Body Localization of ACE-2: On the Trail of the Keyhole of SARS-CoV-2

Delivery Routes for COVID-19 Vaccines

The novel coronavirus, SARS-CoV-2, which causes COVID-19, has resulted in a pandemic with millions of deaths. To eradicate SARS-CoV-2 and prevent further infections, many vaccine candidates have been developed. These vaccines include not only traditional subunit vaccines and attenuated or inactivated viral vaccines but also nucleic acid and viral vector vaccines. In contrast to the diversity in the platform technology, the delivery of vaccines is limited to intramuscular vaccination. Although intramuscular vaccination is safe and effective, mucosal vaccination could improve the local immune responses that block the spread of pathogens. However, a lack of understanding of mucosal immunity combined with the urgent need for a COVID-19 vaccine has resulted in only intramuscular vaccinations. In this review, we summarize the history of vaccines, current progress in COVID-19 vaccine technology, and the status of intranasal COVID-19 vaccines. Future research should determine the most effective route for vaccine delivery based on the platform and determine the mechanisms that underlie the efficacy of different delivery routes.

Impact of cytokine storm and systemic inflammation on liver impairment patients infected by SARS-CoV-2: Prospective therapeutic challenges

Coronavirus disease 2019 (COVID-19) is a devastating worldwide pandemic infection caused by a severe acute respiratory syndrome namely coronavirus 2 (SARS-CoV-2) that is associated with a high spreading and mortality rate. On the date this review was written, SARS-CoV-2 infected about 96 million people and killed about 2 million people. Several arguments disclosed the high mortality of COVID-19 due to acute respiratory distress syndrome or change in the amount of angiotensin-converting enzyme 2 (ACE2) receptor expression or cytokine storm strength production. In a similar pattern, hepatic impairment patients co-infected with SARS-CoV-2 exhibited overexpression of ACE2 receptors and cytokine storm overwhelming, which worsens the hepatic impairment and increases the mortality rate. In this review, the impact of SARS-CoV-2 on hepatic impairment conditions we overviewed. Besides, we focused on the recent studies that indicated cytokine storm as well as ACE2 as the main factors for high COVID-19 spreading and mortality while hinting at the potential therapeutic strategies.

Phosphatidylserine is an overlooked mediator of COVID-19 thromboinflammation

A ubiquitous component of cell membrane, phosphatidylserine (PS), is likely to play a major, but as yet unrecognized, role in the thromboinflammation of COVID-19 and other critical illnesses. PS is present in all plasma membranes but is "hidden" on the inner surface by the action of an ATP-requiring enzyme. Failure of PS to be sequestered on the inner surface of cell membranes, release of PS-containing microparticles from cells, or shedding of enveloped viruses allows it to interact with extracellular proteins, including those of the coagulation and complement systems. Detection and quantification of circulating PS is not standardized, and current methodologies have either focused on circulating cellular elements or subcellular plasma components, but not both. PS may also promote thromboinflammation without circulating if expressed on the surface of endothelial cells, a condition that might only be documented if novel imaging techniques are developed. Research into the role of PS in inflammation and coagulation, called here a "procoagulant phospholipidopathy" may provide novel insights and therapeutic approaches for patients with a variety of illnesses.

Neuropathology of COVID-19 (neuro-COVID): clinicopathological update

Coronavirus disease 2019 (COVID-19) is emerging as the greatest public health crisis in the early 21stcentury. Its causative agent, Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2), is an enveloped single stranded positive-sense ribonucleic acid virus that enters cells via the angiotensin converting enzyme 2 receptor or several other receptors. While COVID-19 primarily affects the respiratory system, other organs including the brain can be involved. In Western clinical studies, relatively mild neurological dysfunction such as anosmia and dysgeusia is frequent (~70-84%) while severe neurologic disorders such as stroke (~1-6%) and meningoencephalitis are less common. It is unclear how much SARS-CoV-2 infection contributes to the incidence of stroke given co-morbidities in the affected patient population. Rarely, clinically-defined cases of acute disseminated encephalomyelitis, Guillain-Barré syndrome and acute necrotizing encephalopathy have been reported in COVID-19 patients. Common neuropathological findings in the 184 patients reviewed include microglial activation (42.9%) with microglial nodules in a subset (33.3%), lymphoid inflammation (37.5%), acute hypoxic-ischemic changes (29.9%), astrogliosis (27.7%), acute/subacute brain infarcts (21.2%), spontaneous hemorrhage (15.8%), and microthrombi (15.2%). In our institutional cases, we also note occasional anterior pituitary infarcts. COVID-19 coagulopathy, sepsis, and acute respiratory distress likely contribute to a number of these findings. When present, central nervous system lymphoid inflammation is often minimal to mild, is detected best by immunohistochemistry and, in one study, indistinguishable from control sepsis cases. Some cases evince microglial nodules or neuronophagy, strongly supporting viral meningoencephalitis, with a proclivity for involvement of the medulla oblongata. The virus is detectable by reverse transcriptase polymerase chain reaction, immunohistochemistry, or electron microscopy in human cerebrum, cerebellum, cranial nerves, olfactory bulb, as well as in the olfactory epithelium; neurons and endothelium can also be infected. Review of the extant cases has limitations including selection bias and limited clinical information in some cases. Much remains to be learned about the effects of direct viral infection of brain cells and whether SARS-CoV-2 persists long-term contributing to chronic symptomatology.

Significance of NETs Formation in COVID-19

Severe contagious respiratory disease—COVID-19—caused by the SARS-CoV-2 coronavirus, can lead to fatal respiratory failure associated with an excessive inflammatory response. Infiltration and spread of SARS-CoV-2 are based on the interaction between the virus’ structural protein S and the cell’s receptor–angiotensin-converting enzyme 2 (ACE2), with the simultaneous involvement of human trans-membrane protease, serine 2 (TMPRSS2). Many scientific reports stress the importance of elevated recruitment and activity of neutrophils, which can form extracellular neutrophil traps (NETs) playing a significant role in the mechanism of combating pathogens, in the pathogenesis of COVID-19. Excessive generation of NETs during prolonged periods of inflammation predisposes for the occurrence of undesirable reactions including thromboembolic complications and damage to surrounding tissues and organs. Within the present manuscript, we draw attention to the impact of NET generation on the severe course of COVID-19 in patients with concurrent cardiovascular and metabolic diseases. Additionally, we indicate the necessity to explore not only the cellular but also the molecular bases of COVID-19 pathogenesis, which may aid the development of dedicated therapies meant to improve chances for the successful treatment of patients. We also present new directions of research into medications that display NETs formation regulatory properties as potential significant therapeutic strategies in the progress of COVID-19.

Association of acute disseminated encephalomyelitis (ADEM) and COVID-19 in a pediatric patient

Cases of acute disseminated encephalomyelitis (ADEM) and its hyperacute form, acute hemorrhagic leukoencephalitis (AHLE), have been reported in coronavirus disease 2019 (COVID-19) patients as rare, but most severe neurological complications. However, histopathologic evaluations of ADEM/AHLE pathology in COVID patients are extremely limited, so far having only been reported in a few adult autopsy cases. Here we compare the findings with an ADEM-like pathology in a pediatric patient taken through a biopsy procedure. Understanding the neuropathology may shed informative light on the autoimmune process affecting COVID-19 patients and provide critical information to guide the clinical management.