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.