Attempts to induce chronic experimental allergic neuritis in strain 13 and Hartley guinea pigs.

An attempt has been made to develop a model of chronic experimental allergic neuritis (EAN) using juvenile and adult inbred (Strain 13) and Hartley guinea pigs sensitized with peripheral nerve in complete Freund's adjuvant. Animals were followed clinically for periods ranging from 2 to 44 weeks postinoculation and then sacrificed for light and electron microscopy. Out of a total of 39 animals, 16 showed either clinical signs or had histopathologic changes. The remaining 23 guinea pigs were free of any disease. The animals' age at inoculation and strain did not seem to affect either the clinical course or ultimate histopathologic changes. The 7 animals that had clinical EAN displayed signs ranging from weight loss and soiling to quadriparesis (one animal). The histologic changes consisted of meningeal and perivascular inflammation as well as peripheral nervous system (PNS) and central nervous system demyelination and remyelination. An interesting abnormality seen the nerve roots of several animals was the proliferation of Schwann cells around remyelinated PNS fibers reminiscent of the "onion-bulb" formations seen in human hypertrophic neuropathies. Because of the lack of ongoing demyelination, onion-bulb formation appeared in this case to be a secondary proliferation of Schwann cells after a single primary episode of demyelination. It is concluded from the present study that despite some interesting histopathologic changes, the animals studied were largely resistant both to acute as well as chronic EAN.