Immunoglobulins in the cerebrospinal fluid: changes during acute viral encephalitis in mice

The development and pathogenesis of immunoglobulin changes in the CSF in acute encephalitis were studied in mice infected with Sindbis virus. Three phases of immunoglobulin changes were noted. 1) During the first 2 days when virus replication in the brain is maximal, few changes were seen in the CSF. 2) At the time of maximal meningeal inflammation, 3 to 5 days after infection, there was a transudation of protein from serum into CSF. 3) During the period of recovery, there was evidence of a local immune response within the CNS. CSF concentrations of all immunoglobulins became increased compared with normal mice and compared with the concentration of albumin, whereas serum immunoglobulin levels remained essentially unchanged. The largest proportionate increase was in IgA. There was no evidence of increased immunoglobulin transfer from serum to CSF by using iodinated immunoglobulins. Comparable amounts of virus-specific IgG and IgA were present in the CSF, whereas serum antibody was primarily IgG. It is concluded that the local immune response to viral encephalitis in mice involves the production of virus-specific IgA as well as IgG.