Dr. Scott: Classic virulence

In a discussion on the mechanisms of protection conferred by the Clostridium perfringens type A toxoid vaccine, Broussard confirmed that there is more to be discovered about why and how the vaccine triggers immunity.

Dr. John F. Prescott, University of Guelph, Ontario, who gave a presentation on NE and alpha-toxin during another session at the poultry conference (see article, page 10), expressed surprise that Australian researchers, whose work was widely publicized, were able to induce NE using C. perfringens that lacked the alpha-toxin gene.

“When we vaccinate with just alpha- toxoid — not just secreted protein — we can get excellent protection, so the alpha-toxin has to be involved,” he reported.

Dr. Joan Schrader, the Intervet/ Schering-Plough Animal Health researcher involved in the development of the C. perfringens type A toxoid vaccine, said she had no difficulty “giving other proteins their due,” but emphasized that she and many other researchers had identified alpha-toxin as a primary player. “I think C. perfringens type A toxoid vaccine is efficacious because of that,” she added.

Prescott reminded the audience that alpha-toxin is “the classic clostridial toxin — the First World War gas gangrene toxin. It’s how C. perfringens is recognized.”

A lot of secreted proteins have been discovered that are virulence-associated, but “certainly alpha-toxin is the classic virulence factor of C. perfringens,” he added.

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