Evaluation of the cutaneous inflammatory cells in dogs with leishmaniosis and in dogs without the disease that were naturally infected by Leishmania infantum (syn. L. chagasi)

Abstract

Background: Canine leishmaniosis (CanL) is associated with an aberrant cutaneous immune response. Few studies have compared cutaneous immune cells among dogs with leishmaniosis or infected without leishmaniosis, and noninfected dogs. Hypothesis/Objective: Evaluate the number of neutrophils, histiocytes, T lymphocytes, T-bet-positive, GATA3-positive, FoxP3-positive and interleukin (IL)-17-positive cells, in lesional (Group A) and normal-looking (Group B) skin of nine dogs with stage II/III leishmaniosis; in normal-looking PCR-positive (Group C; n = 6) or PCR-negative (Group D; n = 6) skin of infected dogs; and in the normal-looking skin of 12 noninfected dogs (Group E). Methods and materials: Diagnosis of CanL considered clinical signs, clinicopathological abnormalities, detection of Leishmania amastigotes in lymph nodes, and/or bone marrow and positive serological results. Paraffin-embedded skin biopsies were processed for routine immunofluorescence and positive cells were identified using commercially available anti-canine antibodies. Results: In Group A, there was a significantly higher number of neutrophils (P < 0.001), histiocytes (P = 0.012), T lymphocytes (P = 0.011), GATA3-positive (P = 0.02) and IL-17A-positive (P = 0.002) cells compared to Group E. In Group B, there was a significantly higher number of histiocytes (P = 0.02), T lymphocytes (P = 0.004), GATA3-positive (P = 0.006) and FoxP3-positive (P = 0.028) cells compared to Group E. There was no difference in between groups A and B and between groups C or D and E. Conclusions and clinical importance: In the lesional and/or normal-looking skin of dogs with moderate/severe CanL there is an infiltration of neutrophils, histiocytes, T lymphocytes, GATA3-, FoxP3- and IL17A-positive cells. By contrast, the number of these cells is not increased in the normal-looking skin of infected dogs without CanL compared to the skin of noninfected dogs. © 2020 ESVD and ACVD