A DEFECTIVE RETROVIRAL VECTOR ENCODING HUMAN INTERFERON-ALPHA-2 CAN TRANSDUCE HUMAN LEUKEMIC-CELL LINES

Using the LXSN backbone, a defective retroviral vector (LISN) was cons tructed that encodes the human interferon (IFN)-alpha 2 (hIFN-alpha 2) gene and the neomycin resistance gene; the hIFN-alpha 2 gene was clon ed from human placental genomic DNA. High titers of the LISN retroviru s wereproduced by the amphotropic packaging cell line GP+envAM12. LISN is able to infect three human hematopoietic and leukemic cell lines: K562, LAMA-84, and TF-1. G418-resistant cells were detected in a simil ar proportion after infection with either the LISN retroviral vector o r the LnLSN retroviral vector (encoding the nlsLacZ gene instead of hI FN-alpha 2), suggesting that hIFN-alpha 2 does not inhibit (or only pa rtially inhibits) the production of retroviral particles by the packag ing cell line and the infection of human cells. LISN-infected cells ex press and secrete hIFN-alpha 2 as demonstrated by Northern blot analys is of poly(A)(+) RNA, detection of the intracellular protein by fluore scence-activated cell sorter analysis, and detection of secreted hIFN- alpha in cell supernatants using an enzyme-linked immunosorbent assay. Retrovirally produced hIFN-alpha 2 is biologically active, as demonst rated by the partial inhibition of the growth of K562 and TF-1, the mo dulation of the expression of cell surface antigens, the induction of the (2'-5') oligoadenylate synthetase, and, for LAMA-84, the down-modu lation of the BCR-ABL protein. We conclude that the infection of human leukemic cell lines with a retroviral vector encoding hIFN-alpha 2 is feasible and induces the expected biological effects. This experiment al model will be useful in investigating the possibility of transducin g normal and leukemic cells and hematopoietic progenitors and in deter mining the consequences of the autocrine production of hIFN-alpha 2 on the behavior of these cells.