Regulation of gene expression by human foamy virus and potentials of foamy viral vectors

The hallmarks of the spumaretrovirus or human foamy virus (HFV) are summarized and discussed with special focus on the potentials to use HFV as a new retroviral vector system. The special features of HFV are the expression of pol by splicing and start of translation at a defined initiation codon. The first Met of Pol is conserved in the six known foamy virus genomic sequences. Another remarkable characteristic of HFV is the presence of a Gly-Arg-rich sequence instead of the Cys-Cys motif of the classical retroviral nuclecapsid proteins. The preferential budding of HFV into cytoplasmic vesicles and the potential to exploit it in the application of corresponding vector systems is discussed. In addition, recent reports of transducing marker genes into susceptible cells will be reviewed.