In Silico Design of a New Epitope-Based Vaccine against Grass Group 1 Allergens

Allergic diseases are a global public health problem that affects up to 30% of the population in industrialized societies. More than 40% of allergic patients suffer from grass pollen allergy. Grass pollen allergens of group 1 and group 5 are the major allergens, since they induce allergic reactions in patients at high rates. In this study, we used immunoinformatic approaches to design an effective epitope-based vaccine against the grass group 1 allergens. After the alignment of all known pollen T-cell and B-cell epitopes from pollen allergens available in the public databases, the epitope GTKSEVEDVIPEGWKADTSY was identified as the most suitable for further analyses. The target sequence was subjected to immunoinformatics analyses to predict antigenic T-cell and B-cell epitopes. Population coverage analysis was performed for CD8+ and CD4+ T-cell epitopes. The selected T-cell epitopes (VEDVIPEGW and TKSEVEDVIPEGWKA) covered 78.87% and 98.20% of the global population and 84.57% and 99.86% of the population of Europe. Selected CD8+, CD4+ T-cell and B-cell epitopes have been validated by molecular docking analysis. CD8+ and CD4+ T-cell epitopes showed a very strong binding affinity to major histocompatibility complex (MHC) class I (MHC I) molecules and MHC class II (MHC II) molecules with global energy scores of -72.1 kcal/mol and -89.59 kcal/mol, respectively. The human IgE-Fc (PDB ID 4J4P) showed a lower affinity with B-cell epitope (ΔG = -34.4 kcal/mol), while the Phl p 2-specific human IgE Fab (PDB ID 2VXQ) had the lowest binding with the B-cell epitope (ΔG = -29.9 kcal/mol). Our immunoinformatics results demonstrated that the peptide GTKSEVEDVIPEGWKADTSY could stimulate the immune system and we performed ex vivo tests showed that the investigated epitope activates T cells isolated from patients with grass pollen allergy, but it is not recognized by IgE antibodies specific for grass pollen allergens. This confirms the importance of such studies to establish universal epitopes to serve as a basis for developing an effective vaccine against a particular group of allergens. Further in vivo studies are needed to validate the effectiveness of such a vaccine against grass pollen allergens.

CD8 T-cell subsets: heterogeneity, functions, and therapeutic potential

CD8 T cells play crucial roles in immune surveillance and defense against infections and cancer. After encountering antigenic stimulation, naïve CD8 T cells differentiate and acquire effector functions, enabling them to eliminate infected or malignant cells. Traditionally, cytotoxic T cells, characterized by their ability to produce effector cytokines and release cytotoxic granules to directly kill target cells, have been recognized as the constituents of the predominant effector T-cell subset. However, emerging evidence suggests distinct subsets of effector CD8 T cells that each exhibit unique effector functions and therapeutic potential. This review highlights recent advancements in our understanding of CD8 T-cell subsets and the contributions of these cells to various disease pathologies. Understanding the diverse roles and functions of effector CD8 T-cell subsets is crucial to discern the complex dynamics of immune responses in different disease settings. Furthermore, the development of immunotherapeutic approaches that specifically target and regulate the function of distinct CD8 T-cell subsets holds great promise for precision medicine.

Clinical impact and immunological alterations in asthmatic patients allergic to grass pollen subjected to high urban pollution in Madrid

BACKGROUND

The prevalence of asthma has increased in recent decades. Among the reasons for this increase is environmental pollution. Pollutants cause bronchial inflammation and introduce modifications in the pollen, making it more allergenic.

OBJECTIVE

Assess symptoms and medication requirements of asthmatic patients with grass allergies in Madrid (high urban pollution) and Ciudad Real (low pollution), and simultaneously evaluate the in vitro effects that pollen collected in both areas has on the immune cells of patients.

METHODS

During two pollen seasons, patients from both cities were included. The patients recorded their symptoms and the asthma medication they took daily. In both cities, pollen data, pollutants and meteorological variables were evaluated. The response to different cell populations from patients in both areas were analysed after "in vitro" stimulation with pollen from both cities.

RESULTS

The symptoms and medication use of the patients in Madrid was 29.94% higher. The NO₂ concentration in Madrid was triple that of Ciudad Real (33.4 vs. 9.1 µg/m³ of air). All other pollutants had very similar concentrations during the study period. Pollen from the high pollution area caused a significant enhancement of T-CD8+ and NK cells proliferation compared with pollen of low pollution area, independently of the patient's origin.

CONCLUSION

Asthmatic patients from Madrid have a worse clinical evolution than those from Ciudad Real because of higher levels of urban pollution, and this could be driven by the higher capacity of pollen of Madrid to activate T-CD8+ and NK cells.

Single-cell analysis pinpoints distinct populations of cytotoxic CD4+ T cells and an IL-10+CD109+ TH2 cell population in nasal polyps

Chronic rhinosinusitis with nasal polyps (CRSwNP) is characterized by a chronic inflammatory process often associated with comorbid asthma. In this study, we analyzed the transcriptomes of single T helper (T_H) cells from nasal polyps of patients with CRSwNP and validated these findings using multiparameter flow cytometry. Polyp tissue contained suppressive T regulatory (T_reg) cells, T_H2 cells, type 2 innate lymphoid cells, and three transcriptionally distinct subsets of cytotoxic CD4⁺ T cells (CD4⁺ CTL). GATA3 expression was a feature of polyp T_reg cells, whereas T_H2 cells highly expressed TCN1, CD200R, and HPGDS and were enriched for genes involved in lipid metabolism. Only a portion of polyp T_H2 cells expressed the prostaglandin D2 receptor CRTH2, whereas a subpopulation of CD109⁺CRTH2^- T_H2 cells expressed mRNA for common inhibitor receptors including LAG3 and TIM3 and produced IL-10. Together, we resolved the complexity of T_H cells in patients with CRSwNP, identifying several distinct clusters of CD4⁺ CTL and a population of CD109⁺CRTH2^- T_H2 cells with putative regulatory potential.

