Article

Chlorine dioxide inhibits the replication of porcine reproductive and respiratory syndrome virus by blocking viral attachment

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Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) causes a great economic loss to the swine industry globally. Current prevention and treatment measures are not effective to control the outbreak and spread of porcine reproductive and respiratory syndrome (PRRS). In other words, new antiviral strategies are urgently needed. Chlorine dioxide (ClO2) is regarded as a broad-spectrum disinfectant with strong inhibitory effects on microbes and parasites. The purpose of this study was to evaluate the inhibitory effects and underlying molecular mechanisms of ClO2 against PRRSV infection in vitro. Here, we identified ClO2 (the purity is 99%) could inhibit the infection and replication of PRRSV in both Marc-145 cells and porcine alveolar macrophages (PAMs). ClO2 could block PRRSV binding to cells rather than internalization and release, suggesting that ClO2 blocks the first stage of the virus life cycle. We also demonstrated that the inhibition exerted by ClO2 was attributed to the degradation of PRRSV genome and proteins. Moreover, we confirmed that ClO2 could decrease the expression of inflammatory cytokines induced by PRRSV. In summary, ClO2 is an efficient agent and potently suppressed PRRSV infection in vitro.

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... The authors reported that the antiviral effect was due to denaturation of hemagglutinin and neuraminidase glycoproteins, a finding that concurs with previous studies that explain the virucidal mechanism of action of ClO2 due to oxidation of amino acid residues that are key for cell entry [23][24][25]. More recently, the antiviral mechanism of action of ClO2 was investigated in vitro using pig alveolar macrophages and MARC-145 cells exposed to the porcine reproductive and respiratory syndrome virus (PRRSV1), finding that the chemical also inhibits the synthesis of proinflammatory molecules that contribute to the pathogenesis of this disease [26]. The authors concluded that viral synthesis of RNA and proteins was impeded by ClO2, leading to a reduction in viral replication. ...
... Secondly, viral replication efficiency could have decreased due to ClO2-induced biochemical changes in the extra-or intracellular milieu, impeding the synthesis of viral RNA and proteins [26,31]. ...
... If duodenal atrophy and nephropathogenicity in IBV-infected embryos are mitigated by inflammatory responses [37], it is possible that the observed damage is due to ClO2-driven downregulation of acute inflammation that allowed virion replication in the tubular epithelium and in the duodenal villi. This scenario could be plausible if we consider that ClO2-treated pig alveolar macrophages and African green monkey kidney cells infected with the porcine reproductive and respiratory syndrome virus (PRRSV1) downregulate pro-inflammatory cytokines IL-1, IL-6 and TNF-α [26]. There are two drugs, based on chlorite, whose describe mechanism of action might be similar to that elicited by ClO2. ...
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Background The need for safe and effective antiviral treatments is pressing given the number of viral infections that are prevalent in animal and human populations, often causing devastating economic losses and mortality. Informal accounts of anecdotal use of chlorine dioxide (ClO 2 ), a well-known disinfectant and antiseptic, in COVID-19 patients has raised concern about potential toxicity, but also raises the question that ClO 2 might elicit antiviral effects, a possibility that has never been examined in vivo in any animal model. Here, we challenged the hypothesis that ClO 2 decreases the viral load and virus-induced mortality in a vertebrate model. For this, we determined viral load, virus-induced lesions and mortality in 10-day old chick embryos inoculated with 10 ⁴ mean EID 50 /mL of attenuated Massachusetts and Connecticut avian coronavirus (IBV) strains. Results The ClO 2 treatment had a marked impact on IBV infection. Namely, viral titres were 2.4-fold lower and mortality was reduced by half in infected embryos that were treated with ClO 2 . Infection led to developmental abnormalities regardless of treatment. Lesions typical of IBV infections were observed in all inoculated embryos, but severity tended to be significantly lower in ClO 2 -treated embryos. We found no gross or microscopic evidence of toxicity caused by ClO 2 at the doses used herein. Conclusions Our study shows that ClO 2 could be a safe and viable way of treating and mitigating the effects of avian coronavirus infections, and raises the possibility that similar effects could be observed in other organisms. Graphical abstract
... Moreover, ClO 2 , when used as a disinfectant on surfaces, has been reported to exhibit antimicrobial properties against various kinds of microbes efficiently even in wet environments. A concentration of 700-1100 ppm of ClO 2 is also a feasible alternative in replacing glutaraldehyde-based disinfectants [3,4] . Aside from its possibility as a potent disinfectant, ClO 2 has been reported to be a disinfectant without causing side effects due to its rapid action and safe antimicrobial properties [5] . ...
... The potential role of ClO 2 in completely inactivating porcine reproductive and respiratory syndrome virus (PRRSV) was demonstrated through the action of degrading the genome and proteins of the virus [4] . This study also confirmed that the expression of inflammatory cytokines induced by this virus can be reduced by ClO 2 . ...
Article
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Chlorine dioxide plays a significant role in the industrial settings as disinfectants due to its broad antimicrobial property. Despite commonly use as germicide, chlorine dioxide demonstrates a good safety profile, rendering its suitability for use at water treatment and food preparation zones. Protein denaturation including envelope proteins is the major mechanism of chlorine dioxide to inactivate microorganisms even at low concentrations. Adverse reactions are not widely reported due to the typical use at a low concentration. The effectiveness of chlorine dioxide against various microorganisms, in both liquid and gaseous forms, over a wide range of pH and at an extremely low concentration has confirmed chlorine dioxide as a vital and versatile disinfectant.
... 10 Stool samples obligate thus remained used to investigate virus transmission in developed as well as rising markets such as China, the Netherlands, as well as Australia. 11 Just two studies were capable of detecting COVID-19 viral RNA snippets in displayed material of hospitalized individuals as of March 3, 2020, according to the WHO (2020), and the virus's distribution across faucal matter was low ( Figure 1). ...
Article
Presently, the coronavirus (COVID‐19) epidemic presents a major threat to global communal fitness also socio‐financial development. Ignoring worldwide isolation as well as shutdown attempts, the occurrence of COVID‐19 infected patients continues to be extremely large. Nonetheless, COVID‐19’s final course, combined with the prevalence of emerging contaminants (antibiotics, pharmaceuticals, nano‐plastics, pesticides, and so on) in wastewater treatment plants (WWTPs), presents a major problem in wastewater situations. The research, therefore, intends near examine an interdisciplinary as well as technical greet to succor COVID‐19 with subsequent COVID cycles of an epidemic as a framework for wastewater treatment settings. This research investigated the potential for wastewater‐based epidemiology (WBE) to detect SARS‐CoV‐2 also the enzymes happening in wastewater conditions. In addition, a chance for the incorporation into the WWTPs of emerging and robust technologies such as mesmeric nano‐biotechnology, electrochemical oxidation, microscopy, and membrane processes to enhance the overall likelihood of environmental consequences of COVID‐19 also strengthen such quality of water is resolved. This article is protected by copyright. All rights reserved.
... The MARC-145 cells cultured in 6-well plates were prechilled at 4 °C for 30 min, followed by incubation with the PRRSV (MOI = 0.001) and Gel-FeS NPs of different concentrations (0, 85.0, 170.0, 255.0, and 340.0 µg/mL) at 4 °C for 2 h [61]. Finally, the cells were washed three times with pre-cooled DMEM and covered with overlay medium for the corresponding plaque assay. ...
