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Infectious ectromelia. A hitherto undescribed virus disease of mice

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... Today, 40 years after the eradication of smallpox, VARV still represents a threat as a bioterrorist weapon, and CPXV and monkeypox virus are the main cause of zoonotic poxvirus infections [5][6][7]. The orthopoxvirus ectromelia virus (ECTV) is the causative agent of mousepox, an acute exanthematous disease of mice that resembles smallpox and was used as a model for studying orthopoxvirus infections [8][9][10]. Mousepox was a serious threat to laboratory mouse colonies in the past [11][12][13][14], but outbreaks of mousepox in laboratory mouse colonies have been eliminated thanks to strict surveillance and improvements in animal house facilities with pathogen contention racks, filters and disinfections [11]. ...
... The first ECTV outbreak was reported in 1930 in the National Institute for Medical Research in Hampstead (London, UK) and was caused by the ECTV-Hampstead (ECTV-H) isolate ( Table 1). The disease was named "infectious ectromelia" because of the characteristic foot amputation observed in mice that recovered from infection [8]. Sixty passages in chorioalantoic membranes (CAMs) of ECTV-H resulted in the attenuated strain ECTV-Hampstead Egg (ECTV-HE) that shows a considerable reduction in virulence in outbred mice [15], and Mouse colony outbreak and cell culture passages yes [17] ECTV-Hamsptead Egg(ECTV-HE) -1949 ...
... Monkey kidney BS-C-1 cells (ATCC: CCL-26) were used for virus amplification and preparation of semi-purified viral stocks as described [34]. ECTV-H [8] and ECTV-MH [16] (original stocks from K. Dumbell) were supplied by J. Williamson (St. Mary's Hospital, Imperial College School of Medicine, London, United Kingdom); ECTV-HE was provided by A. Mullbacher (John Curtin School of Medical Research, Australian National University, Canberra, Australia) [15]; ECTV-I was provided by Y. Ichihashi (Faculty of Medicine, Niigata University, Niigata, Japan) [28]; ECTV-M1 [24], ECTV-M4 and ECTV-M5 [25] were supplied by H. Meyer (Institute of Microbiology, Federal Armed Forces Medical Academy, Munich, Germany); ECTV-MK was isolated in 2008 from wild mice in the region of Krefeld, Germany, by A. Nitsche (The Robert Koch Institute, Berlin, Germany); ECTV-M (ECTV-Moscow-3-P2) is a plaque-purified isolate provided by R. M. L. Buller (School of Medicine, Saint Louis University) [17,41]; ECTV-N is a plaque-purified isolate [34] derived from the original stock of the Naval Medical Research Institute outbreak (Bethesda, MD, USA) provided by R. M. L. Buller [35]. ...
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Ectromelia virus (ECTV), the causative agent of mousepox, has threatened laboratory mouse colonies worldwide for almost a century. Mousepox has been valuable for the understanding of poxvirus pathogenesis and immune evasion. Here, we have monitored in parallel the pathogenesis of nine ECTVs in BALB/cJ mice and report the full-length genome sequence of eight novel ECTV isolates or strains, including the first ECTV isolated from a field mouse, ECTV-MouKre. This approach allowed us to identify several genes, absent in strains attenuated through serial passages in culture, that may play a role in virulence and a set of putative genes that may be involved in enhancing viral growth in vitro. We identified a putative strong inhibitor of the host inflammatory response in ECTV-MouKre, an isolate that did not cause local foot swelling and developed a moderate virulence. Most of the ECTVs, except ECTV-Hampstead, encode a truncated version of the P4c protein that impairs the recruitment of virions into the A-type inclusion bodies, and our data suggest that P4c may play a role in viral dissemination and transmission. This is the first comprehensive report that sheds light into the phylogenetic and geographic relationship of the worldwide outbreak dynamics for the ECTV species.
... Mousepox is an acute exanthematous disease of mice caused by the orthopoxvirus (OPV) ectromelia virus (ECTV) that in the past century affected laboratory mouse colonies worldwide (Esteban and Buller, 2005;Fenner, 1981;Marchal, 1930). ECTV, like variola virus (VARV), the causative agent of smallpox, has a narrow host range and causes a severe disease with skin lesions in the later stages of the infection and a high mortality rate (Esteban and Buller, 2005). ...
... ECTV, like variola virus (VARV), the causative agent of smallpox, has a narrow host range and causes a severe disease with skin lesions in the later stages of the infection and a high mortality rate (Esteban and Buller, 2005). Mousepox was first described in 1930 in Hampstead (United Kingdom) as an infectious disease of mouse associated with high mortality and amputations in mice recovered from infection (Marchal, 1930). Following the identification of ECTV-Hampstead, ECTV has been isolated in temporally and geographically different laboratory mousepox outbreaks. ...
... Since the DRIII region appeared to be highly variable, we compared the length variation of this region in a collection of ECTV isolates available in our laboratory (Smith and Alcami, 2000): (i) ECTV-Moscow, plaque-purified from the virus isolated in an outbreak in Moscow in 1947 (Andrewes and Elford, 1947); (ii) ECTV-Hampstead, the first ECTV isolated in 1930 from London (Marchal, 1930); (iii) ECTV Hampstead-Egg and ECTV-Mill Hill, derived from the ECTV Hampstead isolate by serial passage in eggs (Smith and Alcami, 2000); (iv) ECTV-Ishibashi, a plaque purified virus derived from an outbreak in Japan in 1966 (Ichihashi and Matsumoto, 1966); (v) two isolates ECTV-MP1 (München, 1976) and ECTV-MP4 (Nürnberg, 1976) from German outbreaks (Mahnel, 1983;Osterrieder et al., 1994); (vi) ECTV-MP5 from an outbreak in Wien (Austria) in 1994 (Osterrieder et al., 1994); and (vii) ECTV-Cornell isolated in the most recent outbreak in the USA (Lipman et al., 2000). A high variability in the number of repeats was detected among all the ECTV strains ( Fig. 1) ranging from 15 repeats for ECTV Hampstead-Egg to 45 repeats estimated for ECTV-Cornell. ...
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Ectromelia virus (ECTV) is the causative agent of mousepox, a disease of laboratory mouse colonies and an excellent model for human smallpox. We report the genome sequence of two isolates from outbreaks in laboratory mouse colonies in the USA in 1995 and 1999: ECTV-Naval and ECTV-Cornell, respectively. The genome of ECTV-Naval and ECTV-Cornell was sequenced by the 454-Roche technology. The ECTV-Naval genome was also sequenced by the Sanger and Illumina technologies in order to evaluate these technologies for poxvirus genome sequencing. Genomic comparisons revealed that ECTV-Naval and ECTV-Cornell correspond to the same virus isolated from independent outbreaks. Both ECTV-Naval and ECTV-Cornell are extremely virulent in susceptible BALB/c mice, similar to ECTV-Moscow. This is consistent with the ECTV-Naval genome sharing 98.2% DNA sequence identity with that of ECTV-Moscow, and indicates that the genetic differences with ECTV-Moscow do not affect the virulence of ECTV-Naval in the mousepox model of footpad infection.
