SARS-CoV-2 Invasion and Pathological Links to Prion Disease

Meta-analysis of the serum/plasma proteome identifies significant associations between COVID-19 with Alzheimer's/Parkinson's diseases

In recent years, we have seen the widespread devastations and serious health complications manifested by COVID-19 globally. Although we have effectively controlled the pandemic, uncertainties persist regarding its potential long-term effects, including prolonged neurological issues. To gain comprehensive insights, we conducted a meta-analysis of mass spectrometry-based proteomics data retrieved from different studies with a total of 538 COVID-19 patients and 523 healthy controls. The meta-analysis revealed that top-enriched pathways were associated with neurological disorders, including Alzheimer's (AD) and Parkinson's disease (PD). Further analysis confirmed a direct correlation in the expression patterns of 24 proteins involved in Alzheimer's and 23 proteins in Parkinson's disease with COVID-19. Protein-protein interaction network and cluster analysis identified SNCA as a hub protein, a known biomarker for Parkinson's disease, in both AD and PD. To the best of our knowledge, this is the first meta-analysis study providing proteomic profiling evidence linking COVID-19 to neurological complications.

Rapid progression of probable Creutzfeldt-Jakob disease with concomitant COVID-19 infection

A previously healthy man in his 80s was admitted to a district general hospital with rapidly progressing dementia, gait abnormalities and myoclonus alongside COVID-19 infection. Investigations showed mild elevation of C-reactive protein and neutrophils, unremarkable CT head and mildly raised protein in cerebrospinal spinal fluid (CSF). Brain MRI revealed bilateral cortical and striatal diffusion restriction and electroencephalogram (EEG) findings showed diffuse activity slowing with high amplitude sharp/slow-wave complexes. He was diagnosed with probable sporadic Creutzfeldt-Jakob disease (CJD) and management prioritised comfort and care. He passed away two weeks following admission and a mere 8 weeks after the first onset of symptoms.We present the first documented case of probable CJD with concomitant COVID-19 infection in the UK. We identified six other cases worldwide identified in our literature review. These cases suggest a role of COVID-19 in the rapid progression of CJD and add to the growing evidence of its neuroinflammatory role in other forms of neurodegenerative diseases.

Prion Disease After COVID-19: A Case Report

BACKGROUND Prion disease (PrD) is one of the rapidly progressive dementias. It typically requires several diagnostic criteria to fulfill a probable diagnosis, as definite diagnosis is based on isolated brain biopsy. There has been much debate on a possible infectious etiology of PrD. Viral infections are commonly pathologic in most neurodegenerative conditions. In PrD, misfolded proteins can be contagious and act as infective proteins, regardless of the pathologic agent. There is evidence that COVID-19 can result in neurologic manifestations, and neurodegeneration has been reported in the literature. There are several case reports describing parkinsonism after COVID-19, with Parkinson's disease in particular noted in COVID-19. Few cases of PrD were reported after COVID-19 infection. We identified 1 case of PrD in the setting of COVID-19 at our hospital. CASE REPORT We report the case of a 62-year-old man admitted to Mount Sinai Queens Hospital Center, who presented with rapidly progressive dementia along with difficulty walking and myoclonus. All workup results were negative. He underwent MRI brain, but results were not revealing. Due to the high clinical suspicion, CSF protein 14-3-3 testing was ordered and was positive. Clinically, he experienced worsening neurological function after having been COVID-19-positive on admission. The case fulfilled the probable diagnostic criteria for diagnosing PrD. The patient continued to deteriorate and died due to the rapid progression of his condition. CONCLUSIONS Our case demonstrates the potential correlation of COVID with neurodegenerative conditions, especially prion disorders. While such cases are highly likely to be due to COVID-19, there is no definite evidence beyond coincidental findings. Future studies might be required to establish this correlation.

