Assessing humoral and cell-mediated immune response in Hawaiian green turtles, Chelonia mydas

Seven immature green turtles, Chelonia mydas, captured from Kaneohe Bay on the island of Oahu were used to evaluate methods for assessing their immune response. Two turtles each were immunized intramuscularly with egg white l ysozyme (EWL) in Freund's complete adjuvant, Gerbu, or ISA-70; a seventh tu rtle was immunized with saline only and served as a control. Humoral immune response was measured with an indirect enzyme linked immunosorbent assay ( ELISA). Cell-mediated immune response was measured using in vitro cell prol iferation assays (CPA) using whole blood or peripheral blood mononuclear ce lls (PBM) cultured with concanavalin A (ConA), phytohaemagglutinin (PHA), o r soluble egg EWL antigen. All turtles, except for one immunized with Gerbu and the control, produced a detectable humoral immune response by 6 weeks which persisted for at least 14 weeks after a single immunization. All turt les produced an anamnestic humoral immune response after secondary immuniza tion. Antigen specific cell-mediated immune response in PBM was seen in all turtles either after primary or secondary immunization, but it was not as consistent as humoral immune response; antigen specific cell-mediated immun e response in whole blood was rarely seen. Mononuclear cells had significan tly higher stimulation indices than whole blood regardless of adjuvant, how ever, results with whole blood had lower variability. Both Gerbu and ISA-70 appeared to potentiate the cell-mediated immune response when PBM or whole blood were cultured with PHA. This is the first time cell proliferation as says have been compared between whole blood and PBM for reptiles. This is a lso the first demonstration of antigen specific cell-mediated response in r eptiles. Cell proliferation assays allowed us to evaluate the cell-mediated immune response of green turtles. However, CPA may be less reliable than E LISA for detecting antigen specific immune response. Either of the three ad juvants appears suitable to safely elicit a detectable immune response in g reen turtles. (C) 2000 Elsevier Science B.V. All rights reserved.