Memory CD8 T-cell Research Articles

Innate T-\u03b1\u03b2 lymphocytes as new immunological components of anti-tumoral \u201coff-target\u201d effects of the tyrosine kinase inhibitor dasatinib

Kinase inhibitors hold great potential as targeted therapy against malignant cells. Among them, the tyrosine kinase inhibitor dasatinib is known for a number of clinically relevant off-target actions, attributed in part to effects on components of the immune system, especially conventional T-cells and natural killer (NK)-cells. Here, we have hypothesized that dasatinib also influences non-conventional T-αβ cell subsets known for their potential anti-tumoral properties, namely iNKT cells and the distinct new innate CD8 T-cell subset. In mice, where the two subsets were originally characterized, an activated state of iNKT cells associated with a shift toward an iNKT cell Th1-phenotype was observed after dasatinib treatment in vivo. Despite decreased frequency of the total memory CD8 T-cell compartment, the proportion of innate-memory CD8 T-cells and their IFNγ expression in response to an innate-like stimulation increased in response to dasatinib. Lastly, in patients administered with dasatinib for the treatment of BCR-ABL-positive leukemias, we provided the proof of concept that the kinase inhibitor also influences the two innate T-cell subsets in humans, as attested by their increased frequency in the peripheral blood. These data highlight the potential immunostimulatory capacity of dasatinib on innate T-αβ cells, thereby opening new opportunities for chemoimmunotherapy.

Pregnancy Gestation Impacts on HIV-1-Specific Granzyme B Response and Central Memory CD4 T Cells.

Pregnancy induces alterations in peripheral T-cell populations with both changes in subset frequencies and anti-viral responses found to alter with gestation. In HIV-1 positive women anti-HIV-1 responses are associated with transmission risk, however detailed investigation into both HIV-1-specific memory responses associated with HIV-1 control and T-cell subset changes during pregnancy have not been undertaken. In this study we aimed to define pregnancy and gestation related changes to HIV-1-specific responses and T-cell phenotype in ART treated HIV-1 positive pregnant women. Eleven non-pregnant and 24 pregnant HIV-1 positive women were recruited, peripheral blood samples taken, fresh cells isolated, and compared using ELISpot assays and flow cytometry analysis. Clinical data were collected as part of standard care, and non-parametric statistics used. Alterations in induced IFNγ, IL-2, IL-10, and granzyme B secretion by peripheral blood mononuclear cells in response to HIV-1 Gag and Nef peptide pools and changes in T-cell subsets between pregnant and non-pregnant women were assessed, with data correlated with participant clinical parameters and longitudinal analysis performed. Cross-sectional comparison identified decreased IL-10 Nef response in HIV-1 positive pregnant women compared to non-pregnant, while correlations exhibited reversed Gag and Nef cytokine and protease response associations between groups. Longitudinal analysis of pregnant participants demonstrated transient increases in Gag granzyme B response and in the central memory CD4 T-cell subset frequency during their second trimester, with a decrease in CD4 effector memory T cells from their second to third trimester. Gag and Nef HIV-1-specific responses diverge with pregnancy time-point, coinciding with relevant T-cell phenotype, and gestation associated immunological adaptations. Decreased IL-10 Nef and both increased granzyme B Gag response and central memory CD4 T cells implies that amplified antigen production is occurring, which suggests a period of compromised HIV-1 control in pregnancy.

Levels of Human Immunodeficiency Virus DNA Are Determined Before ART Initiation and Linked to CD8 T-Cell Activation and Memory Expansion.

Initiation of antiretroviral therapy (ART) in early compared with chronic human immunodeficiency virus (HIV) infection is associated with a smaller HIV reservoir. This longitudinal analysis of 60 individuals who began ART during primary HIV infection (PHI) investigates which pre- and posttherapy factors best predict HIV DNA levels (a correlate of reservoir size) after treatment initiation during PHI. The best predictor of HIV DNA at 1 year was pre-ART HIV DNA, which was in turn significantly associated with CD8 memory T-cell differentiation (effector memory, naive, and T-bet−Eomes− subsets), CD8 T-cell activation (CD38 expression) and T-cell immunoglobulin and mucin-domain containing-3 (Tim-3) expression on memory T cells. No associations were found for any immunological variables after 1 year of ART. Levels of HIV DNA are determined around the time of ART initiation in individuals treated during PHI. CD8 T-cell activation and memory expansion are linked to HIV DNA levels, suggesting the importance of the initial host-viral interplay in eventual reservoir size.

