What role does retrograde axonal transport play in poliovirus pathogenesis?

• A. It transports the virus from the gut to the liver
• B. It allows the virus to enter the CNS from the neuromuscular junction
• C. It degrades the viral particle
• D. It has no role in pathogenesis

Answer: (B)

Retrograde axonal transport is the mechanism that carries certain neurotropic viruses from peripheral sites of infection toward the central nervous system. In poliovirus pathogenesis, after the virus replicates in the gut, it can infect motor neurons at the neuromuscular junction and hijack the neuron’s transport system to travel up the axon to the spinal cord. This ascent allows the virus to reach anterior horn motor neurons, where infection leads to their destruction and the flaccid paralysis seen in poliomyelitis. So this transport route is essential for CNS invasion by poliovirus. It does not describe gut-to-liver spread, nor does it involve degrading the viral particle, and it clearly plays a central role in disease.