ORAL AND RECTAL IMMUNIZATION OF ADULT FEMALE VOLUNTEERS WITH A RECOMBINANT ATTENUATED SALMONELLA-TYPHI VACCINE STRAIN

An attenuated strain of Salmonella typhi Delta cya Delta(crp-cdt) Delt a asd expressing a gene encoding a hepatitis B virus core-pre-S protei n was tested in female adult volunteers for its ability to elicit a sy stemic and a mucosal immune response. Specifically, our purpose,vas to evaluate the potential of such a vaccine strain to induce specific se cretory immunoglobulin A (sIgA) at genital and rectal surfaces. Oral a nd rectal routes of immunization were compared: oral immunization indu ced seroconversion against the bacterial lipopolysaccharide (LPS) in s ix out of seven volunteers, while after rectal immunization only one o ut of six volunteers seroconverted against LPS. To our disappointment, the latter volunteer was also the only one who seroconverted against the carried antigen (pre-S1), demonstrating the poor ability of this l ive vaccine to induce an immune response against the carried antigen. Anti-LPS sIgA was found in both the vaginal and cervical secretions of a volunteer who presented a strong seroconversion after oral immuniza tion (16-fold increase in anti-LPS IgG). Smaller amounts of anti-LPS s IgA were found in the rectal secretions of one orally and one rectally immunized volunteer and in the saliva of three orally and one rectall y immunized woman. Our data show for the first time that it is possibl e to induce specific sIgA in the genital and rectal tracts of women by using an S. typhi vaccine strain.