Ulnar nerve inoculation of poliovirus in bonnet monkey: a new primate model to investigate neurovirulence.

A new monkey model of poliovirus neurovirulence has been developed avoiding the currently used intraspinal injection route which traumatizes the spinal cord. Poliovirus type 1 (0.1 ml) was inoculated into the ulnar nerve of bonnet monkeys (Macaca radiata) at the right elbow. Five monkeys were inoculated with 10(7) TCID of LSc/2ab (Sabin vaccine strain); none developed any illness. Limb paralysis, clinically resembling spinal poliomyelitis in children, developed in all four monkeys given greater than or equal to 10(5) TCID50 of Mahoney strain, and in three of four monkeys given 10(4) or 10(3) TCID50. Higher functions and cranial nerves were not affected. Paralysis occurred more frequently in the lower limbs (11 limbs in seven monkeys) than in upper limbs (six limbs in seven monkeys). The incubation period, from inoculation to onset of paralysis, ranged from 5 to 12 days. Further progression of paralysis to other limbs occurred within 2 to 6 days. No illness developed in two monkeys given 10(2) TCID50 of Mahoney virus. All monkeys given LSc/2ab and those given greater than 10(2) TCID50 Mahoney virus developed humoral antibody response; however, infection of the gastrointestinal tract was detected by virus isolation from throat swabs and stools only in monkeys given Mahoney virus, but not in those given LSc/2ab. Thus, intraneural spread of Mahoney virus to the spinal cord, neurovirulence of Mahoney but not of LSc/2ab and retrograde gastrointestinal infection with Mahoney but not with LSc/2ab are the features of this experimental model.