A CD19/CD3 Bispecific Antibody Induces Superior T Cell Responses Against Chronic Lymphocytic Leukemia When Combined with Ibrutinib

Targeting B-cell receptor signaling with ibrutinib, the first-in-class irreversible inhibitor of Bruton tyrosine kinase, has become a highly successful treatment modality for Chronic Lymphocytic Leukemia (CLL) patients. However, there remains a need for adjunct treatments to deepen responses and prevent or treat resistant disease. Ibrutinib also inhibits inducible T-cell kinase (ITK) which is hypothesized to improve antitumor T-cell immunity. We developed a CD19/CD3 bispecific antibody (bsAb) in a 100 kDa single chain-Fv-Fc format (19/3-scFv-Fc). We previously reported increased T-cell activation and cytotoxic activity by the bsAb in blood samples from ibrutinib-treated patients compared to treatment-naïve patients. To better understand how ibrutinib affects T-cell function and increases cytotoxic activity we assessed T-cell responses to the bsAb in samples from ibrutinib-treated patients (12 ± 2 months on ibrutinib) and treatment-naïve (TN) patients. We cultured peripheral blood mononuclear cells (PBMCs) from both patient groups with bsAb and measured CLL cell death, T-cell expansion, activation, and differentiation by flow cytometry. After 5 days of exposure, the CD19/CD3 bsAb induced superior killing of ibrutinib-treated CLL cells, with a median specific-killing of 97% for ibrutinib-treated compared to 77 % for treatment-naïve patient samples (n = 15; p= 0.008). In vitro treatment with CD19/CD3 bsAb induced ≥ 5-fold expansion of autologous CD8 and CD4 T cells and an increase of CD45RO+CCR7- effector memory and CD45RO+CCR7+ central memory CD4 T-cells in response to bsAb (Table 1). We also observed a shift towards Th1 (CCR6-CXCR3+) polarization, and higher T-cell granzyme B expression in response to CD19/CD3 bsAb. While T cells from both patient groups responded to the bsAb, all these effects were more pronounced in ibrutinib-treated samples compared to treatment-naïve samples (Table 1). There was a 13-fold increase of the Th1/Th2 ratio in PBMCs from ibrutinib-treated patients compared to a 7-fold increase in the treatment-naïve group. Moreover, the bsAb induced a significant increase of activation markers HLADR (p=0.0013; p=0.0006) and CD27 (p< 0.001; p=0.0114) on CD4 and CD8 T cells in the ibrutinib-treated patient samples, while there was no significant change in T-cell activation in the treatment-naïve group. Granzyme B expression in CD8 T cells was high even in untreated samples and its upregulation by the bsAb was comparable in both patient groups. However, we observed a 25-fold increase in granzyme B positive CD4 T cells in ibrutinib-treated samples, 5-fold higher than in the treatment-naïve samples. In summary, the enhanced cytotoxic activity of T cells in response to the bsAb in samples from ibrutinib-treated patients correlated with increased memory cell differentiation, higher T-cell activation, and a strong shift towards a Th1 phenotype. As ibrutinib enhances anti-CLL activity of autologous T cells, bsAb immunotherapy may work well with concurrent ibrutinib treatment. These data support the investigation of bsAbs in combination with ibrutinib for immunotherapy of CLL. The mechanisms underlying the enhanced T-cell responses remain to be fully elucidated. In particular, it will be important to define whether inhibition of ITK by ibrutinib plays a role in enhancing T-cell dependent cytotoxicity. Supported by the intramural program of the NHLBI/NIH. Disclosures Rader: NIH: Patents & Royalties: ROR1 mAb 2A2. Wiestner:Acerta: Research Funding; Merck: Research Funding; Nurix: Research Funding; Pharmayclics: Research Funding.

USP18 is a significant driver of memory CD4 T-cell reduced viability caused by type I IFN signaling during primary HIV-1 infection.

