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Infection and Immunity, July 2000, p. 4180-4188, Vol. 68, No. 7
Department of Pediatrics, Sophia Children's
Hospital, Erasmus University, Rotterdam,1 and
Laboratory of Organic Analytical Chemistry, National Institute
of Public Health and the Environment,
Bilthoven,4 The Netherlands; Division of
Infection and Immunity, University of Glasgow, Glasgow,
Scotland2; and Cell Biology and Imaging
Section, National Institute for Biological Standards and Control,
Hertsfordshire, United Kingdom3
Received 28 February 2000/Returned for modification 24 March
2000/Accepted 24 April 2000
Surface-exposed proteins often play an important role in the
interaction between pathogenic bacteria and their host. We isolated a
pool of hydrophobic, surface-associated proteins of Streptococcus pneumoniae. The opsonophagocytic activity of hyperimmune serum raised against this protein fraction was high and species specific. Moreover, the opsonophagocytic activity was independent of the capsular
type and chromosomal genotype of the pneumococcus. Since the
opsonophagocytic activity is presumed to correlate with in vivo
protection, these data indicate that the protein fraction has the
potential to elicit species-specific immune protection with
cross-protection against various pneumococcal strains. Individual proteins in the extract were purified by two-dimensional gel
electrophoresis. Antibodies raised against three distinct proteins
contributed to the opsonophagocytic activity of the serum. The proteins
were identified by mass spectrometry and N-terminal amino acid
sequencing. Two proteins were the previously characterized pneumococcal
surface protein A and oligopeptide-binding lipoprotein AmiA. The third protein was the recently identified putative proteinase maturation protein A (PpmA), which showed homology to members of the family of
peptidyl-prolyl cis/trans isomerases. Immunoelectron
microscopy demonstrated that PpmA was associated with the pneumococcal
surface. In addition, PpmA was shown to elicit species-specific
opsonophagocytic antibodies that were cross-reactive with various
pneumococcal strains. This antibody cross-reactivity was in line with
the limited sequence variation of ppmA. The importance of
PpmA in pneumococcal pathogenesis was demonstrated in a mouse pneumonia
model. Pneumococcal ppmA-deficient mutants showed reduced
virulence. The properties of PpmA reported here indicate its potential
for inclusion in multicomponent protein vaccines.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
The Putative Proteinase Maturation Protein A of
Streptococcus pneumoniae Is a Conserved Surface Protein with
Potential To Elicit Protective Immune Responses
*
Corresponding author. Mailing address: Laboratory of
Pediatrics / room Ee 1500, Erasmus University Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands. Phone: 31-10-4088224. Fax: 31-10-4089486. E-mail: hermans{at}kgk.fgg.eur.nl.
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