Abstract
We report here the molecular cloning and characterization of two related hydrophilic antigens of
Leishmania chagasi. These two antigens have predicted molecular weights of ∼9 and 26 kDa and detect antibodies in sera of patients with kala-azar (k). Thus, to maintain consistency with nomenclature of the previously described 39kDa diagnostic antigen of
L. chagasi (
k39
[1]), these antigens are being referred to as
k9 and
k26. A significant difference between
k9 and
k26 is the presence of 11 copies of a 14 amino acid repeat in the open reading frame of
k26. The region flanking the repeats of
k26 shares a 69% identity with the open reading frame of
k9. The recombinant proteins encoded by both antigens are very hydrophilic and show aberrant migration on SDS PAGE. Results of Southern blot analysis reveal that
k9 and
k26 are conserved to varying degrees among various
Leishmania species. Interestingly, the repeat region of k26 is specific to
L. chagasi and
L. donovani while the flanking region is conserved among several other species. Transcript levels of
k26 are significantly upregulated in the amastigote stage of the parasite. Our results show that recombinant K26 is specific in detecting antibodies in infection sera from visceral leishmaniasis (VL) patients. Thus rK26 may complement rK39 in a more accurate diagnosis of VL in the old and the new world.