The Primary Immune Response of the Green Toad (Bufo viridis) to Challenge with Crithidia fasciculata

Abstract

The primary immune response of the green toad (Bufo viridis) following immunization with Crithidia fasciculata choanomastigotes was studied. Lysins, agglutinins, and antibodies detectable by enzyme-linked immunosorbent assay (ELISA) were first detected in the sera of immunized animals one week after injection. The antibody titers increased to significant levels (P<0.01) and maximum values were reached seven weeks post-immunization.The stimulated immunoglobulins were antigen-specific, partially heat-labile, sensitive to the reducing agent dithiothreitol, possessed precipitin activity, effectively fixed complement and exhibited an electrophoretic mobility similar to the 7-globulins of human serum. On this basis, it is probable that the antibody produced during the primary response in green toads is high molecular weight IgM. Increases in serum lysozyme levels paralleled the rise of antibody titers. Overall, the lysozyme concentration increased two-fold compared to the appropriate controls. This is the first report of the immune response in amphibians to experimental injection with protozoan parasites and the use of the ELISA technique to detect antibodies in amphibian sera.

Development of a pharmacodynamic screening model with Crithidia fasciculata

“…Crithidia fasciculata ( Fig. 1) occurs in nature as a commensal organism in the gut of insects and as a haemo-and endoparasite in amphibians [2]. Within the mosquito gut, C. fasciculata exists in two development forms/stages: one is a non-motile form, or haptomonad, attached in clusters to the lining of the insect gut, the other (nectomonad) is a more elongated form that swims freely in the gut lumen [3,4].…”