Conformational Preference of Serogroup B Salmonella O Polysaccharide in Presence and Absence of the Monoclonal Antibody Se155-4.

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TitleConformational Preference of Serogroup B Salmonella O Polysaccharide in Presence and Absence of the Monoclonal Antibody Se155-4.
Publication TypeJournal Article
Year of Publication2017
AuthorsYang, M, Simon, R, Mackerell, AD
JournalJ Phys Chem B
Volume121
Issue15
Pagination3412-3423
Date Published2017 Apr 20
ISSN1520-5207
Abstract

Salmonella infection is a major public health problem worldwide. Antibodies directed toward the O polysaccharide (OPS) of S. Typhimurium, a serogroup B nontyphoidal Salmonella serovar, have protected against fatal infection in animal models. The OPS is known to undergo O-acetylation, though the impact of these modifications on antibody binding is poorly understood. Using molecular simulations, we assessed the conformational properties and antigen-antibody interactions of deacetylated and O-acetylated S. Typhimurium OPS when bound by monoclonal anti-OPS IgG Se155-4. Our findings indicate that (i) the α-d-abequose (8) monosaccharide makes important interactions with Se155-4, (ii) the deacetylated form binds to the antibody in two conformations, (iii) the acetyl group at α-l-rhamnose (5) traps the acetylated O-antigenic saccharide in one of those two conformations when bound to the antibody; (iv) the dominant conformation sampled by both unbound saccharides only occurs in the deacetylated-antibody complex; and (v) both unbound saccharides sample the second bound conformation to a small extent (2-4%). These observations provide insights into the conformational preference of an antigenic saccharide when bound to a well-characterized specific monoclonal antibody, and suggest possible important properties of vaccine induced antibodies following immunization with live attenuated and OPS-based subunit vaccines.

DOI10.1021/acs.jpcb.6b08955
Alternate JournalJ Phys Chem B
PubMed ID28423910
PubMed Central IDPMC5407322
Grant ListR01 GM070855 / GM / NIGMS NIH HHS / United States