The loss of Memory CD4 T-cells (Mem) is a major hallmark of HIV-1 immuno-pathogenesis and occurs early during the first months of primary infection. A lot of effort has been put into understanding the molecular mechanisms behind this loss, yet they still have not been fully identified. In this study, we unveil the unreported role of USP18 in the deleterious effects of sustained type I IFN signaling on Mem, including HIV-1-specific CD4 T-cells. We find that interfering with IFN-I signaling pathway in infected patients, notably by targeting the interferon-stimulated gene USP18, resulted in reduced PTEN expression similar to those observed in uninfected control donors. We show that AKT activation in response to cytokine treatment, T-cell receptor (TcR) triggering, as well as HIV-1 Gag stimulation was significantly improved in infected patients when PTEN or USP18 were inhibited. Finally, our data demonstrate that higher USP18 in Mem from infected patients prevent proper cell survival and long-lasting maintenance in an AKT-dependent manner. Altogether, we establish a direct role for type I IFN/USP18 signaling in the maintenance of total and virus-specific Mem and provide a new mechanism for the reduced survival of these populations during primary HIV-1 infection.

1017P - Immune-related gene expression profiling after neoadjuvant chemotherapy (NACT) of ovarian high-grade serous carcinoma

BackgroundIn patients with stage III or IV HGSOC who are not suitable for primary surgery (PDS), 3 cycles of platinum based NACT followed by interval surgery (IDS) and adjuvant chemotherapy is an accepted treatment approach. NACT enhances host immune response by increasing levels of PD1, CTLA4 and PDL1 (Böhm S et al. Clin Cancer Res 2016). Gene expression profiling of tumors has identified prognostic signatures for patient selection with immunotherapy (Ribas A et al. J Clin Oncol 2015). MethodsThe purpose of this study is to assess the effect of neoadjuvant chemotherapy (NACT) on immune activation in stage IIIC/IV tubo-ovarian high-grade serous carcinoma (HGSOC). We obtained pre- and post-treatment omental biopsies from a total of 45 patients undergoing platinum-based NACT followed by IDS. We measured T-cell density and phenotype, immune activation, and markers of cancer-related inflammation using IHC. Messenger RNA expression was analyzed on the nCounter system using the PanCancer IO360 Panel. ResultsThere was evidence of T-cell activation in omental biopsies after NACT. CD4+ T cells showed enhanced IFNgproduction and antitumor Th1 gene signatures were increased. T-cell activation correlated with therapeutic response to NACT. The CD8 T-cell and CD45RO memory cell density in the tumor microenvironment was unchanged after NACT, but biopsies after a good therapeutic response had significantly fewer FoxP3+(Treg) cells. Biopsies of good therapeutic responders also showed areduction in a Treg gene signature in post versus pre-NACT samples.Preliminary results according to gene expression of the immune compartment reveal that tumor infiltrating lymphocytes were more abundant in samples from patients showing a good response over those with no or incomplete response to NACT, as well as an increase in gene signatures associated with antigen presentation and Cytokine and Chemokine Signaling. When comparing the expression profiles between samples obtained before or after NACT in patients showing incomplete response,we obtained an expected decreased in cellular proliferation signature. ConclusionsNACT may promote an immune modulatory effect that could improve or favour the further use of specific immunotherapy in HGSOC patients. Legal entity responsible for the studyFundación para la Investigación 12 de Octubre. FundingTesaro SL. DisclosureL.M. Manso: Research grant / Funding (self): Tesaro; Advisory / Consultancy: Roche, Novartis, Tesaro, AstraZeneca, Pfizer, Clovis; Speaker Bureau / Expert testimony: Roche, Novartis, Tesaro, AstraZeneca, Pfizer, Clovis; Travel / Accommodation / Expenses: Roche, Novartis, Tesaro, Pfizer. S. Wang: Full / Part-time employment: Tesaro. All other authors have declared no conflicts of interest.

Pathogenic CD8+ Epidermis-Resident Memory T Cells Displace Dendritic Epidermal T Cells in Allergic Dermatitis

The skin is our interface with the outside world, and consequently it is exposed to a wide range of microbes and allergens. Recent studies have indicated that allergen-specific skin-resident memory T (TRM) cells play a role in allergic contact dermatitis (ACD). However, the composition and dynamics of the epidermal T-cell subsets during ACD are not known. Here we show that exposure of the skin to the experimental contact allergen DNFB results in a displacement of the normally occurring dendritic epidermal T cells (DETC) concomitant with an accumulation of epidermal CD8+CD69+CD103+ TRM cells in mice. By studying knockout mice, we provide evidence that CD8+ T cells are required for the displacement of the DETC and that DETC are not required for recruitment of CD8+ TRM cells to the epidermis following allergen exposure. We demonstrate that the magnitude of the allergic reaction correlates with the number of CD8+ epidermal TRM cells, which again correlates with allergen dose and number of allergen exposures. Finally, in an attempt to elucidate why CD8+ epidermal TRM cells persist in the epidermis, we show that CD8+ epidermal TRM cells have a higher proliferative capability and are bioenergetically more stable, displaying a higher spare respiratory capacity than DETC.

