Details

Autor(en) / Beteiligte

• Larabee, Jason L.
• Krumholz, Aleze
• Hunt, Jonathan J.
• Lanis, Jordi M.
• Ballard, Jimmy D.

Titel

Exposure of Neutralizing Epitopes in the Carboxyl-terminal Domain of TcdB Is Altered by a Proximal Hypervariable Region

Ist Teil von

• The Journal of biological chemistry, 2015-03, Vol.290 (11), p.6975-6985

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2015

Quelle

MEDLINE

Beschreibungen/Notizen

• The sequence, activity, and antigenicity of TcdB varies between different strains of Clostridium difficile. As a result, ribotype-specific forms of TcdB exhibit different toxicities and are not strongly cross-neutralized. Using a combination of biochemical and immunological approaches, we compared two important variants of TcdB (TcdB012 and TcdB027) to identify the mechanisms through which sequence differences alter epitopes and activity of the toxin. These analyses led to the discovery of a critical variation in the 1753–1851 (B2′) region of TcdB, which affects the exposure of neutralizing epitopes in the toxin. Sequence comparisons found that the B2′ region exhibits only 77% identity and is the most variable sequence between the two forms of TcdB. A combination of biochemical, analytical, and mutagenesis experiments revealed that the B2′ region promotes protein-protein interactions. These interactions appear to shield neutralizing epitopes that would otherwise be exposed in the toxin, an event found to be less prominent in TcdB012 due to sequence differences in the 1773–1780 and 1791–1798 regions of the B2′ domain. When the carboxyl-terminal domains of TcdB012 and TcdB027 are swapped, neutralization experiments suggest that the amino terminus of TcdB interacts with the B2′ region and impacts the exposure of neutralizing epitopes in the carboxyl terminus. Collectively, these data suggest that variations in the B2′ region affect protein-protein interactions within TcdB and that these interactions influence the exposure of neutralizing epitopes. Background: TcdB from 027 strains is not as sensitive to antibody neutralization as TcdB from 012 strains, although neutralizing epitopes are present on both forms. Results: Sequence alterations in strain-specific TcdB influence intramolecular protein-protein interactions and exposure of neutralizing epitopes. Conclusion: Our work uncovers a mechanism used by TcdB to shield neutralizing epitopes. Significance: This study demonstrates how strain-specific TcdB can avoid antibody targeting.