Analysis of the adjuvant effect of recombinant Leishmania infantum Hsp83 protein as a tool for vaccination

The properties of Leishmania infantum (LiHsp83) to elicit an immune response against a fused reporter antigen, maltose binding protein(MBP), was studied. CF1 mice were immunized with different purified recombinant proteins: MBP, LiHsp83 and MBP fused to LiHsp83 (MBP-LiHsp83). Serum samples were obtained at days 0, 21, 28, 60, 90, 120 and 150 post-immunization. MBP-LiHsp83 fusion protein elicited a strong humoral response against MBP, higher than that one obtained in mice immunized with MBP alone or MBP mixed with LiHsp83, showing the secretion of both anti-MBP IgG2a and IgG1 isotypes (IgG2a/IgG1 ratio: 2,1). This response was specific for recombinant proteins and was maintained for at least 150 days, whereas the reactivity in mice immunized with hii:BP alone dissapeared at day 90. After in vitro stimulation with MBP, spleen cells from MBP-LiHsp83 immunized mice showed higher proliferation indices and produced higher secretion of IFN-gamma than spleen cells from either control or MBP-immunized mice. In all groups of mice IL-4 was undetectable. Thus we consider that LiHsp83 may be a promising candidate to be: used as carrier of fused antigens for adjuvant-free vaccination. (C) 2001 Elsevier Science B.V. All rights reserved.