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Infection and Immunity, May 1999, p. 2327-2333, Vol. 67, No. 5
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Relationship between Cell Surface Carbohydrates and Intrastrain Variation on Opsonophagocytosis of Streptococcus pneumoniae

Jean O. Kim,1 Sandra Romero-Steiner,2 Uffe B. Skov Sørensen,3 Jens Blom,4 M. Carvalho,2 S. Barnard,2 George Carlone,2 and Jeffrey N. Weiser1,*

Departments of Pediatrics and Microbiology, Children's Hospital of Philadelphia and University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 191041; Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 303332; and Department of Medical Microbiology and Immunology, University of Aarhus, DK-8000 Aarhus,3 and Department of Molecular Cell Biology, Statens Seruminstitut, DK-2300 Copenhagen S,4 Denmark

Received 17 December 1998/Returned for modification 19 February 1999/Accepted 26 February 1999

Streptococcus pneumoniae undergoes spontaneous phase variation between a transparent and an opaque colony phenotype, the latter being more virulent in a murine model of sepsis. Opaque pneumococci have previously been shown to express lower amounts of C polysaccharide (cell wall teichoic acid) and in this study were shown to have a higher content of capsular polysaccharide by immunoelectron microscopy. This report then examined the relationship between expression of these two cell surface carbohydrate structures and their relative contribution to the increased virulence of opaque variants. Comparison of genetically related strains showed that the differential content of capsular polysaccharide did not affect the amount of teichoic acid as measured by a capture enzyme-linked immunosorbent assay (ELISA). In contrast, when the teichoic acid structure was altered by replacing choline in the growth medium with structural analogs, the quantity of capsular polysaccharide as measured by a capture ELISA was decreased, demonstrating a linkage in the expression of the two surface carbohydrate structures. A standardized assay was used to assess the relative contribution of cell surface carbohydrates to opsonophagocytosis. The opaque variants required 1.2- to 30-fold more immune human serum to achieve 50% opsonophagocytic killing than did related transparent variants (types 6B and 9V). The opsonophagocytic titer was proportional to the quantity of capsular polysaccharide rather than teichoic acid. The major factor in binding of the opsonin, C-reactive protein (CRP), was also the amount of capsular polysaccharide rather than the teichoic acid ligand. Only for the transparent variant (type 6B), which bound more CRP, was there enhanced opsonophagocytic killing in the presence of this serum protein. Increased expression of capsular polysaccharide, therefore, appeared to be the major factor in the decreased opsonophagocytic killing of opaque pneumococci.


* Corresponding author. Mailing address: 301B Johnson Pavilion, University of Pennsylvania, Philadelphia, PA 19104-6076. Phone: (215) 573-3511. Fax: (215) 898-9557. E-mail: weiser{at}mail.med.upenn.edu.


Infection and Immunity, May 1999, p. 2327-2333, Vol. 67, No. 5
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.



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