B2 - Prof. Dr. Eberhard Straube
Modulation of Apoptosis and Antigen Presentation of Host Cells by Chlamydia

Abstract:
Apoptosis is one of the host strategies for limitation of intracellular infection with viral, bacterial, and parasitic pathogens. These pathogens might be successfully replicate and survive within the host cell, when they modulate or block at least one of the signal pathways of apoptosis. For Chlamydia species this pathogenicity mechanism is discussed controversial. Whereas several experiments give evidences for apoptosis induction by Chlamydia others support the probability of apoptosis inhibition. Our experience with the cultivation of Chlamydia pneumoniae gives some evidence for apoptosis inhibition due to Chlamydia pneumoniae since the inclusion bodies produce a huge amount of bacterial cells without impairment of the host cell vitality.
Since antigen presentation may trigger one of the apoptosis pathways the influence of Chlamydia on expression or degradation of essential factors of the MHC class I antigen presentation pathway should be investigated. Factors as TAP, tapasin, and gp 96, responsible for the translocation of antigenic peptides into the ER and their binding to MHC class I / ß2M complexes will be estimated by RT-PCR and immunoblots as well.
On the other hand the recognition of Chlamydia infected cells by CD8+ T lymphocytes should be investigated as well. The generation of Chlamydia-reactive CD8+ T cell clones from peripheral blood of patients with a Chlamydia infection would be a prerequisite. In investigation on synovial cells from patients with reactive arthritis we were several times successful in establishing Chlamydia-reactive T cell clones. The reactive CD8+ T cell clones will be measured using IFN-γ ELIOSPOT assay. The autologous fibroblasts established from skin biopsies will be infected with Chlamydia and serve as target cells to the reactive CD8+ T cell clones. T cell activity will be measured by IFN-γ ELISA, cytolysis, and apoptosis assays as well.
Our preliminary investigation of the FAS/FASL dependent apoptosis pathway by mean of microarray technology, functional protein analysis, and suppression of protein synthesis by Doxycyclin leads to a Chlamydia specific protein, which might block this pathway. Since this protein showed immunological cross reactions to CrmA a Caspase-8 inhibitor protein of cow pox virus the monitoring of expression should be accessible for methods like confocal laser scanning microscopy.

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