Listeria Monocytogenes: A Model Pathogen Continues to Refine Our Knowledge of the CD8 T Cell Response

Abstract

Listeria monocytogenes (Lm) infection induces robust CD8 T cell responses, which play a critical role in resolving Lm during primary infection and provide protective immunity to re-infections. Comprehensive studies have been conducted to delineate the CD8 T cell response after Lm infection. In this review, the generation of the CD8 T cell response to Lm infection will be discussed. The role of dendritic cell subsets in acquiring and presenting Lm antigens to CD8 T cells and the events that occur during T cell priming and activation will be addressed. CD8 T cell expansion, differentiation and contraction as well as the signals that regulate these processes during Lm infection will be explored. Finally, the formation of memory CD8 T cell subsets in the circulation and in the intestine will be analyzed. Recently, the study of CD8 T cell responses to Lm infection has begun to shift focus from the intravenous infection model to a natural oral infection model as the humanized mouse and murinized Lm have become readily available. Recent findings in the generation of CD8 T cell responses to oral infection using murinized Lm will be explored throughout the review. Finally, CD8 T cell-mediated protective immunity against Lm infection and the use of Lm as a vaccine vector for cancer immunotherapy will be highlighted. Overall, this review will provide detailed knowledge on the biology of CD8 T cell responses after Lm infection that may shed light on improving rational vaccine design.

Structure and function of the immune system in the spleen

“…At later stages of infection, primed CD8+ cytotoxic T cells promote phagocyte clearance of bacteria, directly lyse infected cells, and prevent re-infection (80). These cytotoxic T cells are primed by cDC1s; however, cDC1s also act as a “Trojan Horse” to propagate Listeria infection in the spleen (80, 81) (Fig. 2).…”

T Cell Immunity to Bacterial Pathogens: Mechanisms of Immune Control and Bacterial Evasion

“…However, such cellular sub-localization exposes these intracellular pathogens to enzymatic degradation and, consequently, to MHC class I and II antigen processing machinery, which elicit the presentation of bacterial fragments as antigens to αβ CD4 + and CD8 + T cells. MHC class I-restricted CD8 + T cells are critical for clearing bacterial infections and are known to provide protective immunity against a range of bacterial species, including L. monocytogenes [ 43 ], M. tuberculosis [ 44 ], Salmonella enterica serovar typhimurium (S. typhimurium) [ 45 ], and S. aureu s [ 46 ]. Furthermore, HLA-E restricted CD8 + T cells can also engage antigens from M. tuberculosis and S. typhimurium [ 21 ].…”

Mucosal CD8 T Cell Responses Are Shaped by Batf3-DC After Foodborne Listeria monocytogenes Infection

“…Despite these findings, cDC2 appear to play minimal roles in the generation of protective immunity to Lm, as mice lacking cDC2 do not exhibit defective CD8 T cell responses (16). Although the roles of resident cDC1 and cDC2 after i.v Lm infection have been assessed, the functions of migratory cDC in the early establishment of Lm infection and the induction of T cell responses after foodborne infection have not been extensively studied (20). Some evidence has emerged from foodborne infection of a susceptible Balb/cBy model that suggests that most Lm replicates extracellularly (21).…”