Low-dose doxycycline induces Chlamydia trachomatis persistence in HeLa cells

Area of Science:

• Microbiology
• Cell Biology
• Infectious Diseases

Background:

• Chlamydia trachomatis (CT) can enter a viable but non-replicative persistent state when exposed to stressors like antibiotics.
• Doxycycline is a common antibiotic used to treat CT infections, but its role in inducing CT persistence is unknown.

Purpose of the Study:

• To investigate the ability of doxycycline to induce CT persistence in an in vitro model.
• To compare doxycycline-induced persistence with penicillin-induced persistence.
• To characterize the molecular and cellular effects of doxycycline on CT infection.

Main Methods:

• An in vitro model using HeLa cells infected with 10 different CT strains was established.
• Doxycycline's effects were analyzed by examining aberrant inclusions, chlamydial recovery, gene expression (omcB, euo, Ct110, Ct604, Ct755, HtrA), and cell viability.
• Tetracycline resistance genes were excluded in all strains.

Main Results:

• Low doxycycline concentrations (0.03-0.015 mg/L) induced CT persistence, characterized by smaller, aberrant inclusions and viable but non-dividing reticulate bodies (RBs).
• Chlamydial cytotoxic effects were abolished, and infectious elementary bodies (EBs) were recoverable after drug removal.
• Doxycycline-induced persistence showed decreased expression of the late gene omcB (blocking RB-to-EB conversion) and significant upregulation of the HtrA stress response gene, similar to penicillin G.

Conclusions:

• Doxycycline can induce a persistent state in Chlamydia trachomatis in vitro.
• This study presents a novel cell model for studying doxycycline-induced persistent CT infections.
• The findings highlight the potential for antibiotic pressure to alter Chlamydia infection dynamics.