Using a Combination Vaccine to Stamp Out Malaria

When Nirbhay Kumar, PhD, professor of global health at Milken Institute School of Public Health (Milken Institute SPH) arrived at the George Washington University (GW) from Tulane University, he was conducting a study of malarial vaccines with support from the National Institutes of Health (NIH). Now that the $1.9 million NIH grant has transferred to Milken Institute SPH, he and his team are forging ahead on the study.

“Our goal is to eliminate malaria, a disease that kills nearly half a million people a year, the majority of them children living in Africa,” Kumar said. “If we are successful, we will have a long-lasting, effective vaccine to combat this ancient disease.”

After arriving in D.C. in 2018, Kumar immediately began to establish his lab and help build a secure insectary, a place where mosquitos, responsible for malaria transmission, can be safely held and studied. Now, he and his team are hard at work on his current study, surrounded by the state-of-the art gleaming public health laboratory on the seventh floor of the GW Science and Engineering Hall.

Previously, Kumar and his colleagues developed and tested an experimental vaccine aimed at blocking transmission when a mosquito bites an infected person. The transmission blocking vaccines or TBVs are given to people and they induce antibodies that abort the sexual development of the malaria-causing parasite in the gut of the mosquito. Thus, these mosquitos are no longer infected with the parasites and are incapable of spreading malaria.

The parasite must go through this sexual development in order for it to be transmitted again to another human – thus the antibodies induced by TBVs effectively block the spread of the disease from mosquitos to humans. The next time the mosquito bites a person, there is the itch of the bite but no transfer of the malaria-causing Plasmodium.

Kumar and his team have shown that TBVs are about 90 percent effective when tested in mice and monkeys. If they had created a vaccine that was close to 100 percent effective at blocking transmission of the parasite, the battle would be over, Kumar adds. Efforts are underway to improve this transmission blocking efficacy.

In addition, to close the gap, Kumar wanted to add another vaccine to the mix, one that when combined with TBVs would deliver a one-two punch capable of eliminating malaria.

The team is now working on a combination vaccine that would not only prevent transmission from infected people to mosquitos but also the other way around – from infected mosquitos to healthy people. Combining the two vaccines together would stop the cycle that results in hundreds of millions of malaria cases worldwide every year.

Kumar says they have already begun testing this combination vaccine in mice and will know by the end of the year if it is effective.

Still, the team is a long way off from the next step: an effective and safe combination vaccine that can be given to people, he says. Once the testing in animals, including primates, is completed the researchers will seek a partnership with a company to produce the vaccine for testing in clinical trials – a process that can take several years before a safe and reliable product makes it through the U.S. Food and Drug Administration approval process to the marketplace.

Kumar points out there is no animal reservoir for the parasite that causes human malaria so if the combination vaccine approach starts to work, the number of malaria cases will start to dwindle.

“There are more than 200 million cases of malaria today in countries around the world,” Kumar said. “We want to bring that number down to the point where the elimination of malaria is within sight.”