Altered IL-7 signaling in CD4+ T cells from patients with visceral leishmaniasis

• Published in: PLoS neglected tropical diseases 2024-02, Vol.18 (2), p.e0011960-e0011960
• Main Authors: Kumar, Shashi, Chauhan, Shashi Bhushan, Upadhyay, Shreya, Singh, Siddharth Sankar, Verma, Vimal, Kumar, Rajiv, Engwerda, Christian, Nylén, Susanne, Sundar, Shyam
• Format: Article
• Language: English
• Subjects: Biology and Life Sciences; Bone marrow; CD38 antigen; CD4 antigen; CD4-Positive T-Lymphocytes; Cell activation; Cells; Cytokines; Down-regulation; Effector cells; Flow cytometry; Gene expression; Homeostasis; Humans; Interleukin 7; Kinases; Leishmaniasis, Visceral - parasitology; Lymphocytes; Lymphocytes T; Macrophages; Medical research; Medicine and Health Sciences; Parasite control; Parasites; Parasitic diseases; Patients; Peripheral blood; Phosphorylation; Plasma; Plasma levels; Protein expression; Proteins; Protozoa; Recombinants; RNA, Messenger - genetics; Signal Transduction; Software; Stat5 protein; Stimulation; Vector-borne diseases; Visceral leishmaniasis; γ-Interferon
• ISSN: 1935-2735; 1935-2727; 1935-2735
• DOI: 10.1371/journal.pntd.0011960

CD4+ T cells play a central role in control of L. donovani infection, through IFN-γ production required for activation of macrophages and killing of intracellular parasites. Impaired control of parasites can in part be explained by hampered CD4+ T cells effector functions in visceral leishmaniasis (VL) patients. In a recent studies that defined transcriptional signatures for CD4+ T cells from active VL patients, we found that expression of the IL-7 receptor alpha chain (IL-7Rα; CD127) was downregulated, compared to CD4+ T cells from endemic controls (ECs). Since IL-7 signaling is critical for the survival and homeostatic maintenance of CD4+ T cells, we investigated this signaling pathway in VL patients, relative to ECs. CD4+ T cells were enriched from peripheral blood collected from VL patients and EC subjects and expression of IL7 and IL7RA mRNA was measured by real time qPCR. IL-7 signaling potential and surface expression of CD127 and CD132 on CD4+ T cell was analyzed by multicolor flow cytometry. Plasma levels of soluble IL-7 and sIL-7Rα were measured by ELISA. Transcriptional profiling data sets generated previously from our group showed lower IL7RA mRNA expression in VL CD4+ T cells as compared to EC. A significant reduction was, however not seen when assessing IL7RA mRNA by RT-qPCR. Yet, the levels of soluble IL-7Rα (sIL-7Rα) were reduced in plasma of VL patients compared to ECs. Furthermore, the levels of soluble IL-7 were higher in plasma from VL patients compared to ECs. Interestingly, expression of the IL-7Rα protein was higher on VL patient CD4+ T cells as compared to EC, with activated CD38+ CD4+ T cells showing higher surface expression of IL-7Rα compared to CD38- CD4+ T cells in VL patients. CD4+ T cells from VL patients had higher signaling potential baseline and after stimulation with recombinant human IL-7 (rhIL-7) compared to EC, as measured by phosphorylation of STAT5 (pSTAT5). Interestingly, it was the CD38 negative cells that had the highest level of pSTAT5 in VL patient CD4+ T cells after IL-7 stimulation. Thus, despite unaltered or potentially lowered IL7RA mRNA expression by CD4+ T cells from VL patients, the surface expression of the IL-7Rα was higher compared to EC and increased pSTAT5 was seen following exposure to rhIL-7. Accordingly, IL-7 signaling appears to be functional and even enhanced in VL CD4+ T cells and cannot explain the impaired effector function of VL CD4+ T cells. The enhanced plasma IL-7 may serve as part of hom