Id |
Subject |
Object |
Predicate |
Lexical cue |
T30 |
0-12 |
Sentence |
denotes |
Coronavirus: |
T31 |
13-24 |
Sentence |
denotes |
An Overview |
T32 |
25-220 |
Sentence |
denotes |
Coronaviruses (CoVs) consist of a group of enveloped, non-segmented, positive-sense single-stranded RNA viruses from the order Nidovirales, family Coronaviridae, and subfamily Orthocoronavirinae. |
T33 |
221-391 |
Sentence |
denotes |
Coronaviruses have the largest genome of all RNA viruses, encoding viral proteins involved in transcribing viral RNA, replication, structure, and accessory proteins (15). |
T34 |
392-675 |
Sentence |
denotes |
The virus has four main proteins – spike, envelope, membrane, and nucleocapsid (S, E, M, and N, respectively) – important for the virus to enter and replicate in the host cell (16), also representing the main molecules used for diagnosis, antiviral treatment, and potential vaccines. |
T35 |
676-791 |
Sentence |
denotes |
According to antigenic and genetic criteria, CoVs are classified into three groups: α-CoVs, β-CoVs and γ-CoVs (17). |
T36 |
792-959 |
Sentence |
denotes |
Coronaviruses of human infection (hCoVs) are detected in both α-CoVs (hCoV-229E and NL63) and β-CoVs (MERS-CoV, hCoV-OC43, hCoV-HKU1, SARS-CoV-1, and SARS-CoV-2) (18). |
T37 |
960-1163 |
Sentence |
denotes |
In addition to infecting humans, α-CoVs and β-CoVs can infect several species of mammals, including bats and pigs, while γ-CoVs infects birds, wild cats, pigs, and some species of marine mammals (19–22). |
T38 |
1164-1314 |
Sentence |
denotes |
CoVs have a high potential of jumping between species and their genome is characterized by high-frequency recombination and a high mutation rate (23). |
T39 |
1315-1544 |
Sentence |
denotes |
hCoVs are responsible for the common cold and other respiratory pathologies with different degrees of severity, especially in babies, the elderly, and immunocompromised patients, characterized by human-to-human transmission (24). |
T40 |
1545-1777 |
Sentence |
denotes |
Coronavirus severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) (25–27) are caused by human β-CoVs and represent a serious illness with a case-fatality ratio of 9 - 10% and 35%, respectively (8, 28). |
T41 |
1778-2035 |
Sentence |
denotes |
In contrast, according to data provided by the WHO, COVID-19 caused by SARS-CoV-2 shows an estimated lethality of ~5% of reported cases (data reported until July 2020) (29), reaching rates of up to 15% among elderly patients and patients with comorbidities. |
T42 |
2036-2236 |
Sentence |
denotes |
Despite the lower case-fatality rate, the high viral transmissibility of SARS-CoV-2 generates an overall number of cases that far outweighs SARS or MERS for spreading more easily among people (5, 28). |
T43 |
2237-2412 |
Sentence |
denotes |
The first report of a COVID-19 case in Wuhan, China, occurred in December 2019, and in February the WHO declared the matter a public health emergency of international concern. |
T44 |
2413-2589 |
Sentence |
denotes |
Until now (September 2020), reports of COVID-19 account for almost 30 million cases and more than 900 thousand deaths in more than 220 countries, territories, or areas (1, 29). |
T45 |
2590-2760 |
Sentence |
denotes |
Imperial College, UK (30) proposed a mathematical model whose prospects indicate 7 billion infections and 40 million deaths in 2020 in the absence of mitigation measures. |
T46 |
2761-3161 |
Sentence |
denotes |
Both SARS-CoV and MERS-CoV were initially believed to have resulted from a zoonotic spread from a bat population (31). α-CoVs and β-CoVs are believed to have evolved over thousands of years, restricted to bats and intermediate mammalian hosts (civet cats for SARS-CoV-1 and dromedary camels for MERS-CoV), which probably contributed to the zoonotic transmission of the new coronavirus to humans (32). |
