Damage/Danger Associated Molecular Patterns (DAMPs) Modulate Chlamydia pecorum and C. trachomatis Serovar E Inclusion Development In Vitro

Persistence, more recently termed the chlamydial stress response, is a viable but non27 infectious state constituting a divergence from the characteristic chlamydial biphasic 28 developmental cycle. Damage/danger associated molecular patterns (DAMPs) are normal 29 intracellular components or metabolites that, when released from cells, signal cellular 30 damage/lysis. Purine metabolite DAMPs, including extracellular ATP and adenosine, inhibit 31 chlamydial development in a species-specific manner. Viral co-infection has been shown to 32 reversibly abrogate Chlamydia inclusion development, suggesting persistence/chlamydial 33 stress. Because viral infection can cause host cell DAMP release, we hypothesized DAMPs 34 may influence chlamydial development. Therefore, we examined the effect of extracellular 35 ATP, adenosine, and cyclic AMP exposure, at 0 and 14 hours post infection, on C. pecorum 36 and C. trachomatis serovar E development. In the absence of de novo host protein synthesis, 37 exposure to DAMPs immediately post or at 14 hours post infection reduced inclusion size; 38 however, the effect was less robust upon 14 hours post infection exposure. Additionally, upon 39 exposure to DAMPs immediately post infection, bacteria per inclusion and subsequent 40 infectivity were reduced in both Chlamydia species. These effects were reversible, and C. 41 pecorum exhibited more pronounced recovery from DAMP exposure. Aberrant bodies, typical 42 in virus-induced chlamydial persistence, were absent upon DAMP exposure. In the presence of 43 de novo host protein synthesis, exposure to DAMPs immediately post infection reduced 44 inclusion size, but only variably modulated chlamydial infectivity. Because chlamydial infection 45 and other infections may increase local DAMP concentrations, DAMPs may influence Chlamydia infection in vivo, particularly in the context of poly-microbial infections