Bystander responses impact accurate detection of murine and human antigen-specific CD8+ T cells

Induction of memory CD8 T cells is important for controlling infections such as malaria HIV/AIDS, and for cancer immunotherapy. Accurate assessment of antigen (Ag)-specific CD8 T-cells is critical for vaccine optimization and defining correlates of protection. However, conditions for determining Ag-specific CD8 T-cell responses ex-vivo using ICS may be variable, especially in humans with complex antigens. Here, we used an attenuated whole parasite malaria vaccine model in humans and various experimental infections in mice to show that the duration of antigenic stimulation and timing of brefeldin A (BFA) addition influences the magnitude of Ag-specific and bystander T cell responses. Indeed, following immunization with an attenuated whole sporozoite malaria vaccine in humans, significantly higher numbers of IFN-γ producing memory CD8 T-cells comprised of antigen specific and bystander responses were detected by increasing the duration of Ag-stimulation prior to addition of BFA. Mechanistic analyses of virus-specific CD8 T-cells in mice revealed that the increase in IFNg producing CD8 T-cells was due to bystander activation of Ag-experienced memory CD8 T-cells, and correlated with the proportion of Ag-experienced CD8 T-cells in the stimulated populations. Incubation with anti-cytokine antibodies (ex. IL-12) improved accuracy in detecting bona-fide memory CD8 T-cell responses suggesting this as the mechanism for the bystander activation. These data have important implications for accurate assessment of immune responses generated by vaccines intended to elicit protective memory CD8 T-cells.

Stability and flexibility in chromatin structure and transcription underlies memory CD8 T-cell differentiation.

The process by which naïve CD8 T cells become activated, accumulate, and terminally differentiate as well as develop into memory cytotoxic T lymphocytes (CTLs) is central to the development of potent and durable immunity to intracellular infections and tumors. In this review, we discuss recent studies that have elucidated ancestries of short-lived and memory CTLs during infection, others that have shed light on gene expression programs manifest in individual responding cells and chromatin remodeling events, remodeling factors, and conventional DNA-binding transcription factors that stabilize the differentiated states after activation of naïve CD8 T cells. Several models have been proposed to conceptualize how naïve cells become memory CD8 T cells. A parsimonious solution is that initial naïve cell activation induces metastable gene expression in nascent CTLs, which act as progenitor cells that stochastically diverge along pathways that are self-reinforcing and result in shorter- versus longer-lived CTL progeny. Deciphering how regulatory factors establish and reinforce these pathways in CD8 T cells could potentially guide their use in immunotherapeutic contexts.

The Role of Pre-existing Cross-Reactive Central Memory CD4 T-Cells in Vaccination With Previously Unseen Influenza Strains.

Influenza vaccination is a common approach to prevent seasonal and pandemic influenza. Pre-existing antibodies against close viral strains might impair antibody formation against previously unseen strains–a process called original antigenic sin. The role of this pre-existing cellular immunity in this process is, despite some hints from animal models, not clear. Here, we analyzed cellular and humoral immunity in healthy individuals before and after vaccination with seasonal influenza vaccine. Based on influenza-specific hemagglutination inhibiting (HI) titers, vaccinees were grouped into HI-negative and -positive cohorts followed by in-depth cytometric and TCR repertoire analysis. Both serological groups revealed cross-reactive T-cell memory to the vaccine strains at baseline that gave rise to the majority of vaccine-specific T-cells post vaccination. On the contrary, very limited number of vaccine-specific T-cell clones was recruited from the naive pool. Furthermore, baseline quantity of vaccine-specific central memory helper T-cells and clonotype richness of this population directly correlated with the vaccination efficacy. Our findings suggest that the deliberate recruitment of pre-existing cross-reactive cellular memory might help to improve vaccination outcome.

