CYTOKINE PRODUCTION PATTERNS AND LYMPHOPROLIFERATIVE RESPONSES IN VOLUNTEERS ORALLY IMMUNIZED WITH ATTENUATED VACCINE STRAINS OF SALMONELLA-TYPHI

New recombinant strains of attenuated Salmonella typhi used as live or al vaccines elicit potent immune responses. This study examined the pa tterns of cytokine production and proliferation to specific S. typhi a ntigens in subjects orally immunized with attenuated S. typhi vaccines CVD 906, CVD 908, and CVD 908 expressing the circumsporozoite protein of Plasmodium falciparum. After immunization, sensitized lymphocytes were found in subjects' blood that exhibited significantly increased p roliferative responses and interferon-gamma production to purified S. typhi flagella when compared with preimmunization levels. Significant negative correlations were observed between interleukin-4 production a nd both interferon-gamma production and proliferation to S. typhi flag ella. These results demonstrate that oral immunization with attenuated S. typhi strains alone or with those carrying a foreign gene elicits strong systemic cell-mediated immunity to purified S. typhi antigens, including the production of cytokines compatible with T1-type response s.