Properties of human foamy virus relevant to its development as a vector for gene therapy

The Spumaviridae (foamy viruses) are increasingly being considered as potential vectors for gene therapy, yet little has been documented of their basic cell biology. This study demonstrates that human foamy virus (HFV) has a broad tropism and that the receptor for HFV is expressed not only on many mammalian, but on avian and reptilian cells. Receptor interference assays using an envelope-expressing cell line and a vesicular stomatitis virus/HFV pseudotype virus demonstrate that the cellular receptor is common to all primate members of the genus. The majority of foamy virus particles assemble and remain sequestered intracellularly. A rapid and quantitative method of assaying foamy virus infectivity by reverse transcriptase activity facilitates the use of classical protocols to increase infectious virus titres in vitro to > or = 10(6) TCID/ml.