Figure 1

Figure 1. Brain imaging and autopsy findings in a case of chronic Jamestown Canyon virus (JCV) meningoencephalitis in a patient receiving rituximab, Boston, Massachusetts, USA. A) Brain magnetic resonance imaging T2-weighted fluid-attenuated...

A 56-year-old man from New England with a history of mantle cell lymphoma in remission, receiving maintenance rituximab since 2014, had fatigue, arthralgias, and weight loss in summer 2017. He was empirically treated for Lyme disease without improvement, had progressive insomnia and inattention, and was eventually admitted for workup of rapidly progressive dementia in April 2018. On examination, he had impaired arousal and attention (Montreal Cognitive Assessment score 6 of 30). Cranial nerve, tone, strength, sensory, and reflex examinations were normal. Gait was wide-based and slow without ataxia or parkinsonism. Magnetic resonance imaging of the brain showed mild ventriculomegaly attributed to atrophy but was otherwise unremarkable, without contrast enhancement, cortical diffusion restriction, mass lesions, hemorrhage, or infarction (Figure 1). Electroencephalography showed moderate bihemispheric slowing without epileptiform features. CSF from multiple lumbar punctures showed mild lymphocytic pleocytosis (0–22 leukocytes/μL, 83%–98% lymphocytes), elevated total protein (40–116 mg/dL; reference 10–44 mg/dL), and unremarkable glucose (65–78 mg/dL; reference 40–80 mg/dL) (Appendix Table 1). An extensive infectious, autoimmune, and neurodegenerative disease workup was normal (Appendix Table 2).

A CSF sample collected in April 2018 underwent clinical metagenomic next-generation sequencing (mNGS) testing at the University of California–San Francisco (8) and was positive for California encephalitis virus most closely matching JCV, with reads mapping to 2 of the 3 viral genome segments (Appendix Figure 1). Another CSF sample, obtained approximately 3 weeks later in May, was negative for JCV by RT-PCR performed by CDC’s Arboviral Diseases Branch (Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases; Fort Collins, CO, USA); however, concurrent serum JCV RT-PCR was positive. Results of JCV IgM and neutralizing antibody testing were negative for CSF and blood from the samples obtained in May. Concurrent samples had 0% CD20+ circulating lymphocytes (reference 3%–20% lymphocytes), attributed to rituximab treatment, last administered in December 2017.

The patient was treated with intravenous immunoglobulin (total 2 g/kg), followed by a 2-week course of favipiravir, an experimental inhibitor of viral RNA polymerase, without improvement. His mental status deteriorated to a comatose state. He was transitioned to comfort care and died in June 2018, ≈1 year after suspected symptom onset.

At autopsy, the unfixed brain weighed 1,240 g and appeared grossly normal, with no masses, hemorrhage, infarctions, or herniation. Histologic abnormalities were most prominent in the cerebral cortex (particularly frontal and temporal lobes), cerebellum, and hippocampus; milder changes in basal ganglia, thalamus, and brainstem were observed, including severe loss of neurons, diffuse microgliosis with microglial nodules and neuronophagia, and perivascular and parenchymal chronic inflammation (Figure 1). Leptomeninges showed numerous chronic inflammatory cells. No viral inclusions were identified. There was no evidence of lymphoma. Immunohistochemical staining highlighted abundant perivascular, parenchymal, and leptomeningeal T cells with a complete lack of B cells. Formalin-fixed paraffin-embedded brain tissue was positive for JCV by RT-PCR (performed by CDC’s Arboviral Diagnostic and Reference Laboratory); results were negative for immunohistochemistry for flaviviruses and enteroviruses (performed by CDC’s Infectious Diseases Pathology Branch [Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases; Atlanta, GA, USA]).

Figure 2

Figure 2. JCV genome analyses in a case of chronic JCV meningoencephalitis in a patient on rituximab, Boston, Massachusetts, USA. A) Maximum-likelihood phylogenetic tree of the coding region of the JCV small...

Complete or near-complete JCV genomes were recovered from premortem CSF and postmortem cerebellum and cortex tissue (both frozen and formalin-fixed paraffin-embedded) (Table; Appendix Supplementary Methods, Figure 2). Phylogenetic analysis of the small (nucleocapsid) segment showed that sequences from this patient were most closely related to JCV from mosquitoes in Connecticut (Figure 2, panel A) (9). Comparison of JCV genomes between this patient’s CSF, cerebellum, and cortex revealed 27 high-confidence within-patient single-nucleotide polymorphisms (SNPs) (Figure 2, panel B; Appendix Tables 3, 4). For 13 SNPs, the variant present in CSF was different from that in cerebellum and cortex, suggesting evolution over time. For another 4 SNPs, the variant present in cerebellum was different from that in cortex, suggesting compartmentalization. The remaining 10 SNPs could represent either compartmentalization or evolution over time, because only 1 brain tissue (cerebellum or cortex) was sequenced to sufficient depth. Variability was greater in the small segment (nucleocapsid) and medium segment (glycoprotein) than the large segment (polymerase).

We describe an unusual fatal case of chronic JCV encephalitis in a patient who was being treated with rituximab. In contrast to this case, previously described patients with JCV have had acute illness, and JCV infection is rarely fatal (7,10). The neuropathologic findings in this patient, although nonspecific, are similar to those of a cerebellar biopsy from a patient with JCV encephalitis that showed severe loss of Purkinje and granule cells, diffuse microgliosis of the molecular layer, and leptomeningeal inflammation (5).

The lack of distinguishing clinical, radiographic, and pathologic features of JCV underscores the diagnostic utility of clinical mNGS (8). Attributable in part to low incidence and lack of commercially available targeted testing, JCV is often not considered a priori, especially in the setting of chronic progressive neurologic illness. As a further complication, standard clinical testing by serology can be negative in the setting of B-cell–depleting therapy; our patient had negative JCV serologic tests and lack of B lymphocytes by immunohistochemical staining. Similar phenomena have been reported in rituximab-treated patients with other arboviral infections (e.g., Cache Valley orthobunyavirus, Powassan virus, and West Nile virus) who lack detectable antibodies but remain viremic longer than immunocompetent patients, highlighting the importance of nucleic acid–based testing methods (11–13).

In addition to diagnosis, mNGS also provides valuable information about pathogen genomics. We report the unique assembly of a JCV genome from human clinical samples, an important advance in the study of JVC pathogenesis, virus evolution, and differences between the enzootic transmission cycle and human infection (14). The functional importance of the identified SNPs could not be evaluated from the genomic data alone; however, none were associated with alterations of potential N-linked glycosylation sites, cysteine bonds, or the conserved fusion domain (15). One SNP that arose between CSF and brain (small segment gA397G; aT109A) also varied between JCV strains with different neurovirulence in mice, although the functional importance is unknown (4).

Although treatment options for JCV infection are largely unexplored, response to antiviral drugs probably depends on initiating treatment early in the disease course and reaching therapeutic levels in the CSF before extensive neuronal loss. Thus, broad-spectrum molecular assays such as mNGS could potentially lead to earlier treatment with improved outcomes (8).