Infectious simian varicella virus expressing the green fluorescent protein

Clinical, pathologic, immunologic and virologic features of simian varicella virus (SVV) infection in primates closely resemble varicella-zoster virus (VZV) infection in humans. Such similarities provide a rationale to analyze SVV infection in primates as a model of varicella pathogenesis and latency. Thus, we constructed an SVV-expressing green fluorescent protein (SVV-GFP) by inserting the GFP gene into the unique short segment of the virus genome by homologous recombination. Analysis of recombinant viral DNA and the expressed proteins of plaque-purified SVV-GFP confirmed the location of the GFP insert and that the recombinant SVV expressed the 27 kDa GFP. Infection of monkey kidney cells in tissue culture with SVV-GFP revealed bright green fluorescence associated with the characteristic focal cytopathic effect produced by SVV infection. Microscopic examination of lung from a 3-month-old African green monkey 10 days after infection with SVV-GFP revealed bright green fluorescence in areas of acute necrotizing pneumonitis. SVV-GFP allows ready identification of cells infected with SVV both in vitro and in vivo, and will be useful for further analysis of varicella pathogenesis and latency in experimentally infected animals--studies not possible in humans.