Tuberculosis Imaging Program

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications, trials & patents

Abstract

This core program focuses on supporting intermural program investigators as they ask important questions about human diseases like tuberculosis and the immunopathology that develops during disease. We assist them using our optimized procedures including PET/CT imaging for monitoring disease progression while conducting a variety of chemotherapeutic testing and basic immunology experiments using Mycobacterium tuberculosis (Mtb) infection models like rhesus macaques, NZW rabbits, and common marmosets. We have also optimized the imaging of mice on the LFER scanners to fulfill the need in the Tuberculosis Research Section (TRS), but because of the resolution and speed of the unit, it is not ideal for mice. We developed new skills during this year including intratracheal inoculation for infection of both mice and rabbits as well as bronchoalveolar lavage of rabbits and marmosets for recovering immune cells. We have worked with two research groups to work toward AI or ML analysis of the Mtb infected animal scans. The group’s approaches work for “whole lung” identification and analysis of the abnormal voxels in the lung images rival trained readers. The next step is to work toward tracking individual lesions across multiple time points. The experiments in 2025 included rabbit, marmoset, and mouse infections with Mtb with TRS to examine the efficacy of potential anti-tubercular compounds or their penetration into MTB lesions where the bacteria reside (1, 2) and we continued to work on the development of the [18F]2 fluor deoxy trehalose (FDT) probe to support an IND application for use in humans. We also continued to support investigation of the role of a Mtb secondary metabolite in disease progression through a series of infections in different strains of knockout mice. We undertook several experiments to increase the frequency of cavities among the lesions that marmosets form after Mtb infection to better understand this important pathologic feature of human disease. In one approach among several, we BCG-vaccinated a group of the marmosets and monitored them for both disease development and cavity formation. As marmosets had not been vaccinated with BCG previously, we undertook several preliminary experiments to confirm that BCG would not cause BCG-osis in the species and that the animals would develop antigen-specific T cells from the exposure. In a collaboration among TRS, T-cell biology section (TBS), and Spatial Immunology Unit (SIU) scientists, we found that marmosets both survived longer and had lower bacterial loads if vaccinated but did not appear to make more cavities. Several interesting features of the marmoset’s immunologic response are being investigated by the SIU. Other approaches to generate cavities are ongoing. Two long term (~ 6 months) and one short term experiment involving Mtb infection of rhesus macaques followed by two different immunological manipulations of the animals in comparison to non-manipulated controls were completed in 2025 with the T-cell biology section (TBS). The analysis of these experiments using advanced genetic methods are ongoing, but the results demonstrate that Mtb disease progression is dependent the presence of many cell types and the cytokines they produce. Perturbing the balance of those cells and their signaling can change the course of disease drastically. In addition, we have continued to work with extramural partners to assist in the analysis of their imaging data from Mtb-infected animals and we have assisted our Vaccine Research Center collaborators with initiating Mtb infections in a local contract research facility – providing diluted and titered bacteria stocks, detailed anesthesia procedures, imaging advice and scan review, and in situ hands-on necropsy training for anatomy and pathology identification. Some specific projects where we have contributed to the work and that have been recently published are mentioned below: Last year we assisted TRS reporting that [18F]FDT could function as a mechanism-based reporter of mycobacteria-selective enzyme activity in vivo (PMID: 38937448). We are completing some further characterization of the tracer to build a case for its use in clinical assessment of TB disease in clinical studies. Toward this goal, in 2024 we monitored marmoset disease progression with FDT and observed that FDT uptake increased as disease progressed and we have shown a clear correlation between FDT retention in tissues and their bacterial content. In 2025, we have treated infected marmosets with anti-TB drugs and monitored treatment response with FDT to determine the lower limit of detection, and we are following some drug-treated marmosets for disease recrudescence to assess if FDT is useful in detecting relapse of tuberculosis. This project with TRS and the Gates foundation is ongoing. In the rabbit model of Mtb infection, we have investigated methods to promote cavity frequency and development in the rabbits. The analysis of the experiment is ongoing, but the cavity material collected has contributed to both cavity characterization with TRS and drug penetration analysis with collaborators. In one such study we used the resulting cavity caseum in ex vivo assays to investigate the potency of several classes of gyrase inhibitors against Mtb (1). In contrast to fluoroquinolones, many other gyrase inhibitors kill only replicating bacterial cultures but produce negligible cidal activity against Mtb. In contrast, fluoroquinolones were unique in their ability to cleave double-stranded DNA at low concentrations, killing Mtb in both replicating and nonreplicating, persistent states. In addition, working with the same collaborators, we investigated the penetration of bedaquiline, and two next generation diarylquinolines TBAJ587 and TBAJ876, in the necrotic center (caseum) of rabbit cavities in vivo through multiday dosing (2). Laser-capture microdissection of the lesions facilitated mapping of drug concentrations as a function of distance from blood supply in caseous lesions. Simulations revealed that bedaquiline reached steady state and efficacious concentrations in deep caseum after several weeks to months in comparison only hours or a few days with the newer compounds. These results predict that Mtb will have less likelihood of developing resistance to the newer compounds since the window of subtherapeutic exposure is likely to be less. As part of our prior assistance to the TBU and LVD, we infected rhesus macaques with SARS-CoV-2 and monitored the animals over several weeks with FDG PET/CT and collection of blood, other fluids and stool samples prior to sacrifice and detailed necropsy. Analysis of the colonic epithelium and plasma samples demonstrated that GI perturbations such as microbial translocation can occur in even mild SARS-CoV-2 infections. Interlukin-6 and soluble CD14 were observed to be elevated during infection and in combination with the leaked microbial products may contribute to the COVID-19 inflammatory state (3). We contributed to other publications (4, 5) and have several ongoing collaborations that have manuscripts in review.