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Infection and Immunity, January 2008, p. 179-188, Vol. 76, No. 1
0019-9567/08/$08.00+0 doi:10.1128/IAI.00837-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
L-Ficolin/Mannose-Binding Lectin-Associated Serine Protease Complexes Bind to Group B Streptococci Primarily through N-Acetylneuraminic Acid of Capsular Polysaccharide and Activate the Complement Pathway
Youko Aoyagi,1
Elisabeth E. Adderson,2
Craig E. Rubens,3
John F. Bohnsack,4
Jin G. Min,5
Misao Matsushita,5
Teizo Fujita,6
Yoshiyuki Okuwaki,1 and
Shinji Takahashi1*
Division of Microbiology, Joshi-Eiyoh (Kagawa Nutrition) University, Sakado, Japan,1 Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee,2 Department of Pediatrics, Children's Hospital and Regional Medical Center, University of Washington, Seattle, Washington,3 Department of Pediatrics, University of Utah Health Sciences Center, Salt Lake City, Utah,4 Department of Applied Biochemistry, Tokai University, Hiratsuka, Japan,5 Department of Immunology, Fukushima Medical University, Fukushima, Japan6
Received 18 June 2007/ Returned for modification 31 July 2007/ Accepted 8 October 2007
Group B streptococci (GBS) are the most common cause of neonatal sepsis and meningitis. Most infants who are colonized with GBS at birth do not develop invasive disease, although many of these uninfected infants lack protective levels of capsular polysaccharide (CPS)-specific antibody. The lectin pathway of complement is a potential mechanism for initiating opsonization of GBS with CPS-specific antibody-deficient serum. In this study, we determined whether mannose-binding lectin (MBL)/MBL-associated serine protease (MASP) complexes and L-ficolin/MASP complexes bind to different strains of GBS to activate the lectin pathway, and we identified the molecules recognized by lectins on the GBS surface. We found that MBL did not bind to any GBS examined, whereas L-ficolin bound to GBS cells of many serotypes. L-ficolin binding to GBS cells correlated with the CPS content in serotypes Ib, III (restriction digestion pattern types III-2 and III-3), and V but not with the group B-specific polysaccharide (GBPS) content or with the lipoteichoic acid (LTA) content. L-ficolin bound to purified CPS and GBPS in a concentration-dependent manner but not to purified LTA. All strains to which L-ficolin/MASP complexes bound consumed C4. When N-acetylneuraminic acid (NeuNAc) was selectively removed from GBS cells by treatment with neuraminidase, the reduction in L-ficolin binding was correlated with the amount of NeuNAc removed. Additionally, L-ficolin was able to bind to wild-type strains but was able to bind only weakly to unencapsulated mutants and a mutant strain in which the CPS lacks NeuNAc. We concluded that L-ficolin/MASP complexes bind to GBS primarily through an interaction with NeuNAc of CPS.
* Corresponding author. Mailing address: Division of Microbiology, Joshi-Eiyoh University, Sakado, Saitama 350-0288, Japan. Phone and fax: 81 49 282 3716. E-mail: tshinji{at}eiyo.ac.jp
Published ahead of print on 15 October 2007.
Infection and Immunity, January 2008, p. 179-188, Vol. 76, No. 1
0019-9567/08/$08.00+0 doi:10.1128/IAI.00837-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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