Identification and molecular characterization of a gene encoding a protective Leishmania amazonensis Trp-Asp (WD) protein

Several Leishmania proteins have been identified and characterized in pursuit of understanding pathogenesis and protection in cutaneous leishmaniasis. In the present study, we utilized sera from infected BALB/c mice to screen a Leishmania amazonensis amastigote cDNA expression library and obtained the full-length gene that encodes a novel Trp-Asp (WD) protein designated LAWD (for Leishmania antigenic WD protein). The WD family of proteins mediates protein-protein interactions and coordinates the formation of protein complexes. The single-copy LAWD gene is transcribed as a approximately 3.1-kb mRNA in both promastigotes and amastigotes, with homologues being detected in several other Leishmania species. Immunoelectron microscopy revealed a predominant localization of the LAWD protein in the flagellar pocket. Analyses of sera from human patients with cutaneous and mucocutaneous leishmaniasis indicated that these individuals mounted significant humoral responses against LAWD. Given that recombinant LAWD protein elicited the production of high levels of gamma interferon, but no detectable levels of interleukin-10 (IL-10), in CD4(+) cells of L. amazonensis-infected mice, we further examined whether LAWD could elicit protective immunity. DNA vaccination with the LAWD and IL-12 genes significantly delayed lesion development, which correlated with a dramatic reduction in parasite burdens. Thus, we have successfully identified a promising vaccine candidate and antigenic vehicle to aid in the dissection of the complicated pathogenic immune response of L. amazonensis.