Recombinant influenza virus with a pandemic H2N2 polymerase complex has a higher adaptive potential than one with seasonal H2N2 polymerase complex

Abstract

The reassortment of influenza viral gene segments plays a key role in the genesis of pandemic strains. All of the last three pandemic viruses contained reassorted polymerase complexes with subunits derived from animal viruses, suggesting that the acquisition of a reassorted polymerase complex might have a role in generating these pandemic viruses. Here, we studied polymerase activities of the pandemic H2N2, seasonal H2N2 and pandemic H3N2 viruses. We observed that the viral ribonucleoprotein (vRNP) of pandemic H2N2 virus has a highly robust activity. The polymerase activity of seasonal H2N2 viruses, however, was much reduced. We further identified three mutations (PB2-I114V, PB1-S261N and PA-D383N) responsible for the reduced activity. To determine the potential impact of viral polymerase activity on the viral life cycle, recombinant H3N2 viruses carrying pandemic and seasonal H2N2 vRNP were studied in cell cultures supplemented with oseltamivir carboxylate and tested for their abilities to develop adaptive or resistant mutations. It was found that the recombinant virus with pandemic H2N2 vRNP was more capable of restoring the viral fitness than the one with seasonal vRNP. These results suggest that a robust vRNP is advantageous to influenza virus to cope with a new selection pressure.

Evaluation of Multivalent Sialylated Polyglycerols for Resistance Induction in and Broad Antiviral Activity against Influenza A Viruses

“…Upon serial passaging with Oseltamivir, only variants harboring mutations in HA and not NA were selected here. It is well established that HA mutations decreasing receptor affinity can confer resistance to NA inhibitors without changes in NA activity in vitro . , G135E in H3 subtype HA found in the present study in particular has been previously described to confer resistance to Oseltamivir …”

“…Thus, the genetic barrier for influenza A/X31 virus to develop resistance by adaptive mutations in these positions appears to be relatively low. The early development of adaptive mutations observed here (Figure , Table ) is comparable to the development of resistance in influenza viruses to other substances, like amantadines, which developed within two to three passages, resistance against Oseltamivir in passage three, and resistance against Zanamivir as early as passage one …”

“…71,72 G135E in H3 subtype HA found in the present study in particular has been previously described to confer resistance to Oseltamivir. 93 Because the resistance mutations occurred around the RBS, we assessed putative changes in receptor binding by analysis with two glycan arrays (Figure 5): WT virus bound with high binding intensity to established receptors of A/X31 virus attachment. 85 In contrast, L1 and L2 bound only to some of the established receptors, with binding intensities reduced by 2 orders of magnitude, whereas no binding was detected for L3.…”