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Infect. Immun., Jul 1996, 2467-2473, Vol 64, No. 7
P Valenti-Weigand, P Benkel, M Rohde and GS Chhatwal
The mouse macrophage-like cell line J774 was used to analyze opsonin-
independent entry and survival of group B streptococci (GBS). Efficient
entry of GBS in J774 cells occurred within 5 min postinfection, and
streptococci persisted intracellularly without loss of viability for at
least 8 h. At 24 h postinfection, 30% of the total intracellular GBS was
recovered from macrophages. Inhibition studies using different biochemical
modulators of cellular functions showed that bacterial entry seemed to
involve nonglycosylated J774 surface structures different from known
receptors such as fibronectin-binding integrins. Internalization of GBS by
J774 cells occurred by a microfilament- dependent phagocytosis-like process
also involving participation of receptor-mediated endocytosis. Prior
opsonization of GBS with human serum containing anti-GBS antibodies did not
affect bacterial entry but significantly reduced the intracellular survival
of GBS. Transmission electron microscopic analysis confirmed these findings
and demonstrated that both opsonized and nonopsonized bacteria were
contained within phagosomes during the whole infection period. Transmission
electron microscopy further revealed that decreased intracellular survival
rates of opsonized GBS appeared to be due to increased lysosomal activities
of the macrophages. These results suggest that in the absence of opsonins,
GBS are able to enter and persist efficiently in macrophages by evading
intracellular antibacterial activities commonly associated with
opsonin-mediated uptake.
Copyright © 1996, American Society for Microbiology
Entry and intracellular survival of group B streptococci in J774 macrophages
Department of Microbiology, GBF-National Research Centre for Biotechnology, Braunschweig, Germany.
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