Susceptibility and immune responses of hybrid snakehead (Channa maculata♀ x Channa argus ♂) following infection with snakehead fish vesiculovirus

Snakehead fish vesiculovirus (SHVV) was initially isolated from diseased hybrid snakehead, and could cause great economic losses in snakehead culture due to its high morbidity and mortality. In this study, the susceptibility, histopathological analysis, and host immune response of hybrid snakehead infected with SHVV were investigated. SHVV was highly pathogenic to hybrid snakehead, and the infected fish exhibited typical signs of acute haemorrhages, and enlarged visceral organs. Histopathological analysis showed that the major tissues of diseased fish exhibited obvious inflammatory responses to SHVV infection. Additionally, humoral immune factors such as superoxide dismutase (SOD), catalase (CAT), and acid phosphatase (ACP) were assayed as serum indicators to evaluate the immune responses induced in infected hybrid snakehead. Quantitative real-time PCR (qRT-PCR) was also performed to evaluate the expression patterns of immune-related genes (HSP70, IL-8, MHCI alpha, MHCII alpha, SOD1, ZAP7 theta, PKCO, LCK, and HLA-A) in tissues of liver, spleen, head kidney and intestine. The results showed significantly enhanced immune activities in hybrid snakehead after SHVV infection. Altogether, these data provided insights into the pathogenic mechanism of SHVV and host immune response, facilitating the future prevention and treatment of hybrid snakehead infected with SHVV.