Phleum pratense alone is sufficient for allergen-specific immunotherapy against allergy to Pooideae grass pollens

Specific immunotherapy is the only causal treatment of allergy available today. Traditionally, therapeutic products based on either a single grass species or a mix of such extracts are used for grass pollen immunotherapy. Investigations comparing the immunological response to these allergen preparations are needed to ensure optimal treatment. The objective of this study was to investigate patterns of T and B cell cross-reactivity to Pooideae single-species extracts and to extract mixes. IgG4 induced by immunotherapy with Phleum pratense extract was investigated for cross-reactivity using nine single-species extracts and four mixes. For the mixes, studies of IgE cross-reactivity were also performed. T cell cross-reactivity was investigated in lines specific to nPhl p 1 or nPhl p 5 allergens, and the amounts of group 1 and 5 allergens in the extracts were quantified by a single radial immunodiffusion. The levels of treatment-induced IgG4 detected by all the extracts displayed a clear correlation to that detected by the P. pratense pollen extract. The IgE studies confirmed the cross-reactivity of P. pratense-specific B cells towards the allergens contained in the mixes, and the T cell studies demonstrated cross-reactivity towards group 1 and 5 major allergens in extracts of six temperate grass species. Extensive T and B cell cross-reactivity was observed towards the allergens of the Pooideae grasses, and the degree of B cell cross-reactivity was independent of the number of species included in the extract mixes. This implies that treatment with pollen extract of just one Pooideae species will affect the allergic responses caused by any of the temperate grasses in this subfamily.