Tissue-resident memory T cells (TRM) are newly defined memory T cells (TM) distinct from circulating TM subsets which have the potential to mount rapid protective immune responses at the site of infection. However, very limited information is available regarding the role and contribution of TRM in vaccine-mediated immune responses in humans at the site of infection. Here, we studied the role and contribution of tissue resident memory T cells (TRM) located in the terminal ileum (TI) (favored site of infection for S. Typhi) following oral Ty21a immunization in humans. We examined TI-lamina propria mononuclear cells (LPMC) and intra-epithelial lymphocytes (IEL) CD8+ TRM subsets obtained from healthy volunteers undergoing medically-indicated colonoscopies who were either immunized with Ty21a or unvaccinated. No significant differences in the frequencies of LPMC CD8+ TRM and CD8+CD69+CD103- T cells subsets were observed following Ty21a-immunization. However, LPMC CD8+ TRM exhibited significantly higher levels of cytokines (IFN-γ, IL-17A, and TNF-α) ex-vivo in Ty21a-vaccinated than in unvaccinated volunteers. LPMC CD8+ TRMS. Typhi-specific responses were evaluated using S. Typhi-infected targets and found to produce significantly higher levels of S. Typhi-specific IL-17A. In contrast, LPMC CD8+CD69+CD103- T cells produced significantly increased S. Typhi-specific levels of IFN-γ, IL-2, and IL-17A. Finally, we assessed CD8+ TRM in IEL and observed that the frequency of IEL CD8+ TRM is significantly lower following Ty21a immunization. However, ex-vivo IEL CD8+ TRM elicited by Ty21a immunization spontaneously produced significantly higher levels of cytokines (IFN-γ, IL-17A, IL-2, and TNF-α). This study provides the first demonstration of the effect of oral Ty21a vaccination on CD8+ TRM subsets (spontaneous and S. Typhi-specific) responses in the LPMC and IEL compartment of the human terminal ileum mucosa, contributing novel information to our understanding of the generation of mucosal immune responses following oral Ty21a-immunization.

Lifelong maintenance of the blood system requires equilibrium between clearance of damaged hematopoietic stem cells (HSCs) and long-term survival of the HSC pool. Severe perturbations of cellular homeostasis result in rapid HSC loss to maintain clonal purity. However, normal homeostatic processes can also generate lower-level stress; how HSCs survive these conditions remains unknown. Here we show that the integrated stress response (ISR) is uniquely active in HSCs and facilitates their persistence. Activating transcription factor 4 (ATF4) mediates the ISR and is highly expressed in HSCs due to scarcity of the eIF2 translation initiation complex. Amino acid deprivation results in eIF2α phosphorylation-dependent upregulation of ATF4, promoting HSC survival. Primitive acute myeloid leukemia (AML) cells also display eIF2 scarcity and ISR activity marks leukemia stem cells (LSCs) in primary AML samples. These findings identify a link between the ISR and stem cell survival in the normal and leukemic contexts.
Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Polyparasitism is common in the developing world. We have previously demonstrated that schistosomiasis-positive (SP) Malian children, aged 4-8 years, are protected from malaria compared to matched schistosomiasis-negative (SN) children. The effect of concomitant schistosomiasis upon acquisition of T cell memory is unknown. We examined antigen-specific T cell frequencies in 48 Malian children aged 4-14 to a pool of malaria blood stage antigens, and a pool of schistosomal antigens, at a time point during a malaria episode and at a convalescent time point ~6 months later, following cessation of malaria transmission. CD4+ T cell-derived memory responses, defined as one or more significant cytokine (IFN-γ, TNF-α, IL-2, and/or IL-17A) responses, was measured to schistoma antigens in 18/23 SP children at one or both time points, compared to 4/23 SN children (P < 0.0001). At the time of malaria infection, 12/24 SN children and 15/23 SP children (P = 0.29) stimulated with malaria antigens demonstrated memory recall as defined by CD4-derived cytokine production. This compares to 7/23 SN children and 16/23 SP children (P = 0.009) at the convalescent timepoint. 46.2% of cytokine-producing CD4+ T cells expressed a single cytokine after stimulation with malaria antigen during the malaria episode. This fell to 40.9% at follow-up with a compensatory rise of multifunctional cytokine secretion over time, a phenomenon consistent with memory maturation. The majority (53.2-59.5%) of responses derived from CD45RA-CD62L- effector memory T cells with little variation in the phenotype depending upon the time point or the study cohort. We conclude that detectable T cell memory responses can be measured against both malaria and schistosoma antigens and that the presence of Schistosoma haematobium may be associated with long-term maintenance of T memory to malaria.

