Adjuvant guided polarization of the immune humoral response against a protective multicomponent antigenic protein (Q) from Leishmania infantum. A CpG + Q mix protects Balb/c mice from infection

It has been shown that vaccination with three doses of the Leishmania infantum poly-protein Q containing five genetically fused antigenic determinants from the Lip2a, Lip2b, H2A and P0 proteins, mixed with BCG induces clearance of parasites in 9 out of 10 Leishmania infantum-infected Beagle dogs, in addition to clinical protection. In the present paper we analysed the immunogenic potential of the poly-protein Q and the specificity and polarization of the response against the antigenic determinants of Q when mixed with various adjuvants. The data showed that the Q protein had high intrinsic immunogenic potential and that it was able to induce a long-lasting IgG response. The IgM immunogenic potential of the poly-protein was mainly due to the LiP2a and LiP2b determinants, whereas the IgG immunogenic potential was mainly due to the LiP2a component. It was observed that the protein itself elicited a mixed IgG2a/IgG1 response and that the determinants of Q were endowed with different IgG2a/IgG1 potential. It was also observed that the adjuvants did not influence the intensity or specificity of the IgM response but that they modulated the intensity, the specificity and the polarization of the IgG response against the determinants of Q. CpG-ODN motifs or double-stranded DNA plasmids containing CpG motifs when mixed with Q induced a predominant IgG2a response mainly observed at early stages post-immunization. The data showed that a CpG + Q mix induced significant protection against L. infantum infection in Balb/c mice.