Astroviral infection is considered to be one of the causes of mammalian diarrheal diseases. It has been shown that astrovirus infections cause varying degrees of diarrhea in turkeys and mice. However, the pathogenesis of porcine astrovirus is unknown. In this study, the virulence of a cytopathic porcine astrovirus (PAstV) strain (PAstV1-GX1) isolated from the PK-15 cell line was tested using seven-day-old nursing piglets. The results showed that PAstV1-GX1 infection could cause mild diarrhea, growth retardation, and damage of the villi of the small intestinal mucosa. However, all the above symptoms could be restored within 7 to 10days post inoculation (dpi). To evaluate the innate immunity response of PAstV in vivo, the alteration of inflammatory cytokine expression in piglets infected with PAstV1-GX1 was determined using quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). The mRNA expression levels of the IFNβ and ISG54 were found to be significantly elevated in virus-infected piglets. In contrast, expression of IFNλ was downregulated in piglets infected with PAstV1-GX1. In addition, the mRNA expression of the tight junction protein 1 and 2 and zonula occludin 1, which are associated with the intestinal barrier permeability, were affected after PAstV1 infection. The present study adds to our understanding of the pathogenic mechanism of PAstV and has established an animal model for further study of pig astrovirus infection.
In recent years, hunniviruses have been reported in a variety of animal species from many countries. Here, hunnivirus was detected in fecal samples from water buffaloes and named as BufHuV-GX-2106. The samples were inoculated into cultures of MDBK cells supplemented with TPCK trypsin and the BufHuV-GX-2106 strain was stably passaged and replicated. Electron microscopic analysis showed the BufHuV-GX-2106 virus particles were spherical and 20~30 nm in diameter. The complete genome of a plaque purified sample of BufHuV-GX-2106 was determined and analyzed. Genomic analysis revealed that the whole sequence of BufHuV-GX-2106 was ~7,601 nucleotides (nt) in length and consisted of a large open reading frame of 6,759nt, a 5′UTR, a 3'UTR and a poly(A) tail. The complete genome sequence of BufHuV-GX-2106 shares 68-85% nucleotide identities with other known hunnivirus strains, indicating high genetic heterogeneity among these viruses. Phylogenetic analysis showed that BufHuV-GX-2106 belonged to the Hunnivirus A species and was more closely related to ovine hunnivirus than other known viruses of this type. This study describes the first isolation and complete genome sequence of a hunnivirus strain from water buffaloes. In addition, this study will help to understand the mechanisms involved in the pathogenesis of Hunnivirus A among different animal species.
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