Article
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Background The infection and spread of porcine reproductive and respiratory syndrome virus (PRRSV) pose a serious threat to the global pig industry, and inhibiting the viral infection process is a promising treatment strategy. Nanomaterials can interact with viruses and have attracted much attention due to their large specific surface area and unique physicochemical properties. Ferrous sulfide nanoparticles (FeS NPs) with the characteristics of high reactivity, large specific surface area, and low cost are widely applied to environmental remediation, catalysis, energy storage and medicine. However, there is no report on the application of FeS NPs in the antiviral field. In this study, gelatin stabilized FeS nanoparticles (Gel-FeS NPs) were large-scale synthesized rapidly by the one-pot method of co-precipitation of Fe ²⁺ and S 2‒ . Results The prepared Gel-FeS NPs exhibited good stability and dispersibility with an average diameter of 47.3 nm. Additionally, they were characterized with good biocompatibility and high antiviral activity against PRRSV proliferation in the stages of adsorption, invasion, and replication. Conclusions We reported for the first time the virucidal and antiviral activity of Gel-FeS NPs. The synthesized Gel-FeS NPs exhibited good dispersibility and biocompatibility as well as effective inhibition on PRRSV proliferation. Moreover, the Fe ²⁺ released from degraded Gel-FeS NPs still displayed an antiviral effect, demonstrating the advantage of Gel-FeS NPs as an antiviral nanomaterial compared to other nanomaterials. This work highlighted the antiviral effect of Gel-FeS NPs and provided a new strategy for ferrous-based nanoparticles against PRRSV. Graphical Abstract
... Degradation of viral capsid proteins inhibits the attachment of ClO 2 -exposed bacteriophages to host cells (Ge et al., 2021). Similarly, the ClO 2 -mediated destruction of glycoproteins affects viral attachment to cell receptors and alters the life cycle of porcine reproductive and respiratory syndrome virus (Zhu et al., 2019). In addition, the denaturation of viral proteins has been reported to be involved Frontiers in Plant Science | www.frontiersin.org in the inactivation of human rotavirus (Xue et al., 2013). ...
Article
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Maintaining microbial safety and quality of fresh fruits and vegetables are a global concern. Harmful microbes can contaminate fresh produce at any stage from farm to fork. Microbial contamination can affect the quality and shelf-life of fresh produce, and the consumption of contaminated food can cause foodborne illnesses. Additionally, there has been an increased emphasis on the freshness and appearance of fresh produce by modern consumers. Hence, disinfection methods that not only reduce microbial load but also preserve the quality of fresh produce are required. Chlorine dioxide (ClO2) has emerged as a better alternative to chlorine-based disinfectants. In this review, we discuss the efficacy of gaseous and aqueous ClO2 in inhibiting microbial growth immediately after treatment (short-term effect) versus regulating microbial growth during storage of fresh produce (long-term effect). We further elaborate upon the effects of ClO2 application on retaining or enhancing the quality of fresh produce and discuss the current understanding of the mode of action of ClO2 against microbes affecting fresh produce.
... Under these conditions, ClO 2 is relatively stable and retains its high oxidizing power [5]. ACD can efficiently remove bacteria, fungi, and viruses in the environment [7][8][9][10][11][12]. In contrast, higher concentrations of ClO 2 are harmful to human cells (IC 50 765 ± 18 ppm) [10]. ...
Article
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Chlorine dioxide is a safe, environmentally friendly disinfecting agent. In this study, aqueous chlorine dioxide (ACD) was used to improve the water quality of dental chairs. However, chlorine dioxide is readily released from ACD solutions under open atmosphere conditions. Described herein is a water purification and disinfection system using ACD. The system was designed, fabricated, and integrated into an existing dental chair water system. This system is referred to as an ACD dental chair. Because ClO2 readily degasses from ACD, there needs to be a way to maintain and measure the ACD solution in real time. In our studies, we found that pH and oxidation-reduction potential (ORP) change as a function of chlorine dioxide concentration and are easily controlled and measured. The dosing of the ACD was designed to begin at 800 mV and stop dosing at 810 mV in the ACD dental chair. Through use of this continuous monitoring and automatic dosing system, the water ORP was controlled between 800 and 860 mV. This range is the effective concentration of chlorine dioxide that is without chlorine-like odor and microorganism growth. The ACD dental chair controlled the total bacterial count to <5 CFU/mL and the chlorite concentration was less than 0.0004 mg/L, meeting legal standards of Taiwan, the USA, and China. In addition to the application of ACD in dental chairs, it may also be used in closed water systems for food, cosmetics, beverages, and other industries.
... Immunofluorescence assays (IFAs) and qRT-PCR were used to evaluate the effect of favipiravir on PPRV attachment to Vero cells. Vero cells seeded on coverslips were treated with PPRV and favipiravir and subsequently examined by IFA, as mentioned above (17). Simultaneously, confluent Vero cells were pretreated with favipiravir at 37 • C for 1 h in a six-well plate and then infected with 100 TCID 50 PPRV at 4 • C for 2 h. ...
Article
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Peste des petits ruminants virus (PPRV), belonging to the genus Morbillivirus in the family Paramyxoviridae, causes severe infectious disease in small ruminants and has been rapidly spreading in many parts of Africa, the Middle East, and Asia. Although vaccination is considered to be an effective means of controlling PPR, the heat-sensitive nature of the vaccines against PPRV greatly limits their application in areas with a hot climate. In the present study, we investigated the anti-PPRV effects of favipiravir and sought to identify the underlying mechanisms in vitro using the Vero cell line. MTT assays, Western blotting, indirect immunofluorescence assays, virus plaque formation assays, and qRT-PCR were used to assess the effects of favipiravir on the life cycle of PPRV and the expression of RNA-dependent RNA polymerase (RdRp). Additionally, the expression levels of JAK1, STAT1, phosphorylated (p)-STAT1, PI3K, AKT, and p-AKT, as well as those of signaling molecules acting downstream of the JAK/STAT and PI3K/AKT signaling pathways, were determined by Western blotting and qRT-PCR. The results indicated that, in PPRV-infected, favipiravir-treated Vero cells, the attachment, invasion, replication, and release of PPRV were significantly inhibited, as was the expression of RdRp, when compared with that in untreated PPRV-infected cells. Furthermore, in favipiravir-treated cells, the expression of JAK1 and STAT1 was downregulated, whereas that of p-STAT1 was significantly upregulated. Similarly, the expression levels of PKR, IRF9, ISG54, and MxA proteins that are associated with innate antiviral activity in host cells were also markedly increased. Moreover, with favipiravir treatment, the expression of PI3K and p-AKT and the p-AKT/AKT ratio were significantly decreased, whereas the expression of AKT was noticeably upregulated. The expression of GSK3, NF-κB p65, p-NF-κB p65, and BAD was also increased with favipiravir treatment, while the expression of CREB, p-CREB, p-GSK3, and Bcl-2 was slightly decreased. In addition, all the p-GSK3/GSK3, p-CREB/CREB, p-NF-κB/NF-κB, and p-BAD/BAD ratios were significantly reduced in favipiravir-treated cells. These results implied that the antiviral effectivity of favipiravir against PPRV is mediated by the JAK/STAT and PI3K/AKT pathways and that favipiravir has potential for use as an effective antiviral agent against PPRV.
... The denaturation of virus proteins is also reported to be the dominant inactivation mechanism upon ClO 2 disinfection of human rotavirus and there is no genome damage (Xue et al. 2013). Zhu et al. (2019) suggested that destruction of membrane glycoprotein GP2a and GP4 by ClO 2 blocked the interaction between porcine reproductive and respiratory syndrome virus (PRRSV) and cell receptors, leading to the termination of life cycle of this virus. ...
Article
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Chlorine dioxide (ClO2), an alternative disinfectant to chlorine, has been widely applied in water and wastewater disinfection. This paper aims at presenting an overview of the inactivation kinetics and mechanisms of ClO2 with viruses. The inactivation efficiencies vary greatly among different virus species. The inactivation rates for different serotypes within a family of viruses can differ by over 284%. Generally, to achieve a 4-log removal, the exposure doses, also being referred to as Ct values (mutiplying the concentration of ClO2 and contact time) vary in the range of 0.06–10 mg L−1 min. Inactivation kinetics of viruses show two phases: an initial rapid inactivation phase followed by a tailing phase. Inactivation rates of viruses increase as pH or temperature increases, but show different trends with increasing concentrations of dissolved organic matter (DOM). Both damages in viral proteins and in the 5′ noncoding region within the genome contribute to virus inactivation upon ClO2 disinfection.
