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

The Spumaviridae (foamy viruses) are increasingly being considered as poten tial vectors for gene therapy, yet little has been documented of their basi c 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 m ammalian, but on avian and reptilian cells. Receptor interference assays us ing an envelope-expressing cell line and a vesicular stomatitis virus/HFV p seudotype virus demonstrate that the cellular receptor is common to all pri mate members of the genus. The majority of foamy virus particles assemble a nd remain sequestered intracellularly. A rapid and quantitative method of a ssaying foamy virus infectivity by reverse transcriptase activity facilitat es the use of classical protocols to increase infectious virus titres in vi tro to greater than or equal to 10(6) TCID/ml.