Determining Protective Features of Human Memory T-cells to Inform Mycobacterium tuberculosis Vaccine Development

Project Summary / Abstract
Tuberculosis (TB), caused by infection with Mycobacterium tuberculosis (Mtb), is a disease that kills 1.4
million people every year. There is no reliable vaccine to prevent TB, yet many latently-infected individuals are
protected from progressing to active TB despite heavy Mtb exposure living in an endemic setting. CD4+ T cells
are critical for host protection against TB as they interact directly with Mtb-infected cells, secrete cytokines and
cytolytic molecules, and recruit or augment other immune cells. However, the candidate and others find that not
all T cells specific for Mtb antigens are able to recognize Mtb-infected macrophages, the niche cell for Mtb. A
critical unmet need for vaccine development is to define the antigen specificities and functions of T cells that can
recognize infected macrophages and prevent progression to active TB. In Aim 1, the candidate uses autologous
ex vivo co-culture and T cell antigen receptor (TCR) sequencing to determine the proportion, antigen specificities
and functions of memory CD4+ T cells that recognize Mtb-infected macrophages. In Aim 2, the candidate
expands on this system to compare the repertoires of memory CD4 T cells that respond to infected macrophages
among two groups of individuals who live in a setting endemic for TB yet differ in their susceptibility to active
disease. Using single-cell transcriptomics, the candidate compares the functions and TCR repertoires of Mtb-
specific memory CD4+ T cells isolated from exposed individuals who do not develop active TB (“stable” latent
Mtb infection) vs. individuals who will later progress to active TB (“pre-TB” progressors). Results from this project
will define key features of protective memory CD4+ T cells that are linked to the prevention of active TB, providing
benchmarks for vaccine development and improvement of TB risk stratification.
This 5-year K08 program provides mentoring, training in human immunology, translational research and
single-cell transcriptomics for Dr. Stephen Carpenter, a T cell immunologist and infectious disease physician at
Case Western Reserve University (CWRU). The institutional environment at CWRU combines an established
TB research unit, BSL-3 flow cytometry, cell sorting, single-cell RNA sequencing, and expertise in bioinformatics
together with a premier graduate program for scientific interaction and courses. The longstanding Uganda-
CWRU Research Collaboration for TB enables clinical and translational work in a TB endemic setting. The
candidate is establishing a lab with the long-term goals of understanding the defining features of protective
memory T cell responses to Mtb. He has recruited mentors with substantial expertise in translational TB research,
T cell biology and single-cell transcriptomics, including Drs. Henry Boom and Mark Cameron at CWRU, and Dr.
Sam Behar (UMass Medical School). Completion of this K08 project will transition the candidate into an
independent investigator, positioning his research program to use powerful single-cell immune profiling
approaches to track and study antigen-specific human memory T cells.

Grant Number: 5K08AI163407-04
NIH Institute/Center: NIH
Principal Investigator: Stephen Carpenter