Parachlamydia acanthamoeba Enters and Multiplies within Human Macrophages and Induces Their Apoptosis

AUTOR(ES)

Greub, Gilbert

FONTE

American Society for Microbiology

RESUMO

Parachlamydia acanthamoeba is an obligately intracellular bacterium that naturally infects free-living amoebae. It is a potential human pathogen and may survive in human macrophages. We studied P. acanthamoeba entry into, and multiplication within, human monocyte-derived macrophages. After 8 h of incubation, 80% of macrophages were infected with a mean of 3.8 P. acanthamoeba organisms per cell. Electron microscopy demonstrated that parachlamydiae were in an intracellular vacuole. After infection with living organisms, the number of parachlamydiae per macrophage increased 4 times from day 0 to day 4, whereas heat-inactivated parachlamydiae were eliminated during the same period. Quantitative PCR confirmed that P. acanthamoeba replicates within macrophages. Transcriptional activity of P. acanthamoeba was detected by reverse transcription-PCR targeting the gene encoding ADP-ATP translocase (tlc). P. acanthamoeba exerted a cytopathic effect on macrophages. When macrophages were infected with living bacteria, their number decreased significantly from day 0 to day 4 due to apoptosis, as shown by annexin-V binding and electron microscopy. This study shows that P. acanthamoeba enters and multiplies within human macrophages before inducing their apoptosis.

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