Targeting Anopheles mosquitoes' sperm could help in fight against malaria

Researchers have suggested that targeting sperm protection in mosquitoes could help in the fight against malaria.

Anopheles gambiae mosquitoes are the main transmitters of malaria, which affects around 200 million people every year. The females mate only once during their lives. They store the sperm from this single mating in an organ called the spermatheca, from which they repeatedly take sperm over the course of their lifetime to fertilise the eggs that they lay.

The female needs the sperm to stay healthy whilst they are in storage in the spermatheca, so that they are viable each time she uses them to reproduce.

The new research reveals that the sperm are partly protected by the actions of an enzyme called HPX15. When the researchers interfered with HPX15 in female A. gambiae mosquitoes in the laboratory, the females fertilised fewer eggs and therefore produced fewer offspring.

This is the first time that scientists have discovered a mechanism that preserves the function of sperm in A. gambiae.

The new study by researchers, from Harvard School of Public Health, the University of Perugia and Imperial College London suggests that HPX15 may protect the stored sperm against potentially damaging molecules called free radicals, which are particularly abundant after a female takes a blood feed. Ensuring that the sperm are healthy after blood-feeding is important for the female's fertility as she reproduces after each feed, fertilising her eggs with sperm released from the spermatheca.

In addition to uncovering the role of HPX15, the researchers also discovered how it is activated, suggesting another possible target for immobilising the enzyme. The male mosquito transfers a hormone called 20E to the female during mating and it is this hormone that induces the expression of HPX15 in the female.

The new research has been published in the journal Proceedings of the National Academy of Sciences.