DIFFERENTIAL MODULATION OF MURINE CELLULAR IMMUNE-RESPONSES BY SALIVARY-GLAND EXTRACT OF AEDES-AEGYPTI

The ability of salivary gland extract (SGE) of Aedes aegypti to modula te cellular immune responses was investigated in a mouse model. Cytoki ne production was induced in naive and antigen-primed murine (BALB/c) spleen cells in vitro by stimulation with the T cell mitogen concanava lin A or the T cell-dependent antigen ovalbumin (OVA), respectively. i nclusion of Ae. aegypti SGE in in vitro culture with naive cells cause d significant suppression of the cytokines interleukin-2 (IL-2) and in terferon gamma in culture supernatants, while levels of other cytokine s (IL-4 and IL-5) were unaffected by SGE. In contrast, SGE did not aff ect cytokine production by antigen-activated cells derived from OVA-pr imed mice. To determine whether SGE could inhibit the responsiveness o f cells to exogenous cytokine stimuli, optimized quantities of lymphoc yte growth factor cytokines IL-2 and IL-4 were added to SGE-treated sp leen cells and the degree of cellular proliferation was determined. Ce llular proliferation in response to IL-2 was markedly suppressed by pr ior exposure of cells to SGE, while the proliferative response to IL-4 was also affected by SGE but to a lesser extent. These results confir m that mosquito SGE can modulate host immune responses, and suggest th at in Ae. aegypti modulation is directed primarily against cytokines a ssociated with type 1 lymphocyte responses. The mode of immunomodulati on and the possible relevance of these results to vector-borne disease research are discussed.