An enzymatically inactivated hemoglobinase from Necator americanus induces neutralizing antibodies against multiple hookworm species and protects dogs against heterologous hookworm infection

FASEB J. 2009 Sep;23(9):3007-19. doi: 10.1096/fj.09-131433. Epub 2009 Apr 20.


Hookworms digest hemoglobin from erythrocytes via a proteolytic cascade that begins with the aspartic protease, APR-1. Ac-APR-1 from the dog hookworm, Ancylostoma caninum, protects dogs against hookworm infection via antibodies that neutralize enzymatic activity and interrupt blood-feeding. Toward developing a human hookworm vaccine, we expressed both wild-type (Na-APR-1(wt)) and mutant (Na-APR-1(mut)-mutagenesis of the catalytic aspartic acids) forms of Na-APR-1 from the human hookworm, Necator americanus. Refolded Na-APR-1(wt) was catalytically active, and Na-APR-1(mut) was catalytically inactive but still bound substrates. Vaccination of canines with Na-APR-1(mut) and heterologous challenge with A. caninum resulted in significantly reduced parasite egg burdens (P=0.034) and weight loss (P=0.022). Vaccinated dogs also had less gut pathology, fewer adult worms, and reduced blood loss compared to controls but these did not reach statistical significance. Vaccination with Na-APR-1(mut) induced antibodies that bound the native enzyme in the parasite gut and neutralized enzymatic activity of Na-APR-1(wt) and APR-1 orthologues from three other hookworm species that infect humans. IgG1 against Na-APR-1(mut) was the most prominently detected antibody in sera from people resident in high-transmission areas for N. americanus, indicating that natural boosting may occur in exposed humans. Na-APR-1(mut) is now a lead antigen for the development of an antihematophagy vaccine for human hookworm disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ancylostomatoidea / immunology
  • Animals
  • Antibodies, Helminth / administration & dosage
  • Antibodies, Helminth / therapeutic use*
  • Cysteine Endopeptidases / immunology*
  • Dogs
  • Hookworm Infections / prevention & control*
  • Hookworm Infections / therapy
  • Humans
  • Intestines / parasitology
  • Necator americanus / immunology*
  • Treatment Outcome
  • Vaccination / methods
  • Vaccines / pharmacology
  • Vaccines / therapeutic use
  • Weight Loss


  • Antibodies, Helminth
  • Vaccines
  • Cysteine Endopeptidases