The efficacy of L. (L.) chagasi excreted-secreted antigens (ESAs) for visceral leishmaniasis diagnosis is due to low levels of cross-reactivity

Abstract

The analysis of promastigote excreted-secreted antigen (ESA) reactivity with 53 visceral leishmaniasis (VL) cases showed that each sample reacted regardless of the antigen or the Leishmania species used in enzyme-linked immunosorbent assay (ELISA) displayed 100% positivity with the L. (L.) chagasi ESA-blot recognizing bands of molecular weight ranging from 26.5 to 31.5 kDa. The analysis of 160 non-visceral cases showed that 5% of the samples cross-reacted with the L. (L.) chagasi ESA-ELISA and 9.4% reacted with the ESA isolated from L. (L.) amazonensis and L. (V.) braziliensis, whereas a high cross-reaction ranging from 24.4% to 25% was observed with total crude promastigote antigens (PRO-ELISA). The ESA-blot of L. (L.) chagasi tested with non-visceral sera samples showed a cross-reaction with 8.8% of cases; most of these cases represented tegumentary leishmaniasis and only one acute chagasic case. These data lead us to recommend the use of ESA as an alternative antigen in VL diagnosis.

Figure 1.

Immunoblotting of L. (L.) chagasi ESA (excreted–secreted antigens), WP (whole promastigote), and PRO (crude promastigote antigen). (A) Visceral leishmaniasis (VL) sera pool IgG reactivity to ESA isolated from L. (L.) chagasi after 1, 3, 6, 12, 24, and 48 hours incubation; WP and PRO. (B) Monoclonal anti-α tubulin antibody reactivity to ESA, WP, and PRO. MW = low molecular weight marker.

Figure 2.

IgG reactivity of visceral leishmaniasis (VL) sera pool to excreted–secreted antigens (ESA) isolated from L. (L.) amazonensis (La), L. (V.) braziliensis (Lb), and L. (L.) chagasi (Lc) via immunoblotting. MW = low molecular weight marker.

Figure 3.

Immunoblotting of excreted–secreted antigens (ESA) (ESA-blot) with a panel of serum. IgG reactivity of visceral leishmaniasis (VL) sera samples to ESA from (A) L. (L.) amazonensis, (B) L. (V.) braziliensis, and (C) L. (L.) chagasi, (lanes 1–3); a cutaneous leishmaniasis (CL) case (lane 4); a chronic chagasic case (lane 5); and an acute chagasic case from a co-endemic region for leishmaniasis and Chagas disease (lane 6). MW = low molecular weight marker.