Effective vaccines remain elusive for many deadly diseases; therefore, it is critical that we better understand how the immune system generates a robust, neutralizing antibody response to vaccination so that we may enhance this type of response in future vaccine design. B cells are the producers of high-affinity antibodies, however, it is the CD4+ T cells that provide the cytokines and co-stimulatory molecules necessary to drive this B cell fate and establish long-term humoral immunity. This is why it is critical that we better understand the development and function of specific CD4+ T cell subsets involved in generating this type of response. After a primary infection or vaccination, some activated CD4+ T cells become a specialized subset specifically known to provide direct B cell help: T follicular helper (Tfh) cells. What commits T cells to the Tfh cell fate is still unknown. Our novel approach leverages the CD4+ T cell response against the immunodominant LLO epitope from Listeria in B6 mice, using two defined CD4+ TCR transgenic lines and polyclonal T cells. The two naive T cells differ in their tonic signaling mediated through the TCR recognition of self-pMHC. Naive CD4+ T cells with low tonic signaling have a high basal metabolism, respond robustly in a primary in vivo response, and develop into Tfh and TEM cells. Conversely, naive CD4+ T cells with high tonic signaling have a low basal metabolism, and poorly form Tfh cells. The premise of this proposal is that the strength of TCR:self-pMHC reactivity (tonic signaling) is deterministic for establishing the basal metabolism and the subsequent Tfh response.
In Aim 1, we will establish whether a direct relationship exists between tonic signaling and the development of Tfh following antigen exposure. To this end, we will use our novel knock-in mouse line, Scn5a+. Expression of th Scn5a voltage gated sodium channel allows us to increase tonic signaling in CD4+ T cells independent of TCR signaling. We will decrease tonic signaling using a newly developed conditional knockout allele of H-2DM. Tfh helper function will be tested using an NP-LLO model.
In Aim 2 we will examine how T cell metabolism influences Tfh cell responses. We have identified the glycerol phosphate shuttle as a key player in the increased metabolism of the LLO-118 T cells. We have now generated a mouse with a conditional knockout allele of mGPD2 which will be a powerful reagent to explore the role of this metabolic pathway in LLO-118 and polyclonal CD4+ T cell responses. These findings will deepen our understanding of Tfh development and may reveal therapeutic targets for vaccine design and autoimmunity.

Public Health Relevance

Understanding how helper T cells develop and function in an immune response is important in understanding how to combat infectious organisms. This project will explore how tonic signaling in T cells influences the cellular metabolism and type of immune response in live animals.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI139540-03
Application #
10075219
Study Section
Cellular and Molecular Immunology - B Study Section (CMIB)
Program Officer
Ferguson, Stacy E
Project Start
2019-01-15
Project End
2023-12-31
Budget Start
2021-01-01
Budget End
2021-12-31
Support Year
3
Fiscal Year
2021
Total Cost
Indirect Cost
Name
Washington University
Department
Pathology
Type
Schools of Medicine
DUNS #
068552207
City
Saint Louis
State
MO
Country
United States
Zip Code
63130