Schistosoma mansoni soluble egg antigens enhance Listeria vector HIV-1 vaccine induction of cytotoxic T cells. Clin. Vaccine Immunol

Schistosome infection induces significant T helper type 2 (Th2) and anti-inflammatory immune responses and has been shown to negatively impact vaccine efficacy. Our goal was to determine if the administration of schistosome soluble egg antigens (SEA) would negatively influence the induction of cytotoxic T lymphocyte (CTL) and Th1-type T cell responses to an HIV candidate vaccine in the Th1-biased C57BL/6 mouse strain. Initial experiments failed, as we were unable to detect any response to the de-fined class I epitope for HIV-1 IIIB Gag. Therefore, we initiated an epitope mapping study to identify C57BL/6 (H-2b) T cell epitopes in HIV-1 IIIB Gag in order to perform the experiments. This analysis defined two previously unreported minimal class I H-2b and class II I-Ab epitopes for HIV-1 IIIB Gag. The newly defined HIV-1 IIIB Gag epitopes were used to evaluate the influ-ence of SEA on the generation of CTL and Th1-type HIV-1 IIIB Gag responses. Surprisingly, in contrast to our hypothesis, we observed that the coadministration of SEA with a Listeria monocytogenes vector expressing HIV-1 IIIB Gag (Lm-Gag) led to a significantly increased frequency of gamma interferon (IFN-)-producing CD8 and CD4 T cells in C57BL/6 mice compared to mice immunized with Lm-Gag only. These observations suggest that SEA contains, in addition to Th2-type and immune-sup-pressive molecules, substances that can act with the Lm-Gag vaccine to increase CTL and Th1-type vaccine-specific immune responses. Vaccines for human immunodeficiency virus (HIV), tubercu-losis, and malaria are in development or in clinical trials. The greatest incidence of each of these diseases is in sub-Saharan Af