Degree Name

PhD (Doctor of Philosophy)

Program

Biomedical Sciences

Date of Award

May 1992

Abstract

Chlamydia trachomatis (CT) is the most prevalent sexually-transmitted infection in the United States. It has been suggested that CT infections can become latent. This has not been substantiated. CT persistence was examined at the molecular and cellular level in vitro and in vivo. Penicillin treatment of CT in vitro results in abnormal inclusions and reduced recovery of infectious CT. Penicillin did not inhibit initial stages of infection, but did downregulate CT rRNA levels after 25 hours post-inoculation (p.i.). DNA amplification was employed to differentiate between a resolved infection and a persistent one. Utilizing a primer pair that amplified a 144 bp fragment in the CT MOMP gene, CT-persistently-infected McCoy cells maintained in penicillin medium were examined. Though undetectable by other assay methods, these cells harbored the CT genome for 18 passages. Removal of penicillin 1, 3 or 6 passages p.i. and subsequent cultivation in permissive medium resulted in "recovery" to productive infection. Removal of penicillin at later passages resulted in low level inclusion formation but no infectious progeny. Penicillin treatment in vitro resulted in a persistent infection undetectable by most methods. Female C$\sb3$H/HeNCRL mice were inoculated with CT intrauterinely and intravaginally in two separate experiments. In one, CT infection was established in untreated and Depo-Provera (DP)-pretreated mice. DP pretreatment enhanced vaginal shedding of infectious CT. A negative vaginal culture did not correlate with elimination of CT from the upper tract. In the second, penicillin therapy did not halt vaginal CT shedding, however, it reduced frequency of recurrent vaginal CT shedding. To examine reactivation, culture-negative mice ($\geq$2 successive vaginal cultures) were injected with cortisone-acetate (CA) or DP; mice from same subpopulation injected with saline served as controls. Transient vaginal CT shedding was reactivated in penicillin-treated mice (14% CA-injected), and in unmedicated mice (28% CA-injected, 33% DP-injected). Saline injection did not reactivate vaginal CT shedding. At time of sacrifice (16 or 22 weeks p.i.) no infectious CT was detected in upper tract tissues, although tissue damage was observed in most mice (70-71%). It is unknown if these mice harbored a persistent infection undetectable by culture. Further work utilizing molecular techniques is needed to resolve this question.

Document Type

Dissertation - Open Access

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