Maize is a major crop grown in India and is consumed in various forms. Although many patients report allergic symptoms to maize but a systematic study on its allergenic roperties has been lacking. The investigation was aimed at to find out maize sensitization in Indian patients of respiratory allergy and Characterize allergens of clinical significance by clinico immunologic evaluation. .
Patients attending allergy clinic for respiratory allergy were screened for Maize sensitization by SPT and by allergen specific IgE by ELISA. The IgE binding epitopes were identified by Immunoblot after transferring SDS- PAGE separated proteins on to NC membrane. The 28kd major allergen was identified in Indian patients and was further subjected to in situ trypsin digestion and MALDI-TOF to determine the molecular masses of peptides and sequence similarity. Cross reactivity of maize seed extract was evaluated with extracts of pea nut, rice, and unrelated Putranjiva roxburghiipollen extract by Immunoblot inhibition studies.
Antigen extracted from maize seeds contained 4.5±0.7 mg/ml protein .The extract was subjected to SDS protein profile with 12 protein bands in molecular weight range of 152 – 10 kD. Five protein fractions of 68, 38, 25, 14 & 10 kD are recorded as stable under 60 min of simulated gastric fluid (SGF) digestion assay. Using clinically maize positive patient sera and significantly raised maize specific IgE titer and IgE binding activity of 28 kD protein smear is recorded. Cross Inhibition studies suggested cross reactivity reactivity of maize with rice, on account of the complete disappearance of observed 28 kD immunoreactive protein smear. However biochemical characterization of the smear corresponds to two protein bands of 25kD and 19 kD on 1D gel which on MS spectra are observed with hypothetical molecular weight of 14.3 kD and 11.6 kD, sharing sequence homology greater than 41% with un annotated rice seed proteins in database.
Two important immuno reactive protein fractions of maize have been identified which are speculated to be belonging to major family of endosperm proteins “zeins