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Cell Microbiol. 2018 Dec;20(12):e12948. doi: 10.1111/cmi.12948. Epub 2018 Sep 23.

Humanised monoclonal antibodies neutralise pertussis toxin by receptor blockade and reduced retrograde trafficking.

Author information

1
Department of Biochemistry, The University of Texas at Austin, Austin, Texas.
2
Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas.
3
Department of Cell and Molecular Biology, The University of Texas at Austin, Austin, Texas.

Abstract

Pertussis toxin (PTx) is a major protective antigen produced by Bordetella pertussis that is included in all current acellular vaccines. Of several well-characterized monoclonal antibodies binding this toxin, the humanised hu1B7 and hu11E6 antibodies are highly protective in multiple in vitro and in vivo assays. In this study, we determine the molecular mechanisms of protection mediated by these antibodies. Neither antibody directly binds the B. pertussis bacterium nor supports antibody-dependent complement cytotoxicity. Both antibodies, either individually or as a cocktail, form multivalent complexes with soluble PTx that bind the FcγRIIb receptor more tightly than antibody alone, suggesting that the antibodies may accelerate PTx clearance via immune complex formation. However, a receptor binding assay and cellular imaging indicate that the main mechanism used by hu11E6 is competitive inhibition of PTx binding to its cellular receptor. In contrast, the main hu1B7 neutralising mechanism appears to be inhibition of PTx internalisation and retrograde trafficking. We assessed the effects of hu1B7 on PTx retrograde trafficking in CHO-K1 cells using quantitative immunofluorescence microscopy. In the absence of hu1B7 or after incubation with an isotype control antibody, PTx colocalizes to organelles in a manner consistent with retrograde transport. However, after preincubation with hu1B7, PTx appears restricted to the membrane surface with colocalization to organelles associated with retrograde transport significantly reduced. Together, these data support a model whereby hu11E6 and hu1B7 interfere with PTx receptor binding and PTx retrograde trafficking, respectively.

KEYWORDS:

Bordetella; antibody engineering; neutralisation; passive immunotherapy; toxins

PMID:
30152075
PMCID:
PMC6519169
DOI:
10.1111/cmi.12948
[Indexed for MEDLINE]
Free PMC Article

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