TMBIM4 and infection: Possible explanations are (i) that the viral protein has subtly different properties to the cellular protein and these are advantageous to the virus, (ii) that the induction of cell motility by vGAAP is beneficial to virus spread, (iii) that vGAAP regulates the host response to infection, and (iv) that the level of expression of cellular GAAP in mammalian cells is low, and so expression at higher levels, as observed during virus infection [2], is beneficial.