Molecular mutation features of influenza B viruses in Guangdong, 2020-2021

Abstract

Objective To learn the molecular characteristics of influenza B Victoria lineage (Bv) and evaluate the influenza B spread trend about the epidemic. Methods Based on the Guangdong Influenza Surveillance Networks (GDISN) to selected the Bv with space-time sampling, the nucleotide sequences of HA/NA genes were detected. The evolution and mutations of both genes were analyzed in homology with MEGA 7.026和SPSS 23.0, in evolutionary tree with neighbor-joining method, in selective evolution with Datamonkey 2.0. Results The nucleotide homologies of HA/NA genes in the 2021 strains were statistically different from these of the 2020's (P < 0.01), in which the those of HA genes in 17 strains isolated in the second half of 2021 were up to (99.28±0.25)% compared with these in the vaccine strain B/Austria/1359417/2021. As to HA genes, the epitope A (H137N/Q, A142T and R148G), B (P159L and N162K) and D (S209N/D and T211A) were mutated, therefore the 2020 and 2021 strains in Guangdong were respectively classified into Clade Bv.1a.3 and Bv.1a.3a.2. There were significantly no mutations in the potential glycosylation sites in HA/NA genes, as well in the NA known drug sensitive sites. Evolutionary selection conducted the negative selection sites in HA/NA genes, including amino acid sites 73, 138, 437 and 497 in HA and sites 179, 321 and 335 in NA. Conclusion Influenza Bv strains including HA and NA genes in Guangdong 2021 strain are significantly different from these of the 2020 strains, especially on HA genes in the second half of 2021.

Keywords

• influenza b
• influenza b victoria lineage
• evolution
• epitope
• negative selection