Coronavirus disease 2019, allergic diseases, and allergen immunotherapy: Possible favorable mechanisms of interaction

Abstract

Background: Both, allergen immunotherapy (AIT) and SARS-COV-2 infection cause a set of immunologic changes that respectively vary during the course of the treatment or the disease. Objective: To review immune changes brought along by each of these entities and how they might interrelate. Methods: We start presenting a brief review of the structure of the new coronavirus and how it alters the functioning of the human immune system. Subsequently, we describe the immune changes induced by AIT and how these changes could be favorable or unfavorable in the allergic patient infected with SARS-CoV-2 at a particular point of time during the evolving infection. Results: We describe how a healthy immune response against SARS-CoV-2 develops, versus an immune response that is initially suppressed by the virus, but ultimately overactivated, leading to an excessive production of cytokines (cytokine-storm-like). These changes are then linked to the clinical manifestations and outcomes of the patient. Reviewing the immune changes secondary to AIT, it becomes clear how AIT is capable of restoring a healthy innate immunity. Investigators have previously shown that the frequency of respiratory infections is reduced in allergic patients treated with AIT. On the other hand it also increases immunoregulation. Conclusion: As there are many variables involved, it is hard to predict how AIT could influence the allergic patient's reaction to a SARS-CoV-2 infection. In any case, AIT is likely to be beneficial for the patient with allergic rhinitis and/or allergic asthma in the context of the SARS-CoV-2 pandemic as controlling allergic diseases leads to a reduced need for contact with healthcare professionals. The authors remind the reader that everything in this article is still theoretical, since at the moment, there are no published clinical trials on the outcome of COVID-19 in allergic patients under AIT.

Allergen-specific immunotherapy practices and course of coronavirus disease 2019 (COVID-19) in patients during COVID-19

“…The lack of published clinical studies on the outcome of COVID-19 in allergic patients under AIT causes the information to remain theoretical [ 23 ]. Our study presents a real-life data that will contribute to theoretical knowledge.…”

International consensus statement on allergy and rhinology: Allergic rhinitis – 2023

“…AIT has been shown to improve symptom control with a decrease in respiratory infections and antibiotic use 3425 . Prior studies with viral infections including influenza, cytomegalovirus (CMV), and HIV have not shown changes in the efficacy or safety of AIT 3392 .…”

Neuronal-Immune Cell Units in Allergic Inflammation in the Nose

“…However, these processes can be beneficial or harmful. Neurotransmitters, such as L-glutamate (L-Glu) and dopamine (DA), can exert exitotoxic and neurotoxic effects [27][28][29], whereas pro-inflammatory cytokines such as IL-1, IL-6, and TNF-α are able to evoke a "cytokine storm" and destroy the body functioning up to a life-threatening condition, e.g., in COVID-19 [30,31]. In addition, the neuroimmune network is closely linked with the concept of "neurogenic" inflammation [21] since nociceptive primary afferent neurons express many neuro molecules displaying influence over immune cells, enable damage to the tissues of physiological barriers that they innervate, and modify the sensory input before it reaches the CNS.…”