Vaccination or Treatment Against TB Modify the Phenotype and Transcriptome of Pulmonary Granulomas in NHPs

Vaccination or Treatment Against TB Modify the Phenotype and Transcriptome of Pulmonary Granulomas in NHPs

Dr F Javier Salguero Bodes, UK Health Security Agency (UKHSA), UK

Non-human primate (NHP) animal models of pulmonary TB, using either rhesus or cynomolgus macaques, have been widely used to test vaccines and therapeutics against TB. BCG (Bacillus Calmette-Guérin) is the only currently available vaccine against TB, but at least 15 vaccine candidates are in clinical phases for the control of TB, including MTBVAC, a live-attenuated strain of Mycobacterium tuberculosis (Mtb), designed to stimulate specific host immune responses mimicking natural TB infection without causing disease, through the stable deletions of the major virulence genes phoP and fadD26. Standard treatment with a combination of drugs (HRZE) is also used in human patients and as a model in NHPs to explore new therapies.

In this study, we have used samples from rhesus macaques vaccinated with MTBVAC or BCG, or treated, to study the phenotype of the pulmonary lesions induced by Mtb. We used histopathology, immunohistochemistry (IHC), multiplex immunofluorescence (IF), and tissue transcript analysis (including spatial transcriptomics in FFPE tissues). Histopathological analyses, IHC, and IF were used to describe the distribution and severity of granulomas and the cell populations within the lesions (CD68+ macrophages, CD3+ T cells, CD20+ B cells, MPO+ neutrophils, and Mtb antigens). Digital image analysis was used to quantify the presence of these cell markers and their interactions. Nanostring (nCounter and GeoMx) was used with FFPE sections to map host immune transcript abundance within the tissue and specific regions of interest (lesions).

Vaccination and treatment revealed a reduction in the frequency and severity of lesions, accompanied by a change in immune cell distribution within granulomas. Transcript analysis revealed an upregulation of pathology pathways, including proinflammatory cytokines or chemokines in unvaccinated/untreated animals, together with innate and adaptive immune activation in treated/vaccinated animals, among multiple genes and parameters analysed.