Sensitive and Specific Serodiagnosis of Leishmania infantum Infection in Dogs by Using Peptides Selected from Hypothetical Proteins Identified by an Immunoproteomic Approach

In Brazil, the percentage of infected dogs living in areas where canine visceral leishmaniasis (CVL) is endemic ranges from 10 to 62%; however, the prevalence of infection in dogs is probably higher than figures reported from serological studies. In addition, problems with the occurrence of false-positive or false-negative results in the serodiagnosis of CVL have been reported. The present work analyzed the potential of synthetic peptides mapped from hypothetical proteins for improvement of the serodiagnosis of Leishmania infantum infection in dogs. From 26 identified leishmanial proteins, eight were selected, considering that no homologies between these proteins and others from trypanosomatide sequence databases were encountered. The sequences of these proteins were mapped to identify linear B-cell epitopes, and 17 peptides were synthesized and tested in enzyme-linked immunosorbent assays (ELISAs) for the serodiagnosis of L. infantum infection in dogs. Of these, three exhibited sensitivity and specificity values higher than 75% and 90%, respectively, to differentiate L. infantum-infected animals from Trypanosoma cruzi-infected animals and healthy animals. Soluble Leishmania antigen (SLA) showed poor sensitivity (4%) and specificity (36%) to differentiate L. infantum-infected dogs from healthy and T. cruzi-infected dogs. Lastly, the three selected peptides were combined in different mixtures and higher sensitivity and specificity values were obtained, even when sera from T. cruzi-infected dogs were used. The study's findings suggest that these three peptides can constitute a potential tool for more sensitive and specific serodiagnosis of L. infantum infection in dogs.