Polyfunctional and IFN- monofunctional human CD4+ T cell populations are molecularly distinct

Impact on parasitemia, survival time and pro-inflammatory immune response in mice infected with Plasmodium berghei treated with Eleutherine plicata

In vitro studies with Plasmodium falciparum have demonstrated the antiparasitic activity of E. plicata, attributed to its naphthoquinones. This study reports on pro-inflammatory changes in mice infected with P. berghei and correlates these changes with parasitemia and survival. The ethanol extract of Eleutherine plicata (EEEp) was fractionated under reflux to obtain the dichloromethane fraction (FDMEp) and isolated compounds from E. plicata, relating these to survival time and parasitemia. Antimalarial activity was evaluated using the Peters suppressive test, with mice infected with Plasmodium berghei and treated with E. plicata, assessing parasitemia and survival over 30 days. The pro-inflammatory profile was determined by measuring interleukin-10, interferon-γ (IFN-γ), and nitric oxide levels. EEEp, FDMEp, and eleutherol showed activity on the 5th day of infection, with only FDMEp being active on the 8th day. Treatment with EEEp and FDMEp extended animal survival, reduced IFN-γ and NO levels, and increased IL-10 levels. Eleutherol significantly altered the response, with eleutherol glucuronide seemingly active by binding to lactate dehydrogenase, inhibiting hemozoin metabolism, leading to parasite death. Pro-inflammatory changes did not appear to correlate with survival and reduced parasitemia. In summary, FDMEp and eleutherol reduced parasitemia, extended survival, and modulated the inflammatory response. FDMEp and eleutherol are promising candidates for developing new antimalarial drugs.

Dysfunctional host cellular immune responses are associated with mortality in melioidosis

Melioidosis is a tropical infection caused by the intracellular pathogen Burkholderia pseudomallei, an underreported and emerging global threat. As melioidosis-associated mortality is frequently high despite antibiotics, novel management strategies are critically needed. Therefore, we sought to determine whether functional changes in the host innate and adaptive immune responses are induced during acute melioidosis and are associated with outcome. Using a unique whole blood stimulation assay developed for use in resource-limited settings, we examined induced cellular functional and phenotypic changes in a cohort of patients with bacteremic melioidosis prospectively enrolled within 24 h of positive blood culture and followed for 28 days. Compared to healthy controls, melioidosis survivors generated an IL-17 response mediated by Th17 cells and terminally-differentiated effector memory CD8+ T cells (P < .05, both), persisting to 28 days after enrolment. Furthermore, melioidosis survivors developed polyfunctional cytokine production in CD8+ T cells (P < .01). Conversely, a reduction in CCR6+ CD4+ T cells was associated with higher mortality, even after adjustments for severity of illness (P = 0.004). Acute melioidosis was also associated with a profound acute impairment in monocyte function as stimulated cytokine responses were reduced in classical, intermediate and non-classical monocytes. Impaired monocyte cytokine function improved by 28-days after enrolment. These data suggest that IL-17 mediated cellular responses may be contributors to host defense during acute melioidosis, and that innate immune function may be impaired. These insights could provide novel targets for the development of therapies and vaccine targets in this frequently lethal disease.

Bivalent norovirus mRNA vaccine elicits cellular and humoral responses protecting human enteroids from GII.4 infection

Nucleoside-modified mRNA-LNP vaccines have revolutionized vaccine development against infectious pathogens due to their ability to elicit potent humoral and cellular immune responses. In this article, we present the results of the first norovirus vaccine candidate employing mRNA-LNP platform technology. The mRNA-LNP bivalent vaccine encoding the major capsid protein VP1 from GI.1 and GII.4 of human norovirus, generated high levels of neutralizing antibodies, robust cellular responses, and effectively protected human enteroids from infection by the most prevalent genotype (GII.4). These results serve as a proof of concept, demonstrating that a modified-nucleoside mRNA-LNP vaccine based on norovirus VP1 sequences can stimulate an immunogenic response in vivo and generates neutralizing antibodies capable of preventing viral infection in models of human gastrointestinal tract infection.

Safety and Immunogenicity Study of a Bivalent Vaccine for Combined Prophylaxis of COVID-19 and Influenza in Non-Human Primates

BACKGROUND

Influenza and SARS-CoV-2 viruses are two highly variable pathogens. We have developed a candidate bivalent live vaccine based on the strain of licensed A/Leningrad/17-based cold-adapted live attenuated influenza vaccine (LAIV) of H3N2 subtype, which expressed SARS-CoV-2 immunogenic T-cell epitopes. A cassette encoding fragments of S and N proteins of SARS-CoV-2 was inserted into the influenza NA gene using the P2A autocleavage site. In this study, we present the results of preclinical evaluation of the developed bivalent vaccine in a non-human primate model.

METHODS

Rhesus macaques (Macaca mulatta) (n = 3 per group) were immunized intranasally with 7.5 lg EID50 of the LAIV/CoV-2 bivalent vaccine, a control non-modified H3N2 LAIV or a placebo (chorioallantoic fluid) using a sprayer device, twice, with a 28-day interval. The blood samples were collected at days 0, 3, 28 and 35 for hematological and biochemical assessment. Safety was also assessed by monitoring body weight, body temperature and clinical signs of the disease. Immune responses to influenza virus were assessed both by determining serum antibody titers in hemagglutination inhibition assay, microneutralization assay and IgG ELISA. T-cell responses were measured both to influenza and SARS-CoV-2 antigens using ELISPOT and flow cytometry. Three weeks after the second immunization, animals were challenged with 105 PFU of Delta SARS-CoV-2. The body temperature, weight and challenge virus shedding were monitored for 5 days post-challenge. In addition, virus titers in various organs and histopathology were evaluated on day 6 after SARS-CoV-2 infection.

RESULTS

There was no toxic effect of the immunizations on the hematological and coagulation hemostasis of animals. No difference in the dynamics of the average weight and thermometry results were found between the groups of animals. Both LAIV and LAIV/CoV-2 variants poorly replicated in the upper respiratory tract of rhesus macaques. Nevertheless, despite this low level of virus shedding, influenza-specific serum IgG responses were detected in the group of monkeys immunized with the LAIV/CoV-2 bivalent but not in the LAIV group. Furthermore, T-cell responses to both influenza and SARS-CoV-2 viruses were detected in the LAIV/CoV-2 vaccine group only. The animals were generally resistant to SARS-CoV-2 challenge, with minimal virus shedding in the placebo and LAIV groups. Histopathological changes in vaccinated animals were decreased compared to the PBS group, suggesting a protective effect of the chimeric vaccine candidate.

CONCLUSIONS

The candidate bivalent vaccine was safe and immunogenic for non-human primates and warrants its further evaluation in clinical trials.

Cytomegalovirus immunity in high-risk liver transplant recipients following preemptive antiviral therapy versus prophylaxis

CMV-specific T cells, NK cells, and neutralizing antibodies (nAbs) were assessed in a randomized trial of CMV prevention with preemptive antiviral therapy (PET) versus prophylactic antiviral therapy (PRO) in donor-seropositive/recipient-seronegative (D+R-) liver transplant recipients (LTxR) at 100 days (end of intervention) and at 6 and 12 months after transplant. The PET group had significantly increased numbers of circulating polyfunctional T cells, NK cells, and nAbs compared with the PRO group at day 100, and several CMV immune parameters remained significantly higher by 12 months after transplant. Among PET recipients, preceding CMV viremia (vs. no preceding viremia) was associated with significantly higher levels of most CMV immune parameters at day 100. Higher numbers of CMV-specific polyfunctional T cells and NKG2C+ NK cells at day 100 were associated with a decreased incidence of CMV disease in multivariable Cox regression. The strongest associations with protection against CMV disease were with increased numbers of CMV-specific polyfunctional CD4+ T cells, CD3negCD56dimCD57negNKG2Cpos cells, and CD3negCD56dimCD57posNKG2Cpos NK cells. Our results suggest that PET is superior to PRO for CMV disease prevention by allowing low-level CMV replication and associated antigen exposure that is promptly controlled by antiviral therapy and facilitates enhanced CMV protective immunity in D+R- LTxR.

