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Mutant Viruses (mutant + viruse)

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Medical Sciences	100%

Selected Abstracts

Influenza A viruses with truncated NS1 as modified live virus vaccines: Pilot studies of safety and efficacy in horses

EQUINE VETERINARY JOURNAL, Issue 1 2009
T. M. Chambers
Summary Reasons for performing study: Three previously described NS1 mutant equine influenza viruses encoding carboxyterminally truncated NS1 proteins are impaired in their ability to inhibit type I IFN production in vitro and are replication attenuated, and thus are candidates for use as a modified live influenza virus vaccine in the horse. Hypothesis: One or more of these mutant viruses is safe when administered to horses, and recipient horses when challenged with wild-type influenza have reduced physiological and virological correlates of disease. Methods: Vaccination and challenge studies were done in horses, with measurement of pyrexia, clinical signs, virus shedding and systemic proinflammatory cytokines. Results: Aerosol or intranasal inoculation of horses with the viruses produced no adverse effects. Seronegative horses inoculated with the NS1-73 and NS1-126 viruses, but not the NS1-99 virus, shed detectable virus and generated significant levels of antibodies. Following challenge with wild-type influenza, horses vaccinated with NS1-126 virus did not develop fever (>38.5°C), had significantly fewer clinical signs of illness and significantly reduced quantities of virus excreted for a shorter duration post challenge compared to unvaccinated controls. Mean levels of proinflammatory cytokines IL-1, and IL-6 were significantly higher in control animals, and were positively correlated with peak viral shedding and pyrexia on Day +2 post challenge. Conclusion and clinical relevance: These data suggest that the recombinant NS1 viruses are safe and effective as modified live virus vaccines against equine influenza. This type of reverse genetics-based vaccine can be easily updated by exchanging viral surface antigens to combat the problem of antigenic drift in influenza viruses. [source]

Effect of the G1896A precore mutation on drug sensitivity and replication yield of lamivudine-resistant HBV in vitro

HEPATOLOGY, Issue 1 2003
Robert Y. M. Chen
Hepatitis B e antigen (HBeAg) negative chronic hepatitis B (CHB) is frequently caused by a mutation (G1896A) in the hepatitis B virus (HBV) precore (PC) reading frame that creates a stop codon, causing premature termination of the PC protein. During lamivudine treatment, drug resistance develops at a similar rate in HBeAg positive and HBeAg negative CHB. Lamivudine-resistant HBV mutants have been shown to replicate inefficiently in vitro in the absence of PC mutations, but it is unknown whether the presence of PC mutations affects replication efficiency or antiviral sensitivity. This study utilized the recombinant HBV baculovirus system to address these issues. HBV baculoviruses encoding the G1896A PC stop codon mutation were generated in wild-type (WT) and lamivudine-resistant (rtM204I and rtL180M + rtM204V) backgrounds, resulting in a panel of 6 related recombinant baculoviruses. In vitro assays were performed to compare the sensitivities of the PC mutant viruses with lamivudine and adefovir and to compare relative replication yields. The PC mutation did not significantly affect sensitivities to either adefovir or lamivudine. WT HBV and PC mutant HBV showed similar replication yields, whereas the replication yields of the lamivudine-resistant mutants were greatly reduced in HBeAg positive HBVs, confirming previous observations. However, the presence of the PC mutation was found to compensate for the replication deficiency in each of the lamivudine-resistant mutants, increasing the replication yields of each virus. In conclusion, the PC stop codon mutation appears to increase the replication efficacy of lamivudine-resistant virus but does not affect in vitro drug sensitivity. [source]

Effects of lamivudine on outcome after liver resection for hepatocellular carcinoma in patients with active replication of hepatitis B virus

HEPATOLOGY RESEARCH, Issue 2 2007
Shoji Kubo
Aim:, Patients with high serum hepatitis B virus (HBV) DNA concentrations are at high risk of tumor recurrence after liver resection for HBV-related hepatocellular carcinoma (HCC). Methods:, Among 24 patients with high serum HBV DNA concentrations who underwent liver resection for HBV-related HCC, postoperative lamivudine therapy was chosen by 14 (lamivudine group). The other 10 patients were controls. Results:, Clinicopathologic findings did not differ between the groups. Tumor-free survival rate after surgery was significantly higher in the lamivudine than the control group (P = 0.0086). By univariate analysis, multiple tumors were also a risk factor for a short tumor-free survival. By multivariate analysis, lack of lamivudine therapy and multiple tumors were independent risk factors for a short tumor-free survival. In four patients YMDD mutant viruses were detected after beginning lamivudine administration; in two of them, adefovir dipivoxil was administered because of sustained serum alanine aminotransferase elevations. Conclusion:, Lamivudine therapy improved tumor-free survival rate after curative resection of HBV-related HCC in patients with high serum concentrations of HBV DNA, although careful follow up proved necessary for the detection of YMDD mutant viruses. [source]

Establishment and recall of CD8+ T-cell memory in a model of localized transient infection

IMMUNOLOGICAL REVIEWS, Issue 1 2006
Katherine Kedzierska
Summary:, The influenza A virus model of localized, transient respiratory infection provides a well-defined experimental system for dissecting the induction and maintenance of CD8+ T-cell memory. This review focuses on quantitative and qualitative aspects of the prominent DbNP366 - and DbPA224 -specific CD8+ T-cell responses in virus-infected B6 mice. The different virus-specific effector and memory sets are compared by phenotypic [CD62L, interleukin-7 receptor-, (IL-7R,), and IL-15R, expression] and functional [interferon-, (IFN-,), tumor necrosis factor-, (TNF-,), and IL-2 production] analyses. Most clonotypes [defined by T-cell receptor (TCR) CDR3, sequence] generated during the acute phase of infection survive into memory, with those expressing the more consensus ,canonical' TCRs being the major contributors to the recall response. The extent of clonal expansion and the size of memory CD8+ T-cell populations has been characterized for mice challenged with either wildtype or mutant viruses, where broadly equivalent DbNP366 and DbPA224 expression was achieved by disabling the peptides in their native configuration, then expressing them in the viral neuraminidase protein. Combining the clonotypic and antigen dose analyses led to a somewhat mechanistic conclusion that the magnitude of any virus-specific CD8+ T-cell response will be a direct function of antigen dose and the size of the naïve or memory CD8+ T-cell precursor pool. [source]