DAMPs reversibly reduce chlamydial infectivity in a species-specific manner.

<p>HeLa cells were infected with <i>C</i>. <i>pecorum</i> or <i>C</i>. <i>trachomatis</i> serovar E and exposed to cAMP (1 mM), ATP (1 mM), or ADO (50 μM, plus 25 μM EHNA) in incubation medium immediately after infection and incubated for 35 hours (<i>C</i>. <i>pecorum</i>) or 39 hours (<i>C</i>. <i>trachomatis</i>). Infected monolayers were then collected and processed for titration by sub-passage. Number of inclusions was determined and inclusion forming units (IFU) per ml (IFU/ml) was calculated for <i>C</i>. <i>pecorum</i> (A) and <i>C</i>. <i>trachomatis</i> (B) (mean ± SD; *p ≤ 0.05, <i>t</i> test; n = 3). In some wells, incubation medium on cells was replaced with fresh incubation medium with DAMPs for continued exposure or without DAMPs for recovery. These cells were incubated a further 24 hours before processing for titration by sub-passage. Number of inclusions was determined and IFU/ml was calculated for <i>C</i>. <i>pecorum</i> (C) and <i>C</i>. <i>trachomatis</i> (D) (mean ± SD, *p ≤ 0.05, <i>t</i> test; values are derived from duplicate determinations within a representative experiment, and represent results obtained from two independent experiments).