Immature dendritic cell-targeting mRNA vaccine expressing PfCSP enhances protective immune responses against Plasmodium liver infection

Resurgence in malaria has been noted in 2022 with 249 million clinical cases resulting in 608,000 deaths, mostly in children under five. Two vaccines, RTS, S, and more recently R21, targeting the circumsporozoite protein (CSP) are recommended by the WHO but are not yet widely available. Strong humoral responses to neutralize sporozoites before they can infect the hepatocytes are important for vaccine-mediated protection. Suboptimal protection conferred by these first-generation vaccines highlight the need for approaches to improve vaccine-induced immune responses. With the recent success of mRNA-LNP vaccines against COVID-19, there is growing interest in leveraging this approach to enhance malaria vaccines. Here, we present the development of a novel chemokine fusion mRNA vaccine aimed at boosting immune responses to PfCSP by targeting the immunogen to immature dendritic cells (iDC). Vaccination of mice with mRNA encoding full-length CSP fused to macrophage inflammatory protein 3 alpha (MIP3α) encapsulated within lipid nanoparticles (LNP) elicited robust CD4+ T cell responses and enhanced antibody titers against NANP repeat epitopes compared to a conventional CSP mRNA-LNP vaccine. Importantly, the CSP-MIP3α fusion vaccine provided significantly greater protection against liver infection upon challenge with P. berghei PfCSP transgenic sporozoites. This enhanced protection was associated with multifunctional CD4+ T cells levels and anti-NANP repeat titers. This study highlights the potential to augment immune responses to PfCSP through iDC targeting and bolster protection against malaria liver infection.

Hybrid lineages of CD4+ T cells: a handbook update

CD4+ T lymphocytes have been classified into several lineages, according to their gene expression profiles and their effector responses. Interestingly, recent evidence is showing that many lineages could yield hybrid phenotypes with unique properties and functions. It has been reported that such hybrid lineages might underlie pathologies or may function as effector cells with protection capacities against molecular threats. In this work, we reviewed the characteristics of the hybrid lineages reported in the literature, in order to identify the expression profiles that characterize them and the markers that could be used to identify them. We also review the differentiation cues that elicit their hybrid origin and what is known about their physiological roles.

Time-resolved assessment of single-cell protein secretion by sequencing

Secreted proteins play critical roles in cellular communication. Methods enabling concurrent measurement of cellular protein secretion, phenotypes and transcriptomes are still unavailable. Here we describe time-resolved assessment of protein secretion from single cells by sequencing (TRAPS-seq). Released proteins are trapped onto the cell surface and probed by oligonucleotide-barcoded antibodies before being simultaneously sequenced with transcriptomes in single cells. We demonstrate that TRAPS-seq helps unravel the phenotypic and transcriptional determinants of the secretion of pleiotropic TH1 cytokines (IFNγ, IL-2 and TNF) in activated T cells. In addition, we show that TRAPS-seq can be used to track the secretion of multiple cytokines over time, uncovering unique molecular signatures that govern the dynamics of single-cell cytokine secretions. Our results revealed that early central memory T cells with CD45RA expression (TCMRA) are important in both the production and maintenance of polyfunctional cytokines. TRAPS-seq presents a unique tool for seamless integration of secretomics measurements with multi-omics profiling in single cells.

Antigen-Specific Intraocular Cytokine Responses Distinguish Ocular Tuberculosis From Undifferentiated Uveitis in Tuberculosis-Immunoreactive Patients

PURPOSE

To compare antigen-specific intraocular immune responses between different clinical phenotypes of tuberculin skin test (TST)-positive and TST-negative uveitis.

DESIGN

Single center, retrospective cross-sectional study.

METHODS

Patients requiring diagnostic or therapeutic vitrectomy for the management of intraocular inflammation were divided into 3 groups based on Standardization of Uveitis Nomenclature (SUN) classification criteria for tubercular uveitis. Group 1 included patients with ocular tuberculosis (OTB; n = 23) who were TST-positive patients, met the SUN criteria, and/or had a polymerase chain reaction (PCR)-positive test for TB. Group 2 included patients with uveitis of unknown origin (UNK; n = 24) who were undifferentiated TST-positive patients who had not met SUN criteria. Group 3 included non-TB uveitis patients (n = 24) who were TST-negative either with or without a well-defined non-TB diagnosis. Total vitreous cells were activated with Mycobacterium tuberculosis-specific Early Secreted Antigenic Target-6 (ESAT-6) or the retinal autoantigen, interphotoreceptor retinoid-binding protein peptide (pIRBP 1-20), stained for intracellular interferon gamma (IFNγ), tumor necrosis factor-alfa (TNFα), and interleukin 17 (IL-17), and analyzed by flow cytometry. Antigen-specific single and dual (polyfunctional) cytokine responses to ESAT-6 and IRBP were compared between the 3 groups.

RESULTS

All cytokine responses to ESAT-6 were higher in the UNK group compared with the non-TB control subjects, while all except IL-17 were comparable between the OTB and non-TB groups. Polyfunctional responses-IFNγ/IL-17 (P = .002), TNFα/IL-17 (P = .02), and TNFα/IFNγ (P = .01)-were significantly greater for UNK than the OTB group. Polyfunctional cells also produced more cytokine per cell than respective monofunctional cells. IRBP cytokine responses were comparable between different groups and were not affected by the clinical phenotype or duration of disease.

CONCLUSION

The intraocular polyfunctional cytokine response is stronger in undifferentiated TST-positive uveitis than in OTB patients, likely representing an exaggerated anti-TB immune response rather than active infection.

Vaccine co-display of CSP and Pfs230 on liposomes targeting two Plasmodium falciparum differentiation stages

A vaccine targeting multiple stages of the Plasmodium falciparum parasite life cycle is desirable. The sporozoite surface Circumsporozoite Protein (CSP) is the target of leading anti-infective P. falciparum pre-erythrocytic vaccines. Pfs230, a sexual-stage P. falciparum surface protein, is currently in trials as the basis for a transmission-blocking vaccine, which inhibits parasite development in the mosquito vector. Here, recombinant full-length CSP and a Pfs230 fragment (Pfs230D1+) are co-displayed on immunogenic liposomes to induce immunity against both infection and transmission. Liposomes contain cobalt-porphyrin phospholipid (CoPoP), monophosphoryl lipid A and QS-21, and rapidly bind His-tagged CSP and Pfs230D1+ upon admixture to form bivalent particles that maintain reactivity with conformational monoclonal antibodies. Use of multicolor fluorophore-labeled antigens reveals liposome binding upon admixture, stability in serum and enhanced uptake in murine macrophages in vitro. Bivalent liposomes induce humoral and cellular responses against both CSP and Pfs230D1+. Vaccine-induced antibodies reduce parasite numbers in mosquito midguts in a standard membrane feeding assay. Mice immunized with liposome-displayed antigens or that passively receive antibodies from immunized rabbits have reduced parasite liver burden following challenge with transgenic sporozoites expressing P. falciparum CSP.

