Antigenicity of Leishmania braziliensis histone H1 during cutaneous leishmaniasis: localization of antigenic determinants

Abstract

The humoral immune response against Leishmania braziliensis histone H1 by patients with cutaneous leishmaniasis is described. For this purpose, the protein was purified as a recombinant protein in a prokaryotic expression system and was assayed by enzyme-linked immunosorbent assay (ELISA) with a collection of sera from patients with cutaneous leishmaniasis and Chagas' disease. The assays showed that L. braziliensis histone H1 was recognized by 66% of the serum samples from patients with leishmaniasis and by 40% of the serum samples from patients with Chagas' disease, indicating that it acts as an immunogen during cutaneous leishmaniasis. In order to locate the linear antigenic determinants of this protein, a collection of synthetic peptides covering the L. braziliensis histone H1sequence was tested by ELISA. The experiments showed that the main antigenic determinant is located in the central region of this protein. Our results show that the recombinant L. braziliensis histone H1 is recognized by a significant percentage of serum samples from patients with cutaneous leishmaniasis, but use of this protein as a tool for the diagnosis of cutaneous leishmaniasis is hampered by the cross-reaction with sera from patients with Chagas' disease.

FIG. 1.

Antigenicity of recombinant L. braziliensis histone H1. The reactivities of 24 serum samples from patients with CL, 10 serum samples from patients with ChD, and 12 control serum samples (8 from Peruvian patients and 4 from Spanish patients) were assayed by ELISA. The cutoff line was established as the mean reactivity value plus 3 SDs for the control sera.

FIG. 2.

Reactivities of serum samples from patients with CL and ChD and control serum samples against recombinant L. braziliensis histone H1 (rLbH1) and synthetic peptides homologous to regions of L. braziliensis histone H1. Columns represent mean reactivities, and bars give the SDs for patient and control serum samples.