CHARACTERIZATION OF THE IMMUNOSTIMULATORY PROPERTIES OF LEISHMANIA-INFANTUM HSP70 BY FUSION TO THE ESCHERICHIA-COLI MALTOSE-BINDING PROTEININ NORMAL AND NU NU BALB/C MICE/

Leishmania infantum HSP70 has been described as an immunodominant anti gen in both humans and dogs suffering from visceral leishmaniasis. In this study, we used L. infantum HSP70 fused to Escherichia coil maltos e-binding protein (MBP), as the reporter protein, to analyze the influ ence of HSP70 on the immunogenicity of MBP in BALB/c mice. Plasmids we re constructed to produce the three recombinant proteins used in this study, namely, MEP, L. infantum HSP70, and MBP-HSP70, which consists o f MBP fused to the L. infantum HSP70 amino terminus. Immunization of B ALB/c mice with the MBP-HSP70 fusion protein elicited humoral and cell ular responses against MBP that were higher by an order of magnitude t han those elicited by immunization with MBP alone or with a mixture of MBP and HSP70. Covalent linkage of MBP to HSP70 was essential for eli citing a strong anti-MBP immune response. Cytokine secretion and immun oglobulin G isotype analyses indicated that immunization with the MBP- HSP70 fusion protein preferentially induces a Th1 immune response. Imm unization of athymic nu/nu mice with the MBP-HSP70 fusion protein unex pectedly gave rise to an anti-MBP humoral response showing features of a T-cell-dependent response. Thus, we present evidence that L. infant um HSP70 demonstrates an adjuvant effect in the immune response agains t a covalently linked reporter protein.