Thermodynamic Analysis of the Binding of 2F5 (Fab and Immunoglobulin G Forms) to Its gp41 Epitope Reveals a Strong Influence of the Immunoglobulin Fc Region on Affinity*

Background: Little is known regarding the thermodynamics of binding of the broadly neutralizing anti-HIV-1 mAb 2F5 to its gp41 epitope. Results: Isothermal titration calorimetry reveals strong differences between IgG and Fab. Conclusion: Residues flanking the core epitope and the immunoglobulin Fc region contribute strongly to affinity by allosteric mechanisms. Significance: The results may help to develop new therapeutics and/or vaccines against HIV and to understanding Ag-Ab recognition. Immunotherapies and vaccines based on the induction of broadly neutralizing monoclonal antibodies (bNAbs) have become outstanding strategies against HIV-1. Diverse bNAbs recognizing different regions of the HIV-1 envelope have been identified and extensively studied. However, there is little information about the thermodynamics of binding of these bNAbs and their epitopes. We used isothermal titration calorimetry to characterize thermodynamically the interactions between bNAb 2F5 (in both the IgG and Fab forms) and its functional and core epitope peptides. We found that these interactions are enthalpically driven and opposed by a negative entropy change. The highest affinity was found for 2F5 IgG for its functional epitope, indicating that additional interactions involving residues flanking the core epitope contribute strongly to higher affinity. In addition, the strong influence of the Fc region on the binding affinity suggests long-range allosteric effects within IgG. Our results provide useful information for developing new therapeutics against HIV-1 and, in a broader scope, contribute to a better understanding of antigen-antibody recognition.

• Publication year

  2013

• Venue

  Journal of Biological Chemistry

• Publication date

  2013-12-03

• Fields of study

  Biology, Medicine, Chemistry

• Identifiers
  DOI 10.1074/jbc.C113.524439PMID 24302742PMCID PMC3887187
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar, PubMed

• No claims are published for this paper.

• No concepts are published for this paper.

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