Dietary Cholesterol Causes Inflammatory Imbalance and Exacerbates Morbidity in Mice Infected with Influenza A Virus

Influenza is a common cause of pneumonia-induced hospitalization and death, but how host factors function to influence disease susceptibility or severity has not been fully elucidated. Cellular cholesterol levels may affect the pathogenesis of influenza infection, as cholesterol is crucial for viral entry and replication, as well as immune cell proliferation and function. However, there is still conflicting evidence on the extent to which dietary cholesterol influences cholesterol metabolism. In this study, we examined the effects of a high-cholesterol diet in modulating the immune response to influenza A virus (IAV) infection in mice. Mice were fed a standard or a high-cholesterol diet for 5 wk before inoculation with mouse-adapted human IAV (Puerto Rico/8/1934), and tissues were collected at days 0, 4, 8, and 16 postinfection. Cholesterol-fed mice exhibited dyslipidemia characterized by increased levels of total serum cholesterol prior to infection and decreased triglycerides postinfection. Cholesterol-fed mice also displayed increased morbidity compared with control-fed mice, which was neither a result of immunosuppression nor changes in viral load. Instead, transcriptomic analysis of the lungs revealed that dietary cholesterol caused upregulation of genes involved in viral-response pathways and leukocyte trafficking, which coincided with increased numbers of cytokine-producing CD4⁺ and CD8⁺ T cells and infiltrating dendritic cells. Morbidity as determined by percent weight loss was highly correlated with numbers of cytokine-producing CD4⁺ and CD8⁺ T cells as well as granulocytes. Taken together, dietary cholesterol promoted IAV morbidity via exaggerated cellular immune responses that were independent of viral load.

Non-coding RNAs in malaria infection

Malaria is one of the most severe infectious diseases affecting humans and it is caused by protozoan pathogens of the species Plasmodium (spp.). The malaria parasite Plasmodium is characterized by a complex, multistage life cycle that requires tight gene regulation which allows for host invasion and defense against host immune responses. Unfortunately, the mechanisms regulating gene expression during Plasmodium infection remain largely elusive, though several lines of evidence implicate a major involvement of non-coding RNAs (ncRNAs). The ncRNAs have been found to play a key role in regulating transcriptional and post-transcriptional events in a broad range of organisms including Plasmodium. In Plasmodium ncRNAs have been shown to regulate key events in the multistage life cycle and virulence ability. Here we review recent progress involving ncRNAs (microRNAs, long non-coding RNAs, and circular RNAs) and their role as regulators of gene expression during Plasmodium infection in human hosts with focus on the possibility of using these molecules as biomarkers for monitoring disease status. We also discuss the surprising function of ncRNAs in mediating the complex interplay between parasite and human host and future perspectives of the field. This article is categorized under: RNA in Disease and Development > RNA in Disease.

Loss of balance between protective and pro-inflammatory synovial tissue T-cell polyfunctionality predates clinical onset of rheumatoid arthritis

OBJECTIVES

This study investigates pathogenic and protective polyfunctional T-cell responses in patient with rheumatoid arthritis (RA), individuals at risk (IAR) and healthy control (HC) synovial-tissue biopsies and identifies the presence of a novel population of pathogenic polyfunctional T-cells that are enriched in the RA joint prior to the development of clinical inflammation.

METHODS

Pathway enrichment analysis of previously obtained RNAseq data of synovial biopsies from RA (n=118), IAR (n=20) and HC (n=44) was performed. Single-cell synovial tissue suspensions from RA (n=10), IAR (n=7) and HC (n=7) and paired peripheral blood mononuclear cells (PBMC) were stimulated in vitro and polyfunctional synovial T-cell subsets examined by flow cytometric analysis, simplified presentation of incredibly complex evaluations (SPICE) and FlowSom clustering. Flow-imaging was utilised to confirm specific T-cell cluster identification. Fluorescent lifetime imaging microscopy (FLIM) was used to visualise metabolic status of sorted T-cell populations.

RESULTS

Increased plasticity of Tfh cells and CD4 T-cell polyfunctionality with enriched memory Treg cell responses was demonstrated in RA patient synovial tissue. Synovial-tissue RNAseq analysis reveals that enrichment in T-cell activation and differentiation pathways pre-dates the onset of RA. Switch from potentially protective IL-4 and granulocyte macrophage colony stimulating factor (GMCSF) dominated polyfunctional CD4 T-cell responses towards pathogenic polyfunctionality is evident in patient with IAR and RA synovial tissue. Cluster analysis reveals the accumulation of highly polyfunctional CD4+ CD8dim T-cells in IAR and RA but not HC synovial tissue. CD4+ CD8dim T-cells show increased utilisation of oxidative phosphorylation, a characteristic of metabolically primed memory T-cells. Frequency of synovial CD4+ CD8dim T-cells correlates with RA disease activity.

CONCLUSION

Switch from potentially protective to pathogenic T-cell polyfunctionality pre-dates the onset of clinical inflammation and constitutes an opportunity for therapeutic intervention in RA.

A T-Cell Epitope-Based Multi-Epitope Vaccine Designed Using Human HLA Specific T Cell Epitopes Induces a Near-Sterile Immunity against Experimental Visceral Leishmaniasis in Hamsters

Visceral leishmaniasis is a neglected tropical disease affecting 12 million people annually. Even in the second decade of the 21st century, it has remained without an effective vaccine for human use. In the current study, we designed three multiepitope vaccine candidates by the selection of multiple IFN-γ inducing MHC-I and MHC-II binder T-cell specific epitopes from three previously identified antigen genes of Leishmania donovani from our lab by an immuno-informatic approach using IFNepitope, the Immune Epitope Database (IEDB) T cell epitope identification tools, NET-MHC-1, and NET MHC-2 webservers. We tested the protective potential of these three multiepitope proteins as a vaccine in a hamster model of visceral leishmaniasis. The immunization data revealed that the vaccine candidates induced a very high level of Th1 biased protective immune response in-vivo in a hamster model of experimental visceral leishmaniasis, with one of the candidates inducing a near-sterile immunity. The vaccinated animals displayed highly activated monocyte macrophages with the capability of clearing intracellular parasites due to increased respiratory burst. Additionally, these proteins induced activation of polyfunctional T cells secreting INF-γ, TNF-α, and IL-2 in an ex-vivo stimulation of human peripheral blood mononuclear cells, further supporting the protective nature of the designed candidates.

Immunoregulatory properties of a crude extraction fraction rich in polysaccharide from Chrysanthemum zawadskii Herbich var. latilobum and its potential role as a vaccine adjuvant

The objective of the current study was to demonstrate the immunostimulatory effects of a polysaccharide isolated from Chrysanthemum zawadskii Herbich var. latilobum leaves (CP) and evaluate its potential as a vaccine adjuvant. Results showed that CP induced maturation of the dendritic cells (DCs). In addition, CP-treated DCs activated naïve T cells to polarized CD4+ and CD8+ T cells and substantially induced the production of IFN-γ and IL-2 in vitro. Furthermore, CP initiated the maturation of DCs via the activation of MAPK and NF-κB signaling pathways. Interestingly, systemic administration of CP-treated DCs pulsed with ovalbumin (OVA) peptides significantly enhanced the immune response in vivo, which included the generation of antigen (OVA)-specific polyfunctional T cells, increased cytotoxic T lymphocyte activity, induction of Th1-mediated humoral immunity, and suppression of tumor growth. Taken together, our study highlighted the immunoregulatory activity of CP as well as its potential as a candidate vaccine adjuvant.

