Immunomodulation of Patients with Canine Visceral Leishmaniasis at Different Stages: A 12-Month Follow-Up Study Using LaSap

Background/Objectives: Canine visceral leishmaniasis (CVL) is one of the main neglected protozoan diseases in the world. Dogs play a fundamental role in the maintenance of Leishmania infantum in the Americas, and we have already encountered resistance problems with drugs currently used in these animals. Methods: In view of this, two new immunotherapeutic protocols were tested in 48 dogs, using L. amazonensis antigens plus saponin (LaSap) and only L. amazonensis antigens (La) as a control group. Dogs naturally infected with L. infantum were divided into four groups, according to clinical staging. A total of 24 dogs (stages 1 and 2) received a four-dose protocol, and another 24 dogs (stages 3 to 5) received six doses. All animals received a booster dose every three months until they were one year old. Results: Our results showed that dogs in the early stages of the disease respond better and are able to remain stable for longer, maintaining baseline laboratory biomarkers, in addition to having a lower parasite load. Conclusions: On the other hand, dogs in more advanced stages have a poor response, with stage 3 being a key point in clinical progression or regression.