Diagnosis of American visceral leishmaniasis in humans and dogs using the recombinant Leishmania donovani A2 antigen.

A2 proteins are expressed in the amastigote stage of Leishmania donovani and are composed predominantely by a conserved repetitive element. Here, we have investigated the presence of anti-A2 antibodies in a panel of American Visceral Leishmaniasis (VL) sera. Anti-A2 antibodies were detected by ELISA, using a recombinant A2 protein containing a tag of six histidine residues (A2-HIS), in 77% of patients sera with symptomatic VL and in 87% of sera from dogs that tested positive in Leishmania immunofluorescent-antibody test (IFAT) or in the parasitological evaluation. Anti-A2 antibodies were also detected in 14 out of 15 symptomatic and in 10 out of 13 asymptomatic dogs. In addition, among the asymptomatic/anti-A2 positive animals, 9 were also positive for the presence of parasites. No significant cross reactivity was observed with sera of animals with other common canine diseases. Our findings suggest that A2 protein is a potential tool for the diagnosis of VL in the New World, and will be particularly useful for diagnosis of dogs.