Systemic cellular immunity elicited by the Ty21a oral typhoid vaccine has been extensively characterized. However, very limited data are available in humans regarding mucosal immunity at the site of infection (terminal ileum [TI]). Here we investigated the host immunity elicited by Ty21a immunization on terminal ileum-lamina propria mononuclear cells (LPMC) and peripheral blood in volunteers undergoing routine colonoscopy.
We characterized LPMC-T memory (TM) subsets and assessed Salmonella enterica serovar Typhi (S Typhi)-specific responses by multichromatic flow cytometry.
No differences were observed in cell yields and phenotypes in LPMC CD8+-TM subsets following Ty21a immunization. However, Ty21a immunization elicited LPMC CD8+ T cells exhibiting significant S Typhi-specific responses (interferon-γ, tumor necrosis factor-α, interleukin-17A, and/or CD107a) in all major TM subsets (T-effector/memory [TEM], T-central/memory, and TEM-CD45RA+), although each TM subset exhibited unique characteristics. We also investigated whether Ty21a immunization elicited S Typhi-specific multifunctional effectors in LPMC CD8+ TEM. We observed that LPMC CD8+ TEM responses were mostly multifunctional, except for those cells exhibiting the characteristics associated with cytotoxic responses. Finally, we compared mucosal with systemic responses and made the important observation that LPMC CD8+S Typhi-specific responses were unique and distinct from their systemic counterparts.
This study provides the first demonstration of S Typhi-specific responses in the human terminal ileum mucosa and provides novel insights into the generation of mucosal immune responses following oral Ty21a immunization.

CD8+ cytotoxic T lymphocyte (CTL) exhaustion is a chief issue for ineffective virus elimination in chronic infectious diseases. We generated novel ovalbumin (OVA)-specific OVA-Texo and HIV-specific Gag-Texo vaccines inducing therapeutic immunity. To assess their therapeutic effect in chronic infection, we developed a new chronic infection model by i.v. infecting C57BL/6 mice with the OVA-expressing adenovirus AdVova. During chronic AdVova infection, mouse CTLs were found to express the inhibitory molecules programmed cell-death protein-1 (PD-1) and lymphocyte-activation gene-3 (LAG-3) and to be functionally exhausted, showing a significant deficiency in T-cell proliferation, IFN-γ production and cytolytic effects. Naive CD8+ T cells upregulated inhibitory PD-ligand 1 (PD-L1), B- and T-lymphocyte attenuator and T-cell anergy-associated molecules (Grail and Itch) while down-regulating the proliferative response upon stimulation in mice with chronic infection. Remarkably, the OVA-Texo vaccine counteracted T-cell anergy and converted CTL exhaustion. The latter was associated with (i) the upregulation of a marker for CTL functionality, diacetylated histone-H3 (diAcH3), (ii) a fourfold increase in CTLs, occurring independent of host DCs or CD4+ T cells, and (iii) the restoration of CTL IFN-γ production and cytotoxicity. In vivo OVA-Texo-stimulated CTLs upregulated the activities of the mTORC1 pathway-related molecules Akt, S6, eIF4E and T-bet, and treatment of the CTLs with an mTORC1 inhibitor, rapamycin, significantly reduced the OVA-Texo-induced increase in CTLs. Interestingly, OVA-Texo-mediated CD40L signaling played a critical role in the observed immunological effects. Importantly, the Gag-Texo vaccine induced Gag-specific therapeutic immunity in chronic infection. Therefore, this study should have a serious impact on the development of new therapeutic vaccines for human immunodeficiency virus (HIV-1) infection.