Abstract
Gastrointestinal infections by Salmonella enterica serovar Typhi (S. Typhi) are rare in industrialized countries. However, they remain a major public health problem in the developing world with an estimated 26.9 million new cases annually and significant mortality when untreated. Recently, we provided the first direct evidence that CD8+ MAIT cells are activated and have the potential to kill cells exposed to S. Typhi, and that these responses are dependent on bacterial load. However, MAIT cell kinetics and function during bacterial infections in humans remain largely unknown. In this study, we characterize the human CD8+ MAIT cell immune response to S. Typhi infection in subjects participating in a challenge clinical trial who received a low- or high dose of wild-type S. Typhi. We define the kinetics of CD8+ MAIT cells as well as their levels of activation, proliferation, exhaustion/apoptosis, and homing potential. Regardless of the dose, in volunteers resistant to infection (NoTD), the levels of CD8+ MAIT cells after S. Typhi challenge fluctuated around their baseline values (day 0). In contrast, volunteers susceptible to the development of typhoid disease (TD) exhibited a sharp decline in circulating MAIT cells during the development of typhoid fever. Interestingly, MAIT cells from low-dose TD volunteers had higher levels of CD38 coexpressing CCR9, CCR6, and Ki67 during the development of typhoid fever than high-dose TD volunteers. No substantial perturbations on the levels of these markers were observed in NoTD volunteers irrespective of the dose. In sum, we describe, for the first time, that exposure to an enteric bacterium, in this case S. Typhi, results in changes in MAIT cell activation, proliferation, and homing characteristics, suggesting that MAIT cells are an important component of the human host response to bacterial infection.
Highlights
MAIT cells are an “innate” like population of T cells that display a TCR Vα7.2+CD161+ phenotype and are restricted by the nonclassical MHC-related molecule 1 (MR1) [1,2,3]
Results in changes in MAIT cell activation, proliferation, and homing characteristics. These results suggest that MAIT cells are an important component of the human host response to bacterial infection
Because of the potential importance of CD8+ MAIT cells in resistance to bacterial infection, in particular to Salmonella infection [12], we investigated their kinetics in subjects participating in a dose-escalation challenge clinical trial conducted by Dr Pollard’s group (Oxford Vaccine Group) [14]
Summary
MAIT cells are an “innate” like population of T cells that display a TCR Vα7.2+CD161+ phenotype and are restricted by the nonclassical MHC-related molecule 1 (MR1) [1,2,3]. Human MAIT cells express molecules such as CD26, CD45RO, and transcription factors RORγt and ZBTB16, which are involved in their function [7,8,9,10]. They express on their cell surface high levels of cytokine receptors for IL-18, IL-12, and IL-23 [6, 7] and can secrete TNF-α, IFN-γ, IL-17, granzyme a/b, and perforin [3, 7, 11, 12], the latter reinforcing their cytotoxic capability. The evaluation of the influence of the bacterial load in CD8+ MAIT cell kinetics may provide further insight of the CD8+ MAIT cell role during bacterial infection
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
