RESEARCH Open Access

Single amino acid substitution (G42E) in the receptor binding domain of mouse mammary Furthermore, the expression of human TfR1, in contrast to mouse TfR1, did not enhance the susceptibility of Konstantoulas et al. Retrovirology (2015) 12:43 DOI 10.1186/s12977-015-0168-2Institute of Virology, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, AustriaMMTV-resistant Chinese hamster ovary cells. Thus, human TfR1 is dispensable for infection and another cell surface molecule mediates the MMTV entry into human cells. Conclusion: Taken together, our data explain the mechanism enabling MMTV to form ‘host-range variants ’ in non-murine cells that has been known for a long time, the basis of which remained obscure. Our findings may expand our understanding of how viruses gain capability to cross species-specific barriers to infect new hosts