The bacterial origin of mitochondria has been a widely accepted as an event that occurred about 1.45 billion years ago and endowed cells with internal energy producing organelle. Thus, mitochondria have traditionally been viewed as subcellular organelle as any other - fully functionally dependent on the cell it is a part of. However, recent studies have given us evidence that mitochondria are more functionally independent than other organelles, as they can function outside the cells, engage in complex "social" interactions, and communicate with each other as well as other cellular components, bacteria and viruses. Furthermore, mitochondria move, assemble and organize upon sensing different environmental cues, using a process akin to bacterial quorum sensing. Therefore, taking all these lines of evidence into account we hypothesize that mitochondria need to be viewed and studied from a perspective of a more functionally independent entity. This view of mitochondria may lead to new insights into their biological function, and inform new strategies for treatment of disease associated with mitochondrial dysfunction.

• Keywords
• SARS-CoV-2, exosomes, independent mitochondria, mitochondria, sensory mitochondria, sentinel mitochondria, tunneling nanotubes, virus,
• MeSH
• Genes, Bacterial * MeSH
• Humans MeSH
• Mitochondria * MeSH
• Quorum Sensing MeSH
• Virion MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH

The incidence of infections from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiologic agent for coronavirus disease 2019 (COVID-19), has dramatically escalated following the initial outbreak in China, in late 2019, resulting in a global pandemic with millions of deaths. Although the majority of infected patients survive, and the rapid advent and deployment of vaccines have afforded increased immunity against SARS-CoV-2, long-term sequelae of SARS-CoV-2 infection have become increasingly recognized. These include, but are not limited to, chronic pulmonary disease, cardiovascular disorders, and proinflammatory-associated neurological dysfunction that may lead to psychological and neurocognitive impairment. A major component of cognitive dysfunction is operationally categorized as "brain fog" which comprises difficulty concentrating, forgetfulness, confusion, depression, and fatigue. Multiple parameters associated with long-term neuropsychiatric sequelae of SARS-CoV-2 infection have been detailed in clinical studies. Empirically elucidated mechanisms associated with the neuropsychiatric manifestations of COVID-19 are by nature complex, but broad-based working models have focused on mitochondrial dysregulation, leading to systemic reductions of metabolic activity and cellular bioenergetics within the CNS structures. Multiple factors underlying the expression of brain fog may facilitate future pathogenic insults, leading to repetitive cycles of viral and bacterial propagation. Interestingly, diverse neurocognitive sequelae associated with COVID-19 are not dissimilar from those observed in other historical pandemics, thereby providing a broad and integrative perspective on potential common mechanisms of CNS dysfunction subsequent to viral infection. Poor mental health status may be reciprocally linked to compromised immune processes and enhanced susceptibility to infection by diverse pathogens. By extrapolation, we contend that COVID-19 may potentiate the severity of neurological/neurocognitive deficits in patients afflicted by well-studied neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease. Accordingly, the prevention, diagnosis, and management of sustained neuropsychiatric manifestations of COVID-19 are pivotal health care directives and provide a compelling rationale for careful monitoring of infected patients, as early mitigation efforts may reduce short- and long-term complications.

• Keywords
• COVID-19, Central nervous system, SARS-CoV-2, anxiety, brain fog, cognitive impairment, depression, long COVID, microglia, mitochondria, neuroinflammation, neuropsychiatric disease,
• MeSH
• Central Nervous System MeSH
• COVID-19 * complications   MeSH
• Humans MeSH
• Neurodegenerative Diseases * MeSH
• Pandemics MeSH
• Disease Progression MeSH
• SARS-CoV-2 MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH

Mitochondrial DNA (mtDNA) heteroplasmy is the dynamically determined co-expression of wild type (WT) inherited polymorphisms and collective time-dependent somatic mutations within individual mtDNA genomes. The temporal expression and distribution of cell-specific and tissue-specific mtDNA heteroplasmy in healthy individuals may be functionally associated with intracellular mitochondrial signaling pathways and nuclear DNA gene expression. The maintenance of endogenously regulated tissue-specific copy numbers of heteroplasmic mtDNA may represent a sensitive biomarker of homeostasis of mitochondrial dynamics, metabolic integrity, and immune competence. Myeloid cells, monocytes, macrophages, and antigen-presenting dendritic cells undergo programmed changes in mitochondrial metabolism according to innate and adaptive immunological processes. In the central nervous system (CNS), the polarization of activated microglial cells is dependent on strategically programmed changes in mitochondrial function. Therefore, variations in heteroplasmic mtDNA copy numbers may have functional consequences in metabolically competent mitochondria in innate and adaptive immune processes involving the CNS. Recently, altered mitochondrial function has been demonstrated in the progression of coronavirus disease 2019 (COVID-19) due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Accordingly, our review is organized to present convergent lines of empirical evidence that potentially link expression of mtDNA heteroplasmy by functionally interactive CNS cell types to the extent and severity of acute and chronic post-COVID-19 neurological disorders.