... However, the limitation is material compatibility, especially cellulose-based medical materials (McEvoy and Rowan, 2019). Chlorine dioxide also has an antiviral effect (Kingsley et al., 2018;Zhu et al., 2019). Sodium hypochlorite requires a concentration of at least 0.21% to be effective in eliminating coronaviruses (Kampf et al., 2020). ...
Article
The new coronavirus SARS-CoV-2, first identified in Wuhan (China) in December 2019, represents the same family as the Serve Acute Respiratory Syndrome Coronavirus-1 (SARS-CoV-1). These viruses spread mainly via the droplet route. However, during the pandemic of COVID-19 other reservoirs, i.e., water (surface and ground), sewage, garbage, or soil, should be considered. As the infectious SARS-CoV-2 particles are also present in human excretions, such a non-droplet transmission is also possible. A significant problem is the presence of SARS-CoV-2 in the hospital environment, including patients’ rooms, medical equipment, everyday objects and the air. Relevant is selecting the type of equipment in the COVID-19 hospital wards on which the virus particles persist the shortest or do not remain infectious. Elimination of plastic objects/equipment from the environment of the infected person seems to be of great importance. It is particularly relevant in water reservoirs contaminated with raw discharges. Wastewater may contain coronaviruses and therefore there is a need for expanding Water-Based Epidemiology (WBE) studies to use obtained values as tool in determination of the actual percentage of the SARS-CoV-2 infected population in an area. It is of great importance to evaluate the available disinfection methods to control the spread of SARS-CoV-2 in the environment. Exposure of SARS-CoV-2 to 65-70% ethanol, 0.5% hydrogen peroxide, or 0.1% sodium hypochlorite has effectively eliminated the virus from the surfaces. Since there are many unanswered questions about the transmission of SARS-CoV-2, the research on this topic is still ongoing. This review aims to summarize current knowledge on the SARS-CoV-2 transmission and elucidate the viral survival in the environment, with particular emphasis on the possibility of non-droplet transmission.
... The WHO (2020) reported that as of March 3, 2020, only two studies had been able to detect the viral RNA fragments of COVID-19 in the faucal matter of infected patients and that the transmission of the virus through faucal matter was low. In a study, COVID-19 viruses in 10 sampled stools in sewage plants in the Paris area in France were detected [17]. Scientists in the Netherlands also reported on a detected virus RNA in a WWTPs in Amersfoort, a city located 32 miles from southeast of Amsterdam [18]. ...
Article
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The coronavirus (COVID-19) pandemic is currently posing a significant threat to the world’s public health and social-economic growth. Despite the rigorous international lockdown and quarantine efforts, the rate of COVID-19 infectious cases remains exceptionally high. Notwithstanding, the end route of COVID-19, together with emerging contaminants’ (antibiotics, pharmaceuticals, nanoplastics, pesticide, etc.) occurrence in wastewater treatment plants (WWTPs), poses a great challenge in wastewater settings. Therefore, this paper seeks to review an inter-disciplinary and technological approach as a roadmap for the water and wastewater settings to help fight COVID-19 and future waves of pandemics. This study explored wastewater–based epidemiology (WBE) potential for detecting SARS-CoV-2 and its metabolites in wastewater settings. Furthermore, the prospects of integrating innovative and robust technologies such as magnetic nanotechnology, advanced oxidation process, biosensors, and membrane bioreactors into the WWTPs to augment the risk of COVID-19’s environmental impacts and improve water quality are discussed. In terms of the diagnostics of COVID-19, potential biosensors such as sample–answer chip-, paper- and nanomaterials-based biosensors are highlighted. In conclusion, sewage treatment systems, together with magnetic biosensor diagnostics and WBE, could be a possible way to keep a surveillance on the outbreak of COVID-19 in communities around the globe, thereby identifying hotspots and curbing the diagnostic costs of testing. Photocatalysis prospects are high to inactivate coronavirus, and therefore a focus on safe nanotechnology and bioengineering should be encouraged.
... The inhibition mechanism of ClO 2 is unclear, but the action of ClO 2 is only known as inhibition. For porcine reproductive and respiratory syndrome virus (PRRSV), ClO 2 could inhibit the first stage of viral life, which inhibited binding itself to cells where PRRSV was not internalized and released (Zhu et al., 2019). ...
Article
The high resolution spectrum of the ν1+ν3 band of the 35ClO2 free radical was recorded with a Bruker IFS 125HR Fourier transform infrared spectrometer and theoretically analysed with an improved theoretical basis including the reduced effective spin–rotation Hamiltonian (which takes into account sixth order operators describing spin–rotational interactions) and a newly created computer code ROVDES for the ro–vibrational spectra of open–shell free radicals. About 2600 spin–ro–vibrational transitions with the values Nmax=59 and Kamax=17 (being about 2.4 times higher in comparison with the number of assigned transitions known in the literature) were assigned to the ν1+ν3 band of 35ClO2 and 1049 spin–ro–vibrational energies (produced only from unblended non–saturated and not very weak experimental lines) of the (101) upper vibrational state were obtained. A set of 30 varied parameters of the effective spin–rotation–vibration Hamiltonian of the (101) vibrational state (vibrational energy, 17 rotational and centrifugal distortion parameters and 12 are spin–rotational ones) was determined from the weighted fit of parameters of the effective spin–rotational Hamiltonian in A-reduction and Ir-representation. The obtained set of parameters reproduces the initial 1049 ”experimental“ upper state energies with the drms=2.5×10-4 cm⁻¹ which is close to the experimental uncertainty of the recorded spectra and is almost 70 times higher in comparison with the analogous reproduction of the same initial upper energies with the use of parameters from (J.Mol.Spectrosc.,158,347-356(1993)).
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Porcine reproductive and respiratory syndrome (PRRS), a viral infection caused by PRRS virus (PRRSV) can result in in severe reproductive failure, and respiratory disease in the pigs thus causing enormous economic losses to the global swine industry. Although the cellular receptors for PRRSV have been identified, but mechanisms underlying PPRSV replication remain obscure. Here, we have performed a genome-scale CRISPR/Cas9 knockout screen in the pig kidney cells with PRRSV. Several genes were found to be highly enriched post-PRRSV selection, just like KxDL Motif Containing 1(KXD1), Proteasome 26S Subunit, Non-ATPase 3 (PSMD3) and Galectin 2 (LGALS2) and soon on. Importantly, we have identified that loss of KXD1 resulted in the restricted autophagy and inhibited replication of PRRSV. Therefore, our study demonstrates that CRISPR/Cas9 system can be effectively used for the screening of pig factors responsible for PRRSV replication.
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African swine fever (ASF) is a highly contagious disease and provokes severe economic losses and health threats. At present no effective vaccine or treatment is available to prevent or cure ASF. Consequently, there is an urgent need to develop effective drugs against ASF virus (ASFV). Chlorine dioxide (ClO2), an ideal biocide, has broad-spectrum antibacterial activity and no drug resistance. Here, we found that ClO2 strongly inhibited ASFV replication in porcine alveolar macrophages (PAMs). The inhibitory effect of ClO2 occurred during viral attachment rather than entry, indicating that ClO2 suppressed the early stage of virus life cycle. ClO2 showed a potent anti-ASFV effect when added either before, simultaneously with, or after virus infection. Furthermore, ClO2 could destroy viral nucleic acids and proteins, which may contribute to its capacity of inactivating ASFV virions. The minimum concentration of degradation of ASFV nucleic acids by ClO2 is 1.2 μg/mL, and the degradation is a temperature-dependent manner. These have guiding significance for ClO2 prevention and control of ASFV infection in pig farms. In addition, ClO2 decreased the expression of ASFV-induced inflammatory cytokines. Overall, our findings suggest that ClO2 may be an ideal candidate for the development of novel anti-ASFV prophylactic and therapeutic drugs in swine industry.
