Ultrahigh frequencies of peripherally matured LGI1- and CASPR2-reactive B cells characterize the cerebrospinal fluid in autoimmune encephalitis

• Published in: Proceedings of the National Academy of Sciences - PNAS 2024-02, Vol.121 (7), p.e2311049121-e2311049121
• Main Authors: Theorell, Jakob, Harrison, Ruby, Williams, Robyn, Raybould, Matthew I J, Zhao, Meng, Fox, Hannah, Fower, Andrew, Miller, Georgina, Wu, Zoe, Browne, Eleanor, Mgbachi, Victor, Sun, Bo, Mopuri, Rohini, Li, Ying, Waters, Patrick, Deane, Charlotte M, Handel, Adam, Makuch, Mateusz, Irani, Sarosh R
• Format: Article
• Language: English
• Subjects: Affinity; Autoantibodies; Autoantigens; Autoimmune diseases; Autoimmune Diseases of the Nervous System; B-cell receptor; Biological Sciences; Cell differentiation; Central nervous system; Cerebrospinal fluid; Contactin; Encephalitis; Glioma; Hashimoto Disease; Humans; Immunoglobulin G; Immunotherapy; Intracellular Signaling Peptides and Proteins; Leucine; LGI1 protein; Lymphocytes; Lymphocytes B; Lymphocytes T; Medicin och hälsovetenskap; Monoclonal antibodies; Neoplasm Recurrence, Local; Receptors; T cell receptors; Ultrahigh frequencies
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.2311049121

Intrathecal synthesis of central nervous system (CNS)-reactive autoantibodies is observed across patients with autoimmune encephalitis (AE), who show multiple residual neurobehavioral deficits and relapses despite immunotherapies. We leveraged two common forms of AE, mediated by leucine-rich glioma inactivated-1 (LGI1) and contactin-associated protein-like 2 (CASPR2) antibodies, as human models to comprehensively reconstruct and profile cerebrospinal fluid (CSF) B cell receptor (BCR) characteristics. We hypothesized that the resultant observations would both inform the observed therapeutic gap and determine the contribution of intrathecal maturation to pathogenic B cell lineages. From the CSF of three patients, 381 cognate-paired IgG BCRs were isolated by cell sorting and scRNA-seq, and 166 expressed as monoclonal antibodies (mAbs). Sixty-two percent of mAbs from singleton BCRs reacted with either LGI1 or CASPR2 and, strikingly, this rose to 100% of cells in clonal groups with ≥4 members. These autoantigen-reactivities were more concentrated within antibody-secreting cells (ASCs) versus B cells ( < 0.0001), and both these cell types were more differentiated than LGI1- and CASPR2-unreactive counterparts. Despite greater differentiation, autoantigen-reactive cells had acquired few mutations intrathecally and showed minimal variation in autoantigen affinities within clonal expansions. Also, limited CSF T cell receptor clonality was observed. In contrast, a comparison of germline-encoded BCRs versus the founder intrathecal clone revealed marked gains in both affinity and mutational distances ( = 0.004 and < 0.0001, respectively). Taken together, in patients with LGI1 and CASPR2 antibody encephalitis, our results identify CSF as a compartment with a remarkably high frequency of clonally expanded autoantigen-reactive ASCs whose BCR maturity appears dominantly acquired outside the CNS.