Densovirinae as Gene Transfer Vehicles

Abstract

Densoviruses present an attractive opportunity to develop expression vectors for insects. They exhibit several features that are beneficial for such vectors. The genomes of densoviruses are among the smallest of animal DNA viruses, and, therefore are easier to use for cloning and transfection procedures. The fact that cloned densovirus genomes are infectious greatly simplifies their applications. It seems that both densovirus promoters have high constitutive activity and they can be further transactivated with NS. The major nonstructural protein, NS1, can retain its functions even if fused to a foreign protein. If the recombinant genome carrying a gene of interest is supplied with the missing virus functions, it can be packaged into transducing particles. The packaging capacity of the densovirus particles can accommodate a foreign gene encoding a polypeptide of up to 150 kDa. Finally, the functions missing from the recombinant densovirus genome that are necessary for the production of transducing particles can be supplied in several different ways: they can be expressed from a helper plasmid, in cells transformed with the virus genes, or from an RNA virus. The last two methods produce transducing particles which are free of wild type virus. Densovirus transducing particles can be used for the delivery and expression of a gene of interest in insect cell culture or living insects. Transducing particles expressing reporter genes can be valuable tools in the study of viral pathogenesis and perhaps in the genetic manipulation of insects.

Junonia coenia Densovirus-Based Vectors for Stable Transgene Expression in Sf9 Cells: Influence of the Densovirus Sequences on Genomic Integration

“…The cloning of the entire JcDNV genome into pBR322 led to a recombinant construct (pBRJ) that retained the capacity to produce infectious particles when injected into larvae of the sensitive host Spodoptera littoralis or transfected into lepidopteran cell lines (20,24,25). The availability of plasmids carrying an infectious sequence of either the JcDNV or the Aedes aegypti densovirus genome has prompted the study of densoviruses as expression vectors (1,2,5,10,16,31). The A. aegypti densovirus, a prototype of the Brevidensovirus genus, has been developed as a gene transfer vehicle that is able to transduce genes into mosquito larvae by typical routes of in-fection, opening the potential for gene introduction into natural populations (1,2).…”

Replication of Flock House Virus in Three Genera of Medically Important Insects

“…Mosquito cell cultures supporting replication of alphaviruses (such as Sindbis virus and Semliki Forest virus) and bunyaviruses (such as La Crosse virus) have been found useful for such purposes (Fallon andSun, 2001, Kempf et al, 2006). Viral expression vectors based on alphaviruses such as Sindbis virus, Semliki Forest virus, OÕnyong-nyong virus (Brault et al 2004, Chikingunya virus (Vanlandingham et al 2005), and densonucleosis viruses (Afanasiev and Carlson 2000) are continuously being developed and used to study mosquito gene functions. Each of these viruses has its own limitations in host range and tissue speciÞcities, and most of them are pathogenic to humans.…”

Transgenic mosquitoes and malaria transmission

“…A potentially useful system for transgene expression could be densoviruses as they specifically infect mosquitoes and thus assure that the trait is not spread into non‐target organisms (Afanasiev and Carlson, 2000). However, the virus is lethal for mosquitoes and, unless a non‐virulent strain is created, thus inappropriate for gene expression.…”