The gp63 gene encoding the major surface antigen of Leishmania
infantum has been cloned and sequenced. In spite of the
overall sequence homology with the gp63 genes from other Leishmania
species, particularly with the constitutively
expressed Leishmania chagasi Gp63 gene, the carboxy-terminal ends
of these genes are clearly divergent (62% homology).
To study the prevalence of anti-gp63 antibodies in the sera from dogs with
visceral leishmaniasis, a recombinant L.
infantum gp63 protein was expressed in Escherichia coli. It
was found that 100% of the sera from these dogs recognized
the recombinant gp63 protein, suggesting that it must function as a potent
B cell immunogen during natural canine visceral
leishmaniasis. However, heterogeneity in the level of response was observed.
Fine mapping of the antigenic determinants
was performed by means of 6 overlapping subfragments of the gp63 protein and
by the use of a library of synthetic
peptides. The data showed that there is some degree of immunological
restriction in the recognition of the protein since
reactivity was observed preferentially against the most divergent region.
The epitope mapping of this region showed 2
immunodominant peptides the response to which seems to be
preferentially of the IgG2 type.