Reactivation of Chlamydia muridarum genital tract infection in iNOS knock out mice

The work described here was designed to follow the chlamydial infection in inducible nitric oxide synthase (iNOS) knock out (KO) mice subsequent to culture-apparent resolution of primary infection. The hypothesis is that in the absence of iNOS activity, sterile eradication of chlamydial infection does not occur and viable organisms persist subsequent to culture-apparent resolution.; To monitor Chlamydia muridarum persistence, detection of chlamydial DNA subsequent to infection was assessed both from vaginal swabs and tissues. Polymerase chain reaction (PCR) and PCR followed by Southern blot hybridization of amplicands was used to detect the presence of ompA. Additional quantitative reverse transcriptase-PCR of Chlamydia heat shock proteins (CHSPs) 60 (groEL1, groEL2, groEL3) and major outer membrane protein (MOMP) (ompA) mRNAs were used to confirm any evidence of persistence, because a positive result would suggest persistence of intact, metabolically active cells.; The results indicate that the lack of iNOS activity was bacteristatic, that is, it caused increasing numbers of Chlamydia to enter the persistent stage and sustain a greater degree of pathological damage when compared to the F1 mice. Also, infection can be reactivated at low rates and with low recovery of viable organisms out to 120 days postinfection in iNOS KO but not F1 mice upon immunosuppression. This reactivation provides evidence of true long-term persistence in vivo between chlamydiae and their host. Chlamydial DNA from both iNOS KO and F1 mice could be detected up to day 117 postinfection from cervical-vaginal swabs and up to day 130 postinfection from upper genital track tissue. These findings support using the murine model to monitor Chlamydia persistence and study their pathogenesis in vivo.; Even though the persistence of C. muridarum in this model could not be monitored by MOMP and HSP transcription levels past day 14 postinfection, this experiment was the first known attempt to analyze CHSPs 60 transcriptional activity in vivo. Comparison of mRNA levels among CHSP 60 encoding genes for both iNOS KO and F1 mice tended to support previous findings that these genes are independently and differentially regulated during postinfection, with groEL1 generally higher than either groEL2 or groEL3 during active chlamydial infection.