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High affinity nanobodies against the Trypanosome brucei VSG are potent trypanolytic agents that block endocytosis

(2011) PLOS PATHOGENS. 7(6).
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Abstract
The African trypanosome Trypanosoma brucei, which persists within the bloodstream of the mammalian host, has evolved potent mechanisms for immune evasion. Specifically, antigenic variation of the variant-specific surface glycoprotein (VSG) and a highly active endocytosis and recycling of the surface coat efficiently delay killing mediated by anti-VSG antibodies. Consequently, conventional VSG-specific intact immunoglobulins are non-trypanocidal in the absence of complement. In sharp contrast, monovalent antigen-binding fragments, including 15 kDa nanobodies (Nb) derived from camelid heavy-chain antibodies (HCAbs) recognizing variant-specific VSG epitopes, efficiently lyse trypanosomes both in vitro and in vivo. This Nb-mediated lysis is preceded by very rapid immobilisation of the parasites, massive enlargement of the flagellar pocket and major blockade of endocytosis. This is accompanied by severe metabolic perturbations reflected by reduced intracellular ATP-levels and loss of mitochondrial membrane potential, culminating in cell death. Modification of anti-VSG Nbs through site-directed mutagenesis and by reconstitution into HCAbs, combined with unveiling of trypanolytic activity from intact immunoglobulins by papain proteolysis, demonstrates that the trypanolytic activity of Nbs and Fabs requires low molecular weight, monovalency and high affinity. We propose that the generation of low molecular weight VSG-specific trypanolytic nanobodies that impede endocytosis offers a new opportunity for developing novel trypanosomiasis therapeutics. In addition, these data suggest that the antigen-binding domain of an anti-microbial antibody harbours biological functionality that is latent in the intact immunoglobulin and is revealed only upon release of the antigen-binding fragment.
Keywords
VARIANT SURFACE GLYCOPROTEIN, SINGLE-DOMAIN ANTIBODIES, BLOOD-STREAM FORMS, AFRICAN TRYPANOSOMES, ANTIGENIC VARIATION, GLUCOSE-TRANSPORT, IMMUNE-COMPLEXES, ANCHORED PROTEIN, CELL-SURFACE, COMPLEMENT

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Chicago
Stijlemans, Benoit, Guy Caljon, Senthil Kumar A Natesan, Dirk Saerens, Katja Conrath, David Perez-Morga, Jeremy N Skepper, et al. 2011. “High Affinity Nanobodies Against the Trypanosome Brucei VSG Are Potent Trypanolytic Agents That Block Endocytosis.” Plos Pathogens 7 (6).
APA
Stijlemans, Benoit, Caljon, G., Natesan, S. K. A., Saerens, D., Conrath, K., Perez-Morga, D., Skepper, J. N., et al. (2011). High affinity nanobodies against the Trypanosome brucei VSG are potent trypanolytic agents that block endocytosis. PLOS PATHOGENS, 7(6).
Vancouver
1.
Stijlemans B, Caljon G, Natesan SKA, Saerens D, Conrath K, Perez-Morga D, et al. High affinity nanobodies against the Trypanosome brucei VSG are potent trypanolytic agents that block endocytosis. PLOS PATHOGENS. 2011;7(6).
MLA
Stijlemans, Benoit et al. “High Affinity Nanobodies Against the Trypanosome Brucei VSG Are Potent Trypanolytic Agents That Block Endocytosis.” PLOS PATHOGENS 7.6 (2011): n. pag. Print.
@article{8131830,
  abstract     = {The African trypanosome Trypanosoma brucei, which persists within the bloodstream of the mammalian host, has evolved potent mechanisms for immune evasion. Specifically, antigenic variation of the variant-specific surface glycoprotein (VSG) and a highly active endocytosis and recycling of the surface coat efficiently delay killing mediated by anti-VSG antibodies. Consequently, conventional VSG-specific intact immunoglobulins are non-trypanocidal in the absence of complement. In sharp contrast, monovalent antigen-binding fragments, including 15 kDa nanobodies (Nb) derived from camelid heavy-chain antibodies (HCAbs) recognizing variant-specific VSG epitopes, efficiently lyse trypanosomes both in vitro and in vivo. This Nb-mediated lysis is preceded by very rapid immobilisation of the parasites, massive enlargement of the flagellar pocket and major blockade of endocytosis. This is accompanied by severe metabolic perturbations reflected by reduced intracellular ATP-levels and loss of mitochondrial membrane potential, culminating in cell death. Modification of anti-VSG Nbs through site-directed mutagenesis and by reconstitution into HCAbs, combined with unveiling of trypanolytic activity from intact immunoglobulins by papain proteolysis, demonstrates that the trypanolytic activity of Nbs and Fabs requires low molecular weight, monovalency and high affinity. We propose that the generation of low molecular weight VSG-specific trypanolytic nanobodies that impede endocytosis offers a new opportunity for developing novel trypanosomiasis therapeutics. In addition, these data suggest that the antigen-binding domain of an anti-microbial antibody harbours biological functionality that is latent in the intact immunoglobulin and is revealed only upon release of the antigen-binding fragment.},
  articleno    = {e1002072},
  author       = {Stijlemans, Benoit and Caljon, Guy and Natesan, Senthil Kumar A and Saerens, Dirk and Conrath, Katja and Perez-Morga, David and Skepper, Jeremy N and Nikolaou, Alexandros and Brys, Lea and Pays, Etienne and Magez, Stefan and Field, Mark C and De Baetselier, Patrick and Muyldermans, Serge},
  issn         = {1553-7366},
  journal      = {PLOS PATHOGENS},
  language     = {eng},
  number       = {6},
  pages        = {15},
  title        = {High affinity nanobodies against the Trypanosome brucei VSG are potent trypanolytic agents that block endocytosis},
  url          = {http://dx.doi.org/10.1371/journal.ppat.1002072},
  volume       = {7},
  year         = {2011},
}

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