TY - JOUR
T1 - Position of O-acetylation within the capsular repeat unit impacts the biological properties of pneumococcal serotypes 33A and 33F
AU - Spencer, Brady L.
AU - Saad, Jamil S.
AU - Shenoy, Anukul T.
AU - Orihuela, Carlos J.
AU - Nahm, Moon H.
N1 - Funding Information:
This project was supported by National Institutes of Health grant R01AG050607-01 (M.H.N.) and by National Institutes of Health grant R01AI114800 (C.J.O.). The UAB Heflin Center Genomics Core Laboratory was supported by Comprehensive Cancer Center Core grant P30 CA013148 and Center for AIDS Research grant P30 AI027767. We thank B. Beall at the CDC, J. Y. Song at Korea University, and S. Hollingshead and D. Briles at UAB for providing us with bacterial strains. We also thank Rob Burton for his help in purifying the 33X1 polysaccharide, K. A. Geno for advice relating to many aspects of this study, and the UAB Heflin Center Genomics Core Laboratory for performing the sequencing. The University of Alabama at Birmingham has intellectual property rights to some reagents developed in the laboratory of M. H. Nahm, and we are all UAB employees. We declare no additional conflicts of interest.
PY - 2017/7/1
Y1 - 2017/7/1
N2 - Streptococcus pneumoniae (pneumococcus) produces many capsule types that differ in their abilities to evade host immune recognition. To explain these serotypedependent protective capacities, many studies have investigated capsular thickness or the interaction of the capsule with complement proteins, but the effects of small chemical modifications of the capsule on its function have not been studied. One small chemical modification found frequently among pneumococcal capsules is O-acetylation. Pneumococcal serotype 33A has two membrane-bound O-acetyltransferase genes, wciG and wcjE. A 33A wcjE-deficient variant, 33F, occurs naturally and is increasing in prevalence in the wake of widespread conjugate vaccine use, but no wciG-deficient variants have been reported. To study the biological consequence of the loss of O-acetylation, we created wciG-deficient variants in both serotypes 33A and 33F, which we named 33X1 (ΔwciG) and 33X2 (ΔwciG ΔwcjE). Serotypes 33X1 and 33X2 express novel capsule types based on serological and biochemical analyses. We found that loss of WcjE-mediated O-acetylation appears not to affect cell wall shielding, since serotypes 33A and 33F exhibit comparable nonspecific opsonophagocytic killing, biofilm production, and adhesion to nasopharyngeal cells, though serotype 33F survived short-term drying better than serotype 33A. Loss of WciG-mediated O-acetylation in serotypes 33X1 and 33X2, however, resulted in a phenotype resembling that of nonencapsulated strains: increased cell wall accessibility, increased nonspecific opsonophagocytic killing, enhanced biofilm formation, and increased adhesion to nasopharyngeal cells. We conclude that WciG-mediated, but not WcjE-mediated, O-acetylation is important for producing protective capsules in 33A and that small chemical changes to the capsule can drastically affect its biological properties.
AB - Streptococcus pneumoniae (pneumococcus) produces many capsule types that differ in their abilities to evade host immune recognition. To explain these serotypedependent protective capacities, many studies have investigated capsular thickness or the interaction of the capsule with complement proteins, but the effects of small chemical modifications of the capsule on its function have not been studied. One small chemical modification found frequently among pneumococcal capsules is O-acetylation. Pneumococcal serotype 33A has two membrane-bound O-acetyltransferase genes, wciG and wcjE. A 33A wcjE-deficient variant, 33F, occurs naturally and is increasing in prevalence in the wake of widespread conjugate vaccine use, but no wciG-deficient variants have been reported. To study the biological consequence of the loss of O-acetylation, we created wciG-deficient variants in both serotypes 33A and 33F, which we named 33X1 (ΔwciG) and 33X2 (ΔwciG ΔwcjE). Serotypes 33X1 and 33X2 express novel capsule types based on serological and biochemical analyses. We found that loss of WcjE-mediated O-acetylation appears not to affect cell wall shielding, since serotypes 33A and 33F exhibit comparable nonspecific opsonophagocytic killing, biofilm production, and adhesion to nasopharyngeal cells, though serotype 33F survived short-term drying better than serotype 33A. Loss of WciG-mediated O-acetylation in serotypes 33X1 and 33X2, however, resulted in a phenotype resembling that of nonencapsulated strains: increased cell wall accessibility, increased nonspecific opsonophagocytic killing, enhanced biofilm formation, and increased adhesion to nasopharyngeal cells. We conclude that WciG-mediated, but not WcjE-mediated, O-acetylation is important for producing protective capsules in 33A and that small chemical changes to the capsule can drastically affect its biological properties.
KW - Capsular diversity
KW - Capsular polysaccharide
KW - O-acetylation
KW - O-acetyltransferase
KW - Pneumococcal vaccine
KW - Serotype
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UR - http://www.scopus.com/inward/citedby.url?scp=85020894727&partnerID=8YFLogxK
U2 - 10.1128/IAI.00132-17
DO - 10.1128/IAI.00132-17
M3 - Article
C2 - 28438972
AN - SCOPUS:85020894727
VL - 85
JO - Infection and Immunity
JF - Infection and Immunity
SN - 0019-9567
IS - 7
M1 - e00132-17
ER -