A novel Leishmania infantum recombinant antigen which elicits interleukin 10 production by peripheral blood mononuclear cells of patients with visceral leishmaniasis

We report here the characterization of a novel Leishmania infantum protein termed papLe22 (22-kDa potentially aggravating protein of Leishmania). A po sitive clone from a cDNA library was identified by serum of a visceral leis hmaniasis (VL) patient. Full-length cDNA obtained using rapid amplification of cDNA ends-PCR codes for a 22-kDa protein. In L. infantum promastigotes an endogenous nuclear protein of 14-kDa electrophoretic mobility was found by using an antiserum prepared against the fusion protein glutathione S-tra nsferase-papLe22. Its expression was also shown in L. infantum amastigotes and in Leishmania major and Leishmania guyanensis promastigotes. VL patient s' sera showed anti-papLe22 immunoglobulin M (IgM) and IgG reactivities, in dicating that a primary response against the leishmanial protein papLe22 ac companied acute VL manifestations. Specific IgG levels were correlated with patients' clinical status. The presence of IgG1, IgG2, and IgG3 subclasses suggested a mixed Th1- and Th2-type response; there was no correlation bet ween subclass reactivity and the disease course. The recombinant papLe22 sp ecifically activated interleukin-10 production by VL patients' peripheral b lood mononuclear cells collected at diagnosis and after treatment-induced c ure, indicating its contribution to VL pathogenesis and concomitant immunos uppression and its potential role in the reactivation of latent parasites. As a dominant immunogen, papLe22 might be used as a vaccine component, prov ided that the vaccination protocol directs the response toward the Th1 patt ern.