Characterization of genital system inflammatory response in female dogs naturally infected with Leishmania infantum.

The genital system of female dogs with visceral leishmaniasis (VL) commonly shows lesions on the external genitalia (vulva and vagina). This study aimed to evaluate the inflammatory response in segments of the reproductive tract of female dogs naturally infected with Leishmania infantum, and to correlate these findings with hormonal status (high or low progesterone levels), local parasitism, and local inflammatory infiltrate immunophenotype. Sixteen unspayed, non-pregnant adult female dogs naturally infected with L. infantum, without any other disease, were used. Animals were divided into two groups: G1 (n = 5, high-progesterone phase) and G2 (n = 11, low-progesterone phase). Parasite presence and the immunophenotype of leukocytes infiltrating the genital system (CD3, CD4, CD8, and MCA874) were determined by immunohistochemistry. Chronic inflammatory infiltrate was the predominant lesion and was mainly found in the vulva and vagina. Internal genitalia segments (cervix, uterus, ovary) presented fewer lesions. Animals of G1 group exhibited higher number of immunolabeled parasites in the internal segments of the reproductive tract and of cells positive for CD3 (T lymphocytes) and MCA874 (macrophages) than G2 group. There was no difference for CD4 and CD8 between groups. However, multivariate analysis showed positive correlations with T lymphocyte subtypes, macrophages, and parasite presence in different segments of the reproductive tract of G1 animals. Leukocyte population and number of parasitized cells in the reproductive tract increased with escalating progesterone levels (G1 group), suggesting that estrus and diestrus stages are most favorable to infection maintenance.