Decline of Ves v 5-specific blocking capacity in wasp venom-allergic patients after stopping allergen immunotherapy.

While allergen-specific immunotherapy (AIT) is very efficient in hymenoptera venom (HV)-allergic patients, long-term outcome after finishing AIT is not well investigated, especially regarding mechanisms that are suggested to contribute to allergen-specific tolerance. Here, we analyse the Ves v 5-inhibitory activity of sera from wasp venom-allergic patients using the novel cell-free enzyme-linked immunosorbent facilitated antigen binding (ELIFAB) assay. Compared to pre-AIT, sera from patients undergoing AIT displayed an increased ability to inhibit Ves v 5 binding by IgE antibodies. In contrast, this inhibitory activity was reduced in patients having finished AIT 5-12 years ago. Allergen-blocking capacity correlated with serum concentrations of Ves v 5-specific IgG4 which rose during AIT but almost reached pretreatment levels in patients who had stopped AIT more than 5 years ago. These data raise questions about how long allergen tolerance is maintained in AIT-treated HV-allergic patients and suggest that the ELIFAB assay might be an easy-to-use tool assessing long-term tolerance in patients treated with HV-AIT.