Going beyond gamma for TB protection

A virtual host model of Mycobacterium tuberculosis infection identifies early immune events as predictive of infection outcomes

Tuberculosis (TB), caused by infection with Mycobacterium tuberculosis (Mtb), is one of the world's deadliest infectious diseases and remains a significant global health burden. TB disease and pathology can present clinically across a spectrum of outcomes, ranging from total sterilization of infection to active disease. Much remains unknown about the biology that drives an individual towards various clinical outcomes as it is challenging to experimentally address specific mechanisms driving clinical outcomes. Furthermore, it is unknown whether numbers of immune cells in the blood accurately reflect ongoing events during infection within human lungs. Herein, we utilize a systems biology approach by developing a whole-host model of the immune response to Mtb across multiple physiologic and time scales. This model, called HostSim, tracks events at the cellular, granuloma, organ, and host scale and represents the first whole-host, multi-scale model of the immune response following Mtb infection. We show that this model can capture various aspects of human and non-human primate TB disease and predict that biomarkers in the blood may only faithfully represent events in the lung at early time points after infection. We posit that HostSim, as a first step toward personalized digital twins in TB research, offers a powerful computational tool that can be used in concert with experimental approaches to understand and predict events about various aspects of TB disease and therapeutics.

Tuberculosis-Cancer Parallels in Immune Response Regulation

Mycobacterium tuberculosis and cancer are two diseases with proclivity for the development of resistance to the host immune system. Mechanisms behind resistance can be host derived or disease mediated, but they usually depend on the balance of pro-inflammatory to anti-inflammatory immune signals. Immunotherapies have been the focus of efforts to shift that balance and drive the response required for diseases eradication. The immune response to tuberculosis has widely been thought to be T cell dependent, with the majority of research focused on T cell responses. However, the past decade has seen greater recognition of the importance of the innate immune response, highlighting factors such as trained innate immunity and macrophage polarization to mycobacterial clearance. At the same time, there has been a renaissance of immunotherapy treatments for cancer since the first checkpoint inhibitor passed clinical trials, in addition to work highlighting the importance of innate immune responses to cancer. However, there is still much to learn about host-derived responses and the development of resistance to new cancer therapies. This review examines the similarities between the immune responses to cancer and tuberculosis with the hope that their commonalities will facilitate research collaboration and discovery.