Prevention of a β-lactoglobulin specific IgE response in the mouse via gene immunisation.

Gene immunisation consists of injecting a vector of bacterial expression containing cDNA from a known protein. Some studies have shown that the injection of such a plasmid in the mouse results in a type Th1 (IgG2a) specific immune response. This polarisation of the immune response has been described in the case of respiratory allergens (Der p5, Bet vl), which prevent all subsequent type Th2 response (IgG1 and IgE). The aim of our study was to investigate such a preventive effect in the case of a food allergen, ie, bovine beta-lactoglobulin (beta LG). This protein is a major allergen in cow's milk, and the presence of anti-beta LG IgE has been demonstrated in 60% of patients who are allergic to milk. In the present study, an experimental induction model was first set up for allergy to beta LG in Balb/c mice. Quantitative dosages of the various isotypes (IgE, IgG1, and IgG2a) were determined, thereby permitting the total antibody and anti-beta LG reaction to be examined in this group of mice. A plasmid containing the beta LG cDNA was then constructed. This plasmid was found to be functional in vitro, and following its injection into the mouse tibia muscle, it allowed the in situ expression of beta LG in its native form. In addition, the primary response induced by this type of immunisation was characterised by a mixed IgG 1/lgG2a response, and by an absence of anti-beta LG IgE. In mice which had been preimmunised by gene vaccine, the resulting sensitivity induced by the protein could be observed in the persistent decrease of over 95% in the specific IgE rate, and by the induction of a marked anti-beta LG IgG2a response (not present in the control mice). The use of efficient non pathogenic vectors which can be orally administered could provide a mean of specific protection in the case of severe food allergies. (C) 2000 Editions scientifiques et medicales Elsevier SAS.