The Leishmania infantum acidic ribosomal protein LiP2a induces a prominenthumoral response in vivo and stimulates cell proliferation in vitro and interferon-gamma (IFN-gamma) production by murine splenocytes

The acidic ribosomal proteins of the protozoan parasite Leishmania infantum have been described as prominent antigens during both human and canine vis ceral leishmaniasis. In this study we present data showing that the intrape ritoneal administration in BALB/c mice of the Leishmania LiP2a protein, in the absence of any added adjuvants, elicited a strong humoral response as a n indication that the protein is a potent immunogen. Despite the evolutiona ry conservation of the acidic ribosomal proteins, the antibody response was found to be specific for the Leishmania protein. Another remarkable findin g was the observation that the LiP2a protein stimulates the in vitro prolif eration of splenocytes from either LiP2a-immunized or naive BALB/c mice. Si nce similar proliferative indices were observed in T cell-enriched cultures , it is likely that the LiP2a stimulating activity is due mainly to T lymph ocyte expansion. Also, the stimulatory effect was demonstrated to be antige n-specific, since the proliferation was abrogated by the presence of anti-L iP2a antibodies. Interestingly, the LiP2a protein stimulated the production of substantial amounts of IFN-gamma in cultured splenocytes from LiP2a-imm unized mice. Our data indicate therefore that the immunostimulatory propert ies shown by this antigen should be taken into account when developing ther apeutic and prophylactic vaccines against leishmaniasis.