Molecular mechanism of the enhanced viral fitness contributed by secondary mutations in the hemagglutinin protein of oseltamivir resistant H1N1 influenza viruses: Modeling studies of antibody and receptor binding

• Effects of compensatory mutations in the HA protein of influenza A H1N1 were studied.
• CH65 docking to HA showed that R192K mutation could have mediated antibody escape.
• R192K mutation also resulted in decreased binding of HA to sialic acid receptor.
• K144E mutation affected surface accessibility and electrostatic charge distribution.
• The study suggests the basis of enhanced viral fitness in oseltamivir-resistant H1N1 strains.

The envelope protein hemagglutinin (HA) of influenza viruses is primarily associated with host antibody and receptor interactions. The HA protein is known to maintain a functional balance with neuraminidase (NA), the other major envelope protein. Prior to 2007–2008, human seasonal H1N1 viruses possessing the NA H274Y mutation, which confers oseltamivir resistance, generally had low growth capability. Subsequently, secondary mutations that compensate for the deleterious effect of the NA H274Y mutation have been identified. The molecular mechanism of how the defect could be counteracted by these secondary mutations is not fully understood. We studied here the effect of three such mutations (T86K, K144E and R192K) in the HA protein, which are located at either the HA receptor binding site or in the H1N1 antigenic sites. Molecular docking and dynamics studies showed that, of the three mutations, the R192K mutation could have mediated neutralizing antibody escape and decreased receptor binding affinity, either or both of which may have contributed to increased viral fitness. The study suggests the molecular basis of enhanced viral fitness induced by secondary mutations in the evolution of oseltamivir-resistant influenza strains.