Antiviral research
-
Using an in vivo ferret model, we investigated the development of resistance to oseltamivir and zanamivir for two different influenza A(H5N1) viruses (A/Vietnam/1203/2004, haemagglutinin phylogenetic clade 1, and A/Chicken/Laos/26/2006, haemagglutinin phylogenetic clade 2.3) by treating the animals with doses equivalent either to the recommended human treatment dose or a range of sub-optimal drug doses. No resistance was observed in oseltamivir-treated ferrets, but analysis of nasal washes from zanamivir-treated ferrets infected with influenza A/Vietnam/1203/2004 revealed one viral isolate (from a ferret receiving the highest dose of zanamivir, 1.0mg/kg twice daily) with a zanamivir IC(50) that was 350-fold higher than the other isolates tested. The same virus also demonstrated a 26-fold increase in oseltamivir IC(50). ⋯ Sequence analysis of the resistant virus revealed a glutamine (Q) to leucine (L) mutation at residue 136 of the neuraminidase. This is the first report of this mutation being associated with neuraminidase inhibitor susceptibility and one of the few reported mutations that confer zanamivir resistance, and as such should be closely monitored in influenza A(H5N1) and other N1 viruses in the future. Further animal studies and human clinical trials are necessary to optimize neuraminidase inhibitor dosing strategies for the treatment of influenza A(H5N1) infections.
-
In 2009 a new swine-origin influenza virus A/H1N1 (A/H1N1 09) emerged, causing the century's first pandemic. Most isolates of the new A/H1N1 09 virus are susceptible to neuraminidase inhibitors, but the H275Y mutation in the neuraminidase gene region associated with high-level oseltamivir resistance has been detected. Using rolling circle amplification (RCA) technology, 96 A/H1N1 09-specific RT-PCR positive clinical samples collected from 80 oseltamivir-treated and untreated patients were screened for the presence of the H275Y mutation. ⋯ RCA demonstrates the rapid emergence of the H275Y resistance mutation in individuals with severe A/H1N1 09 infection receiving neuraminidase inhibitors. Rapid detection of oseltamivir resistance in severe infection is essential for patients to receive maximum therapeutic benefit. In the light of emerging resistance, close monitoring and understanding of the nature and dynamics of resistance mutations in newly emerging strains should be a priority.
-
In the Netherlands, influenza specific antivirals are used for the therapy of influenza in nursing homes and hospitals, for prophylaxis in high risk groups and neuraminidase inhibitors are stockpiled as part of pandemic preparedness plans. To monitor the antiviral susceptibility profile, human influenza virus isolates derived from the Dutch influenza surveillance in 2005-2006 (n=87), 2006-2007 (n=58) and 2007-2008 (n=128) were analyzed with phenotypic assays and sequencing. ⋯ Furthermore, oseltamivir-resistant A(H1N1) or adamantane-resistant A(H3N2) virus infections were not associated with differences in clinical symptoms compared to infections with sensitive variants. Our data show the dynamic nature of emergence of drug-resistant influenza viruses, stressing the need for surveillance of resistance trends as part of influenza monitoring programs.
-
We report herein the identification of a small molecule therapeutic, FGI-106, which displays potent and broad-spectrum inhibition of lethal viral hemorrhagic fevers pathogens, including Ebola, Rift Valley and Dengue Fever viruses, in cell-based assays. Using mouse models of Ebola virus, we further demonstrate that FGI-106 can protect animals from an otherwise lethal infection when used either in a prophylactic or therapeutic setting. ⋯ Cell-based assays also identified inhibitory activity against divergent virus families, which supports a hypothesis that FGI-106 interferes with a common pathway utilized by different viruses. These findings suggest FGI-106 may provide an opportunity for targeting viral diseases.
-
In the beginning of 2007-2008 Northern Hemisphere influenza season, the frequency of influenza A(H1N1) viruses bearing a previously defined oseltamivir resistance conferring amino acid change of Histidine to Tyrosine at position 274 (H274Y) of the neuraminidase (NA) increased dramatically. In order to rapidly detect such resistant viruses, an RT-PCR/restriction fragment length polymorphism (RT-PCR/RFLP) assay targeting amino acid 274 of the N1 NA molecule was developed to investigate the presence or absence of the H274Y mutation. ⋯ The assay was specific for grown A(H1N1) viruses and original clinical specimens, with a lower limit of detection of approximately 10 RNA transcript copies per reaction. Our RT-PCR/RFLP assay provides a simple, rapid and sensitive tool to monitor the emergence and spread of H274Y oseltamivir-resistant influenza A(H1N1) viruses.