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Fresh fruits and vegetables carry a heavy load of microorganisms which may cause the risks of food‐borne illness to the consumer. Even after washing with water, there is a need for sanitization and disinfection to drop down a load of harmful microbes under the safe limit. Sanitizers and disinfectants are not only cost‐effective but also non‐hazardous and eco‐friendly. Moreover, they should not hamper the organoleptic and nutritional properties of fresh produce. With rising demand for safe, nutritious, and fresh fruits and vegetables, many new disinfectants and treatments are commercially available. During this COVID‐19 outbreak, knowledge of sanitizers and disinfectants for fresh fruits and vegetables is very important. This review focuses on working principles, applications, and related legislation of physical and chemical disinfection technologies (chlorine, chlorine dioxide, ozone, organic acids, electrolyzed water, irradiation, ultrasound etc.) and their effectiveness for shelf‐life extension of fresh produce.
Chapter
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This article lists the changes to virus taxonomy approved and ratified by the International Committee on Taxonomy of Viruses in February 2018. A total of 451 species, 69 genera, 11 subfamilies, 9 families and one new order were added to the taxonomy. The current totals at each taxonomic level now stand at 9 orders, 131 families, 46 subfamilies, 803 genera and 4853 species. A change was made to the International Code of Virus Classification and Nomenclature to allow the use of the names of people in taxon names under appropriate circumstances. An updated Master Species List incorporating the approved changes was released in March 2018 (https://talk.ictvonline.org/taxonomy/).
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Porcine reproductive and respiratory syndrome virus (PRRSV) has been epidemic more than 30 years in America and 20 years in China. It is still one of the most important causative agents to the worldwide swine industry. Here, we systematically analyzed the prevalence status of PRRSV in China by a molecular epidemiological perspective. Now both PRRSV-1 and PRRSV-2 are circulating and approximately more than 80% of pig farms are seropositive for PRRSV. For PRRSV-2, there are four lineages (lineage 1, lineage 3, lineage 5, lineage 8) circulating in the fields. Lineage 8 (CH-1a-like) and lineage 5 (BJ-4-like) appeared almost at the same time during 1995-1996. Notably, BJ-4 shares 99.6% and 99.8% identity with VR2332 and RespPRRS MLV, respectively. It means that lineage 5 is likely to be imported from America. Now highly pathogenic PRRSV (HP-PRRSV) which was considered to be evolved from local diversity of lineage 8 strains is predominant with different variants. Lineage 3 appeared in 2010 which is mainly sporadic in south of China. Lineage 1, also known as NADC30-like strains in China, has been prevalent since 2013 and leads to PRRS pandemic again. For PRRSV-1, although sporadic at present, more than 9 provinces/regions have been reported. All the circulating strains belong to subtype I. It should be paid more attention since there are no vaccines available. Our analysis would help to deeply understand the prevalent status of PRRSV in China and provide useful information for prevention and control of porcine reproductive and respiratory syndrome (PRRS).
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Background Porcine reproductive and respiratory syndrome virus (PRRSV) could lead to pandemic diseases and huge financial losses to the swine industry worldwide. Curcumin, a natural compound, has been reported to serve as an entry inhibitor of hepatitis C virus, chikungunya virus and vesicular stomatitis virus. In this study, we investigated the potential effect of curcumin on early stages of PRRSV infection. Results Curcumin inhibited infection of Marc-145 cells and porcine alveolar macrophages (PAMs) by four different genotype 2 PRRSV strains, but had no effect on the levels of major PRRSV receptor proteins on Marc-145 cells and PAMs or on PRRSV binding to Marc-145 cells. However, curcumin did block two steps of the PRRSV infection process: virus internalization and virus-mediated cell fusion. Conclusions Our results suggested that an inhibition of genotype 2 PRRSV infection by curcumin is virus strain-independent, and mainly inhibited by virus internalization and cell fusion mediated by virus. Collectively, these results demonstrate that curcumin holds promise as a new anti-PRRSV drug.
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Human norovirus (NoV) is the leading cause of foodborne illnesses in the United States. Norovirus is shed in high numbers in the feces and vomitous of infected individuals. Contact surfaces contaminated with bodily fluids harboring infectious virus particles serve as vehicles for pathogen transmission. Environmental stability of NoV and its resistance to many conventional disinfectants necessitate effective inactivation strategies to control the spread of virus. We investigated the efficacy of two commercial disinfectants, hydrogen peroxide (7.5%) and a chlorine dioxide (0.2%)-surfactant-based product using a fogging delivery system against human NoV GI.6 and GII.4 Sydney strains as well as the cultivable surrogate, feline calicivirus (FCV) dried on stainless steel coupons. Log10 reductions in human NoV and FCV were calculated utilizing RNase RT-qPCR and infectivity (plaque) assay, respectively. An improved antiviral activity of hydrogen peroxide as a function of disinfectant formulation concentration in the atmosphere was observed against both GII.4 and FCV. At 12.4 ml/m³, hydrogen peroxide achieved a respective 2.5 ± 0.1 and 2.7 ± 0.3 log10 reduction in GI.6 and GII.4 NoV genome copies, and a 4.3 ± 0.1 log10 reduction in infectious FCV within 5 min. At the same disinfectant formulation concentration, chlorine dioxide-surfactant-based product resulted in a respective 1.7 ± 0.2, 0.6 ± 0.0, and 2.4 ± 0.2 log10 reduction in GI.6, GII.4, and FCV within 10 min; however, increasing the disinfectant formulation concentration to 15.9 ml/m3 negatively impacted its efficacy. Fogging uniformly delivered the disinfectants throughout the room, and effectively decontaminated viruses on hard-to-reach surfaces. Hydrogen peroxide delivered by fog showed promising virucidal activity against FCV by meeting the United States EPA 4-log10 reduction criteria for an anti-noroviral disinfectant; however, fogged chlorine dioxide-surfactant-based product did not achieve a 4-log10 inactivation. Future investigation aimed at optimizing decontamination practices is warranted.
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Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most economically important viral pathogen currently affecting swine production worldwide. Although PRRS vaccines have been commercially available for over 20 years, the available vaccines are considered inadequately effective for control and eradication of the virus. Major obstacles for the development of a highly effective PRRS vaccine include the highly variable nature of the viral genome, the viral ability to subvert the host immune system, and the incomplete understanding of the immune protection against PRRSV infection. This article summarizes the impediments for the development of a highly protective PRRS vaccine and reviews the vaccinology approaches that have been attempted to overcome one of the most formidable challenges, which is the substantial genetic variation among PRRSV isolates, to broaden the antigenic coverage of PRRS vaccines.
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Porcine reproductive and respiratory syndrome virus (PRRSV) has a restricted cell tropism and prefers to invade well-differentiated cells of the monocyte/macrophage lineage, such as pulmonary alveolar macrophages and African green monkey kidney cell line MA-104 and its derivatives, such as Marc-145, Vero and CL-2621. PRRSV infection of the host cells actually is a receptor-mediated endocytosis and replication process. The presence and absence of the cellular receptors decide whether the cell lines are permissive or non-permissive to PRRSV infection. Several PRRSV non-permissive cell lines, such as BHK-21, PK-15 and CHO-K1, have been shown to become sensitive to the virus infection upon expression of the recombinant receptor proteins. Up to now, heparin sulfate, sialoadhesin, CD163, CD151 and vimentin have been identified as the important PRRSV receptors via their involvement in virus attachment, internalization or uncoating. Each receptor is characterized by the distribution in different cells, the function in virus different infection stages and the interaction model with the viral proteins or genes. Joint forces of the receptors recently attract attentions due to the specific function. PRRSV receptors have become the targets for designing the new anti-viral reagents or the recombinant cell lines used for isolating the viruses or developing more effective vaccines due to their more conserved sequences compared with the genetic variation of the virus. In this paper, the role of PRRSV receptors and the molecular mechanism of the interaction between the virus and the receptors are reviewed.
