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Degree Name

PhD (Doctor of Philosophy)

Program

Biomedical Sciences

Date of Award

12-2005

Committee Chair or Co-Chairs

Robert V. Schoborg

Committee Members

Jane E. Raulston, John J. Laffan, Jonathan P. Moorman, Priscilla B. Wyrick, W. Scott Champney

Abstract

Clinical and epidemiological studies have shown that multiple infection with HSV-2 and Chlamydia trachomatis occurs in vivo. We hypothesize that (i) HSV-2 co-infection of C. trachomatis infected cervical epithelial cells induces chlamydial persistence; (ii) productive HSV-2 replication is required for induction of persistence in C. trachomatis; (iii) co-infection with C. trachomatis and HSV-2 alters accumulation of immuno-modulatory molecules in infected cells. To test these hypotheses, a cell culture model of co-infection was established in HeLa cells. Transmission electron microscopic (TEM) analyses demonstrated aberrant chlamydial morphology in co-infected cells, which was apparent by 10 hours and prominent by 20 hours post HSV-2 infection. Moreover, co-infection reduced infectivity of progeny chlamydiae. These observations indicate chlamydial persistence and are consistent with certain historical 'markers' of persistence previously described. Since chlamydial persistence was being established, we were interested in unraveling the mechanism of induction. To determine whether HSV-2 replication was necessary, cyclohexamide (Cx), a eukaryotic protein synthesis inhibitor, was used. Cx inhibits host cell and viral protein synthesis by >95% and productive viral replication by >90%. Development of chlamydial persistence was observed in the presence of Cx. To analyze whether events during attachment and entry are sufficient for induction of chlamydial persistence, UV-inactivated, replication incompetent HSV-2 (HSV-2uv) was used. HSV-2uv is capable of attachment and entry but incapable of productive replication. Chlamydial persistence also developed during co-infection with C. trachomatis and HSV-2uv. Both of these observations suggest that an early event/s in HSV-2 replication, most probably occurring during HSV-2 attachment and entry, is sufficient for induction of chalmydial persistence. These observations also suggest that productive viral replication is not required for the induction of chlamydial persistence. Accumulation of chlamydial major outer membrane (MOMP) was decreased whereas pro-inflammatory chlamydial heat shock protein 60 (cHSP60) was increased in co-infected cells compared to C. trachomatis singly-infected cells. Among the cytokines looked at, an elevation in the levels of IL-6 was observed in HSV-2 infected and co-infected samples. Release of chlamydial antigens during chlamydial persistence increases inflammation and disease severity in vivo. Therefore, co-infection might increase immunopathology compared to that observed in C. trachomatis singly-infected individuals.

Document Type

Dissertation - Campus Only

Copyright

Copyright by the authors.

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