Microbial GWAS studies revealing combinations of Omicron RBD mutations existed and may contribute to antibody evasion and ACE2 binding

Since Omicron variant of SARS-CoV-2 was first detected in South Africa (SA), it has now dominated in United Kingdom (UK) of Europe and United State (USA) of North America. A prominent feature of this variant is the gathering of spike protein mutations, in particularly at the receptor binding domain (RBD). These RBD mutations essentially contribute to antibody resistance of current immune approaches. During global spillover, combinations of RBD mutations may exist and synergistically contribute to antibody resistance in fact. Using three geographic-stratified genome wide association studies (GWAS), we observed that RBD combinations exhibited a geographic pattern and genetical associated, such as five common mutations in both UK and USA Omicron, six or two specific mutations in UK or USA Omicron. Although the UK specific RBD mutations can be further classified into two separated sub-groups of combination based on linkage disequilibrium analysis. Functional analysis indicated that the common RBD combinations (fold change, -11.59) alongside UK or USA specific mutations significantly reduced neutralization (fold change, -38.72, -18.11). As RBD overlaps with angiotensin converting enzyme 2(ACE2) binding motif, protein-protein contact analysis indicated that the common RBD mutations enhanced ACE2 binding accessibility and were further strengthened by UK or USA-specific RBD mutations. Spatiotemporal evolution analysis indicated that UK-specific RBD mutations largely contribute to global spillover. Collectively, we have provided genetic evidence of RBD combinations and estimated their effects on antibody evasion and ACE2 binding accessibility.

Tracing two causative SNPs reveals SARS-CoV-2 transmission in North America population

During the COVID-19 pandemic, precisely tracing the route of the SARS-CoV-2 transmission in human population remains challenging. Because this RNA virus can mutate massively without a specifically tracing maker. Herein, using a geographic stratified genome-wide association study (GWAS) of 2599 full-genome sequences, we identified that two SNPs (i.e., 1059.C>T and 25563.G>T) of linkage disequilibrium were presented in approximately half of North America SARS-CoV-2 population (p = 2.44 x 10-212 and p = 2.98 x 10-261), resulting two missense mutations (i.e., Thr 265 Ile and Gln 57 His) in ORF1ab and ORF3a, respectively. Interestingly, these two SNPs exclusively occurred in the North America dominated clade 1, accumulated during mid to late March, 2020. We did not find any of these two SNPs by retrospectively tracing the two SNPs in bat and pangolin related SARS-CoV-2 and human SARS-CoV-2 from the first epicenter Wuhan or other regions of China mainland. This suggested that the SARS-CoV-2 population of Chinese mainland were different from the prevalent strains of North America. Time-dependently, we found that these two SNPs first occurred in Europe SARS-CoV-2 (26-Feb-2020) which was 3 days early than the occurring date of North America isolates and 17 days early for Asia isolates (Taiwan China dominated). Collectively, this population genetic analysis highlights a well-confidential transmission route of the North America isolates and the two SNPs we newly identified are possibly novel diagnosable or druggable targets for surveillance and treatment.

Construction and application of Escherichia Coli-Riemerella anatipestifer efficient shuttle plasmid pFY02 / 生物工程学报

Riemerella anatipestifer is a pathogen that mainly infects ducks, gooses, turkeys and other birds, causing septicemia and serositis. At present, the function of R. anatipestifer genes are studied by gene deletion and complementation. However, the shuttle plasmid pLMF03 used at present is inefficient for conjugation. Moreover, less restriction enzyme site can be used for cloning. It is not able to use for all the genes complementation. To solve this disadvantage, the conjugative transfer site, R. anatipestifer replication initiation gene, high expression promoter and a number of enzyme cutting sites were cloned into the plasmid pPM5, to generate the new shuttle plasmid pFY02. The shuttle plasmid pFY02 was stable in R. anatipestifer and had a high conjugative transfer efficiency. The R. anatipestifer tonB2 mutant strain could be complemented by shuttle plasmid pFY02 expressing tonB2, indicating that the shuttle plasmid can be used to the complementation of R. anatipestifer. Taken together, the new shuttle plasmid pFY02 constructed in this study replenishes the genetic tool for complementation.

Molecular characterization of duck enteritis virus CHv strain UL49.5 protein and its colocalization with glycoprotein M

The UL49.5 gene of most herpesviruses is conserved and encodes glycoprotein N. However, the UL49.5 protein of duck enteritis virus (DEV) (pUL49.5) has not been reported. In the current study, the DEV pUL49.5 gene was first subjected to molecular characterization. To verify the predicted intracellular localization of gene expression, the recombinant plasmid pEGFP-C1/pUL49.5 was constructed and used to transfect duck embryo fibroblasts. Next, the recombinant plasmid pDsRed1-N1/glycoprotein M (gM) was produced and used for co-transfection with the pEGFP-C1/pUL49.5 plasmid to determine whether DEV pUL49.5 and gM (a conserved protein in herpesviruses) colocalize. DEV pUL49.5 was thought to be an envelope glycoprotein with a signal peptide and two transmembrane domains. This protein was also predicted to localize in the cytoplasm and endoplasmic reticulum with a probability of 66.7%. Images taken by a fluorescence microscope at different time points revealed that the DEV pUL49.5 and gM proteins were both expressed in the cytoplasm. Overlap of the two different fluorescence signals appeared 12 h after transfection and continued to persist until the end of the experiment. These data indicate a possible interaction between DEV pUL49.5 and gM.