Oseltamivir–Resistant Pandemic H1N1/2009 Influenza Virus Possesses Lower Transmissibility and Fitness in Ferrets

Division of Virology, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
PLoS Pathogens (Impact Factor: 8.06). 07/2010; 6(7):e1001022. DOI: 10.1371/journal.ppat.1001022
Source: PubMed

ABSTRACT The neuraminidase (NA) inhibitor oseltamivir offers an important immediate option for the control of influenza, and its clinical use has increased substantially during the recent H1N1 pandemic. In view of the high prevalence of oseltamivir-resistant seasonal H1N1 influenza viruses in 2007-2008, there is an urgent need to characterize the transmissibility and fitness of oseltamivir-resistant H1N1/2009 viruses, although resistant variants have been isolated at a low rate. Here we studied the transmissibility of a closely matched pair of pandemic H1N1/2009 clinical isolates, one oseltamivir-sensitive and one resistant, in the ferret model. The resistant H275Y mutant was derived from a patient on oseltamivir prophylaxis and was the first oseltamivir-resistant isolate of the pandemic virus. Full genome sequencing revealed that the pair of viruses differed only at NA amino acid position 275. We found that the oseltamivir-resistant H1N1/2009 virus was not transmitted efficiently in ferrets via respiratory droplets (0/2), while it retained efficient transmission via direct contact (2/2). The sensitive H1N1/2009 virus was efficiently transmitted via both routes (2/2 and 1/2, respectively). The wild-type H1N1/2009 and the resistant mutant appeared to cause a similar disease course in ferrets without apparent attenuation of clinical signs. We compared viral fitness within the host by co-infecting a ferret with oseltamivir-sensitive and -resistant H1N1/2009 viruses and found that the resistant virus showed less growth capability (fitness). The NA of the resistant virus showed reduced substrate-binding affinity and catalytic activity in vitro and delayed initial growth in MDCK and MDCK-SIAT1 cells. These findings may in part explain its less efficient transmission. The fact that the oseltamivir-resistant H1N1/2009 virus retained efficient transmission through direct contact underlines the necessity of continuous monitoring of drug resistance and characterization of possible evolving viral proteins during the pandemic.


Available from: David Boltz, May 30, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Influenza transmission efficiency in ferrets is vital for risk-assessment studies. However, the inability to monitor viral infection and transmission dynamics in real time only provides a glimpse into transmissibility. Here we exploit a replication-competent influenza reporter virus to investigate dynamics of infection/transmission in ferrets. Bioluminescent imaging of ferrets infected with A/California/04/2009 H1N1 virus (CA/09) encoding NanoLuc (NLuc) luciferase provides the first real-time snapshot of influenza infection/transmission. Luminescence in the respiratory tract and in less well-characterized extra-pulmonary sites is observed, and imaging identifies infections in animals that would have otherwise been missed by traditional methods. Finally, the reporter virus significantly increases the speed and sensitivity of virological and serological assays. Thus, bioluminescent imaging of influenza infections rapidly determines intra-host dissemination, inter-host transmission and viral load, revealing infection dynamics and pandemic potential of the virus. These results have important implications for antiviral drug susceptibility, vaccine efficacy, transmissibility and pathogenicity studies.
    Nature Communications 03/2015; 6:6378. DOI:10.1038/ncomms7378 · 10.74 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We propose a simple two-disease epidemic model where one disease exhibits only a drug-sensitive strain, while the other exhibits both drug-sensitive and drug-resistant strains. Treatment for the first disease may select for resistance in the other. We model antibiotic use as a mathematical game through the study of individual incentives and community welfare. The basic reproduction number is derived and the existence and local stability of the model equilibria are analyzed. When the force of infection of each disease is unaffected by the presence of the other, we find that there is a conflict of interest between individual and community, known as a tragedy of the commons, under targeted treatment towards persons infected by the single strain disease, but there is no conflict under mass treatment. However, we numerically show that individual and social incentive to use antibiotics may show disaccord under mass treatment if the restriction on the transmission ability of the dually infected people is removed, or drug resistant infection is worse than drug sensitive infection, or the uninfected state has a comparative disutility over the infected states. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
    Mathematical Biosciences 02/2015; 16. DOI:10.1016/j.mbs.2015.02.007 · 1.49 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Oseltamivir-resistant H1N1 influenza viruses carrying the H275Y neuraminidase mutation predominated worldwide during the 2007-2009 seasons. Although several neuraminidase substitutions were found to be necessary to counteract the adverse effects of H275Y, the order and impact of evolutionary events involved remain elusive. Here we reconstruct H1N1 neuraminidase phylogeny during 1999-2009, estimate the timing and order of crucial amino acid changes and evaluate their impact on the biological outcome of the H275Y mutation. Of the 12 neuraminidase substitutions that occurred during 1999-2009, 5 (chronologically, V234M, R222Q, K329E, D344N, H275Y and D354G) are necessary for maintaining full neuraminidase function in the presence of the H275Y mutation by altering protein accumulation or enzyme affinity/activity. The sequential emergence and cumulative effects of these mutations clearly illustrate a role for epistasis in shaping the emergence and subsequent evolution of a drug-resistant virus population, which can be useful in understanding emergence of novel viral phenotypes of influenza.
    Nature Communications 01/2014; 5:5029. DOI:10.1038/ncomms6029 · 10.74 Impact Factor