Full-genome characterisation of a putative novel serotype of Yonaguni orbivirus isolated from cattle in Yunnan province, China

In July 2019, a novel viral strain (JH2019C603) was isolated from sentinel cattle in Jinghong City, in the subtropical region of Yunnan Province, China. The virus replicated and caused cytopathological effects in both Aedes albopictus (C6/36) and Baby Hamster Syrian Kidney (BHK-21) cells. Agarose gel electrophoresis analysis revealed a viral genome comprised of 10 segments of double-stranded RNA, with a 1-2-2-1-1-1-1-1 migration pattern. Complete genome sequences of the JH2019C603 virus were determined through full-length cDNA amplification. Phylogenetic analysis based on the amino acid (aa) sequences of RNA-dependent RNA Polymerase (Pol), Major subcore (T2) and Major core-surface (T13) showed that JH2019C603 clustered with Yonaguni orbivirus (YONOV) from Japan, with aa identities relative to YONOV of 97.7% (Pol), 99.0% (T2) and 98.5% (T13). However, phylogenetic analysis based on the aa sequences of the outer capsid protein one and two (OC1 and OC2) showed that JH2019C603 formed an independent branch in the phylogenetic tree, and its aa identity with YONOV was only 55.4% (OC1) and 80.8% (OC2), respectively. Compared with the prototype of YONOV, a notable sequence deletion was observed in the 3' non-coding region of NS1, with the NS1 of JH2019C603 encoded within segment 7 (Seg-7), in contrast to YONOV, which contains NS1 in Seg-6. These results indicate that JH2019C603 belongs to the YONOV lineage and might be a novel serotype or a highly variant strain of YONOV. These findings will facilitate the identification of new isolates and clarify their geographical distribution, epidemiology, genetic diversity and possible disease associations.

Full genome-based characterization of G4P[6] rotavirus strains from diarrheic patients in Thailand: Evidence for independent porcine-to-human interspecies transmission events

The exact evolutionary patterns of human G4P[6] rotavirus strains remain to be elucidated. Such strains possess unique and strain-specific genotype constellations, raising the question of whether G4P[6] strains are primarily transmitted via independent interspecies transmission or human-to-human transmission after interspecies transmission. Two G4P[6] rotavirus strains were identified in fecal specimens from hospitalized patients with severe diarrhea in Thailand, namely, DU2014-259 (RVA/Human-wt/THA/DU2014-259/2014/G4P[6]) and PK2015-1-0001 (RVA/Human-wt/THA/PK2015-1-0001/2015/G4P[6]). Here, we analyzed the full genomes of the two human G4P[6] strains, which provided the opportunity to study and confirm their evolutionary origin. On whole genome analysis, both strains exhibited a unique Wa-like genotype constellation of G4-P[6]-I1-R1-C1-M1-A8-N1-T1-E1-H1. The NSP1 genotype A8 is commonly found in porcine rotavirus strains. Furthermore, on phylogenetic analysis, each of the 11 genes of strains DU2014-259 and PK2015-1-0001 appeared to be of porcine origin. On the other hand, the two study strains consistently formed distinct clusters for nine of the 11 gene segments (VP4, VP6, VP1-VP3, and NSP2-NSP5), strongly indicating the occurrence of independent porcine-to-human interspecies transmission events. Our observations provide important insights into the origin of zoonotic G4P[6] strains, and into the dynamic interaction between porcine and human rotavirus strains.