Genomic and antigenic analysis of G1P[8] rotavirus strains in Ningxia, China

Rotavirus A (RVA) genotype G1P[8] is epidemiologically significant and a major vaccine target. This study aimed to characterize the genetic features, evolutionary dynamics, and antigenic compatibility with current vaccine strains of G1P[8] RVA circulating in Ningxia, China, in order to assess its local epidemiological shifts and potential implications.

We conducted continuous surveillance in Ningxia from 2015 to 2023 on diarrheal outpatients from sentinel hospitals for foodborne disease monitoring, and from 2022 to 2024 on hospitalized children under 5 years of age with diarrhea from sentinel sites for viral diarrhea surveillance. RVA detection and G/P genotyping were performed using RT-PCR. Representative G1P[8] strains were selected for whole-genome sequencing, followed by bioinformatic analyses including antigenic epitope comparison, Bayesian evolutionary analysis, and phylogenetic reconstruction.

The overall RVA positivity rate during the surveillance period was 16.8%. However, G1P[8] was prevalent only in 2015-2016, accounting for 16.83% and 12.50% of cases, respectively. Its circulation declined sharply thereafter, with only one case detected in 2021. Whole-genome analysis revealed that all sequenced strains possessed a typical Wa-like genetic constellation (G1-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1). Antigenic epitope analysis identified multiple amino acid variations in key neutralizing sites of VP7 and VP4 proteins between Ningxia strains and vaccine strains. The VP7 of the 2021 strain showed the highest similarity to the Rotarix vaccine strain, while the VP4 of all Ningxia strains was most similar to that of the Rotavin-M1 vaccine. Evolutionary analysis indicated that the 2015-2016 strains and the 2021 strain belonged to distinct VP7 and VP4 lineages. Although the 2021 strain (20210516) exhibited a G1P[8] genotype, its remaining gene segments (VP1-VP3, VP6, NSP1-NSP5) clustered with G12 strains, suggesting its possible origin from a reassortment event between G12 and G1P[8] viruses. Compared with the contemporaneously reported Palermo 2021 variant from Italy, the Ningxia 20210516 strain showed closer phylogenetic relatedness only in certain gene segments (e.g., NSP5, VP1-VP2, VP4, VP7).

This study confirms that G1P[8] RVA prevalence in Ningxia remains low; however, novel variants arising from reassortment may still emerge locally, accompanied by changes in antigenicity and genetic background. Sustained genotype surveillance and whole-genome analysis of RVA are essential for tracking epidemiological trends, evaluating vaccine effectiveness, and informing prevention and control strategies.