Human-derived virus-like particles (heVLPs), comprising a membrane comprising a phospholipid bilayer with one or more HERV-derived envelope proteins on the external side; one or more HERV-derived GAG proteins in the heVLP core, and a cargo molecule, e.g., a biomolecule and/or chemical cargo molecule, disposed in the core of the heVLP on the inside of the membrane, wherein the heVLP does not comprise a gag protein, except for gag proteins that are encoded in the human genome or gag proteins that are encoded by a consensus sequence that is derived from gag proteins found in the human genome, and methods of use thereof for delivery of the cargo molecule to cells.

The present disclosure provides methods and compositions for genetically modifying lymphocytes and related methods that include genetically modifying T cells and/or NK cells. The methods use replication incompetent recombinant retroviral particles that comprise a pseudotyping element on their surface and optionally a membrane-bound T cell activation element, such as an anti-CD3, and encode one or more engineered signaling polypeptides that can include a lymphoproliferative element, and/or a chimeric antigen receptor (CAR). The methods can include contacting PBMCs with replication incompetent recombinant retroviral particles for various exemplary time periods, such as less than 24 hours or in some illustrative embodiments less than 15 minutes. In some aspects, the present disclosure provides methods and compositions for genetically modifying lymphocytes, for example T cells and/or NK cells, in whole blood or a component thereof. In some embodiments a lymphodepletion filter assembly is used before or after forming a reaction mixture where lymphocytes are contacted with recombinant retroviral particles in a closed system, to genetically modify the lymphocytes.

The present invention relates nucleic acid molecules and concatemers containing spacer sequences useful for the efficient packaging of viral particles so as to minimize the incorporation of contaminant nucleic acids into these vectors, as well as methods of producing such viral particles.