A β-mercaptoethanol-modified enzyme-linked immunosorbent assay for diagnosis of canine visceral leishmaniasis

Abstract

A β-mercaptoethanol-modified enzyme-linked immunosorbent assay for diagnosis of canine visceral leishmaniasis

Laura Barral-Veloso, Saul J. Semião-Santos, Paulo P. de Andrade, Marcia A. de Melo, Luís Martins, Artur A. Marinho, José A. A. de Almeida, Luís Cardoso, Abdallah el Harith

Abstract Two immunoglobulin G enzyme-linked immunosorbent assay (ELISA) versions using whole promastigotes of Leishmania infantum (syn. Leishmania chagasi) treated either with β-mercaptoethanol (β-ME_ELISA) or trypsin (TRYP-ELISA) as antigens were developed for the diagnosis of canine visceral leishmaniasis (CVL). By comparison with the direct agglutination test (DAT; 100%, 31/31; 95% confidence interval [CI]: 86.3-100%, slightly lower sensitivity was demonstrated for the newly developed β-ME-ELISA (93,5%, 29/31; 95% CI: 77.2-98.9). Sensitivity was higher for β-ME-ELISA compared with TRYP-ELISA (87.1%, 27/31; 95% CI: 69.2-95.8%) in serum samples from dogs with CVL. When tested with sera from 37 healthy dogs and from 45 dogs with clinical conditions other than CVL, a specificity of 97.6% (80/82; 95% CI: 87.3-98.4%) for DAT and TRYP-ELISA, respectively. Observed agreement was 94.0% (95% CI: 88.7-97.1%) between DAT and β-ME-ELISA (k = 0.879; 95% CI: 0.803-0.956) and 87.4% (95% CI: 80.8-92.1%) between DAT and TRYP-ELISA (k = 0.743; 95% CI: 0.636-0.851). Current results advocate application of the new β-ME-ELISA for diagnosis of CVL at the laboratory level and confirmation of results obtaines with the DAT in field studies.

Key words: Antigen; β –mercaptoethanol; canine visceral leishmaniasis; diagnosis; enzyme-linked immunosorbent assay