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Here we report the rescue of a recombinant porcine reproductive and respiratory syndrome virus (PRRSV) carrying an enhanced green fluorescent protein (EGFP) reporter gene as a separate transcription unit. A copy of the transcription regulatory sequence for ORF6 (TRS6) was inserted between the N protein and 3[prime]-UTR to drive the transcription of the EGFP gene and yield a general purpose expression vector. Successful recovery of PRRSV was obtained using an RNA polymerase II promoter to drive transcription of the full-length virus genome, which was assembled in a bacterial artificial chromosome (BAC). The recombinant virus showed growth replication characteristics similar to those of the wild-type virus in the infected cells. In addition, the recombinant virus stably expressed EGFP for at least 10 passages. EGFP expression was detected at approximately 10 h post infection by live-cell imaging to follow the virus spread in real time and the infection of neighbouring cells occurred predominantly through cell-to-cell-contact. Finally, the recombinant virus generated was found to be an excellent tool for neutralising antibodies and antiviral compound screening. The newly established reverse genetics system for PRRSV could be a useful tool not only to monitor virus spread and screen for neutralising antibodies and antiviral compounds, but also for fundamental research on the biology of the virus.
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Vaccination is the principal means used to control and treat porcine reproductive and respiratory syndrome virus (PRRSV) infection. An array of PRRS vaccine products is available in various regions of the world. However, despite extensive efforts, little progress has been made to improve efficacy since the first introduction of a live, attenuated vaccine in 1994 in the USA. Key limitations include: (a) uncertainty about the viral targets of protective immunity that prevents a research focus on individual viral structures and proteins, and frustrates efforts to design novel vaccines; (b) inability to establish clear immunological correlates of protection that requires laborious in vivo challenge models for evaluation of protection against challenge; and (c) the great genetic diversity of PRRSV which requires that challenge experiments be interpreted cautiously since it is not possible to predict how immunological protection against one isolate will translate to broadly cross-protective immunity. Economically significant levels of cross-protection that are provided to a variety of field isolates still cannot assure that effective protection will be conferred to isolates that might emerge in the future. In addition to these substantial barriers to new PRRSV vaccine development, there are enormous gaps in our understanding of porcine immunological mechanisms and processes that provide immunity to PRRSV infection and memory responses for long-term protection. Despite these impediments, we should be confident that progress will be made. Sequencing of the swine genome is providing a rich source of primary knowledge of gene structure and transcriptional regulation that is certain to reveal important insights about the mechanisms of anti-PRRSV immunity, and continued efforts to unravel the details of the interaction of PRRSV with pigs will lead to new insights that overcome the current limitations in the field.
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Porcine reproductive and respiratory syndrome virus (PRRSV) is an enveloped, positive-sense single-stranded RNA virus belonging to the Arteriviridae family. Arteriviruses and coronaviruses are grouped together in the order Nidovirales, based on similarities in genome organization and expression strategy. Over the past decade, crystal structures of several viral proteins, electron microscopic studies of the virion, as well as biochemical and in vivo studies on protein-protein interactions have led to a greatly increased understanding of PRRSV structural biology. At this point, crystal structures are available for the viral proteases NSP1α, NSP1β and NSP4 and the nucleocapsid protein, N. The NSP1α and NSP1β structures have revealed additional non-protease domains that may be involved in modulation of host functions. The N protein forms a dimer with a novel fold so far only seen in PRRSV and other nidoviruses. Cryo-electron tomographic studies have shown the three-dimensional organization of the PRRSV virion and suggest that the viral nucleocapsid has an asymmetric, linear arrangement, rather than the isometric core previously described. Together, these studies have revealed a closer structural relationship between arteri- and coronaviruses than previously anticipated.
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A collection of 12 monoclonal antibodies (MAbs) raised against porcine reproductive and respiratory syndrome (PRRS) virus was used to study the antigenic structure of the virus nucleocapsid protein (N). The full-length N gene, encoded by open reading frame 7, was cloned from the Canadian PRRS virus, PA-8. Deletions were introduced into the N gene to produce a series of nine overlapping protein fragments ranging in length from 25 to 112 amino acids. The individual truncated genes were cloned as glutathione S-transferase fusions into a eukaryotic expression vector downstream of the T7 RNA polymerase promoter. HeLa cells infected with recombinant vaccinia virus expressing T7 RNA polymerase were transfected with plasmid DNA encoding the N protein fragments, and the antigenicity of the synthesized proteins was analyzed by immunoprecipitation. Based on the immunoreactivities of the N protein deletion mutants with the panel of N-specific MAbs, five domains of antigenic importance were identified. MAbs SDOW17, SR30, and 5H2.3B12.1C9 each identified independent domains defined by amino acids 30 to 52, 69 to 123, and 37 to 52, respectively. Seven of the MAbs tested specifically recognized the local protein conformation formed in part by the amino acid residues 52 to 69. Furthermore, deletion of 11 amino acids from the carboxy terminus of the nucleocapsid protein disrupted the epitope configuration recognized by all of the conformation-dependent MAbs, suggesting that the carboxy-terminal region plays an important role in maintaining local protein conformation.
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Induction of the proinflammatory cytokines interleukin-1 (IL-1) (alpha and beta), IL-6, IL-8, IL-10, IL-12, and tumor necrosis factor alpha (TNF-alpha) in pulmonary alveolar macrophages (PAMs) was assessed following experimental infection with porcine reproductive and respiratory syndrome virus (PRRSV) and/or Mycoplasma hyopneumoniae by using in vivo and in vitro models. The in vivo model consisted of pigs infected with PRRSV and/or M. hyopneumoniae and necropsied at 10, 28, or 42 days postinfection. Pigs infected with both pathogens had a greater percentage of macroscopic lung lesions, increased clinical disease, and slower viral clearance than pigs infected with either pathogen alone. The pigs infected with both PRRSV and M. hyopneumoniae had significantly increased levels of mRNA for many proinflammatory cytokines in PAMs collected by bronchoalveolar lavage (BAL) at all necropsy dates compared to those in uninfected control pigs. Increased levels of IL-1beta, IL-8, IL-10, and TNF-alpha proteins in BAL fluid, as measured by enzyme-linked immunosorbent assay, confirmed the increased cytokine induction induced by the pathogens. An in vitro model consisted of M. hyopneumoniae-inoculated tracheal ring explants cultured with PRRSV-infected PAMs. PAMs were harvested at 6 or 15 h postinfection with either or both pathogens. The in vitro study detected increased IL-10 and IL-12 mRNA levels in PAMs infected with PRRSV at all time periods. In addition, IL-10 protein levels were significantly elevated in the culture supernatants in the presence of M. hyopneumoniae-inoculated tracheal ring explants. The increased production of proinflammatory cytokines in vivo and in vitro associated with concurrent M. hyopneumoniae and PRRSV infection may play a role in the increased rates of pneumonia associated with PRRSV infection. The increased levels of IL-10 may be a possible mechanism that PRRSV and M. hyopneumoniae use to exacerbate the severity and duration of pneumonia induced by PRRSV and modulate the respiratory immune response.
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To estimate the annual cost of infections attributable to porcine reproductive and respiratory syndrome (PRRS) virus to US swine producers. Economic analysis. Data on the health and productivity of PRRS-affected and PRRS-unaffected breeding herds and growing-pig populations were collected from a convenience sample of swine farms in the midwestern United States. Health and productivity variables of PRRS-affected and PRRS-unaffected swine farms were analyzed to estimate the impact of PRRS on specific farms. National estimates of PRRS incidence were then used to determine the annual economic impact of PRRS on US swine producers. PRRS affected breeding herds and growing-pig populations as measured by a decrease in reproductive health, an increase in deaths, and reductions in the rate and efficiency of growth. Total annual economic impact of these effects on US swine producers was estimated at dollar 66.75 million in breeding herds and dollar 493.57 million in growing-pig populations. PRRS imposes a substantial financial burden on US swine producers and causes approximately dollar 560.32 million in losses each year. By comparison, prior to eradication, annual losses attributable to classical swine fever (hog cholera) and pseudorabies were estimated at dollar 364.09 million and dollar 36.27 million, respectively (adjusted on the basis of year 2004 dollars). Current PRRS control strategies are not predictably successful; thus, PRRS-associated losses will continue into the future. Research to improve our understanding of ecologic and epidemiologic characteristics of the PRRS virus and technologic advances (vaccines and diagnostic tests) to prevent clinical effects are warranted.
