444. One-Time Gene Therapy to Prevent Peanut-Induced Anaphylaxis

Abstract

Peanut allergy is a major public health problem that accounts for the majority of fatal food-induced anaphylactic reactions. There are no curative or preventative therapies. Therapy with omalizumab, a human anti-IgE monoclonal antibody, is transiently effective, but it must be administered parenterally, has a short half-life and is costly, thus it is challenging to use as a preventative for peanut allergy. To circumvent this challenge, we hypothesized that a one-time administration of an adeno-associated virus (AAV) gene transfer vector expressing the genetic sequence of omalizumab would provide persistent high circulating levels of anti-IgE sufficient to protect against repeated peanut exposure in the peanut allergic host. To assess this hypothesis, we created a humanized murine model of peanut allergy by reconstituting NOD-scid IL2rgnull mice with 3 x107 blood mononuclear cells (PBMC) derived from peanut allergic individuals or non-allergic controls and treating the mice with a non-human primate serotype rh.10 AAV expressing omalizumab (AAVrh.10anti-IgE) or control vector. Administration of a single dose (1×1011 gc) of AAVrh.10anti-IgE resulted in persistent high levels of anti-IgE in both wild type and humanized mouse models, with anti-IgE levels > 400 mg/ml at 6 wk and remained at similar levels to the last time point evaluated at 24 wk in wild type mice and levels above 220 mg/ml were achieved in NSG mice at wk 8. No anti-IgE was detected in serum from mice that received a non-relevant control vector or PBS alone. The humanized NOD-scid IL2rgnull mice were sensitized intraperitoneally with crude peanut extract (CPE) weekly for 4 wk and then challenged with CPE via oral gavage. Total serum human IgG, IgE and peanut-specific IgE were measured weekly. After challenge, allergic phenotype was assessed using an anaphylaxis score, histamine levels, rectal temperature and behavior. All NSG mice were successfully reconstituted with mononuclear cells as measured by persistent levels of human IgG. Mice treated with AAVrh.10anti-IgE had elevated total and peanut-specific IgE from day 28 onwards with total IgE lower in the AAVrh.10anti-IgE treated mice. Strikingly, after peanut challenge, AAVrh.10anti-IgE treated mice displayed a less severe allergic phenotype compared to those that received the control vector as defined by decreased histamine release, a lower anaphylaxis score, no drop in rectal temperature and suppressed ambulation. These results demonstrate that a single treatment with AAVrh.10anti-IgE provides long term protection from peanut allergen challenge in the peanut sensitized population, representing a paradigm shift in current therapeutic approaches.