... Wspó³praca wirusologów, immunologów, neurobiologów, patologów, cytobiologów i przedstawicieli innych dyscyplin biomedycyny nad wyjanieniem komórkowych i molekularnych mechanizmów patogenezy wirusowej zachodz¹cej w orodkowym uk³adzie nerwowym (OUN) oraz odpowiedzi immunologicznej za-ka¿onego organizmu doprowadzi³a do ukszta³towania siê tak fascynuj¹cych nauk, jak neurowirusologia oraz neuroimmunologia. Zdolnoae zaka¿ania komórek OUN u cz³owieka i replikowania siê w nich posiada wiele wirusów nale¿¹cych do ró¿nych rodzin, w tym wirusy opryszczki (HSV-1, herpes simplex virus 1/HHV-1, human herpesvirus 1), wirusy polio i inne [7,20]. Niektóre wirusy, jak, na przyk³ad, HHV-1 mog¹ powodowaae utajone lub przetrwa³e zaka¿enia wra¿liwych komórek, w których kwas nukleinowy wirusa jest wbudowany w genom komórki nie wywo³uj¹c widocznych objawów klinicznych a¿ do chwili jego reaktywacji klasycznym przyk³adem jest wspomniany HHV-1, którego DNA znajduje siê w zwojach nerwu trójdzielnego mózgu u wiêkszoci ludzi i, po reaktywacji wirusa, mo¿e powodowaae w okrelonych sytuacjach (np. ...
... Skoro nie powinno siê, ze zrozumia³ych i wspomnianych ju¿ w tym artykule, wzglêdów bezpieczeñstwa, prowadziae badañ przy u¿yciu VARV, to w celu lepszego poznania w odniesieniu do prac zmie-rzaj¹cych do opracowania nowych generacji leków i bezpiecznych szczepionek anty-VARV mechanizmów patogenezy ospy prawdziwej wirus ospy myszy (ECTV) zosta³ zaakceptowany przez wirusologów i immunologów jako wirus modelowy. Wirus ten, opisany po raz pierwszy przez J. M a r c h a l a w 1930 r. [20], Sir F. M a c F a r l a n e B u r n e t dopiero w 1945 r. zaklasyfikowa³ do rodzaju Orthopoxvirus (Tab. I). ...
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The World Health Organization (WHO) announced on May 8 1980 that smallpox was the first human infectious disease eradicated from the environment. It was possible thanks to the spectacular success of the Intensified Smallpox Eradication Program initiated in 1967 by WHO. In this article, we summarize the fascinating history of smallpox variolation and vaccination. We also acknowledge Edward Jenner (1749-1823), the father of immunology and one of the world's greatest scientific visionaries, who was many years ahead of his times. Since the studies on variola virus (VARV) are not accepted by the civilized countries, public opinion and scientific community, the progress in the immunobiology of VARV and the production of modern vaccines against smallpox will be not possible without model studies both in vivo and in vitro. Also, the lack of research would hinder the understanding of virus nature and the cellular and molecular mechanisms of the disease. For this reason, in our laboratory we are conducting studies on immunobiology of ectromelia virus (ECTV) and on mousepox pathogenesis as a substitute for VARV and smallpox.
... Infectious ectromelia (ECTV) was identified in 1930 when the mouse was first introduced as an experimental laboratory animal [1]. Wild populations of rodents in Europe are suspected to be infected naturally with ECTV and the virus is transmitted easily among wild and laboratory populations under experimental conditions [2]. ...
... • Pharmacokinetics in the animal species used in orthopoxvirus infection models may not be the most relevant for dose selection in humans. 1 Adapted from Future Virology (2006) 1(2) 173-179 with permission of Future Medicine Ltd [28]. ...
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The absence of herd immunity to orthopoxviruses and the concern that variola or monkeypox viruses could be used for bioterroristic activities has stimulated the development of therapeutics and safer prophylactics. One major limitation in this process is the lack of accessible human orthopoxvirus infections for clinical efficacy trials; however, drug licensure can be based on orthopoxvirus animal challenge models as described in the “Animal Efficacy Rule”. One such challenge model uses ectromelia virus, an orthopoxvirus, whose natural host is the mouse and is the etiological agent of mousepox. The genetic similarity of ectromelia virus to variola and monkeypox viruses, the common features of the resulting disease, and the convenience of the mouse as a laboratory animal underscores its utility in the study of orthopoxvirus pathogenesis and in the development of therapeutics and prophylactics. In this review we outline how mousepox has been used as a model for smallpox. We also discuss mousepox in the context of mouse strain, route of infection, infectious dose, disease progression, and recovery from infection.
... Clinical signs and the rate of mortality depend on the strain of the virus as well as mouse genotype, age, sex, and immune status. 4,[6][7][8]10,14,18 Reports of mousepox in the United States date to the 1950s and have been linked to importation of infected mice and murine products. 4,[7][8][9]14,16,17 An outbreak spreading in 2 buildings at the Naval Medical Research Center in Maryland in 1995 was linked to commercial serum from the United States. ...
... This mouse healed by day 27 after inoculation, lacked gross and histologic lesions characteristic of mousepox (after euthanasia at 12 wk after inoculation), and had antibodies to EV but was not EV-PCR-positive. The other 7 mice had gross and histologic lesions typical of mousepox, 1,4,6,7,9,10,14 including necrosis of the spleen, liver, and lymphoid organs as well as epidermal hyperplasia and ulceration. All 4 (2 B6 and 2 BALB/cJ) mice in groups 6 through 9 that were injected with BMC died or were euthanized within 6 d. ...
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An outbreak of mousepox in a research institution was caused by Ectromelia-contaminated mouse serum that had been used for bone marrow cell culture and the cells subsequently injected into the footpads of mice. The disease initially was diagnosed by identification of gross and microscopic lesions typical for Ectromelia infection, including foci of necrosis in the liver and spleen and eosinophilic intracytoplasmic inclusion bodies in the skin. The source of infection was determined by PCR analysis to be serum obtained from a commercial vendor. To determine whether viral growth in tissue culture was required to induce viral infection, 36 mice (BALB/cJ, C57BL/6J) were experimentally exposed intraperitoneally, intradermally (footpad), or intranasally to contaminated serum or bone marrow cell cultures using the contaminated serum in the culture medium. Mice were euthanized when clinical signs developed or after 12 wk. Necropsy, PCR of spleen, and serum ELISA were performed on all mice. Mice injected with cell cultures and their cage contacts developed mousepox, antibodies to Ectromelia, and lesions, whereas mice injected with serum without cells did not. Mouse antibody production, a tool commonly used to screen biologic materials for viral contamination, failed to detect active Ectromelia contamination in mouse serum.
... ECTV naturally enters its murine host through microabrasions of the foot and, experimentally, by footpad injection. Whether naturally or experimentally acquired, ECTV replication in the footpad is substantial and often results in necrosis and loss of the limb, hence the name of the virus [15]. In susceptible mouse strains, ECTV rapidly spreads from the footpad to the dLN and subsequently to the blood and liver. ...
