Immunomodulatory effects of snake venom C-type lectins in vaccine formulations against ascariasis in mice

The search for novel vaccine adjuvants capable of enhancing or directing effective immune responses when combined with target antigens remains a global priority. Snake venom-derived biomolecules have previously demonstrated immunomodulatory activity in vitro, as reported in earlier studies, suggesting potential application as vaccine adjuvants. In this study, we evaluated the adjuvant potential of a C-type like lectin from Crotalus durissus terrificus (CVX) and a C-type lectin from Bothrops jararacussu (BjcuL) snake venoms in a murine immunization model using the recombinant BOT protein, previously described as immunoprotective against ascariasis. Mice received three immunizations at 10-day intervals and were subsequently challenged with Ascaris suum eggs. Formulations containing lectins enhanced the immunogenicity of BOT, inducing high levels of BOT-specific IgG. Although the BOT/CVX formulation elicited the highest antibody titers, only formulations containing MPLA or BjcuL significantly reduced parasite burden, whereas CVX did not confer protection and was associated with increased parasite load relative to the infected control. Endpoint analysis of circulating leukocytes and serum cytokines revealed that lectin-based formulations induced distinct immune profiles characterized by increased neutrophil frequencies and elevated IL-4 and IL-6 levels, while IL-2 was selectively increased in the CVX group. These findings highlight a dissociation between antibody magnitude and protective efficacy and indicate that BjcuL, but not CVX, displays adjuvant properties in this murine model of ascariasis. Collectively, this study supports the potential of selected snake venom lectins as vaccine adjuvants and emphasizes the importance of functional protection, safety evaluation, and mechanistic studies in future investigations.