Site of Initial Chlamydia Exposure May Dictate Patient Outcomes

Investigators from UT Health San Antonio have found that the site of first chlamydia exposure can make all the difference when it comes to patient outcomes.

Initial exposure to chlamydia in the gut was shown to result in robust transmucosal immunity, with the lungs and genital tract protected against the disease. However, if an individual’s initial exposure to the bacteria occurs within the genital tract, it can result in a more severe disease pattern that promotes further disease, according to the official press release.

“This research emphasizes the pre-exposure of chlamydia to the gastrointestinal tract as a vaccine,” Guangming Zhong, MD, PhD, professor in the Joe R. & Teresa Lozano Long School of Medicine at UT Health San Antonio stressed in the press release.

For their study, published in the journal Infection and Immunity, Dr. Zhong and his team used a mouse model to better understand chlamydia transmission.

“Purified C. muridarum EBs were used to inoculate 6- to 7-week-old female mice intragastrically (as an immunization route), intrarectally, or intravaginally…We started with CBA/J mice since they are highly susceptible to C. muridarum induction of hydrosalpinx. After observing the transmucosal protection induced by GI tract C. muridarum, we switched to C57BL/6J mice in order to investigate the mechanisms,” authors of the study write. “Inoculation of viable C. muridarum bacteria intragastrically was used to mimic oral immunization. Following each inoculation, both vaginal and rectal swab specimens were periodically taken to monitor viable C. muridarum colonization or organs/tissues were harvested (after the mice were sacrificed) to titrate viable organisms as described previously.”

The investigators found that “mice preinoculated intragastrically with Chlamydia muridarum became highly resistant to subsequent infection in the genital tract, resulting in the prevention of pathology in the upper genital tract,” the authors write. “The long-lasting colonization with C. muridarum was restricted to the gastrointestinal tract and was nonpathogenic to either gastrointestinal or extra-gastrointestinal tissues.”

Based on the study’s findings, Dr. Zhong wants to take the idea of an oral chlamydia vaccine further, by exploring the idea of adding chlamydia as a probiotic for the gut.

“GI tract C. muridarum may be considered an orally deliverable replicating vaccine. First, the oral uptake of attenuated live bacterial or viral vaccines has been well accepted,” the authors write. “Although the reversion of orally administered attenuated vaccines into pathogens has caused some concerns, our studies have shown that C. muridarum behaves like a normal commensal species in the mouse gut.”

The authors stated that clinical studies will be needed to explore if C. trachomatis will also behave like a normal commensal species in the human gut and if it would be capable of inducing transmucosal protection within the human GI tract.

The authors also note that doxycycline can be used to clear C. muridarum from the gastrointestinal tract without affecting the induced transmucosal immunity, which thus, “provides a safeguard measure for preventing any potential pathogenicity,” the authors write. However, optimal conditions for clearing out C. trachomatis in the human GI tract still need further exploration.