Distinct time-dependent S. Typhi-specific CD8+ T cell programs are associated with clinical outcome following Ty21a immunization and wild-type S. Typhi challenge in humans

Introduction

CD8+ T cells are essential components of the adaptive immune system that play a critical role in determining the clinical severity of typhoid disease by directly killing Salmonella enterica serovar Typhi (S. Typhi)-infected cells, producing cytokines, chemokines, and establishing memory responses that have been linked to clinical outcome in a controlled human infection model (CHIM) of typhoid. Despite decades of extensive research, the role of memory CD8+ T (TM) cells and its subsets as correlates of protection against S. Typhi infection and typhoid disease remains incompletely understood.