Immunoadjuvant potential of Asparagus racemosus ethanolic root extract on protection and immune response of Labeo rohita immunized with inactivated Aeromonas hydrophila vaccine

Medicinal herbs are known for their diverse immunomodulatory properties, with bioactive compounds making them potential immunoadjuvants in vaccination. This study investigated the immunoadjuvant potential of ethanolic root extract from Asparagus racemosus (AREE) in rohu (Labeo rohita) fingerlings, using a formalin-killed Aeromonas hydrophila vaccine. A total of 360 rohu fingerlings were randomly divided into six groups, each with three replicate tanks. The fish were immunized via intraperitoneal injection with one of the following: phosphate-buffered saline (PBS), bacterin (B), bacterin combined with AREE (B + AREE), bacterin mixed with Freund’s complete adjuvant (B + FCA), FCA alone, or AREE alone. Serum, head kidney leucocytes, and head kidney tissues were collected 30 days post-immunization to assess antibody titers, antigen-specific leucocyte proliferation, and expression of immune genes (IL-1β, IFN-γ, IL-2, IgM, and IgT). Thirty days after immunization, ten fish from each group were challenged with A. hydrophila, and mortality was monitored for 2 weeks to calculate survivability. The B + AREE and B + FCA groups exhibited significantly higher (P ≤ 0.05) antibody titers, leucocyte proliferation, and immune gene expression compared to other groups. The post-immunization challenge revealed a significantly higher (P ≤ 0.05) survivability rate in the B + AREE (66.67 ± 3.33%) and B + FCA (70 ± 5.77%) groups. These findings suggest that AREE can serve as an effective immunoadjuvant with A. hydrophila bacterin, offering similar protection to Freund’s complete adjuvant in rohu against A. hydrophila infection.