Ivan Jelcic

Broadly neutralizing human monoclonal JC polyomavirus VP1–specific antibodies as candidate therapeutics for progressive multifocal leukoencephalopathy

Human monoclonal antibodies broadly neutralize multiple PML-causing JC polyomavirus variants. Opportunity knocks for JC polyomavirus therapy JC polyomavirus (JCPyV) can be found in the urinary tract in most adults, resulting in a persistent but asymptomatic infection. However, in immunocompromised individuals, JCPyV opportunistically infects the brain, resulting in the debilitating and frequently fatal disease progressive multifocal leukoencephalopathy (PML). No treatments are currently available for PML, but two papers now identify and exploit a gap in the immune response to JCPyV. Ray et al. report that JCPyV strains found in the cerebrospinal fluid of PML patients have mutations that prevent antibody neutralization and that these blind spots can be overcome with vaccination. Jelcic et al. suggest that broadly neutralizing antibodies derived from a patient who recovered from PML may fill this gap. In immunocompromised individuals, JC polyomavirus (JCPyV) may mutate and gain access to the central nervous system resulting in progressive multifocal leukoencephalopathy (PML), an often fatal opportunistic infection for which no treatments are currently available. Despite recent progress, the contribution of JCPyV-specific humoral immunity to controlling asymptomatic infection throughout life and to eliminating JCPyV from the brain is poorly understood. We examined antibody responses against JCPyV major capsid protein VP1 (viral protein 1) variants in the serum and cerebrospinal fluid (CSF) of healthy donors (HDs), JCPyV-positive multiple sclerosis patients treated with the anti–VLA-4 monoclonal antibody natalizumab (NAT), and patients with NAT-associated PML. Before and during PML, CSF antibody responses against JCPyV VP1 variants show “recognition holes”; however, upon immune reconstitution, CSF antibody titers rise, then recognize PML-associated JCPyV VP1 variants, and may be involved in elimination of the virus. We therefore reasoned that the memory B cell repertoire of individuals who recovered from PML could be a source for the molecular cloning of broadly neutralizing antibodies for passive immunization. We generated a series of memory B cell–derived JCPyV VP1–specific human monoclonal antibodies from HDs and a patient with NAT-associated PML–immune reconstitution inflammatory syndrome (IRIS). These antibodies exhibited diverse binding affinity, cross-reactivity with the closely related BK polyomavirus, recognition of PML-causing VP1 variants, and JCPyV neutralization. Almost all antibodies with exquisite specificity for JCPyV, neutralizing activity, recognition of all tested JCPyV PML variants, and high affinity were derived from one patient who had recovered from PML. These antibodies are promising drug candidates for the development of a treatment of PML.

Mechanisms of immune escape in central nervous system infection with neurotropic JC virus variant

Symptomatic infections of the central nervous system (CNS) with JC polyomavirus (JCV) usually occur as a result of immunocompromise and manifest as progressive multifocal leukoencephalopathy (PML) or granule cell neuronopathy (GCN). After immune reconstitution, some of these cases may show long‐term persistence of JCV and delayed clinical improvement despite inflammation.

Memory B Cells Activate Brain-Homing, Autoreactive CD4+ T Cells in Multiple Sclerosis

Summary Multiple sclerosis is an autoimmune disease that is caused by the interplay of genetic, particularly the HLA-DR15 haplotype, and environmental risk factors. How these etiologic factors contribute to generating an autoreactive CD4+ T cell repertoire is not clear. Here, we demonstrate that self-reactivity, defined as “autoproliferation” of peripheral Th1 cells, is elevated in patients carrying the HLA-DR15 haplotype. Autoproliferation is mediated by memory B cells in a HLA-DR-dependent manner. Depletion of B cells in vitro and therapeutically in vivo by anti-CD20 effectively reduces T cell autoproliferation. T cell receptor deep sequencing showed that in vitro autoproliferating T cells are enriched for brain-homing T cells. Using an unbiased epitope discovery approach, we identified RASGRP2 as target autoantigen that is expressed in the brain and B cells. These findings will be instrumental to address important questions regarding pathogenic B-T cell interactions in multiple sclerosis and possibly also to develop novel therapies.