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The interstitial fluids in tissues are constantly drained into the lymph nodes (LNs) as lymph through afferent lymphatic vessels and from LNs into the blood through efferent lymphatics. LNs are strategically positioned and have the appropriate cellular composition to serve as sites of adaptive immune initiation against invading pathogens. However, for lymph-borne viruses, which disseminate from the entry site to other tissues through the lymphatic system, immune cells in the draining LN (dLN) also play critical roles in curbing systemic viral dissemination during primary and secondary infections. Lymph-borne viruses in tissues can be transported to dLNs as free virions in the lymph or within infected cells. Regardless of the entry mechanism, infected myeloid antigen-presenting cells, including various subtypes of dendritic cells, inflammatory monocytes, and macrophages, play a critical role in initiating the innate immune response within the dLN. This innate immune response involves cellular crosstalk between infected and bystander innate immune cells that ultimately produce type I interferons (IFN-Is) and other cytokines and recruit inflammatory monocytes and natural killer (NK) cells. IFN-I and NK cell cytotoxicity can restrict systemic viral spread during primary infections and prevent serious disease. Additionally, the memory CD8 ⁺ T-cells that reside or rapidly migrate to the dLN can contribute to disease prevention during secondary viral infections. This review explores the intricate innate immune responses orchestrated within dLNs that contain primary viral infections and the role of memory CD8 ⁺ T-cells following secondary infection or CD8 ⁺ T-cell vaccination.
... This name has been taken from the Greek word ectro, meaning abortion, and melia, which signifying limb. It was identified in 1930 in United Kingdom when the mice were first used for experiments in laboratory [4]. Young mice are highly susceptible to lethal infection as compared to adult mice. ...
... OPXVs, such as ECTV, CPXV, or raccoonpox virus, these accrued MVs become occluded into cytoplasmic ATI (6,7,31). Here, we show that the viral protein A26 skews virus maturation toward the single-membraned MV form and antagonizes maturation of the alternative double-membraned EV form. ...
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Vaccinia virus produces two types of virions known as single-membraned intracellular mature virus (MV) and double-membraned extracellular enveloped virus (EV). EV production peaks earlier when initial MV are further wrapped and secreted to spread infection within the host. However, late during infection MV accumulate intracellularly and become important for host-to-host transmission. The process that regulates this switch remains elusive and is thought to be influenced by host factors. Here we examined the hypothesis that EV and MV production are regulated by the virus through expression of F13 and the MV-specific protein A26. By switching the promoters and altering the expression kinetics of F13 and A26, we demonstrate that A26 expression downregulates EV production and plaque size, thus limiting viral spread. This process correlates with A26 association with the MV surface protein A27 and exclusion of F13, thus reducing EV titres. Thus, MV maturation is controlled by the abundance of the viral A26 protein, independently of other factors, and is rate-limiting for EV production. The A26 gene is conserved within vertebrate poxviruses, but strikingly lost in poxviruses known to be transmitted exclusively by biting arthropods. A26-mediated virus maturation thus has the appearance to be an ancient evolutionary adaptation to enhance transmission of poxviruses that has subsequently been lost from vector-adapted species, for which it may serve as a genetic signature. The existence of virus-regulated mechanisms to produce virions adapted to fulfil different functions represents a novel level of complexity in mammalian viruses with major impact on evolution, adaptation and transmission. IMPORTANCE Chordopoxviruses are mammalian viruses that uniquely produce a first type of virion adapted to spread within the host and a second type that enhances transmission between hosts, which can take place by multiple ways including direct contact, respiratory droplets, oral/fecal routes, or via vectors. Both virion types are important to balance intra-host dissemination and inter-host transmission, so virus maturation pathways must be tightly controlled. Here we provide evidence that the abundance and kinetics of expression of the viral protein A26 regulates this process by preventing formation of the first form and shifting maturation towards the second form. A26 is expressed late after the initial wave of progeny virions is produced, so sufficient viral dissemination is ensured, and provides virions with enhanced environmental stability. Conservation of A26 in all vertebrate poxviruses but those transmitted exclusively via biting arthropods reveals the importance of A26-controlled virus maturation for transmission routes involving environmental exposure.
... Studies with vaccinia virus (VACV), the prototype member of the family, established that genome replication, transcription, translation, and virion assembly occur within juxtanuclear factories (12)(13)(14). Following egress from the assembly site, some infectious mature virions (MVs) are enveloped by a double-membrane derived from endosomal and Golgi networks and transported to the cell periphery on microtubules (15)(16)(17)(18)(19). Additionally, MVs of certain poxviruses including CPXV, ectromelia virus, raccoonpox virus, canarypox virus, and fowlpox virus become embedded in ATIs that are distant from the virus factory (20)(21)(22). ATIs are comprised of an abundant 150-kDa protein containing multiple repeats of about 30 amino acids each (23,24). The ATIs are dynamic, mobile bodies with liquid gel-like properties that enlarge in part by coalescence events that depend on microtubules (25). ...
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Poxvirus genome replication, transcription, translation, and virion assembly occur at sites within the cytoplasm known as factories. Some poxviruses sequester infectious virions outside of the factories in inclusion bodies comprised of numerous copies of the 150-kDa ATI protein, which can provide stability and protection in the environment. We provide evidence that ATI mRNA is anchored by nascent peptides and translated at the inclusion sites rather than in virus factories. Association of ATI mRNA with inclusion bodies allows multiple rounds of local translation and prevents premature ATI protein aggregation and trapping of virions within the factory.
... By thin section EM, in addition to the viral factories, some poxviruses have other cytoplasmic structures know as acidophilic-type inclusions (A-type inclusions) consisting of a matrix containing the A-type inclusion protein and other proteins, with occluded intracellular mature particles [10,11] ( Figure 1A). Virus species with these inclusions include cowpox, ectromelia, raccoonpox, skunkpox, volepox, and fowlpox viruses. ...
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Electron microscopy has been instrumental in the identification of viruses by being able to characterize a virus to the family level. There are a few cases where morphologic or morphogenesis factors can be used to differentiate further, to the genus level. These include viruses in the families Poxviridae, Reoviridae, Retroviridae, Herpesviridae, Filoviridae, and Bunyaviridae.
... This can be ascribed, at least in part, to greater subversion of early immune responses by ECTV than by VACV (14,37). However, while VACV-induced inflammation remained relatively mild and eventually subsided, ECTVassociated swelling became considerable, ultimately leading to necrosis and loss of the limb within ϳ21 days of infection in most cases, consistent with previous reports (38). In both infections, we found day 10 postinfection to be the time point at which virusspecific T CD4 ϩ responses could be discriminately measured, providing an optimal signal-to-noise ratio (data not shown). ...
