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Virus Infectivity (virus + infectivity)
Selected AbstractsVariation and infectivity neutralization in influenzaIMMUNOLOGY, Issue 1 2006Marcel Knossow Summary Worldwide epidemics of influenza are caused by viruses that normally infect other species, particularly waterfowl, and that contain haemagglutinin membrane glycoproteins (HAs) to which the human population has no immunity. Anti-HA immunoglobulins neutralize influenza virus infectivity. In this review we outline structural differences that distinguish the HAs of the 16 antigenic subtypes (H1,16) found in viruses from avian species. We also describe structural changes in HA required for the effective transfer to humans of viruses containing three of them, H1, H2 and H3, in the 1918 (Spanish), the 1957 (Asian) and the 1968 (Hong Kong) pandemics, respectively. In addition, we consider changes that may be required before the current avian H5 viruses could pass from human to human. [source] Inactivated infectious haematopoietic necrosis virus (IHNV) vaccinesJOURNAL OF FISH DISEASES, Issue 10 2008E Anderson Abstract The inactivation dynamics of infectious haematopoietic necrosis virus (IHNV) by ,-propiolactone (BPL), binary ethylenimine (BEI), formaldehyde or heat and the antigenic and immunogenic properties of the inactivated vaccines were evaluated. Chemical treatment of IHNV with 2.7 mm BPL, 1.5 mm BEI or 50 mm formaldehyde abolished virus infectivity within 48 h whereas heat treatment at 50 or 100 °C rendered the virus innocuous within 30 min. The inactivated IHNV vaccines were recognized by rainbow trout, Oncorhynchus mykiss, IHNV-specific antibodies and were differentially recognized by antigenic site I or antigenic site II IHNV glycoprotein-specific neutralizing monoclonal antibodies. The BPL inactivated whole virus vaccine was highly efficacious in vaccinated rainbow trout challenged by waterborne exposure to IHNV 7, 28, 42 or 56 days (15 °C) after immunization. The formaldehyde inactivated whole virus vaccine was efficacious 7 or 11 days after vaccination of rainbow trout but performed inconsistently when tested at later time points. The other vaccines tested were not efficacious. [source] Titration of hepatitis B virus infectivity in the sera of pre-acute and late acute phases of HBV infection: Transmission experiments to chimeric mice with human liver repopulated hepatocytesJOURNAL OF MEDICAL VIROLOGY, Issue 12 2008Ayako Tabuchi Abstract Studies of hepatitis B virus (HBV) infection in non-human primates such as chimpanzees are no longer possible due to ethical considerations and the endangered status of chimpanzees since April 2007 in Japan. A human hepatocyte transplanted chimeric mouse was used to characterize HBV infectivity in serial stages of acute infection. Chimeric mice were inoculated intravenously with serum samples obtained from an experimentally infected chimpanzee with HBV. Sera from the pre-acute phases (i.e., rump-up viremia prior to anti-HBc) and late acute phases (i.e., declining phase of HBsAg and anti-HBcAb positive) were collected from the chimpanzees 57 and 244 days after inoculation. These sera contained 2.6,×,106 and 2.8,×,106 copies/ml of HBV DNA, respectively. Three chimeric mice inoculated intravenously with 100 µl of pre-acute serum (equivalent to 100 copy of HBV DNA) developed an HBV infection. The three chimeric mice that received 100 µl of pre-acute serum (equivalent to 101 copies of HBV DNA), developed high levels of serum HBV DNA. None of the three chimeric mice inoculated with 100 µl of 1:104 dilution (equivalent to 101 copies of HBV DNA) of late-acute serum was infected, while only one of three chimeric mice inoculated with 100 µl of 1:103 dilution (equivalent to 102 copies of HBV DNA) of late-acute serum developed an HBV infection. Based on these results, chimeric mice can be used as animal models for the study of HBV infectivity, pathogenesis and control. The results show that pre-acute phase HBV serum is about 100-times more infectious than late acute phase serum. J. Med. Virol. 80:2064,2068, 2008. © 2008 Wiley-Liss, Inc. [source] Inter-subtype cross-neutralizing antibodies recognize epitopes on cell-associated HIV-1 virionsJOURNAL OF MEDICAL VIROLOGY, Issue 2 2003Helen Donners Abstract HIV-1 infected individuals with cross-neutralizing antibodies against primary HIV-1 isolates belonging to Group M (env A-H) and O, are identified. To investigate the neutralization-kinetics of primary isolates with these antibodies, different neutralization assay conditions are compared. Each set is summarized as a/b/c where a is the time in hours for which antibody is incubated with virus, b is the time in hours allowed for virus to absorb to cells, c is the total culture period in days, from the cells' first exposure to virus, before antigen production (peripheral blood mononuclear cells) or number of fluorescent cells (GHOST) are measured. In HIV-infected individuals, neutralizing antibodies can be detected against a wide range of primary isolates (Group M; A,H and Group O) in PBMC-assays with short incubation phases (1/2/7 or 1/24/7). If cultures are extended (1/2/14 or 1/24/14), however, neutralization can be lost. In kinetic experiments, neutralization can even be seen without pre-incubation (a,=,0 hr). This study shows that neutralization of primary HIV isolates by cross-reactive antibodies can continue after the virus has bound to its target cell. This neutralization, however, is not an all or nothing loss in virus infectivity. Most often it leads only to a reduction in viral replication rates. J. Med. Virol. 