First in-human vaccine study for malaria caused by Plasmodium vivax

February 26, 2016

Walter Reed Army Institute of Research (WRAIR) researchers recently published the results of testing a Plasmodium vivax malaria vaccine candidate in a human challenge model.

A vaccine to prevent infection and disease caused by P. vivax is critical to reduce sickness and mortality from vivax malaria, a common cause of malaria among deployed service members. While malaria no longer poses a significant threat in developed countries, it affects millions of people every year around the world. P. vivax malaria is challenging to control because it can be dormant, causing no symptoms, and then become active causing symptomatic malaria weeks to months after initial infection.

The vaccine candidate developed by WRAIR and tested jointly with GlaxoSmithKline (GSK) to prevent vivax malaria infection is the first in-human study of its kind under an investigational new drug application with the US Food and Drug Administration. WRAIR investigators immunized 30 volunteers with three doses of the vaccine candidate. Malaria is only transmitted through the bite of a female mosquito. Immunized volunteers took part in WRAIR's well-established controlled human malaria infection (CHMI) model where they were bitten by malaria-infected mosquitoes. The efficacy of the vaccine candidate was then determined based on whether or not volunteers developed malaria by looking at blood smears or if it took longer for malaria parasites to appear in the blood.

"This study represents the first vaccine study to test the effectiveness of a P. vivax vaccine candidate in humans using controlled human malaria infection," said Lt. Col. Jason W. Bennett, the study's lead investigator. The study's results were published today in the journal PLOS Neglected Tropical Diseases. Unlike P. falciparum where a CHMI model is well established, the P. vivax CHMI model must rely on blood donations from infected humans to initiate infections in mosquitoes.

For this trial, the WRAIR investigators worked with the WRAIR overseas lab in Bangkok, Thailand, the Armed Forces Research Institute of Medical Sciences (AFRIMS), to acquire P. vivax-infected mosquitoes which were then transported to WRAIR for the malaria challenge. The vaccine candidate was well tolerated in all volunteers and generated robust immune responses. While the did not prevent , it did significantly delay parasitemia in 59% of vaccinated subjects.

Col. Robert Paris, director of the US Military Malaria Research Program at WRAIR, is optimistic that an improved vaccine can be designed. "Findings from the analysis of the immune response of vaccinated subjects have given us clues to improve vaccine candidates and studies are now underway at WRAIR to develop next generation vivax vaccines," says Dr. Paris, "Vaccines and antimalarial drugs are both critical needs for the DoD to protect service members from malaria."

Malaria challenge models require effective treatment for any resulting malaria infections. Investigators were also able to demonstrate that individuals with low or absent levels of a specific liver enzyme were unable to convert primaquine to an active drug form to kill the dormant stage of the parasites. These volunteers were more likely to experience vivax malaria relapse. The clinical data in this study is the first to show that differences in a person's genetics can result in primaquine treatment failure. Despite this newly identified limitation, primaquine remains the only FDA-approved drug to treat the dormant stages of vivax malaria.

WRAIR remains dedicated to developing vaccines, cures, and other products to eradicate and curb the transmission of infectious diseases. Decades of research at WRAIR have culminated in many effective products, including vaccines for yellow fever, dengue fever, and Japanese encephalitis. This study demonstrates WRAIR's continued dedication to prevention and marks an important step towards an effective P. vivax vaccine.

Explore further: Potential vaccine aims to block transmission of malaria parasites

Related Stories

Potential vaccine aims to block transmission of malaria parasites

November 9, 2015
The Jenner Institute at Oxford University, together with partners Imaxio and GSK, has started a phase I clinical trial of a novel vaccine candidate aimed at blocking transmission of malaria.

Southeast Asian ovalocytosis protects against P. vivax malaria

September 4, 2012
A multinational group of authors, led by Ivo Mueller from the Walter & Eliza Hall Institute, Australia and the Papua New Guinea Institute of Medical Research, have found a strong association between Southeast Asian ovalocytosis, ...

First-in-man trial of MERS vaccine begins

February 17, 2016
The Walter Reed Army Institute of Research (WRAIR) began vaccinations today in a Phase 1 clinical trial to evaluate the safety and immune response of a vaccine candidate to prevent Middle East Respiratory Syndrome (MERS).

Insecticide-treated nets may still prevent malaria despite mosquito resistance

February 26, 2016
Insecticide-treated nets may still help prevent malaria despite mosquitoes developing resistance, according to a new study published in Parasites & Vectors.

GSK asks European regulator to OK malaria shot

July 24, 2014
(AP)—Pharma giant GSK said Thursday it is submitting its malaria vaccine for regulatory approval to the European Medicines Agency.

Recommended for you

Researchers report new system to study chronic hepatitis B

July 25, 2017
Scientists from Princeton University's Department of Molecular Biology have successfully tested a cell-culture system that will allow researchers to perform laboratory-based studies of long-term hepatitis B virus (HBV) infections. ...

Research examines lung cell turnover as risk factor and target for treatment of influenza pneumonia

July 24, 2017
Influenza is a recurring global health threat that, according to the World Health Organization, is responsible for as many as 500,000 deaths every year, most due to influenza pneumonia, or viral pneumonia. Infection with ...

Scientists propose novel therapy to lessen risk of obesity-linked disease

July 24, 2017
With obesity related illnesses a global pandemic, researchers propose in the Journal of Clinical Investigation using a blood thinner to target molecular drivers of chronic metabolic inflammation in people eating high-fat ...

Raccoon roundworm—a hidden human parasite?

July 24, 2017
The raccoon that topples your trashcan and pillages your garden may leave more than just a mess. More likely than not, it also contaminates your yard with parasites—most notably, raccoon roundworms (Baylisascaris procyonis).

Google searches can be used to track dengue in underdeveloped countries

July 20, 2017
An analytical tool that combines Google search data with government-provided clinical data can quickly and accurately track dengue fever in less-developed countries, according to new research published in PLOS Computational ...

MRSA emerged years before methicillin was even discovered

July 19, 2017
Methicillin resistant Staphylococcus aureus (MRSA) emerged long before the introduction of the antibiotic methicillin into clinical practice, according to a study published in the open access journal Genome Biology. It was ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.