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SARS-CoV-2 Morphology, Genomic Organisation and Lifecycle
Published in Srijan Goswami, Chiranjeeb Dey, COVID-19 and SARS-CoV-2, 2022
Srijan Goswami, Ushmita Gupta Bakshi
As discussed in Chapter 1, the coronaviruses are classified into four genera: alphacoronavirus, betacoronavirus, gammacoronavirus and deltacoronavirus. SARS-CoV-2, the enveloped virus responsible for COVID-19, belongs to genera betacoronavirus and shares structural similarities with SARS-CoV and MERS-CoV (the other two members of the same genera) (Lu et al., 2020). The genome of coronaviruses consists of positive-sense single-stranded RNA (+ssRNA) and are around 29,881 bp in length (GenBank no. MN908947) with 9860 amino acids (Chen et al., 2020; Wang, 2020). The genome consists of gene sequences encoding structural proteins and non-structural proteins. The electron microscopic analysis of SARS-CoV-2 revealed that it has a spherical body with a diameter of approximately 60 nm to 140 nm and a crown-like spike structure of approximately 9 nm to 12 nm in length (Zhu et al., 2020). These crown-like spike structures are common to all the representative members of the coronavirus family. There are also various kinds of structural proteins that are present on the outer surface of coronaviruses (Astuti & Ysrafil, 2020). SARS-CoV-2 possess four major structural proteins on the outer surface similar to other coronaviruses, namely the spike protein (S), envelope protein (E), membrane protein (M) and nucleocapsid protein (N) (Figure 2.1). Let us now understand each of these four proteins in detail.
Current Epidemiological and Clinical Features of COVID-19; a Global Perspective From China
Published in William C. Cockerham, Geoffrey B. Cockerham, The COVID-19 Reader, 2020
Huilan Tu, Sheng Tu, Shiqi Gao, Anwen Shao, Jifang Sheng
Coronaviruses were first described by Tyrell and Bynoe in 1966, who isolated the viruses from patients suffering from the common cold.6 Tyrell and Bynoe called them coronaviruses because they are spherical virions with a core shell and surface projections resembling a solar corona.7 Coronaviruses are members of the subfamily Coronavirinae in the family Coronaviridae, order Nidovirales. Members of this subfamily were genetically classified into four major genera: Alphacoronavirus, Betacoronavirus, Gammacoronavirus, and Deltacoronavirus.8 Alphacoronaviruses and betacoronaviruses infect only mammals and usually cause respiratory illness in humans and gastroenteritis in animals. The gammacoronaviruses and deltacoronaviruses predominantly infect birds, but some can also infect mammals.9 Six types of coronavirus have been identified in humans (HCoVs), including HCoV-NL63, HCoV-229E, HCoV-OC43, HCoV-HKU1, SARS-CoV, and MERS-CoV. The first two belong to the Alphacoronavirus genus and the latter four to the genus Betacoronavirus.10 SARS-CoV and MERS-CoV can cause severe respiratory syndrome in humans, while the other four human coronaviruses induce only mild upper respiratory diseases in immunocompetent hosts.11,12 Coronaviruses did not attract worldwide attention until the 2003 SARS epidemic, followed by the 2012 MERS outbreak and, most recently, the novel coronavirus pandemic.