Immune exhaustion in chronic Chagas disease: Pro-inflammatory and immunomodulatory action of IL-27 in vitro

In chronic Chagas disease, Trypanosoma cruzi-specific T-cell function decreases over time, and alterations in the homeostatic IL-7/IL-7R axis are evident, consistent with a process of immune exhaustion. IL-27 is an important immunoregulatory cytokine that shares T-cell signaling with IL-7 and other cytokines of the IL-12 family and might be involved in the transcriptional regulation of T-cell function. Here, we evaluated the expression and function of IL-27R in antigen-experienced T cells from subjects with chronic Chagas disease and assessed whether in vitro treatment with IL-27 and IL-7 might improve T. cruzi-specific polyfunctional T-cell responses. In vitro exposure of PBMCs to T. cruzi induced a downregulation of IL-27R in CD4+ T cells and an upregulation in CD8+ T cells in subjects without heart disease, while IL-27R expression remained unaltered in subjects with more severe clinical stages. The modulation of IL-27R was associated with functional signaling through STAT3 and STAT5 and induction of the downstream genes TBX21, EOMES and CXCL9 in response to IL-27. In vitro treatment of PBMCs with IL-27 and IL-7 improved monofunctional and polyfunctional Th1 responses, accompanied by the induction of IL-10 and Bcl-2 expression in subjects without heart disease but did not improve those in subjects with cardiomyopathy. Our findings support the process of desensitization of the IL-27/IL-27R pathway along with disease severity and that the pro-inflammatory and immunomodulatory mechanisms of IL-27 might be interconnected.

A guide to investigating immune responses elicited by whole-sporozoite pre-erythrocytic vaccines against malaria

In the last few decades, considerable efforts have been made toward the development of efficient vaccines against malaria. Whole-sporozoite (Wsp) vaccines, which induce efficient immune responses against the pre-erythrocytic (PE) stages (sporozoites and liver forms) of Plasmodium parasites, the causative agents of malaria, are among the most promising immunization strategies tested until present. Several Wsp PE vaccination approaches are currently under evaluation in the clinic, including radiation- or genetically-attenuated Plasmodium sporozoites, live parasites combined with chemoprophylaxis, or genetically modified rodent Plasmodium parasites. In addition to the assessment of their protective efficacy, clinical trials of Wsp PE vaccine candidates inevitably involve the thorough investigation of the immune responses elicited by vaccination, as well as the identification of correlates of protection. Here, we review the main methodologies employed to dissect the humoral and cellular immune responses observed in the context of Wsp PE vaccine clinical trials and discuss future strategies to further deepen the knowledge generated by these studies, providing a toolbox for the in-depth analysis of vaccine-induced immunogenicity.

Human CD8 T-stem cell memory subsets phenotypic and functional characterization are defined by expression of CD122 or CXCR3

Long-lived T-memory stem cells (T_SCM ) are key to both naturally occurring and vaccine-conferred protection against infection. These cells are characterized by the CD45RA⁺ CCR7⁺ CD95⁺ phenotype. Significant heterogeneity within the T_SCM population is recognized, but distinguishing surface markers and functional characterization of potential subsets are lacking. Human CD8 T_SCM subsets were identified in healthy subjects who had been previously exposed to CMV or Influenza (Flu) virus in flow cytometry by expression of CD122 or CXCR3, and then characterized in proliferation, multipotency, self-renewal, and intracellular cytokine production (TNF-α, IL-2, IFN-γ), together with transcriptomic profiles. The T_SCM CD122^hi -expressing subset (versus CD122^lo ) demonstrated greater proliferation, greater multipotency, and enhanced polyfunctionality with higher frequencies of triple positive (TNF-α, IL-2, IFN-γ) cytokine-producing cells upon exposure to recall antigen. The T_SCM CXCR3^lo subpopulation also had increased proliferation and polyfunctional cytokine production. Transcriptomic analysis further showed that the T_SCM CD122^hi population had increased expression of activation and homing molecules, such as Ccr6, Cxcr6, Il12rb, and Il18rap, and downregulated cell proliferation inhibitors, S100A8 and S100A9. These data reveal that the T_SCM CD122^hi phenotype is associated with increased proliferation, enhanced multipotency and polyfunctionality with an activated memory-cell like transcriptional profile, and hence, may be favored for induction by immunization and for adoptive immunotherapy.

Age-dependency of terminal ileum tissue resident memory T cell responsiveness profiles to S. Typhi following oral Ty21a immunization in humans

BACKGROUND

The impact of aging on the immune system is unequivocal and results in an altered immune status termed immunosenescence. In humans, the mechanisms of immunosenescence have been examined almost exclusively in blood. However, most immune cells are present in tissue compartments and exhibit differential cell (e.g., memory T cells -TM) subset distributions. Thus, it is crucial to understand immunosenescence in tissues, especially those that are exposed to pathogens (e.g., intestine). Using a human model of oral live attenuated typhoid vaccine, Ty21a, we investigated the effect of aging on terminal ileum (TI) tissue resident memory T (TRM) cells. TRM provide immediate adaptive effector immune responsiveness at the infection site. However, it is unknown whether aging impacts TRM S. Typhi-responsive cells at the site of infection (e.g., TI). Here, we determined the effect of aging on the induction of TI S. Typhi-responsive TRM subsets elicited by Ty21a immunization.

RESULTS

We observed that aging impacts the frequencies of TI-lamina propria mononuclear cells (LPMC) TM and TRM in both Ty21a-vaccinated and control groups. In unvaccinated volunteers, the frequencies of LPMC CD103- CD4+ TRM displayed a positive correlation with age whilst the CD4/CD8 ratio in LPMC displayed a negative correlation with age. We observed that elderly volunteers have weaker S. Typhi-specific mucosal immune responses following Ty21a immunization compared to adults. For example, CD103+ CD4+ TRM showed reduced IL-17A production, while CD103- CD4+ TRM exhibited lower levels of IL-17A and IL-2 in the elderly than in adults following Ty21a immunization. Similar results were observed in LPMC CD8+ TRM and CD103- CD8+ T cell subsets. A comparison of multifunctional (MF) profiles of both CD4+ and CD8+ TRM subsets between elderly and adults also showed significant differences in the quality and quantity of elicited single (S) and MF responses.

CONCLUSIONS

Aging influences tissue resident TM S. Typhi-specific responses in the terminal ileum following oral Ty21a-immunization. This study is the first to provide insights in the generation of local vaccine-specific responses in the elderly population and highlights the importance of evaluating tissue immune responses in the context of infection and aging.

TRIAL REGISTRATION

This study was approved by the Institutional Review Board and registered on ClinicalTrials.gov (identifier NCT03970304 , Registered 29 May 2019 - Retrospectively registered).

CD4+ T Cells: Multitasking Cells in the Duty of Cancer Immunotherapy

Cancer immunotherapy activates the immune system to specifically target malignant cells. Research has often focused on CD8+ cytotoxic T cells, as those have the capacity to eliminate tumor cells after specific recognition upon TCR-MHC class I interaction. However, CD4+ T cells have gained attention in the field, as they are not only essential to promote help to CD8+ T cells, but are also able to kill tumor cells directly (via MHC-class II dependent recognition) or indirectly (e.g., via the activation of other immune cells like macrophages). Therefore, immunotherapy approaches have shifted from only stimulating CD8+ T cells to targeting and assessing both, CD4+ and CD8+ T cell subsets. Here, we discuss the various subsets of CD4+ T cells, their plasticity and functionality, their relevance in the antitumor immune response in patients affected by cancer, and their ever-growing role in therapeutic approaches for human cancer.

