Our Research

COVID-19

Coronavirus disease 2019 (COVID-19) is causes by systemic acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the virus-induced aberrant, chronic inflammatory response leading to widespread lung damage and inflammation (pneumonia, acute respiratory distress syndrome [ARDS]). Based upon our lab’s expertise and research on virus-induced inflammatory responses, we successfully received funding from the NIH with Dr. Diego Restrepo to explore the role of SARS-Co-V2 in the loss of sense of smell and taste, the ability of TRPM5+ cells to modulate virus-induced inflammation and neuroinvasiveness, and the ability of a drug that blocks ion channels to decrease virus replication and associated inflammation. In addition, we are analyzing COVID-19 blood samples to identify prognostic biomarkers and virus-associated gene expression pathways that can be targeted with therapies.

Varicella zoster virus (VZV) and stroke

Multiple epidemiological studies show that individuals with VZV reactivation manifesting as herpes zoster (shingles) have an increased risk of stroke that declines over the following year. Furthermore, virus reactivation without rash can also produce stroke. VZV-associated stroke may be caused by direct infection of cerebral arteries (vasculopathy), virus-induced hypercoagulability, and/or inflammation that may disrupt pre-existing atherosclerotic plaques or other vascular lesions. The best characterized mechanisms have been established for VZV vasculopathy with information gleaned from clinical cases, virus-infected arteries obtained at autopsy from VZV vasculopathy patients, and VZV-infected cerebrovascular cells in vitro. Our lab has characterized features that would assist in the recognition, diagnosis, and treatment of VZV vasculopathy. In addition, we found that during reactivation from trigeminal and upper cervical ganglia, VZV can be directly deposited to the cerebral arteries. Within the arteries, VZV-infected cells evade immune clearance (interfering with JAK-STAT signaling, decreasing MHC class I), secrete matrix metalloproteinases that weaken the vessel wall, secrete cytokines to recruit inflammatory cells that then persist (downregulation of programmed death ligand 1) - overall disrupting vessel wall integrity (aneurysm, hemorrhage) and leading to accumulation of myofibroblasts in the lumen (ischemia).

We continue to investigate why virus persists in arteries (recurrent reactivation with deposition, ineffective clearance?), why there is such widespread, chronic inflammation with or without detection of viral antigens (epigenetic alterations in cerebrovascular cells leading to continuous production of proinflammatory cytokines?), and how VZV vasculopathy presents in the extracranial circulation (giant cell arteritis, granulomatous arteritis of the aorta).

Clinical Pearls

  1. Treat zoster individuals with oral antivirals to decrease risk of subsequent stroke.

  2. Because of conflicting reports, it is not yet clear if zoster vaccination (Zostavax or Shingrix) prevents central nervous manifestations of VZV reactivation.

  3. Diagnosis of VZV vasculopathy can be made by temporal relationship to zoster rash, as well as the presence of intrathecal synthesis of anti-VZV antibodies (best test) or VZV DNA in cerebrospinal fluid (CSF), particularly if rash not present.

Varicella zoster virus and other inflammatory manifestations

Because VZV can reactivate from sensory/autonomic ganglia and because every organ system receives innervation from these ganglia allowing direct viral spread along immunoprivileged nerve fibers, VZV can produce multi-system disease, including ganglionitis (postherpetic neuralgia, subset of burning mouth syndrome), myelitis, keratitis, retinitis, pneumonitis, myocarditis, gastritis, pancreatitis, and hepatitis. As Program Director of a National Institute on Aging Program Project, Dr. Nagel works closely with Drs. Randall Cohrs and Ravi Mahalingam to determine mechanisms of VZV-induced persistent inflammation leading to these diseases using temporal artery biopsies from patients with giant cell arteritis and a simian varicella zoster-rhesus macaque model. Overall, knowledge gleaned from VZV-induced aberrant inflammation and identification of therapeutic targets can be applied to other human DNA and RNA viruses that may use similar mechanisms.

