The Plasmid-Encoded pGP3 Promotes Evasion of Acidic Barriers in Both Stomach and Vagina.

Although is a human genital tract pathogen, chlamydial organisms have frequently been detected in both vaginal and rectal swab samples of animals and humans. The plasmid-encoded pGP3, a genital tract virulence factor, is essential for to colonize the mouse gastrointestinal tract. However, intracolon inoculation to bypass the gastric barrier rescued the colonization ability of a pGP3-deficient mutant, suggesting that pGP3 is required for to reach but not to colonize the large intestine. The pGP3-deficient mutant was rapidly cleared in the stomach and was 100-fold more susceptible to gastric killing. In mice genetically deficient in gastrin, a key regulator for gastric acid production, or pharmacologically treated with a proton pump inhibitor, the ability of pGP3-deficient to colonize the gastrointestinal tract was rescued. The pGP3-dependent resistance was further recapitulated with treatments with HCl, pepsin, or sarkosyl. In the genital tract, deficiency in pGP3 significantly reduced survival in the mouse vagina and increased susceptibility to vaginal killing by ∼8 times. The pGP3-deficient was more susceptible to lactic acid killing, and the pGP3 deficiency also significantly increased susceptibility to lactic acid. The above-described observations together suggest that may have acquired the plasmid-encoded pGP3 to overcome the gastric barrier during its adaptation to the gastrointestinal tract and the pGP3-dependent resistance may enable chlamydial evasion of the female lower genital tract barrier during sexual transmission.