Phenotypic and Functional Profiles of Antigen-Specific CD4⁺ and CD8⁺ T Cells Associated With Infection Control in...

The host immunological response is a key factor determining the pathogenesis of cutaneous leishmaniasis. It is known that a Th1 cellular response is associated with infection control and that antigen-specific memory T cells are necessary for the development of a rapid and strong protective cellular response. The present manuscript reports the analysis of the functional and phenotypic profiles of antigen-specific CD4⁺ and CD8⁺ T cells from patients cured of cutaneous leishmaniasis (CL), patients with an active process of cutaneous leishmaniasis, asymptomatic individuals with a positive Montenegro test and healthy donors (HD). Peripheral blood mononuclear cells (PBMCs) from the patients exhibited a lymphoproliferative capacity after stimulation with total soluble protein from either Leishmania panamensis (SLpA) or Leishmania infantum (SLiA) or with a recombinant paraflagellar rod protein-1 (rPFR1). Higher frequencies of antigen-specific T_NAIVE cells, mainly following stimulation with rPFR1, were observed in asymptomatic and cured patients than in patients with active cutaneous leishmaniasis, while T cells from patients with active cutaneous leishmaniasis showed a higher percentage of effector memory T cells (T_EM for CD4⁺ T cells and T_EMRA for CD8⁺ T cells). The amount of antigen-specific CD57⁺/CD8⁺ T_EMRA cells in patients with active cutaneous leishmaniasis was higher than that in cured patients and asymptomatic subjects. Regarding functionality, a more robust multifunctional CD8⁺ T cell response was detected in cured patients than in those with active cutaneous leishmaniasis. Moreover, cured patients showed a significant increase in the frequency of cells expressing a Th1-type cytotoxic production profile (IFN-γ⁺/granzyme-B/⁺perforin⁺). Patients with an active leishmaniosis process had a significantly higher frequency of CD8⁺ T cells expressing the inhibitory CD160 and 2B4 receptors than did cured patients. The expression profile observed in cured patients could be indicative of an imbalance toward a CD8⁺ Th1 response, which could be associated with infection control; consequently, the determination of this profile could be a useful tool for facilitating the clinical follow-up of patients with cutaneous leishmaniasis. The results also suggest a possible exhaustion process of CD8⁺ T cells associated with the evolution of Leishmania infection.