Spinal fluid antibody profile against bacteria demonstrates intrathecal antibody production in demyelinating diseases

This study follows work establishing multiple sclerosis (MS) microbial candidates from RNA sequencing of human brain samples. A subsequent study demonstrated anti-microbial immune responses in cerebrospinal fluid (CSF) of patients with demyelinating diseases (DD) and other neurologic diseases (OND). We aim to expand evidence for specific anti-microbial responses in CSF of patients with DD. CSF IgG ELISA assays were developed from 20 bacteria identified as MS microbial candidates. CSF responses from patients with DD (N = 16) and OND (N = 8) were determined using commercial CSF as positive and negative controls. CSF reactivity was expressed as ELISA Index (EI) values against each of the lysates. Antibody Index (AI) values were determined by comparing CSF reactivity and diluted serum samples with equivalent IgG concentrations. AI values > 1.5 were considered positive, 1.0-1.49 equivocal, and < 1.0 negative. Most samples from both groups displayed reactivity across all 20 lysates, with an overall rate of 87.8%. CSF EI values were highest against Haemophilus, Aggregatibacter, and Streptococcus, lowest against Veillonella, Fusobacterium, and Alistipes. Twenty-five percent of subjects with DD and 13% with OND had AI > 1.5 to at least one lysate. Clustering of AI values from four DD samples against Bacteroides and Lactobacillus was observed. This serological study shows reactivity against multiple bacteria in CSF from patients with primary DD including MS and OND. Elevated AI in four DD and one OND subject provides evidence for specific intrathecal antibody production in these patients. KEY MESSAGES: This study measured humoral immune responses in the cerebrospinal fluid (CSF) of human subjects with multiple sclerosis (MS) and other demyelinating diseases against 20 candidate bacteria previously identified by sequencing of diseased human brain tissue. The method described here involves diluting CSF to match the serum IgG concentrations, running an ELISA, and calculating an Antibody Index (AI). The methods described here are improved by directly measuring banked CSF and serum IgG concentrations in the laboratory. Several subjects with demyelinating diseases clustered strongly for responses against Bacteroides, Lactobacillus, Akkermansia, and Alistipes, found in the normal flora in the human gut and female genital tract.