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Experimental Malaria Vaccine Provides Durable Protection Against Multiple Strains in NIH Clinical Trial

Kirsten E. Lyke, MD

University of Maryland School of Medicine Research Shows Vaccine’s Versatility

An experimental malaria vaccine protected healthy subjects from infection with a malaria strain different from that contained in the vaccine, according to a study published this week in the Proceedings of the National Academy of Sciences (PNAS). The research was conducted by scientists at the University of Maryland School of Medicine and the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH).

The Phase 1 clinical trial is important because in places where malaria is common, there is usually more than one strain of malaria. To be effective in the real world, a vaccine must protect against more than one. The study’s lead researcher, Kirsten E. Lyke, MD, associate professor of medicine at the University of Maryland School of Medicine and a senior scientist at the Center for Vaccine Development, said the vaccine’s versatility was promising. “Our study shows that that this vaccine can protect against at least two strains of malaria,” said Dr. Lyke, who has studied malaria for more than a decade. “We need to continue our research, but this is a fantastic finding.”

Malaria is transmitted to humans through the bite of infected mosquitoes, which inject immature malaria parasites called sporozoites into a person’s bloodstream. The parasites travel to the liver, where they mature, multiply and spread via the bloodstream throughout the body causing malaria symptoms including chills, fever, headache, nausea, sweating and fatigue. According to the World Health Organization, 212 million people were infected with malaria globally in 2015 and 429,000 people died, mostly young children in Africa. The species Plasmodium falciparum is the most common cause of malaria morbidity and mortality in Africa. In the United States, travel-related malaria is a concern for international tourists, aid workers and military personnel worldwide.

The PfSPZ Vaccine used in this study was developed by Sanaria Inc., of Rockville, Maryland. The vaccine contains weakened P. falciparum sporozoites that do not cause infection but are able to generate a protective immune response that protects against live malaria infection. Earlier research with the vaccine found it to be safe, well-tolerated and protective for more than a year when tested in healthy U.S. adults against a single Africa-derived malaria strain matched to the PfSPZ Vaccine.

The study enrolled 31 healthy adults ages 18 to 45 years, and was led by Dr. Lyke and Robert A. Seder, MD, chief of the Cellular Immunology Section of NIAID's Vaccine Research Center (VRC). Participants were assigned to receive three doses of the vaccine over several months by rapid intravenous injection.

Nineteen weeks after receiving the final dose of the test vaccine, participants who received the vaccine and a group of non-vaccinated volunteers were exposed in a controlled setting to bites from mosquitoes infected with the same strain of P. falciparum parasites (NF54, from Africa) that were used to manufacture the PfSPZ Vaccine.

Nine of the 14 participants (64 percent) who received the PfSPZ Vaccine demonstrated no evidence of malaria parasites; all six of the non-vaccinated participants who were challenged at the same time had malaria parasites in their blood.

Of the nine participants who showed no evidence of malaria, six participants were again exposed in a controlled setting to mosquito bites, this time from mosquitoes infected with a different strain of P. falciparum parasite, 33 weeks after the final immunization. In this group, 5 of the 6 participants (83 percent) were protected against malaria infection; none of the six participants who did not receive the vaccine and were challenged were protected. All participants who became infected with malaria immediately received medical treatment.

The research team found that the PfSPZ Vaccine activated T cells, a key component of the body’s defenses against malaria, and induced antibody responses in all vaccine recipients. Vaccine-specific T-cell responses were comparable when measured against both of the malaria challenge strains, providing some insights into how the vaccine was mediating protection.

Ongoing research will determine whether protective efficacy can be improved by changes to the PfSPZ Vaccine dose and number of immunizations. Accordingly, a Phase II efficacy trial testing three different dosages in a three-dose vaccine regimen is now underway in 5- to 12-month-old infants in Western Kenya to assess safety and efficacy against natural infection.

“Malaria remains an urgent global health problem, one that shortens far, far too many young lives,” said University of Maryland School of Medicine Dean
E. Albert Reece, MD, PhD, MBA, who is also the vice president for Medical Affairs, University of Maryland, and the John Z. and Akiko K. Bowers Distinguished Professor. “This vaccine has the potential to save millions of lives, and I am sure that these researchers will continue to collaborate on this exciting work.”

About the University of Maryland School of Medicine

Commemorating its 210th Anniversary, the University of Maryland School of Medicine was chartered in 1807 and is the first public medical school in the United States and continues today as an innovative leader in accelerating innovation and discovery in medicine. The School of Medicine is the founding school of the University of Maryland and is an integral part of the 11-campus University System of Maryland. Located on the University of Maryland’s Baltimore campus, the School of Medicine works closely with the University of Maryland Medical Center and Medical System to provide a research-intensive, academic and clinically based education. With 43 academic departments, centers and institutes and a faculty of more than 3,000 physicians and research scientists plus more than $400 million in extramural funding, the School is regarded as one of the leading biomedical research institutions in the U.S. with top-tier faculty and programs in cancer, brain science, surgery and transplantation, trauma and emergency medicine, vaccine development and human genomics, among other centers of excellence. The School is not only concerned with the health of the citizens of Maryland and the nation, but also has a global presence, with research and treatment facilities in more than 35 countries around the world. medschool.umaryland.edu/

About the National Institutes of Health (NIH)

NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.

Learn More

• Center for Vaccine Development (CVD)

• Division of Malaria Research

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