Neuronal Autoantibodies in Adults After Community-Acquired Bacterial Meningitis.

Background and objectives: Long-term cognitive impairment is observed in 14%-32% of patients surviving community-acquired bacterial meningitis. We hypothesized that the impairment might be linked to secondary immune activation due to the development of neuronal autoantibodies, similar to postinfectious autoimmune encephalitis after viral encephalitis.

Methods: In this cross-sectional observational study, we included adult patients from a prospective, nationwide cohort study of community-acquired bacterial meningitis in the Netherlands, the MeninGene study. The presence of neuronal autoantibodies was evaluated in follow-up serum samples at 7 days, at 3 months, or over a year. Immunohistochemistry on complete rat brain slices was performed for the initial screening. If positive or ambiguous, immunocytochemistry using live primary rat hippocampal neurons and cell-based assays expressing extracellular targets were performed; immunoblots were used for intracellular targets.

Results: In total, 118 patients were included, of whom 24 of 100 (24%) had cognitive impairment and 14 of 109 (13%) had focal neurologic deficits at discharge. Causative pathogens were Streptococcus pneumoniae in 98 patients (83%), Neisseria meningitidis in 4 (3%), and other pathogens in 6 (5%); in 10 patients (9%), no causative pathogen was identified. Two of 118 patients (2%) had neuronal autoantibodies in follow-up serum: 1 had leucine-rich glioma inactivated 1 antibodies, and 1 had unspecified antibodies. None of the patients was positive for NMDA receptor antibodies.

Discussion: There was no clear evidence of postinfectious autoimmune encephalitis after bacterial meningitis. Therefore, acute brain damage caused by the infection itself seems to be the most plausible explanation for long-term cognitive impairment and neurologic disabilities.