Endotoxin content of standardized allergen vaccines☆☆☆★

Abstract 

Background: Endotoxin is a ubiquitous and potent proinflammatory agent. Previous limited studies suggest that it is pres-ent in allergen vaccines and that this could affect the safety and efficacy of allergen immunotherapy. The endotoxin content of standardized allergen vaccines is unknown. Objective: The purpose of this study was to quantify the amount of endotoxin contained in standardized allergen vaccines. Methods: The endotoxin content of 14 allergen vaccines was measured by using the Limulus amebocyte lysate (LAL) gel-clot assay. To account for (1,3)-β-d-glucan and protease interference, vaccines were selectively depleted of endotoxin and then retested with the gel-clot assay. Proteases were also heat-inactivated in selected vaccines. Fifty-eight lots of vaccines were tested, including at least two manufacturers per vaccine. Results: The endotoxin content of the 58 vaccines ranged from undetectable to 34,000 EU/mL. Cat pelt (12,735 EU/mL; range, 5177 to 33,805) had significantly more endotoxin activity than cat hair (2883 EU/mL; range, 1 to 16,962), and Dermatophagoides farinae extracts (4619 EU/mL; range, 849 to 8485) had more than Dermatophagoides pteronyssinus (11 EU/mL; range, 1 to 34). Grass (160 EU/mL; range, 3 to 1561) and ragweed pollen (341 EU/mL; range, 8 to 1697) vaccines contained less endotoxin. (1,3)-β-d-glucan interference was significant (>10%) only in three ragweed vaccines and two grass vaccines. Heat inactivation had no effect. There were considerable differences in endotoxin content of the same vaccines made by different manufacturers. Conclusions: The endotoxin content of standardized allergen vaccines is extremely variable. Interference by proteases and (1,3)-β-d-glucans is minimal. The effects of the high levels of endotoxin in some vaccines on the immunomodulatory changes associated with allergen immunotherapy require further study.

Keywords:  Endotoxin, lipopolysaccharide, allergen, allergen vac-cine, allergen immunotherapy, Limulus amebocyte lysate, endotox-in-neutralizing protein, standardization, protease

Abbreviations:  ENP: , Endotoxin-neutralizing protein, EU: , Endotoxin unit, LAL: , Limulus amebocyte lysate, LPS: , Lipopolysaccharide