The role of human endogenous retroviruses (HERVs) in disease pathogenesis is unclear. We show that HERV-K is activated in a subpopulation of patients with sporadic amyotrophic lateral sclerosis (ALS) and that its envelope (env) protein may contribute to neurodegeneration. The virus was expressed in cortical and spinal neurons of ALS patients, but not in neurons from control healthy individuals. Expression of HERV-K or its env protein in human neurons caused retraction and beading of neurites. Transgenic animals expressing the env gene developed progressive motor dysfunction accompanied by selective loss of volume of the motor cortex, decreased synaptic activity in pyramidal neurons, dendritic spine abnormalities, nucleolar dysfunction, and DNA damage. Injury to anterior horn cells in the spinal cord was manifested by muscle atrophy and pathological changes consistent with nerve fiber denervation and reinnervation. Expression of HERV-K was regulated by TAR (trans-activation responsive) DNA binding protein 43, which binds to the long terminal repeat region of the virus. Thus, HERV-K expression within neurons of patients with ALS may contribute to neurodegeneration and disease pathogenesis.

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This is the first long-term follow-up of patients who discontinued natalizumab. We did not observe a clinical, radiographic, or immunologic rebound phenomenon after discontinuation of natalizumab therapy.

Purpose Brentuxiumab vedotin (BV) is an anti-CD30 monoclonal antibody-drug conjugate approved in 2011 for treating anaplastic large cell and Hodgkin lymphomas. The product label indicates that three BV-treated patients developed progressive multifocal leukoencephalopathy (PML), a frequently fatal JC-virus induced central nervous system infection. Prior immunosuppressive therapy and compromised immune systems were postulated risk factors. We report 5 patients who developed BV-associated PML, including two immunocompetent patients. Patients Case information was obtained from clinicians (four patients) or a Food and Drug Administration database (one patient). Results All five patients had lymphoid malignancies. Two patients with cutaneous T-cell lymphomas had not previously received chemotherapy. PML developed after a median of three BV doses (range, 2 to 6) and within a median of 7 weeks following BV initiation (range, 3 to 34 weeks). Presenting findings included aphasia, dysarthria, confusion, hemiparesis, and gait dysfunction; JC virus in cerebrospinal fluid (two patients), or CNS biopsy (three patients); and brain MRI scans with white matter abnormalities (five patients). Four patients died a median of 8 weeks (range, 6 to 16 weeks) after PML diagnosis. The sole survivor developed immune reconstitution inflammatory syndrome. Conclusion PML can develop after a few BV doses and within weeks of BV initiation. Clinicians should be aware of this syndrome, particularly when neurologic changes develop following BV initiation. The decision to administer BV to patients with indolent cutaneous lymphomas should be based on consideration of risk-benefit profiles and of alternative options.