Prognostic Value of Immunoglobulin G (IgG) Patterns by Western Blotting Immunodetection in Treated Dogs Previously Infected with <i>Leishmania infantum</i>

Leishmaniasis is a heterogeneous group of neglected tropical diseases with various clinical syndromes, which is caused by obligate intracellular protozoa of the genus <i>Leishmania</i> and transmitted by the bite of a female phlebotomine sandfly. Humans and several animal species are considered as reservoirs of the disease. Among other animal species, dogs are the most important reservoirs in a domestic environment, maintaining the endemic focus of the parasite. The behavior of the disease progression and the clinical symptoms of the disease in the infected dog is mainly associated with depressed cellular immunity and strong humoral response. This study aimed to assess the role of Western blotting in the analysis of the idiotype expression of the two main immunoglobulins (IgG1 and IgG2) in dogs that are naturally infected with <i>Leishmania infantum</i> (<i>L. infantum</i>) and treated with N-methyl meglumine antimoniate. Interestingly, for the first time, our study identified several <i>L. infantum</i> antigen polypeptides (14, 31, 33, 49, 64, 66, 99, and 169 kDa) that more frequently stimulate an immune reaction in recovered dogs after treatment, whereas in the non-recovered group of dogs, four antigen polypeptides of <i>L. infantum</i> with molecular weights of 31, 49, 66, and 115 kDa with unfavorable prognosis were identified. Clearly, these interesting findings confirm the strong association between the detected immunodominant bands and the successful recovery in treated dogs that can be used for differentiating the treated dogs from the untreated dogs, as well as the markers of a favorable or unfavorable prognosis and, as a consequence, the prediction of the clinical outcome of the disease. Likewise, these data could be helpful in the implementation of novel vaccines from the detected antigens.