Rehabilitation of patients with COVID-19
Published in Expert Review of Respiratory Medicine, 2020
Tiantian Sun, Liyun Guo, Fei Tian, Tiantian Dai, Xiaohong Xing, Junqing Zhao, Qiang Li
Of the four genera in the coronavirus subfamily [1], Alphacoronavirus and Betacoronavirus infect mammals, and Gammacoronavirus and Deltacoronavirus mostly infect birds [2]. Human coronavirus NL63 (HCoV-NL63) and human coronavirus 229E (HCoV-229E) both cause disease in humans and belong to the genus Alphacoronavirus. Human coronavirus OC43 (HCoV-OC43), human coronavirus HKU1 (HCoV-HKU1), severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) belong to the Betacoronavirus genus, of which HCoV-229E, HCoV-OC43, HCoV-NL63, and HCoV-HKU1 are viruses responsible for common colds [3]. Some studies have shown a close relationship between SARS-CoV-2 and the SARS coronavirus that infects bats and to SARS-CoV. However, the change in the minimum receptor-binding domain of the spike glycoprotein of SARS-CoV-2 is more significant, thus enhancing the virus’s ability to spread [4,5,6,7]. It has been reported that the spike glycoprotein of SARS-CoV-2 is more likely to bind to the surface protein of angiotensin-converting enzyme 2 (ACE2). Compared with the SARS virus, the S protein of SARS-CoV-2 has a 10–20 times higher affinity for ACE2, which is mainly distributed throughout the lungs, heart, kidneys, testes, and digestive tract [8,9]. SARS-CoV-2 transmission is mainly via droplets, followed by aerosol and fecal-oral transmission [10,11].
Can the Coronavirus Disease 2019 (COVID-19) Affect the Eyes? A Review of Coronaviruses and Ocular Implications in Humans and Animals
Published in Ocular Immunology and Inflammation, 2020
CoVs belong to the subfamily Coronavirinae, in the family Coronaviridae of the order Nidovirales. CoVs have four known genera: Alphacoronavirus, Betacoronavirus, Gammacoronavirus, and Deltacoronavirus. The CoV name is a derivative from the Latin word corona which means crown. This is due to the characteristic structure of the virus whereby surface projections on the viral envelope gives it an appearance similar to a crown. The virus is a single-stranded positive-sense RNA virus with a genome of around 30 kb in length. This makes them the largest known RNA viruses.8 The RNA genome codes for both structural proteins (SPs) and non-structural proteins (NSPs). All known CoVs share a similar structure made of four main structural proteins: spike (S), membrane (M), envelope (E), and nucleocapsid (N) proteins. Some CoVs also encode special structural and accessory proteins.9 While the exact functions of most accessory proteins are still currently being researched on, it is recognized that the structural proteins aid the viral infection of host cells and subsequent replication. The S-protein is responsible for attachment to host receptors, M protein helps shape the virion particles and binding to nucleocapsid, E-protein plays a role in the assembly and release of particles while N-protein aids with the binding of the genome to a replication-transcription complex which is required for the replication of genomic material.
Broad-spectrum coronavirus antiviral drug discovery
Published in Expert Opinion on Drug Discovery, 2019
Allison L. Totura, Sina Bavari
Highly pathogenic coronaviruses SARS-CoV and MERS-CoV recently emerged into human populations, but other human coronaviruses (HCoVs) including HCoV-OC43, HCoV-229E, HCoV-NL63, and HCoV-HKU1 are estimated to have circulated in human populations for hundreds of years, causing mild respiratory illness to which approximately 5–30% of ‘common colds’ are attributed [7,8]. Within the Coronaviridae family (order Nidovirales) four genera are recognized: alphacoronavirus, betacoronavirus, gammacoronavirus, and deltacoronavirus. The six HCoVs (Table 1) currently identified belong to the genera alphacoronavirus (HCoV-229E and HCoV-NL63) and betacoronavirus (SARS-CoV, MERS-CoV, HCoV-OC43, and HCoV-HKU1). Gammacoronaviruses and deltacoronaviruses have no known viruses that infect humans, but contain important agricultural pathogens of livestock. Epizootic coronaviruses in animals cause a wide range of disease signs resulting from respiratory, enteric, and neurological tissue tropism. Although HCoVs cause primarily respiratory symptoms, the potential for a wide range of severe disease symptoms in humans caused by infection by future emergent coronaviruses cannot be excluded. Despite the severity and diversity of coronavirus disease signs and symptoms affecting a large number of important livestock species as well as humans, there are no proven therapies that specifically target CoVs.