The disclosure relates to betaretroviruses (genus Betaretrovirus), and recombinant betaretroviral envelope (rENV) protein for use in viral vector platforms, an engineered delivery vehicle and gene therapy, their associated methods of use and manufacture. In particular, the present disclosure provides compositions and methods to tune betavirus envelope proteins such that they target a particular cell surface receptor; i.e., are cell and/or tissue-type specific, allowing for better site-specific transgene delivery and expression.