Long COVID as a Tauopathy: Of "Brain Fog" and "Fusogen Storms"

Long COVID, also called post-acute sequelae of SARS-CoV-2, is characterized by a multitude of lingering symptoms, including impaired cognition, that can last for many months. This symptom, often called "brain fog", affects the life quality of numerous individuals, increasing medical complications as well as healthcare expenditures. The etiopathogenesis of SARS-CoV-2-induced cognitive deficit is unclear, but the most likely cause is chronic inflammation maintained by a viral remnant thriving in select body reservoirs. These viral sanctuaries are likely comprised of fused, senescent cells, including microglia and astrocytes, that the pathogen can convert into neurotoxic phenotypes. Moreover, as the enteric nervous system contains neurons and glia, the virus likely lingers in the gastrointestinal tract as well, accounting for the intestinal symptoms of long COVID. Fusogens are proteins that can overcome the repulsive forces between cell membranes, allowing the virus to coalesce with host cells and enter the cytoplasm. In the intracellular compartment, the pathogen hijacks the actin cytoskeleton, fusing host cells with each other and engendering pathological syncytia. Cell-cell fusion enables the virus to infect the healthy neighboring cells. We surmise that syncytia formation drives cognitive impairment by facilitating the "seeding" of hyperphosphorylated Tau, documented in COVID-19. In our previous work, we hypothesized that the SARS-CoV-2 virus induces premature endothelial senescence, increasing the permeability of the intestinal and blood-brain barrier. This enables the migration of gastrointestinal tract microbes and/or their components into the host circulation, eventually reaching the brain where they may induce cognitive dysfunction. For example, translocated lipopolysaccharides or microbial DNA can induce Tau hyperphosphorylation, likely accounting for memory problems. In this perspective article, we examine the pathogenetic mechanisms and potential biomarkers of long COVID, including microbial cell-free DNA, interleukin 22, and phosphorylated Tau, as well as the beneficial effect of transcutaneous vagal nerve stimulation.

Endogenous miRNA-Based Innate-Immunity against SARS-CoV-2 Invasion of the Brain

The severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2), the causative agent of COVID-19, possesses an unusually large positive-sense, single-stranded viral RNA (ssvRNA) genome of about ~29,903 nucleotides (nt). In many respects, this ssvRNA resembles a very large, polycistronic messenger RNA (mRNA) possessing a 5'-methyl cap (m7GpppN), a 3'- and 5'-untranslated region (3'-UTR, 5'-UTR), and a poly-adenylated (poly-A+) tail. As such, the SARS-CoV-2 ssvRNA is susceptible to targeting by small non-coding RNA (sncRNA) and/or microRNA (miRNA), as well as neutralization and/or inhibition of its infectivity via the human body's natural complement of about ~2650 miRNA species. Depending on host cell and tissue type, in silico analysis, RNA sequencing, and molecular-genetic investigations indicate that, remarkably, almost every single human miRNA has the potential to interact with the primary sequence of SARS-CoV-2 ssvRNA. Individual human variation in host miRNA abundance, speciation, and complexity among different human populations and additional variability in the cell and tissue distribution of the SARS-CoV-2 angiotensin converting enzyme-2 (ACE2) receptor (ACE2R) appear to further contribute to the molecular-genetic basis for the wide variation in individual host cell and tissue susceptibility to COVID-19 infection. In this paper, we review recently described aspects of the miRNA and ssvRNA ribonucleotide sequence structure in this highly evolved miRNA-ssvRNA recognition and signaling system and, for the first time, report the most abundant miRNAs in the control superior temporal lobe neocortex (STLN), an anatomical area involved in cognition and targeted by both SARS-CoV-2 invasion and Alzheimer's disease (AD). We further evaluate important factors involving the neurotropic nature of SARS-CoV-2 and miRNAs and ACE2R distribution in the STLN that modulate significant functional deficits in the brain and CNS associated with SARS-CoV-2 infection and COVID-19's long-term neurological effects.