Adjuvant effect of leishmania major promerstigotes on the immune response of mice to ovalbumin

ABSTRACT

The immune responses of mice immunized with ovalbumin [OVA] together with killed L. major [KLM] promastigotes as adjuvant were studied. Three doses [5 ' 107, 1 ' 108 and 2 ' 108] of KLM combined with OVA [100 micro g] were injected into the groups of C57BL/6 mice. BCG and complete Freund's adjuvant [CFA] were used as control adjuvants. Lymphocyte proliferation and antibody titers were determined, and IFN-gamma and IL-4 were measured in the supernatants of lymph node cell cultures. Results showed that immunization using OVA mixed with KLM enhanced the in vitro proliferative response of T-cells to the antigen and resulted in the production of increased levels of IFN-gamma [2800-3700 pg/ml] relative to the mice injected with OVA alone [1750 pg/ml]. In the mice receiving OVA + 5 ' 107 KLM, the production of IL-4 remained lower [18, 20 pg/ml] than OVA alone [105, 109 pg/ml] and almost was similar to that of observed in mice inoculated with OVA + BCG, leading to high IFN-gamma /IL-4 ratios. Using higher doses of KLM [1 ' 108], the IL-4 responses were of the same magnitude as or higher than the responses of mice inoculated with OVA + CFA. Antibody titers to OVA were also strongly boosted at the highest KLM dose. These findings indicate that KLM may function as an adjuvant, and its dose plays a role in the eventual outcome of the response. Inoculation of the mice with a low dose of KLM [5 ' 107] tends to promote a Th1-type response