In our study, an absence of observed viral particles in LGTVinfected ISE6 cells did not allow for confirmation of previously reported differences seen with TBEV [35] between virus particle location in mammalian versus arthropod cells. However, we have augmented this earlier published work by reporting the 3D structure of acutely infected tick cells. By ET, the proliferating membranes are revealed to be a complex anastomosing system of membranes almost certainly derived from ER. In the Semliki Forest virus replicon system containing Kunjin virus proteins, expression of a single flavivirus protein, NS4A, can induce the membrane rearrangements [22] , and similar results have been reported for Dengue virus NS4A [57] , but it is uncertain at this time if this role can be assigned to NS4A in the TBFV. Future investigation is in progress to determine which TBFV protein or combination of proteins cause membrane rearrangement in mammalian and tick cells.