New discovery may prevent malaria transmission

Updated: Mar 12, 2010, 00:00 AM IST

Washington: A research team from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, has made a novel discovery that could help block malaria transmission.

While studying the Anopheles gambiae mosquito – the main vector of malaria – the researchers found that when the mosquito takes a blood meal, that act triggers two enzymes to form a network of crisscrossing proteins around the ingested blood.

The authors found that the formation of this protein barrier is part of the normal digestive process that allows so-called ‘healthy’ or commensal gut bacteria to grow without activating mosquito immune responses.

However, there is a downside: The barrier also prevents the mosquito`s immune defense system from clearing any disease-causing agents that may have slipped into the blood meal, such as the Plasmodium malaria parasite, which in turn can be passed on to humans.

But disrupting the protein barrier can trigger mosquito immune defenses to intervene and protect the insect from infection, the researchers said.

The enzymes involved in the protein barrier are called immunomodulatory peroxidase (IMPer) and dual oxidase (Duox).

The researchers believe it might be possible to prevent the formation of the protein barrier by immunizing people with IMPer or the proteins that crisscross.

This vaccine would generate antibodies that, after a mosquito feeds on a human, could disrupt the barrier, reduce parasite survival in the mosquito and prevent malaria transmission.

According to Carolina Barillas-Mury, the senior study author, the role of IMPer-Duox in forming a protective barrier was unexpected – and previously unrecognised.

When her research group silenced, or turned off, the gene for either IMPer or Duox, the mosquito``s midgut immune system took over and greatly reduced Plasmodium infection, indicating that IMPer and Duox are both required for parasite survival.