Interactions of a novel cypovirus in the Heliothis virescens and Campoletis sonorensis host parasitoid system

Some viruses, notably the ascoviruses, are reliant upon parasitoid wasps for horizontal transmission between their lepidopteran hosts. Other viruses, the polydnaviruses, are obligate symbionts of parasitoid wasps, existing in highly commensal and evolved relationships with their parasitoid hosts. Among the viruses associated with parasitoid wasps, polydnaviruses are considered beneficial to the wasp and are essential in the parasitism of lepidopteran hosts. In contrast, the impact of ascoviruses within the wasp-host system can be detrimental to both the wasp and host. There are many viruses, however, associated with parasitoid wasps or the lepidopteran host, and little is known about their impact on the host-parasitoid system.

We have recently discovered two genetic variants of a dsRNA Cypovirus (CPV) in laboratory colonies of the parasitoid wasp, Campoletis sonorensis and in the wasp’s conventional host, Heliothis virescens larvae. CPVs typically cause non-lethal effects in insects and are similar, but unrelated, to Baculoviruses as the virions are occluded and protected by a polyhedral matrix.

We characterized and sequenced the CPV variants and discovered a mutation in the polyhedrin-encoding segment. We then examined the unique pathologies and biological effects of these variants in our C. sonorensis and H. virescens colonies. CPVs are common insect colony pathogens, yet little is known about their effects on a complex biological system. We describe here a novel virus which appears to interact with a host-parasitoid system in a fundamentally new and intriguing way.