Erber et al. demonstrated, in various experiments, high selectivity of this system for surface expression of EphB4 in transfected cell clones, rodent specificity of ecotropic viruses, no infection of human SF126 glioma cells by the used retrovirus, EphB4 overexpression in transfected cell clones, and increased EphB4 tyrosine phosphorylation compared to control viruses [10]. This evidence concerns the gene EPHB4 and infection.