Studies on the deterioration of antigen E in extracts of Ambrosia elatior.

Five per cent (w/v) extracts of defatted Ambrosia elatior pollen were prepared in bicarbonate-buffered saline (Coca's extract) and Coca's extract with 50% glycerol (Gly-Coca's extract). Sterile extracts were stored in untreated glassware and glassware coated with silicone. Stock extracts were diluted in phosphate-buffered saline (PBS) and stored at 5 +/- 3 degrees C. Extracts 1:20, 1:40, and 1:400 were assayed at approximately 6-wk intervals for antigen E. Quantitative determinations were made by modified double diffusion in agarose gels using known standards of antigen E for comparison. Results from the first year of this 3-yr study show no significant reduction in 1:20 Gly-Coca's extracts and a highly significant reduction of antigen E in 1:20 Coca's extracts. Further analysis of variance indicates significant reduction in all 1:40 and 1:400 extracts. Differences in the initial extracting solvents did not significantly affect these more dilute extracts. No significant differences were observed in the untreated and silicone-coated glassware. In terms of per cent antigen E reduction, 1:20 Gly-Coca's showed negligible reduction and Coco's at 1:20 declined nearly 50% in antigen E content. Extracts stored at 1:40 retained only 40% of the original antigen E content, while diluted extracts stored at 1:400 retained only 35% of the initial antigen E after 1 yr of storage at 5 +/- 3 degrees C.