The pandemic COVID-19 caused by the zoonotic virus SARS-CoV-2 has devastated countries worldwide, infecting more than 4.5 million people and leading to more than 300,000 deaths. Whole genome sequencing (WGS) is an effective tool to monitor emerging strains and provide information for intervention, thus help to inform outbreak control decisions. Here, we reported the first effort to sequence and de novo assemble the whole genome of SARS-CoV-2 using PacBio's SMRT sequencing technology in Vietnam. We also presented the annotation results and a brief analysis of the variants found in our SARS-CoV-2 strain, which was isolated from a Vietnamese patient. The sequencing was successfully completed and de novo assembled in less than 30 hours, resulting in one contig with no gap and a length of 29,766 bp. All detected variants as compared to the NCBI reference were highly accurate as confirmed by Sanger sequencing. The results have shown the potential of long read sequencing to provide high quality WGS data to support public health responses, and advance understanding of this and future pandemics.
The creation of recombinant oligomeric haemagglutinin proteins from A/H5N1 virus is a new concern for many scientists. In this study, the gene encoding the haemagglutinin protein (H5TG) derived from virus A/duck/Vietnam/TG24-01/2005 was fused with three different motifs (GCN4pII, GCN4pII-IgMFc and GCN4pII-ELP-IgMFc) in order to form three recombinant proteins (trimeric H5TGpII, oligomeric H5TGpII-IgMFc and ELPylated oligomeric H5TGpII-ELP-IgMFc, respectively) for enhancing protein expression, bio-function and purification of H5TG. These H5TG fragments have been attached to expression cassettes in the pCB301 shuttle vector, transiently expressed in Nicotiana benthamiana by agroinfiltration, then the protein expression was confirmed by SDS-PAGE and Western blot analysis. The results showed that the expression level of the H5TGpII-ELP-IgMFc protein in plant raw extract was stronger than that of two other proteins analyzed in this paper. Evaluation of bio-function showed that the haemagglutination titre (HA titre) of the total solution protein extract containing H5TGpII-IgMFc protein was highest (64 HAU) compared to that containing two remaining proteins (8 HAU). Subsequently, the H5TGpII and H5TGpII-IgMFc proteins were purified by immobilized metal ion affinity chromatography (IMAC), while the H5TGpII-ELP-IgMFc protein was purified using membrane-based Inverse Transition Cycling (mITC). The oligomer state of the purified proteins was then determined by non-reducing SDS-PAGE. The haemagglutination assay analysis of purified proteins showed that the lowest protein amount causing erythrocyte agglutination (1 HAU) of the H5TGpII-IgMFc protein was 0.06 µg and lower four times than that of H5TGpII and H5TGpII-ELP-IgMFc proteins (both of them were 0.24 µg). This indicates that the fusing of the GCN4pII-IgMFc motif into the H5TG protein gives the stronger bio-function than the fusing of two remaining motifs into this protein. This result opens up the applicability of the IgMFc for generation of oligomer proteins to enhance the bio-function of target proteins in the study of recombinant vaccine production.
Citrus Greening, also known as HuangLongbing (HLB), is considered one of the most dangerous citrus diseases, and limiting the production of citrus trees all over the world. Production of antibodies against Ompa protein of Candidatus Liberibacter asiaticus (CLas) for detection of citrus greening disease is considered as promising research direction. In this study, for the purpose of producting antibodies against Ompa of CLas, we firstly used the camel VHH antibody library for screening VHH antibodies against Ompa using phage-display technique. Next, phages which had strong interaction with Ompa as shown in ELISA were selected for phagemid isolation and the DNA fragments encoding VHH antibodies were sequenced. The DNA fragment encoding the best VHH antibody was then selected and inserted into the expression vector pET-21a (+), then cloned in Ecoli DH5α strain and expressed in BL21 (DE3) strain. The expression of VHH antibodies against Ompa was optimized at different temperatures with an inductive concentration of 0.1 M IPTG. Anti-Ompa VHH antibodies were purified under denatured conditions then re-folded. The biological activity of the VHH antibody with Ompa antigen was assessed by indirect-ELISA reaction. Results indicated that the VHH antibody had a very strong interaction with the Ompa antigen. This opens up the prospect of applying VHH antibody in the detection of citrus greening disease.
Porcine Epidemic Diarrhea (PED) is an infectious disease with high mortality especially in suckling piglets. Among the structural proteins of Porcine Epidemic Diarrhea Virus (PEDV), the S protein (including sub-domain S1 and S2), is a homotrimer protein that plays an important role in attaching the viruses to the cell receptors. In particular, the S1 protein is considered as an important sub-component in the development of effective vaccines against PEDV. In this study, for the purpose of expressing S1 in the original form of trimmer and oligomer of trimer based on S-tag and S-protein interactions, the DNA encoding for S1 protein was fused with GCN4pII or GCN4pII-Stag, was then inserted to the pRTRA cloning vector under the control of the 35S CaMV promoter. After that, the whole cassete was inserted into the pCB301 vector and transformed into Agrobacterium tumefaciens for transient expression on Nicotiana benthamiana. The expression of recombinant S1 proteins in tobacco was determined by Western blot. The results showed that the expression levels of S1 trimer and S1 trimer S-tag proteins were equal in plants, which also indicated that S-tag fusion did not affect the expression level of the S1 protein. However, the expression level of S1 proteins was relatively low, reaching 0.005% of total soluble protein. In addition, the expression of S1 trimer S-tag protein and Sprotein-tp protein by co-transformation of two A. tumefaciens strains containing corresponding vectors in plants were also determined by Western blot. This is a premise study for the development of subunit vaccines in plants that prevent the spread of PEDV.
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