How canine leishmaniosis and treatment affect dog immune cells

Abstract

Dogs are a major reservoir of, etiological agent of canine leishmaniosis (CanL) a zoonotic visceral disease of worldwide concern. Therapeutic protocols based on antileishmanial drugs are commonly used to treat sick dogs and improve their clinical condition. To better understand the impact ofinfection and antileishmanial drugs on the dog's immune response, this study investigates the profile of CD4and CD8T cell subsets in peripheral blood, lymph node, and bone marrow of sick dogs and after two different CanL treatments. Two CanL groups of six dogs each were treated with either miltefosine or meglumine antimoniate combined with allopurinol. Another group of 10 clinically healthy dogs was used as control. Upon diagnosis and during the following 3 months of treatment, peripheral blood, popliteal lymph node, and bone marrow mononuclear cells were collected, labeled for surface markers CD45, CD3, CD4, CD8, CD25, and intracellular nuclear factor FoxP3, and T lymphocyte subpopulations were immunophenotyped by flow cytometry. CanL dogs presented an overall increased frequency of CD8and CD4CD8double-positive T cells in all tissues and a decreased frequency of CD4T cells in the blood. Furthermore, there was a higher frequency of CD8T cells expressing CD25FoxP3in the blood and bone marrow. During treatment, these subsets recovered to levels similar to those of healthy dogs. Nevertheless, antileishmanial therapy caused an increase of CD4CD25FoxP3T cells in all tissues, associated with the decrease of CD8CD25FoxP3T cell percentages. These findings may support previous studies that indicate thatmanipulates the dog's immune system to avoid the development of a protective response, ensuring the parasite's survival and the conditions that allow the completion oflife cycle. Both treatments used appear to have an effect on the dog's immune response, proving to be effective in promoting the normalization of T cell subsets.