Effector and central memory T helper 2 cells respond differently to peptide immunotherapy

Penicilazaphilone C alleviates allergic airway inflammation and improves the immune microenvironment by hindering the NLRP3 inflammasome

AIMS

Penicilazaphilone C (PAC) is hypothesized to potentially serve as a therapeutic treatment for allergic airway inflammation by inhibiting the NLRP3 inflammasome and reducing oxidative stress.

METHODS

An allergic asthma model was induced in female BALB/c mice of the OVA, OVA+PAC, OVA+PAC+LPS, and OVA+Dex groups by sensitizing and subsequently challenging them with OVA. The OVA+PAC and Normal+PAC groups were treated with PAC, while the OVA+PAC+LPS group also received LPS. The OVA+Dex group was given dexamethasone (Dex). Samples of serum, bronchoalveolar lavage fluid (BALF), and lung tissue were collected for histological and cytological analysis.

RESULTS

Allergic mice treated with PAC or Dex showed inhibited inflammation and mucus production in the lungs. There was a decrease in the number of inflammatory cells in the BALF, lower levels of inflammatory cytokines in the serum and BALF, and a reduction in the protein expression of NLRP3, ASC, cleaved caspase-1, IL-1β, activated gasdermin D, MPO, Ly6G, and ICAM-1. Additionally, oxidative stress was reduced, as shown by a decrease in MDA and DCF, but an increase in SOD and GSH. Treatment with PAC also resulted in a decrease in pulmonary memory CD4+ T cells and an increase in regulatory T cells. However, the positive effects seen in the PAC-treated mice were reversed when the NLRP3 inflammasome was activated by LPS, almost returning to the levels of the Sham-treated mice.

SIGNIFICANCE

PAC acts in a similar way to anti-allergic inflammation as Dex, suggesting it may be a viable therapeutic option for managing allergic asthma inflammation.

Mechanisms of allergen immunotherapy supporting its disease-modifying effect

Allergen immunotherapy (AIT) is considered the only disease-modifying treatment available at present for allergic disorders. Its main benefits include improvement of symptoms, decreased need for pharmacotherapy, prevention of new sensitizations and sustained effect after AIT completion. The key pillars of AIT-induced tolerance include a shift from Th2 to Th1 response, an increase of regulatory T and B cells, pro-inflammatory effector cell downregulation and IgE suppression, in addition to IgG4, IgA and IgD induction. AIT may also induce trained immunity, characterized by a durable decrease in group 2 of innate lymphoid cells (ILCs) and increased ILC1 and ILC3s. Understanding the immune mechanisms of AIT is essential for validating biomarkers for the prediction of AIT response and for achieving AIT success.

An exhausted phenotype of TH 2 cells is primed by allergen exposure, but not reinforced by allergen-specific immunotherapy

BACKGROUND

Studies show that proallergic T_H 2 cells decrease after successful allergen-specific immunotherapy (AIT). It is likely that iatrogenic administration of allergens drives these cells to exhaustion due to chronic T-cell receptor stimulation. This study aimed to investigate the exhaustion of T cells in connection with allergen exposure during AIT in mice and two independent patient cohorts.

METHODS

OVA-sensitized C57BL/6J mice were challenged and treated with OVA, and the development of exhaustion in local and systemic T_H 2 cells was analyzed. In patients, the expression of exhaustion-associated surface markers on T_H 2 cells was evaluated using flow cytometry in a cross-sectional grass pollen allergy cohort with and without AIT. The treatment effect was further studied in PBMC collected from a prospective long-term AIT cohort.

RESULTS

The exhaustion-associated surface markers CTLA-4 and PD-1 were significantly upregulated on T_H 2 cells upon OVA aerosol exposure in OVA-allergic compared to non-allergic mice. CTLA-4 and PD-1 decreased after AIT, in particular on the surface of local lung T_H 2 cells. Similarly, CTLA-4 and PD-1 expression was enhanced on T_H 2 cells from patients with allergic rhinitis with an even stronger effect in those with concomitant asthma. Using an unbiased Louvain clustering analysis, we discovered a late-differentiated T_H 2 population expressing both markers that decreased during up-dosing but persisted long term during the maintenance phase.

