Complete genome sequence analysis of rare G4P[6] rotavirus strains from human and pig reveals the evidence for interspecies transmission

Two rare human rotavirus strains, RVA/Human-wt/THA/CMH-N016-10/2010/G4P[6] and RVA/Human-wt/THA/CMH-N014-11/2011/G4P[6], were detected during the surveillance of group A rotavirus (RVA) in Chiang Mai, Thailand. Complete genome sequences of both strains were analyzed in comparison with that of the representative porcine G4P[6] RVA strain (RVA/Pig-wt/THA/CMP-011-09/2009/G4P[6]) detected in the same geographical area. Human RVA strain CMH-N016-10 containing the genotype constellation of G4-P[6]-I1-R1-C1-M1-A8-N1-T1-E1-H1 was identical to that of porcine RVA strain CMP-011-09. Another human RVA strain (CMH-N014-11) was also contained the genotype constellation of ten segments identical to those of CMH-N016-10 and of porcine RVA strain CMP-011-09 except for genotype I of VP6 gene which contained I5 instead of I1. The genotype constellation of CMH-N014-11, G4-P[6]-I5-R1-C1-M1-A8-N1-T1-E1-H1 was a novel genotype constellation that has not been reported previously in both human and pig. Phylogenetic analysis of all 11 genome segments revealed that both strains of human RVA were more closely related to porcine and porcine-like human than to human RVA reference strains, particularly those reported from Thailand and other Asian countries with very high nucleotide sequence identities ranging from 91.1-100% except for NSP4 gene from 86.1-92.2%. Based on complete genome constellation and overall phylogenetic analyses suggested that these two human G4P[6] strains may have probably originated from porcine RVA strains of independent ancestor. This study provided an evidence for direct interspecies transmission of porcine RVA from pig to human.