CD8+ T cells activated during viral infection migrate to infected skin in an antigen-independent manner. Local recognition of antigens drives the differentiation into Trm CD8+ T cells.

Trafficking of memory CD8+ T cells out of the circulation is essential to provide protective immunity against intracellular pathogens in non-lymphoid tissues. However, the molecular mechanisms that dictate the trafficking potential of diverse memory CD8+ T cell populations are not completely defined. Here, we show that following infection or inflammatory challenge, central memory (TCM) CD8+ T cells rapidly traffic into non-lymphoid tissues, whereas most effector memory (TEM) cells remain in the circulation. Furthermore, we demonstrate that cellular migration of memory CD8+ T cells into non-lymphoid tissues is driven by IL-15-stimulated enzymatic synthesis of core 2 O-glycans, which generates functional ligands for E- and P-selectin. Given that IL-15 stimulated expression of glycosyltransferase enzymes is largely a feature of TCM CD8+ T cells, this allows TCM to selectively migrate out of the circulation and into non-lymphoid tissues. Thus, these data show that the capacity to synthesize core 2 O-glycans identifies the memory CD8+ T cells with tissue-trafficking potential and that TCM, and not TEM, is the major subset that enters non-lymphoid tissues following infection or tissue injury.

Memory CD8+ T cells in the circulation rapidly infiltrate non-lymphoid tissues following infection and provide protective immunity in an antigen-specific manner. However, the subsequent fate of memory CD8+ T cells after entering non-lymphoid tissues such as the skin during a secondary infection is largely unknown. Furthermore, because expression of CD62L is often used to identify the central memory (TCM) CD8+ T cell subset, uncoupling the physical requirement for CD62L-mediated lymph node homing versus other functional attributes of TCM CD8+ T cells remains unresolved. Here, we show that in contrast to naïve CD8+ T cells, memory CD8+ T cells traffic into the skin independent of CD62L-mediated lymph node re-activation and provide robust protective immunity against Vaccinia virus (VacV) infection. TCM, but not effector memory (TEM), CD8+ T cells differentiated into functional CD69+/CD103- tissue residents following viral clearance, which was also dependent on local recognition of antigen in the skin microenvironment. Finally, we found that memory CD8+ T cells expressed granzyme B after trafficking into the skin and utilized cytolysis to provide protective immunity against VacV infection. Collectively, these findings demonstrate that TCM CD8+ T cells become cytolytic following rapid infiltration of the skin to protect against viral infection and subsequently differentiate into functional CD69+ tissue-residents.

Enteropathogenic Escherichia coli is an important cause of profuse, watery diarrhea in infants living in developing regions of the world. Typical strains of EPEC (tEPEC) possess a virulence plasmid, while related clinical isolates that lack the pEAF plasmid are termed atypical EPEC (aEPEC). tEPEC and aEPEC tend to cause acute vs. more chronic type infections, respectively. The pEAF plasmid encodes an attachment factor as well as a regulatory operon, perABC. PerC, a poorly understood regulator, was previously shown to regulate expression of the type III secretion system through Ler. Here we elucidate the regulon of PerC using RNA sequencing analysis to better our understanding of the role of the pEAF in tEPEC infection. We demonstrate that PerC controls anaerobic metabolism by increasing expression of genes necessary for nitrate reduction. A tEPEC strain overexpressing PerC exhibited a growth advantage compared to a strain lacking this regulator, when grown anaerobically in the presence of nitrate, conditions mimicking the human intestine. We show that PerC strongly down-regulates type I fimbriae expression by manipulating fim phase variation. The quantities of a number of non-coding RNA molecules were altered by PerC. In sum, this protein controls niche adaptation, and could help to explain the function of the PerC homologs (Pch), many of which are encoded within prophages in related, Gram-negative pathogens.

dZinc supplements are an effective clinical treatment for infantile diarrheal disease caused by enteric pathogens. Previous studies demonstrated that zinc acts on enteropathogenic Escherichia coli (EPEC) bacteria directly to suppress several virulence-related genes at a concentration that can be achieved by oral delivery of dietary zinc supplements. Our in vitro studies showed that a micromolar concentration of zinc induced the envelope stress response and suppressed virulence in EPEC, providing a possible mechanistic explanation for zinc's therapeutic action. In this report, we investigated the molecular and physiological changes in EPEC induced by zinc. We found that micromolar concentrations of zinc reduced the bacterial growth rate without affecting viability. We observed increased membrane permeability caused by zinc. Zinc upregulated the RpoE-dependent envelope stress response pathway and suppressed EPEC virulence gene expression. RpoE alone was sufficient to inhibit virulence factor expression and to attenuate attaching and effacing lesion formation on human host cells. By mutational analysis we demonstrate that the DNA-binding motif of RpoE is necessary for suppression of the LEE1, but not the LEE4, operon. Predictably, inhibition of the RpoE-mediated envelope stress response in combination with micromolar concentrations of zinc reduced EPEC viability. In conclusion, zinc induces the RpoE and stress response pathways in EPEC, and the alternate sigma factor RpoE downregulates EPEC LEE and non-LEE virulence genes by multiple mechanisms.A cute diarrheal infections (ADI) are a major cause of morbidity and mortality in children, particularly those living in developing countries. Worldwide, children suffer from ϳ2 billion bouts of diarrhea annually, with approximately 1 million children under the age of 5 years dying of ADI every year. Even nonlethal infections can lead to malnutrition, cognitive impairment, and permanent gastrointestinal damage.In 2008, the World Health Organization began administering dietary zinc supplements with oral rehydration therapy to those suffering from ADI. Along with restoring normal zinc levels, which are essential for proper immune function (1, 2), this metal ion affects the virulence of gastrointestinal, bacterial pathogens even in children with normal plasma zinc concentrations. In 1995, a double-blind, randomized control trial involving 937 children with acute diarrhea in New Delhi, India, demonstrated that dietary zinc supplements of 20 mg per day given to children under the age of 3 years significantly reduced the severity and duration of disease (3). The children were 23% less likely to have continued diarrhea, with a 39% reduction in the frequency of episodes. There was a 21% reduction in the mean number of days with watery stools and a 39% drop in the number of watery stools per day. Thus, by a yet unknown mechanism, zinc dietary supplements benefited children with ADI, even those with normal plasma zinc levels.To understand the mechanism by which zinc affected bacterium...