Vedolizumab-mediated integrin α4β7 blockade does not control HIV-1SF162 rebound after combination antiretroviral therapy interruption in humanized mice.

The combined combination antiretroviral therapy (cART) and anti-α4β7 RM-Act-1 antibody therapy allows macaques to durably control simian immunodeficiency virus (SIV) rebound after withdrawal of the interventions. Here, we aimed to investigate whether vedolizumab (VDZ), a clinical-grade humanized anti-α4β7 antibody, would have similar effects in controlling live HIV-1 infection in humanized mice. The integrin α4β7 blockade by VDZ was evaluated on human primary memory CD4+ T (MEMT) cells and retinoic acid-induced gut-homing α4β7+MEMT cells (α4β7+MEMT) in vitro. The antiretroviral activity of VDZ was determined using pseudotyped R5-tropic HIV-1SF162, which displays binding activity to α4β7. The preventive and immunotherapeutic efficacies of VDZ were further investigated in humanized mice using the live HIV-1SF162 strain compared with RM-Act-1. VDZ effectively and dose-dependently blocked the binding of mucosal vascular addressin cell adhesion molecule-1 (MAdCAM-1), the native ligand of α4β7, to α4β7+MEMT cells. HIV-1SF162 not only displayed binding capacity to α4β7-expressing cells, but also showed an increased infectivity in retinoic acid-induced α4β7+MEMT cells pretreated with VDZ. Moreover, VDZ failed to prevent live HIV-1SF162 infection and did not reduce the peak viral load when administrated prior to viral challenge in humanized mice. Lastly, in immunotherapeutic settings, the withdrawal of combined cART with either VDZ or RM-Act-1 resulted in an uncontrolled HIV-1SF162 rebound in humanized mice, whereas the α4β7 molecules remained significantly blocked on circulating CD4+ T cells. VDZ neither prevents nor controls HIV-1SF162 infection both in vitro and in humanized mice. Our findings have significant implications to the clinical application of VDZ in HIV-1 preventive and immunotherapeutic interventions.

Bacillus Calmette-Gu\xe9rin Induces PD-L1 Expression on Antigen-Presenting Cells via Autocrine and Paracrine Interleukin-STAT3 Circuits

Bacillus Calmette-Guérin (BCG) is the only licensed vaccine for tuberculosis (TB), and is also used as an immunotherapy for bladder cancer and other malignancies due to its immunostimulatory properties. Mycobacteria spp., however, are well known for their numerous immune evasion mechanisms that limit the true potential of their therapeutic use. One such major mechanism is the induction of programmed death ligand-1 (PD-L1), which mitigates adaptive immune responses. Here, we sought to unravel the molecular pathways behind PD-L1 up-regulation on antigen-presenting cells (APCs) by BCG. We found that infection of APCs with BCG induced PD-L1 up-regulation, but that this did not depend on direct infection, suggesting a soluble mediator for this effect. BCG induced potent quantities of IL-6 and IL-10, and the downstream transcription factor STAT3 was hyper-phosphorylated. Intracellular analyses revealed that levels of PD-L1 molecules were associated with the STAT3 phosphorylation state, suggesting a causal link. Neutralisation of the IL-6 or IL-10 cytokine receptors dampened STAT3 phosphorylation and BCG-mediated up-regulation of PD-L1 on APCs. Pharmacological inhibition of STAT3 achieved the same effect, confirming an autocrine-paracrine cytokine loop as a mechanism for BCG-mediated up-regulation of PD-L1. Finally, an in vivo immunisation model showed that BCG vaccination under PD-L1 blockade could enhance antigen-specific memory CD4 T-cell responses. These novel findings could lead to refinement of BCG as both a vaccine for infectious disease and as a cancer immunotherapy.