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Waterborne viruses can exhibit resistance to common water disinfectants, yet the mechanisms that allow them to tolerate disinfection are poorly understood. Here, we generated echovirus 11 (E11) with resistance to chlorine dioxide (ClO2) by experimental evolution, and we assessed the associated genotypic and phenotypic traits. ClO2 resistance emerged after E11 populations were repeatedly reduced (either by ClO2-exposure or by dilution) and then regrown in cell culture. The resistance was linked to an improved capacity of E11 to bind to its host cells, which was further attributed to two potential causes: first, the resistant E11 populations possessed mutations that caused amino acid substitutions from ClO2-labile to ClO2-stable residues in the viral proteins, which likely increased the chemical stability of the capsid toward ClO2. Second, resistant E11 mutants exhibited the capacity to utilize alternative cell receptors for host binding. Interestingly, the emergence of ClO2 resistance resulted in an enhanced replicative fitness compared to the less resistant starting population. Overall this study contributes to a better understanding of the mechanism underlying disinfection resistance in waterborne viruses, and processes that drive resistance development.
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PRRSV (porcine reproductive and respiratory syndrome virus) is a major economically significant pathogen that has adversely impacted the global swine industry for almost 30 years. Currently PRRSV is estimated to cause losses of almost US$600 million per year in the USA. Except for new mutants that continually emerge during PRRSV outbreaks, our understanding of the virology, origin, and evolution of PRRSV and the host's immune response are largely inadequate. Such limited knowledge impedes development of effective methods to eradicate this virus. In this review, we systematically describe recent advances in anti-PRRSV research, especially focusing on those techniques with the potential to transform current anti-PRRSV strategies. Furthermore, a combination of these new techniques may provide creative insights to guide future PRRSV control and prevention.
Article
Porcine reproductive and respiratory syndrome (PRRS) is one of the most important diseases in pigs, leading to significant economic losses in swine industry worldwide. PRRS virus (PRRSV) is an enveloped positive single-stranded RNA virus, which mainly infects cells of monocyte/macrophage lineage. MicroRNAs (miRNAs) are small non-coding RNAs and have emerged as important regulators of virus–host cell interactions. In the past several years, scientists have been trying to understand the interaction between host miRNAs and PRRSV infection. Here, we focus on discussing the current understanding roles of host miRNAs in PRRSV infection and propose that miRNAs may be an effective executant in controlling PRRSV infection.
Article
Porcine reproductive and respiratory syndrome virus (PRRSV) is endemic in most pig producing countries worldwide and causes enormous economic losses to the swine industry. Specifically differentiated porcine alveolar macrophages are the primary target for PRRSV infection in pigs. At least six cellular molecules have been described so far as putative receptors for PRRSV, and they include heparan sulfate, vimentin, CD151, sialoadhesin (CD169; siglec-1), dendritic cell-specific intercellular adhesion melecule-3-grabbing non-integrin (DC-SIGN; CD209), and CD163 (SRCR, cysteine-rich scavenger receptor). Progress has been made to shed light on the interactions between cells and PRRSV, and this review describes the advances and current understanding of the entry of PRRSV to cells with a particular focus on the role of CD163 and sialoadhesin for infection and PRRSV pathogenesis. CD163 is most likely the primary and core receptor for PRRSV and determines the susceptibility of cells to the virus. Sialoadhesin is either unnecessary for infection or may function as an accessory protein. Sialoadhesin has been mostly studied for genotype I PRRSV whereas the utilization of CD163 has been mostly studied using genotype II PRRSV, and whether each genotype indeed utilizes a different receptor is unclear. Copyright © 2015 Elsevier B.V. All rights reserved.
Article
Lithium chloride (LiCl) has been used as a mood stabilizer in the manic depressive disorders treatment. Recent studies show that LiCl is also a potent inhibitor for some DNA and RNA viruses. Porcine reproductive and respiratory syndrome virus (PRRSV) is an important viral pathogen in modern pig industry. In this study, we assessed the inhibitory effect of LiCl on PRRSV infection using plaque-formation assay, Q-PCR and Western blot analysis. Our results showed that LiCl could inhibit PRRSV infection in MARC-145 and PAM-CD163 cells. Previous reports have shown that LiCl could induce the Wnt pathway in the absence of Wnt ligands. In our studies, we demonstrated that LiCl activates the Wnt pathway in PRRSV infected cells. Additionally, the knockdown of β -catenin or the Wnt/ β -catenin pathway inhibitor PNU74654 was able to reverse the antiviral effect of LiCl, which suggested that the inhibitory effect of LiCl against PRRSV replication might be associated with the activation of the Wnt/ β -catenin pathway. We also found that lower viral replication after LiCl treatment was associated with the reduced mRNA levels of pro-inflammatory IL-8, IL-6, IL-1 β, tumor necrosis factor α and decreased NF-kB nuclear translocation. Collectively, our data demonstrated that LiCl inhibited PRRSV infection by enhancing Wnt/ β -catenin pathway and suppressing pro-inflammatory responses. Copyright © 2015. Published by Elsevier B.V.
Article
The porcine reproductive and respiratory syndrome virus (PRRSV) pp1a and pp1ab replicase polyproteins are proteolytically processed by four proteases encoded in ORF1a. In this study, a large set of PRRSV replicase cleavage products were identified and pp1a cleavage sites were verified by using a combination of bioinformatics, proteomics, immunoprecipitation, and site-directed mutagenesis. For genotype 1 PRRSV (isolate SD01-08), proteomic analysis identified H180/S181, G385/A386, and G1446/A1447 as the cleavage sites separating nsp1α/1β, nsp1β/nsp2, and nsp2/nsp3, respectively. Transient expression of nsp2-8, nsp3-8, nsp4-8, nsp5-8 (using the recombinant vaccinia virus/T7 RNA polymerase system) and immunoprecipitation identified the cleavage end products nsp2, nsp3, nsp4, nsp7α and nsp7β, and various processing intermediates. Our studies also revealed the existence of alternative proteolytic processing pathways for the processing of the nsp3-8 region, depending on the presence or absence of nsp2 as a co-factor. The identity of most cleavage products was further corroborated by site-directed mutagenesis of individual cleavage sites in constructs expressing nsp3-8 or nsp4-8. This study constitutes the first in-depth experimental analysis of PRRSV replicase processing and the data are discussed against the background of the processing scheme previously derived for the arterivirus prototype, the distantly related equine arteritis virus (EAV). Despite several differences between the two viruses, of which the functional significance remains to be studied, our study demonstrates the general conservation of the replicase pp1a processing scheme between EAV and PRRSV, and likely also the other members of the arterivirus family. Copyright © 2014 Elsevier B.V. All rights reserved.
Article
Porcine reproductive and respiratory syndrome virus (PRRSV), an arterivirus that causes significant losses in the pig industry, is one of the most important animal pathogens of global significance. Since the discovery of the virus, significant progress has been made in understanding its epidemiology and transmission, but no adequate control measures are yet available to eliminate infection with this pathogen. The genome replication of PRRSV is required to reproduce, within a few hours of infection, the millions of progeny virions that establish, disseminate, and maintain infection. Replication of the viral RNA genome is a multistep process involving a replication complex that is formed not only from components of viral and cellular origin but also from the viral genomic RNA template; this replication complex is embedded within particular virus-induced membrane vesicles. PRRSV RNA replication is directed by at least 14 replicase proteins that have both common enzymatic activities, including viral RNA polymerase, and also unusual and poorly understood RNA-processing functions. In this review, we summarize our current understanding of PRRSV replication, which is important for developing a successful strategy for the prevention and control of this pathogen.
