HIGH-TITER PACKAGING CELLS PRODUCING RECOMBINANT RETROVIRUSES RESISTANT TO HUMAN SERUM

Novel retroviral protein expression constructs were designed to retain minimal retroviral sequences and to express dominant selectable marke rs by reinitiation of translation after expression of the viral genes, HT1080 cells were selected as producer cells for their ability to rel ease high-titer viruses that are resistant to inactivation by human se rum. Two HT1080-based packaging cell lines which produce Moloney murin e leukemia virus cores with envelope glycoproteins of either amphotrop ic murine leukemia virus (FLYA13 line) or cat endogenous virus RD114 ( FLYRD18 line) are described. Direct comparison with previous retrovira l packaging systems indicated that 100-fold-higher titers of helper-fr ee recombinant viruses were released by the FLYA13 and FLYRD18 lines.