CONCLUSIONS

This study shows that allergen exposure promotes CTLA-4 and PD-1 expression on T_H 2 cells and that the dynamic change in frequencies of exhausted T_H 2 cells exhibits a differential pattern during the up-dosing versus the maintenance phases of AIT.

Early memory differentiation and cell death resistance in T cells predicts melanoma response to sequential anti-CTLA4 and anti-PD1 immunotherapy

Immune checkpoint blockers (ICBs)-based immunotherapy has revolutionised oncology. However, the benefits of ICBs are limited to only a subset of patients. Herein, the biomarkers-driven application of ICBs promises to increase their efficacy. Such biomarkers include lymphocytic IFNγ-signalling and/or cytolytic activity (granzymes and perforin-1) footprints, whose levels in pre-treatment tumours can predict favourable patient survival following ICB-treatment. However, it is not clear whether such biomarkers have the same value in predicting survival of patients receiving first-line anti-CTLA4 ICB-therapy, and subsequently anti-PD1 ICB-therapy (i.e., sequential ICB-immunotherapy regimen). To address this, we applied highly integrated systems/computational immunology approaches to existing melanoma bulk-tumour transcriptomic and single-cell (sc)RNAseq data originating from immuno-oncology clinical studies applying ICB-treatment. Interestingly, we observed that CD8⁺/CD4⁺T cell-associated IFNγ-signalling or cytolytic activity signatures fail to predict tumour response in patients treated with anti-CTLA4 ICB-therapy as a first-line and anti-PD1 ICB-therapy in the second-line setting. On the contrary, signatures associated with early memory CD8⁺/CD4⁺T cells (integrating TCF1-driven stem-like transcriptional programme), capable of resisting cell death/apoptosis, better predicted objective response rates to ICB-immunotherapy, and favourable survival in the setting of sequential ICB-immunotherapy. These observations suggest that sequencing of ICB-therapy might have a specific impact on the T cell-repertoire and may influence the predictive value of tumoural immune biomarkers.

Lipopolysaccharide-Activated Bone Marrow-Derived Dendritic Cells Suppress Allergic Airway Inflammation by Ameliorating the Immune Microenvironment

Background

Previous studies have shown that lipopolysaccharide (LPS)-activated bone marrow-derived dendritic cells (DClps) might induce tolerance in autoimmune and cancer models in vivo, whereas it remains unclear whether DClps could play a role in allergic disease model. Herein, we aimed to elucidate the potential effects of DClps on OVA-sensitized/challenged airway inflammation in a mouse model, which may help facilitate the application of specific tolerogenic dendritic cells (tolDC) in allergic asthma in the future.

Methods

The phenotype and function of immature DC (DCia), DClps or IL-10-activated-DC (DC10) were determined. OVA-sensitized/challenged mice were treated with OVA-pulsed DCia or DClps or DC10. We assessed the changes of histopathology, serum total IgE level, pulmonary signal transducers and activators of transcription (STAT), pulmonary regulatory T cells (Tregs), and airway recall responses to OVA rechallenge, including proliferation and cytokine secretory function of pulmonary memory CD4⁺ T cells in the treated mice.

Results

DClps exhibited low levels of CD80 and MHCII and increased levels of anti-inflammatory cytokines such as IL-10 and TGF-β. Additionally, DClps treatment dramatically diminished infiltration of inflammatory cells, eosinophilia, serum IgE and STAT6 phosphorylation level, increased the number of pulmonary Tregs. In addition, DClps treatment decreased the proliferation of pulmonary memory CD4⁺ T cells, which further rendered the downregulation of Th2 cytokines in vitro.

Conclusion

LPS stimulation may lead to a tolerogenic phenotype on DC, and thereby alleviated the Th2 immune response of asthmatic mice, possibly by secreting anti-inflammatory cytokines, inhibiting pulmonary memory CD4⁺ T cells, downregulating pulmonary STAT6 phosphorylation level and increasing pulmonary Tregs.

