Isolation, propagation, and characterization of a G9P[4] human rotavirus strain 543765 in Iran

Group A rotavirus (RVA) is a leading etiological agent of diarrheal diseases in children less than 5 years of age. While live attenuated RV vaccines have demonstrated high efficacy in high-income countries (HICs), their performance is substantially reduced in low- and middle-income countries (LMICs). Despite this disparity, the development and evaluation of live attenuated RVA strains remain a central objective in RV vaccine research. In this study, a human RVA strain, designated 543765, was successfully isolated from a stool sample using MA104 cell culture. The isolate was characterized through observation of cytopathic effects (CPE), polyacrylamide gel electrophoresis (PAGE), reverse transcription-polymerase chain reaction (RT-PCR), hemagglutination assay, transmission electron microscopy (TEM), and complete genome sequencing. Genotypic analysis revealed the following constellation: G9-P[4]-I1 (Lineage IV/II recombinant)-R1-C1-M1-A1-N1-T1-E1-H1. These findings suggest that strain 543765 exhibits stable structural and replication properties, achieving titers of up to 10⁸ TCID₅₀/mL in MA104 cells. Given its genetic profile and in vitro growth characteristics, strain 543765 holds promise as a candidate for development into a monovalent vaccine capable of inducing both homotypic and heterotypic immune protection against G9P[4] and other RVA genotypes. However, further investigation is warranted to evaluate whether serial passages in cell culture have resulted in attenuation, a determination that requires validation through clinical studies.