IL-32 producing CD8+ memory T cells and Tregs define the IDO1 / PD-L1 niche in human cutaneous leishmaniasis skin lesions.

Human cutaneous leishmaniasis (CL) is characterised by chronic skin pathology. Experimental and clinical data suggest that immune checkpoints (ICs) play a crucial role in disease outcome but the cellular and molecular niches that facilitate IC expression during leishmaniasis are ill-defined. We previously showed that in Sri Lankan patients with CL, indoleamine 2,3-dioxygenase 1 (IDO1) and programmed death-ligand 1 (PD-L1) are enriched in lesion skin and that reduced PD-L1 expression early after treatment onset predicted cure rate following antimonial therapy. Here, we use spatial cell interaction mapping to identify IL-32-expressing CD8+ memory cells and regulatory T cells as key components of the IDO1 / PD-L1 niche in Sri Lankan CL patients and in patients with distinct forms of dermal leishmaniasis in Brazil and India. Furthermore, the abundance of IL-32+ cells and IL-32+CD8+ T cells at treatment onset was prognostic for rate of cure in Sri Lankan patients. This study provides a unique spatial perspective on the mechanisms underpinning IC expression during CL and a novel route to identify additional biomarkers of treatment response. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by funding from the UK Medical Research Council / UK Aid Global Challenges Research Fund (MR/P024661/1 to PMK, SR, HG, and MC), a Wellcome Trust Senior Investigator Award (WT104726 and WT224290 to PMK) and Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (2018/14398-0) and fellowship (2019/25393-1) to HG. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Written informed consent including for lesion photographs was obtained from participants under a protocol for the project titled Towards a global research network for the molecular pathological stratification of leishmaniasis approved by Ethical Review Committee of the Faculty of Medical Sciences, University of Jayewardenepura (ref: 780/13 & 52/17), Ethics Committee of the Faculdade de Medicina, Universidade de Sao Paulo- CAAE 39964520.8.0000.0068, Institutional Ethics Committee of School of Tropical Medicine, Kolkata and Institute of Post Graduate Medical Education and Research, Kolkata (IPGME&R/IEC/2019/208) and the Biology Ethics Committee (ref: PK201805), Department of Biology, University of York. This study was conducted according to the Declaration of Helsinki (2013). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data availability The sequencing data reported in this paper have been deposited in the GEO database under the accession code GEO: TBC. The processed sequencing data is available as Rds files on Zenodo: https://doi.org/10.5281/zenodo.10402126. Additional data (Supplementary Table 4) related to the figures is also available on figshare (DOI: https://doi.org/10.6084/m9.figshare.24803511). Code availability Code used for analysis (including that for generating Figs from Visium seq data and CosMx imaging data) in this study is available at https://github.com/NidhiSDey/leish-ME