Tolerance induction in memory CD4 T cells is partial and reversible

Memory T cells respond rapidly in part because they are less reliant on a heightened levels of costimulatory molecules. This enables rapid control of secondary infecting pathogens but presents challenges to efforts to control or silence memory CD4 T cells, for example in antigen‐specific tolerance strategies for autoimmunity. We have examined the transcriptional and functional consequences of reactivating memory CD4 T cells in the absence of an adjuvant. We find that memory CD4 T cells generated by infection or immunisation survive secondary activation with antigen delivered without adjuvant, regardless of their location in secondary lymphoid organs or peripheral tissues. These cells were, however, functionally altered following a tertiary immunisation with antigen and adjuvant, proliferating poorly but maintaining their ability to produce inflammatory cytokines. Transcriptional and cell cycle analysis of these memory CD4 T cells suggests they are unable to commit fully to cell division potentially because of low expression of DNA repair enzymes. In contrast, these memory CD4 T cells could proliferate following tertiary reactivation by viral re‐infection. These data indicate that antigen‐specific tolerogenic strategies must examine multiple parameters of Tcell function, and provide insight into the molecular mechanisms that may lead to deletional tolerance of memory CD4 T cells.

Go With Your Gut: The Shaping of T-Cell Response by Gut Microbiota in Allergic Asthma

Novel methods in immunological research and microbiome evaluation have dramatically changed several paradigms associated with the pathogenesis of allergic asthma (AAS). Ovalbumin and house dust mite-induced AAS in germ-free or specific pathogen-free mice are the two leading experimental platforms that significantly contribute to elucidate the relationship between AAS and gut microbiota. Beyond the exacerbation of T helper (Th) 2 responses, a complex network of immunological interaction driven by gut microbiota could modulate the final effector phase. Regulatory T cells are abundant in gastrointestinal mucosa and have been shown to be pivotal in AAS. The gut microbiota could also influence the activity of other T cell subsets such as Th9, Th17, and populations of effector/memory T lymphocytes. Furthermore, gut microbiota metabolites drive the hematopoietic pattern of dendritic cells and ameliorate lung Th2 immunity in AAS models. The administration of probiotics has shown conflicting results in AAS, and limited evidence is available on the immunological pathways beyond their activity. Moreover, the impact of early-life gut dysbiosis on AAS is well-known both experimentally and clinically, but discrepancies are observed between preclinical and clinical settings. Herein, our aim is to elucidate the most relevant preclinical and clinical scenarios to enlighten the potential role of the gut microbiota in modulating T lymphocytes activity in AAS.

Modulation of CRTh2 expression on allergen-specific T cells following peptide immunotherapy

Background

Allergen immunotherapy using synthetic peptide T‐cell epitopes (Cat‐PAD) from the major cat allergen Fel d 1 has been shown, in allergen exposure studies, to significantly reduce symptoms of allergic rhinoconjunctivitis in cat‐allergic subjects. However, the immunological mechanisms underlying clinical benefit remain only partially understood. Since previous studies of whole allergen immunotherapy demonstrated a reduction in the frequency of allergen‐specific (MHC II tetramer⁺) CD4⁺ T cells expressing the chemokine receptor CRTh2, we assessed the impact of Cat‐PAD on the frequency and functional phenotype of Fel d 1‐specific CD4⁺ T cells.

Methods

Using before and after treatment samples from subjects enrolled in a randomized, double‐blind, placebo‐controlled trial of Cat‐PAD, we employed Fel d 1 MHC II tetramers and flow cytometry to analyze the expression of chemokine receptors CCR3, CCR4, CCR5, CXCR3, and CRTh2, together with markers of memory phenotype (CD27 and CCR7) on Fel d 1‐specific CD4⁺ T cells.

Results

No statistically significant change in the frequency of Fel d 1‐specific CD4⁺ T cells, nor in their expression of chemokine receptors or memory phenotype, was observed. However, a significant reduction in cell surface expression of CRTh2 was observed between the placebo and active groups (P = 0.047).

Conclusions

Peptide immunotherapy with Cat‐PAD does not significantly alter the frequency or phenotype of Fel d 1‐CD4⁺ T cells, but may decrease their expression of CRTh2.

Regulation of type 2 innate lymphoid cell-dependent airway hyperreactivity by butyrate

BACKGROUND

Allergic asthma is characterized by airway hyperreactivity (AHR) and inflammation driven by aberrant T_H2 responses. Type 2 innate lymphoid cells (ILC2s) are a critical source of the T_H2 cytokines IL-5 and IL-13, which promote acute asthma exacerbation. Short-chain fatty acids (SCFAs) have been shown to attenuate T cell-mediated allergic airway inflammation. However, their role in regulation of ILC2-driven AHR and lung inflammation remains unknown.