Low expression of a Ddm7/Ldm7-hybrid mutant (D/Ldm7) in the novel haplotype H-2nc identified in atopic dermatitis model NC/Nga mice

Environmental factors and the major histocompatibility complex (MHC) are involved in the pathogenesis of atopic dermatitis (AD). However, MHC type (H2 haplotype) of AD model mice NC/Nga is poorly understood. Alloreactive CD8⁺ or CD4⁺ T cells in NC/Nga strongly responded to each antigen-presenting cells (A/J: H-2^a, C57BL/6: H-2^b, BALB/c: H-2^d, or C3H/HeJ: H-2^k), suggesting that NC/Nga has other H2 haplotype. Polymorphic microsatellite (CA)ⁿ repeats in TNF-α gene differ based on the H2 haplotype at present. NC/Nga's (CA)ⁿ repeats (n = 19) were different from other examined strains, A/J (n = 14), BALB/c (n = 14), C3H/HeJ (n = 16), and C57BL/6 (n = 20). Using flow cytometry and genotyping, we demonstrated the NC/Nga H2 haplotype had a unique phenotype (K^d, I-A^k, and I-E^k) in which D^d and L^d lacked as protein despite sensitive mRNA detection. The loss of D^d and L^d was caused by forming a unique D^dm7/L^dm7-hybrid mutant (D/L^dm7). We propose to call this novel H2 haplotype the "H-2^nc," and provide the important information regarding the AD research using NC/Nga mice.

Pathogenic CD4+ T cells in patients with asthma

Asthma encompasses a variety of clinical phenotypes that involve distinct T cell-driven inflammatory processes. Improved understanding of human T-cell biology and the influence of innate cytokines on T-cell responses at the epithelial barrier has led to new asthma paradigms. This review captures recent knowledge on pathogenic CD4+ T cells in asthmatic patients by drawing on observations in mouse models and human disease. In patients with allergic asthma, TH2 cells promote IgE-mediated sensitization, airway hyperreactivity, and eosinophilia. Here we discuss recent discoveries in the myriad molecular pathways that govern the induction of TH2 differentiation and the critical role of GATA-3 in this process. We elaborate on how cross-talk between epithelial cells, dendritic cells, and innate lymphoid cells translates to T-cell outcomes, with an emphasis on the actions of thymic stromal lymphopoietin, IL-25, and IL-33 at the epithelial barrier. New concepts on how T-cell skewing and epitope specificity are shaped by multiple environmental cues integrated by dendritic cell "hubs" are discussed. We also describe advances in understanding the origins of atypical TH2 cells in asthmatic patients, the role of TH1 cells and other non-TH2 types in asthmatic patients, and the features of T-cell pathogenicity at the single-cell level. Progress in technologies that enable highly multiplexed profiling of markers within a single cell promise to overcome barriers to T-cell discovery in human asthmatic patients that could transform our understanding of disease. These developments, along with novel T cell-based therapies, position us to expand the assortment of molecular targets that could facilitate personalized treatments.

Spectrum of T-lymphocyte activities regulating allergic lung inflammation

Despite advances in the treatment of asthma, optimization of symptom control remains an unmet need in many patients. These patients, labeled severe asthma, are responsible for a substantial fraction of the disease burden. In these patients, research is needed to define the cellular and molecular pathways contributing to disease which in large part are refractory to corticosteroid treatment. The causes of steroid-resistant asthma are multifactorial and result from complex interactions of genetics, environmental factors, and innate and adaptive immunity. Adaptive immunity, addressed here, integrates the activities of distinct T-cell subsets and by definition is dynamic and responsive to an ever-changing environment and the influences of epigenetic modifications. These T-cell subsets exhibit different susceptibilities to the actions of corticosteroids and, in some, corticosteroids enhance their functional activation. Moreover, these subsets are not fixed in lineage differentiation but can undergo transcriptional reprogramming in a bidirectional manner between protective and pathogenic effector states. Together, these factors contribute to asthma heterogeneity between patients but also in the same patient at different stages of their disease. Only by carefully defining mechanistic pathways, delineating their sensitivity to corticosteroids, and determining the balance between regulatory and effector pathways will precision medicine become a reality with selective and effective application of targeted therapies.

Maternal sensitivity and social support protect against childhood atopic dermatitis

BACKGROUND

Many studies have identified associations between qualities of maternal-child relationships and childhood asthma, but few have examined associations with childhood atopic dermatitis (AD), a common precursor to asthma. Moreover, maternal psychological distress, including prenatal and postnatal depression, anxiety and stress, may increase risk, while social support from partners may reduce risk for childhood AD. We sought to uncover the association between maternal-infant relationship qualities (maternal sensitivity towards infant behavioral signals, controlling behavior, and unresponsiveness) and child AD after accounting for risk (i.e., prenatal and postnatal maternal depression, anxiety and stress) and protective (i.e., social support) factors.

METHODS

We conducted a secondary analysis of data collected on a subsample of 242 women and their infants enrolled during pregnancy in the ongoing Alberta Pregnancy Outcomes and Nutrition cohort study. Inclusion criteria required mothers to be >16 years of age, English speaking and <22 weeks gestational age at enrollment. Data on depression, anxiety and stress in the prenatal and postnatal periods and physician diagnosis of childhood AD at 18 months were gathered via maternal report. Maternal sensitivity, unresponsiveness and controlling behaviours were assessed via videotaped observations using the Child-Adult Relationship Experimental (CARE)-Index at 6 months of infant age.

RESULTS

Higher maternal sensitivity, or the inability of the mother to appropriately understand and respond to infant needs based on behavioral signals, predicted reduced odds of AD independent of and in combination with low prenatal and postnatal anxiety and high paternal support. After adjustment, higher maternal controlling behaviours and unresponsiveness also predicted greater odds of AD.

CONCLUSIONS

Low maternal sensitivity is a risk factor for childhood AD, independently and in combination with perinatal anxiety and low social support. Thus, interventions that improve maternal-infant relationship quality, especially sensitivity, reduce anxiety and improve social support from partners could reduce odds of childhood AD.

Therapeutic vaccines for allergic disease

Allergic diseases are highly prevalent worldwide and affect all age groups, contributing to a high personal and socioeconomic burden. Treatment with an “allergy vaccine” or allergen immunotherapy aims to provide long-lasting benefits by inducing unresponsiveness to the relevant antigen. The consequences of the therapy are considered disease modifying and range from dampening of the immediate immune responses to the reduction of secondary tissue remodeling. Furthermore, allergen immunotherapy interventions have a potential to slow or cease the development of additional allergic manifestations with a long-term overall effect on morbidity and quality of life. Here, we review proposed mechanisms underlying the therapeutic effects of immunotherapy for allergic diseases. Further, we discuss both standard and novel approaches and possible future directions in the development of allergen immunotherapy.

