BIOBRIEF
An investigational drug halts the malaria parasite in the liver before it can reach the blood and cause disease, turning each mosquito delivered parasite into an immune training event and sparing mice from illness.
A mosquito bite, normally the start of a malaria infection, has been turned into the vaccination event itself. In a mouse study, researchers paired the bite with an investigational drug that halts the parasite at a late liver stage, so it never causes disease but still trains the immune system. The approach is called chemovaccination: the live parasite still arrives via the mosquito, but the drug acts as a safety brake.
Malaria kills more than 600,000 people a year, mostly pregnant women and children under five in Africa, according to WHO figures cited in coverage. Existing liver-stage vaccines such as RTS,S and R21 require multi-dose regimens and cold-chain logistics that have limited reach. A vaccine that piggybacks on the mosquito itself would change the delivery math.
The work comes from the Walter and Eliza Hall Institute (WEHI) in Melbourne with drug partner MSD (known as Merck & Co. in the US and Canada). Findings published this month in Science show that mice given the drug and then exposed repeatedly to malaria-carrying mosquitoes built durable protection within the study period. Lead researcher Justin Boddey (WEHI) said the team had "found a way to turn mosquito bites — the very thing that spreads malaria — into vaccination events in mice."
The leap from mouse to human is large. The Plasmodium species used in mouse models does not mirror P. falciparum, and the drug would have to be present at every bite. Whether late-stage arrest holds in people, and how long protection lasts past the study window, are the questions the next round of work has to answer.