Peptide Vaccines Raise Concern in Animal Study

By David Douglas

NEW YORK (Reuters Health) – Findings from an animal study indicate that inoculation with so-called peptide vaccines can have lethal consequences.

A peptide vaccine contains small synthetic proteins designed to activate the immune system against a particular virus or other microbe. In particular, they work by stimulating the body’s "killer" T cells to go out and destroy the invading pathogen. Unfortunately, in this study, the T cells appeared to go over-board and killed the animal too.

Synthetic peptides "are considered promising candidates for new-generation vaccines," senior investigator Dr. J. Lindsay Whitton, from Scripps Research Institute, La Jolla, California told Reuters Health. However, "our findings show that peptide vaccines can be harmful, especially if improperly formulated or delivered."

In the study, virus-infected mice that received a peptide vaccine experienced a rapid and severe drop in body temperature. Some of the animals, infected with a virus called LCMV, died within hours of vaccination. As noted, the researchers blamed the deaths not on the virus per se, but on the vigorous and overwhelming killer T cell response.

Despite these findings, the researchers do not believe that peptide vaccines should be abandoned. "Although our results raise a cautionary flag, they should not be taken as an indication that the peptide vaccine approach is fatally flawed," Whitton emphasized.

SOURCE: Journal of Clinical Investigation, February 2006.