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Unlabelled: The factors that determine CD4+ T cell (TCD4+) specificities, functional capacity, and memory persistence in response to complex pathogens remain unclear. We explored these parameters in the C57BL/6 mouse through comparison of two highly related (>92% homology) poxviruses: ectromelia virus (ECTV), a natural mouse pathogen, and vaccinia virus (VACV), a heterologous virus that nevertheless elicits potent immune responses. In addition to elucidating several previously unidentified major histocompatibility complex class II (MHC-II)-restricted epitopes, we observed many qualitative and quantitative differences between the TCD4+ repertoires, including responses not elicited by VACV despite complete sequence conservation. In addition, we observed functional heterogeneity between ECTV- and VACV-specific TCD4+ at both a global and individual epitope level, particularly greater expression of the cytolytic marker CD107a from TCD4+ following ECTV infection. Most striking were differences during the late memory phase where, in contrast to ECTV, VACV infection failed to elicit measurable epitope-specific TCD4+ as determined by intracellular cytokine staining. These findings illustrate the strong influence of epitope-extrinsic factors on TCD4+ responses and memory. Importance: Much of our understanding concerning host-pathogen relationships in the context of poxvirus infections stems from studies of VACV in mice. However, VACV is not a natural mouse pathogen, and therefore, the relevance of results obtained using this model may be limited. Here, we explored the MHC class II-restricted TCD4+ repertoire induced by mousepox (ECTV) infection and the functional profile of the responding epitope-specific TCD4+, comparing these results to those induced by VACV infection under matched conditions. Despite a high degree of homology between the two viruses, we observed distinct specificity and functional profiles of TCD4+ responses at both acute and memory time points, with VACV-specific TCD4+ memory being notably compromised. These data offer insight into the impact of epitope-extrinsic factors on the resulting TCD4+ responses.
... Some poxviruses form large inclusions in the cytoplasm in which mature virions (MVs) are embedded. Such structures called A-type inclusions (ATIs), Downie bodies and Marchal bodies by different investigators (Downie, 1939;Goodpature and Woodruff, 1931;Kato et al., 1959;Marchal, 1930) occur within several genera of chordopoxviruses and entomopoxviruses (Bergoin et al., 1971). It is thought that these structures prolong infectivity by protecting the embedded virions from ultraviolet irradiation and other environmental stresses. ...
Article
Some orthopoxviruses including cowpox virus embed virus particles in dense bodies, comprised of the A-type inclusion (ATI) protein, which may provide long-term environmental protection. This strategy could be beneficial if the host population is sparse or spread is inefficient or indirect. However, the formation of ATI may be neutral or disadvantageous for orthopoxviruses that rely on direct respiratory spread. Disrupted ATI open reading frames in orthopoxviruses such as variola virus, the agent of smallpox, and monkeypox virus suggests that loss of this feature provided positive selection. To test this hypothesis, we constructed cowpox virus mutants with deletion of the ATI gene or another gene required for embedding virions. The ATI deletion mutant caused greater weight loss and higher replication in the respiratory tract than control viruses, supporting our hypothesis. Deletion of the gene for embedding virions had a lesser effect, possibly due to known additional functions of the encoded protein.
... In contrast, C57BL/6, which are resistant to ECTV, generally exhibit subclinical infection with lower viral titres and the development of non-fatal tissue lesions (Buller and Fenner 2007). The disease was first detected in laboratory mice (Marchal 1930), and has been reported in wild house mice associated with infected laboratory mice (McGaughey and Whitehead 1933) and in colonies of laboratory mice in various countries (Fenner 1982). The natural reservoir of ECTV is likely to be free-living Mus species, although wild rodents, such as Apodemus spp., may also be naturally infected (Buller and Fenner 2007). ...
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The wild house mouse (Mus domesticus) is not native to Australia and was introduced from Europe with early settlement. It undergoes periodic population explosions or plagues, which place significant economic and social burdens on agricultural communities. Present control mechanisms rely on improvements to farm hygiene and the use of rodenticides. This review covers over a decade of work on the use of virally vectored immunocontraception (VVIC) as an adjunct method of controlling mouse populations. Two viral vectors, ectromelia virus (ECTV) and murine cytomegalovirus (MCMV) have been tested as potential VVIC vectors: MCMV has been the most widely studied vector because it is endemic to Australia; ECTV less so because its use would have required the introduction of a new pathogen into the Australian environment. Issues such as efficacy, antigen choice, resistance, transmission, species specificity and safety of VVIC are discussed. In broad terms, both vectors when expressing murine zona pellucida 3 (mZP3) induced long-term infertility in most directly inoculated female mice. Whereas innate and acquired resistance to MCMV may be a barrier to VVIC, the most significant barrier appears to be the attenuation seen in MCMV-based vectors. This attenuation is likely to prevent sufficient transmission for broad-scale use. Should this issue be overcome, VVIC has the potential to contribute to the control of house mouse populations in Australia.
... The first ECTV isolate was the Hampstead strain, discovered in a laboratory mouse colony in London [23]. ECTV has been enzootic in the breeding stocks of mice in Europe, China and Japan [24]. ...
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Erythromelagia is a condition characterized by attacks of burning pain and inflammation in the extremeties. An epidemic form of this syndrome occurs in secondary students in rural China and a virus referred to as erythromelalgia-associated poxvirus (ERPV) was reported to have been recovered from throat swabs in 1987. Studies performed at the time suggested that ERPV belongs to the orthopoxvirus genus and has similarities with ectromelia virus, the causative agent of mousepox. We have determined the complete genome sequence of ERPV and demonstrated that it has 99.8% identity to the Naval strain of ectromelia virus and a slighly lower identity to the Moscow strain. Small DNA deletions in the Naval genome that are absent from ERPV may suggest that the sequenced strain of Naval was not the immediate progenitor of ERPV.
... Most MVs, however, are not destined to become EVs and are retained in the cytoplasm until cell lysis. The MVs of some OPXVs, including strains of cowpox virus (CXPV), ectromelia virus, fowlpox virus, and raccoonpox virus (but not vaccinia virus [VACV], monkeypox virus, or variola virus), are embedded in cytoplasmic, proteinaceous matrices called A-type inclusions (ATIs) (8,18,21,28), which are thought to protect infectious particles after release into the environment. ...
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In cells infected with some orthopoxviruses, numerous mature virions (MVs) become embedded within large, cytoplasmic A-type inclusions (ATIs) that can protect infectivity after cell lysis. ATIs are composed of an abundant viral protein called ATIp, which is truncated in orthopoxviruses such as vaccinia virus (VACV) that do not form ATIs. To study ATI formation and occlusion of MVs within ATIs, we used recombinant VACVs that express the cowpox full-length ATIp or we transfected plasmids encoding ATIp into cells infected with VACV, enabling ATI formation. ATI enlargement and MV embedment required continued protein synthesis and an intact microtubular network. For live imaging of ATIs and MVs, plasmids expressing mCherry fluorescent protein fused to ATIp were transfected into cells infected with VACV expressing the viral core protein A4 fused to yellow fluorescent protein. ATIs appeared as dynamic, mobile bodies that enlarged by multiple coalescence events, which could be prevented by disrupting microtubules. Coalescence of ATIs was confirmed in cells infected with cowpox virus. MVs were predominantly at the periphery of ATIs early in infection. We determined that coalescence contributed to the distribution of MVs within ATIs and that microtubule-disrupting drugs abrogated coalescence-mediated MV embedment. In addition, MVs were shown to move from viral factories at speeds consistent with microtubular transport to the peripheries of ATIs, whereas disruption of microtubules prevented such trafficking. The data indicate an important role for microtubules in the coalescence of ATIs into larger structures, transport of MVs to ATIs, and embedment of MVs within the ATI matrix.
