Over one million people died from tuberculosis (TB) in 2016. Improved understanding of the host factors that influence TB infection and TB disease severity is needed to improve TB treatments and vaccines. Multiple lines of evidence show that excess inflammation worsens outcomes from M. tuberculosis (Mtb) infection. After Mtb infection, macrophages and dendritic cells initiate the immune response, leading to mycobacterial killing, granuloma formation, and T cell activation. The Toll-Interacting Protein (TOLLIP) mediates the immune response to Mtb by dampening several innate immune pathways, including TLR and IL-1 signaling pathways. Our long-term goal is to determine the molecular and cellular mechanisms that influence vaccine immunity and susceptibility to TB. Discovery of innate immune factors, including TOLLIP, that influence vaccine development may influence vaccine design. The objective of this grant is to characterize the role of TOLLIP in influencing T memory differentiation and persistence in the context of chronic TB or BCG exposure. The central hypothesis is that TOLLIP deficiency ? a phenotype we have discovered exists in multiple population -- amplifies the innate immune response to Mtb in a deleterious fashion, weakening Mtb- specific T cell responses and increasing TB susceptibility. The rationale is that identification of innate immune factors that influence T cell immunity in a nuanced fashion provides a novel path toward rational vaccine design.
Our specific aims will test the following hypotheses: 1) TOLLIP deficiency in macrophages is caused by alterations in the TOLLIP transcriptional complex and influences multiple signaling pathways within the macrophage; 2) TOLLIP deficiency increases DC activation, which leads to increased T cell differentiation but reduced vaccine effectiveness in humans, and 3) TOLLIP deficiency impairs lung-specific immunity, particularly in the formation and persistence of resident memory T cells and exhausted T cells in knockout mice. This contribution is significant because it will establish that TOLLIP regulates the innate immune response and improves host defense against M. tuberculosis; this proposal may lead to improved vaccine adjuvants and host-directed therapeutics to Mtb. The proposed work is innovative because we investigate the mechanisms and effects of a functionally active variant of TOLLIP in humans and combine with a knockout mouse model of infection, using novel tools to investigate an understudied, critical immune regulator. Insight into immunoregulatory genes like TOLLIP is impactful because they may offer new targets for modifying the immune response.
The proposed research is relevant to public health because tuberculosis is the commonest cause of death from infections worldwide; despite this, no new vaccines for TB have been introduced in nearly 100 years. By the end of this proposal, we will the role of TOLLIP in altering innate and T cell immunity to M. tuberculosis. In so doing, we hope to understand the ways that TOLLIP regulates immunity and inflammation and identify novel targets for vaccine adjuvants and host-directed therapeutics for TB.