Filaggrin inhibits generation of CD1a neolipid antigens by house dust mite-derived phospholipase

Atopic dermatitis is a common pruritic skin disease in which barrier dysfunction and cutaneous inflammation contribute to pathogenesis. Mechanisms underlying the associated inflammation are not fully understood, and although Langerhans cells expressing the nonclassical major histocompatibility complex (MHC) family member CD1a are known to be enriched within lesions, their role in clinical disease pathogenesis has not been studied. We observed that house dust mite (HDM) allergen generates neolipid antigens presented by CD1a to T cells in the blood and skin lesions of affected individuals. HDM-responsive CD1a-reactive T cells increased in frequency after birth in individuals with atopic dermatitis and showed rapid effector function, consistent with antigen-driven maturation. In HDM-challenged human skin, we observed phospholipase A2 (PLA2) activity in vivo. CD1a-reactive T cell activation was dependent on HDM-derived PLA2, and such cells infiltrated the skin after allergen challenge. Moreover, we observed that the skin barrier protein filaggrin, insufficiency of which is associated with atopic skin disease, inhibited PLA2 activity and decreased CD1a-reactive PLA2-generated neolipid-specific T cell activity from skin and blood. The most widely used classification schemes of hypersensitivity suggest that nonpeptide stimulants of T cells act as haptens that modify peptides or proteins; however, our results show that HDM proteins may also generate neolipid antigens that directly activate T cells. These data define PLA2 inhibition as a function of filaggrin, supporting PLA2 inhibition as a therapeutic approach.

IL-13-producing BLT1-positive CD8 cells are increased in asthma and are associated with airway obstruction

BACKGROUND

The role of CD8 T lymphocytes in the pathogenesis of asthma is not well understood. We investigated whether a subset of IL-13-producing BLT1-positive CD8 T lymphocytes are present in asthmatic airways and are associated with impaired lung function.

METHODS

Bronchoalveolar lavage (BAL) cells were obtained from asthmatic (n = 39) and healthy control (n = 28) subjects. Cells were stimulated with phorbol ester and ionomycin in the presence of brefeldin A and stained for CD8, BLT1, and intracellular IL-13. The frequency of IL-13-producing BLT1-positive CD8 T lymphocytes was compared between the two groups and related to lung function, serum IgE levels, and reticular basement membrane (RBM) thickness.

RESULTS

A subset of CD8 T lymphocytes expressing BLT1 and producing IL-13 were detected in the airways of all asthmatic subjects. The frequency of this subset among recovered lymphocytes was significantly higher in the airways of asthmatic subjects compared with controls (mean ± SEM: 16.2 ± 1.4 vs 5.3 ± 0.5, respectively, P < 0.001) and correlated positively with serum IgE levels and RBM thickness. More importantly, the frequency of CD8 T lymphocytes co-expressing BLT1 and IL-13 was inversely related to FEV1 and FEF[25-75] percent predicted values (P < 0.001).

CONCLUSIONS

A subset of CD8 T lymphocytes expressing BLT1 and producing IL-13 is present in the airways of asthmatics. The accumulation of these cells is associated with airway obstruction, suggesting that they may play a significant pathogenic role in bronchial asthma.

Immune responses to inhalant allergens

This overview describes the nature of the immune responses induced by the inhalation of allergens. There is a dichotomy in that B cells have multiple mechanisms that limit the amount of immunoglobulin E (IgE) antibody production, whereas T-cell responses are large even in nonallergic subjects. With the possible exception of responses to cat allergen, however, T cells from nonallergic subjects have limited effector function of helping IgG antibody, and in house-dust mite allergy, this declines with age. Regulation by interleukin 10 (IL-10)-producing cells and CD25⁺ T-regulatory cells has been proposed, but critically, there is limited evidence for this, and many studies show the highest IL-10 production by cells from allergic subjects. Recent studies have shown the importance of nonlymphoid chemokines thymic stromal lymphopoietin and IL-27, so studying responses in situ is critical. Most sources of allergens have 1 or 2 dominant allergens, and for house-dust mite, it has been shown that people have a predictable responsiveness to high-, mid-and poor-IgE-binding proteins regardless of the total size of their response. This allergen hierarchy can be used to design improved allergen preparations and to investigate how antiallergen responses are regulated.

Increased frequencies of IL-31-producing T cells are found in chronic atopic dermatitis skin

Interleukin (IL)-31 has been associated with pruritus, a characteristic feature of atopic dermatitis (AD). Local T cell responses may be responsible for the increased level of IL-31 mRNA observed in AD. We investigated the frequency of IL-31-producing T cells in AD lesions, as well as their cytokine profile. T cells were isolated from chronic AD lesions, autologous blood and healthy donor skin. Intracellular expression of IL-31, IFN-γ, IL-13, IL-17 and IL-22 was measured using flow cytometry. T cells from AD lesions contained significantly higher percentages of IL-31-producing T cells compared to autologous blood and donor skin. Many IL-31-producing T cells co-produced IL-13 and to lesser extent IL-22, but rarely IFN-γ or IL-17. A substantial part of the IL-31-producing T cells did not co-produce any of the other cytokines and could therefore not be linked to any of the known functionally different T cell subsets. The T cell infiltrates were also relatively enriched for Th2/Tc2 and Th22/Tc22 cells, while frequencies of Th1/Tc1 and Th17 cells were decreased. This is the first report describing the detection of IL-31 at protein level in skin-infiltrating T cells. We show here that T cells in chronic AD skin produce IL-31 and that AD lesions contain increased levels of these IL-31-producing T cells. This suggests that a substantial part of previously reported increased IL-31 mRNA levels in AD skin is T cell derived and that these cells may be involved in the pathogenesis of AD.

