Cluster-immunotherapy in allergic rhinoconjunctivitis. A review of an innovative, new therapeutic approach

Besides allergen avoidance specific immunotherapy (SIT) represents the only curative (causal) treatment available for patients with allergic rhinoconjunctivitis. Clinical efficacy of this treatment depends on the correct indication for SIT, specific allergen-preparation used, quality and cumulative dose of the allergen-extracts administered and, moreover, the dosage-schedule. In conventional SIT, gradually ascending dosages of the allergen extract are injected subcutaneously in weekly intervals ("dose-increase period") until the individual maximum dose is reached ("dose-maintenance period"). Several dosage protocols have been designed which require 4 - 16 weeks for the initial, dose-increase period. Therefore, the aim of Cluster-SIT-schedules is to reach the maintenance dose more rapidly by administering 2 - 3 injections per treatment day. Depot-allergen-preparations as well as chemically-modified allergen-preparations ("allergoids") have been used in different Cluster-protocols published. In the first part, this review focusses on the rate of adverse events of Cluster-schedules in recently published trials in the current literature. Clear evidence was found that the frequency and severity of adverse events in these protocols are comparable to those in conventional, classic schedules. In the second part it overviews the onset and extent of clinical and immunological effects of accelerated Cluster-schedules. For both adult and paediatric allergic patients it could be found that clinical benefits and change of immunological pattern appear more rapidly after Cluster-SIT in comparison to conventional-schedules. Taken together, Cluster-protocols might become an interesting and alternative therapy-option for the dose-increase period of SIT in the future.