Molecular mechanisms underlying oseltamivir resistance mediated by an I117V substitution in the neuraminidase of subtype H5N1 avian influenza A viruses.
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.
Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
Ryo
R
Takano
Maki
M
Kiso
Manabu
M
Igarashi
Quynh Mai
QM
Le
Masakazu
M
Sekijima
Kimihito
K
Ito
Ayato
A
Takada
Yoshihiro
Y
Kawaoka
D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001717:Birds; D024882:Drug Resistance, Viral / Q000235:genetics*; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D005260:Female; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D005585:Influenza in Birds / Q000188:drug therapy / Q000821:virology; D007251:Influenza, Human / Q000188:drug therapy / Q000821:virology; D051379:Mice; D008807:Mice, Inbred BALB C; D056004:Molecular Dynamics Simulation; D009439:Neuraminidase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D009976:Orthomyxoviridae Infections / Q000188:drug therapy / Q000821:virology*; D053139:Oseltamivir / Q000494:pharmacology* / Q000627:therapeutic use; D017354:Point Mutation; D011200:Poultry; D014764:Viral Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D014779:Virus Replication
D000998:Antiviral Agents; D004791:Enzyme Inhibitors; D014764:Viral Proteins; D053139:Oseltamivir; D009439:Neuraminidase