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

Peptide immunotherapy (PIT) offers realistic prospects for the treatment of allergic diseases, including allergic asthma. Much is understood of the behavior of naive T cells in response to PIT. However, treatment of patients with ongoing allergic disease requires detailed understanding of the responses of allergen-experienced T cells. CD62L expression by allergen-experienced T cells corresponds to effector/effector memory (CD62L(lo)) and central memory (CD62L(hi)) subsets, which vary with allergen exposure (e.g., during, or out with, pollen season). The efficacy of PIT on different T helper 2 (Th2) cell memory populations is unknown. We developed a murine model of PIT in allergic airway inflammation (AAI) driven by adoptively transferred, traceable ovalbumin-experienced Th2 cells. PIT effectively suppressed AAI driven by unfractionated Th2 cells. Selective transfer of CD62L(hi) and CD62L(lo) Th2 cells revealed that these two populations behaved differently from one another and from previously characterized (early deletional) responses of naive CD4(+) T cells to PIT. Most notably, allergen-reactive CD62L(lo) Th2 cells were long-lived within the lung after PIT, before allergen challenge, in contrast to CD62L(hi) Th2 cells. Despite this, PIT was most potent against CD62L(lo) Th2 cells in protecting from AAI, impairing their ability to produce Th2 cytokines, whereas this capacity was heightened in PIT-treated CD62L(hi) Th2 cells. We conclude that Th2 cells do not undergo an early deletional form of tolerance after PIT. Moreover, memory Th2 subsets respond differently to PIT. These findings have implications for the clinical translation of PIT in different allergic scenarios

Mechanisms and predictive biomarkers of allergen immunotherapy in the clinic

Allergen-specific immunotherapy (AIT) remains the only disease-modifying treatment for IgE-mediated allergic diseases such as allergic rhinitis (AR). It can provide long-term clinical benefits when given for three years or longer. Mechanisms of immune tolerance induction by AIT are underscored by the modulation of several compartments within the immune system. These include repair of disruption in epithelial barrier integrity, modulation of the innate immune compartment that includes regulatory dendritic cells (DCreg) and innate lymphoid cells (ILCreg), and adaptive immune compartments such as induction of regulatory T and B cells. Altogether, these are also associated with dampening allergen-specific Th2 (Th2A) and T follicular helper cell responses and subsequent generation of blocking antibodies. Whilst AIT is effective in modifying the immune response, there is a lack of validated and clinically relevant biomarkers that can be used to monitor desensitization, efficacy, and the likelihood of response, all of which can contribute to accelerating personalized medication and increasing patient care. Candidate biomarkers comprise humoral, cellular, metabolic and in vivo biomarkers; however, these are primarily studied in small trials and require further validation. In this review, we evaluate the current candidates of biomarkers of AIT and how we can implement changes in future studies to help us identify clinically relevant biomarkers of safety, compliance and efficacy

Synchronous immune alterations mirror clinical response during allergen immunotherapy

BACKGROUND: Three years treatment with either sublingual or subcutaneous allergen immunotherapy has been shown to be effective and to induce long-term tolerance. The GRASS∗ trial demonstrated that two years treatment via either route was effective in suppressing the response to nasal allergen challenge, although was insufficient for inhibition one year after discontinuation. OBJECTIVE: To examine in the GRASS trial the time-course of immunologic changes during two years sublingual and subcutaneous immunotherapy and for one year after treatment discontinuation. METHODS: We performed multi-modal immunomonitoring to assess allergen-specific CD4 T cell properties, in parallel with analysis of local mucosal cytokine responses induced by nasal allergen exposure and humoral immune responses that included IgE-dependent basophil activation and measurement of serum inhibitory activity for allergen-IgE binding to B cells (IgE-Facilitated Allergen Binding). RESULTS: All three of these distinct arms of the immune response displayed significant and coordinate alterations during 2 years allergen desensitization, followed by reversal at 3 years, reflecting a lack of a durable immunological effect. Whereas frequencies of antigen-specific Th2 cells in peripheral blood determined by HLA class II tetramer analysis most closely paralleled clinical outcomes, IgE-antibody dependent functional assays remained partially inhibited one year following discontinuation. CONCLUSION: Two years of allergen immunotherapy were effective but insufficient for long-term tolerance. Allergen-specific Th2 cells most closely paralleled the transient clinical outcome and it is likely that recurrence of the T cell 'drivers' of allergic immunity abrogated the potential for durable tolerance. On the other hand, persistence of IgE-blocking antibody one year after discontinuation may be an early indicator of a pro-tolerogenic mechanism