| In order to study on the pathologic lesions, tissue tropism and expression of MHC genes. Chinese giant salamander. Andrias davidianus (weight 280.3±20.2g and length 33,9±2.3cm) were infected by intraperitoneal injection with Chinese giant salamander ranavirus (CGSRV) at 1.0×106.5 TCID50ml-1. Liver, spleen.kindey, lung, intestine, stomach, skin-muscle, heart and brain were collected at 0d,3d,5d,7d,9d, 13d and 16d after infection for pathologic lesions and tissue tropism examination. Paraffin section and HE staining were used for histopathological observation, qPCR was used to examine the quantitative dynamic distribution and tissue tropism of CGSRV. Symptoms showed mucus secretion increased on body surface. Anorexia and movement reduced, loss of appetite or waste, hemorrhages and ulcers are common in the skin-muscle. Necropsy examination revealed:swelling in liver, spleen and kindey at 3d after infection:7-9d, ascites appeared, gastrointestinal tract became empty, pulmonary hemorrhage, mullifocal necrosis in spleen:13-16d, swelling, petcchiac and ecchymosis hemorrhages in liver, multifocal necrosis in spleen, swelling and ecchymosis hemorrhage in kindey:yellowish mucus filled in gastrointestinal tracts. Histopathological examination:many tissues and organs extremely lesions caused by CGSRV, especially, serious pathological lesions in liver, spleen, kindey and muscle skin were the important target organs, basophilic or eosinophilic inclusions appeared in damaged cells. At 3d after infection, degeneration in hepatocytes and renal tubular epithelial cells, eosinophils and lymphocytes infiltration in renal interstitial and central vein of hepatic lobule.5-7d. degeneration and necrosis, inflammatory reaction progressed in parenchymatous organ.catarrhal inflammation in gastrointestinal tracts. 9d. necrosis, exfoliation of epidermal, degeneration and necrosis of muscle fibers. 13-16d. degeneration, necrosis and inflammation extensively in liver, lymphocytes remarkably reduced, glomerulonephritis with exudation and necrosis in kindey. hemorrhage, necrotic and inflammatory cells infiltration in skin-muscle, myocarditis in heart. qPCR results indicated that CGSRV copies in tissues increased during the process of infection at the range of 7.89×102—4.61×108copies/ug DNA. Virus copies were higher in the lung, intestine, liver, spleen, kidney and skin muscle, these indicate that CGSRV has a broaden tissue tropism and liver, spleen, kindey and skin muscle were also the target organs of viral replication and damaged, and a positive correlation between the amount of virus and pathological was showed.Expression of MHCⅠ and MHCⅡ genes in liver, spleen, kindey, intestine, stomach, skin, lung and muscle of Chinese giant salamanders were tested by qPCR at 0d,3d,5d,7d.9d.13d,16d after infection by CGSRV, respectively. The results showed that CGSRV induced MHC Ⅰ. MHC ⅡA and MHC ⅡB genes were changed their relative expression levels in all the chosen tissues. The expression level of all MHC showed time-dependent and first up-regulated and then down-regulated after infection by CGSRV and changes wasrestricted in tissues. Expression of MHC Ⅰ and MHC ⅡA genes were highly different after infection. MHC ⅡB gene changes gently.3 kinds of MHC genes in liver, spleen, kindey. lung. intestine at 3 d after infection with CGSRV significantly raised(P<0.01). reached a maximum at 5-9d and then decline. Expression level was up-regulated in skin and muscle at 5-7d(P<0.01). and then showed an up and down-regulated trend.The expression level is much higher than others(P<0.01). The results showed that the CGSRV infection had a significant effect on the expression of MHC genes of Chinese giant salamander and indicated that MHC genes play an important role in antiviral immunity after infected by CGSRV. |
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