The alpha C protein mediates internalization of group B Streptococcus within human cervical epithelial cells.
Group B Streptococcus (GBS) is the leading cause of bacterial chorioamnionitis and neonatal pneumonia, sepsis, and meningitis. Deletion of the alpha C protein gene (bca) attenuates the virulence of GBS in an animal model; significant survival differences in the first 24 h of infection suggest a pathogenic role for the alpha C protein early in the infection process. We examined the role of alpha C protein in the association between GBS and mucosal surfaces using a human cervical epithelial cell line, ME180. Fluorescent and confocal microscopy and flow cytometry demonstrated that 9-repeat alpha C protein binds to the surface of ME180 cells. Isolated N-terminal region of this protein also binds to these cells and competitively inhibits binding of the full protein. Wild-type GBS strain A909 and the bca-null isogenic mutant JL2053 bound similarly to the surface of ME180 cells. However, A909 entered these cells threefold more. Internalization of A909 was inhibited with 2- and 9-repeat alpha C and with N-terminal region alone but not by repeat region-specific peptide. Translocation across polarized ME180 membranes was fivefold greater for A909 than for JL2053. These findings suggest a role for the alpha C protein in interaction with epithelial surfaces and initiation of infection.
Bolduc
G R
GR
Channing Laboratory, Boston, MA 02115, USA. gbolduc@rics.bwh.harvard.edu
Baron
M J
MJ
Gravekamp
C
C
Lachenauer
C S
CS
Madoff
L C
LC
D000818:Animals; D000954:Antigens, Surface / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D002460:Cell Line; D016764:Cell Polarity; D002584:Cervix Uteri / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D005260:Female; D005434:Flow Cytometry; D005456:Fluorescent Dyes / Q000378:metabolism; D006801:Humans; D011485:Protein Binding; D013290:Streptococcal Infections / Q000378:metabolism*; D013292:Streptococcus agalactiae / Q000378:metabolism*
D000954:Antigens, Surface; D001426:Bacterial Proteins; D005456:Fluorescent Dyes; C077961:alpha C protein, group B streptococci