69:173,181, 2003. © 2003 Wiley-Liss, Inc. [source] Viral Control of Phytoplankton Populations,a Review,THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2004CORINA P. D. BRUSSAARD ABSTRACT. Phytoplankton population dynamics are the result of imbalances between reproduction and losses. Losses include grazing, sinking, and natural mortality. As the importance of microbes in aquatic ecology has been recognized, so has the potential significance of viruses as mortality agents for phytoplankton. The field of algal virus ecology is steadily changing and advancing as new viruses are isolated and new methods are developed for quantifying the impact of viruses on phytoplankton dynamics and diversity. With this development, evidence is accumulating that viruses can control phytoplankton dynamics through reduction of host populations, or by preventing algal host populations from reaching high levels. The identification of highly specific host ranges of viruses is changing our understanding of population dynamics. Viral-mediated mortality may not only affect algal species succession, but may also affect intraspecies succession. Through cellular lysis, viruses indirectly affect the fluxes of energy, nutrients, and organic matter, especially during algal bloom events when biomass is high. Although the importance of viruses is presently recognized, it is apparent that many aspects of viral-mediated mortality of phytoplankton are still poorly understood. It is imperative that future research addresses the mechanisms that regulate virus infectivity, host resistance, genotype richness, abundance, and the fate of viruses over time and space. [source] A novel purification strategy for retrovirus gene therapy vectors using heparin affinity chromatographyBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2005María de las Mercedes Segura Abstract Membrane separation and chromatographic technologies are regarded as an attractive alternative to conventional academic small-scale ultracentrifugation procedures used for retrovirus purification. However, despite the increasing demands for purified retroviral vector preparations, new chromatography adsorbents with high specificity for the virus have not been reported. Heparin affinity chromatography is presented here as a novel convenient tool for retrovirus purification. The ability of bioactive retroviral particles to specifically bind to heparin ligands immobilized on a chromatographic gel is shown. A purification factor of 63 with a recovery of 61% of functional retroparticles was achieved using this single step. Tentacle heparin affinity supports captured retroviral particles more efficiently than conventional heparin affinity chromatography supports with which a lower recovery was obtained (18%). Intact, infective retroviral particles were recovered by elution with low salt concentrations (350 mM NaCl). Mild conditions for retrovirus elution from chromatographic columns are required to preserve virus infectivity. VSV-G pseudotyped retroviruses have shown to be very sensitive to high ionic strength, losing 50% of their activity and showing membrane damage after a short exposure to 1M NaCl. We also report a complete scaleable downstream processing scheme for the purification of MoMLV-derived vectors that involves sequential microfiltration and ultra/diafiltration steps for virus clarification and concentration respectively, followed by fractionation by heparin affinity chromatography and final polishing by size-exclusion chromatography. Overall, by using this strategy, a 38% yield of infective particles can be achieved with a final purification factor of 2,000. © 2005 Wiley Periodicals, Inc. [source] Structural Investigation of the HIV-1 Envelope Glycoprotein gp160 Cleavage Site 3: Role of Site-Specific Mutations,CHEMBIOCHEM, Issue 12 2004Lucia Falcigno Dr. Abstract Proteolytic processing of HIV gp160 to produce gp120 and gp41 is performed by PC enzymes. This process is a prerequisite for the virus infectivity, since both gp120 and gp41 participate in the virus HIV-1 entry mechanism. The structure of the gp120/gp41 junction remains to be elucidated, and the structural features required for molecular recognition between HIV-1 gp160 and proteolytic enzymes have not been clarified. Furin is the best PC candidate for the gp160 proteolytic processing known to date. In previous studies on model peptides, we have shown the relevance of an N-terminal helix for the proper recognition of the gp160 processing site by furin. Here we analyze the effect of point mutations in peptides lacking a regular N-terminal helix. To this end, we present the structure,activity characterization of three peptide analogues of the HIV gp160 processing site that all present mutations in proline at positions P3 and/or P2,, while sharing the same N-terminal sequence, containing helix-breaking D -amino acids. Conformational analysis of the peptides was carried out in solution by NMR techniques, and furin's efficiency in cleaving them was measured. Structural findings are presented and discussed in relation to the different exhibited activity. [source] | ||||||||||