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Novel genotyping and quantitative analysis of neuraminidase inhibitor resistance-associated mutations in influenza a viruses by single-nucleotide polymorphism analysis.

ABSTRACT: Neuraminidase (NA) inhibitors are among the first line of defense against influenza virus infection. With the increased worldwide use of the drugs, antiviral susceptibility surveillance is increasingly important for effective clinical management and for public health epidemiology. Effective monitoring requires effective resistance detection methods. We have developed and validated a novel genotyping method for rapid detection of established NA inhibitor resistance markers in influenza viruses by single nucleotide polymorphism (SNP) analysis. The multi- or monoplex SNP analysis based on single nucleotide extension assays was developed to detect NA mutations H275Y and I223R/V in pandemic H1N1 viruses, H275Y in seasonal H1N1 viruses, E119V and R292K in seasonal H3N2 viruses, and H275Y and N295S in H5N1 viruses. The SNP analysis demonstrated high sensitivity for low-content NA amplicons (0.1 to 1 ng/?l) and showed 100% accordant results against a panel of defined clinical isolates. The monoplex assays for the H275Y NA mutation allowed precise and accurate quantification of the proportions of wild-type and mutant genotypes in virus mixtures (5% to 10% discrimination), with results comparable to those of pyrosequencing. The SNP analysis revealed the lower growth fitness of an H275Y mutant compared to the wild-type pandemic H1N1 virus by quantitatively genotyping progeny viruses grown in normal human bronchial epithelial cells. This novel method offers high-throughput screening capacity, relatively low costs, and the wide availability of the necessary equipment, and thus it could provide a much-needed approach for genotypic screening of NA inhibitor resistance in influenza viruses.

SUBMITTER: Duan S

PROVIDER: S-EPMC3187000 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature

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Novel genotyping and quantitative analysis of neuraminidase inhibitor resistance-associated mutations in influenza a viruses by single-nucleotide polymorphism analysis.

Duan Susu S Boltz David A DA Li Jiang J Oshansky Christine M CM Marjuki Henju H Barman Subrata S Webby Richard J RJ Webster Robert G RG Govorkova Elena A EA

Antimicrobial agents and chemotherapy 20110705 10

Neuraminidase (NA) inhibitors are among the first line of defense against influenza virus infection. With the increased worldwide use of the drugs, antiviral susceptibility surveillance is increasingly important for effective clinical management and for public health epidemiology. Effective monitoring requires effective resistance detection methods. We have developed and validated a novel genotyping method for rapid detection of established NA inhibitor resistance markers in influenza viruses by ...[more]

PMID: 21730113

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Project description:Currently, two neuraminidase (NA) inhibitors, oseltamivir and zanamivir, which must be administrated twice daily for 5 days for maximum therapeutic effect, are licensed for the treatment of influenza. However, oseltamivir-resistant mutants of seasonal H1N1 and highly pathogenic H5N1 avian influenza A viruses have emerged. Therefore, alternative antiviral agents are needed. Recently, a new neuraminidase inhibitor, R-125489, and its prodrug, CS-8958, have been developed. CS-8958 functions as a long-acting NA inhibitor in vivo (mice) and is efficacious against seasonal influenza strains following a single intranasal dose. Here, we tested the efficacy of this compound against H5N1 influenza viruses, which have spread across several continents and caused epidemics with high morbidity and mortality. We demonstrated that R-125489 interferes with the NA activity of H5N1 viruses, including oseltamivir-resistant and different clade strains. A single dose of CS-8958 (1,500 microg/kg) given to mice 2 h post-infection with H5N1 influenza viruses produced a higher survival rate than did continuous five-day administration of oseltamivir (50 mg/kg twice daily). Virus titers in lungs and brain were substantially lower in infected mice treated with a single dose of CS-8958 than in those treated with the five-day course of oseltamivir. CS-8958 was also highly efficacious against highly pathogenic H5N1 influenza virus and oseltamivir-resistant variants. A single dose of CS-8958 given seven days prior to virus infection also protected mice against H5N1 virus lethal infection. To evaluate the improved efficacy of CS-8958 over oseltamivir, the binding stability of R-125489 to various subtypes of influenza virus was assessed and compared with that of other NA inhibitors. We found that R-125489 bound to NA more tightly than did any other NA inhibitor tested. Our results indicate that CS-8958 is highly effective for the treatment and prophylaxis of infection with H5N1 influenza viruses, including oseltamivir-resistant mutants.

