Severe acute respiratory syndrome coronavirus 2 (SARS-CoV) and 2019 novel coronavirus (2019-nCoV) pose a serious threat to human health. To determine the genetic relationships between the two clades and the genetic mechanism of origin of 2019-nCoV, we compared the whole genomic sequences of SARS-CoV and 2019-nCoV and dissected their phylogenetic histories. Surprisingly, we found that the two clades have frequently exchanged genetic material through homologous recombination in recent decades. Nearly 2/3 of the genetic material of CoVZC45 comes from 2019-nCoV lineage, while the other 1/3 descends from SARS-CoV clade. In particular, the 2019-nCoV lineage might have acquired its receptor-binding domain from the SARS-CoV clade, enabling 2019-nCoV to bind to human angiotensin-converting enzyme 2 receptor and helping it to spread rapidly in humans. Our findings suggest the role of a virus of the SARS-CoV clade in causing COVID-19 and warn of the possible emergence of more mosaic CoVs capable of causing severe epidemics.
Ebolavirus (EBOV) is responsible for several EBOV disease (EVD) outbreaks in Africa, with a fatality rate of up to 90%. During 2014-2016, An epidemic of EVD spread throughout Sierra Leone, Guinea and Liberia, and killed over 11,000 people. EBOV began to circulate again in the Democratic Republic of Congo in 2018. Due to the need for a BSL-4 facility to manipulate this virus, the development and improvement of specific therapeutics has been hindered. As a result, it is imperative to perform reliable research on EBOV under lowered BSL restrictions. In this study, we developed a safe neutralization assay based on pseudotyped EBOV, which incorporates the glycoprotein of the 2014 EBOV epidemic strain into a lentivirus vector. Our results demonstrated that the tropism of pseudotyped EBOV was similar to that of authentic EBOV, but with only one infection cycle. And neutralizing activity of both authentic EBOV and pseudotyped EBOV were compared in neutralization assay using three different samples of antibody-based reagents against EBOV, similar results were obtained. In addition, an indirect ELISA was performed to show the relationship between IgG and neutralizing antibody against EBOV detected by our pseudotyped EBOV-based neutralization assay. As expected, the neutralizing antibody titers varied with the IgG titers detected by indirect ELISA, and a correlation between the results of the two assays was identified. By comparison with two different assays, the reliability of the results detected by the pseudotyped EBOV-based neutralization assay was confirmed. Collectively, in the absence of BSL-4 restrictions, pseudotyped EBOV production and neutralizing activity evaluation can be performed safely and in a manner that is neither labor- nor time-consuming, providing a simple and safe method for EBOV-neutralizing antibody detection and the assessment of immunogenicity of EBOV vaccines. All these remarkable advantages of the newly established assay highlight its potential to further application in assessment of immunogenicity of EBOV vaccine candidates.
2019-nCoV and SARS-CoV seriously threatened human health. In order to know the genetic relations of the two dangerous clades and genetic mechanism of origin of 2019-nCoV, we compared whole genomic sequences of SARS-CoV and 2019-nCoV clades, and dissected phylogenetic histories of them. To our surprise, we found that the two clades may frequently exchange their genetic materials through homologous recombination in recent decades, resulting in 2019-nCoV and its sister branch represented by CoVZC45. Particularly the 2019-nCoV lineage might thereby acquire the receptor-binding domain from the SARS-CoV clade, enabling it to make use of angiotensin-converting enzyme 2 as well and thus spread rapidly in humans. Our findings suggest the accomplice role of a virus of SARS-CoV clade in COVID-19 and warn of the possible emergence of more mosaic CoVs capable of launching severe epidemic.
Since its first emergence in 2012, cases of infection with Middle East respiratory syndrome coronavirus (MERS-CoV) have continued to occur. In this study, we present two nucleic acid visualization assays that target the MERS-CoV UpE and N genes as a panel that combines reverse transcription recombinase polymerase amplification with a closed vertical flow visualization strip (RT-RPA-VF). The limit of detection was 1.2×10^1 copies/μl for the UpE assay and 1.2 copies/μl for the N assay. The two assays exhibited no cross-reactivity with multiple CoVs, including the bat severe acute respiratory syndrome related coronavirus (SARSr-CoV), the bat coronavirus HKU4, and the human coronaviruses 229E, OC43, HKU1 and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The RT-RPA-VF assay does not require sophisticated equipment and provides rapid detection within 30 min, so it has potential for use in surveillance and detection of MERS-CoV in low-resource settings.
A novel bat coronavirus (2019-nCoV) caused an outbreak of infectious pneumonia termed COVID-19 in the world. This reminds us of another notorious bat coronavirus, SARS-CoV, which mysteriously broke out in China 17 years ago and killed nearly 800 people worldwide. A key to its efficient human attack is adopting angiotensin-converting enzyme 2 (ACE2) as the receptor. The relationship between 2019-nCoV and SARS-CoV has aroused much public concern. To our surprise, we found that the two CoV lineages may frequently exchange their genetic materials through homologous recombination. Particularly 2019-nCoV might thereby acquire the receptor-binding domain from the SARS-CoV clade, enabling it to make use of ACE2 as well and thus spread rapidly in humans. Our findings suggest the accomplice role of a virus of SARS-CoV clade in COVID-19 and warn of the possible emergence of more mosaic CoVs capable of launching severe epidemic.