Parasitoid virus-like particles destroy Drosophila cellular immunity

Area of Science:

• Insect immunology
• Parasitoid-host interactions
• Cellular defense mechanisms

Background:

• Parasitoid wasps require overcoming host immune responses for successful reproduction.
• Drosophila melanogaster employs lamellocytes for encapsulating foreign objects, including parasitoid eggs.
• Leptopilina heterotoma females possess a mechanism to neutralize Drosophila's cellular defenses.

Purpose of the Study:

• To identify the factor injected by Leptopilina heterotoma that neutralizes Drosophila lamellocytes.
• To elucidate the mechanism by which this factor affects different Drosophila blood cell types.

Main Methods:

• In vitro experiments exposing Drosophila blood cells to the identified factor.
• Microscopic analysis to observe the entry and intracellular localization of the factor.
• Differential cell viability assays for lamellocytes and plasmatocytes.

Main Results:

• The destructive factor is identified as virus-like particles (VLPs) from a female wasp accessory gland.
• VLPs selectively infect and are found free in the cytoplasm of susceptible lamellocytes.
• VLPs are contained within phagocytic vesicles of resistant plasmatocytes, indicating differential cellular uptake or processing.

Conclusions:

• Virus-like particles are key effectors in the parasitoid-host interaction, specifically targeting lamellocytes.
• The intracellular fate of VLPs dictates the survival of Drosophila blood cells, differentiating between lamellocytes and plasmatocytes.
• This mechanism highlights a sophisticated strategy employed by parasitoids to subvert host immunity.