Oseltamivir-Resistant Pandemic A/H1N1 Virus Is as Virulent as Its Wild-Type Counterpart in Mice and Ferrets

Abstract

The neuraminidase inhibitor oseltamivir is currently used for treatment of patients infected with the pandemic A/H1N1 (pH1N1) influenza virus, although drug-resistant mutants can emerge rapidly and possibly be transmitted. We describe the characteristics of a pair of oseltamivir-resistant and oseltamivir-susceptible pH1N1 clinical isolates that differed by a single change (H274Y) in the neuraminidase protein. Viral fitness of pH1N1 isolates was assessed in vitro by determining replication kinetics in MDCK α2,6 cells and in vivo by performing experimental infections of BALB/c mice and ferrets. Despite slightly reduced propagation of the mutant isolate in vitro during the first 24 h, the wild-type (WT) and mutant resistant viruses induced similar maximum weight loss in mice and ferrets with an identical pyrexic response in ferrets (AUC of 233.9 and 233.2, P = 0.5156). Similarly, comparable titers were obtained for the WT and the mutant strains on days 1, 3, 6 and 9 post-infection in mouse lungs and on days 1–7 in ferret nasal washes. A more important perivascular (day 6) and pleural (days 6 and 12) inflammation was noted in the lungs of mice infected with the H274Y mutant, which correlated with increased pulmonary levels of IL-6 and KC. Such increased levels of IL-6 were also observed in lymph nodes of ferrets infected with the mutant strain. Furthermore, the H274Y mutant strain was transmitted to ferrets. In conclusion, viral fitness of the H274Y pH1N1 isolate is not substantially altered and has the potential to induce severe disease and to disseminate.

The E119D neuraminidase mutation identified in a multidrug-resistant influenza A(H1N1)pdm09 isolate severely alters viral fitness in vitro and in animal models

“…Interestingly, our group and other investigators reported that A(H1N1)pdm09 H275Y variants conserved a good fitness and exhibited efficient contact transmission when assessed in ferrets and guinea pigs (Hamelin et al, 2010;Memoli et al, 2011;Seibert et al, 2010;Wong et al, 2012). Furthermore, we previously demonstrated that the A(H1N1)pdm09 H275Y mutant was at least as virulent as the WT virus in BALB/c (Hamelin et al, 2010) and C57BL/6 mice. At this time, little information is available regarding the fitness and virulence of zanamivir-resistant A(H1N1)pdm09 viruses.…”

“…Such variants are also resistant to peramivir but retain susceptibility to zanamivir and laninamivir (Pizzorno et al, 2011;Samson et al, 2014). Interestingly, our group and other investigators reported that A(H1N1)pdm09 H275Y variants conserved a good fitness and exhibited efficient contact transmission when assessed in ferrets and guinea pigs (Hamelin et al, 2010;Memoli et al, 2011;Seibert et al, 2010;Wong et al, 2012). Furthermore, we previously demonstrated that the A(H1N1)pdm09 H275Y mutant was at least as virulent as the WT virus in BALB/c (Hamelin et al, 2010) and C57BL/6 mice.…”

The H275Y Neuraminidase Mutation of the Pandemic A/H1N1 Influenza Virus Lengthens the Eclipse Phase and Reduces Viral Output of Infected Cells, Potentially Compromising Fitness in Ferrets

“…Unlike the growth of pre-2007 seasonal H1N1 strains, that of the H1N1pdm09 H275Y MUT (H1N1pdm09-MUT) strain is not severely compromised in vitro or in ferrets (9,12,15,31). Contact transmissions of H1N1pdm09-MUT between ferrets have been successful in all of the experiments reported (15,16,35,38,45).…”

Fast High-Throughput Screening of H1N1 Virus by Parallel Detection with Multichannel Microchip Electrophoresis

“…[6][7][8] In addition, by using specific primers and probes, the different subtypes of influenza A can be discriminated. [6][7][8][9][10] However, current PCR methods continue to rely heavily on slab gel electrophoresis (SGE) analysis, which requires several hours to obtain results and is extremely low-throughput, making this technique unsuitable for a large number of samples. 11 Even though real-time PCR (RT-PCR) methods may decrease analysis time, they require special thermo-cyclers equipped with an expensive and sensitive camera and well-designed primers.…”