PhI p 6

Pollen allergen Phl p 6 is a significant allergen derived from Timothy grass (Phleum pratense) pollen. It is known to cause allergic reactions in a substantial portion of individuals sensitive to grass pollen. Recombinant Phl p 6 (rPhl p 6) is a laboratory-produced version of this allergen, which is used for various research and diagnostic purposes.

Phl p 6 is an acidic protein with a molecular weight of approximately 11.8 kDa . It exhibits an almost exclusive α-helical secondary structure, as determined by circular dichroism spectroscopy . The recombinant form of Phl p 6 is produced in various expression systems, including SF9 cells, and is often tagged for purification purposes .

Phl p 6 is a major allergen, reacting with serum IgE from about 75% of grass pollen-allergic patients . The N-terminal region of the protein is crucial for IgE recognition, making it a key target for diagnostic tests and potential therapeutic interventions . Recombinant Phl p 6 can elicit dose-dependent basophil histamine release and immediate-type skin reactions in allergic individuals .

The structural stability of Phl p 6 is influenced by pH levels, which affect its conformational flexibility and susceptibility to proteolytic degradation . Studies using constant pH molecular dynamics (cpH-MD) techniques have shown that endosomal acidification can lead to local unfolding of the protein, particularly in regions containing T-cell epitopes and early proteolytic cleavage sites . This local unfolding is a prerequisite for proteolytic cleavage and subsequent immune response.

Due to its high prevalence in grass pollen-allergic patients, Phl p 6 is extensively studied for its role in allergic reactions. Recombinant Phl p 6 is used in both in vitro and in vivo diagnostic tests to identify grass pollen allergies . Additionally, N-terminal deletion mutants of Phl p 6 with reduced IgE binding capacity are being explored as potential candidates for immunotherapy, offering a lower risk of anaphylactic side effects .