Antisense-mediated silencing of a gene encoding a major ryegrass pollen allergen

Type 1 allergic reactions, such as hay fever and allergic asthma, triggered by grass pollen allergens are a global health problem that affects approxi mate to 20% of the population in cool, temperate climates. Ryegrass is the dominant source of allergens because of its prodigious production of airbor ne pollen. Lol p 5 is the major allergenic protein of ryegrass pollen, judg ing from the fact that almost all of the individuals allergic to grass poll en show presence of serum IgE antibodies against this protein. Moreover, ne arly two-thirds of the IgE reactivity of ryegrass pollen has been attribute d to this protein. Therefore, it can be expected that down-regulation of Lo l p 5 production can significantly reduce the allergic potential of ryegras s pollen. Here, we report down-regulation of Lol p 5 with an antisense cons truct targeted to the Lol p 5 gene in ryegrass. The expression of antisense RNA was regulated by a pollen-specific promoter. Immunoblot analysis of pr oteins with allergen-specific antibodies did not detect Lol p 5 in the tran sgenic pollen. The transgenic pollen showed remarkably reduced allergenicit y as reflected by low IgE-binding capacity of pollen extract as compared wi th that of control pollen. The transgenic ryegrass plants in which Lol p 5 gene expression is perturbed showed normal fertile pollen development, indi cating that genetic engineering of hypoallergenic grass plants is possible.