A population of CD4hiCD38hi T cells correlates with disease severity in patients with acute malaria

OBJECTIVE

CD4⁺ T cells are critical mediators of immunity to Plasmodium spp. infection, but their characteristics during malarial episodes and immunopathology in naturally infected adults are poorly defined. Flow cytometric analysis of PBMCs from patients with either P. falciparum or P. knowlesi malaria revealed a pronounced population of CD4⁺ T cells co-expressing very high levels of CD4 and CD38 we have termed CD4^hiCD38^hi T cells. We set out to gain insight into the function of these novel cells.

METHODS

CD4⁺ T cells from 18 patients with P. falciparum or P. knowlesi malaria were assessed by flow cytometry and sorted into populations of CD4^hiCD38^hi or CD4^norm T cells. Gene expression in the sorted populations was assessed by qPCR and NanoString.

RESULTS

CD4^hiCD38^hi T cells expressed high levels of CD4 mRNA and canonical type 1 regulatory T-cell (TR1) genes including IL10, IFNG, LAG3 and HAVCR2 (TIM3), and other genes with relevance to cell migration and immunomodulation. These cells increased in proportion to malaria disease severity and were absent after parasite clearance with antimalarials.

CONCLUSION

In naturally infected adults with acute malaria, a prominent population of type 1 regulatory T cells arises that can be defined by high co-expression of CD4 and CD38 (CD4^hiCD38^hi) and that correlates with disease severity in patients with falciparum malaria. This study provides fundamental insights into T-cell biology, including the first evidence that CD4 expression is modulated at the mRNA level. These findings have important implications for understanding the balance between immunity and immunopathology during malaria.

A Longitudinal Study of Immune Cells in Severe COVID-19 Patients

Little is known about the time-dependent immune responses in severe COVID-19. Data of 15 consecutive patients were sequentially recorded from intensive care unit admission. Lymphocyte subsets and total monocyte and subsets counts were monitored as well as the expression of HLA-DR. For 5 patients, SARS-CoV-2-specific T-cell polyfunctionality was assessed against Spike and Nucleoprotein SARS-CoV-2 peptides. Non-specific inflammation markers were increased in all patients. Median monocyte HLA-DR expression was below the 8,000 AB/C threshold defining acquired immunodepression. A "V" trend curve for lymphopenia, monocyte numbers, and HLA-DR expression was observed with a nadir between days 11 and 14 after symptoms' onset. Intermediate CD14++CD16+ monocytes increased early with a reduction in classic CD14++CD16- monocytes. Polyfunctional SARS-Cov-2-specific CD4 T-cells were present and functional, whereas virus-specific CD8 T-cells were less frequent and not efficient. We report a temporal variation of both innate and adaptive immunity in severe COVID-19 patients, helpful in guiding therapeutic decisions (e.g. anti-inflammatory vs. immunostimulatory ones). We describe a defect in virus-specific CD8 T-cells, a potential biomarker of clinical severity. These combined data also provide helpful knowledge for vaccine design.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov/, identifier NCT04386395.

Human Salmonella Typhi exposure generates differential multifunctional cross-reactive T-cell memory responses against Salmonella Paratyphi and invasive nontyphoidal Salmonella

Objective

There are no vaccines for most of the major invasive Salmonella strains causing severe infection in humans. We evaluated the specificity of adaptive T memory cell responses generated after Salmonella Typhi exposure in humans against other major invasive Salmonella strains sharing capacity for dissemination.

Methods

T memory cells from eleven volunteers who underwent controlled oral challenge with wtS. Typhi were characterised by flow cytometry for cross‐reactive cellular cytokine/chemokine effector responses or evidence of degranulation upon stimulation with autologous B‐lymphoblastoid cells infected with either S. Typhi, Salmonella Paratyphi A (PA), S. Paratyphi B (PB) or an invasive nontyphoidal Salmonella strain of the S. Typhimurium serovar (iNTSTy).

Results

Blood T‐cell effector memory (T_EM) responses after exposure to S. Typhi in humans evolve late, peaking weeks after infection in most volunteers. Induced multifunctional CD4⁺ Th1 and CD8⁺ T_EM cells elicited after S. Typhi challenge were cross‐reactive with PA, PB and iNTSTy. The magnitude of multifunctional CD4⁺ T_EM cell responses to S. Typhi correlated with induction of cross‐reactive multifunctional CD8⁺ T_EM cells against PA, PB and iNTSTy. Highly multifunctional subsets and T central memory and T effector memory cells that re‐express CD45 (T_EMRA) demonstrated less heterologous T‐cell cross‐reactivity, and multifunctional Th17 elicited after S. Typhi challenge was not cross‐reactive against other invasive Salmonella.

Conclusion

Gaps in cross‐reactive immune effector functions in human T‐cell memory compartments were highly dependent on invasive Salmonella strain, underscoring the importance of strain‐dependent vaccination in the design of T‐cell‐based vaccines for invasive Salmonella.

Transcriptional Profiling of CD8+ CMV-Specific T Cell Functional Subsets Obtained Using a Modified Method for Isolating High-Quality RNA From Fixed and Permeabilized Cells

Previous studies suggest that the presence of antigen-specific polyfunctional T cells is correlated with improved pathogen clearance, disease control, and clinical outcomes; however, the molecular mechanisms responsible for the generation, function, and survival of polyfunctional T cells remain unknown. The study of polyfunctional T cells has been, in part, limited by the need for intracellular cytokine staining (ICS), necessitating fixation and cell membrane permeabilization that leads to unacceptable degradation of RNA. Adopting elements from prior research efforts, we developed and optimized a modified protocol for the isolation of high-quality RNA (i.e., RIN > 7) from primary human T cells following aldehyde-fixation, detergent-based permeabilization, intracellular cytokines staining, and sorting. Additionally, this method also demonstrated utility preserving RNA when staining for transcription factors. This modified protocol utilizes an optimized combination of an RNase inhibitor and high-salt buffer that is cost-effective while maintaining the ability to identify and resolve cell populations for sorting. Overall, this protocol resulted in minimal loss of RNA integrity, quality, and quantity during cytoplasmic staining of cytokines and subsequent flourescence-activated cell sorting. Using this technique, we obtained the transcriptional profiles of functional subsets (i.e., non-functional, monofunctional, bifunctional, polyfunctional) of CMV-specific CD8+T cells. Our analyses demonstrated that these functional subsets are molecularly distinct, and that polyfunctional T cells are uniquely enriched for transcripts involved in viral response, inflammation, cell survival, proliferation, and metabolism when compared to monofunctional cells. Polyfunctional T cells demonstrate reduced activation-induced cell death and increased proliferation after antigen re-challenge. Further in silico analysis of transcriptional data suggested a critical role for STAT5 transcriptional activity in polyfunctional cell activation. Pharmacologic inhibition of STAT5 was associated with a significant reduction in polyfunctional cell cytokine expression and proliferation, demonstrating the requirement of STAT5 activity not only for proliferation and cell survival, but also cytokine expression. Finally, we confirmed this association between CMV-specific CD8+ polyfunctionality with STAT5 signaling also exists in immunosuppressed transplant recipients using single cell transcriptomics, indicating that results from this study may translate to this vulnerable patient population. Collectively, these results shed light on the mechanisms governing polyfunctional T cell function and survival and may ultimately inform multiple areas of immunology, including but not limited to the development of new vaccines, CAR-T cell therapies, and adoptive T cell transfer.