... Vaccination with VACV was evaluated in mousepox resistant C57BL/6, susceptible outbred Swiss Cr:NGP (Swiss), and susceptible inbred A/NCR mice all infected via the FP route (note that C57BL/6 mice are susceptible to infection, but are resistant to lethal mousepox disease as described by (Marchal, 1930). The mousepox susceptible mouse strains are better models for smallpox as human populations are susceptible to disease, and not resistant, to morbidity and mortality following VARV infection. ...
Article
In 2001, Jackson et al. reported that murine IL-4 expression by a recombinant ectromelia virus caused enhanced morbidity and lethality in resistant C57BL/6 mice as well as overcame protective immune memory responses. To achieve a more thorough understanding of this phenomenon and to assess a variety of countermeasures, we constructed a series of ECTV recombinants encoding murine IL-4 under the control of promoters of different strengths and temporal regulation. We showed that the ECTV-IL-4 recombinant expressing the highest level of IL-4 was uniformly lethal for C57BL/6 mice even when previously immunized. The lethality of the ECTV-IL-4 recombinants resulted from virus-expressed IL-4 signaling through the IL-4 receptor but was not due to IL-4 toxicity. A number of treatment approaches were evaluated against the most virulent IL-4 encoding virus. The most efficacious therapy was a combination of two antiviral drugs (CMX001(®) and ST-246(®)) that have different mechanisms of action.
... However, the majority of MVs remain in the cytoplasm until cell lysis. The MVs of some orthopoxviruses, e.g., cowpox virus (CPXV), ectromelia virus, and raccoonpox virus, have an additional fate: they become embedded in dense, proteinaceous bodies called A-type inclusions (ATIs) that are distinguished from virus factories (6,13,14). Orthopoxviruses that do not form A-type inclusions include vaccinia virus (VACV), the prototype of the poxvirus family; variola virus, the causative agent of smallpox; and monkeypox virus, an emerging pathogen. Inclusions with embedded virions also form in cells infected with avipoxviruses and entomopoxviruses (3) and may protect virions from harsh environmental conditions during transmission between hosts. ...
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Some orthopoxviruses, e.g., the cowpox, ectromelia, and raccoonpox viruses, form large, discrete cytoplasmic inclusions within which mature virions (MVs) are embedded by a process called occlusion. These inclusions, which may protect occluded MVs in the environment, are composed of aggregates of the A-type inclusion protein (ATIp), which is truncated in orthopoxviruses such as vaccinia virus (VACV) and variola virus that fail to form inclusions. In addition to an intact ATIp, occlusion requires the A26 protein (A26p). Although VACV contains a functional A26p, determined by complementation of a cowpox virus occlusion-defective mutant, its role in occlusion was unknown. We found that restoration of the full-length ATI gene was sufficient for VACV inclusion formation and the ensuing occlusion of MVs. A26p was present in inclusions even when virion assembly was inhibited, suggesting a direct interaction of A26p with ATIp. Analysis of a panel of ATIp mutants indicated that the C-terminal repeat region was required for inclusion formation and the N-terminal domain for interaction with A26p and occlusion. A26p is tethered to MVs via interaction with the A27 protein (A27p); A27p was not required for association of A26p with ATIp but was necessary for occlusion. In addition, the C-terminal domain of A26p, which mediates A26p-A27p interactions, was necessary but insufficient for occlusion. Taken together, the data suggest a model for occlusion in which A26p has a bridging role between ATIp and A27p, and A27p provides a link to the MV membrane.
... ECTV, the causative agent of mousepox, can be naturally found in wild mice. Several isolates have been described since its first discovery in 1929 [34] and ECTV strain Moscow is the most virulent [35,36]. The pathogenesis of smallpox in humans caused by VARV infection is closely mirrored by mousepox, especially in C57BL/6 mice [10]. ...
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Current prophylactic vaccines work via the induction of B and T cell mediated memory that effectively control further replication of the pathogen after entry. In the case of therapeutic or post-exposure vaccinations the situation is far more complex, because the pathogen has time to establish itself in the host, start producing immune-inhibitory molecules and spread into distant organs. So far it is unclear which immune parameters have to be activated in order to thwart an existing lethal infection. Using the mousepox model, we investigated the immunological mechanisms responsible for a successful post-exposure immunization with modified vaccinia Ankara (MVA). In contrast to intranasal application of MVA, we found that intravenous immunization fully protected mice infected with ectromelia virus (ECTV) when applied three days after infection. Intravenous MVA immunization induced strong innate and adaptive immune responses in lethally infected mice. By using various gene-targeted and transgenic mouse strains we show that NK cells, CD4 T cells, CD8 T cells and antibodies are essential for the clearance of ECTV after post-exposure immunization. Post-exposure immunization with MVA is an effective measure in a murine model of human smallpox. MVA activates innate and adaptive immune parameters and only a combination thereof is able to purge ECTV from its host. These data not only provide a basis for therapeutic vaccinations in the case of the deliberate release of pathogenic poxviruses but possibly also for the treatment of chronic infections and cancer.
... Several other OPXV species are known to be associated with rodents, but the specific nature of these associations remains unknown. Ectromelia virus was described from captive colonies of lab mice (Mus spp) and some strains are highly lethal to this rodent species, however almost nothing is known regarding its natural distribution [8,9]. Monkeypox virus was initially isolated from captive non-human primates in Denmark [10], and was later associated with human disease [11]. ...
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The data presented herein support the North American orthopoxviruses (NA OPXV) in a sister relationship to all other currently described Orthopoxvirus (OPXV) species. This phylogenetic analysis reaffirms the identification of the NA OPXV as close relatives of "Old World" (Eurasian and African) OPXV and presents high support for deeper nodes within the Chordopoxvirinae family. The natural reservoir host(s) for many of the described OPXV species remains unknown although a clear virus-host association exists between the genus OPXV and several mammalian taxa. The hypothesized host associations and the deep divergence of the OPXV/NA OPXV clades depicted in this study may reflect the divergence patterns of the mammalian faunas of the Old and New World and reflect a more ancient presence of OPXV on what are now the American continents. Genes from the central region of the poxvirus genome are generally more conserved than genes from either end of the linear genome due to functional constraints imposed on viral replication abilities. The relatively slower evolution of these genes may more accurately reflect the deeper history among the poxvirus group, allowing for robust placement of the NA OPXV within Chordopoxvirinae. Sequence data for nine genes were compiled from three NA OPXV strains plus an additional 50 genomes collected from Genbank. The current, gene sequence based phylogenetic analysis reaffirms the identification of the NA OPXV as the nearest relatives of "Old World" OPXV and presents high support for deeper nodes within the Chordopoxvirinae family. Additionally, the substantial genetic distances that separate the currently described NA OPXV species indicate that it is likely that many more undescribed OPXV/NA OPXV species may be circulating among wild animals in North America.
