ABSTRACT
Control of canine visceral leishmaniasis (CVL), a major zoonotic disease in Brazil and many other tropical and subtropical countries, remains difficult as an accurate and reliable diagnosis is still missing. In endemic regions, infected dogs are the main parasitic reservoir host of human Visceral leishmaniasis (VL) infection. Vaccination of dogs against Leishmania infection constitutes an important strategy to prevent or to better control CVL, thus, a serological test that can discriminate between antibodies induced by immunization versus infection is highly desirable in order to improve and simplify diagnosis. Here, four recombinant proteins were evaluated for their ability to detect and differentiate between dogs that are infected with Leishmania or have been immunized with the anti-Leishmania vaccine Leish-Tec®. Receiver operating characteristic (ROC) curve analysis of the four Leishmania-specific IgG ELISA revealed superior performance of rK28, followed by rKLO8, rK39 and rLb6H. The rK28-based ELISA revealed not only the best accuracy against CVL, but also the lowest cross-reactivity with sera from Leish-Tec® immunized dogs. Our data show that the rK28-based ELISA is highly suitable for CVL screening as it shows high sensitivity with simultaneous low cross-reactivity. Further, the high specificity of the rKLO8 indicates its suitability for the confirmation of CVL diagnosis.
ABSTRACT
Canine visceral leishmaniasis (CVL) represents an important public health issue. Despite numerous diagnostic tests available, CVL diagnosis still needs to be improved to achieve a more accurate detection rate. Recently, rKLO8, a new antigenic protein of Sudanese Leishmania donovani, was studied for the first time in diagnosis of human visceral leishmaniasis (HVL) and showed good performance. The present study aimed to evaluate serum reactivity to rKL08 and the reference antigen rK26, and to compare both diagnostic proteins with the combined DPP® CVL rapid test and ELISA (EIE-Bio-Manguinhos) confirmatory test, which are both recommended for the diagnosis of CVL in Brazil. Serum samples of dogs were grouped into: (I) DPP®/EIE negative (n=100) and (II) DPP®/EIE positive sera (n=100). Enhanced levels of IgG, mainly IgG2, to both rKLO8 and rK26 were found in group II. Sensitivity was 68% and 77% and specificity was 92% and 91%, for rKLO8 and rK26 antigens, respectively. Moreover, the combination of rKLO8 and rK26 antigens (rKLO8+rK26) exhibited higher sensitivity (85%) and specificity (93%). Thus, our results show that apart from the improved diagnostic power of rKLO8 in HVL, this new antigen is also suitable for the diagnosis of CVL. Further, the combination of rKLO8 and rK26 antigens increases the diagnostic accuracy of CVL.