T-cells producing multiple combinations of IFNγ, TNF and IL10 are associated with mild forms of dengue infection

Multifunctional interleukin 10 (IL10)⁺ Th1 cells have been implicated in favorable evolution of many infectious diseases, promoting an efficacious immune response while limiting immunopathology. Here, we investigated the presence of multifunctional CD4⁺ and CD8⁺ T-cells that expressed interferon gamma (IFNγ), IL10 and tumor necrosis factor (TNF), or its combinations during dengue infection. Peripheral blood mononuclear cells (PBMCs) from outpatients with dengue (mild dengue forms) and hospitalized patients (or patients with dengue with warning signs and severe dengue) were cultured in the presence of envelope (ENV) or NS3 peptide libraries of DENV during critical (hospitalization period) and convalescence phases. The production of IFNγ, IL10 and TNF by CD4⁺ and CD8⁺ T-cells was assessed by flow cytometry. Our data show that patients with mild dengue, when compared with patients with dengue with warning signs and severe dengue, presented higher frequencies of multifunctional T-cells like NS3-specific IFNγ/IL10-producing CD4⁺ T-cells in critical phase and NS3- and ENV-specific CD8⁺ T-cells producing IFNγ/IL10. In addition, NS3-specific CD8⁺ T-cells producing high levels of IFNγ/TNF and IFNγ/TNF/IL10 were also observed in the mild dengue group. We observed that multifunctional T-cells produced higher levels of cytokines as measured by intracellular content when compared with single producer T-cells. Importantly, multifunctional CD4⁺ and CD8⁺ T-cells producing IFNγ, TNF and IL10 simultaneously displayed positive correlation with platelet levels, suggesting a protective role of this population. The presence of IL10⁺ Th1 and IL10⁺ Tc1 multifunctional cells was associated with mild dengue presentation, suggesting that these cells play a role in clinical evolution of dengue infection.

Oral typhoid vaccine Ty21a elicits antigen-specific resident memory CD4+ T cells in the human terminal ileum lamina propria and epithelial compartments

Background

Salmonella enterica serovar Typhi (S. Typhi) is a highly invasive bacterium that infects the human intestinal mucosa and causes ~ 11.9–20.6 million infections and ~ 130,000–223,000 deaths annually worldwide. Oral typhoid vaccine Ty21a confers a moderate level of long-lived protection (5–7 years) in the field. New and improved vaccines against enteric pathogens are needed but their development is hindered by a lack of the immunological correlates of protection especially at the site of infection. Tissue resident memory T (T_RM) cells provide immediate adaptive effector immune responsiveness at the infection site. However, the mechanism(s) by which S. Typhi induces T_RM in the intestinal mucosa are unknown. Here, we focus on the induction of S. Typhi-specific CD4+T_RM subsets by Ty21a in the human terminal ileum lamina propria and epithelial compartments.

Methods

Terminal ileum biopsies were obtained from consenting volunteers undergoing routine colonoscopy who were either immunized orally with 4 doses of Ty21a or not. Isolated lamina propria mononuclear cells (LPMC) and intraepithelial lymphocytes (IEL) CD4+T_RM immune responses were determined using either S. Typhi-infected or non-infected autologous EBV-B cell lines as stimulator cells. T-CMI was assessed by the production of 4 cytokines [interferon (IFN)γ, interleukin (IL)-2, IL-17A and tumor necrosis factor (TNF)α] in 36 volunteers (18 vaccinees and 18 controls volunteers).

Results

Although the frequencies of LPMC CD103+ CD4+T_RM were significant decreased, both CD103+ and CD103− CD4+T_RM subsets spontaneously produced significantly higher levels of cytokines (IFNγ and IL-17A) following Ty21a-immunization. Importantly, we observed significant increases in S. Typhi-specific LPMC CD103+ CD4+T_RM (IFNγ and IL-17A) and CD103− CD4+T_RM (IL-2 and IL-17A) responses following Ty21a-immunization. Further, differences in S. Typhi-specific responses between these two CD4+T_RM subsets were observed following multifunctional analysis. In addition, we determined the effect of Ty21a-immunization on IEL and observed significant changes in the frequencies of IEL CD103+ (decrease) and CD103− CD4+T_RM (increase) following immunization. Finally, we observed that IEL CD103− CD4+T_RM, but not CD103+ CD4+T_RM, produced increased cytokines (IFNγ, TNFα and IL-17A) to S. Typhi-specific stimulation following Ty21a-immunization.

Conclusions

Oral Ty21a-immunization elicits distinct compartment specific immune responses in CD4+T_RM (CD103+ and CD103−) subsets. This study provides novel insights in the generation of local vaccine-specific responses.

Trial registration This study was approved by the Institutional Review Board and registered on ClinicalTrials.gov (identifier NCT03970304, Registered 29 May 2019—Retrospectively registered, http://www.ClinicalTrials.gov/NCT03970304)

Use of gene expression studies to investigate the human immunological response to malaria infection

Background

Transcriptional profiling of the human immune response to malaria has been used to identify diagnostic markers, understand the pathogenicity of severe disease and dissect the mechanisms of naturally acquired immunity (NAI). However, interpreting this body of work is difficult given considerable variation in study design, definition of disease, patient selection and methodology employed. This work details a comprehensive review of gene expression profiling (GEP) of the human immune response to malaria to determine how this technology has been applied to date, instances where this has advanced understanding of NAI and the extent of variability in methodology between studies to allow informed comparison of data and interpretation of results.

Methods

Datasets from the gene expression omnibus (GEO) including the search terms; ‘plasmodium’ or ‘malaria’ or ‘sporozoite’ or ‘merozoite’ or ‘gametocyte’ and ‘Homo sapiens’ were identified and publications analysed. Datasets of gene expression changes in relation to malaria vaccines were excluded.

Results

Twenty-three GEO datasets and 25 related publications were included in the final review. All datasets related to Plasmodium falciparum infection, except two that related to Plasmodium vivax infection. The majority of datasets included samples from individuals infected with malaria ‘naturally’ in the field (n = 13, 57%), however some related to controlled human malaria infection (CHMI) studies (n = 6, 26%), or cells stimulated with Plasmodium in vitro (n = 6, 26%). The majority of studies examined gene expression changes relating to the blood stage of the parasite. Significant heterogeneity between datasets was identified in terms of study design, sample type, platform used and method of analysis. Seven datasets specifically investigated transcriptional changes associated with NAI to malaria, with evidence supporting suppression of the innate pro-inflammatory response as an important mechanism for this in the majority of these studies. However, further interpretation of this body of work was limited by heterogeneity between studies and small sample sizes.

Conclusions

GEP in malaria is a potentially powerful tool, but to date studies have been hypothesis generating with small sample sizes and widely varying methodology. As CHMI studies are increasingly performed in endemic settings, there will be growing opportunity to use GEP to understand detailed time-course changes in host response and understand in greater detail the mechanisms of NAI.

