Redox potential and survival of virulent Treponema pallidum under microaerophilic conditions

Effect of four serum components on survival of Treponema pallidum and its attachment to rabbit cells in vitro

Transferrin and, to a lesser extent, insulin were two components of serum that enhanced the survival of Treponema pallidum in microaerophilic, acellular medium. These two components also enhanced the attachment of T pallidum to baby rabbit genital organ (BRGO) cells in both aerobic and microaerophilic tissue culture systems. Growth hormone and epidermal growth factor marginally enhanced the attachment of T pallidum to BRGO cells.

Susceptibility of Treponema pallidum to the toxic products of oxygen reduction and the non-treponemal nature of its catalase

We examined the sensitivity of Treponema pallidum (Nichols strain) to toxic products of oxygen reduction. T pallidum was sensitive to hydrogen peroxide at concentrations similar to those to which obligate anaerobes are sensitive. Accelerated death of T pallidum occurred at hydrogen peroxide concentrations below 50 mumol/l. Agents protective against hydrogen peroxide and the hydroxyl free radical (catalase, peroxidase, and mannitol) significantly enhanced treponemal survival in vitro under all three conditions of aerobiosis tested--that is, air, 3% oxygen, and 3% oxygen in conjunction with a reduced medium. Superoxide dismutase (which provides protection against superoxide radicals) did not enhance treponemal survival in normal media. When superoxide radicals were generated in the medium by means of a xanthine and xanthine oxidase system, however, the enzyme did protect T pallidum. A possible toxic involvement of singlet oxygen was also indicated by enhanced treponemal survival in air in the presence of histidine. Extracts of T pallidum from infected rabbit testes showed catalase activity which, on polyacrylamide gel electrophoresis, had the same relative mobility as purified rabbit catalase. The treponemal catalase activity was neutralised by anti rabbit catalase antiserum (raised in guinea pigs). This confirmed that the catalase was of rabbit origin and not an endogenous enzyme of T pallidum. We discuss the relation of these results to the obligate parasitism of T pallidum.

Effect of syphilitic rabbit sera taken at different periods after infection on treponemal motility, treponemal attachment to mammalian cells in vitro, and treponemal infection in rabbits

The time course of antibody synthesis during syphilis was studied in experimentally infected rabbits. A rapid antibody response was seen; the rabbits became positive in both the rapid plasma reagin (RPR) test and Treponema pallidum haemagglutination assay (TPHA) by nine days after infection. Treponemal immobilising antibodies were also seen as early as nine days after infection. Antibody inhibition of treponemal attachment to baby rabbit genital organ (BRGO) cells in culture occurred with immune sera taken 30 days after infection but not earlier. When T pallidum was mixed with immune syphilitic rabbit sera taken at different stages of the infection and used to infect normal rabbits the rabbits became partially resistant to T pallidum only when the treponemes were mixed with sera taken at least 30 days after syphilitic infection. This appearance correlated well with the development of antibodies which blocked attachment of T pallidum to host cells. These antibodies may be involved in the resistance to reinfection which develops in syphilis as the disease progresses.

A monoclonal IgM smooth muscle antibody reactive with fibroblast stress fibres produced by immunization with Treponema pallidum

A monoclonal IgM smooth muscle antibody secreted by a hybrid (MMI-1) of mouse plasmacytoma NS-1 with spleen cells from mouse immunized with Treponema pallidum was detected by indirect immunofluorescence tests on frozen tissue sections and on acetone fixed monolayers of rat and human fibroblasts. The antibody did not react with acetone fixed smears of T. pallidum but reacted with smooth muscle fibres and with striations of skeletal and cardiac muscle. In non-muscle cells, the antibody stained liver in a 'polygonal' pattern, thymus with accentuated staining of the thymic medulla, renal glomeruli and the brush border and peritubular fibrils of renal tubules. In fibroblast monolayers, the antibody stained stress fibres in an interrupted pattern. Immunoblotting with muscle proteins and the antibody showed labelling of a 100K molecule. The cellular distribution of the mouse monoclonal antibody is similar to that obtained with anti-actin antibody suggesting that the corresponding antigen may be an actin binding protein.

Factors affecting the attachment of Treponema pallidum to mammalian cells in vitro

Attachment of Treponema pallidum (Nichols) to mammalian cells is probably the first step in the pathogenesis of syphilis. It may also be important for the multiplication of T pallidum in vitro. When factors affecting the attachment of T pallidum to mammalian cells in vitro were studied significantly greater numbers of treponemes were found to attach to baby rabbit genital organ (BRGO) cells than to five other mammalian cell lines. When attached to BRGO cells T pallidum survived longer in vitro than unattached treponemes. Eagle's minimal essential medium was superior to three other culture media in increasing attachment and maintaining the survival of treponemes. Dithiothreitol (0.25-1.0 mmol/l) had no effect on the attachment of T pallidum to BRGO cells. Anaerobic conditions were superior to microaerophilic conditions, and the latter were superior to aerobic conditions for the attachment and survival of T pallidum to BRGO cells. Within the range of concentrations tested the number of treponemes attached to the BRGO cells was directly dependent on the concentrations of viable treponemes in the inoculum. Greater numbers of treponemes attached to actively metabolising BRGO cells than to quiescent or slowly growing cells.

Effects of anaerobic and microaerophilic conditions of extraction and incubation on the survival of Treponema pallidum in vitro

Treponema pallidum extracted from infected rabbit testes under anaerobic conditions survived longer in vitro than those extracted under aerobic conditions. Anaerobically extracted treponemes were incubated anaerobically for 0, 12, 24, 36, or 48 hours and then exposed to microaerophilic conditions (3% oxygen) for further incubation. Treponemes transferred to microaerophilic conditions after 36 or 48 hours' anaerobic incubation maintained significantly greater viability compared with those kept under constant microaerophilic conditions, although there was no difference after 12 or 24 hours. T pallidum incubated under constant anaerobic conditions, however, usually maintained greater viability than those kept under constant microaerophilic conditions. These results suggest that T pallidum is sensitive to oxygen toxicity both during initial extraction from orchitic rabbit testes and subsequent incubation in vitro. In the latter case, it can be partially protected by a period of anaerobic incubation in vitro, before exposure to microaerophilic conditions.