CD4+ T cell depletion changes the cytokine environment from a TH1/TH2 response to a TC17-like response in a murine model of atopic dermatitis

Atopic dermatitis (AD) is a common inflammatory skin disease often associated with co-morbidities including allergic hypersensitivity. We have studied induced AD-like disease in NC/Nga mice using the hapten FITC. Following FITC-treatment the NC/Nga mice develop AD-like skin lesions in regard to the histopathological and immunological changes. Consistent with AD in humans the number of CD4(+) T cells within the blood and draining lymph nodes increases considerably. To evaluate the contribution of T(H) cells on disease development we examined the effect of CD4 depletion. Following CD4 depletion the mice still develop AD-like skin lesions characterized by e.g. increased epidermal proliferation, hyperkeratosis and cellular infiltrate, however, the underlying immunological mechanisms change. CD4 depletion results in increased IL-17A and IL-22 production, which traditionally are associated with T(H)17 cells. Using confocal microscopy, we demonstrate that epidermal CD8(+) cells are positive for IL-17A, indicating that these cells are T(C)17 cells, the cytotoxic T cell counterpart to T(H)17 cells. In conclusion, we show that NC/Nga mice develop AD-like disease following CD4 depletion. This is mirrored by an increased production of IL-17A, which we suggest are produced by T(C)17 cells. These findings support that CD8(+) T cells can play a role in AD.

Interaction of allergens, major histocompatibility complex molecules, and T cell receptors: a 'ménage à trois' that opens new avenues for therapeutic intervention in type I allergy

T cells are major players in the initiation and perpetuation of the allergic immune response. In this review, we summarize the current knowledge on allergen recognition by T lymphocytes and address the components of the trimeric recognition complex: T cell receptors, major histocompatibility complex molecules, and allergen-derived peptides. Furthermore, possible implications of this scientific background for future therapeutic developments are discussed.

The role of leukocytes, keratinocytes, and allergen-specific IgE in the development of atopic dermatitis

This review provides an overview of the inflammatory mechanisms and immunological aspects specific to atopic dermatitis. The review discusses publications on the roles of different T-cell subsets (that is, T helper 1 (Th1), Th2, T-regulatory, and Th17 cells), myeloid and plasmacytoid dendritic cells, and eosinophils. A further focus lies on keratinocyte-T-cell interactions, which may be of particular relevance in eczema. Mechanisms in innate and adaptive immunity that result in susceptibility to skin infections and in hyperreactivity to environmental stimuli, influencing the course and severity of atopic dermatitis, are summarized. Because the Journal of Investigative Dermatology has recently published reviews of specific features of barrier defects, defects in innate immunity, and, in this issue, genetics, these topics are only briefly discussed here in the context of immunology of atopic dermatitis.

Antigen-driven bystander effect accelerates epicutaneous sensitization with a new protein allergen

Exposure to protein allergen epicutaneously, inducing a Th2-dominant immune response, sensitizes the host to the development of atopic disease. Antigen-driven bystander effect demonstrates that polarized T cells could instruct naïve T cells to differentiate into T cells with similar phenotype. In this study, we aimed to determine the contribution of antigen-driven bystander effect on epicutaneous sensitization with a newly introduced protein allergen. BALB/c mice were immunized intraperitoneally with BSA emulsified in alum, known to induce a Th2 response, three weeks before given BSA and OVA epicutaneously. Lymph node cells from these mice restimulated with OVA secreted higher levels IL-4, IL-5 and IL-13 as compared with cells from mice without BSA immunization. In addition, BALB/c mice immunized subcutaneously with BSA emulsified in complete Freund's adjuvant, known to induce a Th1-predominant response, also induced higher Th1 as well as Th2 cytokine response when restimulated with OVA as compared with mice without immunization. We demonstrated that subcutaneous immunization with BSA in CFA induced Th2 as well as Th1 response. The threshold of epicutaneous sensitization to OVA was also reduced, possibly due to increased expressions of IL-4 and IL-10 in the draining lymph nodes during the early phase of sensitization. In conclusion, antigen-driven bystander effect, whether it is of Th1- or Th2-predominant nature, can accelerate epicutaneous sensitization by a newly introduced protein allergen. These results provide a possible explanation for mono- to poly-sensitization spread commonly observed in atopic children.

Suppression of allergic airway inflammation and IgE responses by a class I restricted allergen peptide vaccine

CD8 T cells are known to deviate CD4 T-cell responses from Th2 toward Th1. Reduction of Th2 cytokines and increased interferon-gamma ameliorates allergic airway disease. We have developed a novel approach to the suppression of allergic airway inflammation, by designing a MHC class I-restricted allergen peptide vaccine, which induces potent and long-lived CD8 T-cell responses. Vaccination of C57BL/6 mice before allergen sensitization completely prevented allergen-specific immunoglobulin E (IgE) antibody responses. Vaccination after sensitization failed to suppress IgE, but inhibited accumulation of eosinophils and neutrophils in airways after subsequent allergen challenge. Vaccination suppressed Th2 airway infiltration and enhanced the lung Th1 response without inducing excessive CD8 cellular infiltration or interleukin-17, and the combination of class I peptide with adjuvant was more effective than adjuvant alone. Airway hyperreactivity was prevented by vaccination in an allergen-specific fashion. Class I peptide vaccines might therefore represent a robust and long-lasting immunotherapeutic strategy in allergic disease.

History of allergy and reduced incidence of colorectal cancer, Iowa Women's Health Study

Previous epidemiologic studies have reported that a history of allergy is associated with reduced risk of colorectal cancer and other malignancies. We studied the association between allergy history and incident colorectal cancer (n=410) prospectively in 21,292 Iowa women followed for 8 years. Allergy was defined from four self-reported questions about physician-diagnosed asthma (a), hay fever (b), eczema or allergy of the skin (c), and other allergic conditions (d). A history of any allergy was inversely associated with incident colorectal cancer: after multivariate adjustment, the hazard ratio (HR) was 0.74 [95% confidence interval (95% CI), 0.59-0.94]. Compared with women with no allergy, women reporting only one of the four types of allergy and women reporting two or more types had HRs of 0.75 (95% CI, 0.56-1.01) and 0.58 (95% CI, 0.37-0.90), respectively (P trend=0.02). The inverse association persisted in analyses restricted to any type of nonasthmatic allergy (HR, 0.73; 95% CI, 0.56-0.95). HRs were similar for rectal and colon cancers as well as for colon subsites: proximal and distal (HRs for any allergy ranged from 0.63 to 0.78 across these end points). Allergy history, which may reflect enhanced immunosurveillance, is associated with a reduced risk of colorectal cancer.

