Phylogenetic Analysis of Noroviruses Based on RNA-Dependent RNA Polymerase GII.P16 Gene Sequences

Noroviruses with the GII.P16 polymerase gene have long been considered rare. However, since 2015, there have been reports from different geographical regions about the spread of new recombinant strains of norovirus in which GII.P16 polymerase is associated with a capsid protein of various genotypes. In the autumn of 2016, a sharp increase in the frequency of detection of noroviruses was observed in Nizhny Novgorod, which coincided with the appearance of new recombinants GII.4_Sydney and GII.2 – with GII.P16 polymerase. Based on the sequences of the RNA-dependent RNA polymerase gene present in the GenBank database, a phylogenetic analysis of noroviruses with GII.P16 specificity was performed by constructing Bayesian phylogenetic trees. Analysis of amino acid sequences showed that representatives of the novel variant of the GII.P16 polymerase gene had five substitutions compared to earlier strains. These substitutions are located near sites responsible for the enzyme activity of polymerase and could affect the transmissivity of the virus. Acquisition of a novel variant of the GII.P16 polymerase gene by noroviruses with different capsid protein genotypes probably provides certain advantages for recombinants and creates prerequisites for their wide distribution.