Construction of Infectious Simian Varicella Virus Expressing Green Fluorescent Protein

Abstract

Determining the precise location of pathogenic events inside living cells is critical to the understanding of infectious and other biological processes. Molecular cloning and expression of the green fluorescent protein (GFP) from the jellyfish Aequorea victoria, which emits bright green fluorescence at 509 nm (1), has enabled visualization of events within eukaryotic cells. GFP is stable with minimal photobleaching (1), and the gene-encoding GFP has been modified to enhance the fluorescence several-fold (2). The authors have used GFP to label simian varicella virus (SVV) by homologous recombination (3). SVV infection in primates resembles varicella zoster virus (VZV) infection in humans, clinically, pathologically, immunologically, and virologically, including features of latency in ganglia. VZV causes chickenpox (varicella) in children, becomes latent in dorsal root ganglia, and reactivates decades later to produce shingles (zoster). SVV causes a similar disease in monkeys, enters ganglia by hematogenous spread (4), and remains latent in their ganglia for the lifetime of the animal. SVV expressing GFP (SVV-GFP) allows ready identification of cells infected with virus, both in vitro and in vivo, and is potentially useful for further analysis of varicella pathogenesis and latency in experimentally infected animals: such studies are not possible in humans.