Antigenic properties of the Leishmania infantum GRP94 and mapping of linear B-cell epitopes

In this study, we show that the glucose-regulated protein 94 (GRP94) from Leishmania infantum is a major target for humoral immune response during both visceral (VL) and mucocutaneous leishmaniasis (MCL). Also, the time-course of appearance of anti-GRP94 antibodies along the infection was analysed in hamsters (Mesocricetus auratus) experimentally infected with L. infantum. Remarkably, the reactivity against the Leishmania GRP94 was observed very soon after challenge, at the time of appearance of a humoral response against Leishmania total proteins, and long before that the animals develop clinical symptoms of disease. Therefore, at least for golden hamsters, the reactivity against Leishmania GRP94 is an early marker of infection. Using a collection of synthetic peptides covering the complete sequence of the L. infantum GRP94, we have determined the main linear antigenic determinants recognised by sera from humans, dogs, and hamsters suffering from VL. Four synthetic peptides, located in highly divergent regions of the protein, were found to be immunodominants and recognised by VL sera of these three different origins. We discuss that the prominent antigenicity of Leishmania GRP94 may be related to recent findings involving GRP94, and other heat shock proteins, in relevant immune functions such as tumour immunogenicity and antigen presentation.