Figure 1.

Three potential mechanisms for restricted patterns of RABV spread in the CNS. Spread restricted to preferentially synaptically-connected input cells could be achieved through specific expression of viral receptors on input cell terminals, direct transfer of viruses from post-synaptic cells to pre-synaptic cells without ever needing to bud into the extracellular space, and through non-productive infection of nearby glial cells. A combination of these mechanisms may also influence the apparent labeling specificity.