In one study, protein aggregates from yeast prions were released into a mammalian intercellular cleft and were taken up by the adjacent cell, as opposed to direct cell transfer. This process would be similar to the secretion and transmission of infectious particles through the synaptic cleft between cells of the immune system, as seen in retroviruses. Understanding the routes of intercellular protein aggregate transfer, particularly routes involving clefts is imperative in understanding the progressive spreading of this infection8.