OBJECTIVE

We investigated the immunomodulatory role of SCFAs in regulation of ILC2-induced AHR and airway inflammation and delineated the mechanism involved.

METHODS

We assessed the role of SCFAs in regulating survival, proliferation, and cytokine production in lung sorted ILC2s. The SCFA butyrate was administered through drinking water or intranasally in BALB/c mice to evaluate its role in the ILC2-driven inflammatory response in IL-33 and Alternaria alternata models of allergic inflammation. We further confirmed our findings in human ILC2s.

RESULTS

We show that butyrate, but not acetate or propionate, inhibited IL-13 and IL-5 production by murine ILC2s. Systemic and local administration of butyrate significantly ameliorated ILC2-driven AHR and airway inflammation. We further demonstrate that butyrate inhibited ILC2 proliferation and GATA3 expression but did not induce cell apoptosis, likely through histone deacetylase (HDAC) inhibition, because trichostatin A, a pan-HDAC inhibitor, exerted similar effects on ILC2s. Importantly, cotreatment with trichostatin A and butyrate did not result in an additive effect. Finally, we show that butyrate reduces cytokine production in human ILC2s.

CONCLUSION

Our findings identify butyrate as a critical regulator of ILC2 proliferation and function through its HDAC inhibitory activity and can serve as a potential therapeutic target for asthma.

New Insight into the Pathogenesis of Erythema Nodosum Leprosum: The Role of Activated Memory T-Cells

Memory T-cells, particularly, effector memory T cells are implicated in the pathogenesis of inflammatory diseases and may contribute to tissue injury and disease progression. Although erythema nodosum leprosum (ENL) is an inflammatory complication of leprosy, the role of memory T cell subsets has never been studied in this patient group. The aim of this study was at investigate the kinetics of memory T cell subsets in patients with ENL before and after prednisolone treatment. A case–control study design was used to recruit 35 untreated patients with ENL and 25 non-reactional lepromatous leprosy (LL) patient controls at ALERT Hospital, Ethiopia. Venous blood samples were obtained before, during, and after treatment from each patient. Peripheral blood mononuclear cells (PBMCs) were isolated and used for immunophenotyping of T cell activation and memory T-cell subsets by flow cytometry. The kinetics of these immune cells in patients with ENL before and after treatment were compared with LL patient controls as well as within ENL cases at different time points. The median percentage of CD3⁺, CD4⁺, and CD8⁺ T-cells expressing activated T-cells were significantly higher in the PBMCs from patients with ENL than from LL patient controls before treatment. The median percentage of central and activated memory T-cells was significantly increased in patients with ENL compared to LL patient controls before treatment. Interestingly, patients with ENL had a lower percentage of naïve T cells (27.7%) compared to LL patient controls (59.5%) (P < 0.0001) before treatment. However, after prednisolone treatment, patients with ENL had a higher median percentage of naïve T-cells (43.0%) than LL controls (33.0%) (P < 0.001). The median percentage of activated T-cells (effector memory and effector T-cells) was significantly increased in patients with ENL (59.2%) before treatment compared to after treatment with prednisolone (33.9%) (P < 0.005). This is the first work which has shown T-cell activation and the different subsets of memory T cells in untreated patients with ENL. Consequently, this study delineates the role of T-cell activation in the pathogenesis of ENL reaction and challenges the long-standing dogma of immune complex as a sole etiology of ENL reaction.

Immunomodulatory Effects of Adjuvants CPG, MPLA, and BCG on the Derp2-Induced Acute Asthma at Early Life in an Animal Model of BALB/c Mice