Expression of naive/memory (CD45RA/CD45RO) markers by peripheral blood CD4+ and CD8 + T cells in children with asthma

Introduction:

The role of CD4⁺ T cells in the immunopathogenesis of asthma is well documented. Little is known about the role of CD8⁺ T cells. The aim of this study was to assess peripheral blood subsets of CD4⁺ and CD8⁺ T cells expressing naive/memory markers (CD45RA⁺/RO⁺) and the activation marker (CD25⁺) in children with allergic asthma.

Materials and Methods:

Peripheral blood mononuclear cells were isolated from children with allergic asthma and healthy children. T cell subsets were analyzed by flow cytometry for the expressions of CD45RA, CD45RO, and CD25. In this study, some differences in the memory compartment of peripheral blood T cells between asthmatic children and healthy controls were detected.

Results:

The absolute number of CD8⁺ T cells expressing CD45RO was significantly elevated and the percentages of CD3⁺ T cells expressing activation marker CD25 and of CD4⁺ T cells expressing memory marker CD45RO were significantly lower in children with asthma compared with controls. No correlation was found between severity of asthma and peripheral blood lymphocyte subsets.

Conclusions:

There were some differences in the memory compartment of peripheral blood T cells between asthmatic children and healthy controls. The increase in the number of CD8⁺ T cells expressing the memory marker (CD45RO) in children with allergic asthma may indicate that CD8⁺ T cells play a role in the pathogenesis of asthma.

Anti-lymphocyte function associated antigen-1 inhibits T-helper 2 function of human allergen-specific CD4+ T cells

BACKGROUND

Blockade of lymphocyte function associated antigen-1 (LFA-1) is proving successful in the management of psoriasis and other inflammatory skin conditions including atopic dermatitis (AD), but the dependence of allergen-specific CD4+ T-cell function on LFA-1 has not been studied extensively.

OBJECTIVES

We sought to investigate the potential ability of LFA-1 inhibition to influence keratinocyte presentation of allergen to specific T-helper (Th) 2 cell clones.

METHODS

Using human leucocyte antigen class II tetrameric complexes, we generated Der p 1-specific DRB1*1501-restricted CD4+ T-cell lines (n=5) and clones (n=4) from the peripheral blood of five adults with AD.

RESULTS

Using doses of anti-LFA-1 present in vivo, we observed significant inhibition (P<0.05) of allergen-specific CD4+ T-cell production of interleukin-4 with such inhibition occurring during presentation of allergen by keratinocytes.

CONCLUSIONS

These data show that at doses present in vivo, LFA-1 blockade inhibits keratinocyte presentation to allergen-specific Th2 cells, suggesting one mechanism through which anti-LFA-1 may be beneficial therapeutically.

Human keratinocyte induction of rapid effector function in antigen-specific memory CD4+ and CD8+ T cells

The ability of human keratinocytes to present antigen to T cells is controversial and, indeed, it has been suggested that keratinocytes may promote T cell hyporesponsiveness. Furthermore, it is unclear whether keratinocytes can process antigen prior to MHC class I and class II presentation. We tested the ability of keratinocytes to induce functional responses in epitope-specific CD4+ and CD8+ memory T cells using peptides, protein and recombinant expression vectors as sources of antigen. Keratinocytes were able to efficiently process and present protein antigen to CD4+ T cells, resulting in cytokine secretion (Th1 and Th2). This interaction was dependent on keratinocyte expression of HLA class II and ICAM-1, which could be induced by IFN-gamma. In addition, keratinocytes could present virally encoded or exogenous peptide to CD8+ T cells, resulting in T cell cytokine production and target cell lysis. Finally, T cell lines grown using keratinocytes as stimulators showed no loss of function. These findings demonstrate that keratinocytes are able to efficiently process and present antigen to CD4+ and CD8+ memory T cells and induce functional responses. The findings have broad implications for the pathogenesis of cutaneous disease and for transcutaneous drug or vaccine delivery.

T-cell responses to allergens

The allergic response in human beings is engineered by CD4(+) T lymphocytes, which secrete T(H)2 cytokines in response to activation by allergen-derived peptides. Although T(H)2 cells have been well characterized, defining the properties of allergen-specific T cells has proved challenging in human beings because of their low frequency within the T-cell repertoire. However, recent studies have provided insight into the molecular signature of long-lived human memory T(H)2 cells, which are allergen-specific. T-cell responses directed against allergens develop in early life and are heavily influenced by the type and dose of allergen, and possibly coexposure to microbial products. These responses are susceptible to suppression by regulatory T cells. This article highlights recent advances in the characterization of allergen-specific memory T(H)2 cells and discusses the heterogeneous nature of regulatory T cells and possible mechanisms of action. The relevance of T-cell epitope mapping studies to understanding the unique nature of T-cell responses to different allergens, as well as to peptide vaccine development, is reviewed. Experimental techniques and approaches for analyzing allergen-specific T cells and identifying novel T-cell epitopes are described that may lead to new T-cell-based therapies.

T and B cell responses to HDM allergens and antigens

House dust mites provide well-characterized proteins to study human responses to inhaled antigens. Even in the absence of allergy they induce a high frequency of T cell precursors. The healthy response manifests by T cell proliferation and Th1 cytokines with little antibody. Responses of allergic people include Th1 and Th2 cytokines and IgE, IgG1, and IgG4 antibodies. Regulatory cells limit effector responses in healthy people. About half the IgE and IgG antibodies bind the group 1 and 2 allergens and 30% bind the group 4, 5, and 7 allergens. Although HLA independent, the recognition of the group 1 allergen shows an immunodominant region and a T cell receptor bias. The major allergens are not produced in higher amounts than many of the poorly non-allergenic proteins. The non-allergenic mite ferritin antigen shows high T cell proliferative responses with mixed cytokine production.

