Lyme neuroborreliosis: improvements of the laboratory diagnosis and a survey of epidemiological and clinical features in Denmark 1985-1990

Abstract

Lyme neuroborreliosis (LNB) has within the last few years become one of the most frequent neuroinfections. This thesis is based on 7 publications which have two main topics: (i) to improve and develop laboratory methods for routine diagnosis of LNB, (ii) to generate epidemiological data for LNB and to achieve a descriptive clinical delimitation of this disease. Laboratory diagnosis in Lyme borreliosis is based on detection of a Borrelia burgdorferi (Bb) specific immune response. Up till now serological assays have not achieved a sufficient diagnostic specificity and sensitivity. This is partly due to the use of test antigens consisting of all proteins of the spirochete including broadly cross-reacting antigens. In order to improve diagnostic antibody detection we isolated an immunodominant structural protein of Bb, the motility organelle the flagellum. The use of native, morphologically intact flagella as test antigen in ELISA led to a significantly increased diagnostic specificity, and, especially in early disease, to an improved diagnostic sensitivity. Reservations regarding the use of only one out of the over 100 proteins of Bb as a diagnostic antigen probe are groundless. The early as well as the late immune response to Bb always includes antibodies to the flagellum. The Bb flagellum is as a test antigen not completely Bb specific. Compared with all other antigen preparations however, the flagellum is at present the best compromise, if a sensitive and specific routine serology is requested. The diagnostic performance of specific IgM detection was improved with a mu-capture ELISA, which used biotin labelled Bb flagella. Compared to conventional indirect ELISA this technique avoids false positive results due to IgM rheumatoid factor interference and false low or false negative results due to IgG competition for the test antigen. The antibody response in Bb infection develops slowly. Patients with LNB can be antibody negative in blood up to 6-8 weeks after onset of neurological symptoms. Longstanding but seronegative disease in untreated patients is unlikely to occur. Expectations of further improvement of Lyme borreliosis serology focuses presently on the performance of the outer surface protein (Osp) C as a test antigen and on the genus specific domain of the Bb flagellin. Theoretically this region constitutes the best candidate for a better test antigen either as a recombinant or a synthetic peptide. In LNB a prominent Bb specific intrathecal antibody response develops.(ABSTRACT TRUNCATED AT 400 WORDS)