Detection of Leishmania infantum Infection in Reservoir Dogs Using a Multiepitope Recombinant Protein (PQ10)

Abstract

Mediterranean visceral leishmaniasis is a zoonotic disease caused by <em>Leishmania infantum</em> and transmitted by the bites of infected female sand flies. Iran is one of the endemic areas of this disease. Dogs and canines are the major reservoir hosts of <em>Leishmania infantum</em> in the new and old world, including Iran. If visceral leishmaniasis is left untreated, it may result in a 90% mortality rate. The identification and elimination of infected dogs are efficient ways to control this disease. The diagnostic methods used to identify these animals cannot yield 100% detection. Therefore, in the present study, we used a multiepitope recombinant protein (PQ10) to distinguish between symptomatic and asymptomatic infections caused by <em>Leishmania infantum</em> in animal reservoirs (dogs). The coding sequence of PQ10 recombinant protein was sub-cloned in pET28 expression vector and was commercially synthesized by GENERAY Biotechnology, China. In the following process, sequencing was performed with plasmid-specific primers and followed by the expression, optimization of expression. The purified recombinant protein was confirmed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot. The efficacy of recombinant PQ10 protein was evaluated by an indirect enzyme-linked immunosorbent assay (ELISA) test using 150 dog sera (25 symptomatic positive sera, 25 asymptomatic positive sera, 80 negative sera, and 20 sera of dogs with other infectious diseases). Direct agglutination test (DAT) as the standard method was used to compare and determine specificity and sensitivity. The results indicated that the sensitivity and specificity of ELISA using infected dog sera were 94% and 86%, respectively. Positive and negative predictive values for dog sera were reported as 87.03% and 93.47%, respectively. This protein was able to identify 92% of asymptomatic dogs with visceral leishmaniasis. The results showed that the recombinant protein PQ10 is able to identify positive cases of canine visceral leishmaniasis, especially asymptomatic cases.