Gene characterization of human rotavirus strains VP7, VP4 and NSP4 in Tianjin, 2018-2020.

Objectives To identify VP7, VP4 and NSP4 genotypes and analyze their sequence characterization of group A rotavirus (RVA) strains prevalent in Tianjin. Methods The fecal samples of patients suffered from RVA-positive cases of acute diarrhea in Tianjin during 2018-2020 were collected and viral RNA were extracted. VP7, VP4 and NSP4 gene fragments were amplified by RT-PCR and PCR products were sequenced to analysis phylogenetic tree. Results The genotyping results showed that all RVA prevalent in Tianjing (TJ) strains in this study were G9P[8]. Phylogenetic analysis confirmed that VP7 and VP4 belonged to lineages G9-VI and P[8]-3. Phylogenetic analysis of NSP4 confirmed that 19 RVAs belonged to E1 and 12 RVAs belonged to E2. Comparison with vaccine strains and international epidemic strains showed VP7, VP4 and NSP4 genes of TJ strains had amino acid substitution at key sites. Thirty-one TJ-VP7 amino acid sequences were found with 4 and 3 substitution sites each compared to Rotavac G9 and Rotasiil G9. Six and three amino acid differences were found for thirty-one TJ-VP8* nucleotide sequences each compared with Rotarix P[8]-1 and RotaTeq. Compared with the two vaccines, only one amino acid site variation of TJ-VP5* was found in I388L of 5-1 region of RotaTeq, and the other 11 amino acid sites were highly conserved, while the amino acid sequence of the Rotarix 5-1 to 5-5 region is identical. Compared with the vaccine strain, TJ-E1 strain had 2 and 3 amino acid mutations in ASI and ASII regions, respectively; TJ E2 strain had 3, 8, 2, and 5 amino acid substitutions in ASI-ASIV, respectively, compared to the NSP4 sequence of the vaccine strain. 19 G9P[8]-E1 and 12 G9P[8]-E2 were detected in Tianjin from 2018 to 2020, which is the first time a G9P[8]-E2 reassortant (IGR) strains was found in Tianjin. Conclution Compared to the same genotypic vaccines strains and epidemic strains, the effect of amino acids variations located in VP7,VP4 and NSP4 epitope regions of TJ strains on the protective efficacy of the vaccine needs to be further investigated. Continued monitoring of rotavirus molecular mutation and recombination phenomena is needed, not only for G\P typing, but also for consideration of multi-gene fragment co-analysis and whole genome sequencing, in order to grasp the recombination and recombination of rotavirus. [ABSTRACT FROM AUTHOR]