Transgenic parasites stably expressing full-length Plasmodium falciparum circumsporozoite protein as a model for vaccine down-selection in mice using sterile protection as an endpoint

Clin Vaccine Immunol. 2013 Jun;20(6):803-10. doi: 10.1128/CVI.00066-13. Epub 2013 Mar 27.

Abstract

Circumsporozoite protein (CSP) of Plasmodium falciparum is a protective human malaria vaccine candidate. There is an urgent need for models that can rapidly down-select novel CSP-based vaccine candidates. In the present study, the mouse-mosquito transmission cycle of a transgenic Plasmodium berghei malaria parasite stably expressing a functional full-length P. falciparum CSP was optimized to consistently produce infective sporozoites for protection studies. A minimal sporozoite challenge dose was established, and protection was defined as the absence of blood-stage parasites 14 days after intravenous challenge. The specificity of protection was confirmed by vaccinating mice with multiple CSP constructs of differing lengths and compositions. Constructs that induced high NANP repeat-specific antibody titers in enzyme-linked immunosorbent assays were protective, and the degree of protection was dependent on the antigen dose. There was a positive correlation between antibody avidity and protection. The antibodies in the protected mice recognized the native CSP on the parasites and showed sporozoite invasion inhibitory activity. Passive transfer of anti-CSP antibodies into naive mice also induced protection. Thus, we have demonstrated the utility of a mouse efficacy model to down-select human CSP-based vaccine formulations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Protozoan / blood
  • Culicidae
  • Disease Models, Animal
  • Enzyme-Linked Immunosorbent Assay
  • Malaria / prevention & control*
  • Malaria Vaccines / genetics
  • Malaria Vaccines / immunology*
  • Malaria Vaccines / isolation & purification
  • Mice
  • Mice, Inbred C57BL
  • Parasitemia / prevention & control*
  • Plasmodium berghei / genetics
  • Plasmodium berghei / immunology
  • Plasmodium falciparum / genetics
  • Plasmodium falciparum / immunology
  • Protozoan Proteins / genetics
  • Protozoan Proteins / immunology*
  • Vaccination / methods*
  • Vaccines, Synthetic / genetics
  • Vaccines, Synthetic / immunology
  • Vaccines, Synthetic / isolation & purification

Substances

  • Antibodies, Protozoan
  • Malaria Vaccines
  • Protozoan Proteins
  • Vaccines, Synthetic
  • circumsporozoite protein, Protozoan