The Th1- and Treg cell-related immune responses play key roles in the modulation of Th2 cell-related allergic disorders. The aim was to evaluate the effects of CPG, MPLA, and BCG on the number of Th1-, Th2-, and Treg cell-related parameters in an animal model of asthma. BALB/c mice were divided into five groups and immunized subcutaneously (SC) on days 1, 15, and 22 with allergen Derp2. Three groups of mice were pretreated SC on days 0, 14, and 21 with CPG, CPG + MPLA, or CPG + BCG. All mice were then challenged intranasally with Derp2 on days 28-37. Blood samples were collected from the retro-orbital sinus, on days 0, 23, and 40. The serum levels of IL-4, IFN-γ, IgE, and IgG2a were measured using ELISA technique. The blood number of Th1 and Treg cells was determined using flow cytometry. At the sensitization phase, the number of Th1 and the serum levels of IFN-γ and IgG2a were significantly increased in the Derp2-sensitized group pretreated with CPG plus MPLA, and the number of Treg cells was significantly elevated in Derp2-sensitized mice pretreated with CPG or CPG plus MPLA as compared with that in Derp2-sensitized control mice. At the challenge phase, the number of Th1 was significantly elevated in Derp2-sensitized mice pretreated with CPG plus MPLA, CPG plus BCG, or CPG; the count of Treg cells was significantly increased in Derp2-sensitized mice pretreated with CPG plus BCG group; and the levels of IFN-γ and IgG2a were significantly enhanced in the Derp2-sensitized group pretreated with CPG plus MPLA in comparison with those in Derp2-sensitized control mice. The scores of inflammation and mucus secretion in the lung were significantly decreased in the Derp2-sensitized group pretreated with CPG, BCG, and CPG plus MPLA in comparison with those in the Derp2-sensitized control group. These results showed that BCG, MPLA, and CPG modulate Th1-, Th2-, and Treg-related parameters and ameliorate lung inflammatory parameters in a mouse model of asthma.

Development and Function of Protective and Pathologic Memory CD4 T Cells

Immunological memory is one of the defining features of the adaptive immune system. As key orchestrators and mediators of immunity, CD4 T cells are central to the vast majority of adaptive immune responses. Generated following an immune response, memory CD4 T cells retain pertinent information about their activation environment enabling them to make rapid effector responses upon reactivation. These responses can either benefit the host by hastening the control of pathogens or cause damaging immunopathology. Here, we will discuss the diversity of the memory CD4 T cell pool, the signals that influence the transition of activated T cells into that pool, and highlight how activation requirements differ between naïve and memory CD4 T cells. A greater understanding of these factors has the potential to aid the design of more effective vaccines and to improve regulation of pathologic CD4 T cells, such as in the context of autoimmunity and allergy.

Antigen-based immunotherapy (AIT) for autoimmune and allergic disease

Autoimmune and allergic diseases are major causes of morbidity. Antigen-based immunotherapy (AIT) is immunologically the most satisfying means of specifically targeting only those T cells driving disease, thereby inducing antigen-specific immune tolerance, with the lowest adverse risk profile. AIT is highly effective in rodent models of T cell-driven inflammation and is now in clinical trials. The range of approaches to applying AIT in the clinic prevents a consensus on the molecular basis for this form of tolerance. In particular, there has been a paucity of information on how pre-activated effector and memory T cells respond to AIT. New, advanced murine models of AIT are beginning to deliver such information at the cellular, biochemical, transcriptional and epigenetic levels.

Monocyte:T-cell interaction regulates human T-cell activation through a CD28/CD46 crosstalk

T cell activation requires engagement of the T cell receptor and of at least one costimulatory molecule. The key role of CD28 in inducing T cell activation has been reported several decades ago and the molecular mechanisms involved well described. The complement regulator CD46 also acts as a costimulatory molecule for T cells but, in contrast to CD28, has the ability to drive T cell differentiation from producing some IFNγ to secreting some potent anti-inflammatory IL-10, acquiring a so-called Type I regulatory phenotype (Tr1). Proteolytic cleavage of CD46 occurs upon costimulation and is important for T cell activation and IL-10 production. The observation that CD46 cleavage was reduced when PBMC were costimulated compared to purified naive T cells led us to hypothesize that interactions between different cell types within the PBMC were able to modulate the CD46 pathway. We show that CD46 downregulation is also reduced when CD4⁺ T cells are co-cultured with autologous monocytes. Indeed, monocyte:T cell co-cultures impaired CD46–mediated T cell differentiation and coactivation, by reducing downregulation of surface CD46, lowering induction of the early activation marker CD69, as well as reducing the levels of IL-10 secretion. Blocking of CD86 could partly restore CD69 expression and cytokine secretion, demonstrating that the CD28-CD86 pathway regulates CD46 activation. Direct concomitant ligation of CD28 and CD46 on CD4⁺ T cells also modulated CD46 expression and regulated cytokine production. These data identify a crosstalk between two main costimulatory pathways and provide novel insights into the regulation of human T cell activation.

