Polydnavirus Innexins Disrupt Host Cellular Encapsulation and Larval Maturation

Area of Science:

• Virology
• Insect Pathology
• Molecular Biology

Background:

• Polydnaviruses, symbiotic viruses of endoparasitoid wasps, are injected into host caterpillars.
• Virus gene expression manipulates host physiology, facilitating parasitoid development.
• Vinnexins are viral homologues of insect innexins (gap junction proteins) and are key viral gene families.

Purpose of the Study:

• To investigate the in vivo function of two polydnavirus vinnexin genes (vnxG and vnxQ2) in a susceptible caterpillar host.
• To determine the impact of vinnexin expression on caterpillar molting, survival, and immune responses.

Main Methods:

• Expression of vinnexin genes (vnxG, vnxQ2) using recombinant baculoviruses in Heliothis virescens caterpillars.
• Intrahemocoelic injection of recombinant baculoviruses to infect hemocytes and produce viral proteins.
• Assessment of molting rates, survival, and hemocyte encapsulation immune assays.

Main Results:

• Recombinant vinnexin baculoviruses infected >90% of hemocytes, leading to protein production.
• Infected larvae showed significantly reduced molting rates, lower survival, and impaired immune encapsulation compared to controls.
• VnxG expression resulted in more severe pathology than VnxQ2.

Conclusions:

• Vinnexins play a significant role in the pathology of *Campoletis sonorensis* ichnovirus (CsIV) and other ichnoviruses in lepidopteran hosts.
• Vinnexins disrupt host multicellular physiology, affecting development and immune functions.
• These findings provide insights into host susceptibility mechanisms and parasitoid host range.