Immunopathological signatures in congenital tuberculosis-a case-matched study.

Introduction: Congenital tuberculosis (CTB) is a rare and life-threatening condition with a mortality rate of approximately 53% even with clinical intervention, which is markedly higher than that of adult tuberculosis (ATB). To date, the phenotypic and functional characteristics of immune cells in CTB neonates remain largely uncharacterized. Methods: In this case-control study, we enrolled nine CTB neonates and nine paired healthy control (pHC) neonates, collecting basic clinical characteristics of the infants and their mothers, and comparing routine blood test results, C-reactive protein (CRP) levels, and lymphocyte subset profiles via flow cytometry during hospitalization. For exploratory mechanistic investigation, we performed single-cell RNA sequencing (scRNA-seq) on peripheral blood mononuclear cells isolated from one pHC neonate and one CTB neonate at the pre-symptomatic early stage, with additional scRNA-seq data of one ATB patient included for comparative analysis. Results: At the clinical level, CTB neonates exhibited gradual lymphocyte depletion, reduced regulatory T (Treg) cell frequency, and an excessive innate immune response-changes that may drive an overwhelming pro-inflammatory response alongside a compromised adaptive immune response. Exploratory scRNA-seq analysis of the single CTB and pHC neonate revealed a general suppression of immune function in T and natural killer (NK) cells in CTB. T cell subset transcriptomic profiling further showed decreased proportions of Tregs, Th1/17 cells, proliferating T cells, and cytotoxic CD8+ T cells in the CTB neonate, with a concomitant reduction in cytotoxic NK cell frequency. The proportion of myeloid cell subsets in CTB was similar to that in HCs, however, myeloid cells in CTB showed a generally activated inflammatory response. Compared with ATB, myeloid cells of CTB expressed high levels of inflammatory markers. Transcriptomic features of T and NK cell function in the CTB neonate were similar to those in the ATB patient, yet these immune cells in the CTB neonate showed a generally weaker antigen presentation capacity. These preliminary features may partially underpin the high mortality of CTB. Discussion: Notably, the scRNA-seq findings presented here are exploratory and hypothesis-generating, and should be interpreted with caution. Further studies with expanded scRNA-seq cohorts are urgently needed to validate these initial observations and elucidate the core immune pathophysiological mechanisms of CTB.