Cross-priming with an epicutaneously introduced soluble protein antigen generates Tc1 cells

Epicutaneous sensitization with a protein antigen was demonstrated to induce a predominant type 2 CD4 T cell response with high IgE production in mice. On the other hand, its CD8 T cell responses have not been addressed probably partly because of the generally accepted concept that cross-priming of soluble protein is an inefficient process. Here, we used an established patch-applied murine model to demonstrate that cross-priming with an epicutaneously introduced soluble protein antigen, though inefficient, generated mainly Tc1 cells, but not Tc2 cells. In the presence of an irritant or hapten, the efficiency of this cross-priming process could be enhanced and more Tc1 cells were generated. CpG oligonucleotides also promote the generation of Tc1 cells. In contrast, lipopolysaccharide and poly (inosinic-cytidylic) acid [poly (I:C)] have no effect. Together, these results provide supportive evidence of the epicutaneous sensitization of human cutaneous lymphocyte-associated antigen-positive CD8 T cells found in the peripheral blood or tissues of patients. The surprising observation of the type 1 character of the generated CD8 T cells will also help us to better understand the complicated pathogenesis of atopic and cutaneous inflammatory diseases.

Interleukin-4 promotes human CD8 T cell expression of CCR7

Despite strong evidence supporting a pathway of human T cell differentiation characterized by changes in the expression of CCR7, CD28, CD27 and CD62L, few studies have addressed the mechanisms of pathway regulation. Cutaneous lymphocyte-associated antigen (CLA)-positive skin-homing CD8(+) T cells expressed significantly elevated levels of activation markers compared with CLA(-) CD8(+) T cells in individuals (n = 27) with cutaneous atopic disease. Despite such an activated phenotype, CLA(+) T cells expressed significantly higher levels of CCR7 than a CLA(-) T cell subset. Interleukin (IL)-4 was found to dramatically promote CCR7 expression by antigen-specific CD8(+) cells. Furthermore, skin-homing CD8(+) T cells from individuals with severe disease produced significantly less IL-10 than those derived from mildly affected atopic subjects. Thus in a T-helper 2 dominated disease, tissue-specific CD8(+) T cells show altered CCR7 expression and cytokine production, which may contribute to continued lymph node homing, antigen presentation and disease. IL-4 promotes expression of CCR7, a marker linked to existing models of CD8(+) T cell differentiation.

Functional and phenotypic characterization of CD8+CD28+ and CD28- T cells in atopic individuals sensitized to Dermatophagoides pteronyssinus

BACKGROUND

CD8+ T suppressor cells may play a role in immunoregulation. Recent studies have characterized this population by the lack of the CD28 molecule. These CD8+CD28 T cells differ phenotypically and functionally from CD8 + CD28 + T cells. Little is known about CD8 + CD28 cells in atopy. Our aim was to analyze the phenotype and functional properties of CD8 + CD28T cells in atopic and non-atopic individuals.

METHODS

Peripheral blood mononuclear cells (PBMC) were obtained after density gradient centrifugation. CD8 + CD28 and CD8 + CD28 + T cells were isolated using immunomagnetic beads. Relative percentages of these cells and expression of several phenotypic markers were analyzed by flow cytometry. Proliferation was assessed by thymidine incorporation in isolated populations and in co-cultures with PBMC using Dermatophagoides pteronyssinus as stimulus. Cytokine synthesis was evaluated in culture supernatants by cytometric bead array.

RESULTS

The relative percentages of CD8+CD28 T cells and their phenotypic expression in atopic and non-atopic volunteers were not significantly different. However, CD8 + CD28 T cells showed greater proliferation than did CD8+CD28+ T cells when stimulated with D. pteronyssinus, although cytokine synthesis patterns were similar. CD8+CD28 co-cultures with PBMC showed greater proliferation than CD8+CD28+ T cell co-cultures, but cytokine synthesis patterns were not different.

CONCLUSIONS

Our data confirm phenotypic and functional differences between CD28+ and CD28 T cells, irrespective of atopic status. Purified human CD8+CD28 T cells, freshly isolated from peripheral blood, do not have suppressor properties on allergen-specific proliferation or on cytokine synthesis in PBMC.

Cytokine-induced IL-10-secreting CD8 T cells represent a phenotypically distinct suppressor T-cell lineage

Populations of regulatory T cells (Tregs) control autoimmune and allergic immunopathology induced by self or foreign antigens. Several types of CD4(+) MHC class II-restricted Treg populations have been characterized, but the biology of CD8(+), MHC class I-restricted Tregs is less understood. We show here that CD8(+) Tregs are rapidly generated in the presence of IL-4 and IL-12, produce IL-10, and exhibit a unique cell-surface phenotype with coexpression of activation and naive cell-associated markers. They block activation of naive or effector T cells and suppress IgG/IgE antibody responses and graft-versus-host disease in vivo. Suppression is dependent on cell contact and mediated by direct T-cell-T-cell interaction that antagonizes T-cell-receptor (TCR) signals. The data establish the existence of a CD8 T-cell suppressor effector subset distinct in both phenotype and function from T cytotoxic 1 (Tc1) and Tc2 cells. Production of such CD8 Tregs has potential for cell-based therapy of CD4 or CD8 T-cell-mediated disease.

Sensitization to airborne environmental allergens: unresolved issues

Despite considerable advances in identifying the environmental agents that trigger allergy and the immunological mechanisms involved, progress in developing effective treatments remains frustratingly slow. Is it time to rethink some of the paradigms guiding this research?

CD8+ T cell contributions to allergen induced pulmonary inflammation and airway hyperreactivity

The pathogenesis of asthma has been linked to the production of type 2 cytokines, which can be expressed by several cell types in the lung. These studies investigated CD8(+) T cell responses in a murine cockroach antigen (CRA) model of asthma. The results from these present studies show that depletion of CD8(+) T cells after allergen sensitization to CRA significantly reduces airway hyperreactivity, airway eosinophilia and pulmonary type 2 cytokine levels. The data demonstrate that CD8(+) T cells from CRA-sensitized mice can produce type 2 cytokines IL-4, IL-5 and IL-13 upon antigen challenge, and that the transfer of these cells into naive mice will cause airway hyperreactivity when exposed to CRA. We found that the transferred airway response is dependent on both IL-4 and IL-13 from CD8(+) T cells using cytokine knockout mice. Compared to CD4(+) T cells, CD8(+) T cells were not as numerous in the lungs of sensitized and challenged mice, but were as efficacious in the transfer of airway disease. The most severe airway response was observed when both CD4(+) and CD8(+) T cells were transferred at the same time. Altogether, these studies highlight a role for CD8(+) T lymphocytes in the development of allergen-induced airway responses.

