In a report published in the Proceedings of the National Academy of Sciences, attenuated PfSPZ vaccine induces strain-transcending T cells and durable protection against heterologous controlled human malaria infection.
Investigators from the National Institute of Allergy and Infectious Diseases (NIAID), NIH and the University of Maryland School of Medicine reported that nine of fourteen subjects (64%) immunized with three doses of Sanaria PfSPZ Vaccine were protected against homologous challenge with Plasmodium falciparum malaria 19 weeks after their last vaccine dose.
Moreover, five of six of the protected subjects who underwent a subsequent heterologous challenge with Plasmodium falciparum 33 weeks after their last vaccine dose were protected. Dr. Robert A. Seder, MD, of the Vaccine Research Center, NIAID, NIH and Dr. Kirsten Lyke, MD at The University of Maryland School of Medicine led the studies.
PfSPZ Vaccine was administered to the 14 subjects at a higher vaccine dose than had been given in prior studies; the research also demonstrated that the three doses were safe. PfSPZ Vaccine is comprised of live, attenuated malaria parasites. Volunteers in the clinical trial received three 0.5 mL injections of the vaccine by rapid direct venous inoculation.
The clinical trial included volunteers 19 to 45 years old. Fourteen volunteers received at least three doses of PfSPZ Vaccine, 12 volunteers were control subjects. Nineteen weeks after last immunization, nine of the fourteen volunteers (64%) who received 3 doses of PfSPZ Vaccine were protected against malaria parasites similar to those in the vaccine that were transmitted by exposure to malaria-infected mosquitoes.
In a subset of the protected subjects, five out of six vaccinated subjects were protected against parasites different from those in the vaccine thirty-three weeks after the final immunization. All 12 control volunteers developed malaria. Collectively, these data show that a 3-dose regimen of PfSPZ Vaccine confers durable protection against malaria parasites that are same and different than the malaria parasites from which the vaccine is made.
Dr. Stanley Plotkin, former Medical and Scientific Director of the vaccine company, Aventis Pasteur, now Sanofi Pasteur, discoverer of the German measles vaccine, and perhaps the most prominent vaccinologist in the U.S. said, “For my entire career I have been hearing about the potential for a highly effective malaria vaccine that protects through induction of strain-transcending killer T cells. This paper indicates that PfSPZ Vaccine induces this type of immunity. This is an enormously important finding. The next step is to refine the immunization regimen to achieve even higher levels of protection, and I am optimistic this team of investigators will succeed.”
African children are hardest hit by malaria. The World Health Organization estimates that in 2015 malaria caused 214M clinical episodes and 438,000 deaths worldwide; others have estimated up to 730,500 malaria deaths in 2015. This enormous morbidity and mortality occurs despite investment of billions of dollars in malaria control efforts.
Malaria is also a concern for tourists, diplomats, business travelers, aid workers, industrial workers, and military personnel worldwide.
Professor Chris Plowe, Founding Director, Institute for Global Health, University of Maryland School of Medicine said, “Because of the spread of drug resistance, we’re dangerously close to having truly untreatable malaria. A highly effective vaccine is desperately needed to move faster toward elimination and to prevent losing ground to resistance. These results confirming that a single-strain whole organism vaccine can be effective against diverse strains of malaria are an important step toward having an immunization regimen that can be used for mass vaccination campaigns to eliminate malaria from populations and prevent infection in individual travelers.”
Adel Mahmoud, former President of Merck Vaccines, and Sanaria and Foundation for Vaccine Research Director said, “Vaccines are the most highly efficient interventions for control and elimination of infectious diseases. The world needs a highly effective malaria vaccine. Sanaria’s PfSPZ-based vaccines are the only malaria vaccines to have shown >90% protective efficacy at any point after the last dose of vaccine.
This report moves Sanaria one step closer to establishing an immunization regimen that provides the long-term, high-level protection against malaria that we so desperately need to achieve elimination of this deadly parasite, which has been the scourge of humanity for so many millenia.”
