Vibrio cholerae ghosts elicit the production of soluble immunostimulatory factors and prevent development of Chlamydia infection (INM3P.408)

Infections by the obligate intracellular pathogen Chlamydia trachomatis cause infertility in women of childbearing age. Currently infections caused by the pathogen are treated with antimicrobial therapy. Bacterial ghosts offer a cost-effective, long-term, protective therapy as vaccine delivery vectors. In the present study we tested the hypothesis that factors contained in culture supernatant exhibit anti-chlamydial activity. THP-1 monocytes were differentiated into macrophages (Mdm) by incubating with phorbol myristate acetate (PMA). Activated Mdm were pulsed with Vibrio cholerae ghosts (VCG) for 24 h, followed by the addition of murine splenocytes for an additional 48 h. After 72 h the supernatant was collected and assayed for cytokine concentration. Samples presented observable levels of immunostimulatory factors necessary for containing or clearing infections with chlamydia. Following these assay results, Chlamydia pneumonia (MoPn) elementary bodies (EBs) were suspended in VCG-pulsed THP-1 Mdm supernatant (conditioned media) and used to culture HeLa cells. As a positive control, MoPn was suspended in Earle’s MEM - a medium used for HeLa cell culture. Immunostimulatory factors contained in the conditioned media prevented the development of Chlamydia infection forming units (5.87%) vs. our positive control (94.1%). These results indicate that immunostimulatory factors induced by VCG confer protective immunity against the development cycle of Chlamydia.

The effect of extracellularly applied divalent cations on cytosolic Ca2+ in murine leydig cells: evidence for a Ca2+-sensing receptor

1. The effect of extracellularly applied divalent cations upon cytosolic Ca2+ levels ([Ca2+]) was investigated in fura-2-loaded mouse Leydig (TM3) cells. 2. The extracellular application of Ca2+ (2.5-15 mM) or Ni2+ (0.5-5 mM) elicited concentration-dependent elevations in cytosolic [Ca2+] that were followed by decays to baseline levels. Extracellular Mg2+ (0.8-15 mM) failed to influence cytosolic [Ca2+]. 3. Conditioning applications of Ca2+ (2.5-10 mM), Mg2+ (2.5-15 mM) or Ni2+ (0.5-5 mM) all attenuated the cytosolic Ca2+ response to a subsequent test application of 5 mM [Ni2+]. 4. The amplitude of Ni2+-induced cytosolic Ca2+ signals remained constant in low-Ca2+ solutions. Such findings suggest a participation of Ca2+ release from intracellular stores. In parallel, depletion of Ca2+ stores by either ionomycin (5 microM, in low-Ca2+ solutions) or thapsigargin (4 microM) abolished or attenuated Ni2+-induced Ca2+ transients. 5. Ionomycin (5 microM) elevated cytosolic [Ca2+] in Ca2+-free solutions even after prior Ni2+ application, indicating the presence of Ni2+-insensitive stores. 6. Caffeine (250 and 500 microM) elevated cytosolic [Ca2+] and attenuated Ni2+-induced Ca2+ release. Furthermore, TM3 cells stained intensely with a specific anti-ryanodine receptor antiserum, Ab34. These findings suggest that Ca2+ release is regulated by ryanodine receptors. 7. Both membrane depolarization and hyperpolarization, brought about by changes in extracellular [K+] ([K+]e) in the presence of valinomycin (5 microM), altered the waveform of the Ni2+-induced cytosolic Ca2+ signal. Hyperpolarization, in addition, diminished the response magnitude. Such voltage-induced response modulation localizes the regulatory events to the Leydig cell plasma membrane. 8. We propose the existence of a cell surface divalent cation (Ca2+) receptor in Leydig cells, the activation of which triggers Ca2+ fluxes through ryanodine receptors.