Immunoprophylactic Potential of a New Recombinant Leishmania infantum Antigen for Canine Visceral Leishmaniasis: An In Vitro Finding.

The development and application of safe and effective immunoprophylactic/immunotherapeutic agents against canine visceral leishmaniasis (CanL) have been pointed out as the only means for the real control of the disease. Thus, this study aimed to evaluate the in vitro cellular immune response of dogs, elicited by the new recombinant proteins of Leishmania infantum, Lci10 and Lci13, in order to investigate their potential for vaccinology. Twenty-four dogs were submitted to clinical, parasitological, serological and molecular tests, and then separated into two study groups: 12 infected (InD) and 12 non-infected dogs (NInD), and six of each group were directed for Lci10 and Lci13 evaluation. Peripheral blood mononuclear cells (PBMC) were cultured and stimulated with Lci10 (10 µg/ml) or Lci13 (5 µg/ml), and with L. infantum soluble antigen (LSA) (25 µg/ml) or no stimulus (NS) as controls. Afterwards, the mRNA levels of different cytokines were quantified through qPCR, and Nitric Oxide (NO) production was assessed in the culture supernatants. Significant differences were considered when p ≤ 0.05. The comparative analysis revealed that, in the NInD group, Lci13 promoted a significant increase in the expression of IFN-γ in relation to LSA (p = 0.0362), and the expression of this cytokine in NInD was significantly higher than that presented in the InD (p = 0.0028). A negative expression for TGF-ß was obtained in both groups. Lci13 also induced a greater production of NO in relation to the NS sample in the NInD group. No significant differences were observed after stimulation with Lci10. In conclusion, the results suggest a protective role of Lci13 for uninfected animals, thus with a potential for immunoprophylaxis. The results will help to direct the antigen Lci13 for further studies (pre-clinical trials), in order to determine its immunogenicity and reactogenicity effects, as a way to consolidate its real applicability for vaccinology against CanL.

The diagnosis of canine visceral leishmaniasis in Brazil: Confronting old problems.

In Brazil, the main strategy adopted to contain Visceral Leishmaniasis (VL) is the controversial culling of dogs with reagent serology for Canine VL (CVL). Despite there are studies showing that significant reduction of human cases has not been observed, as well as there are works demonstrating the occurrence of false-positive results in the confirmatory test, the protocol has been maintained. Researches that can reinforce the existence and persistence of this problem, as well as bring concrete alternatives are pivotal. In this context, the aim of this work was to evaluate and compare the serological, molecular and parasitological methods employed for CVL detection in Brazil, in dogs with diverse clinical profiles, from two endemic areas of Pernambuco state. Comparisons among TR-DPP®, EIE-LVC and qPCR (animals from Goiana-PE: 91) demonstrated that agreements varied from 'poor' to 'moderate' (kappa = 0.162-0.442), and a triple agreement occurred in 61.36% (54/88) of the samples. The highest percentage of agreement was obtained between TR-DPP® and EIE-LVC within the polysymptomatic group (93.33%; 14/15). Of the 34 dogs with reagent serology from Caruaru-PE, 17 (50%) and 29 dogs (85.29%) were positive for qPCR and parasitological exam, respectively. By comparing serology, qPCR and parasitological exam, the lowest percentage of agreements were obtained within the asymptomatic group (40%-72.72%). It was possible to observe that the percentage of agreement tended to decrease according to the absence of clinical manifestations in the dogs. Thus, from the fact that all diagnostic tools evaluated have their limitations, it is very important to be careful before to propose an alternative set of diagnostic criteria. Besides, the answer for better results in the control of CVL may not be in the choose of the best set of diagnostic tools, but it may be in the strategy of culling itself. In this context, it is very important to invest in alternative control measures, such as mass vaccination and treatment of dogs, thus reducing the transmission to the vector and helping to avoid new canine and human cases.