Immunological diagnosis in viral infections of the central nervous system: course of antibody titres against homo- and heterologous viruses.

In clinical cases suspected for viral encephalitis or meningoencephalitis, the estimation of virus-specific antibodies especially in liquor requires high sensitivity as well as specificity. With enzyme immunoassays the sensitivity in detecting antibodies has increased compared to e.g., complement fixation tests. This report concerns the determination of virus-specific antibodies with a commercial enzyme-linked immunosorbent assay (ELISA) in paired liquor/serum samples of four patients with encephalitis or meningoencephalitis. Up to six virus-specific antibodies of the IgG and IgM classes have been determined [herpes simplex virus (HSV), varicella-zoster virus (VZV), cytomegalovirus, mumps virus, measles virus, and rubella virus]. Additionally, serum samples from several patients suffering, or recovered from, diseases caused by HSV and VZV without CNS involvement have been included as controls. The results showed that besides the virus-specific antibody development (IgG and IgM) against the leading virus, i.e., principally concerned in the disease manifestation assumed to be primarily causing the disease, virus-specific antibodies of the IgG and IgM class against a heterologous virus (e.g., VZV) could also be measured with substantial titers. "Cross-reacting" antibodies to both HSV and VZV with the ELISA only appeared and were present in cases where the infection mainly affected the CNS: no such immunological "cross-reactivity" was observed in serum of individuals in "clinically silent" stages of both HSV and VZV infections. The same situation with no measurable "cross-reacting" antibodies was found in cases of acute HSV or VZV diseases where the CNS was not involved. These findings have been discussed with respect to the findings of common antigens, especially between HSV and VZV, and with respect to an unspecific stimulation of immunocompetent cells.