Jug r 2-reactive CD4(+) T cells have a dominant immune role in walnut allergy

Background

Allergic reactions to walnut can be life threatening. While IgE epitopes of walnut have been studied, CD4⁺ T-cell specific epitopes for walnut remain uncharacterized. Particularly, the relationship of both phenotype and frequency of walnut specific T-cells to the disease have not been examined.

Objectives

We sought to provide a thorough phenotypic analysis for walnut reactive T-cells in allergic and non-allergic subjects. Particularly, the relationship of phenotypes and frequencies of walnut specific T-cells with the disease.

Methods

CD154 up-regulation assay was used to examine CD4⁺ T-cell reactivity towards walnut allergens.Jug r 1, Jug r 2 and Jug r 3. Tetramer-Guided epitope mapping approach was utilized to identify HLA-restricted CD4⁺ T-cells epitopes in Jug r 2. Direct ex vivo staining with peptide-major histocompatibility complex class II (pMHC-II) tetramers enabled the comparison of frequency and phenotype of Jug r 2-specific CD4⁺ T-cells between allergic and non-allergic subjects. Jug r 2-specific T-cell-clones were also generated and mRNA transcription factor levels were assessed by RT qPCR. Intracellular cytokine staining (ICS) assays were performed for further phenotypical analyses.

Results

Jug r 2 was identified as the major allergen that elicited CD4⁺ T-cell responses. Multiple Jug r 2 T-cell epitopes were identified. The majority of these T-cells in allergic subjects have a CCR4⁺ T_CM (central memory) phenotype. A subset of these T-cells express CCR4⁺CCR6⁺ irrespectively of the asthmatic status of the allergic subjects. ICS confirmed these T_H2, T_H2/T_H17 and T_H17-like heterogenic profiles. Jug r 2-specific T-cell-clones from allergic subjects mainly expressed GATA3; nonetheless, a portion of T-cell clones expressed either GATA3 and RORC, or RORC, confirming the presence of T_H2, T_H2/T_H17 and T_H17 cells.

Conclusions

Jug r 2 specific responses dominate walnut T-cell responses in subjects with walnut allergy. Jug r 2 central memory CD4⁺ cells and terminal effector T-cells were detected in peripheral blood with the central memory phenotype as the most prevalent phenotype. In addition to conventional T_H2-cells, T_H2/T_H17 and T_H17 cells were also detected in non-asthmatic and asthmatic subjects with walnut allergy. Understanding this T-cell heterogeneity may render better understanding of the disease manifestation.

HLA-A02:01-restricted epitopes identified from the herpes simplex virus tegument protein VP11/12 preferentially recall polyfunctional effector memory CD8+ T cells from seropositive asymptomatic individuals and protect humanized HLA-A*02:01 transgenic mice against ocular herpes

The HSV type 1 tegument virion phosphoprotein (VP) 11/12 (VP11/12) is a major Ag targeted by CD8(+) T cells from HSV-seropositive individuals. However, whether and which VP11/12 epitope-specific CD8(+) T cells play a role in the "natural" protection seen in seropositive healthy asymptomatic (ASYMP) individuals (who have never had clinical herpes disease) remain to be determined. In this study, we used multiple prediction computer-assisted algorithms to identify 10 potential HLA-A*02:01-restricted CD8(+) T cell epitopes from the 718-aa sequence of VP11/12. Three of 10 epitopes exhibited high-to-moderate binding affinity to HLA-A*02:01 molecules. In 10 sequentially studied HLA-A*02:01-positive and HSV-1-seropositive ASYMP individuals, the most frequent, robust, and polyfunctional effector CD8(+) T cell responses, as assessed by a combination of tetramer frequency, granzyme B, granzyme K, perforin, CD107(a/b) cytotoxic degranulation, IFN-γ, and multiplex cytokines assays, were predominantly directed against three epitopes: VP11/1266-74, VP11/12220-228, and VP11/12702-710. Interestingly, ASYMP individuals had a significantly higher proportion of CD45RA(low)CCR7(low)CD44(high)CD62L(low)CD27(low)CD28(low)CD8(+) effector memory CD8(+) T cells (TEMs) specific to the three epitopes, compared with symptomatic individuals (with a history of numerous episodes of recurrent ocular herpetic disease). Moreover, immunization of HLA-A*02:01 transgenic mice with the three ASYMP CD8(+) TEM cell epitopes induced robust and polyfunctional epitope-specific CD8(+) TEM cells that were associated with a strong protective immunity against ocular herpes infection and disease. Our findings outline phenotypic and functional features of protective HSV-specific CD8(+) T cells that should guide the development of an effective T cell-based herpes vaccine.

