Abstract Background Canine leishmaniasis caused by Leishmania infantum is recognized as one of the most important neglected vector-borne diseases of zoonotic concern worldwide. Cats may also be infected with L. infantum , though the mechanisms underlying the immune response to this protozoal infection in the feline host remain poorly understood. In this study, the early cytokine gene-expression profile was investigated by in vitro infection of feline monocyte-derived macrophages with L. infantum . Methods Primary macrophages were matured from peripheral blood mononuclear cells of a healthy domestic cat, and cells were collected at different time points post-infection (i.e., 4, 24, and 72 h) for microscopic evaluation and quantitative real-time PCR analysis of cytokine expression interleukin (IL)-2, IL-4, IL-6, IL-10, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α. Results Infection rates ranged from 35.6% to 48.2%, with 2.1–2.4 intracellular parasites per infected cell. Gene-expression analysis revealed a marked upregulation of IL-2, IFN-γ, and TNF-α at 72 h, indicating a predominant Th1-type pro-inflammatory response, while IL-4, IL-6, and IL-10 remained stable or slightly downregulated. Conclusions These findings provide unprecedented evidence that feline macrophages activate a Th1-like cytokine pattern following in vitro infection with L. infantum . Overall, the outcomes of this investigation support the hypothesis that, when compared with dogs, the milder clinical course of leishmaniasis in cats is related to a predominant Th1-like immune response, eventually contributing to the infection control in naturally infected animals. Graphical Abstract
Louzada-Flores et al. (Sat,) studied this question.