HPV-16 VLP vaccine yields consistent, durable antibody response in small trials.('Excellent' Immunogenicity)

BETHESDA, MD. -- Vaccines that contain viruslike particles from human papillomavirus types known to cause cervical cancer have produced consistent, durable antibody responses in several small trials, Doug Lowy, Ph.D., reported.

Viruslike particles (VLPs) resemble the actual virus morphologically but do not induce infection. Once introduced into the body, the particles induce neutralizing antibodies--a response that prevents an infection from taking hold when the subject is later exposed to the natural virus.

If the efficacy and safety of these VLP vaccines are confirmed in larger trials now underway, they may be marketed to the public eventually, he reported at an international conference on malignancies in AIDS and other immunodeficiencies.

Dr. Lowy, chief of the National Cancer Institute's laboratory of cellular oncology in Bethesda, Md., reviewed the results to date of trials for VLP vaccines for human papillomavirus (HPV).

An initial trial tested a vaccine formulation containing VLPs from HPV-16 in 35 volunteers. This vaccine's immunogenicity was "excellent," he said. All the subjects seroconverted within 1 month, and only minor side effects were noted.

Similar results were seen in two subsequent trials sponsored by drug companies. The HPV-16 VLP vaccine failed to induce seroconversion in only 0.3% of cases in these two trials. Serum antibody titers were still high at the 6-month follow-up, indicating that the vaccine's immunogenicity is durable, Dr. Lowy said at the conference, which was sponsored by the National Cancer Institute.

A French research group studied the antibody response at the cervix itself to see whether antibody levels in cervical secretions were comparable to serum antibody levels. They round that cervical antibody levels were consistently about 10% of serum levels.