Humoral Immune Responses to Select Bacterial Pathogens in the American Alligator, \u3ci\u3eAlligator mississippiensis\u3c/i\u3e

The American alligator, Alligator mississippiensis, is widely distributed and abundant throughout the southeastern United States. Despite their abundance, these reptiles have not been examined for their role in environmental pathogen distribution, as a sentinel for the presence of various pathogens, or other humoral immune responses in individuals from different habitats. This study investigates the humoral immune responses of alligators to select bacterial pathogens. Immunoglobulin Y (IgY), an immunoglobulin molecule found in amphibians, birds and reptiles, similar to IgG in higher vertebrates. IgY was purified from pooled alligator serum collected in coastal South Carolina. Mouse polyclonal antisera (pAb) was then generated against IgY to develop a sensitive ELISA to quantify serum antibody responses and relative titers. Serum samples from alligators collected from multiple localities in Florida were screened for bacteria-specific antibodies to the following nine aquatic bacteria: Vibrio cholera, Escherichia coli, V. anguillarum, V. vulnificus, V. parahaemolyticus, Brevundimonas vesicularis, Mycobacterium marinum, Erysipelothrix rhusiopathiae and Streptococcus agalactiae. C-reactive protein (CRP) is an ancient acute phase protein, participating in complement activation and opsonisation of pathogens, and is usually indicative of relative levels of systemic inflammation. Alligator CRP was purified and used to generate a specific monoclonal antibody to develop ELISA-based approaches to semi-quantifying circulating CRP in individuals. Finally, serum lysozyme enzymatic activity was also quantified in individual samples. Humoral immune responses to various pathogens, along with CRP and lysozyme activity, may be correlated with environmental health. This study provides the first baseline data and proof of concept, to compare responses of wild alligators to pathogens throughout their distribution. This information will allow A. mississippiensis to be used as a sentinel of pathogen occurrence and environmental quality in future studies