β-Endorphin alters a viral induced central nervous system disease in normal mice but not in nude mice

A single intracerebroventricular injection of 100 ng of β-endorphin altered the course of the central nervous system (CNS) infection of a temperature-sensitive mutant of vesicular stomatitis virus (VSV), tsG31-KS5. When mice were administered β-endorphin and then 24 h later infected intracerebrally with tsG31-Ks5 VSV, 70% of the animals died within 8 days of infection. In comparison, less than 10% of the animals had died after 21 days when infected with tsG31-KS5 VSV alone. When mice were injected with β-endorphin and tsG31-KS5 VSV simultaneously, or with β-endorphin 21 days after infection, the more aggressive clinical disease was not observed. Superficially, the more lethal disease induced by β-endorphin appeared to be a result of a mild hypothermia caused by the neuropeptide. β-Endorphin, however, did not influence the disease in nude (nu/nu) mice even though their core temperatures were reduced to an extent similar to that of BALB/c (+/+) mice, implicating the involvement of T lymphocytes in the alteration of the course of infection in normal mice.