Targeted gene transfer to lymphocytes using murine leukaemia virus vectorspseudotyped with spleen necrosis virus envelope proteins

In contrast to murine leukaemia virus (MLV)-derived vector systems, vector particles derived from the avian spleen necrosis virus (SNV) have been succ essfully targeted to subsets of human cells by envelope modification with a ntibody fragments (scFv). However, an in vivo application of the SNV vector system in gene transfer protocols is hampered by its lack of resistance ag ainst human complement. To overcome this limitation we established pseudoty ping of MLV vector particles produced in human packaging cell lines with th e SNV envelope (Env) protein. Three variants of SNV Env proteins differing in the length of their cytoplasmic domains were all efficiently incorporate d into MLV core particles. These pseudotype particles infected the SNV perm issive cell line D17 at titers of up to 10(5) IU/ml. A stable packaging cel l line (MS4) of human origin released MLV(SNV) pseudoype vectors that were resistant against human complement inactivation. To redirect their tropism to human T cells, MS4 cells were transfected with the expression gene encod ing the scFv 7A5 in fusion with the transmembrane domain (TM) of the SNV En v protein, previously shown to retarget SNV vector particles to human lymph ocytes. MLV(SNV-7A5)-vector particles released from these cells were select ively infectious for human T cell lines. The data provide a proof of princi ple for targeting MLV-derived vectors to subpopulations of human cells thro ugh pseudotyping with SNV targeting envelopes.