Effect of neonatal thymectomy on experimental subacute sclerosing panencephalitis in adult hamsters.

Syrian golden hamsters were thymectomized in the first 48 h of life, raised, and then inoculated intracerebrally with the HBS strain of hamster-adapted subacute sclerosing panencephalitis virus when over 12 weeks old. Two groups soon become apparent; one group showed progressive neurological susmptoms and the other group remained healthy. The sick hamsters became moribund between days 8 and 17 postinoculation, and they had large amounts of complete virus in their brains, no antibodies to measles virus in their sera, and a demonstrated lack of thymus tissue. Pathological changes in the central nervous system included marked focal necrosis, numerous giant and inclusion-bearing cells, and slight inflammation. The healthy animals, killed at day 22 or 35 postinoculation, contained no central nervous system virus, moderate amounts of measles antibody in their sera, minimal or absent central nervous system pathology, and histologically identifiable remnants of thymus tissue. These studeis indicate that, in the hamster, the immune system is essential in recovering from central nervous system measles infection and that the antibody response to measles probably requires helper T lymphocytes to develop. Im the absence of antibody to measles, the virus did not undergo modification to a cell-associated state, as noted in previous hamster studies and in human subacute aclerosing panencephalitis. This model system may be useful for passive transfer studies to further clarify the effect of the n vivo immune response to acute and persistent central nervous system measles virus infections9