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Dynamic Interplay of Th1/Th17 Immunity and Antimicrobial Gene Expression in Leprosy Skin Lesions

ABSTRACT: Reversal reactions (RR) in leprosy provide a unique opportunity to study the dynamics of the immune response against intracellular bacteria in humans. We performed RNA sequencing on paired skin biopsy specimens from nine leprosy patients before and during RR, identifying a 64-gene antimicrobial response signature that correlated with the concomitant decrease in Mycobacterium leprae bacilli in RR patients. The upstream regulators of this antimicrobial gene signature included both innate (IL-1β, TNF) and adaptive (IFN-γ, IL-17) cytokines, indicating induction of both Th1 and Th17 responses. By using a machine learning classifier to identify proteins with predicted membrane-permeating activity, we identified 28 additional antimicrobial genes including S100A8. We validated the antimicrobial activity of four proteins (S100A7, S100A8, CCL17, CCL19) against M. leprae in infected macrophages and axenic culture. Scanning electron microscopy revealed distinct morphological changes in bacterial membranes upon exposure to these antimicrobial proteins. Our findings illuminate the dynamic regulation of antimicrobial gene expression as part of the innate and adaptive immune response against M. leprae and identify new potential antimicrobial effectors in human host defense. These insights underscore the potential for therapeutic strategies aimed at enhancing Th1 and Th17 cell function to improve outcomes in mycobacterial infection in humans.

ORGANISM(S): Homo sapiens

PROVIDER: GSE280021 | GEO | 2024/12/21

REPOSITORIES: GEO

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Project description:The immune mechanisms that control resistance vs. susceptibility to mycobacterial infection in humans were investigated by studying leprosy skin lesions, the site where the battle between the host and the pathogen is joined. Using an integrative genomics approach, we found an inverse correlation between of IFN-beta and IFN-gamma gene expression programs at the site of disease. The Type II IFN, IFN-gamma and its downstream vitamin D-dependent antimicrobial genes were preferentially expressed in the lesions from patients with the self-healing tuberculoid form of the disease and mediated antimicrobial activity against the pathogen, Mycobacterium leprae in vitro. In contrast, the Type I IFN, IFN-beta and its downstream genes, including IL-27 and IL-10, were induced in monocytes by M. leprae in vitro, and were preferentially expressed in the lesions of disseminated and progressive lepromatous form. The IFN-gamma induced macrophage antimicrobial response was inhibited by IFN-beta/IL-10, by a mechanism involving blocking the generation of bioactive 1,25-dihyroxy vitamin D as well as inhibiting induction of antimicrobial peptides cathelicidin and DEFB4. The ability of IFN-M-oM-^AM-" to inhibit the IFN-gamma induced vitamin D pathway including antimicrobial activity was reversed by neutralization of IL-10, suggesting a possible target for therapeutic intervention. Finally, a common IFN-beta and IL-10 gene signature was identified in both the skin lesions of leprosy patients and in the peripheral blood of active tuberculosis patients. Together these data suggest that the ability of IFN-beta to downregulate protective IFN-gamma responses provides one general mechanism by which some bacterial pathogens of humans evade protective host responses and contribute to pathogenesis. Peripheral blood monuclear cells derived through Ficoll-Hypaque from the blood of healthy human donors (n=4). Cells adhered to tissue culture treated 6-well plates for 2 hours in 1% Fetal Bovine Serum (FBS) RPMI and then stimulated by IL-10 (R&D Systems) 10ng/ml or media alone in 10% FBS RPMI for 24 hours at 37M-BM-0C, 5% CO2. After stimulation, cells harvested and monocytes isolated through CD14 positive selection (Miltenyi Biotec). RNA from purified monocytes extracted by Trizol and purified by Qiagen RNeasy Kit. RNA probe and microarray performed by UCLA Clinical Microarray Core using Ambion labeling kit and Affymetrix Human U133 Plus 2.0 array.