Researchers at the Walter and Eliza Hall Institute (WEHI) in Melbourne, Australia, have developed a new vaccination approach that uses antimalarial drug compounds to transform mosquito bites from a source of deadly infection into natural immune boosters, according to a study published in Science.
Targeting the Late Liver Stage to Build Durable Immunity
The preclinical study demonstrates that pairing mosquito-delivered malaria parasites with investigational drug compounds can stop infections just before they reach the bloodstream. According to WEHI Associate Professor Justin Boddey, this strategy traps the parasite at the end of liver-stage development. This method gives the immune system a fuller preview of potential threats using a very small dose of parasites, triggering both antibodies and CD8+ T cells to protect against reinfection.
Pro tip: Understanding how liver-resident memory T cells function is critical for next-generation vaccine design, as these cells can respond rapidly to eliminate future infections before disease develops, according to WEHI researchers.
A Decade-Long Collaboration Behind WM382 and MK-7602
The antimalarial drug candidates utilized in the study, designated WM382 and MK-7602, are dual inhibitors of plasmepsin IX and X. These enzymes act as master regulators crucial for parasite survival. The compounds are the result of a ten-year research partnership between WEHI and global biopharmaceutical company MSD, a tradename of Merck & Co., Inc., Rahway, N.J., USA. John A. McCauley, Senior Director, Discovery Chemistry at MSD, noted that using a drug to arrest parasites at the late liver stage enables the immune system to recognize a broader range of malaria antigens than traditional genetically attenuated parasite approaches.
Did you know? Malaria claims the lives of more than 600,000 people annually, primarily pregnant women and children under the age of five, with the World Health Organization reporting that one child in Africa dies from the disease every two minutes.
Real-World Implications and Long-Acting Preclinical Development
Because the targeted enzymes are highly conserved across malaria species, researchers hope the approach will protect against a wide range of variants. This could allow individuals living in endemic areas to build and sustain progressive long-term immunity through repeated natural mosquito bites. A long-acting injectable based on these compounds is currently in preclinical development, supported by MSD, The Wellcome Trust, National Health and Medical Research Council of Australia (NHMRC) and Victorian State Government.
Frequently Asked Questions
How do mosquito bites act as vaccine boosters in this study?
When paired with investigational antimalarial drugs like WM382 or MK-7602, small doses of parasites delivered by mosquitoes are arrested at the late liver stage. This triggers a multi-layered immune response, allowing subsequent mosquito bites to reinforce immunity over time, according to WEHI researchers.
What are plasmepsin IX and X?
Plasmepsin IX and X are master regulator enzymes crucial for malaria parasite survival. The drug candidates WM382 and MK-7602 target both of these enzymes simultaneously.
How long did the protection last in the preclinical study?
According to the study published in Science, the immunisation strategy protected mice from developing the disease for up to two years, which covers two malaria seasons in real-world settings.
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