Article
This study investigates the mechanisms underlying the deviation from Chick-Watson kinetics, namely a tailing curve, during the disinfection of viruses by chlorine dioxide (ClO2). Tailing has been previously reported, but is typically attributed to the decay in disinfectant concentration. Herein, it is shown that tailing occurs even at constant ClO2 concentrations. Four working hypothesis to explain the cause of tailing were tested, specifically changes in the solution's disinfecting capacity, aggregation of viruses, resistant virus subpopulations, and changes in the virus properties during disinfection. In experiments using MS2 as a model virus, it was possible to rule out the solution's disinfecting capacity, virus aggregation and the resistant subpopulation as reasons for tailing. Instead, the cause for tailing is the deposition of an adduct onto the virus capsid over the course of the experiment, which protects the viruses. This adduct could easily be removed by washing, which restored the susceptibility of the viruses to ClO2. This finding highlights an important shortcoming of ClO2, namely its self-limiting effect on virus disinfection. It is important to take this effect into account in treatment applications to ensure that the water is sufficiently disinfected before human consumption.
Article
Porcine reproductive and respiratory syndrome virus (PRRSV) represents a significant challenge to the swine industry worldwide. Current control strategies against PRRSV are still inadequate and there is an urgent need for new antiviral therapies. Flavaspidic acid AB (FA-AB) is a compound derived from Dryopteris crassirhizoma, a traditional antiviral Chinese medicine. Here, we first identified its anti-PRRSV activity through targeting multiple stages in PRRSV infection in vitro. Our studies demonstrated that FA-AB could inhibit the internalization and cell-to-cell spreading of PRRSV, but not block PRRSV binding to cells. By monitoring the kinetics of PRRSV replication, we showed that FA-AB significantly suppressed PRRSV replication when treatment was initiated 24 hours after virus infection. Furthermore, we confirmed that FA-AB was able to significantly induce IFN-α, IFN-β, and IL1-β expression in porcine alveolar macrophages, suggesting that induction of antiviral cytokines by FA-AB could contribute to FA-AB induced inhibition of PRRSV replication. In conclusion, we provide a foundation for the possibility to develop a new therapeutic agent to control PRRSV infection.
Article
Antibiotic resistance genes (ARGs), in association with antibiotic resistant bacteria (ARB), have been identified as widespread contaminants of treated drinking waters and wastewaters. As a consequence, concerns have been raised that ARB or ARG transport between aquatic compartments may enhance the spread of antibiotic resistance amongst non-resistant bacterial communities by means of horizontal gene transfer processes. Most often, discussion of horizontal gene transfer focuses on the probable role of conjugative plasmid or transposon exchange, which requires live ARB donor cells. Conventional water and wastewater disinfection processes generally provide highly effective means for mitigating the transport of live ARB; thereby minimizing risks of conjugative gene transfer. However, even if ARB present in a treated water are fully inactivated during a disinfection process, the possibility remains that intact remnants of DNA contained within the resulting cell debris could still confer resistance genotypes to downstream bacterial populations by means of natural transformation and/or transduction, which do not require live donor cells. Thus, a systematic evaluation of the capability of common disinfection technologies to ensure the destruction of bacterial DNA, in addition to pathogen inactivation, seems warranted. With that objective in mind, this review seeks to provide a concise introduction to the significance of ARB and ARG occurrence in environmental systems, coupled with a review of the role that commonly used water and wastewater disinfection processes may play in minimizing ARG transport and dissemination.
Article
Porcine reproductive and respiratory syndrome virus (PRRSV) has a restricted tropism mainly for porcine alveolar macrophages (PAMs), but not for peripheral blood monocytes (BMo) in vivo. Previous research showed that only a few BMo became susceptible to PRRSV infection after 1 day culture. Porcine sialoadhesin (PoSn) and CD163 are identified to be the two main PRRSV receptors for binding and internalization. Both receptors are not expressed on BMo, or only expressed at low levels, which may explain why PRRSV cannot infect them. The relationship of BMo differentiation/aging, PRRSV receptor level, and susceptibility to PRRS virus infection has not been thoroughly investigated. In this study, BMo were successfully cultured with pig serum plus L929 cell culture supernatant. Our results showed that both the mRNA and protein expression levels of PoSn were significantly increased after 5-day culture. The mRNA level of CD163 was enhanced more than 20-fold after 1-day culture; CD163-positive BMo increased dramatically from about 2% after 2h- culture to about 50% after 96-h culture. Furthermore, cultured BMo became much more permissive to PRRSV infection, and the percentage of PRRSV-infected BMo was at least the same as PAMs, if not higher, when infected with CH-1a, the first PRRSV strain isolated in China, or HV, a highly virulent strain. Three other PRRSV strains including VR2332, and two classical Chinese isolates could also infect cultured BMo as well. Most importantly, PRRS virus was successfully isolated from 14 of 15 antibody-positive serum samples using cultured BMo. These results suggest that the enhanced susceptibility of cultured BMo to PRRS virus is coordinated with increased CD163 expression, but less related to the delayed (day 5) increased expression of PoSn. Thus, cultured BMo could be an alternative choice for PRRS virus isolation and identification.
Article
Recognized in the late 1980s in North America and Europe the syndrome that caused reproductive and respiratory problems in swine was initially called "mystery swine disease" and is now termed "porcine reproductive and respiratory syndrome (PRRS)". In the early 1990 s an arterivirus, referred to as PRRS virus (PRRSV), was determined to be the etiologic agent of this disease. Since then research has progressed substantially. Most recently "porcine high fever disease" was reported in China starting in 2006 with PRRSV being a critical virus associated with high morbidity and mortality (20%) associated with this syndrome which in 2010 is still causing severe pathology in pigs in China, with spread to Vietnam and Cambodia. This volume contains a series of reviews that highlight the virus, its pathogenesis, epidemiology, immunology, vaccinology and host genetic control. This paper provides a brief historical review of PRRS and the associated PRRSV. It presents areas of research gaps that inhibit current progress towards PRRS elimination through production of effective vaccines and current plans for PRRS elimination or eradication programs. It is hoped that this discussion will stimulate further collaboration between researchers and swine veterinarians throughout the world to provide answers that enhance our understanding of PRRS and PRRSV in an effort to eliminate this economically important disease.
Article
Porcine reproductive and respiratory syndrome (PRRS) virus appeared 20 years ago as the cause of a new disease in swine. Today PRRS is the most significant swine disease worldwide in spite of intensive immunological interventions. The virus showed remarkable genetic variation with two geographically distinct genotypes at the time of its discovery, indicating the possibility of prolonged evolutionary divergence prior to its appearance as a swine pathogen. Since then, both type 1 and type 2 have spread geographically, radiated genetically, and acquired new phenotypic characteristics, especially increased virulence. Here, we explore various hypotheses that might account for rapid expansion and diversification of PRRSV, including mechanisms specific to PRRSV and other arteriviruses, cellular modification processes, and immunological selection. Phylogenetic analysis of PRRSV has provided a broadly applicable means to relate diverse isolates, but it does not explain biological variation in virulence or immunological cross-protection. We present other methods of classification and review their limitations. Major questions about PRRSV remain unanswered despite intensive investigation, suggesting that the interaction of PRRSV with pigs involves novel biological processes that may be relevant to other RNA virus and host interactions.
