1999 Workshop Abstracts | Virus Evolution Home Page | Plant Biology Home Page

Reduced biological transmission of RNA virus populations following genetic bottlenecks

Lynn Cooper and Thomas Scott
Department of Entomology, University of Maryland, College Park, Maryland and Department of Entomology, University of California, Davis, California

An increasing number of in vitro studies have examined the negative effects of genetic drift on the replicative fitness of RNA virus populations In natural transmission cycles, severe population bottlenecks can be associated with the colonization of naive hosts in which new infections may potentially be initiated by a single founding virion. We simulated such a series of severe population bottlenecks in cell culture and then tested their effects in several whole animal systems. Twelve clonal lineages of the New World alphavirus, eastern equine encephalitis (EEE) virus were subjected to intensified genetic drift by propagation through twenty-five consecutive genetic bottleneck transfers in the BHK-21 cell line. Highly significant decreases in two correlated measures of viral fitness, plaque size and plaque yield, occurred over time (Factorial ANOVA, p<0.0001). Virus lineages which displayed reduced fitness in cell culture were less infectious for avian and mosquito hosts. In avian hosts, these lineages often failed to establish an infection and when successful, produced lower circulating viremias than did the ancestral control population. In mosquito hosts, more severe fitness declines were observed. When compared to their common ancestral control, the experimental lineages grew to lower levels within the bodies of infected mosquitoes. The transmission potential of these lineages was severely reduced, and virions were present in mosquito saliva less often and at strikingly lower levels. These results indicate that the overall transmission potential of these viruses was significantly lessened and suggest that the accumulation of one or more deleterious mutations impaired virus performance in multiple phases of the natural transmission cycle.

Abstract - Presented at the Virus Evolution Workshop
Ardmore, OK
October 21 - 24th, 1999

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e-mail: mroossinck@noble.org

Dr. Marilyn Roossinck
Plant Biology Division
The Noble Foundation
P.O. Box 2180
Ardmore, OK 73402

phone: 580 224-6630