Methodology for a freshly engineered or cryo-preserved 3D tuberculoma bioplatform for studying tuberculosis biology and high-content screening of therapeutics

Suraj B. Sable^*Allison KlineWen LiJames E Posey

• Centers for Disease Control and Prevention, Atlanta, United States

Tuberculomas are the conglomeration of tuberculous granulomas into structurally organized three-dimensional (3D) masses that result from Mycobacterium tuberculosis infection and represent one of the more severe morphological forms of tuberculosis (TB). Several in vitro models that mimic human TB granulomas have been reported to decipher complex host-pathogen interactions and to discover new prophylactic and therapeutic interventions. They serve as ethical bridge approaches to human studies. However, these models need improvements in generating well-organized granuloma lesions, classic tuberculoma structures, and relevant microenvironments. They are impractical for screening extensive chemical and genetic libraries owing to their low throughput, limited scalability, batch-to-batch variability, and high costs. Here, we describe a 'mycobacteria-in-spheroid' co-culture workflow in a standard 96-well plate format that generates a robust 3D cell culture model. This model reproduces key attributes and microenvironments in human tuberculomas and can be scaled up as a high-throughput screening (HTS)-compatible bioplatform. The tuberculoma-like structures generated encompass organized, florid granulomatous foci and exhibit solid, necrotic, and cavitary morphologies. This model can be developed using freshly isolated human primary cells or a monocytic cell line with virulent mycobacteria. The platform combines the entire workflow, from generation to imaging of tuberculoma-like structures, in situ. It permits the serial quantitation of drug efficacy and monitoring of lesion resolution over several days to weeks following a single treatment. Additionally, we outline a methodology for adopting this workflow for cryo-preservation, enhancing its potential for commercial application. The ease of generation, pliability, cryo-shelf stability, and reproducibility of the bioplatform make it ideal for HTS applications and for implementation in discovery programs for TB and other granulomatous diseases.