Abstract
BackgroundChlamydia trachomatis is an intracellular bacteria which consist of three biovariants; trachoma (serovars A-C), urogenital (serovars D-K) and lymphogranuloma venereum (L1-L3), causing a wide spectrum of disease in humans. Monocytes are considered to disseminate this pathogen throughout the body while dendritic cells (DCs) play an important role in mediating immune response against bacterial infection. To determine the fate of C. trachomatis within human peripheral blood monocytes and monocyte-derived DCs, these two sets of immune cells were infected with serovars Ba, D and L2, representative of the three biovariants of C. trachomatis.ResultsOur study revealed that the different serovars primarily infect monocytes and DCs in a comparable fashion, however undergo differential infection outcome, serovar L2 being the only candidate to inflict active infection. Moreover, the C. trachomatis serovars Ba and D become persistent in monocytes while the serovars predominantly suffer degradation within DCs. Effects of persistence gene Indoleamine 2, 3-dioxygenase (IDO) was not clearly evident in the differential infection outcome. The heightened levels of inflammatory cytokines secreted by the chlamydial infection in DCs compared to monocytes seemed to be instrumental for this consequence. The immune genes induced in monocytes and DCs against chlamydial infection involves a different set of Toll-like receptors, indicating that distinct intracellular signalling pathways are adopted for immune response.ConclusionOur results demonstrate that the host pathogen interaction in chlamydia infection is not only serovar specific but manifests cell specific features, inducing separate immune response cascade in monocytes and DCs.
Highlights
Chlamydia trachomatis is an intracellular bacteria which consist of three biovariants; trachoma, urogenital and lymphogranuloma venereum (L1-L3), causing a wide spectrum of disease in humans
HeLa cell monolayers infected with C. trachomatis serovar Ba, D and L2 elementary body (EB) were cultivated at 37°C and 5% CO2 in Earle's MEM containing glutamine, supplemented with 10% fetal calf serum (FCS), 0.1 M nonessential amino acids, and 1 mM sodium pyruvate (PAA Laboratories, Pasching, Germany) along with 1 μg/ml cycloheximide (Sigma-Aldrich, Steinheim, Germany)
Infection of monocyte and monocyte-derived Dendritic cell (DC) Monocytes and the monocyte-derived DCs were infected with C. trachomatis serovars Ba, D and L2 at a multiplicity of infection (MOI) of 3 by centrifugation for 30 min at 400 × g with further incubation for 30 min at 37°C in 5% CO2
Summary
Chlamydia trachomatis is an intracellular bacteria which consist of three biovariants; trachoma (serovars A-C), urogenital (serovars D-K) and lymphogranuloma venereum (L1-L3), causing a wide spectrum of disease in humans. Monocytes are considered to disseminate this pathogen throughout the body while dendritic cells (DCs) play an important role in mediating immune response against bacterial infection. To determine the fate of C. trachomatis within human peripheral blood monocytes and monocyte-derived DCs, these two sets of immune cells were infected with serovars Ba, D and L2, representative of the three biovariants of C. trachomatis. The C. trachomatis infection of monocytes in vitro, have mostly resulted in noncultivable state in which the bacteria metabolically active could not produce active infectious particle when recultured in HeLa cells [23,24]
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