The new alpharetrovirus-based particles are suitable for high efficiency of transiently transducing animal cells. e.g. human or murine cells, and which efficiently introduce coding and non-coding RNA contained in the alpharetrovirus-based particles into target cells The alpharetrovirus-based particles also provide for high efficiency of the activity and/or integrity of the RNA that is introduced into the animal cells, as the particles protect the incoming RNA from degradation during entry. The transferred RNA can be of non-coding nature (e.g. single guide (sg) RNA. short-hairpin (sh) RNA. micro RNA. or long non-coding (Inc) RNA. or the RNA may encode proteins or peptides. e.g. receptors. transcription factors. cellular enzymes, antigens for use in vaccination, gene/protein therapy and/or gene editing nucleases, recombinases and transposases.

The invention provides retroviral envelope glycoproteins in which the cytoplasmic C-terminal tail (CTT) from N-terminus to C-terminus comprises or consists of a T-domain and an R-domain, wherein the R-domain is truncated from its C-terminus, and hybrid glycoproteins and retroviral, especially alpharetroviral, lentiviral or gammaretroviral vector particles containing the glycoprotein. The glycoproteins target the SLC1A5 receptor for target cell entry.