Immunological effects of adjuvanted low‐dose allergoid allergen‐specific immunotherapy in experimental murine house dust mite allergy. Issue 3 (26th July 2021) - Heldner, Alexander
Abstract: Background: Native allergen extracts or chemically modified allergoids are routinely used to induce allergen tolerance in allergen‐specific immunotherapy (AIT), although mechanistic side‐by‐side studies are rare. It is paramount to balance optimal dose and allergenicity to achieve efficacy warranting safety. AIT safety and efficacy could be addressed by allergen dose reduction and/or use of allergoids and immunostimulatory adjuvants, respectively. In this study, immunological effects of experimental house dust mite (HDM) AIT were investigated applying high‐dose HDM extract and low‐dose HDM allergoids with and without the adjuvants microcrystalline tyrosine (MCT) and monophosphoryl lipid A (MPL) in a murine model of HDM allergy. Methods: Cellular, humoral, and clinical effects of the different AIT strategies were assessed applying a new experimental AIT model of murine allergic asthma based on physiological, adjuvant‐free intranasal sensitization followed by subcutaneous AIT. Results: While low‐dose allergoid and high‐dose extract AIT demonstrated comparable potency to suppress allergic airway inflammation and Th2‐type cytokine secretion of lung‐resident lymphocytes and draining lymph node cells, low‐dose allergoid AIT was less effective in inducing a potentially protective IgG1 response. Combining low‐dose allergoid AIT with MCT or MCT and dose‐adjusted MPL promoted Th1‐inducing mechanisms and robust B‐cell activation counterbalancing the allergic Th2 immune response. Conclusion: Low allergen doses induce cellular and humoral mechanisms counteracting Th2‐driven inflammation by using allergoids and dose‐adjusted adjuvants. In light of safety and efficacy improvement, future therapeutic approaches may use low‐dose allergoid strategies to drive cellular tolerance and adjuvants to modulate humoral responses. Abstract : In experimental HDM AIT, a 220‐fold reduced allergen dose is equally effective in control of allergic inflammation when HDM allergoids instead of extracts are applied. Low‐dose nonadjuvanted allergoid AIT is less effective in inducing a potentially protective IgG1 response. Combining low‐dose allergoid AIT with the adjuvant MCT or the adjuvant system MCT + MPL promotes Th1‐inducing mechanisms and robust B‐cell activation. Abbreviations: AIT, allergen‐specific immunotherapy; HDM, house dust mite; MCT, microcrystalline tyrosine; MPL, monophosphoryl lipid A; sIgG, specific immunoglobulin G; tIgG, total immunoglobulin G