Researchers advance tests of ‘promising’ chlamydia vaccine

A research team in Canada believes it has a good shot at creating the first-ever successful vaccine against chlamydia in humans.

Although human trials are still a few years away, researchers say the results of early animal studies are “very promising.”

Chlamydia is the most common sexually transmitted infection in North America, according to the Centers for Disease Control and Prevention (CDC). The World Health Organization estimates that it affects roughly 131 million individuals worldwide-particularly in developing countries. Although chlamydia infections are easily treated with antibiotics, in many cases-70% of women and 50% of men-there are often no symptoms to alert an individual to infection, and the infection can progress to cause serious health problems, such as pelvic inflammatory disease and infertility.

Efforts to produce and effective vaccine against chlamydia have been unsuccessful, and any vaccine would have to provide protection against several distinctly different strains.

In the new study, “Immunization with chlamydial type III secretion antigens reduces vaginal shedding and prevents fallopian tube pathology following live C. muridarum challenge” published in Vaccine, researchers at the Michael G. DeGroote Institute for Infectious Disease Research at McMaster University in Canada identified a novel antigen-BD584-which may be effective against the most common form of chlamydia-Chlamydia trachomatis.

BD584 is made up of three T3SS proteins from C. trachomatis. In laboratory studies, BD584 elicited an antibody response that inhibited C. trachomatis infection in vitro, according to the report. In mice infected vaginally with C. muridarum, the vaccine was able to reduce chlamydial shedding by 95% and hydrosalpinx-a symptom of C. trachomatis infection where serous fluids block the fallopian tubes-by almost 88%. Researchers say the drop in hydrosalpinx rates from 80% to 10% in mice models suggests that the antigen may be effective in reducing infertility in those infected with chlamydia.

The vaccine would be administered intranasally and could be administered with minimal training, according to the research team.

James Mahony, PhD, FCCM, FAAM, professor of pathology and molecular medicine, assistant dean of the Medical Sciences Program, and head of service for the Regional Virology Laboratory at McMaster University, led the study and says the identification of an antigen is the first step in successful vaccine development.

“Our vaccine targets the type III secretion mechanism of chlamydia, which is essential for infection of cells. Inhibition of type III secretion blocks infection and prevents the complications such as tubal factor infertility,” Mahoney told Medical Economics in an email. “Our vaccine candidate will protect against all strains of Chlamydia trachomatis which cause genital tract and eye infections. The effectiveness is due in part to the choice of the three chlamydial proteins that we have fused together as a single fusion protein and to the intranasal route of immunization used to stimulate mucosal immunity at distant mucosal sites including the vagina.”

While the research team said the vaccine appears to be very promising in mice, it now must be tested in other animal models before it can move to human trials. Mahoney says trials in a second animal model are underway, and human trials could follow in two to three years.