... It is well known that ectromelia (mousepox), an infectious disease of mice, is caused by a dsDNA virus belonging to the family Poxviridae, genus Orthopoxvirus [17]. The disease is endemic in mouse colonies around the world [6,8,15,16,23]. Due to the widespread use of mice in biomedical research it is important to study the biology of EV strains characteristic for a given country. ...
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Three strains of viruses have been identified as ectromedia virus (EV) based on their origin, clinical features, morphology, size of virions (140 x 220 nm), replicative ability and specific cytoplasmatic fluorescence. The mean diameter of plaques produced by EV strains was 0.76 mm (range 0.5-1.0 mm). The neutralizing properties of the tested sera were evaluated by seroneutralization (SN) and hemagglutination inhibition (HAI) tests.
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Background Ectromelia virus (ECTV) is the causative agent of mousepox in mice. In the past century, ECTV was a serious threat to laboratory mouse colonies worldwide. Recombinase polymerase amplification (RPA), which is widely used in virus detection, is an isothermal amplification method. Results In this study, a probe-based RPA detection method was established for rapid and sensitive detection of ECTV.Primers were designed for the highly conserved region of the crmD gene, the main core protein of recessive poxvirus, and standard plasmids were constructed. The lowest detection limit of the ECTV RT- RPA assay was 100 copies of DNA mol-ecules per reaction. In addition, the method showed high specificity and did not cross-react with other common mouse viruses.Therefore, the practicability of the RPA method in the field was confirmed by the detection of 135 clinical samples. The real-time RPA assay was very similar to the ECTV real-time PCR assay, with 100% agreement. Conclusions In conclusion, this RPA assay offers a novel alternative for the simple, sensitive, and specific identification of ECTV, especially in low-resource settings.
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This review provides a brief history of the impacts that a human-specific Orthopoxvirus (OPXV), Variola virus, had on mankind, recalls how critical vaccination was for the eradication of this disease, and discusses the consequences of discontinuing vaccination against OPXV. One of these consequences is the emergence of zoonotic OPXV diseases, including Monkeypox virus (MPXV). The focus of this manuscript is to compare pathology associated with zoonotic OPXV infection in veterinary species and in humans. Efficient recognition of poxvirus lesions and other, more subtle signs of disease in multiple species is critical to prevent further spread of poxvirus infections. Additionally included are a synopsis of the pathology observed in animal models of MPXV infection, the recent spread of MPXV among humans, and a discussion of the potential for this virus to persist in Europe and the Americas.
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Ectromelia virus (ECTV) is an orthopoxvirus that causes mousepox in mice. Members of the genus orthopoxvirus are closely related and include variola (the causative agent of smallpox in humans), monkeypox, and vaccinia. Common features of variola virus and ECTV further include a restricted host range and similar disease progression in their respective hosts. Mousepox makes an excellent small animal model for smallpox to investigate pathogenesis, vaccine and antiviral agent testing, host-virus interactions, and immune and inflammatory responses. The availability of a wide variety of inbred, congenic, and gene-knockout mice allows detailed analyses of the host response. ECTV mutant viruses lacking one or more genes encoding immunomodulatory proteins are being used in numerous studies in conjunction with wild-type or gene-knockout mice to study the functions of these genes in host-virus interactions. The methods used for propagation of ECTV in cell culture, purification, and quantification of infectious particles through viral plaque assay are described. © 2018 by John Wiley & Sons, Inc.
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Variola virus (VARV), the causative agent of smallpox, is an exclusively human virus belonging to the genus Orthopoxvirus, which includes many other viral species covering a wide range of mammal hosts, such as vaccinia, cowpox, camelpox, taterapox, ectromelia and monkeypox virus. The tempo and mode of evolution of Orthopoxviruses were reconstructed using a Bayesian phylodynamic framework by analysing 80 hemagglutinin sequences retrieved from public databases. Bayesian phylogeography was used to estimate their putative ancestral hosts. In order to estimate the substitution rate, the tree including all of the available Orthopoxviruses was calibrated using historical references dating the South American variola minor clade (alastrim) to between the XVI and XIX century. The mean substitution rate determined by the analysis was 6.5 × 10-6substitutions/site/year. Based on this evolutionary estimate, the time of the most recent common ancestor of the genus Orthopoxvirus was placed at about 10,000 years before the present. Cowpox virus was the species closest to the root of the phylogenetic tree. The root of VARV circulating in the XX century was estimated to be about 700 years ago, corresponding to about 1300 AD. The divergence between West African and South American VARV went back about 500 years ago (falling approximately in the XVI century). A rodent species is the most probable ancestral host from which the ancestors of all the known Orthopoxviruses were transmitted to the other mammal host species, and each of these species represented a dead-end for each new poxvirus species, without any further inter-specific spread. This article is protected by copyright. All rights reserved.
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Rodents are distributed throughout the world and interact with humans in many ways. They provide vital ecosystem services, some species are useful models in biomedical research and some are held as pet animals. However, many rodent species can have adverse effects such as damage to crops and stored produce, and they are of health concern because of the transmission of pathogens to humans and livestock.The first rodent viruses were discovered by isolation approaches and resulted in break-through knowledge in immunology, molecular and cell biology, and cancer research. In addition to rodent-specific viruses, rodent-borne viruses are causing a large number of zoonotic diseases. Most prominent examples are reemerging outbreaks of human hemorrhagic fever disease cases caused by arena- and hantaviruses. In addition, rodents are reservoirs for vector-borne pathogens, such as tick-borne encephalitis virus and Borrelia spp., and may carry human pathogenic agents, but likely are not involved in their transmission to human.In our days, next-generation sequencing or high-throughput sequencing (HTS) is revolutionizing the speed of the discovery of novel viruses, but other molecular approaches, such as generic RT-PCR/PCR and rolling circle amplification techniques, contribute significantly to the rapidly ongoing process. However, the current knowledge still represents only the tip of the iceberg, when comparing the known human viruses to those known for rodents, the mammalian taxon with the largest species number. The diagnostic potential of HTS-based metagenomic approaches is illustrated by their use in the discovery and complete genome determination of novel borna- and adenoviruses as causative disease agents in squirrels.In conclusion, HTS, in combination with conventional RT-PCR/PCR-based approaches, resulted in a drastically increased knowledge of the diversity of rodent viruses. Future improvements of the used workflows, including bioinformatics analysis, will further enhance our knowledge and preparedness in case of the emergence of novel viruses. Classical virological and additional molecular approaches are needed for genome annotation and functional characterization of novel viruses, discovered by these technologies, and evaluation of their zoonotic potential.
