ULTRASTRUCTURAL AND MOLECULAR ANALYSES OF THE PERSISTENCE OF CHLAMYDIA-TRACHOMATIS (SEROVAR-K) IN HUMAN MONOCYTES

Previous studies have suggested that monocytes may play a role in the dissemination of Chlamydia trachomatis, and in establishment of persis tent infection with this bacterium. Infection of cultured human periph eral blood monocytes with C. trachomatis serovar K produced persistent , non-productive infection. Transmission electron microscopy of such i nfected cultures revealed single or multiple Chlamydia in monocyte inc lusions over a culture period of 10 days. Those inclusions were aberra nt, and normal reticulate bodies within the inclusions were not observ ed. Immunoelectron microscopy showed the chlamydial major outer membra ne protein and lipopolysaccharide to be associated with the bacterial plasma membrane. Lipopolysaccharide was also identified in the monocyt e cytoplasm. Molecular analyses of primary chlamydial rRNA transcripts demonstrated that the organism is viable and metabolically active wit hin monocyte inclusions. However, attempts to overcome chlamydial grow th arrest by incubation of Chlamydia-infected monocytes with tryptopha n, and antibodies against alpha interferon, gamma interferon, or tumor necrosis factor, were all ineffective, suggesting that known mechanis ms of growth inhibition do not hold in human monocytes. These observat ions indicate that infection of human peripheral blood monocytes with C. trachomatis may be involved in the genesis/maintenance of extra-uro genital inflammation, since non-culturable, metabolically active bacte ria persist in those cells. (C) 1997 Academic Press Limited.