Interferon in cerebrospinal fluid. A marker for viral persistence of canine distemper encephalomyelitis

Interferon (IFN) was measured in serum and cerebrospinal fluid (CSF) of dogs after experimental (intranasal) infection with different strains of virulent canine distemper virus (CDV). Viral strains employed produced neurological changes in dogs that range from acute inflammatory to subacute, delayed demyelinating encephalomyelitis. With few exceptions, first appearance of serum-IFN correlated with the first elevated body temperature 4 days post-infection (p.i.). By 16 days p.i. IFN had disappeared from the serum of all infected dogs. In contrast, IFN was constantly detectable in CSF in dogs with CDV infection of the central nervous system (CNS). It was first detected 5 days p.i., was continuously detectable during the variable preclinical phase and into the period when signs of acute or delayed encephalomyelitis were evident. Dogs from which CDV would be retrieved from CNS tissue at necropsy always had CSF-IFN (up to 56 days p.i.). In contrast, dogs that recovered from infection, substantiated at necropsy by minimal, resolving CNS lesions and non-detectable virus, had IFN in CSF demonstrable for only a brief post-inoculation period. CSF-IFN appears to be a valid marker for CDV persistence in the canine CNS and may have broader applications.