Biology subjects

Chu, D. K. W.

Publications and source records attributed to Chu, D. K. W..

4 recordsLinked to original sources

bioRxiv2023

Mutation nsp6 L232F associated with MERS-CoV zoonotic transmission confers higher viral replication in human respiratory tract cultures ex-vivo

Middle East respiratory syndrome coronavirus (MERS-CoV) causes zoonotic disease. Dromedary camels are the source of zoonotic infection. We identified a mutation of amino acid leucine to phenylalanine in the codon 232 position of the non-structural protein 6 (nsp6) (nsp6 L232F) that is repeatedly associated with zoonotic transmission. We generated a pair of isogenic recombinant MERS-CoV with nsp6 232L and 232F residues, respectively, and showed that the nsp6 L232F mutation confers higher replication competence in ex-vivo culture of human nasal and bronchial tissues and in lungs of mice experimentally infected in-vivo. Mechanistically, the nsp6 L232F mutation appeared to modulate autophagy and was associated with higher exocytic virus egress, while innate immune responses and zippering activity of the endoplasmic reticulum remained unaffected. Our study suggests that MERS-CoV nsp6 may contribute to viral adaptation to humans. This highlights the importance of continued surveillance of MERS-CoV in both camels and humans. ImportanceViral host adaptation plays an important role in zoonotic transmission of coronaviruses. For MERS-CoV that widely circulates in dromedary camels from Arabian Peninsula, camel-to human transmissions are ongoing, raising the possibility of human adaptive evolution for MERS-CoV. Here, we analysed MERS-CoV sequences and identified an amino acid mutation L232F in nsp6 to occur repeatedly in human MERS-CoV over the years since the first outbreak in 2012. We found the nsp6 L232F confers increase viral replication in-vitro, in ex-vivo upper human respiratory tract cultures and in mice, using a reverse genetics approach. Our results showed the nsp6 L232F may be advantageous for MERS-CoV to replicate in humans. This study highlighted a human adaptation of MERS-CoV and a need for continued surveillance of MERS-CoV to identify any further adaptations in humans, which may be relevant to the pandemic potential of MERS-CoV.

microbiology↗

bioRxiv2020

Cross Sectional Study Of Middle East Respiratory Syndrome (MERS-CoV Infection) In Camels At Selected Sites Of Amibara District, Afar Region, Ethiopia

BackgroundA Cross sectional study of Middle East Respiratory Syndrome Corona virus (MERS-CoV) in Camel was conducted between February 2018 to April 2019 in three selected sites of Amibara district of Afar region, Northeast Ethiopia. The study was aimed to observe the current sero-prevalence status of MERS-CoV, assess the presence of active cases through detection RNA Viral particle and investigate possible risk factors of MERS-CoV in camels. A total of 589 sera were collected and tested with indirect Enzyme linked ImmunoSorbent Assay (iELISA). ResultThe overall seroprevalance of MERS-CoV was 87.3% (n=514/589, 95% CI: 84.5-89.9). Association of different risk factors with seroprevalance revealed that origin (X2=13.39,P=0.001), sex (X2=4.5 P=0.034), age ((X2=185.7, P=0.001) season (X2=41.7, P=0.000) and reproduction status (X2=96.1, P=0.001) displayed a statistical significant difference among the groups (P<0.05) while herd size did not show a Significant difference among groups (p>0.05). In multivariable logistic regression analysis, age (OR=7.39, 95% CI:3.43-15.91), season (OR=4.83, 95% CI:-2.14-10.90), and in adult female camel reproduction status (OR=7.39,95% C I:3.43-15.91) showed statistically significant difference among the groups for MERS CoV antibody detection while risk factors of origin, animal sex and herd size difference were statistically insignificant. A total of 857 nasal swab samples were collected for the detection of MERS-CoV RNA particle. However, all swab samples tested by Real-time reverse transcription polymerase chain reaction (RT-PCR) technique were Negative for the virus. ConclusionIn conclusion, the present study revealed a high seroprevalance of MERS CoV in adult camels. However, in spite of high seroprevalance the lack of any RNA viral particle in the study suggests the need for further in depth longitudinal study to detect the circulating virus focusing on juveniles and young camels whereby seroprevalance of antibody is low when compared with adult camel in order to get the active virus before the camel develop antibody. Moreover, the zoonotic significance and potential transmission routes of MERS CoV to pastoral communities should also be investigated and design strategy for the preparedness in control of the diseases in Ethiopia.

microbiology↗

bioRxiv2020

A Rare Deletion in SARS-CoV-2 ORF6 Dramatically Alters the Predicted Three-Dimensional Structure of the Resultant Protein

The function of the SARS-CoV-2 accessory protein p6, encoded by ORF6, is not fully known. Based upon its similarity to p6 from SARS-CoV, it may play a similar role, namely as an antagonist of type I interferon (IFN) signaling. Here we report the sequencing of a SARS-CoV-2 strain passaged six times after original isolation from a clinical patient in Hong Kong. The genome sequence shows a 27 nt in-frame deletion ({Delta}27,264-27,290) within ORF6, predicted to result in a 9 aa deletion ({Delta}FKVSIWNLD) from the central portion of p6. This deletion is predicted to result in a dramatic alteration in the three-dimensional structure of the resultant protein (p6{Delta}22-30), possibly with significant functional implications. Analysis of the original clinical sample indicates that the deletion was not present, while sequencing of subsequent passages of the strain identifies the deletion as a majority variant. This suggests that the deletion originated ab initio during passaging and subsequently propagated into the majority, possibly due to the removal of selective pressure through the IFN-deficient Vero E6 cell line. The specific function of the SARS-CoV-2 p6 N-terminus, if any, has not yet been determined. However, this deletion is predicted to cause a shift from N-endo to N-ecto in the transmembrane localization of the SARS-CoV-2 p6{Delta}22-30 N-terminus, possibly leading to the ablation of its native function.

genomics↗

bioRxiv2020

Multivariate Analyses of Codon Usage in 2019 Novel Coronavirus on the Genomic Landscape of Betacoronavirus

Coronavirus disease 2019 (COVID-19) is a global health concern as it continues to spread within China and beyond. The causative agent of this disease, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), belongs to the genus Betacoronavirus which also includes severe acute respiratory syndrome related coronavirus (SARSr-CoV) and Middle East respiratory syndrome related coronavirus (MERSr-CoV). Codon usage of viral genes are believed to be subjected to different selection pressures in different host environments. Previous studies on codon usage of influenza A viruses can help identify viral host origins and evolution trends, however, similar studies on coronaviruses are lacking. In this study, global correspondence analysis (CA), within-group correspondence analysis (WCA) and between-group correspondence analysis (BCA) were performed among different genes in coronavirus viral sequences. The amino acid usage pattern of SARS-CoV-2 was generally found similar to bat and human SARSr-CoVs. However, we found greater synonymous codon usage differences between SARS-CoV-2 and its phylogenetic relatives on spike and membrane genes, suggesting these two genes of SARS-CoV-2 are subjected to different evolutionary pressures.

evolutionary biology↗