The Role of Gap Junction Mediated Antigen Transport in Immunopathogenesis of Mucosal Intracellular Pathogens

We have shown previously using mouse models that Chlamydia-specific CD8⁺ T-cells do not significantly affect bacterial clearance but cause pathological sequelae such as fluid-filled oviduct dilatation (hydrosalpinx), which also occurs in humans.  We recently found that chlamydial antigens can be detected in uninfected cells neighboring infected genital epithelial cells. Based on this, we hypothesized that gap junction mediated antigen transport (GMAT) via channels formed by connexin (Cx) proteins, predominantly Cx43 expressed on oviduct epithelium, plays a role in activation of antigen-specific CD8⁺ T-cells.  Using Cre-Lox technology, we generated mice (Foxj1Cre-Cx43flox mice) with a conditional deficiency of Cx43 only in ciliated columnar epithelial cells specifically the oviduct, but not uterine horn, epithelium in the genital tract.  Resolution of chlamydial infection, splenic antigen-specific total cellular cytokine response and serum antibody response were comparable between Foxj1Cre-Cx43flox and WT mice.  However, the frequency of Chlamydia-specific CD8⁺ T-cells in spleens of Foxj1Cre-Cx43flox mice was significantly reduced compared to WT mice.   Moreover, the incidence and severity of oviduct pathology in Foxj1Cre-Cx43flox mice was significantly reduced compared to WT animals, whereas uterine horn pathology was comparable on day 80 after intravaginal chlamydial infection. Furthermore, HeLa cells engineered to express Cx43, not those without, efficaciously transferred Ova_257-264 peptide to co-cultured mouse APC, which subsequently activated CD8⁺ T-cells derived from Ova primed OT-1 mice.  These results suggest that efficient transfer of microbial peptides at mucosal surfaces from infected to uninfected cells via Cx43 GMAT plays an important role in activation of pathogen-specific CD8⁺ T-cells that induce immunopathology.