Background: The neuraminidase (NA) inhibitor oseltamivir is widely used to treat patients infected with influenza viruses. An Ile-to-Val change at position 117 in influenza A virus subtype H5N1 NA (NA-I117V) confers a reduction in susceptibility to oseltamivir carboxylate. However, the in vivo relevance and molecular basis of the decreased sensitivity mediated by this mutation are poorly understood.

Methods: We created single-point-mutant viruses with 3 genetically different backgrounds (ie, 1 belonging to clade 1 and 2 belonging to clade 2.3.4) and evaluated the effects of the I117V mutation on oseltamivir susceptibility in vitro, in vivo, and in silico.

Results: The NA-I117V mutation conferred a slight reduction in susceptibility to oseltamivir in vitro (1.3- to 6.3-fold changes), although it did not substantially compromise NA enzymatic activity. Mice infected with I117V virus exhibited reduced susceptibility to oseltamivir and decreased survival in 2 of 3 virus pairs tested. Molecular dynamics simulations revealed that I117V caused the loss of hydrogen bonds between an arginine at position 118 and the carboxyl group of oseltamivir, leading to a lower binding affinity for oseltamivir.

Conclusions: Our findings provide new insight into the mechanism of NA-I117V-mediated oseltamivir resistance in highly pathogenic H5N1 avian influenza viruses.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3571237PMC
http://dx.doi.org/10.1093/infdis/jis633DOI Listing

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