Bronchial CD8 cell infiltrate and lung function decline in asthma

RATIONALE

Patients with asthma have an accelerated decline in lung function, which can lead to irreversible airway obstruction. It is generally assumed that this is related to specific aspects of airway inflammation and/or remodeling.

OBJECTIVE

We investigated the prognostic significance of bronchial eosinophil and CD8+ cell counts and subepithelial reticular layer thickness for the subsequent decline in lung function in patients with asthma after 7.5 years of follow-up.

METHODS

In a prospective study, pre- and post-bronchodilator lung function (FEV1) was measured at baseline, and after 2 years and 7.5 years in 32 patients with asthma. Annual decline in lung function after 7.5 years of follow-up was related to type and severity of airway inflammation and remodeling in bronchial biopsies, which were taken at baseline and at Year 2.

RESULTS

Annual decline in post-bronchodilator FEV1 (mean [SD], 46.6 [53.4] ml/year) was significantly larger than the decline in prebronchodilator FEV1 (mean [SD], 27.5 [62.5] ml/year), indicating loss in reversibility. Although annual fall in post-bronchodilator FEV1 was not related to thickness of the reticular layer or to eosinophil counts in bronchial biopsies, there was a significant correlation with CD8+ T cells (r=-0.39, p=0.032). Analyzing the biopsies taken at Year 2, the significant association between annual fall in post-bronchodilator FEV1 and CD8 cells could independently be confirmed (r=-0.39, p=0.036).

CONCLUSION

The outcome of asthma, as determined by the annual decline in FEV1, can be predicted by the bronchial CD8+ cell infiltrate. This suggests that the inflammatory phenotype in asthma has prognostic relevance, which may require phenotype-specific therapeutic strategies.

Interleukin-4 induced down-regulation of skin homing receptor expression by human viral-specific CD8 T cells may contribute to atopic risk of cutaneous infection

Factors controlling the expression of cutaneous lymphocyte-associated antigen (CLA) by T cells are poorly understood, but data from murine and human CD4(+) T cell systems have suggested that cytokines play an important role. However, there are no data examining the influence of cytokines on the expression of CLA by human antigen-specific CD8(+) T cells. Peripheral blood mononuclear cells (PBMC) were isolated from 10 HLA-A*0201-positive healthy individuals. Using HLA-peptide tetrameric complexes refolded with immunodominant peptides from Epstein-Barr virus (EBV), cytomegalovirus (CMV) and influenza A virus, we investigated the temporal associations of CLA expression by viral-specific CD8(+) T cells following stimulation with antigen. Ex vivo influenza matrix-specific CD8(+) T cells expressed significantly (P < 0.05) greater levels of CLA than EBV BMLF1 and CMV pp65-specific CD8(+) T cells (mean 9.7% influenza matrix versus 1.4% BMLF1 versus 1.1% pp65) and these differences were sustained on culture. However, regardless of viral specificity, interleukin (IL)-12 and IL-4 induced significant (P < 0.05) dose-dependent up-regulation and down-regulation of CLA expression, respectively, with IL-4 showing a dominant negative effect. In many cases, IL-4 resulted in complete abrogation of detectable CLA expression by the viral-specific CD8(+) T cells. Overall these data demonstrate that CLA expression by human viral-specific CD8(+) T cells is highly dynamic and that IL-4 causes significant down-regulation. Disorders associated with a type 2 cytokine shift may reduce the efficiency of skin homing by viral-specific CD8(+) T cells. Furthermore, the ability to modify the local and systemic microenvironment may offer novel therapeutic strategies that influence tissue-specific T cell homing.

Immune dysregulation in allergic respiratory disease: the role of T regulatory cells

Although earlier research focused on the role of the polarity of T helper cell signalling as the defining factor in immune responses, it is now recognised that other cells with regulatory properties have a more key role. It has been recently proposed that allergic disease may result from an inappropriate balance between regulatory cells (including but not limited to CD4+ CD25+ T regulatory cells) and T helper type 2 (Th2) effector cells. In the airways, a number of other cells also have important regulatory effects on local immune responses, including epithelial cells and airway dendritic cells (DC). Allergic respiratory disease appears to be the culmination of both local epithelial dysfunction and generalised immune dysregulation resulting in Th2 propensity (atopic predisposition). Although these processes are related they also appear to occur independently. This review examines evolving models of allergy pathogenesis, including the newly recognised role of diverse groups of regulatory cells. Increasing rates of allergic disease (and other immune diseases) suggest that environmental changes may be having fundamental effects on common regulatory pathways. Understanding these influences and their mechanism of action could lead to strategies to prevent disease.

T cell epitope immunotherapy induces a CD4+ T cell population with regulatory activity

BACKGROUND

Synthetic peptides, representing CD4(+) T cell epitopes, derived from the primary sequence of allergen molecules have been used to down-regulate allergic inflammation in sensitised individuals. Treatment of allergic diseases with peptides may offer substantial advantages over treatment with native allergen molecules because of the reduced potential for cross-linking IgE bound to the surface of mast cells and basophils.

METHODS AND FINDINGS

In this study we address the mechanism of action of peptide immunotherapy (PIT) in cat-allergic, asthmatic patients. Cell-division-tracking dyes, cell-mixing experiments, surface phenotyping, and cytokine measurements were used to investigate immunomodulation in peripheral blood mononuclear cells (PBMCs) after therapy. Proliferative responses of PBMCs to allergen extract were significantly reduced after PIT. This was associated with modified cytokine profiles generally characterised by an increase in interleukin-10 and a decrease in interleukin-5 production. CD4(+) cells isolated after PIT were able to actively suppress allergen-specific proliferative responses of pretreatment CD4(neg) PBMCs in co-culture experiments. PIT was associated with a significant increase in surface expression of CD5 on both CD4(+) and CD8(+) PBMCs.

CONCLUSION

This study provides evidence for the induction of a population of CD4(+) T cells with suppressor/regulatory activity following PIT. Furthermore, up-regulation of cell surface levels of CD5 may contribute to reduced reactivity to allergen.

