An in vitro method for evaluating endotoxic activity using prostaglandin E(2) induction in bovine peripheral blood

Area of Science:

• Veterinary immunology
• Toxicology
• Biotechnology

Background:

• Veterinary vaccines, especially those containing Histophilus somni for cattle, have been linked to severe adverse reactions in Japan.
• Endotoxins are suspected culprits, but current detection methods like the Limulus amebocyte lysate (LAL) test may not fully capture in vivo endotoxic potential.

Purpose of the Study:

• To establish a novel method for assessing endotoxic activity in bovine blood by measuring prostaglandin E2 (PGE2) induction.
• To compare the efficacy of this new method against the LAL test for evaluating endotoxins in veterinary vaccines.

Main Methods:

• Incubation of bovine peripheral blood with standard endotoxin from Escherichia coli.
• Measurement of induced prostaglandin E2 (PGE2) concentrations in culture supernatants after 24 hours.
• Establishing a dose-response curve correlating PGE2 levels with endotoxin concentration (5-5000 ng/ml).

Main Results:

• A linear dose-response relationship was observed between PGE2 concentration and logarithmic endotoxin concentration.
• Histophilus somni exhibited the highest endotoxic activity in cows compared to other tested endotoxins.
• Limulus amebocyte lysate (LAL) test results did not fully reflect the high endotoxic activity of H. somni.

Conclusions:

• The established prostaglandin E2 (PGE2) detection assay in bovine blood offers a valuable tool for evaluating the in vivo endotoxic activities of veterinary vaccines.
• This method may explain the frequent reports of side effects associated with Histophilus somni-containing vaccines, offering a more accurate assessment than the LAL test.