title: Mixed infections and the competitive fitness of faster-acting genetically modified viruses.
abstract: Faster-acting recombinant baculoviruses have shown potential for improved suppression of insect pests, but their ecological impact on target and nontarget hosts and naturally occurring pathogens needs to be assessed. Previous studies have focused on the fitness of recombinants at the between-hosts level. However, the population structure of the transmission stages will also be decided by within-host selection. Here we have experimentally quantified the within-host competitive fitness of a fast-acting recombinant Autographa californica multicapsid nucleopolyhedrovirus missing the endogenous egt gene (vEGTDEL), by means of direct competition in single- and serial-passage experiments with its parental virus. Quantitative real-time PCR was employed to determine the ratio of these two viruses in passaged mixtures. We found that vEGTDEL had reduced within-host fitness: per passage the ratio of wild type to vEGTDEL was on average enhanced by a factor of 1.53 (single passage) and 1.68 (serial passage). There is also frequency-dependence: the higher the frequency of vEGTDEL, the stronger the selection against it is. Additionally, the virus ratio is a predictor of time to host death and virus yield. Our results show that egt is important to within-host fitness and allow for a more complete assessment of the ecological impact of recombinant baculovirus release.
authors.affiliation: Laboratory of Virology, Wageningen University Wageningen, The Netherlands ; Laboratory of Genetics, Wageningen University Wageningen, The Netherlands.
authors.forename: Mark P
authors.initials: MP
authors.lastname: Zwart
authors.affiliation: Crop and Weed Ecology Group, Wageningen University Wageningen, The Netherlands.
authors.forename: Wopke
authors.initials: W
authors.lastname: Van Der Werf
authors.affiliation: Laboratory of Virology, Wageningen University Wageningen, The Netherlands.
authors.forename: Monique M
authors.initials: MM
authors.lastname: Van Oers
authors.affiliation: Biometris, Wageningen University Wageningen, The Netherlands.
authors.forename: Lia
authors.initials: L
authors.lastname: Hemerik
authors.affiliation: Laboratory of Virology, Wageningen University Wageningen, The Netherlands.
authors.forename: Jan M V
authors.initials: JM
authors.lastname: Van Lent
authors.affiliation: Laboratory of Genetics, Wageningen University Wageningen, The Netherlands.
authors.forename: J Arjan G M
authors.initials: JA
authors.lastname: De Visser
authors.affiliation: Laboratory of Virology, Wageningen University Wageningen, The Netherlands.
authors.forename: Just M
authors.initials: JM
authors.lastname: Vlak
authors.affiliation: Department of Biology, Algoma University Sault Ste. Marie, Ontario, Canada ; Department of Biological Sciences, Simon Fraser University Burnaby, British Columbia, Canada.
authors.forename: Jenny S
authors.initials: JS
authors.lastname: Cory
keywords: agriculture; baculovirus; egt; experimental evolution; genetically modified organisms; host parasite interactions; population ecology