Antiviral activity of marine fungal polysaccharide AVP141-A against Singapore grouper iridovirus (SGIV) in vitro and in vivo.

Abstract

Singapore grouper iridovirus (SGIV) represents a major viral pathogen responsible for severe economic losses in the grouper aquaculture industry, emphasizing the urgent need for effective antiviral agents. In the present study, the antiviral activity of the natural compound AVP141-A against SGIV was systematically evaluated in vitro and in vivo. In vitro, AVP141-A showed no cytotoxicity to GS cells at concentrations up to 5 mg/mL, and significantly inhibited SGIV replication in a concentration-dependent manner. This inhibitory effect was reflected by attenuated cytopathic effects, reduced transcription of viral genes (MCP and VP19), and decreased expression of the viral MCP protein. AVP141-A downregulated the SGIV-induced overexpression of pro-inflammatory cytokines (IL-6, IL-8, TNF-ɑ and IL-1β), and modulated the expression and phosphorylation-dependent activation of key factors involved in the MAPK signaling pathway. In vivo, the groupers fed diets supplemented with 0.1% AVP141-A for 28 d exhibited significantly improved survival after SGIV challenge. AVP141-A treatment also alleviated histopathological damage in the spleen and liver, and reduced viral loads in these organs. Furthermore, AVP141-A mitigated intestinal villus atrophy and mucosal damage, inhibited viral replication in the intestine, suppressed excessive intestinal pro-inflammatory cytokine expression, and upregulated the expression of critical tight-junction proteins (ZO-1, Occludin, Claudin-1 and Claudin-3). Collectively, the results demonstrate that AVP141-A possesses potent antiviral activity against SGIV by regulating inflammatory responses and preserving intestinal barrier integrity, supporting its potential as a promising antiviral candidate for the prevention and control of SGIV in grouper aquaculture.