Immunochemical features of a case of progressive rubella panencephalitis

Progressive rubella panencephalitis (PRP), a slowly progressive and fatal central nervous system (CNS) disorder due to rubella virus, is characterized by high cerebrospinal fluid (CSF) levels of immunoglobulins, oligoclonal bands and high CSF:serum rubella antibody titre ratios. Sera, CSF and neutral extracts of brain, spleen, lymph node and kidney obtained at autopsy from a case were analysed for immunoglobulin isotype and content by enzyme linked immunosorbent assays. Comparable titres of rubella specific IgA and IgG were found in sera and CSF, but accounted for a disproportionate amount of the isotype specific immunoglobulins of CSF (0.19%, 14.0%) as compared to serum (0.02%, 0.69%). The percentage of isotype specific immunoglobulins were not increased in extracts of most visceral tissues compared to serum, however, rubella specific IgA and IgG were disproportionately increased in extracts from most regions of brain sampled (1-60-fold and 8-27-fold respectively). No rubella specific IgM could be conclusively demonstrated in any specimen. Immunoprecipitation studies showed that the IgG reacted with the major glycoproteins (gp62, gp47-56 complex) and non-glycosylated polypeptide (p38) of radiolabelled rubella virions and infected cell lysates. These studies support the conclusion that a major portion of the rubella specific antibody is produced within the CNS of patients with PRP.