T47 |
3162-3347 |
Sentence |
denotes |
Regarding SARS-CoV-2 transmission, several works have demonstrated that coronaviruses found in pangolins (Manis javanica) and SARS-CoV-2 share a genomic similarity of approximately 91%. |
T48 |
3348-3559 |
Sentence |
denotes |
The presence of the virus in samples of pulmonary fibrosis in pangolins found around the COVID-19 outbreak suggests that these animals were the hosts responsible for spreading the virus among humans (4, 21, 33). |
T49 |
3560-3786 |
Sentence |
denotes |
In contrast, some researchers claim that SARS-CoV-2 did not come directly from pangolins since, despite their similarity, the viruses found in these animals do not have the essential tools needed to infect human cells (4, 34). |
T50 |
3787-3981 |
Sentence |
denotes |
Thus, the possibility of other animals, such as ferrets and snakes, acting as intermediate hosts for SARS-CoV-2 and being responsible for zoonotic transmission is still under consideration (35). |
T51 |
3982-4201 |
Sentence |
denotes |
Since SARS-CoV-2 genomes’ information is still scarce and genomes of other coronaviruses closely related to this virus have limited availability (36), the evolutionary origin of SARS-CoV-2 is yet to be fully understood. |
T52 |
4202-4393 |
Sentence |
denotes |
So far, it is known that, compared with other β-CoVs, SARS-CoV-2 shows 50, 79, and 88 - 96% of genome similarity with MERS-CoV, SARS-CoV-1, and the bat SARS-like virus, respectively (37, 38). |
T53 |
4394-4596 |
Sentence |
denotes |
The genomic changes of SARS-CoV-2 appear in both non-structural and structural proteins – notably in proteins S, M, and N – affecting viral multiplication, encapsulation, tropism, and transmission (39). |
T54 |
4597-5126 |
Sentence |
denotes |
Two important characteristics were described in the genome of SARS-CoV-2 that lead to alterations in the S protein: (i) receptor-binding domain (RBD), which is the most variable part of the viral genome, appears to be optimized for binding to the human ACE2 receptor, and (ii) presence of a polybasic (furin) cleavage site at the S1 and S2 boundary, via the insertion of twelve nucleotides, which allows effective cleavage by furin and other proteases and has a role in determining viral tropism, infectivity, and host range (4). |
T55 |
5127-5211 |
Sentence |
denotes |
Such genomic changes also affected the recognition of these viruses by immune cells. |
T56 |
5212-5440 |
Sentence |
denotes |
Baruah and Bose (40) demonstrated that Sars-CoV-2 has specific regions for B cell and cytotoxic T cell glycoproteins recognition, which does not coincide with those found in bat-derived CoV, SARS-CoV-1, or MERS-CoV ( Figure 1 ). |
T57 |
5441-5597 |
Sentence |
denotes |
Such distinguished interaction of cells and viruses can promote unusual immunomodulation or immune responses that contribute to the severity of the disease. |
T58 |
5598-5692 |
Sentence |
denotes |
All aspects of immunomodulation and immune evasion will be discussed in the subsequent topics. |
T59 |
5693-5756 |
Sentence |
denotes |
Figure 1 Genetic evolution of SARS-CoV-2 and its consequences. |
T60 |
5757-5964 |
Sentence |
denotes |
Compared with other β-CoVs, SARS-CoV-2 has similarities of 50, 79, and 88 - 96% to MERS-CoV, SARS-CoV-1, and bat SARS-like-CoV genome, respectively, with 91% similarity with SARS-like CoV found in pangolins. |
T61 |
5965-6226 |
Sentence |
denotes |
The virus resulted from mutations that caused changes in important proteins for its virulence; notably, the spike, matrix, envelope, and nucleocapsid proteins caused alterations in host cell interactions, which culminated in a new aggressive disease (COVID-19). |
T62 |
6227-6288 |
Sentence |
denotes |
RBD (receptor binding domain), S1 (subunit 1) S2 (subunit 2). |