T cell epitope-specific defects in the immune response to cat allergen in patients with atopic dermatitis

Atopic dermatitis (AD) is often associated with high titer IgE antibodies (ab) to allergens, and IL-10-mediated regulation of IFN-gamma has been proposed to contribute to this IgE ab production. However, the relevance of IL-10 and IFN-gamma to IgE associated with AD has not been examined in the context of an allergen-specific system. Analysis of PBMC responses in vitro showed deficient T cell proliferation to overlapping IL-10- (peptide (P) 2:1) and IFN-gamma- (P2:2) inducing chain 2 major epitopes of cat allergen (Fel d 1) in cultures from sensitized AD patients (mean IgE to cat=20.9 IU/ml). Diminished IFN-gamma induction by Fel d 1 and P2:2, along with elevated peptide-induced IL-10 (except for P2:1) was observed in PBMC cultures from AD subjects compared with non-AD (sensitized and non-sensitized) subjects. Neither T cell proliferation nor IFN-gamma production to chain 2 epitopes could be restored by anti-IL-10 mAb in cultures from sensitized AD subjects. Moreover, allergen avoidance was associated with a paradoxical decrease in both IL-10 and IFN-gamma in peptide-stimulated PBMC from these subjects. Control of IFN-gamma production to chain 2 epitopes by IL-10 may be relevant to sensitization status. Development of high titer IgE ab in AD could reflect a failure of this mechanism.

High IFN-gamma production by CD8+ T cells and early sensitization among infants at high risk of atopy

BACKGROUND

High genetic risk (HR) of atopy among unstratified populations of infants is associated with attenuated IFN-gamma responses. However, the role of IFN-gamma in progression from HR status to active disease is less clear.

OBJECTIVE

To identify immune function markers in neonates with HR that are associated with positive atopic outcomes at 2 years.

METHODS

Cord blood mononuclear cells (CBMCs) were collected from 175 children with HR and cryopreserved. The children were assessed for atopy by skin prick at 0.5 and 2 years. CBMCs were thawed and stimulated with allergens and mitogens PHA and staphylococcal enterotoxin B (SEB), and cytokine responses were determined.

RESULTS

No correlations were observed between allergen-specific CBMC responses and atopic outcomes. In contrast, sensitization was strongly associated with polyclonal IFN-gamma responses to both PHA (P=.002) and SEB (P=.005), and also with SEB-induced IL-5 (P =.05), IL-10 (P =.02), and IL-13 (P =.01). Logistic regression analysis identified elevated PHA-induced IFN-gamma and SEB-induced IL-13 responses as the strongest independent predictors of atopy development. Cell separation studies confirmed CD8+ T cells as the source of approximately 90% of IFN-gamma production.

CONCLUSIONS

IFN-gamma produced by CD8+ T cells may synergize with T(H)2 cytokines in driving atopy development in children with HR.

T-cell immunotherapy of allergic disease: the role of CD8+ T cells

PURPOSE OF REVIEW

The scope of this review is to place recent advances in T-cell immunotherapy into an account of our understanding of the potential role of CD8+ T cells in the pathogenesis of allergic disease.

RECENT FINDINGS

Studies over the last year suggest that changes in CD8+ T-cell function may represent key events in successful T-cell immunotherapy. The first human human leukocyte antigen class I allergen epitopes have now been described and will provide further insights into the role of allergen-specific CD8+ T cells.

SUMMARY

The coupling of recent technical advances in the study of antigen-specific T cells with the knowledge of human allergen class I epitopes will promote rapid progress in the field, with potential consequences for the diagnosis, monitoring and immunotherapeutic treatment of affected individuals.

Detection and characterization of cellular immune responses using peptide-MHC microarrays

The detection and characterization of antigen-specific T cell populations is critical for understanding the development and physiology of the immune system and its responses in health and disease. We have developed and tested a method that uses arrays of peptide-MHC complexes for the rapid identification, isolation, activation, and characterization of multiple antigen-specific populations of T cells. CD4(+) or CD8(+) lymphocytes can be captured in accordance with their ligand specificity using an array of peptide-MHC complexes printed on a film-coated glass surface. We have characterized the specificity and sensitivity of a peptide-MHC array using labeled lymphocytes from T cell receptor transgenic mice. In addition, we were able to use the array to detect a rare population of antigen-specific T cells following vaccination of a normal mouse. This approach should be useful for epitope discovery, as well as for characterization and analysis of multiple epitope-specific T cell populations during immune responses associated with viral and bacterial infection, cancer, autoimmunity, and vaccination.

Drug development for asthma

Asthma is characterized by abnormal immune cell accumulation and activation in the airways as well as dysfunction of specialized parenchymal cells. Research strategies to define asthma pathogenesis have focused on the hypothesis that this altered state is a consequence of an excessive allergen-driven response. Drug development for asthma has been directed at improving existing agents and expanding new modalities that target the Th2 allergic cascade. Significant opportunities are being pursued in each of these areas. However, this strategy may not account for some critical aspects of asthma pathogenesis. Alternative considerations include the need for a multidisciplinary approach to dissect the complexity of the asthma phenotype as well as a better understanding of nonallergic factors (especially viral reprogramming of airway behavior) in the development of the phenotype. Each of these considerations may provide an alternative strategy for further drug development for asthma and other complex diseases.

Human dendritic cells activated by TSLP and CD40L induce proallergic cytotoxic T cells

Human thymic stromal lymphopoietin (TSLP) is a novel epithelial cell-derived cytokine, which induces dendritic cell (DC)-mediated CD4+ T cell responses with a proallergic phenotype. Although the participation of CD8+ T cells in allergic inflammation is well documented, their functional properties as well as the pathways leading to their generation remain poorly understood. Here, we show that TSLP-activated CD11c+ DCs potently activate and expand naive CD8+ T cells, and induce their differentiation into interleukin (IL)-5 and IL-13-producing effectors exhibiting poor cytolytic activity. Additional CD40L triggering of TSLP-activated DCs induced CD8+ T cells with potent cytolytic activity, producing large amounts of interferon (IFN)-gamma, while retaining their capacity to produce IL-5 and IL-13. These data further support the role of TSLP as initial trigger of allergic T cell responses and suggest that CD40L-expressing cells may act in combination with TSLP to amplify and sustain pro-allergic responses and cause tissue damage by promoting the generation of IFN-gamma-producing cytotoxic effectors.