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Replacements in the exposed loop of the T15 antibody VH CDR2 affect carrier recognition of PC-containing pathogens
1Department of Molecular Microbiology and Immunology, Oregon Health Sciences University, Portland 97201, USA.
Abstract:
A panel of mutant antibodies of the phosphocholine (PC)-binding antibody, T15, was tested for binding to PC-protein, Streptococcus pneumoniae, Trichinella spiralis and Ascaris suum. Relative to wildtype T15, all the mutant antibodies showed differential recognition of the panel of PC-associated antigens. These mutant antibodies contain amino acid replacements in the CDR2 region of the heavy chain variable region, indicating the importance of CDR2 in recognition of carrier determinants. A model of T15 is shown that illustrates the strategic placement of mutations that could allow interaction with determinants associated with PC. A direct implication of this finding is that the T15 antibody combining site accommodates structures larger than phosphocholine and that recognition of associated carrier determinants could be a significant force in shaping the immune response to PC-containing pathogens.
Insights
Mutant antibodies targeting phosphocholine (PC) revealed that the T15 antibody site binds larger structures than PC alone. This suggests carrier determinants significantly influence immune responses to PC-containing pathogens.
Area of Science:
- Immunology
- Structural Biology
- Microbial Pathogenesis
Background:
- The T15 antibody is a model system for studying phosphocholine (PC) recognition.
- Understanding antibody-antigen interactions is crucial for vaccine development and treating infections.
Purpose of the Study:
- To investigate the role of specific antibody regions in recognizing PC and associated antigens.
- To explore the structural basis for T15 antibody binding to PC and microbial determinants.
Main Methods:
- Generated mutant antibodies with amino acid replacements in the CDR2 region of the T15 heavy chain.
- Tested binding affinities of wildtype and mutant T15 antibodies to PC-protein, Streptococcus pneumoniae, Trichinella spiralis, and Ascaris suum.
Main Results:
- All mutant T15 antibodies exhibited differential binding to PC-associated antigens compared to wildtype.
- Mutations in the CDR2 region significantly altered antigen recognition, highlighting its importance.
- Structural modeling suggested the T15 antibody combining site accommodates structures larger than PC.
Conclusions:
- The CDR2 region of the T15 antibody is critical for recognizing carrier determinants associated with PC.
- The T15 antibody's binding site accommodates epitopes larger than PC, implying broader recognition capabilities.
- Recognition of carrier determinants is a significant factor shaping immune responses to PC-bearing pathogens.