Avaliação da resposta humoral de Tambaqui, Colossoma macropomum infectado pelo acantocéfalo Neoechinorhynchus buttnerae

Abstract

This study evaluated the local and systemic humoral immune response of Colossoma macropomum to infection by acanthocephalan Neoechinorhynchus buttnerae, a recurrent parasite in tambaqui cultivation that has caused losses to fish farms, especially in Brazil northern region. First, a literature review was performed to find out the main responses in teleost fish to helminth parasite infection. As a result, it was observed that increasing the number and size of mucus producing cells is the most common response in almost all species investigated. Rodlet cells and mast cells, together with neutrophils and macrophages are often associated with the presence of helminths in the mucosa, especially intestinal mucosa. The role of the adaptive immune system in helminth defense and elimination is still a poorly explored field due to methodological difficulties and the increased focus on the innate immune system of fish. Nevertheless, new findings characterizing differences in local and systemic immune responses have stimulated further research targeting the adaptive immune system of fish in helminth infections. Therefore, it was proposed an adaptation of an established method for the purification and isolation of immunoglobulins in mammals, in order to facilitate the study of these molecules, especially in native species. Purification of intestinal mucosal immunoglobulins by the caprylic acid method was performed on 10 infected and 10 uninfected tambaqui. Some classes of immunoglobulins have been partially isolated, but the methodology still needs to be adjusted to achieve the highest purity, verified by SDS-PAGE electrophoresis. Still, this technique is simpler and less expensive compared to other commonly used purification techniques. In western blot, it was possible to detect immunoglobulins present in the mucus with serum total anti-Ig antibodies, indicating the presence of equal class (es) in both tambaqui body fluids. Acanthocephalan infection Neoechinorhynchus buttnerae resulted in higher immunoglobulin expression in the intestinal mucus, presenting higher immunoglobulin titers in infected animals. In a second experiment, 10 infected and 10 uninfected tambaquis in two different weight classes were separated. Serum and intestinal mucus were collected for evaluation of innate and adaptive immune response components. Intestinal immunohistochemistry of infected and uninfected tambaqui was performed to confirm the presence of immunoglobulins in the intestinal mucosa and the interaction of these molecules with acanthocephalan. Increases in total immunoglobulin and alkaline phosphatase titers were observed, as well as in serum and mucus total protein levels, and decreased immunoglobulin and alkaline phosphatase titers in the intestinal mucus of infected animals. The presence of immunoglobulins in cells present in the lamina propria of uninfected animals and immunoglobulins in intestinal mucus and in direct contact with the parasite surface was revealed by immunohistochemistry. Thus, in acanthocephalan infections, local and systemic responses of the tambaqui immune system are observed, highlighting the importance of mucus for the evaluation of local alterations and serum to assess the health status of the fish.