Comparative transcriptomic profiling of human conjunctival epithelial cells and macrophages in response to Chlamydia trachomatis genovars A and B in early- and mid-infection cycles.

Chlamydia trachomatis (Ct), an obligate intracellular bacterium, is the primary infectious cause of blindness through trachoma. Ct undergoes a unique biphasic developmental cycle between infectious elementary bodies and replicating reticulate bodies, manipulating host cells via secreted effector proteins. Whilst previous studies have characterised host-pathogen interactions including transcriptomes of urogenital Ct genovars E and L2, limited studies exist on ocular Ct genovars. This study examined transcriptomic responses of human conjunctival epithelial (HCjE) cells and PMA-differentiated THP-1 macrophages to infection with ocular Ct strains A/2497 or B/Tunis864 (live or heat-inactivated) at 4 and 24 hours post-infection (hpi). Transcriptomic profiling was performed using RNA sequencing, with differential gene expression analysis. Pathway enrichment analyses were performed to identify strain-specific and cell type-specific transcriptional signatures. HCjE cells exhibited progressive transcriptional activation, with differentially expressed genes (DEGs) increasing from 4 to 24 hpi (144 to 259), whilst THP-1 macrophages showed temporal attenuation (391 to 154). B/Tunis864 consistently elicited stronger responses than A/2497 in HCjE cells at both time points (152 vs. 54 DEGs at 4 hpi; 259 vs. 83 at 24 hpi). Conversely, THP-1 macrophages showed stronger responses to A/2497 than B/Tunis864 at both time points (599 vs. 376 DEGs at 4 hpi; 166 vs. 114 at 24 hpi). HCjE cells demonstrated markedly higher proportions of strain-specific DEGs and pathways compared to macrophages. B/Tunis864 infection in HCjE cells induced pronounced interferon (IFN)-stimulated gene signatures, particularly at 24 hpi. This study revealed contrasting temporal and strain-specific patterns: THP-1 macrophages showed peak-then-decline, strain-invariant responses, whilst HCjE cells exhibited progressive activation with predominantly strain-specific programmes. Enhanced IFN-stimulated gene and inflammatory pathway activation by B/Tunis864 in HCjE cells may provide molecular insights into genovar B-associated trachoma severity.