Isolation, Characterization, and Comparative Analysis of Two Subtypes of Goose Astrovirus in Guangdong Province, China

Since 2017, an infectious disease characterized by gosling gout and caused by goose astrovirus (GAstV) has affected geese in most major goose-producing regions of China. In this study, a total of 385 geese displaying gout symptoms were sampled from 12 cities in Guangdong Province, China, between 2019 and 2021. RT-PCR analysis revealed that all samples were positive for GAstV (385/385), with GAstV-II being the predominant subtype, accounting for 90.4% (348/385) of the cases. Co-infection with GAstV-I and GAstV-II was detected in 50.4% (194/385) of the samples. Additionally, different GAstV subtypes were successfully isolated using goose embryos, namely GDYJ-21-01 (GAstV-I) and GDZJ-21-01 (GAstV-II). Analysis of viral copy numbers in major pathological tissues following infection of goslings and goose embryos revealed that GDZJ strain exhibited broader tissue tropism than GDYJ strain. Compared to other tissues, GDYJ strain displayed tissue tropism exclusively in the cecal tonsils of goslings and the allantoic fluid of embryos. Structural prediction and alignment using AlphaFold 2.0 identified an α-helix in the S223-A226 region of the GDZJ VP34 protein, while a loop structure was observed in the Q235-Q237 region of the corresponding GDYJ VP34 protein. Furthermore, although the VP27 protein regions of both subtypes contained five β-sheet structures, the overall sequence similarity was relatively low, at 37.1%. This study broadens our understanding of the prevalence differences among GAstV subtypes and provides valuable insights into the development of reagents for preventing these viral infections.