Clinical

Lyophilization does not eradicate viruses from connective tissue allografts

Last Updated: 2004-04-02 17:09:30 -0400 (Reuters Health)

By Karla Gale

NEW YORK (Reuters Health) - Lyophilization does not inactivate retroviruses from bone and connective tissue, according to investigators at Michigan State University in East Lansing, suggesting that this technique does not improve the safety of tissue used for allografts.

Despite rigorous screening, HIV and hepatitis C transmission has occurred after transplantation of infected bone and tendon. "There has been a long-held belief based on one article published in 1985 that freeze-drying may inhibit or inactivate a virus, suggesting that it would provide an extra measure of safety," senior investigator Dr. Steven P. Arnoczky told Reuters Health.

As reported online in the American Journal of Sports Medicine, Dr. Arnoczky's group obtained patellar tendons and cortical bone from cats systemically infected with feline leukemia virus. Samples were freeze-dried, providing tissue with less than 2% residual moisture.

Using "an extremely sensitive, in vitro challenge system," they compared the infectivity of freeze-dried and fresh frozen tissue in feline embryonic fibroblast cell cultures. Media from all samples were positive for virus, regardless of which type of tissue was used.

His group's findings are logical, if you consider that vaccines remain effective after lyophilization, Dr. Arnoczky said, "but ours was the first well-controlled experimental model" to provide conclusive evidence.

He noted that bone can be demineralized to inactivate virus without affecting its biological properties, "but the problem is in soft tissues, such as tendons, ligament and cartilage. You can't do what is necessary to sterilize them without altering their mechanical properties."

He emphasized that with current screening methods, the likelihood of implanting infected tissues is minute. But screening could miss an emerging infectious disease, "and we don't know the effects of processing on prion-infected tissue," he added.

Am J Sports Med 2004;32.