USU Researchers Develop New Vaccine Candidate to Combat Chlamydia

Novel Approach Preserves Key Proteins, Offering Hope for Preventing Infertility and Blindness Worldwide

November 14, 2024 by Sharon Holland

Researchers at the Uniformed Services University (USU), in collaboration with scientists at Duke University, have developed a promising vaccine candidate to help prevent chlamydia infections-a major cause of infertility and blindness worldwide.

Dr. George Liechti and Dr. Ann Jerse, professors in USU's Department of Microbiology and Immunology, and Dr. Michael Daly, professor in the USU Department of Pathology, with their team of USU researchers and in collaboration with Dr. Andrew Macintyre at Duke University, tested a whole-cell vaccine using patented technology that inactivates Chlamydia while preserving critical proteins on its surface. This approach enabled vaccinated mice to effectively clear chlamydia infections and limited associated tissue damage. The findings were published November 11 in npj Vaccines.

Chlamydia is one of the most common infections in young adults, with the CDC reporting over 1.6 million cases in 2022, primarily affecting women ages 15-24. If untreated, infections can lead to pelvic inflammatory disease (PID), ectopic pregnancies, and infertility. The high infection rates among military personnel, who are in the primary age group at risk, can disrupt unit readiness and require extensive healthcare resources. Preventing these infections would enhance military health and readiness, while globally, a vaccine could support humanitarian missions in regions where Chlamydia trachomatis, which also causes trachoma (a leading cause of blindness), is prevalent.

Despite decades of effort, no vaccine exists for chlamydia. In the 1960s, field trials with whole-cell vaccines in trachoma-endemic areas yielded conflicting results, leading researchers to abandon this approach. Recently, interest has resurfaced, focusing on live-attenuated vaccines, yet USU's research suggests that rethinking inactivation methods might be key to effective whole-cell vaccines.

Building on Daly's work with the extremophile Deinococcus radiodurans, USU scientists used a novel antioxidant, MDP (Manganous Decapeptide ortho-Phosphate), developed by Daly and patented by the Henry M. Jackson Foundation for the Advancement of Military Medicine, to protect the bacterial proteins during inactivation. This addition resulted in significantly higher levels of protective antibodies and immune responses in vaccinated mice. When tested with live chlamydia, MDP-protected vaccinated mice showed faster infection clearance, lower bacterial levels, and less tissue damage compared to traditional vaccines.

The researchers believe these results offer a promising, straightforward approach to advancing a chlamydia vaccine. Liechti, a study lead, remarked, "If you want an effective whole-cell chlamydia vaccine, then you should probably try not to cook, zap, or otherwise damage the surface antigens that it relies on."

This work represents a hopeful step toward preventing chlamydia and its complications for millions worldwide.