Mucosal and humoral responses of javelin goby, Synechogobius hasta, after immersion vaccination using killed Vibrio vulnificus bacterin

Immersion vaccination is dependent on the response of fish mucosa-associated tissues. Herein, javelin goby Synechogobius hasta was immersed with Vibrio vulnificus bacterin to investigate mucosal and humoral immune responses post-vaccination. The results showed that the specific serum antibody titers gradually increased after vaccination and peaked at day 21, while the mucosal antibody titers in the gill, skin, and intestine showed a faster response, with the peak time at days 3, 5, and 7, respectively. For antigen uptake, a rapid and significant enhancement was detected in the mucosa-associated tissues (gill, skin, and intestine) compared with the blood, spleen, kidney, and liver (P < 0.05). Antigen uptake levels in the gills and skin were peaked at 12 h post-immersion and were significantly higher than other tissues (P < 0.05). The histological results showed that the mucous cell numbers in mucosa-associated tissues increased over time, peaked at day 3 post-immunization, and then decreased to the level of the control groups. Additionally, the mucin components in mucosa-associated tissues shifted from neutral mucopolysaccharide to acidic mucopolysaccharide. Integrations of antibody titers, antigen uptake in mucosa-associated tissues, mucous cell number changes, and mucin characteristic changes provided valuable information for research on mucosal immunity in fish. All present findings suggest a major advantage of immersion vaccines to elicit a high level of local immune response, making immersion vaccines an ideal mode of inoculation that induces protective immunity against a variety of pathogens.

Automated summary

This study investigated the mucosal and humoral immune responses of javelin goby to immersion vaccination with Vibrio vulnificus bacterin. The results showed that serum antibody titers increased gradually after vaccination, while mucosal antibody titers in the gill, skin, and intestine showed a faster response. Antigen uptake was significantly enhanced in mucosa-associated tissues compared to other organs. The histological results indicated an increase in mucous cell numbers in mucosa-associated tissues, with a shift in mucin components. These findings provide valuable information on mucosal immunity in fish and highlight the advantage of immersion vaccines in eliciting a high level of local immune response.