Manufacturing and Standardizing Fungal Allergen Products - Greer

J ALLERGY CLIN IMMUNOLVOLUME 113, NUMBER 2Esch 211Reviews andfeature articlesFIG 1. Production outline for fungal source materials. See text for details. QC, Quality control.period, might be important for sporulation and mightaffect allergen production. Because no 2 manufacturersuse the same culture medium or culture conditions, qualitativedifferences between products manufactured bydifferent companies are expected, even when identicalstrains of fungal stock cultures are used.Allergenic materials produced by fungi during cultivationare distributed throughout the culture in the form ofspores, mycelia, and extracellular components secretedinto the growth medium. 8-11 Manufacturers might retainthe cellular (spores and mycelia), the extracellular (culturefiltrate), or the whole culture during harvest. If culturefiltrates are retained, nonantigenic culture media areused. If spores are retained, then they are rendered nonviablethrough chemical or physical means before transferto the manufacturing (extraction) facilities. Variousprocessing steps, including centrifugation, filtration,diafiltration, acetone precipitation, and lyophilization,are used to recover the allergenic materials from fungalcultures. Each manufacturer’s process requirements andspecifications are unique and defined as part of theirproduct and establishment licenses.Fig 2 presents a typical production outline for fungalallergenic extracts. Fungal source materials are reconstitutedfrom the lyophilized state or extracted in an appropriatebuffer to recover the soluble allergenic materials.The allergenic potency of extracts can be influenced by anumber of variables in the extraction procedure. Themost important extraction parameters include the extractionbuffer, pH, ratio, time, and temperature. The mostcommon extraction buffer used by US manufacturers isCoca’s extraction buffer, a slightly alkaline carbonatebuffer developed to maximize protein recovery fromallergen source materials. Manufacturers might add glycerinor phenol as preservatives. Extraction ratios areexpressed as weight/volume or the weight in grams of thesource material extracted to the volume in milliliters ofextraction fluid. For example, a 1:10 wt/vol on a labeldesignates an extract that was prepared with 1 g of sourcematerial for every 10 mL of extraction fluid. Some aller-