Microglial priming of antigen presentation and adaptive stimulation in Alzheimer's disease

The prominent pathological consequences of Alzheimer's disease (AD) are the misfolding and mis-sorting of two cellular proteins, amyloid-β and microtubule-associated protein Tau. The accumulation of toxic phosphorylated Tau inside the neurons induces the increased processing of amyloid-β-associated signaling cascade and vice versa. Neuroinflammation-driven synaptic depletion and cognitive decline are substantiated by the cross talk of activated microglia and astroglia, leading to neuron degeneration. Microglia are the brain-resident immune effectors that prove their diverse functions in maintaining CNS homeostasis via collaboration with astrocytes and T lymphocytes. Age-related senescence and chronic inflammation activate microglia with increased pro-inflammatory markers, oxidative damage and phagocytosis. But the improper processing of misfolded protein via lysosomal pathway destines the spreading of 'seed' constituents to the nearby healthy neurons. Primed microglia process and present self-antigen such as amyloid-β and modified Tau to the infiltrated T lymphocytes through MHC I/II molecules. After an effective conversation with CD4+ T cells, microglial phenotype can be altered from pro-active M1 to neuro-protective M2 type, which corresponds to the tissue remodeling and homeostasis. In this review, we are focusing on the change in functionality of microglia from innate to adaptive immune response in the context of neuroprotection, which may help in the search of novel immune therapy in AD.

Memory CD4 T cell-derived IL-2 synergizes with viral infection to exacerbate lung inflammation

Defining the most penetrating correlates of protective memory T cells is key for designing improved vaccines and T cell therapies. Here, we evaluate how interleukin (IL-2) production by memory CD4 T cells, a widely held indicator of their protective potential, impacts immune responses against murine influenza A virus (IAV). Unexpectedly, we show that IL-2-deficient memory CD4 T cells are more effective on a per cell basis at combating IAV than wild-type memory cells that produce IL-2. Improved outcomes orchestrated by IL-2-deficient cells include reduced weight loss and improved respiratory function that correlate with reduced levels of a broad array of inflammatory factors in the infected lung. Blocking CD70-CD27 signals to reduce CD4 T cell IL-2 production tempers the inflammation induced by wild-type memory CD4 T cells and improves the outcome of IAV infection in vaccinated mice. Finally, we show that IL-2 administration drives rapid and extremely potent lung inflammation involving NK cells, which can synergize with sublethal IAV infection to promote acute death. These results suggest that IL-2 production is not necessarily an indicator of protective CD4 T cells, and that the lung environment is particularly sensitive to IL-2-induced inflammation during viral infection.

Epstein-Barr virus (EBV) reactivation and therapeutic inhibitors

Epstein-Barr virus (EBV) is a ubiquitous human virus which infects almost all humans during their lifetime and following the acute phase, persists for the remainder of the life of the individual. EBV infects B lymphocytes leading to their immortalisation, with persistence of the EBV genome as an episome. In the latent phase, EBV is prevented from reactivating through efficient cytotoxic cellular immunity. EBV reactivates (lytic phase) under conditions of psychological stress with consequent weakening of cellular immunity, and EBV reactivation has been shown to occur in a subset of individuals with each of a variety of cancers, autoimmune diseases, the autoimmune-like disease, chronic fatigue syndrome/myalgic encephalitis and under other circumstances such as being an inpatient in an intensive care unit. Chronic EBV reactivation is an important mechanism in the pathogenesis of many such diseases, yet is rarely tested for in immunocompetent individuals. This review summarises the pathogenesis of EBV infection, EBV reactivation and its role in disease, and methods which may be used to detect it. Known inhibitors of EBV reactivation and replication are discussed, including drugs licensed for treatment of other herpesviruses, licensed or experimental drugs for various other indications, compounds at an early stage of drug development and nutritional constituents such as vitamins and dietary supplements.

High-Parameter Single-Cell Analysis

Thousands of transcripts and proteins confer function and discriminate cell types in the body. Using high-parameter technologies, we can now measure many of these markers at once, and multiple platforms are now capable of analysis on a cell-by-cell basis. Three high-parameter single-cell technologies have particular potential for discovering new biomarkers, revealing disease mechanisms, and increasing our fundamental understanding of cell biology. We review these three platforms (high-parameter flow cytometry, mass cytometry, and a new class of technologies called integrated molecular cytometry platforms) in this article. We describe the underlying hardware and instrumentation, the reagents involved, and the limitations and advantages of each platform. We also highlight the emerging field of high-parameter single-cell data analysis, providing an accessible overview of the data analysis process and choice of tools.

An Animal Model of Acute and Chronic Chagas Disease With the Reticulotropic Y Strain of Trypanosoma cruzi That Depicts the Multifunctionality and Dysfunctionality of T Cells

Chagas disease (ChD), a complex and persistent parasitosis caused by Trypanosoma cruzi, represents a natural model of chronic infection, in which some people exhibit cardiac or digestive complications that can result in death 20–40 years after the initial infection. Nonetheless, due to unknown mechanisms, some T. cruzi-infected individuals remain asymptomatic throughout their lives. Actually, no vaccine is available to prevent ChD, and treatments for chronic ChD patients are controversial. Chronically T. cruzi-infected individuals exhibit a deterioration of T cell function, an exhaustion state characterized by poor cytokine production and increased inhibitory receptor co-expression, suggesting that these changes are potentially related to ChD progression. Moreover, an effective anti-parasitic treatment appears to reverse this state and improve the T cell response. Taking into account these findings, the functionality state of T cells might provide a potential correlate of protection to detect individuals who will or will not develop the severe forms of ChD. Consequently, we investigated the T cell response, analyzed by flow cytometry with two multicolor immunofluorescence panels, to assess cytokines/cytotoxic molecules and the expression of inhibitory receptors, in a murine model of acute (10 and 30 days) and chronic (100 and 260 days) ChD, characterized by parasite persistence for up to 260 days post-infection and moderate inflammation of the colon and liver of T. cruzi-infected mice. Acute ChD induced a high antigen-specific multifunctional T cell response by producing IFN-γ, TNF-α, IL-2, granzyme B, and perforin; and a high frequency of T cells co-expressed 2B4, CD160, CTLA-4, and PD-1. In contrast, chronically infected mice with moderate inflammatory infiltrate in liver tissue exhibited monofunctional antigen-specific cells, high cytotoxic activity (granzyme B and perforin), and elevated levels of inhibitory receptors (predominantly CTLA-4 and PD-1) co-expressed on T cells. Taken together, these data support our previous results showing that similar to humans, the T. cruzi persistence in mice promotes the dysfunctionality of T cells, and these changes might correlate with ChD progression. Thus, these results constitute a model that will facilitate an in-depth search for immune markers and correlates of protection, as well as long-term studies of new immunotherapy strategies for ChD.

Innovative antigen carrier system for the development of tuberculosis vaccines

A major obstacle to tuberculosis (TB)-subunit-vaccine development has been the induction of inadequate levels of protective immunity due to the limited breadth of antigen in vaccine preparations. In this study, immunogenic mycobacterial fusion peptides Ag85B-TB10.4 and Ag85B-TB10.4-Rv2660c were covalently displayed on the surface of self-assembled polyester particles. This study investigated whether polyester particles displaying mycobacterial antigens could provide augmented immunogenicity (i.e., offer an innovative vaccine formulation) when compared with free soluble antigens. Herein, polyester particle-based particulate vaccines were produced in an endotoxin-free Escherichia coli strain and emulsified with the adjuvant dimethyl dioctadecyl ammonium bromide. C57BL/6 mice were used to study the immunogenicity of formulated particulate vaccines. The result of humoral immunity showed the antibodies only interacted with target antigens and not with PhaC and the background proteins of the production host. The analysis of T helper 1 cellular immunity indicated that a relatively strong production of cellular immunity biomarkers, IFN-γ and IL-17A cytokines, was induced by particulate vaccines when compared with the respective soluble controls. This study demonstrated that polyester particles have the potential to perform as a mycobacterial antigen-delivery agent to induce augmented antigen-specific immune responses in contrast to free soluble vaccines.-Chen, S., Sandford, S., Kirman, J. R., Rehm, B. H. A. Innovative antigen carrier system for the development of tuberculosis vaccines.

