Possible Vaccine Target For Chlamydia Identified

The researchers, led by Toni Darville, MD, chief of the Division of Pediatric Infectious Diseases at Children's, identified a plasmid-deficient strain of Chlamydia that, when investigated in an animal model of genital tract infection, failed to cause disease. Plasmids are small molecules of DNA.

"This finding represents a major step forward in our work to eventually develop a vaccine against chlamydial disease," said Dr. Darville, senior author of the study and also a professor of pediatrics and microbiology/immunology at the University of Pittsburgh School of Medicine. "If we can identify plasmid-deficient derivatives of the C. trachomatis strains that infect humans, they would have the potential to serve as a vaccine against this disease."

Dr. Darville is considered one of the world's foremost researchers of Chlamydia trachomatis, a bacterium which is the most frequently reported cause of sexually transmitted disease in the United States. Because symptoms are usually mild or absent, it can damage a woman's reproductive organs and cause irreversible damage, including infertility, before a woman ever recognizes a problem.

In this study, a plasmid-deficient strain derived from Chlamydia muridarum was introduced to mice. The mice became infected but did not develop the trademark signs of chlamydial disease, particularly damage to the oviduct, the tube that carries eggs from the ovaries, according to Catherine M. O'Connell, PhD, a researcher in Dr. Darville's laboratory and first author of the study.

"Not only did the mice not develop oviduct scarring after infection with the plasmid-deficient strain, we also found that the mice previously infected with these strains were protected against oviduct disease when later infected with fully virulent C. muridarum," Dr. O'Connell said.

Nearly 930,000 chlamydial infections were reported to the Centers for Disease Control and Prevention (CDC) in 2004. Under-reporting is substantial because most people with Chlamydia are not aware of their infections and do not seek testing. An estimated 2.8 million Americans are infected with Chlamydia each year, according to the CDC.

Results of their study are published in the Sept. 15 issue of the Journal of Immunology.