Purified Native and Recombinant Major Alternaria alternata Allergen (Alt a 1) Induces Allergic Asthma in the Murine Model

Alternaria Allergy and Immunotherapy

BACKGROUND

Allergen immunotherapy (AIT) is the only known causative treatment for Alternaria allergy, but the difficulty in standardizing Alternaria extracts hampers its effectiveness and safety.

SUMMARY

Alternaria, a potent airborne allergen, has a high sensitization rate and is known to trigger the onset and exacerbation of respiratory allergies, even inducing fungal food allergy syndrome in some cases. It can trigger a type 2 inflammatory response, leading to an increase in the secretion of type 2 inflammatory cytokines and eosinophils, which are the culprits behind allergic symptoms. Diagnosing Alternaria allergy is a multistep process, involving a careful examination of clinical symptoms, medical history, skin prick tests, serum-specific IgE detection, or provocation tests. Alt a1, the major component of Alternaria, is a vital player in diagnosing Alternaria allergy through component-resolved diagnosis. Interestingly, Alternaria can reduce the protein activity of other allergens like pollen and cat dander when mixed with them. In order to solve the problems of standardization, efficacy and safety of traditional Alternaria AIT, novel AIT methods targeting Alt a1 and innovative vaccines such as epitope, DNA, and mRNA vaccines seem promising in bypassing the standardization issue of Alternaria extracts. But these studies are in early stages, and most researches are still focused on animal models, calling for more evidence to validate their use in humans.

KEY MESSAGES

This review delves into the various aspects of Alternaria allergy, including characteristics, epidemiology, immune mechanisms, diagnosis, clinical manifestations, and the application and limitations of Alternaria AIT, aiming to provide a foundation for the management of patients with Alternaria allergy.

Blocking CD226 regulates type 2 innate lymphoid cell effector function and alleviates airway hyperreactivity

BACKGROUND

Type 2 innate lymphoid cells (ILC2s) play a pivotal role in type 2 asthma. CD226 is a costimulatory molecule involved in various inflammatory diseases.

OBJECTIVE

We aimed to investigate CD226 expression and function within human and mouse ILC2s, and to assess the impact of targeting CD226 on ILC2-mediated airway hyperreactivity (AHR).

METHODS

We administered IL-33 intranasally to wild-type mice, followed by treatment with anti-CD226 antibody or isotype control. Pulmonary ILC2s were sorted for ex vivo analyses through RNA sequencing and flow cytometry. Next, we evaluated the effects of CD226 on AHR and lung inflammation in wild-type and Rag2-/- mice. Additionally, we compared peripheral ILC2s from healthy donors and asthmatic patients to ascertain the role of CD226 in human ILC2s.

RESULTS

Our findings demonstrated an inducible expression of CD226 in activated ILC2s, enhancing their cytokine secretion and effector functions. Mechanistically, CD226 alters intracellular metabolism and enhances PI3K/AKT and MAPK signal pathways. Blocking CD226 ameliorates ILC2-dependent AHR in IL-33 and Alternaria alternata-induced models. Interestingly, CD226 is expressed and inducible in human ILC2s, and its blocking reduces cytokine production. Finally, we showed that peripheral ILC2s in asthmatic patients exhibited elevated CD226 expression compared to healthy controls.

CONCLUSION

Our findings underscore the potential of CD226 as a novel therapeutic target in ILC2s, presenting a promising avenue for ameliorating AHR and allergic asthma.

Changes of allergic inflammation and immunological parameters after Alt a 1 and A. alternata immunotherapy in mice

Background

The efficacy of allergen-specific subcutaneousimmunotherapy (SCIT) with Alt a 1 of the fungus A. alternata is still unknown. Yet, few studies compare the therapeutic effects and immunological mechanisms of Alt a 1 and A. alternata extracts. We aim to explore and compare the changes in allergic inflammation and immunological mechanisms of Alt a 1 and A. alternata in mice.

Methods

Female BALB/c mice administrated recombinant Alt a 1 (rAlt a 1), native Alt a 1 (nAlt a 1), and A. alternata. Lung histology, airway hyper-reactivity (AHR), bronchoalveolar lavage fluid (BALF) cytokine levels, serum immunoglobulin responses, the expression of Bcl-6, the percentages of T follicular helper cells (Tfh), cytokine-related Tfh subtypes, regulatory B cells (Breg), and IL-10+ Breg cells were detected.

Results

High-purity nAlt 1 protein was obtained. SCIT with Alt a 1 and Alternaria decreased airway and lung inflammation, including improvement of lung pathology, lower levels of AHR, reduction of total cell numbers, and IL-4 and IL-13 levels in BALF. Furthermore, Alt a 1-SCIT effectively suppressed the IgE responses, elevated IgG titers, and was superior in decreasing the expression of Bcl-6. Additionally, Alternaria-SCIT significantly decreased the expression of Tfh cells, L-4+ Tfh, and IL-5+ Tfh cells in the spleen, whereas Alt a 1 showed superior therapeutic effects in the lymph node. IL-13+ Tfh cells in these two treatment groups not being significant. IL-17A+ Tfh cells were alleviated most effectively after A. alternata-SCIT in both the spleen and lymph node. Intriguingly, IL-10+ Breg cells decreased remarkably in response to SCIT with rAlt a 1.

Conclusions

Treatments with Alt a 1 and A. alternata extracts had beneficial effects on allergic inflammation. Alt a 1-SCIT resulted in prominent improvement in the immunoglobulin responses, Bcl-6, and IL-10+ Breg cells. Alternaria-SCIT was more likely to suppress the expression of Tfh and cytokine-related Tfh subtypes.