Pathogen Specificity and Autoimmunity Are Distinct Features of Antigen-Driven Immune Responses in Neuroborreliosis

Abstract

Neuroborreliosis (NB) is a chronic infectious disease of the central nervous system (CNS) caused by a tick-borne spirochete, Borrelia burgdorferi. In addition to direct effects of the causative infectious agent, additional immunity-mediated mechanisms are thought to play a role in the CNS pathology of NB. In order to further understand the involvement of humoral immune mechanisms in NB, we dissected the intrathecal antibody responses down to the single-plasma-cell level. Starting with single-cell reverse transcription-PCR of fluorescence-activated cell sorter-sorted cerebrospinal fluid plasma cells from an NB patient, we identified expanded clones and resurrected the antigen specificity of their secreted antibodies through recombinant expression of the correctly paired immunoglobulin heavy-and light-chain genes as monoclonal antibodies (MAbs). As expected, we found specificity for the causative infectious agent, B. burgdorferi, among the clonally expanded plasma cell (cePC)-derived MAbs. However, from an independent cePC of the same patient, we could derive MAbs specific for human CNS myelin, without detectable cross-reactivity with B. burgdorferi antigens. While reactivity against B. burgdorferi is a known feature of humoral immune responses in NB, we show (i) that immune responses specific for self antigens may be a distinct feature of CNS infections independent of pathogen reactivity and (ii) that humoral autoimmunity in NB (since found in cePC) is the result of a truly antigen-driven immune response. Our findings indicate that in NB mechanisms may be at play that induce distinct immune responses specific for pathogen and self antigens independent from "molecular mimicry

Clonally expanded plasma cells in the cerebrospinal fluid of MS patients produce myelin‐specific antibodies

“…Myelin reactivity of MS-mAb appeared independent of the disease course and treatment, and could even be found in a patient with optic neuritis (CIS1), which is deemed to be a very early form of MS. While this finding fits the generally accepted hypothesis of MS being a demyelinating autoimmune disease involving potentially pathogenic humoral immune responses, recent data from our laboratory suggest that the myelin reactivity shown in the current study is not specific for MS: Antibodies from cePC from the CSF of a patient with neuroborreliosis included reactivities with Borrelia burgdorferi, the causative pathogen, but also with CNS myelin [26].…”

“…PCR-amplified Ig H and L chain genes from each plasma cell clone were used to recombinantly reconstruct the antigen specificity of antibodies expressed by cePC preserving the original Ig H and L chain pairings of individual plasma cells. This approach has been demonstrated to faithfully resurrect pathogen-specific antibodies from individual plasma cells from patients with subacute sclerosing panencephalitis [25] and borreliosis, and to maintain the original antibody affinity [26].…”

NMDAR encephalitis: passive transfer from man to mouse by a recombinant antibody

“…All four treatment‐naive patients with recent onset anti‐NMDAR encephalitis in the current study showed intrathecal B‐cell and plasma cell accumulation and intrathecal production of NMDAR‐specific IgG. Moreover, using single‐cell RT‐PCR of FACS‐sorted CD138 + CSF plasma cells and recombinant antibody technology,19, 21 we identified expanded clones and were able to obtain seven different rhuMab (SSM1‐7) from intrathecal cePc of one of the anti‐NMDAR encephalitis patients. Ig sequences showed varying numbers of mutations from published germline sequences, indicating antigen‐driven expansion and ongoing somatic hypermutations.…”

“…To elucidate whether cePc are the actual source of the intrathecal autoantibody response, we cloned paired immunoglobulin heavy‐ and light‐chain variable gene regions from cePc essentially as previously described 19, 21. PEI mediated cotransfection of IgG‐HC and matching Ig‐LC expression vectors into FreeStyle 293‐F cells were carried out to produce recombinant monoclonal antibodies in vitro.…”

“…Single CD138 + plasma cells were sorted in individual microtiter wells and stored at −80°C until use. RT‐PCR amplification of IgG heavy‐ and light‐chain transcripts from single cells was performed as described previously21 with minor modifications. PCR amplicons were purified from 1% agarose gel using QIAquick PCR purification kit and subsequently sequenced with the respective constant region primers at GATC Biotech (Germany).…”