Clinical Pearls

  1. VZV disease can occur with or without rash.

  2. For CNS VZV disease, diagnose with rash if present, intrathecal synthesis of anti-VZV antibodies, and/or the presence of VZV DNA in CSF.

  3. For peripheral VZV disease, diagnose with rash if present, 4-fold increase in anti-VZV IgG titers in serum compared to baseline (difficult since baseline titers usually not known), and/or the presence of anti-VZV IgM (positive if recent reactivation; negative if VZV not involved or if VZV infection is chronic).

Varicella zoster virus, amyloid-beta, amylin, and amyloid

Herpes zoster (shingles) is associated with an increased risk of dementia and neovascular macular degeneration and also leads to a decline in glycemic control in individuals with diabetes mellitus (type 2 diabetes). These 3 diseases share the pathological feature of amyloid deposition in brain (amyloid-beta and/or amylin aggregates), retina (amyloid-beta aggregates), and pancreas (amylin aggregates), respectively. Thus, we are investigating how VZV can contribute to the toxic amyloid burden in these diseases. We found that VZV-infected primary human spinal astrocytes contain intracellular amyloid-beta, amylin, and amyloid that is absent in uninfected cells; furthermore, VZV-infected cells produced an extracellular environment that catalyzed aggregation of amyloidogenic peptides, likely in part due to amyloidogenic viral peptides. Similarly, we found that compared to non-zoster individuals, individuals with acute zoster had amyloidogenic factors in plasma (Bubak et al., Journal of Neurovirology, in press).

Ongoing projects determine if an amyloidogenic environment is present in CSF and arteries during VZV vasculopathy, in VZV-infected retinal pigment epithelial cells in the context of macular degeneration, in VZV-infected pancreatic beta cells in the context of diabetes, and in CSF/serum/pancreas of simian varicella virus-infected rhesus macaques.

Development of antiviral nanoparticles using a guinea pig model of vzv infection

In collaboration with Dr. Tom Anchordoquy and funding from the Skaggs School of Pharmacy and Pharmaceutical Sciences Therapeutic Innovation Grant (ALSAM), Dr. Nagel’s lab is developing nanoparticles that preferentially bind to peripheral blood mononuclear cells and that express a plasmid encoding siRNAs that knock down essential VZV genes. In parallel, the lab is optimizing a guinea pig model of VZV infection to test the efficacy of the anti-VZV nanoparticles in reducing virulence. With successful completion of this project, these antiviral nanoparticles can be modified to target other blood-borne viruses to decrease hematogenous dissemination to organs and decrease mosquito-borne transmission.

development of induced pluripotent stem cell-derived motor neurons to study viral motor neuron disease

In collaboration with Dr. Holger Russ, we are developing an induced pluripotent stem-cell-derived motor neuron model to study the pathogenesis of viral myelitis/myelopathy.

herpesvirus infection and cognitive impairment

The role of herpesvirus infection in cognitive impairment and dementia is controversial. Our lab is investigating whether herpesviruses, in conjunction with other host and environmental factors, can contribute to the pathological features of dementia in the context of accelerating cerebrovascular disease, amyloid deposition, tauopathy, and neuroinflammation. Our models use FFPE tissue from Alzheimer’s disease olfactory bulb, tract, and hippocampus; an HSV-1 murine model of infection; a VZV guinea pig model of infection; an SVV rhesus macaque model of infection; and primary human CNS cells.

Neurokinin-1 receptor antagonists to treat vzv central nervous system disease

Our lab identified a novel function of neurokinin-1 receptor (NK-1R) in VZV infection. Specifically, VZV-infected cells aberrantly translocate NK-1R to the nucleus, distinctly different from cytoplasmic localization of NK-1R after binding of endogenous ligand, substance P. Nucelear NK-1R in VZV-infected cells is associated with multiple phenotypic changes, including formation of lamellipodia, promoting viral spread. Importantly, NK-1R antagonists (aprepitant and rolapitant, clinically used as anti-emetics) inhibit VZV virulence in multiple cell types. These repurposed drugs provide a potentially new class of antiviral agents against VZV infection.