The Molecular Biology of Chlamydiae as Exemplar of Bacterial Pathogenesis in the Rheumatic Diseases

As with tuberculosis and smallpox, the rheumatic diseases have a long history with the human species, and like the former, many clinical examples of the latter have an infectious origin. Among those, one common attribute is the elicitation of often severe inflammation in the synovial context by the infecting agent. In this initial chapter, we examine the molecular details involved in the genesis of an inflammatory arthritis that can serve in many ways as an exemplar of infectious bacterial origin for several arthritides. Genital Chlamydia trachomatis infections can elicit an inflammatory arthritis in some individuals, and one recent study indicated that ocular (trachoma), not genital, strains of the organism are present in the synovial tissues of patients with the disease. This observation suggests an explanation for the small proportion of genitally infected patients who develop Chlamydia-induced arthritis. Other studies summarized in this chapter provide new and important insight into the chlamydial gene products that elicit the synovial inflammatory response during both active and quiescent disease. While more study will be required to complete the understanding of that complex process of host–pathogen interaction, newly developed experimental methods and approaches for study of the process should enable identification of new therapeutic targets, and possibly strategies for prevention of the disease altogether. We suggest areas which should prove productive in the latter endeavors.