Acute childhood neuroborreliosis with a selective immune response to a low molecular weight protein expressed by Borrelia garinii.

In patients with Lyme borreliosis the early immune response to Borrelia burgdorferi is usually directed against the flagellin (41 kD) antigen. However, the sera of 4 out of 12 children with typical early neuroborreliosis contained antibodies to two low molecular weight proteins of 19 and 23 kD. These antibodies were demonstrated in serological tests using Borrelia garinii as antigen source. B. garinii is the species of B. burgdorferi sensu lato associated with neuroborreliosis. In contrast serological tests using B. burgdorferi sensu stricto, associated with arthritis, or using VS461 strains (B. afzelii), associated with chronic skin disease, were false-negative. Monospecific rabbit sera raised against the 23 kD protein of B. garinii strain W1 detected the 23 kD epitope in B. garinii isolates only. Results of serological tests for Lyme borreliosis may depend on the infecting strain and on the choice of the strain used as antigen source for diagnostic tests. The attending physician should interpret serological test results with care and rely on astute clinical judgement.