Engineered recombinant retroviruses

A recombinant retrovirus comprising:

• (a) a viral envelope comprising (i) one or more mutated viral envelope glycoproteins that retain fusogenic activity and lack cognate receptor binding activity and (ii) a non-viral membrane-bound tropism polypeptide, and
• (b) a recombinant retroviral vector comprising a polynucleotide encoding a promoter operably linked to a polynucleotide encoding one or more engineered antigen receptors;
• wherein the retroviral vector is engineered or derived from a retrovirus selected from the group consisting of:
• an alpharetrovirus genome, a betaretrovirus genome, a gammaretrovirus genome, a deltaretrovirus genome, an epsilonretrovirus genome, a simiispumavirus genome, a bovispumavirus genome, an equispumavirus genome, a felispumavirus genome, and a prosimiispumavirus genome.