ABSTRACT Introduction: The House Dust Mite Blomia tropicalis (Bt) is an important etiological agent of allergic asthma in tropical areas. Bt is substantially apart from the genus Dermatophagoides, which is more common globally. The objective of this paper was to assess the immunobiological features of Bt allergens. Methods: Purified allergens from Bt cultures were used, based on a technological platform developed at BIOCEN. Bt formulations were evaluated in murine models of respiratory allergy and in clinical studies of asthma immunotherapy with the VALERGEN®-BT vaccine. Mass spectrometry was used for molecular characterization and anti-Blo_t_13 monoclonal antibodies, obtained in BIOCEN, for epitope mapping. Results and Discussion: For the first time, the interaction of Bt allergens with innate immunity TLR receptors and the induction of neutrophilic inflammation, a known feature of the severe asthma phenotype, was identified. Native Blo_t_2 was identified as the predominant component of allergenic extracts, showing high IgE binding frequency in Cuban asthmatics (80 %), greater than Blo_t_5, currently considered the major allergen. Moreover, the IgE epitopes and cross-reactivity to human proteins of another Bt allergen, Blo_t_13, were identified. The first piece of evidence in humans of the specific and non-cross-reactive effect of Bt immunotherapy towards Dermatophagoides allergens was obtained. These results guided the design of a second-generation therapeutic vaccine, Prolinem®-BT, using alumina and TLR4 ligands as adjuvants. Its preclinical development results showed its antiallergic effect with only three doses, and its safety. Conclusion: Overall, these results confirm the need for the inclusion of Bt-specific immunotherapy for the effective management of allergic asthma in tropical countries.

RESUMEN Introducción: El ácaro del polvo doméstico Blomia tropicalis (Bt) es un agente etiológico importante del asma alérgica en zonas tropicales, que se distingue sustancialmente del género Dermatophagoides, más común globalmente. El objetivo de este trabajo fue evaluar las propiedades inmunobiológicas de los alergenos de Bt. Métodos: Se emplearon alérgenos purificados de cultivo de Bt, como plataforma tecnológica desarrollada en el Centro Nacional de Biopreparados (BIOCEN), se evaluaron formulaciones de Bt en modelos murinos de alergia respiratoria y en estudios clínicos de inmunoterapia en asmáticos con la vacuna VALERGEN®-BT. Se empleó espectrometría de masa para la caracterización molecular y anticuerpos monoclonales anti Blo_t_13, obtenidos en BIOCEN, para el mapeo de epítopes. Resultados y discusión: Se evidenció por primera vez la interacción de Bt con receptores TLR de la inmunidad innata e inducción de inflamación neutrofílica, característica del fenotipo severo del asma. Se identificó a Blo_t 2 como el componente predominante en los extractos alergénicos, con alto reconocimiento de IgE en asmáticos cubanos (80 %), mayor que Blo_t 5, considerado actualmente el alergeno principal. Se identificaron epítopes de otra molécula: Blo_t_13 y su reactividad cruzada con proteínas humanas. Se obtuvieron las primeras evidencias en humanos del efecto específico y no cruzado de la inmunoterapia con Bt hacia Dermatophagoides. Estos resultados guiaron el diseño de la vacuna terapéutica de segunda generación Prolinem®-BT empleando como adyuvante alúmina y ligandos TLR4. Los resultados preclínicos mostraron su efecto antialérgico con solo 3 dosis y su seguridad. Como conclusiones se confirma la necesidad de la inclusión de la inmunoterapia a Bt, para el manejo efectivo del asma alérgica en los trópicos.

Asthma results from allergen-driven intrapulmonary Th2 response, and is characterized by intermittent airway obstruction, airway hyperreactivity (AHR), and airway inflammation. Accumulating evidence indicates that inflammatory diseases of the respiratory tract are commonly associated with elevated production of nitric oxide (NO). It has been shown that exhaled NO may be derived from constitutive NO synthase (NOS) such as endothelial (NOS 3) and neural (NOS 1) in normal airways, while increased levels of NO in asthma appear to be derived from inducible NOS2 expressed in the inflamed airways. Nevertheless, the functional role of NO and NOS isoforms in the regulation of AHR and airway inflammation in human or experimental models of asthma is still highly controversial. In the present commentary we will discuss the role of lipopolysaccharides contamination of allergens as key element in the controversy related to the regulation of NOS2 activity in experimental asthma.

We summarize here the main characteristics of a novel model of pulmonary hypersensitivity. Mice were immunized with a subcutaneous implant of a fragment of heat solidified chicken egg white and 14 days later challenged with ovalbumin given either by aerosol or by intratracheal instillation. This procedure induces a persistent eosinophilic lung inflammation, a marked bone marrow eosinophilia, and Th2-type isotypic profile with histopathological findings that resemble human asthma. Further, this model is simple to perform, reproducible in different strains of mice, does not require adjuvants nor multiple boosters. Based on these characteristics we propose it as a suitable murine model of allergic eosinophilic lung inflammation.