Activation of mosquito complement antiplasmodial response requires cellular immunity

Area of Science:

• Immunology
• Entomology
• Parasitology

Background:

• The mosquito complement-like system is vital for limiting Plasmodium infection.
• Hemocytes are suspected to play a role in early anti-Plasmodium responses, but their exact function is unknown.

Purpose of the Study:

• To investigate the role and fate of hemocytes during Plasmodium infection in mosquitoes.
• To elucidate the mechanism by which hemocytes contribute to anti-Plasmodium immunity.

Main Methods:

• Hemocyte populations were labeled in vivo to track their response to Plasmodium infection.
• Hemocyte-derived microvesicle (HdMv) release was manipulated using gene silencing, immune priming, and polystyrene bead injection.
• The impact of HdMv release on complement activation was assessed.

Main Results:

• Midgut nitration, induced by ookinete invasion, triggers the release of HdMvs into the midgut basal labyrinth.
• HdMv release is directly linked to hemocyte contact with the nitrated midgut basal surface.
• This HdMv release is essential for the effective activation of the mosquito complement system.

Conclusions:

• Hemocyte-derived microvesicles are critical mediators of the mosquito's anti-Plasmodium immune response.
• HdMvs likely deliver factors that activate thioester-containing protein 1, a key component of mosquito antiplasmodial immunity.