SARS-CoV-2: Should We Be Concerned about the Nervous System?

Molecular Mechanisms of SARS-CoV-2/COVID-19 Pathogenicity on the Central Nervous System: Bridging Experimental Probes to Clinical Evidence and Therapeutic Interventions

The coronavirus disease 2019 (COVID-19) pandemic, induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has dramatically impacted the global healthcare systems, constantly challenging both research and clinical practice. Although it was initially believed that the SARS-CoV-2 infection is limited merely to the respiratory system, emerging evidence indicates that COVID-19 affects multiple other systems including the central nervous system (CNS). Furthermore, most of the published clinical studies indicate that the confirmed CNS inflammatory manifestations in COVID-19 patients are meningitis, encephalitis, acute necrotizing encephalopathy, acute transverse myelitis, and acute disseminated encephalomyelitis. In addition, the neuroinflammation along with accelerated neurosenescence and susceptible genetic signatures in COVID-19 patients might prime the CNS to neurodegeneration and precipitate the occurrence of neurodegenerative diseases, including Alzheimer's and Parkinson's diseases. Thus, this review provides a critical evaluation and interpretive analysis of existing published preclinical as well as clinical studies on the key molecular mechanisms modulating neuroinflammation and neurodegeneration induced by the SARS-CoV-2. In addition, the essential age- and gender-dependent impacts of SARS-CoV-2 on the CNS of COVID-19 patients are also discussed.

Live Viral Vaccine Neurovirulence Screening: Current and Future Models

Live viral vaccines are one of the most successful methods for controlling viral infections but require strong evidence to indicate that they are properly attenuated. Screening for residual neurovirulence is an important aspect for live viral vaccines against potentially neurovirulent diseases. Approximately half of all emerging viral diseases have neurological effects, so testing of future vaccines will need to be rapid and accurate. The current method, the monkey neurovirulence test (MNVT), shows limited translatability for human diseases and does not account for different viral pathogenic mechanisms. This review discusses the MNVT and potential alternative models, including in vivo and in vitro methods. The advantages and disadvantages of these methods are discussed, and there are promising data indicating high levels of translatability. There is a need to investigate these models more thoroughly and to devise more accurate and rapid alternatives to the MNVT.

Environmental Nanoparticles, SARS-CoV-2 Brain Involvement, and Potential Acceleration of Alzheimer's and Parkinson's Diseases in Young Urbanites Exposed to Air Pollution

Alzheimer's and Parkinson's diseases (AD, PD) have a pediatric and young adult onset in Metropolitan Mexico City (MMC). The SARS-CoV-2 neurotropic RNA virus is triggering neurological complications and deep concern regarding acceleration of neuroinflammatory and neurodegenerative processes already in progress. This review, based on our MMC experience, will discuss two major issues: 1) why residents chronically exposed to air pollution are likely to be more susceptible to SARS-CoV-2 systemic and brain effects and 2) why young people with AD and PD already in progress will accelerate neurodegenerative processes. Secondary mental consequences of social distancing and isolation, fear, financial insecurity, violence, poor health support, and lack of understanding of the complex crisis are expected in MMC residents infected or free of SARS-CoV-2. MMC residents with pre-SARS-CoV-2 accumulation of misfolded proteins diagnostic of AD and PD and metal-rich, magnetic nanoparticles damaging key neural organelles are an ideal host for neurotropic SARS-CoV-2 RNA virus invading the body through the same portals damaged by nanoparticles: nasal olfactory epithelium, the gastrointestinal tract, and the alveolar-capillary portal. We urgently need MMC multicenter retrospective-prospective neurological and psychiatric population follow-up and intervention strategies in place in case of acceleration of neurodegenerative processes, increased risk of suicide, and mental disease worsening. Identification of vulnerable populations and continuous effort to lower air pollution ought to be critical steps.