##plugins.themes.huaf_theme.article.main##
Abstract
This study was conducted to evaluate the efficacy of different delivery methods of inactivated Streptococcus iniae vaccine (SiV) on the immune response and protective efficiency in Asian seabass (Lates calcarifer). The experiment consisted of three treatments: double immersion (NT1), immersion combined with injection (NT2), and double injection (NT3), and a control group injected with phosphate-buffered saline (PBS). Immunological parameters, including antibody titers, specific antibody IgM concentration, and Relative Percentage Survival (RPS), were assessed at 30, 90, and 180 days after the second immunization. The results showed that antibody titers, specific antibody concentration, and RPS decreased over time depending on the vaccine delivery methods. In particular, the double injection method (NT3) achieved the highest efficiency with antibody content reaching OD₄₉₂ = 0.405, agglutination titer of 1:147 and RPS protection efficiency reaching 94.4% at 30 days after immunization and maintained above 80% up to 180 days. The combined immersion injection method (NT2) also gave relatively high protection results (70.8% -76.7%). In contrast, immersion alone (NT1) only induced a low immune response and unsustainable protection. These findings confirm that intraperitoneal injection is the most effective strategy to induce strong and long-lasting immunity, making it suitable for large-scale commercial farming of L. calcarifer. Moreover, combined delivery methods as immersion followed by injection may offer a practical compromise between protective efficacy and operational feasibility in aquaculture.
Key word: Lates calcarifer, vaccine delivery methods, Streptococcus iniae, inactivated vaccine.