Attenuated PfSPZ Vaccine induces strain-transcending T cells and durable protection against heterologous controlled human malaria infection

Proc Natl Acad Sci U S A. 2017 Mar 7;114(10):2711-2716. doi: 10.1073/pnas.1615324114. Epub 2017 Feb 21.


A live-attenuated malaria vaccine, Plasmodium falciparum sporozoite vaccine (PfSPZ Vaccine), confers sterile protection against controlled human malaria infection (CHMI) with Plasmodium falciparum (Pf) parasites homologous to the vaccine strain up to 14 mo after final vaccination. No injectable malaria vaccine has demonstrated long-term protection against CHMI using Pf parasites heterologous to the vaccine strain. Here, we conducted an open-label trial with PfSPZ Vaccine at a dose of 9.0 × 105 PfSPZ administered i.v. three times at 8-wk intervals to 15 malaria-naive adults. After CHMI with homologous Pf parasites 19 wk after final immunization, nine (64%) of 14 (95% CI, 35-87%) vaccinated volunteers remained without parasitemia compared with none of six nonvaccinated controls (P = 0.012). Of the nine nonparasitemic subjects, six underwent repeat CHMI with heterologous Pf7G8 parasites 33 wk after final immunization. Five (83%) of six (95% CI, 36-99%) remained without parasitemia compared with none of six nonvaccinated controls. PfSPZ-specific T-cell and antibody responses were detected in all vaccine recipients. Cytokine production by T cells from vaccinated subjects after in vitro stimulation with homologous (NF54) or heterologous (7G8) PfSPZ were highly correlated. Interestingly, PfSPZ-specific T-cell responses in the blood peaked after the first immunization and were not enhanced by subsequent immunizations. Collectively, these data suggest durable protection against homologous and heterologous Pf parasites can be achieved with PfSPZ Vaccine. Ongoing studies will determine whether protective efficacy can be enhanced by additional alterations in the vaccine dose and number of immunizations.

Keywords: T-cell immunology; live-attenuated vaccine; malaria; plasmodium; sporozoite.

Publication types

  • Clinical Trial, Phase I
  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Adolescent
  • Adult
  • Female
  • Healthy Volunteers
  • Humans
  • Malaria Vaccines / administration & dosage*
  • Malaria Vaccines / adverse effects
  • Malaria Vaccines / immunology
  • Malaria, Falciparum / immunology
  • Malaria, Falciparum / parasitology
  • Malaria, Falciparum / prevention & control*
  • Male
  • Middle Aged
  • Plasmodium falciparum / drug effects*
  • Plasmodium falciparum / pathogenicity
  • Sporozoites / immunology
  • Sporozoites / pathogenicity
  • T-Lymphocytes / drug effects
  • T-Lymphocytes / immunology
  • T-Lymphocytes / parasitology
  • Vaccines, Attenuated / administration & dosage*
  • Vaccines, Attenuated / adverse effects
  • Vaccines, Attenuated / immunology


  • Malaria Vaccines
  • Vaccines, Attenuated