Tuberculosis Imaging Program

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications & trials

Abstract

The major activities of this research project in the past have centered around using our optimized methods and procedures for imaging rhesus macaques, NZW rabbits, and common marmosets on PET/CT scanners while conducting a variety of chemotherapy and basic immunology experiments in Mtb models. We have begun to optimize the imaging of mice on the LFER scanner to fulfill the need in the TRS, but because of the resolution and speed of the unit, it is not ideal for mice. The experiments in 2021 included various Mtb infections of rhesus macaques with TBU and IIIU. Rabbit (2), marmoset (3) and mouse infections (3) with Mtb with TRS. And most recently, Mtb infection of rhesus with the VRC lab CIS. In addition, we have conducted two larger Sars CoV-2 infection experiments in rhesus macaques with the TBU. As we have more than 10 years of data and multiple publications using CT Hounsfield unit (HU)density ranges and PET FDG uptake values as descriptive and quantitative features for tuberculosis lesions, we have made systematic study of the quantitative differences in images collected on the previous small clinical CT scanner and the new scanner (LFER). In 2020, our licensed technologist worked with a company using NEMA certified materials to design a new CT phantom appropriate for modeling the monkey chests. The new linear slope calculations indicate the Ceretom CT and the Mediso unit have differing y intercepts. After rerunning these tests, the optimal technique for mimicking a clinical scanner available on the LFER was 80 kVp, 980 uA, 80 ms (65.6 As) for the rhesus and the rabbit. Scans using this technique were collected and analyzed with specific attention to the HU ranges where lesions were identified, and lesion tissue was found to have HU distributed from -550 to 100 HU with very few voxels above 100 HU. When possible, we applied an automated method that segregates low- and high-density ranges using a whole lung technique. This approach allowed us to monitor disease changes closely and accurately when individual lesions were very difficult to separate in the CT images. The optimal FDG dose for each animal species (relative to their weight in Kg) has been determined as well. Our analysis of PET images has been based on changes in total activity in the lung, changes in dense tissue which corresponds to diseased areas or changes in individual lesions over time depending on the type of experiment. We observed some disease differences that caused us to modify our HU and baseline PET settings for Sars Cov-2 disease analysis. Some specific projects that are published are mentioned below. We have conducted experiments where BAL fluid and blood was collected regularly from Mtb infected macaques so that IIIU researchers could determine the kinetics of the various innate effector cells in the blood and on airway surfaces during progressive infection. They uncovered an unexpected association between eosinophils and Mtb infection. In humans with refractory tuberculosis, eosinophils were decreased in the blood but enriched in resected human lung lesions and autopsy granulomas. An influx of eosinophils was also evident in infected zebrafish, mice, and nonhuman primate granulomas, where they were functionally activated and degranulated (PMID: 34347010). We collaborated with the TBU to examine the role of PD-1 during Mycobacterium tuberculosis (Mtb) infection of rhesus macaques. Animals treated with anti-PD-1 monoclonal antibody developed worse disease as shown by PET/CT and higher granuloma bacterial loads compared with isotype control-treated monkeys (PMID: 33452107). PD-1 blockade increased the number and functionality of granuloma Mtb-specific CD8 T cells. In contrast, Mtb-specific CD4 T cells in anti-PD-1-treated macaques were not increased in number or function in granulomas, expressed increased levels of CTLA-4, and exhibited reduced intralesional trafficking in live imaging studies. In granulomas of anti-PD-1-treated animals, multiple proinflammatory cytokines were elevated, and more cytokines correlated with bacterial loads. Therefore, PD-1-mediated coinhibition is required for control of Mtb infection in macaques, perhaps because of its role in dampening detrimental inflammation. The TBU has previously shown that MAIT cells expand during murine Mtb infection and that this event enhances bacterial control. As a follow up, we and the TBU treated M. tuberculosis infected rhesus macaques with 5-OP-RU intratracheally but found no clinical or microbiological benefit. MAIT cells did not expand, but rather upregulated PD-1 and lost the ability to produce multiple cytokines, a phenotype resembling T cell exhaustion (PMID: 34158594). Uninfected macaques treated with 5-OP-RU+CpG instillation into the lungs drove MAIT cell dysfunction, and PD-1 blockade during 5-OP-RU treatment partly prevents the loss of MAIT cell function without facilitating their expansion. Apparently, in rhesus macaques, MAIT cells are prone to the loss of effector functions, suggesting therapeutically targeting these cells will be problematic.