Loss of T-Cell Multifunctionality and TCR-Vβ Repertoire Against Epstein-Barr Virus Is Associated With Worse Prognosis and Clinical Parameters in HIV+ Patients

Epstein-Barr virus (EBV) is an oncogenic virus associated with the development of aggressive and poor-prognosis B-cell lymphomas in patients infected with human immunodeficiency virus (HIV⁺ patients). The most important risk factors for these malignancies include immune dysfunction, chronic immune activation, and loss of T-cell receptor (TCR) repertoire. The combination of all these factors can favor the reactivation of EBV, malignant cell transformation, and clinical progression toward B-cell lymphomas. The overarching aim of this study was to evaluate the frequency, phenotype, functionality, and distribution of TCR clonotypes for EBV-specific T-cell subpopulations in HIV⁺ patients at different clinical stages and for HIV⁺ patients with B-cell lymphoma, as well as to establish their association with clinical variables of prognostic value. Factors were studied in 56 HIV⁺ patients at different clinical stages and in six HIV+ subjects with diagnosed B-cell lymphoma. We found a significant decrease in all subpopulations of EBV-specific CD4⁺ T cells from HIV⁺ patients at stage 3 and with B-cell lymphoma. EBV-specific effector CD8⁺ T cells, particularly effector memory cells, were also reduced in HIV⁺ patients with B-cell lymphoma. Interestingly, these cells were unable to produce IFN-γ and lacked multifunctionality in HIV+ patients. The TCR-Vβ repertoire, which is key for protection against EBV in healthy individuals, was less diverse in HIV⁺ patients due to a lower frequency of TCR-Vβ2⁺, Vβ4⁺, Vβ7.1⁺, Vβ9⁺, Vβ13.6⁺, Vβ14⁺, Vβ17⁺, Vβ22⁺ CD4⁺, Vβ14⁺, and Vβ17⁺ CD8⁺ T cells. HIV⁺ patients with positive plasma EBV loads (EBV⁺HIV⁺) had a noteworthy decrease in the levels of both TNF-α⁺ and multifunctional TNF-α⁺/IL-2⁺ and TNF-α⁺/IFN-γ⁺ CD8⁺ T cells. Altogether, our findings demonstrate that HIV⁺ patients have significant alterations in the immune response to EBV (poor-quality immunity) that can favor viral reactivation, escalating the risk for developing EBV-associated B-cell lymphomas.

Emergence of CD4+ and CD8+ Polyfunctional T Cell Responses Against Immunodominant Lytic and Latent EBV Antigens in Children With Primary EBV Infection

Long term carriers were shown to generate robust polyfunctional T cell (PFC) responses against lytic and latent antigens of Epstein-Barr virus (EBV). However, the time of emergence of PFC responses against EBV antigens, pattern of immunodominance and difference between CD4+ and CD8+ T cell responses during various stages of EBV infection are not clearly understood. A longitudinal study was performed to assess the development of antigen-specific PFC responses in children diagnosed to have primary symptomatic (infectious mononucleosis [IM]) and asymptomatic (AS) EBV infection. Evaluation of IFN-γ secreting CD8+ T cell responses upon stimulation by HLA class I-specific peptides of EBV lytic and latent proteins by ELISPOT assay followed by assessment of CD4+ and CD8+ PFC responses upon stimulation by a panel of overlapping EBV peptides for co-expression of IFN-γ, TNF-α, IL-2, perforin and CD107a by flow cytometry were performed. Cytotoxicity of T cells against autologous lymphoblastoid cell lines (LCLs) as well as EBV loads in PBMC and plasma were also determined. Both IM and AS patients had elevated PBMC and plasma viral loads which declined steadily during a 12-month period from the time of diagnosis whilst decrease in the magnitude of CD8+ T cell responses toward EBV lytic peptides in contrast to increase toward latent peptides was shown with no significant difference between those of IM and AS patients. Both lytic and latent antigen-specific CD4+ and CD8+ T cells demonstrated polyfunctionality (defined as greater or equal to three functions) concurrent with enhanced cytotoxicity against autologous LCLs and steady decrease in plasma and PBMC viral loads over time. Immunodominant peptides derived from BZLF1, BRLF1, BMLF1 and EBNA3A-C proteins induced the highest proportion of CD8+ as well as CD4+ PFC responses. Diverse functional subtypes of both CD4+ and CD8+ PFCs were shown to emerge at 6–12 months. In conclusion, EBV antigen-specific CD4+ and CD8+ PFC responses emerge during the first year of primary EBV infection, with greatest responses toward immunodominant epitopes in both lytic and latent proteins, correlating to steady decline in PBMC and plasma viral loads.

Altered Peptide Ligands Impact the Diversity of Polyfunctional Phenotypes in T Cell Receptor Gene-Modified T Cells

The use of T cell receptor (TCR) gene-modified T cells in adoptive cell transfer has had promising clinical success, but often, simple preclinical evaluation does not necessarily accurately predict treatment efficacy or safety. Preclinical studies generally evaluate one or a limited number of type 1 cytokines to assess antigen recognition. However, recent studies have implicated other "typed" T cells in effective anti-tumor/viral immunity, and limited functional evaluations may underestimate cross-reactivity. In this study, we use an altered peptide ligand (APL) model and multi-dimensional flow cytometry to evaluate polyfunctionality of TCR gene-modified T cells. Evaluating six cytokines and the lytic marker CD107a on a per cell basis revealed remarkably diverse polyfunctional phenotypes within a single T cell culture and among peripheral blood lymphocyte (PBL) donors. This polyfunctional assessment identified unexpected phenotypes, including cells producing both type 1 and type 2 cytokines, and highlighted interferon γ^neg (IFNγ^neg) antigen-reactive populations overlooked in our previous studies. Additionally, APLs skewed functional phenotypes to be less polyfunctional, which was not necessarily related to changes in TCR-peptide-major histocompatibility complex (pMHC) affinity. A better understanding of gene-modified T cell functional diversity may help identify optimal therapeutic phenotypes, predict clinical responses, anticipate off-target recognition, and improve the design and delivery of TCR gene-modified T cells.

A Chlamydia-Specific TCR-Transgenic Mouse Demonstrates Th1 Polyfunctionality with Enhanced Effector Function

Chlamydia is responsible for millions of new infections annually, and current efforts focus on understanding cellular immunity for targeted vaccine development. The Chlamydia-specific CD4 T cell response is characterized by the production of IFN-γ, and polyfunctional Th1 responses are associated with enhanced protection. A major limitation in studying these responses is the paucity of tools available for detection, quantification, and characterization of polyfunctional Ag-specific T cells. We addressed this problem by developing a TCR-transgenic (Tg) mouse with CD4 T cells that respond to a common Ag in Chlamydia muridarum and Chlamydia trachomatis Using an adoptive-transfer approach, we show that naive Tg CD4 T cells become activated, proliferate, migrate to the infected tissue, and acquire a polyfunctional Th1 phenotype in infected mice. Polyfunctional Tg Th1 effectors demonstrated enhanced IFN-γ production compared with polyclonal cells, protected immune-deficient mice against lethality, mediated bacterial clearance, and orchestrated an anamnestic response. Adoptive transfer of Chlamydia-specific CD4 TCR-Tg T cells with polyfunctional capacity offers a powerful approach for analysis of protective effector and memory responses against chlamydial infection and demonstrates that an effective monoclonal CD4 T cell response may successfully guide subunit vaccination strategies.