Enzymes play an important role in inducing airway
inflammation, but knowledge is limited to few
proteins. This study was carried out to assess the role of Epi p 1, a
serine protease of Epicoccum purpurascens, in inducing
allergy and
inflammation in a murine model. Balb/c mice were sensitized with Epi p 1 active
protease (EAP) or Epicoccum extract. Subsequently, Epi p 1 sensitized mice were boosted on day 14 with EAP or inactivated
protease (EIAP). Three intranasal challenges were given and mice were killed to obtain blood, bronchoalveolar lavage fluid (BALF), spleen and lung tissues. Cellular airways infiltration,
immunoglobulin E (Ig)E titres and
cytokine levels in BALF and splenocyte culture supernatant were compared. Mice immunized with EAP had higher Epi p 1-specific serum
IgE and
IgG1 than EIAP immunized mice (P < 0.01). There was a twofold difference in the number of eosinophils in BALF of EAP mice and EIAP mice (P < 0.01). A similar trend was recorded for
eosinophil peroxidase activity (P < 0.05), indicating the role of proteolytic activity in inducing
inflammation. Further, lung histology revealed increased leucocyte infiltration and airway narrowing, with higher
inflammation scores in the EAP group than in the EIAP group. The lungs of EAP mice showed increased mucus and goblet cell
metaplasia.
Interleukin (IL)-4 and
IL-5 levels were higher in BALF and splenocyte culture supernatant of EAP mice than in EIAP mice (P < 0.05), indicating a T helper 2 response. Proteolytic activity of Epi p 1 plays an important role in inducing allergic
inflammation. The enzymatically inactive form may be investigated for
immunotherapy.