Isolation, Genomic Characterization, and Immunogenicity Evaluation of a G9P[23] Porcine Rotavirus Strain

(1) Background: Rotavirus (RV) is the primary pathogen causing diarrhea in infants and young children. The G9-type is an emerging genotype; however, its isolation is challenging, and its immunogenicity to piglets is poorly understood. This study aimed to isolate, characterize, and evaluate the immunogenicity of a PoRVA strain, RHeN2, obtained from the diarrhea samples of piglets from a pig farm in Henan Province, China. (2) Methods: Porcine rotavirus A (PoRVA) was isolated from diarrheal samples of piglets on a farm in Henan Province, China, through sequential passaging on MA-104 cells. Its immunogenicity and cross-neutralization potential were evaluated. Inactivated vaccines were prepared using two agents (formaldehyde and binary ethyleneimine, BEI) and administered intramuscularly to 28-day-old piglets. Dulbecco's Modified Eagle Medium (DMEM) served as the control. (3) Results: A PoRVA strain, G9P[23] type, was successfully isolated and named RHeN2. Full-genome Sanger sequencing revealed the genetic constellation of this strain as G9-P[23]-I5-R1-C1- M1-A8-N1-T1-E1-H1. In addition, the titers of neutralizing antibodies peaked at 45 days post-vaccination, and the immunogenicity of the BEI-inactivated group of vaccines was better than that of the formaldehyde-inactivated group. The RHeN2 (G9P[23]) strain demonstrated a strong cross-neutralization ability against the same G9P[23] and G4P[23] strains and a stronger cross-neutralizing ability against the P[23] strains than against the P[7] strains. (4) Conclusion: The newly isolated G9P[23] strain demonstrates favorable immunogenicity, holding potential as a G9-type vaccine candidate.