The four entry proteins gD, gB, gH and gL are sufficient for infection from the extracellular environment, but efficient infection by cell-to-cell transfer additionally requires glycoproteins gE and gI [17], which are non-essential in tissue culture, but essential for in vivo infection [18] adding further weight to the importance of cell-to-cell spread in the host. Here, GNAI1 is linked to infection.