Tuberculosis has caused disease in humans for thousands of years and is still a significant global health threat. However, the immune response to Mycobacterium tuberculosis infection is still not completely understood. Research into new vaccines and therapeutics use animal models before potential candidates go forward to human trials. One of the main species used is the non-human primate model. Although a great deal of research has been undertaken in this model, the early immune responses within the granuloma are still not fully understood.

The aim of this thesis was to characterise the cellular composition of granulomas at early- and late-phases of disease in both rhesus and cynomolgus macaques using histological, immunohistochemical, and in-situ hybridisation techniques to visualise and count the number of positively stained cells and describe the spatial distribution of cells within the granuloma. Furthermore, NanoString nCounter gene expression analysis was tested to assess the suitability of the technique for use on formalin-fixed paraffin embedded tissues that had been archived and stored for approximately ten years.

This project highlights that there are differences in the cellular composition of granulomas between rhesus and cynomolgus macaques, with cynomolgus macaques showing that they are better able to control TB disease compared to rhesus. The gene expression profiles were able to identify a difference between early-stage and late-stage granulomas, however when comparing species regardless of granuloma type the findings support the data that each animal is heterogenous in their immune response to Mtb infection. The success of this technology opens up a wealth of underutilised archived samples that can now be used to interrogate new hypotheses to further our understanding of cellular interactions within granulomas avoiding the need to use more animals. Data collected from these samples could be used to develop novel immunotherapeutic approaches with which to combat human tuberculosis.