Molecular characterization and recombination analysis of Gyrovirus homsa2 in chickens

Gyrovirus homsa2 (GyVh2), originally identified in Tunisian children with diarrhoea, was previously known as Gyrovirus 6. In this study, chickens from 36 poultry farms across four major poultry-producing provinces in China (Henan, Hubei, Anhui, and Jiangsu) were screened for GyVh2 using polymerase chain reaction (PCR) from 2022-2024. As a result, 12 farms positive for GyVh2 were detected and subsequently subjected to whole-genome sequencing for GyVh2. The genomes of the 12 GyVh2 from positive farms were all 2282 nucleotides (nt) in length. Sequence similarity analysis showed high similarity (94.87%-99.65%) among the obtained and reference GyVh2 strains with no significant determining effect of years or geographic distribution, but low similarity (48.99%-57.60%) with other Gyrovirus species (Gyrovirus chickenanemia, Gyrovirus galga1, Gyrovirus galga2 and Gyrovirus homsa1). Phylogenetic analysis of the whole genome sequences of all 12 GyVh2-positive farms revealed that they formed a unique branch, clearly separated from other Gyrovirus species. Recombination analysis suggested that HN220604 (accession no.: PQ519595.1) and HN221228 (accession no.: PQ519596.1) may have originated from recombination with the human-derived GyVh2 strain (accession no.: NC_022789.1). A hypervariable region (located at sites 140-152) and highly mutated sites at positions 149, 254 and 380 were identified in the capsid protein through amino acid mutation analysis. The observed association between GyVh2 cross-species transmission and complex mutations and recombination offers a basis for future studies on its molecular epidemiology and evolution.