The DD Env confers enhanced utilisation of THTR1 homologues. MLV (FeLV) lacZ pseudotypes bearing the A (Glasgow-1), C (Sarma), DD, ND or NN Envs were plated onto MDTF cells expressing the feline (fe), human (hu) or porcine (po) THTR1 homologues, human FLVCR1 or human FLVCR2. 72 hours post-infection, cells were stained for expression of lacZ and counted manually. Values represent the mean +/− SEM of three independent experiments. The increase in titre associated with the DD mutation upon feline, human or porcine THTR1 is statistically significant in comparison with A (Glasgow-1) (unpaired T test, p < 0.05).