Multiple combinations of P[13]-like genotype with G3, G4, and G5 in porcine rotaviruses.

Epidemiological surveillance of porcine rotavirus (PoRV) strains was carried out in Chiang Mai Province, Thailand, from 2002 to 2003, and eight rotavirus isolates could not be completely typed by PCR. Of these, six were G3 and one was G4 and displayed a P-nontypeable genotype, while another isolate was both G and P nontypeable. Analysis of a partial VP4 gene of all eight P-nontypeable strains revealed a high degree of amino acid sequence identities (94.7% to 100%), suggesting that they belonged to the same P genotype. Comparison of the amino acid sequences of two representative strains (namely, strains CMP178 and CMP213) with those of 27 other known P genotypes revealed a high degree of amino acid sequence identity with those of P[13] porcine rotavirus reference strains HP113 and HP140, which were recently isolated in India. However, amino acid sequence comparison with non-P[13] rotavirus strains revealed relatively low identities, ranging from 58.2% to 84.8% for full-length VP4 sequences and 35.1% to 80.6% for VP8* sequences. Phylogenetic analysis revealed that CMP178 and CMP213 clustered together in a monophyletic branch with P[13]-like genotypes HP113 and HP140 which was clearly separated from the other lineages of P[13] or P[22] strains. Altogether, these findings indicate that PoRV strains CMP178 and CMP213 should be considered the P[13]-like VP4 genotype, a rare genotype that has been identified only in pigs. This study provides additional evidence of increasing genetic diversity among group A rotaviruses in nature.