Chlamydia trachomatis Hijacks Host Cell Programs to Establish Persistence

Chlamydia trachomatis (C. trachomatis) is a major global pathogen responsible for bacterial sexually transmitted infections. The majority of infections are asymptomatic and may persist for prolonged periods; consequently, clinically silent transmission and upper genital tract complications represent a persistent public health burden. The biological basis of this clinical phenotype resides in the bacterium's capacity to sustain infection despite host immune pressure. However, the molecular mechanisms underpinning this process remain unclear. Accumulating evidence indicates that, upon invasion, C. trachomatis reprograms host cell signaling through T3SS effector proteins such as TarP. It subsequently establishes a replicative niche that is sequestered from cytoplasmic immune receptors by a network of inclusion membrane proteins and, through effectors such as Cdu1, CpoS, and GarD, modulates the NF-κB and cGAS-STING signaling, as well as IFN-γ-mediated clearance of inclusions. Under IFN-γ-induced nutrient restriction, the bacterium can enter a reversible, low-proliferative state characterized by division arrest and downregulation of developmental programs. This state does not represent immune silencing per se; rather, alterations in its surface molecular composition concurrently influence both host recognition and immune responses. However, most of these mechanisms have been inferred from in vitro cellular models. The bacterial strains and host systems employed across studies are heterogeneous, and systematic evidence is lacking regarding whether effector protein networks remain functional under steady-state conditions. Accordingly, extrapolation of these findings to human infection should be undertaken with caution. This review critically appraises the evidence and unresolved controversies surrounding these mechanisms, advances a research framework centered on the persistent state, and contends that deciphering the dynamic interplay between host immune pressure and bacterial adaptive responses is a prerequisite for identifying intervention targets and optimizing vaccine strategies.