Project description:Neuraminidase (NA) mutations conferring resistance to NA inhibitors were believed to compromise influenza virus fitness. Unexpectedly, an oseltamivir-resistant A/Brisbane/59/2007 (Bris07)-like H1N1 H275Y NA variant emerged in 2007 and completely replaced the wild-type (WT) strain in 2008-2009. The NA of such variant contained additional NA changes (R222Q, V234M and D344N) that potentially counteracted the detrimental effect of the H275Y mutation on viral fitness. Here, we rescued a recombinant Bris07-like WT virus and 4 NA mutants/revertants (H275Y, H275Y/Q222R, H275Y/M234V and H275Y/N344D) and characterized them in vitro and in ferrets. A fluorometric-based NA assay was used to determine Vmax and Km values. Replicative capacities were evaluated by yield assays in ST6Gal1-MDCK cells. Recombinant NA proteins were expressed in 293T cells and surface NA activity was determined. Infectivity and contact transmission experiments were evaluated for the WT, H275Y and H275Y/Q222R recombinants in ferrets. The H275Y mutation did not significantly alter Km and Vmax values compared to WT. The H275Y/N344D mutant had a reduced affinity (Km of 50 vs 12 µM) whereas the H275Y/M234V mutant had a reduced activity (22 vs 28 U/sec). In contrast, the H275Y/Q222R mutant showed a significant decrease of both affinity (40 µM) and activity (7 U/sec). The WT, H275Y, H275Y/M234V and H275Y/N344D recombinants had comparable replicative capacities contrasting with H275Y/Q222R mutant whose viral titers were significantly reduced. All studied mutations reduced the cell surface NA activity compared to WT with the maximum reduction being obtained for the H275Y/Q222R mutant. Comparable infectivity and transmissibility were seen between the WT and the H275Y mutant in ferrets whereas the H275Y/Q222R mutant was associated with significantly lower lung viral titers. In conclusion, the Q222R reversion mutation compromised Bris07-like H1N1 virus in vitro and in vivo. Thus, the R222Q NA mutation present in the WT virus may have facilitated the emergence of NAI-resistant Bris07 variants.

Project description:Several subtypes of avian influenza viruses (AIVs) are emerging as novel human pathogens, and the frequency of related infections has increased in recent years. Although neuraminidase (NA) inhibitors (NAIs) are the only class of antiviral drugs available for therapeutic intervention for AIV-infected patients, studies on NAI resistance among AIVs have been limited, and markers of resistance are poorly understood. Previously, we identified unique NAI resistance substitutions in AIVs of the N3, N7, and N9 NA subtypes. Here, we report profiles of NA substitutions that confer NAI resistance in AIVs of the N4, N5, N6, and N8 NA subtypes using gene-fragmented random mutagenesis. We generated libraries of mutant influenza viruses using reverse genetics (RG) and selected resistant variants in the presence of the NAIs oseltamivir carboxylate and zanamivir in MDCK cells. In addition, two substitutions, H274Y and R292K (N2 numbering), were introduced into each NA gene for comparison. We identified 37 amino acid substitutions within the NA gene, 16 of which (4 in N4, 4 in N5, 4 in N6, and 4 in N8) conferred resistance to NAIs (oseltamivir carboxylate, zanamivir, or peramivir) as determined using a fluorescence-based NA inhibition assay. Substitutions conferring NAI resistance were mainly categorized as either novel NA subtype specific (G/N147V/I, A246V, and I427L) or previously reported in other subtypes (E119A/D/V, Q136K, E276D, R292K, and R371K). Our results demonstrate that each NA subtype possesses unique NAI resistance markers, and knowledge of these substitutions in AIVs is important in facilitating antiviral susceptibility monitoring of NAI resistance in AIVs.IMPORTANCE The frequency of human infections with avian influenza viruses (AIVs) has increased in recent years. Despite the availability of vaccines, neuraminidase inhibitors (NAIs), as the only available class of drugs for AIVs in humans, have been constantly used for treatment, leading to the inevitable emergence of drug-resistant variants. To screen for substitutions conferring NAI resistance in AIVs of N4, N5, N6, and N8 NA subtypes, random mutations within the target gene were generated, and resistant viruses were selected from mutant libraries in the presence of individual drugs. We identified 16 NA substitutions conferring NAI resistance in the tested AIV subtypes; some are novel and subtype specific, and others have been previously reported in other subtypes. Our findings will contribute to an increased and more comprehensive understanding of the mechanisms of NAI-induced inhibition of influenza virus and help lead to the development of drugs that bind to alternative interaction motifs.

Dataset Information

Novel genotyping and quantitative analysis of neuraminidase inhibitor resistance-associated mutations in influenza a viruses by single-nucleotide polymorphism analysis.

Publications

Novel genotyping and quantitative analysis of neuraminidase inhibitor resistance-associated mutations in influenza a viruses by single-nucleotide polymorphism analysis.

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