Cellular and molecular architecture of granulomas in human tuberculous lymphadenitis - ABSTRACT Tuberculous lymphadenitis (TBL) is the most frequent form of extrapulmonary of TB affecting approximately 2000 individuals in Tunisia annually, such that the disease is a clinical burden on the Tunisian health care system. Since the occurrence of concomitant pulmonary TB in TBL patients is infrequent, and bacilli are rarely detected by microscopy, TBL represents a form of TB in which the infection is controlled and not yet disseminated, except in immunocompromised individuals. TBL in Tunisia is generally caused by Mycobacterium bovis or M. tuberculosis, yet cannot be distinguished clinically, radiographically, or pathologically. The histologic hallmark of TB is the granuloma, an organized collection of macrophages, lymphocytes, and other cell types that function to contain and kill invading pathogens. Here, we will test the hypothesis that elucidation of the cellular and molecular architecture of TBL granulomas will lead to the identification of disease biomarkers and insight into the mechanisms by which T cell responses regulates antimicrobial responses in granulomas. We propose to study the cellular and molecular architecture of granulomas in TBL by integrating single cell RNA-sequencing (scRNA-seq) with spatial-seq of lymph node specimens that are obtained as part of routine clinical care. This project brings together scientists from the Benabdessalem lab at the Institut Pasteur de Tunis (IPT) with scientists from UCLA, who have already collaborated to generate preliminary data measuring the spatial distribution of cell types and genes in pulmonary TB and TBL granulomas. In Aim 1, we will determine the cellular and molecular architecture of TBL granulomas, identifying biomarkers related to antimicrobial responses that correlate with the causative agent, M. bovis vs. M. tuberculosis, as well as comparing the response in TBL to pulmonary TB. In Aim 2, we will determine the contribution of T cells to control the infection in TBL granulomas through antimicrobial responses, including relevant correlates to specific mycobacterial antigens in peripheral blood. Together, these studies will provide new insight into the mechanisms by which the intersection of T cell responses and granuloma organization impacts host control of M. bovis vs. M. tuberculosis infection. As such, our studies of the specific immune biosignatures in TBL will expand our understanding of its immunopathogenesis, leading to improved care for patients with TBL. An important part of this application is to ensure transfer of technology and research training from the Modlin lab at UCLA to the Benabdessalem lab at IPT.