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Today's laboratory mouse, Mus musculus, has its origins as the 'house mouse' of North America and Europe. Beginning with mice bred by mouse fanciers, laboratory stocks (outbred) derived from M. musculus musculus from eastern Europe and M. m. domesticus from western Europe were developed into inbred strains. Since the mid-1980s, additional strains have been developed from Asian mice (. M. m. castaneus from Thailand and M. m. molossinus from Japan) and from M. spretus which originated from the western Mediterranean region.
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Most poxviruses encode a homolog of a ~200,000-kDa membrane protein originally identified in variola virus. We investigated the importance of the ectromelia virus (ECTV) homolog C15 in a natural infection model. In cultured mouse cells, the replication of a mutant virus with stop codons near the N-terminus (ECTV-C15Stop) was indistinguishable from a control virus (ECTV-C15Rev). However, for a range of doses injected into the footpads of BALB/c mice there was less mortality with the mutant. Similar virus loads were present at the site of infection with mutant or control virus whereas there was less ECTV-C15Stop in popliteal and inguinal lymph nodes, spleen and liver indicating decreased virus spread and replication. The latter results were supported by immunohistochemical analyses. Decreased spread was evidently due to immune modulatory activity of C15, rather than to an intrinsic viral function, as the survival of infected mice depended on CD4+ and CD8+ T cells.
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In 2007, the United States– Food and Drug Administration (FDA) issued guidance concerning animal models for testing the efficacy of medical countermeasures against variola virus (VARV), the etiologic agent for smallpox. Ectromelia virus (ECTV) is naturally-occurring and responsible for severe mortality and morbidity as a result of mousepox disease in the murine model, displaying similarities to variola infection in humans. Due to the increased need of acceptable surrogate animal models for poxvirus disease, we have characterized ECTV infection in the BALB/c mouse. Mice were inoculated intranasally with a high lethal dose (125 PFU) of ECTV, resulting in complete mortality 10 days after infection. Decreases in weight and temperature from baseline were observed eight to nine days following infection. Viral titers via quantitative polymerase chain reaction (qPCR) and plaque assay were first observed in the blood at 4.5 days post-infection and in tissue (spleen and liver) at 3.5 days post-infection. Adverse clinical signs of disease were first observed four and five days post-infection, with severe signs occurring on day 7. Pathological changes consistent with ECTV infection were first observed five days after infection. Examination of data obtained from these parameters suggests the ECTV BALB/c model is suitable for potential use in medical countermeasures (MCMs) development and efficacy testing.
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1. We succeeded in getting monocytes with ectromelia inclusion bodies from the peritoneal cavity of the intraabdominally infected mice. 2. By this method, quantitative and qualitative development of inclusion bodies and cell reaction in ascites following infection were investigated. The inclusion bodies appear in the periphery zone of the cytoplasm having completely no relation with centrosphere of monocytes, and increase their volume gradually. 3. In the supravital state the inclusion bodies stained positive with neutral red and fuchsin but negative with nile blue, brilliant cresyl blue and bordeaux BX. 4. Elementary bodies within the inclusion bodies having blue brilliant points were found in the supravital preparations by the dark ground microscope. 5. It was possible to take ultra-violet photomicrographs of the infected monocytes in the supravital preparations. From data obtained by this method we observed the fine figures of elementary bodies in the ectromelia inclusion bodies corresponding to the blue points which had been found by the dark ground microscope. Absorption of ultra-violet rays by inclusion bodies is much less than by the nuclei, and there is no difference between that of the inclusion, bodies and that of the protoplasm. The results obtained from the ultra-violet microscopy coincide with the other results that the inclusion bodies give a negative Feulgen reaction in smear preparation. In this case the negative Feulgen test do not mean inevitably the denial of desoxyribonucleic nature of the virus nucleic acid.
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Die Verfasser haben an 207 untersuchten Personen festgestellt, da dasToxoplasma-Antigen fr die Hautprobe, das aus den im Museperitonealexsudat vorhandenen Toxoplasmen hergestellt wird, thermostabil ist. Durch erhhte Temperatur (100 C/60 min bzw. 1,5 Atm./20 min) wird seine Aktivitt nicht gendert oder herabgesetzt. Zum klinischen Gebrauch wird ein autoklaviertes Antigen empfohlen. Dadurch werden die Bedenken einiger Fachleute endgltig beseitigt, da einige Virusarten, welche bei Musen spontan vorkommen und eventuell onkogen wirken, mit dem Toxoplasmin in die Haut der untersuchten Patienten gelangen knnten. Es ist bis jetzt keine Virusart bekannt, welche die Temperatur von 100 C berstehen knnte. Durch Hitzebehandlung wird also die Sterilitt des Prparates und damit die Unschdlichkeit des Toxoplasmin-Testes gewhrleistet.
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Vaccinia virus (VACV) stimulates long-term immunity against highly pathogenic orthopoxvirus infection of humans (smallpox) and mice (mousepox [ectromelia virus {ECTV}]) despite the lack of a natural host-pathogen relationship with either of these species. Previous research revealed that VACV is able to induce polyfunctional CD8(+) T-cell responses after immunization of humans. However, the degree to which the functional profile of T cells induced by VACV is similar to that generated during natural poxvirus infection remains unknown. In this study, we monitored virus-specific T-cell responses following the dermal infection of C57BL/6 mice with ECTV or VACV. Using polychromatic flow cytometry, we measured levels of degranulation, cytokine expression (gamma interferon [IFN-γ], tumor necrosis factor alpha [TNF-α], and interleukin-2 [IL-2]), and the cytolytic mediator granzyme B. We observed that the functional capacities of T cells induced by VACV and ECTV were of a similar quality in spite of the markedly different replication abilities and pathogenic outcomes of these viruses. In general, a significant fraction (≥50%) of all T-cell responses were positive for at least three functions both during acute infection and into the memory phase. In vivo killing assays revealed that CD8(+) T cells specific for both viruses were equally cytolytic (∼80% target cell lysis after 4 h), consistent with the similar levels of granzyme B and degranulation detected among these cells. Collectively, these data provide a mechanism to explain the ability of VACV to induce protective T-cell responses against pathogenic poxviruses in their natural hosts and provide further support for the use of VACV as a vaccine platform able to induce polyfunctional T cells.
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Thesis research directed by: Cell Biology & Molecular Genetics. Title from t.p. of PDF. Thesis (Ph. D.) -- University of Maryland, College Park, 2006. Includes bibliographical references. Text.
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Some orthopoxviruses produce large proteinaceous intracellular bodies, known as A-type inclusions (ATIs) during infection of host cells. Virions associate with ATIs resulting in distinct phenotypes referred to as V+, V+/ and V⁻. The phenotype V+ has the virions embedded in the ATI matrix; V⁻ has no virions embedded within or on the surface of the ATI matrix, whereas an aberrant phenotype, the V+/ has virions only on the surface of ATIs. Viruses that do not produce ATI are designated as V⁰. Recombinant viruses generated from a V+ cowpox virus (CPXV) and a V⁰ transgenic vaccinia virus (VACV) produced aberrant V+/ ATIs. ATI phenotype is dependent on the A-type inclusion protein (Atip) and the P4c protein. We sequenced the atip and p4c genes of parental and progeny recombinant viruses as well as their flanking sequences. The atip and p4c open reading frames were identical in parental V+ CPXV and hybrid V+/ progenies. Our results suggest that additional viral gene(s) are required for the formation of wild type V+ ATI.
