SYNTHETIC PEPTIDE-BASED ENZYME-LINKED-IMMUNOSORBENT-ASSAY FOR SERODIAGNOSIS OF VISCERAL LEISHMANIASIS

Synthetic peptides, derived from the amino acid sequence of a Leishman ia donovani clone, were used to develop an enzyme-linked immunosorbent assay (ELISA) for detecting antibodies against L. donovani. For this purpose, five peptides were conjugated to a protein carrier, human ser um albumin (HSA), by using a heterobifunctional reagent, epsilon-malei midocaproic acid N-hydrolrysuccinimide ester, to obtain a well-defined product. The sensitivity and the specificity of the peptide-specific ELISA were determined with a panel of 106 serum samples from individua ls living in areas where visceral leishmaniasis is endemic; sera from post-kala azar dermal leishmaniasis-infected patients and from individ uals suffering from other infectious diseases were also included. ELIS As were performed with either a single peptide-HSA conjugate, or a mix ture of two peptide-HSA conjugates. Ninety-seven percent of the serum samples from patients with visceral leishmaniasis had detectable antib odies to one or more of the single synthetic peptides. ELISA with a si ngle peptide-HSA conjugate proved to be less sensitive (less than 71%) but more specific (up to 93%) than ELISA with crude promastigote anti gens (80% sensitivity and 79% specificity); when a combination of two different peptide-HSA conjugates was used, the test increased both in sensitivity and in specificity. Chemically defined peptide-protein con jugates improve the reproducibility and reliability of ELISA for the s erodiagnosis of L. donovani infection.