Determinants of monovalent oral polio vaccine mutagenesis in vaccinated elderly people.
ABSTRACT Live oral poliovirus vaccine (OPV) strains can mutate and recombine during replication in the host. Trivalent OPV has long been used to restrain wild-type poliovirus in developing countries. However, recently WHO advocates using monovalent OPV (mOPV) to finally eradicate poliovirus world-wide. We analysed polioviruses recovered from the faeces of 101 elderly patients (divided into three groups by immune status) challenged with mOPV-1 or mOPV-3. A high number of nucleotide mutations was found in the viral capsid-protein-encoding regions. Some of these mutations caused amino acid changes in or near regions with neutralizing epitopes, especially in mOPV-1-derived strains. The quantities of mutations in recovered poliovirus strains correlated with prevaccination immune status (seronegatives have more mutations) and excretion duration. Duration of excretion appears to be the dominant factor for the accumulation of mutations in mOPV-derived strains in vaccinated elderly people.
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ABSTRACT: Viruses belonging to the family Picornaviridae are small, non-enveloped viruses with a single-stranded, positive-sense RNA genome. Up to present, thirteen genera within this large family have been designated by the International Committee on Taxonomy of Viruses: Aphtovirus, Erbovirus, Teschovirus, Sapelovirus, Senecavirus, Tremovirus, Avihepatovirus, Cardiovirus, Hepatovirus, Cosavirus, Parechovirus, Kobuvirus and Enterovirus (Fig. 1). Members within the latter six genera have been reported to cause human disease. Enteroviruses are, next to viruses of the Herpesviridae family, the major viral cause of neurologic disease with a known etiology in humans, including meningitis, encephalitis and acute flaccid paralysis (24, 38, 47). By that they form a serious threat for human health. A well known representative of these is poliovirus (species Human enterovirus C), which has inextricably been associated with large outbreaks of neurologic disease in children. This thesis will focus on prevalence and genetic diversity of human enteroviruses (belonging to species A to D) in the context of poliovirus eradication.
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ABSTRACT: Fracture toughness of three crystalline Calcite marbles, which are different only in grain size and distribution, is determined under modes I and II and mixed mode I–II loading conditions using Cracked Chevron-Notched Brazilian Disc (CCNBD) and Hollow Centre Cracked Disc (HCCD) specimens. The results show that mode I fracture toughness (KIC) is correlated negatively with grain size. For each marble, HCCD yields lower values of fracture toughness, compared with CCNBD. This difference is negligible under mode I loading condition; while it becomes larger as loading condition transits from mode I to mode II. Measured values of P-wave velocity (VP), Brazilian tensile strength (σtB) and Schmidt hammer hardness are in direct relation with KIC of the marbles. The obtained results are compared with three fracture criteria, in which the Minimum Strain Energy Density (MSED) criterion has provided better correlations with different critical combinations of modes I and II Stress Intensity Factors.International Journal of Rock Mechanics and Mining Sciences 10/2011; 48(7):1123-1134. DOI:10.1016/j.ijrmms.2011.06.015
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ABSTRACT: The progress of the Global Polio Eradication Initiative is monitored by acute flaccid paralysis (AFP) surveillance supplemented with environmental surveillance in selected areas. To assess the sensitivity of environmental surveillance, stools from (re)vaccinated elderly persons with a low seroprevalence and from wastewater were concurrently collected and analyzed in the Netherlands over a prolonged period of time. A total number of 228 healthy individuals with different levels of immunity were challenged with monovalent oral polio vaccine serotype 1 or 3. Poliovirus concentrations were determined by the titration of fecal suspensions on poliovirus-sensitive L20B cells and of sewage concentrates by L20B monolayer plaque assay. Almost half of the individuals (45%) shed poliovirus on day 3 after challenge, which peaked (57%) on day 8 with an average poliovirus excretion of 1.3 × 10(5) TCID(50) per g of feces and gradually decreased to less than 5% on day 42. The virus concentrations in sewage peaked on days 6 to 8 at approximately 100 PFU per liter, remained high until day 14, and subsequently decreased to less than 10 PFU per liter on day 29. The estimated poliovirus concentration in sewage approximated the measured initial virus excretion in feces, within 1 log(10) variation, resulting in a sensitivity of detection of 100 infected but mostly asymptomatic individuals in tens of thousands of individuals. An additional second peak observed in sewage may indicate secondary transmission missed by enterovirus or AFP surveillance in patients. This enables the detection of circulating poliovirus by environmental surveillance, supporting its feasibility as an early warning system.Applied and Environmental Microbiology 03/2012; 78(11):3800-5. DOI:10.1128/AEM.07972-11