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Molluscum contagiosum virus propagated in FL cells of human amnion origin has a one-step growth cycle time of 12 to 14 h. The appearance and exponential increase of intracellular virus preceded the release of extracellular virus by approximately 2 h. Demonstration of comparable titers of extracellular and intracellular virus at the end of the replication cycle indicated that a substantial amount of virus remained associated with cells exhibiting cytopathogenic changes. Mean buoyant density values of virus in sucrose ranged from 1.275 to 1.278 g/cm3, but in CsCl the virus banded at densities at 1.325 to 1.340 and 1.261 to 1.281 g/cm3. Although virus infectivity was not affected by high concentrations of CsCl, it was found by polyacrylamide gel electrophoresis that the salt removed several nonglycosylated polypeptides with estimated molecular weights of 15,000 to 60,000. This suggested that the high-density band (1.325 to 1.340) may reflect the loss of these structural components. The half-life of virus infectivity was approximately 26.5 h at 26 degrees C and 11.2 h at 37 degrees C. Although the virus was rapidly inactivated at 50 degrees C, it could be stabilized at this temperature by the presence of 1.0 M MgCl2. Virus did not agglutinate newborn chick, adult chicken, or type "0" human erythrocytes. Virus infectivity was found to be sensitive to acid pH but resistant to treatment with diethyl ether or chloroform. The replication of molluscum virus in FL cells was not inhibited by 5-iodo-2'-deoxyuridine, 5-bromo-2'-deoxyuridine, or cytosine arabinonucleoside in noncytotoxic concentrations of 200 to 400 mug/ml, but greater than 99% reduction in the yield of herpes simplex virus or vaccinia virus in FL cells was obtained with 200 mug of these compounds per ml. Guanidinium chloride in concentrations of 100 to 200 mug/ml reduced molluscum virus yields by more than 99.9%.
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The pathogenesis and transmission of infection with the Moscow strain of ectromelia virus were studied in inbred mice. BALB/cAnNcr had high morbidity and mortality and C57BL/6Ncr (B6) mice had high morbidity and low mortality. Virus was detected in B6 mice for 2 weeks after subcutaneous (s.c.) inoculation and infected mice developed lesions compatible with acute mousepox. B6 inoculated by footpad transmitted infection to cagemates for up to five weeks and soiled cages that had housed infected mice were infectious for three weeks. S.c.-inoculated B6 mice also transmitted by contact for 2 weeks. Transmission was attributed to oronasal excretion of virus. Airborne transmission of infection between adjacent cages occurred at a low rate. Ectromelia virus-free progeny were derived from previously infected dams. These studies indicate that the highly virulent and infectious Moscow strain of ectromelia virus caused self-limiting infection in inbred mice and that direct contact is the most efficient means of transmission. These findings support the concept that mousepox can be contained by husbandry practices that minimize or eliminate the spread of infection by direct contact or fomites.
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Cowpox virus clones (A- clones) deficient in production of type A inclusions were isolated from two cowpox strains, Amsterdam and 53. These clones did not differ from their parents in major markers such as pock morphology in chorioallantoic membranes and pathogenicity in the rabbit skin. However, the LS antigens induced by A- clones developed precipitin lines in agar gel diffusion tests, while the antigens from their parents failed to precipitate. Immunofluorescence and agar gel diffusion tests revealed that antigens detectable by antisera against purified type A inclusions and LS antigens were closely related to each other. These findings suggest that the A- clones might be variants of cowpox virus which have lost the ability to assemble LS antigens into type A inclusions.
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A gene was identified in camelpox virus strain CP-1 that is similar to the 160K gene of cowpox virus strain Brighton (BR) that encodes the A-type inclusion body protein (ATIP). The CP-1 gene was mapped, sequenced, and the presence of the ATIP-specific mRNA was demonstrated. The open reading frame [2178 nucleotides (nt)] was found at a similar position in the CP genome as the one reported for the cowpox virus 160K ATI gene. DNA sequence comparison revealed a deletion of two adjacent adenine residues relative to cowpox virus BR, generating a reading frame shift accompanied by the formation of a translational stop codon. An identical deletion has been described for vaccinia virus strain Western Reserve. The DNA sequence of the corresponding region of monkeypox virus strain Copenhagen revealed a deletion leading to a putative stop codon 75 nt upstream of the same stop codons in the camelpox and vaccinia virus genes. These findings are consistent with the expression of truncated ATIPs, of 94K in vaccinia and camelpox viruses and of 92K in monkeypox virus. In addition, a deletion of 789 bp could be localized downstream of the ATI open reading frame in camelpox virus isolates of different origin. This causes the transcription of a shortened ATI-specific mRNA (3.7 kb) relative to vaccinia and cowpox viruses (both 4.5 kb). The similarity observed in ATIP-encoding and flanking sequences might suggest that vaccinia and camelpox viruses are descended from a common ancestor.
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Mousepox was diagnosed in and eradicated from a laboratory mouse colony at the Naval Medical Research Institute. The outbreak began with increased mortality in a single room; subsequently, small numbers of animals in separate cages in other rooms were involved. Signs of disease were often mild, and overall mortality was low; BALB/cByJ mice were more severely affected, and many of them died spontaneously. Conjunctivitis was the most common clinical sign of disease in addition to occasional small, crusty scabs on sparsely haired or hairless areas of skin. Necropsy findings included conjunctivitis, enlarged spleen, and pale liver. Hemorrhage into the pyloric region of the stomach and proximal portion of the small intestine was observed in experimentally infected animals. In immune competent and immune deficient mice, the most common histologic finding was multifocal to coalescing splenic necrosis; necrosis was seen less frequently in liver, lymph nodes, and Peyer's patches. Necrosis was rarely observed in ovary, vagina, uterus, colon, or lung. Splenic necrosis often involved over 50% of the examined tissue, including white and red pulp. Hepatic necrosis was evident as either large, well-demarcated areas of coagulative necrosis or as multiple, random, interlacing bands of necrosis. Intracytoplasmic eosinophilic inclusion bodies were seen in conjunctival mucosae and haired palpebra. Ectromelia virus was confirmed as the causative agent of the epizootic by electron microscopy, immunohistochemistry, animal inoculations, serologic testing, virus isolation, and polymerase chain reaction. Serologic testing was of little value in the initial stages of the outbreak, although 6 weeks later, orthopoxvirus-specific antibody was detected in colony mice by indirect fluorescent antibody and enzyme-linked immunosorbent assay procedures. The outbreak originated from injection of mice with a contaminated, commercially produced, pooled mouse serum. The most relevant concern may be the unknown location of the source of the virus and the presence of a reservoir for this virus within the United States.
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