Hz-2V (a.k.a. gonad specific virus, GSV) is unusual among insect pathogenic viruses in that productive replication of this virus does not lead to insect mortality but rather to the sterility of the infected adult moth. This fact is the principle feature of the virus that led to its discovery in a laboratory colony of Helicoverpa zea from Stoneville, MS (6, 11). The Stoneville colony of H. zea, later found to be carrying the virus, was difficult to maintain and periodically went through periods of low fecundity due the high level of sterile individuals in the colony (7). It was later determined that these sterile moths had malformed reproductive tissues, a condition which has been referred to as being agonadal (AG).
Insects from the Stoneville colony were found to be able to transmit Hz-2V to healthy partners during mating as evidenced by the AG progeny resulting from these matings (6). In a series of experiments involving matings between infected, Stoneville insects and healthy partners, it was demonstrated that not only was Hz-2V transmitted by both infected males and females during mating, but also that some Stoneville females were fertile, asymptomatic (AS) carriers of the virus. These AS individuals gave rise to AG progeny when mated to healthy male moths. In addition, the results of these mating experiments suggested that only females could be AS carriers of the virus, since individual mating pairs of Stoneville males and healthy females produced either no viable eggs or only healthy progeny. Virus infected AG progeny were only observed to result from mass matings of Stoneville males and healthy females; presumably arising from matings of uninfected Stoneville males and females infected with Hz-2V via prior mating attempts with infected, AG Stoneville males.
Another important finding of these mating experiments was that the level of AG progeny hatching from eggs produced by matings with infected Stoneville moths increased with increasing oviposition days. This suggested that productive virus replication took place in infected, fertile females (either AS carriers or those acquiring virus from infected males) with an increase in virus dose being transferred to eggs laid on successive oviposition days. The site and basis for this virus replication, as well as the mechanism by which Hz-2V is transferred to eggs developing in infected females, has yet to be determined.
The Sexually Transmitted Insect Virus, Hz-2V
- Received Date: 31 January 2009
- Accepted Date: 29 April 2009
Abstract: Hz-2V is one of only a very few sexually transmitted viruses currently known in insects. Replication of this insect pathogenic virus results in sterility of infected moths rather than mortality. The sterility of the infected host is a consequence of virus directed malformation of adult reproductive tissues, which in females results in cellular proliferation and hypertrophy of these tissues. Virus replication has additional ramifications in infected females. Infected females produce more mating pheromones and attract more mates than healthy females, ultimately facilitating virus transmission and enhancing viral fitness. The molecular mechanisms used by the virus to manipulate the host to enhance its fitness are yet to be determined. Unraveling the underlying principles of these mechanisms promises to enhance our understanding of insect reproductive physiology, as well as provide molecular tools for use in novel approaches in sterile insect control programs.