Profiling the myeloid compartment of PBMC in active tuberculosis reveals substantial changes in CD14+ cells and upregulation of CD16 in pro-inflammatory dendritic cells

Abstract Tuberculosis (TB) is the second leading infectious killer after COVID-19 worldwide. Gene expression analysis of whole blood and peripheral blood mononuclear cells (PBMC) from TB infected versus uninfected donors suggests that myeloid cells contribute to the immune signature of TB infection. In this study, we carried out the largest cellular and molecular profiling of the circulating myeloid compartment in the context of Mycobacterium tuberculosis (Mtb) infection to date. Using flow cytometry and RNA sequencing, we isolated and interrogated the transcriptomic profile of myeloid cell subsets isolated from PBMC in a cohort of active TB (ATB) patients with paired sampling at diagnosis and mid-treatment, as well as from Mtb sensitized (IGRA+) and unsensitized (IGRA−) healthy individuals. We identified an increased frequency of CD14+ CD16− and CD14+ CD16+ myeloid cells in ATB at diagnosis with upregulated expression of interferon signaling genes that significantly overlapped with previously reported blood TB signatures. In CD14+ CD16+ cells, there was an additional increased expression of MHC-II related genes, which could be traced down to a subset of pro-inflammatory dendritic cells (DCs), namely CD14+ CD163+ DC3. This cell population significantly upregulated CD16 in ATB at diagnosis, thus displaying a CD14+ CD16+ phenotype, similarly to intermediate monocytes. This result also suggests CD16 might play an important role in inflammatory DC function in ATB. Thus, our study demonstrates quantitative and qualitative changes in CD14+ myeloid cells that are contributing to blood TB signatures. Additionally, it reveals phenotypic overlaps between subsets of monocytes and DCs in human blood that may hold disease relevance. Supported by a grant from NIH (U19 AI118626)