Endotoxin content of standardized allergen vaccines

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.

The purpose of this study was to quantify the amount of endotoxin contained in standardized allergen vaccines.

The endotoxin content of 14 allergen vaccines was measured by using the Limulus amebocyte lysate (LAL) gel-clot assay. To account for (1,3)-beta-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.

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)-beta-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.

The endotoxin content of standardized allergen vaccines is extremely variable. Interference by proteases and (1,3)-beta-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.