Streptavidin Paramagnetic Particles Provide a Choice of Three Affinity-Based Capture and Magnetic Concentration Strategies for Retroviral Vectors

Three strategies have been designed to concentrate infectious retroviral vectors from the supernatants of human- (HT1080) and murine- (NIH 3T3) based packaging cells. Streptavidin-conjugated paramagnetic particles in conjunction with (i) antibodies directed against murine fibronectin, (ii) biotinylated lectins, or (iii) biotin-modified packaging cell-surface proteins allow affinity-mediated magnetic concentration of retroviral vectors. Retroviral titers (assayed by colony formation of human myeloid K562 cells) are increased by 1–4 × 103-fold after volume reductions of only 125-fold. Using these procedures, preparations of 5 × 108 cfu/ml are routinely made from relatively low-titer (2Darling D. Low-speed centrifugation of retroviral vectors absorbed to a particulate substrate: A highly effective means of enhancing retroviral titre.Gene Ther. 2000; 7: 914-923Crossref PubMed Scopus (14) Google Scholar, 3Signas C. Nucleotide sequence of the gene for fibronectin-binding protein from Staphylococcus aureus: Use of this peptide sequence in the synthesis of biologically active peptides.Proc. Natl. Acad. Sci. USA. 1989; 86: 699-703Crossref PubMed Scopus (309) Google Scholar, 4Jönsson K. Signas C. Muller H-P. Lindberg M. Two different genes encode fibronectin binding proteins in Staphylococcus aureus: The complete nucleotide sequence and characterization of the second gene.Eur. J. Biochem. 1991; 202: 1041-1048Crossref PubMed Scopus (295) Google Scholar, 5Jordan-Sciutto K.L. Logan T.J. Norton P.A. Derfoul A. Dodge G.R. Hall D.J. Reduction in fibronectin expression and alteration in cell morphology are coincident in NIH3T3 cells expressing a mutant E2F1 transcription factor.Exp. Cell Res. 1997; 236: 527-536Crossref PubMed Scopus (14) Google Scholar × 105 cfu/ml) starting material. High-titer (paramagnetic) retroviral vector preparations can be used for magnetic field-dependent retroviral infection in vitro. Magnetic field-dependent localization such as this may enable the in vivo administration of formulations that concentrate retroviral infection to the required target tissues and organs.