Correlation between the receptor specificity of pandemic influenza a (H1N1)pdm09 virus strains isolated in 2009-2011 and the structure of the receptor-binding site and the probability of fatal primary viral pneumonia

The receptor specificity (RS) of pandemic influenza A(H1N1) pdm09 virus strains deposited into the State Collection of Viruses of the Russian Federation, D. I. Ivanovsky Research Institute of Virology, Ministry of Health and Social Development of Russia, in the 2009-2010 and 2010-2011 epidemic seasons to a panel of 9 sialoglycopolymers (SGP). The strains were divided into 3 groups according to the W(3/6) index proposed by the authors, which was equal to the amount of reactivities to unbranched alpha2-3-SGP to that of reactivities to unbranched alphal-6-SGP: W(3/6)or = 1.0; 1.0W(3/6)or = 1.5. The W(3/6)or = 1.5 group showed a predominance of a2-3-RS, attended by the high incidence of fatal primary viral pneumonias (FPVP) (60.0%) and amino acid replacements in the HA1 receptor-binding site (RBS) (80.0%): D222{G, N} and Q223R. The 1.0W(3/6)or = 1.5 group was characterized by mixed alpha2-3/alpha2-6-RS with the incidence of FPVP (29.7%) and amino acid replacements in the HA1 RBS (40.5%) (D222{G, N, V} and Q223), respectively. In the W(3/6)or = 1.0 group, alpha2-6-RS was prevalent, FPVPs were absent and amino acid replacements in HA1 RBS (D222{G, E}) were seen only in 6.0% of cases. The number of strains with increased specificity to alpha2-3-sialosides increased in the 2010-2011 epidemic season as compared to the previous season. With their further spread among the population, there may be a rise in cases of severe primary viral pneumonias with possible fatal outcomes, which can be, however, accompanied by a decrease in the capacity of mutants to air-dropwise transmission.