• Keywords
• COVID-19, Central nervous system, Gut microbiome, Immune response, Mitochondrial DNA, SARS-CoV-2,
• MeSH
• COVID-19 complications   genetics   immunology   metabolism   MeSH
• Heteroplasmy genetics   MeSH
• Immunity MeSH
• Humans MeSH
• DNA, Mitochondrial genetics   MeSH
• Mitochondria metabolism   MeSH
• Nervous System Diseases complications   genetics   immunology   metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• DNA, Mitochondrial MeSH

Recent studies have shown a significant level of T cell immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in convalescent coronavirus disease 2019 (COVID-19) patients and unexposed healthy individuals. Also, SARS-CoV-2-reactive T memory cells occur in unexposed healthy individuals from endemic coronaviruses that cause the 'common cold.' The finding of the expression of adaptive SARS-CoV-2-reactive T memory cells in unexposed healthy individuals may be due to multiple cross-reactive viral protein targets following previous exposure to endemic human coronavirus infections. The opinion of the authors is that determination of protein sequence homologies across seemingly disparate viral protein libraries may provide epitope-matching data that link SARS-CoV-2-reactive T memory cell signatures to prior administration of cross-reacting vaccines to common viral pathogens. Exposure to SARS-CoV-2 initiates diverse cellular immune responses, including the associated 'cytokine storm'. Therefore, it is possible that the intact virus possesses a required degree of conformational matching, or stereoselectivity, to effectively target its receptor on multiple cell types. Therefore, conformational matching may be viewed as an evolving mechanism of viral infection and viral replication by an evolutionary modification of the angiotensin-converting enzyme 2 (ACE2) receptor required for SARS-CoV-2 binding and host cell entry. The authors propose that convalescent memory T cell immunity in individuals with mild or asymptomatic SARS-CoV-2 infection may result from an evolutionarily adapted immune response to coronavirus and the 'common cold'.

• MeSH
• Angiotensin-Converting Enzyme 2 genetics   MeSH
• Asymptomatic Infections * MeSH
• Immunity, Cellular genetics   MeSH
• COVID-19 blood   diagnosis   immunology   virology   MeSH
• Epitopes, T-Lymphocyte genetics   immunology   MeSH
• Immunogenicity, Vaccine MeSH
• Immunologic Memory genetics   MeSH
• Virus Internalization MeSH
• Humans MeSH
• Evolution, Molecular MeSH
• Common Cold immunology   prevention & control   virology   MeSH
• Antibodies, Viral MeSH
• Virus Replication genetics   immunology   MeSH
• Rhinovirus genetics   immunology   MeSH
• SARS-CoV-2 immunology   pathogenicity   MeSH
• Sequence Homology MeSH
• Severity of Illness Index MeSH
• T-Lymphocyte Subsets immunology   MeSH
• T-Lymphocytes immunology   MeSH
• Viral Proteins genetics   immunology   MeSH
• Viral Vaccines administration & dosage   immunology   MeSH
• Cross Reactions genetics   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• ACE2 protein, human MeSH Browser
• Angiotensin-Converting Enzyme 2 MeSH
• Epitopes, T-Lymphocyte MeSH
• Antibodies, Viral MeSH
• Viral Proteins MeSH
• Viral Vaccines MeSH

Since the initial reports of coronavirus disease 2019 (COVID-19) in China in late 2019, infections from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have spread rapidly, resulting in a global pandemic that has caused millions of deaths. Initially, the large number of infected people required the direction of global healthcare resources to provide supportive care for the acutely ill population in an attempt to reduce mortality. While clinical trials for safe and effective antiviral agents are ongoing, and vaccine development programs are being accelerated, long-term sequelae of SARS-CoV-2 infection have become increasingly recognized and concerning. Although the upper and lower respiratory tracts are the main sites of entry of SARS-CoV-2 into the body, resulting in COVID-19 pneumonia as the most common presentation, acute lung damage may be followed by pulmonary fibrosis and chronic impairment of lung function, with impaired quality of life. Also, increasing reports have shown that SARS-CoV-2 infection involves the central nervous system (CNS) and the peripheral nervous system (PNS) and directly or indirectly damages neurons, leading to long-term neurological sequelae. This review aims to provide an update on the mechanisms involved in the development of the long-term sequelae of SARS-CoV-2 infection in the 3 main areas of lung injury, neuronal injury, and neurodegenerative diseases, including Alzheimer disease, Parkinson disease, and multiple sclerosis, and highlights the need for patient monitoring following the acute stage of infection with SARS-CoV-2 to provide a rationale for the prevention, diagnosis, and management of these potential long-term sequelae.

• MeSH
• Time Factors MeSH
• COVID-19 complications   epidemiology   immunology   virology   MeSH
• Quality of Life MeSH
• Humans MeSH
• Neurodegenerative Diseases diagnosis   epidemiology   immunology   prevention & control   MeSH
• Pandemics MeSH
• Pulmonary Fibrosis diagnosis   epidemiology   immunology   prevention & control   MeSH
• Lung Injury diagnosis   epidemiology   immunology   prevention & control   MeSH
• Disease Progression MeSH
• SARS-CoV-2 immunology   pathogenicity   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Review MeSH