Vaccine using live-attenuated malaria parasites shows promise
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Key takeaways:
- In a human challenge trial, the GA2 vaccine prevented 89% of people who received it from being infected with malaria.
- The proof-of-concept trial may add another vaccination method to the malaria armamentarium.
An experimental vaccine against malaria that uses live-attenuated Plasmodium falciparum malaria parasites showed promise in a small human challenge trial, researchers reported in The New England Journal of Medicine.
The vaccine, GA2, is a second-generation vaccine candidate that uses genetically attenuated — or weakened — malaria parasites that invade liver cells and develop through an early part of their life-cycle, causing asymptomatic infection and an immune responses but not a blood infection.
Although the trial showed promise, Meta Roestenberg, MD, professor of vaccinology and clinical head of the Controlled Human Infections Center at the Leiden University Center for Infectious Diseases in the Netherlands, told Healio that use of the vaccine is one or two generations away.
“This study is a proof-of-concept clinical trial using mosquitoes to administer the genetically attenuated parasite — consequently, it is not a vaccine yet,” Roestenberg said.
“The aim for the genetically attenuated vaccine is to achieve much higher efficacy than the currently available vaccines,” she said. “However, they are also in a much earlier development stage and far from [regulatory approval].”
In just the last 2 years, the world’s first two malaria vaccines — RTS,S and R21 — have been approved and rolled out across Africa.
GA2 is not the only live-attenuated malaria vaccine in development. Sanara’s PfSPZ vaccine has long been in development and in recent years showed promise in several trials.
Roestenberg and colleagues conducted a double-blind, controlled clinical trial among 20 healthy adult participants who had not had malaria. They compared the safety, side effects and efficacy of GA2 to the first generation GA1 vaccine that has not previously been highly effective and a placebo group.
They delivered the GA2 and GA1 vaccines via mosquitoes infected with genetically altered malaria parasites. The researchers randomly assigned nine participants to be exposed to 50 mosquito bites per immunization for GA2, eight participants to receive GA1 and three participants to be exposed to uninfected mosquitoes, according to the study.
After immunization, the researchers compared the efficacy of GA2 to GA1 and placebo using controlled human malaria infection. Participants in the placebo group were bitten by uninfected mosquitoes.
Adverse events were similar across all three groups, the researchers reported, with 89% of the GA2 group (eight of nine), 13% of the GA1 group (one of eight) and none of the three participants in the placebo group showing protective efficacy against malaria. Additionally, study participants who received GA2 had a significantly higher protective immune response than those given GA1, according to the study.
References:
- First of its kind vaccine expands malaria protection for pregnant women. https://sanaria.com/2024/08/14/first-of-its-kind-vaccine-expands-malaria-protection-for-pregnant-women/. Published Aug. 14, 2024. Accessed Nov. 20, 2024.
- Lamers OAC, et al. N Engl J Med. 2024;doi:10.1056/NEJMoa2313892.
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