Abstract P1-09-09: Octogenerian breast cancer was associated with higher infiltration of M2 macrophages and tregs and worse disease free survival

Abstract Backgrounds: It is known that elderly patients have worse prognosis of breast cancer and commonly the blame is on their medical comorbidities and access to care. We question this dogma and hypothesized that extreme elderly (octogenerians over 80 years old) have biologically worse cancer that can be defined by mutation load, tumor heterogeneity, and its tumor immune microenvironment. Patients and Methods: Two groups; Control (patients aged 40-65), and octogenerians (age over 80) at the time of breast cancer diagnosis were compared in The Cancer Genomic Atlas (TCGA; n=1093) and the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC; n=2506) cohorts. Cytolytic activity score (CYT), CIBERSORT analysis, tumor mutation load, as well as mutant-allele tumor heterogeneity (MATH) score were conducted as previously published. Results: The total number of patients in the control group and octogenarians were 675 and 54 in TCGA, and 1001 and 121 in METABRIC, respectively. Octogenerians had significantly worse disease free survival in addition to overall survival in both cohorts (p<0.01 in both), which suggested that they had worse cancer biology. In terms of subtypes, octogenerians had significantly higher rate of ER positive cancers than control group in both cohorts (75.3% vs 87.0%, p<0.01 in TCGA, 72.9% vs 90.0%, p<0.01 in METABRIC), but there was no significant deference in PgR or Her2 positivity. With regard of PAM50 classification, luminal-A and B subtypes were significantly higher in octogenarians (44.6% vs 34.7%, 31.4% vs 20.5%, respectively, p<0.01), whereas basal (7.4% vs 11.2%) and claudin-low (2.5% vs 11.8%) subtypes were significantly lower (p<0.05) in octogenarians in METBRIC cohort. Given that octogenerians had subtype with favorable prognosis, we examined whether they had higher mutation load or heterogeneity of the tumor. There were no significant difference in tumor mutation load and MATH score that reflect tumor heterogeneity in both cohorts. On the other hand, breast tumors of octogenerians were significantly associated with immune-suppressive cells, such as M2 type macrophages and regulatory T cells in both cohorts (p<0.05), whereas they were negatively associated with immune- eliminating cells, such as activated memory CD4 T-cells and M1 type of macrophages in METABRIC cohort (p<0.05). There was no significant difference in CYT in TCGA cohort. Conclusion: Our result demonstrated that octogenerians breast tumors were infiltrated with more immune-suppressive cells that may contribute to their biologically worse behavior. Citation Format: Okano M, Elkhanany A, Qi Q, Yan L, Takabe K. Octogenerian breast cancer was associated with higher infiltration of M2 macrophages and tregs and worse disease free survival [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-09-09.

Potent Antitumor T-Cell Memory Is Generated by Curative Viral Oncolytic Immunotherapy But Not Curative Chemotherapy.

Late developing breast cancer metastases are common and lethal despite treatment with adjuvant chemotherapy at the time of primary tumor excision. Stimulation of an antitumor immune response is an alternative strategy for preventing this devastating development. A mouse model of the human epidermal growth factor receptor 2 (HER2/neu)-positive mammary cancer was used to compare the antitumor memory T-cell response following tumor cure by viral oncolytic immunotherapy, chemotherapy, surgical excision, or surgical excision plus virus infection. Memory T-cell response was assessed by functional in vivo assays. Antitumor T-cell memory was generated most powerfully by curative viral oncolytic immunotherapy and poorly by curative chemotherapy. Cure by surgical excision generated an immune antitumor response which was increased by neo-adjuvant virus infection. CD4 memory T-cells were most potent. Virus infection of tumor generates an antitumor memory immune response and chemotherapy suppresses this response. Clinical trials testing adjuvant immune stimulation instead of chemotherapy may be worth exploring because memory antitumor T-cells have the unique potential to find and eliminate small nests of metastatic cancer cells in sanctuary sites and prevent emergence of tumors from dormant cancer cells.

Vecabrutinib Is Efficacious In Vivo in a Preclinical CLL Adoptive Transfer Model

Vecabrutinib Is Efficacious In Vivo in a Preclinical CLL Adoptive Transfer Model

Blimp-1 induces and Hobit maintains the cytotoxic mediator granzyme B in CD8 Tcells.