Article
Our knowledge about the structure and function of the nonstructural proteins (nsps) encoded by the arterivirus replicase gene has advanced in recent years. The continued characterization of the nsps of the arterivirus prototype equine arteritis virus has not only corroborated several important functional predictions, but also revealed various novel features of arteriviral replication. For porcine reproductive and respiratory syndrome virus (PRRSV), based on bioinformatics predictions and experimental studies, a processing map for the pp1a and pp1ab replicase polyproteins has been developed. Crystal structures have been resolved for two of the PRRSV nonstructural proteins that possess proteinase activity (nsp1α and nsp4). The functional characterization of the key enzymes for arterivirus RNA synthesis, the nsp9 RNA polymerase and nsp10 helicase, has been initiated. In addition, progress has been made on nsp functions relating to the regulation of subgenomic mRNAs synthesis (nsp1), the induction of replication-associated membrane rearrangements (nsp2 and nsp3), and an intriguing replicative endoribonuclease (nsp11) for which the natural substrate remains to be identified. The role of nsps in viral pathogenesis and host immunity is also being explored, and specific nsps (including nsp1α/β, nsp2, nsp4, nsp7, and nsp11) have been implicated in the modulation of host immune responses to PRRSV infection. The nsp3-8 region was identified as containing major virulence factors, although mechanistic information is scarce. The biological significance of PRRSV nsps in virus-host interactions and the technical advancements in engineering the PRRSV genome by reverse genetics are also reflected in recent developments in the area of vaccines and diagnostic assays.
Article
Porcine reproductive and respiratory syndrome virus (PRRSV) infects fully differentiated cells of the monocyte/macrophage lineage. Recently, CD163 was shown to be a cellular receptor capable of mediating infection of otherwise PRRSV non-permissive cell lines. CD163 is a macrophage differentiation antigen belonging to the scavenger receptor cysteine-rich (SRCR) family of membrane proteins. We provide a brief review of current knowledge regarding CD163 in relation to PRRSV infection, and propose a structure-based prediction of amino acid sequences involved in PRRSV interaction.
Article
We determined the disinfection efficiency of chlorine and chlorine dioxide (ClO(2)) using murine norovirus (MNV) and coliphage MS2 as surrogates for human norovirus. Experiments were performed in oxidant demand-free buffer (pH 7.2) at 5 degrees C and 20 degrees C. The extent of virus inactivation by a disinfectant was quantified using three different analytical methods: plaque, short template real-time TaqMan reverse transcriptase-polymerase chain reaction (RT-PCR), and long template RT-PCR assays. Rapid inactivation of MNV by both chlorine and chlorine dioxide was observed by the plaque assay. According to the efficiency factor Hom model, Ct values of 0.314mg/Lmin and 0.247mg/Lmin were required for a 4-log reduction of MNV at 5 degrees C by chlorine and chlorine dioxide, respectively. Lower Ct values were required at 20 degrees C. Both long template and short template RT-PCR assays significantly underestimated the virus inactivation compared to the plaque assay. Our study demonstrates that adequate treatment of water with either chlorine or ClO(2) is likely to effectively control the waterborne transmission of human norovirus.
Article
Porcine reproductive and respiratory syndrome virus (PRRSV) continues to be a threat for the pig industry. Vaccines have been developed, but these failed to provide sustainable disease control, in particular against genetically unrelated strains. Here we give an overview of current knowledge and gaps in our knowledge that may be relevant for the development of a future generation of more effective vaccines. PRRSV replicates in cells of the monocyte/macrophage lineage, induces apoptosis and necrosis, interferes with the induction of a proinflammatory response, only slowly induces a specific antiviral response, and may cause persistent infections. The virus appears to use several evasion strategies to circumvent both innate and acquired immunity, including interference with antigen presentation, antibody-mediated enhancement, reduced cell surface expression of viral proteins, and shielding of neutralizing epitopes. In particular the downregulation of type I interferon-alpha production appears to interfere with the induction of acquired immunity. Current vaccines are ineffective because they suffer both from the immune evasion strategies of the virus and the antigenic heterogeneity of field strains. Future vaccines therefore must "uncouple" the immune evasion and apoptogenic/necrotic properties of the virus from its immunogenic properties, and they should induce a broad immune response covering the plasticity of its major antigenic sites. Alternatively, the composition of the vaccine should be changed regularly to reflect presently and locally circulating strains. Preferably new vaccines should also allow discriminating infected from vaccinated pigs to support a virus elimination strategy. Challenges in vaccine development are the incompletely known mechanisms of immune evasion and immunity, lack of knowledge of viral sequences that are responsible for the pathogenic and immunosuppressive properties of the virus, lack of knowledge of the forces that drive antigenic heterogeneity and its consequences for immunogenicity, and a viral genome that is relatively intolerant for subtle changes at functional sites.
Article
The inactivation of single-particle stocks of human (type 2, Wa) and simian (SA-11) rotaviruses by chlorine dioxide was investigated. Experiments were conducted at 4 degrees C in a standard phosphate-carbonate buffer. Both virus types were rapidly inactivated, within 20 s under alkaline conditions, when chlorine dioxide concentrations ranging from 0.05 to 0.2 mg/liter were used. Similar reductions of 10(5)-fold in infectivity required additional exposure time of 120 s at 0.2 mg/liter for Wa and at 0.5 mg/liter for SA-11, respectively, at pH 6.0. The inactivation of both virus types was moderate at neutral pH, and the sensitivities to chlorine dioxide were similar. The observed enhancement of virucidal efficiency with increasing pH was contrary to earlier findings with chlorine- and ozone-treated rotavirus particles, where efficiencies decreased with increasing alkalinity. Comparison of 99.9% virus inactivation times revealed ozone to be the most effective virucidal agent among these three disinfectants.
Article
Porcine reproductive and respiratory syndrome virus (PRRSV) is an enveloped RNA virus of the Arteriviridae family, genomically related to the coronaviruses. PRRSV is the causative agent of both severe and persistent respiratory disease and reproductive failure in pigs worldwide. The PRRSV virion contains a core made of the 123 amino acid nucleocapsid (N) protein, a product of the ORF7 gene. We have determined the crystal structure of the capsid-forming domain of N. The structure was solved to 2.6 A resolution by SAD methods using the anomalous signal from sulfur. The N protein exists in the crystal as a tight dimer forming a four-stranded beta sheet floor superposed by two long alpha helices and flanked by two N- and two C-terminal alpha helices. The structure of N represents a new class of viral capsid-forming domains, distinctly different from those of other known enveloped viruses, but reminiscent of the coat protein of bacteriophage MS2.
Article
This study was undertaken to gain an understanding of the factors that influence viral RNA degradation in the presence of chlorine dioxide (ClO(2)), which will be very useful in helping to define the significance of the presence of the viral genome in disinfected water. We focused our investigation on the influence of ClO(2) on extracted RNA on the one hand, and on the infectious virus on the other. Our first results show that RNA degradation, like viral inactivation, is dose dependent. The influence of the spatial organization of the targeted genomic sequence, as well as that of its size and location (and/or sequence) on degradation of the Poliovirus 1 genome by ClO(2), was studied using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). The results show that the preferential sites of action of ClO(2) appear to be located in the untranslated regions, 5'- and 3'-UTR, a phenomenon influenced by both the presence of secondary structures and the genomic sequence in these regions. Our results also reveal a rapid decrease of infectious particles quantified by the cell culture for the applied dose. Comparison between cell culture and real-time PCR for viral detection reveals disagreement following disinfection treatment, even for the largest targeted fragment (a 6,989-base fragment representing the quasi-whole viral genome). The detection of genome fragments is insufficient to confirm the presence of the infectious virus, as each targeted fragment shows a different sensitivity. Hence, the smallest targeted fragment (76 bp) persisted throughout the analysis period, while the longest targeted fragment (6,989 bp) disappeared very rapidly. Highly sensitive regions (i.e. 5'- and 3'-UTR) should be targeted to avoid an overestimation of the risk of viral infection using molecular biology methods in water following disinfection. Further studies in this area are needed. To date, it has not been possible to routinely apply virological controls to drinking water because of the time-consuming nature of the gold standard technique (cell culture) and its inability to detect all serotypes (e.g. Norovirus). Molecular techniques (e.g. real-time RT-PCR) constitute a solution to the rapid and specific detection of all the serotypes. However, ignorance of the mechanisms of viral degradation prevents the validation of PCR for the measurement of the risk of infection to humans following disinfection treatment.