Phenotypic and functional complexity of brain-infiltrating T cells in Rasmussen encephalitis

Objective: To characterize the brain-infiltrating immune cell repertoire in Rasmussen encephalitis (RE) with special focus on the subsets, clonality, and their cytokine profile. Methods: The immune cell infiltrate of freshly isolated brain tissue from RE was phenotypically and functionally characterized using immunohistology, flow cytometry, and T-cell receptor (TCR) deep sequencing. Identification of clonally expanded T-cell clones (TCCs) was achieved by combining flow cytometry sorting of CD4+ and CD8+ T cells and high-throughput TCR Vβ-chain sequencing. The most abundant brain-infiltrating TCCs were isolated and functionally characterized. Results: We found that CD4+, CD8+, and also γδ T cells infiltrate the brain tissue in RE. Further analysis surprisingly revealed that not only brain-infiltrating CD8+ but also CD4+ T cells are clonally expanded in RE. All 3 subsets exhibited a Tc1/Th1 phenotype characterized by the production of interferon (IFN)-γ and TNF. Broad cytokine profiling at the clonal level showed strong production of IFN-γ and TNF and also secretion of interleukin (IL)-5, IL-13, and granzyme B, both in CD4+ and CD8+ T cells. Conclusions: CD8+ T cells were until now considered the central players in the immunopathogenesis of RE. Our study adds to previous findings and highlights that CD4+ TCCs and γδ T cells that secrete IFN-γ and TNF are also involved. These findings underline the complexity of T-cell immunity in RE and suggest a specific role for CD4+ T cells in orchestrating the CD8+ T-cell effector immune response.

Multifocal CNS demyelination after octreotide treatment for metastatic meningioma

Octreotide (Sandostatin® Novartis, Berne, Switzerland) is a omatostatin analog approved for the treatment of acromegaly nd gastrointestinal syndromes of hormone hypersecretion in witzerland. Since somatostatin receptors (SSTR) are present on ost meningiomas, octreotide has been suggested as a salvage reatment for patients with recurrent meningioma with presence f somatostatin receptors confirmed by octreotide SPECT or PET tudies [1,2]. We report the case of a patient with metastatic omatostatin receptor-positive meningioma who developed mulifocal CNS demyelination after octreotide therapy.

Intrathecal production of antibodies against JC virus and other viruses in multiple sclerosis and natalizumab-associated progressive multifocal leukoencephalopathy

and CNS, we compared the heavy chain (VH) transcriptome from CSF plasmablastswith the VH transcriptome of peripheral B cell populations in 7 NMO patients. CSF Ig transcriptome libraries were generated from isolated CSF plasmablasts by single-cell sorting, reverse-transcription polymerase chain reaction (RT-PCR), and DNA sequencing. Recombinant antibodies were generated from paired heavyand light chain sequences and tested for AQP4-reactivity by a cell binding assay. Peripheral B cells were FACS sorted into naïve (CD19+CD20+CD27− IgD+), memory (CD19+CD20+CD27+), plasmablast (CD19+CD20−CD27+ IgD−CD38++), and triple-negative (CD19+CD20−CD27−IgD−) B cell populations. VH transcriptomes were subsequently generated by RT-PCR and next generation deep sequencing (Illumina MiSeq) using barcoded primers equipped with unique molecular identifiers (UMIs). In 5 out of 7 NMO patients, we found an overlap of clonally related B cells across the blood–brain-barrier. On average, 5% of the CSF Ig transcriptome sequences could be linked to blood Ig transcriptome sequences. The overlap between clonally related B cells could be established between CSF plasmablasts and peripheral blood memory B cells, triple-negative B cells, and plasmablasts. VH sequences of AQP4-specific CSF antibodies were observed in each of these peripheral B cell compartments; however, the pattern of somatic hypermutation in peripheral blood memory and triple negative B cells was more closely related to their CSF counterparts and for some VH sequences were nearly identical. The proportion of peripheral triple-negative B cells in NMO was significantly elevated when compared to MS patients and healthy controls. Our findings indicate that an exchange of B cells occurs between the peripheral and CNS compartment in NMO. AQP4-specific memory and triple negative B cells may be a critical source of CNS AQP4-IgG producing plasmablasts and play a role in the initiation of NMO lesions. Monitoring these specific peripheral blood populations may prove useful for assessing disease activity and therapy.