CD8 Tcells acquire cytotoxic molecules including granzyme B during effector differentiation. Both tissue-resident memory CD8 Tcells (Trm) and circulating CD45RA+ effector-type Tcells (Temra) cells have the ability to retain granzyme B protein expression into the memory phase, but it is unclear how this persistence of cytolytic activity is regulated during steady state. Previously, we have described that the transcriptional regulators Hobit and Blimp-1 have overlapping target genes that include granzyme B, but their impact on the regulation of cytotoxicity in Trm and Temra cells during homeostasis has remained unclear. We examined the expression regulation of Hobit and Blimp-1 in murine and human CD8 T-cells to determine their timeframe of activity. While Blimp-1 mRNA was expressed throughout effector and memory Tcells, Blimp-1 protein, was only transiently expressed during the effector stage. In contrast, Hobit mRNA and protein expression was stably maintained during quiescence, but downregulated after activation. Notably, Blimp-1 was required for expression of granzyme B in murine effector Tcells and Trm, while Hobit specifically regulated granzyme B in murine Trm during the memory phase. These findings suggest that Blimp-1 initiates cytotoxic effector function and that Hobit maintains cytotoxicity in a deployment-ready modus in Trm.

Dangerously Fit: Extracellular ATP Aids Memory T Cell Metabolism

In a recent issue of Nature, Borges da Silva etal. (2018) reveal that P2RX7, a receptor for extracellular ATP, promotes CD8 Tcell memory by enhancing metabolic fitness. This work links an ancient "danger" signal with long-term immunity.

Early programming and late-acting checkpoints governing the development of CD4 T-cell memory.

CD4 T cells contribute to protection against pathogens through numerous mechanisms. Incorporating the goal of memory CD4 T-cell generation into vaccine strategies therefore offers a powerful approach to improve their efficacy, especially in situations where humoral responses alone cannot confer long-term immunity. These threats include viruses such as influenza that mutate coat proteins to avoid neutralizing antibodies, but that are targeted by T cells that recognize more conserved protein epitopes shared by different strains. A major barrier in the design of such vaccines is that the mechanisms controlling the efficiency with which memory cells form remain incompletely understood. Here, we discuss recent insights into fate decisions controlling memory generation. We focus on the importance of three general cues: interleukin-2, antigen and co-stimulatory interactions. It is increasingly clear that these signals have a powerful influence on the capacity of CD4 T cells to form memory during two distinct phases of the immune response. First, through 'programming' that occurs during initial priming, and second, through 'checkpoints' that operate later during the effector stage. These findings indicate that novel vaccine strategies must seek to optimize cognate interactions, during which interleukin-2-, antigen- and co-stimulation-dependent signals are tightly linked, well beyond initial antigen encounter to induce robust memory CD4 T cells.

Peering into the HIV reservoir.

The main obstacle to HIV eradication is the establishment of a long-term persistent HIV reservoir. Although several therapeutic approaches have been developed to reduce and eventually eliminate the HIV reservoir, only a few have achieved promising results. A better knowledge of the mechanisms involved in the establishment and maintenance of HIV reservoir is of utmost relevance for the design of new therapeutic strategies aimed at purging it with the ultimate goal of achieving HIV eradication or alternatively a functional cure. In this regard, it is also important to take a close look into the cellular HIV reservoirs other than resting memory CD4 T-cells with key roles in reservoir maintenance that have been recently described. Unraveling the special characteristics of these HIV cellular compartments could aid us in designing new therapeutic strategies to deplete the latent HIV reservoir.

Effects of anti-CTLA-4 and anti-PD-1 on memory T-cell differentiation and resistance to tumor relapse

Abstract Clinical studies have shown that αPD-1 therapy mediates a greater response rate compared to αCTLA-4 according to RECIST criteria. However, it may not be as durable as αCTLA-4. 25% of patients who initially responded to αPD-1 have tumor relapse within 24 months. In contrast, the 10-year survival rate of patients treated with αCTLA-4 is at least ~25% suggesting a durable response. The goal of this study is to understand the relationship between memory T-cell formation in tumor models mediated by checkpoint antibodies and tumor relapse. Our results have shown that αCTLA-4 could induce a superior memory antitumor response during tumor rechallenge on mice compared to that treated with αPD-1 after 80 days. We also showed that this memory antitumor response was antigen-specific. These antigen-specific memory T-cells in mice that were treated with αCTLA-4 had better proliferative potential with cytokine producing function and more CD62L+CD44+ memory T-cells were converted back to CD62L-CD44+ effectors during rechallenge. We found that αCTLA-4 and αPD-1 facilitated the development of CD4 and CD8 memory T-cells respectively. We also demonstrated that the memory antitumor activity mediated by the combination of αCTLA-4 and αPD-1 overlapped with αCTLA-4 alone suggesting the effect of the combined treatment is dominated by αCTLA-4.