The effect of BCG vaccination in immune responses against visceral leishmaniasis in a natural (canine) model of infection
Visceral leishmaniasis (VL) is the most severe clinical form of leishmaniasis due to frequent complications and the risk of developing into untreated death. It is a zoonosis with high prevalence and wide distribution by the world. In urban areas, the dog is considered the main reservoir of VL due to its close relationship with humans. Canine disease is also considered valuable for the understanding of human disease, since the clinical presentation in both species show similarities.
Several drugs have been used in the treatment of VL; however, some of them are not recommended by the world health organization for use in veterinary medicine, in order to avoid the parasite’s resistance to active principles. Immunotherapy involves the use of biological substances or molecules to modulate immune responses in order to achieve prophylactic and / or therapeutic success. Immunotherapy with or without chemotherapy has been used for the treatment of leishmaniasis. Several studies have described that the use of immunotherapy helps to reduce the clinical signs, the dose of drugs and the time of the treatment.
The BCG vaccine is widely used to prevent tuberculosis and originates from attenuated strains of Mycobacterium bovis. The main mechanism of action of BCG induced protection has been described as mediated by Th-1 cells. The BCG vaccine has been studied as a possible immunotherapeutic for the control of leishmaniasis. Studies with murine models have shown that the use of BCG associated with conventional treatment helps to reduce the parasite burden, the severity of clinical manifestations, and helps increasing the resistance of macrophages to infection, also increasing the capacity of these cells to kill the parasite.
The present study aims to evaluate the effects of BCG vaccination administration on the clinical presentation and parasite load of naturally infected dogs from an area endemic for visceral leishmaniasis.
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