Epigenetic modification of the PD-1 (Pdcd1) promoter in effector CD4(+) T cells tolerized by peptide immunotherapy

Clinically effective antigen-based immunotherapy must silence antigen-experienced effector T cells (Teff) driving ongoing immune pathology. Using CD4⁺ autoimmune Teff cells, we demonstrate that peptide immunotherapy (PIT) is strictly dependent upon sustained T cell expression of the co-inhibitory molecule PD-1. We found high levels of 5-hydroxymethylcytosine (5hmC) at the PD-1 (Pdcd1) promoter of non-tolerant T cells. 5hmC was lost in response to PIT, with DNA hypomethylation of the promoter. We identified dynamic changes in expression of the genes encoding the Ten-Eleven-Translocation (TET) proteins that are associated with the oxidative conversion 5-methylcytosine and 5hmC, during cytosine demethylation. We describe a model whereby promoter demethylation requires the co-incident expression of permissive histone modifications at the Pdcd1 promoter together with TET availability. This combination was only seen in tolerant Teff cells following PIT, but not in Teff that transiently express PD-1. Epigenetic changes at the Pdcd1 locus therefore determine the tolerizing potential of TCR-ligation.

DOI:http://dx.doi.org/10.7554/eLife.03416.001

The immune system protects the body from dangerous microbes and removes damaged cells. However, in some cases, the immune system can malfunction and attack healthy tissues, which can lead to type-1 diabetes, multiple sclerosis, and other autoimmune diseases. Many of the current treatments for these disorders suppress the immune system, which can make the individuals more susceptible to infections.

It may be possible to treat autoimmune diseases using small pieces of protein—called peptides—that are based on proteins found on the cells that the immune system attacks by mistake. This strategy would target the specific immune cells that are malfunctioning, but allow the rest of the immune system to continue to work as normal. Peptide-based therapies for autoimmune diseases are currently being tested in clinical trials, and although the results look promising, it is not known precisely how they work.

McPherson et al. used mice that develop a disease similar to multiple sclerosis because some of their immune cells, known as effector T cells, attack a protein found in the mouse brain called MBP. The mice were treated with a peptide based on part of MBP, which prevented them from developing the autoimmune disease. The success of the peptide therapy depended on the T cells producing large amounts of a protein called PD-1. This protein stops the T-cells from activating immune responses when they detect the MBP protein.

The gene that makes PD-1 can have a methyl-tag—a chemical modification to DNA—which alters how much PD-1 is made in the T cells. When the gene has this methyl-tag, it can only be switched on for a short time to make a small amount of PD-1, which helps to control the immune responses activated by the T cell. However, when the methyl-tag was removed as a result of the peptide therapy the gene could be switched on for much longer, so that much more PD-1 was produced.

This work helps us to understand how peptide therapy works and should improve the chances of using this therapy to successfully treat patients with autoimmune diseases.

DOI:http://dx.doi.org/10.7554/eLife.03416.002

New treatments for allergen immunotherapy

Allergen-specific immunotherapy (SIT) represents the only curative and specific way for the treatment of allergic diseases, which have reached a pandemic dimension in industrial countries affecting up to 20-30% of the population. Although applied for 100 years to cure allergy, SIT still faces several problems related to side effects and limited efficacy. Currently, allergen-SIT is performed with vaccines based on allergen extracts that can cause severe, often life threatening, anaphylactic reactions as well as new IgE sensitization to other allergens present in the extract. Low patient adherence and high costs due to long duration (3 to 5 years) of treatment have been commonly reported. Several strategies have been developed to tackle these issues and it became possible to produce recombinant allergen-SIT vaccines with reduced allergenic activity.