Molecular characteristics and pathogenicity of a novel chicken astrovirus variant

Figures

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  Figure 1. Isolation and identification of CAstV. A LMHs were infected with virus isolates and tested by PCR for various chicken-original viruses. B Cytopathic effects of LMH-infected SDAU2022-1 at 48 hpi. C Growth kinetics of CAstV isolate infected LMHs at 6, 12, 24, 48, and 72 hpi. D Structural representation of CAstV, featuring three open reading frames (ORFs) and characteristic “stem-loop-II-like” motifs. The initiation site of the heptameric AAAAAAC (RFS) sequence is indicated by black triangles. Gray bars are the transmembrane domains. ORF, open reading frame; RFS, ribosomal frameshift signal; s2m, stem-loop-II-motif.

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  Figure 2. Phylogenetic relationships between the AAstV isolates. The analysis was based on the nucleotide sequences of the complete genome (A) and amino acid sequences of the complete ORF1a (B), ORF1b (C), and ORF2 (D) regions. The phylogenetic trees were constructed using MEGA 7, the neighbor-joining method, and 1000 bootstrap replicates. GenBank accession numbers of the sequences are indicated in parentheses. The scale bar corresponds to genetic distance. The red squares represent the other three CAstV isolates. E The mutation of the amino acid sequences in ORF2 protein.

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  Figure 3. Body weight gain and survival curves of experimental chickens. A Changes in body weight at 10 days of age in the intraperitoneal and oral groups. Control stands for control. Po stands for oral infection group. Intraperitoneal stands for intraperitoneal infection group. B Weight gain of chickens infected with SDAU2022-1. *p < 0.05, ** p < 0.01, *** p < 0.001 C Survival curves of chickens after infection. D Gross lesions of experimental chickens.

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  Figure 4. Histopathologic observations of proventriculus, pancreas, kidney, and liver (H&E staining). In the intraperitoneal infection group, proventriculus tissue exhibited necrosis of proventriculus tubules accompanied by lymphocytic infiltration (400 ×). Increased density of lymphocytic infiltration in pancreatic tissue (400 ×), while liver tissue displayed lymphocytic infiltration around the central hepatic venous vessels. Kidney tissue presented with necrosis of renal tubular epithelial cells and necrotic foci (200 ×). In the oral infection group, proventriculus tubules exhibited lymphocytic infiltration and proventricular dilatation (400 ×). Pancreatic tissue showed lymphocytic infiltration accompanied by pancreatic hemorrhage (400 ×). Liver tissue displayed lymphocytic infiltration around the central hepatic venous vessels. Kidney tissue exhibited swelling of renal tubular epithelial cells that compressed the lumen of the renal tubules (200 ×). Normal tissue (proventriculus, pancreas, liver, and kidney) in the control group (200 ×).

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  Figure 5. Detection of viral loads in organs. Intraperitoneal infection group (A) and oral infection group (B) of viral loads detection in the digestive organs. Digestive tract viral loads testing in the intraperitoneal group (C) and oral group (D). Intraperitoneal infection group (E) and oral group (F) of viral loads detection in the Immune organ. Intraperitoneal infection group (G) and oral group (H) of viral loads detection in the other organ. I The viral loads in blood of chickens infected with CAstV. J The viral loads in cloacal swabs of chickens infected with CAstV.

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  Figure 6. Serum dynamics of ALT, AST, UA, and UN in chickens post-infection with CAstV. * Indicates a statistically significant difference between the infection and control groups. ** Indicates a highly significant difference between the infection and control groups. *** Indicates an exceptionally significant difference between the infection and control groups.