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Nature Reviews. Microbiology May 2022Clostridioides difficile is a Gram-positive anaerobe that can cause a spectrum of disorders that range in severity from mild diarrhoea to fulminant colitis and/or death.... (Review)
Review
Clostridioides difficile is a Gram-positive anaerobe that can cause a spectrum of disorders that range in severity from mild diarrhoea to fulminant colitis and/or death. The bacterium produces up to three toxins, which are considered the major virulence factors in C. difficile infection. These toxins promote inflammation, tissue damage and diarrhoea. In this Review, we highlight recent biochemical and structural advances in our understanding of the mechanisms that govern host-toxin interactions. Understanding how C. difficile toxins affect the host forms a foundation for developing novel strategies for treatment and prevention of C. difficile infection.
Topics: Antitoxins; Bacterial Proteins; Bacterial Toxins; Clostridioides difficile; Diarrhea; Humans
PubMed: 34837014
DOI: 10.1038/s41579-021-00660-2 -
Nature Feb 2022The SARS-CoV-2 B.1.1.529 (Omicron) variant contains 15 mutations of the receptor-binding domain (RBD). How Omicron evades RBD-targeted neutralizing antibodies requires...
The SARS-CoV-2 B.1.1.529 (Omicron) variant contains 15 mutations of the receptor-binding domain (RBD). How Omicron evades RBD-targeted neutralizing antibodies requires immediate investigation. Here we use high-throughput yeast display screening to determine the profiles of RBD escaping mutations for 247 human anti-RBD neutralizing antibodies and show that the neutralizing antibodies can be classified by unsupervised clustering into six epitope groups (A-F)-a grouping that is highly concordant with knowledge-based structural classifications. Various single mutations of Omicron can impair neutralizing antibodies of different epitope groups. Specifically, neutralizing antibodies in groups A-D, the epitopes of which overlap with the ACE2-binding motif, are largely escaped by K417N, G446S, E484A and Q493R. Antibodies in group E (for example, S309) and group F (for example, CR3022), which often exhibit broad sarbecovirus neutralizing activity, are less affected by Omicron, but a subset of neutralizing antibodies are still escaped by G339D, N440K and S371L. Furthermore, Omicron pseudovirus neutralization showed that neutralizing antibodies that sustained single mutations could also be escaped, owing to multiple synergetic mutations on their epitopes. In total, over 85% of the tested neutralizing antibodies were escaped by Omicron. With regard to neutralizing-antibody-based drugs, the neutralization potency of LY-CoV016, LY-CoV555, REGN10933, REGN10987, AZD1061, AZD8895 and BRII-196 was greatly undermined by Omicron, whereas VIR-7831 and DXP-604 still functioned at a reduced efficacy. Together, our data suggest that infection with Omicron would result in considerable humoral immune evasion, and that neutralizing antibodies targeting the sarbecovirus conserved region will remain most effective. Our results inform the development of antibody-based drugs and vaccines against Omicron and future variants.
Topics: Angiotensin-Converting Enzyme 2; Antibodies, Monoclonal; Antibodies, Neutralizing; Antibodies, Viral; COVID-19; COVID-19 Vaccines; Cells, Cultured; Convalescence; Epitopes, B-Lymphocyte; Humans; Immune Evasion; Immune Sera; Models, Molecular; Mutation; Neutralization Tests; SARS-CoV-2; Spike Glycoprotein, Coronavirus
PubMed: 35016194
DOI: 10.1038/s41586-021-04385-3 -
American Journal of Transplantation :... Mar 2022The IgG-degrading enzyme derived from Streptococcus pyogenes (Imlifidase, Hansa Biopharma) is a novel agent that cleaves all four human subclasses of IgG and has... (Review)
Review
The IgG-degrading enzyme derived from Streptococcus pyogenes (Imlifidase, Hansa Biopharma) is a novel agent that cleaves all four human subclasses of IgG and has therapeutic potential for HLA desensitization in kidney transplantation and antibody-mediated rejection. Data from clinical trials in kidney transplantation demonstrated rapid degradation of anti-HLA donor-specific antibodies facilitating HLA-incompatible transplantation, which led to conditional approval of imlifidase by the European Medicines Agency for desensitization in kidney transplant recipients of a deceased donor with a positive cross match. Important considerations arising from the early experiences with imilfidase on kinetics of donor-specific antibodies after administration, timing of complementary therapeutic monoclonal or polyclonal IgG antibodies, and interference with cross match assays should be recognized as imlifidase emerges as a therapeutic agent for clinical transplantation.
Topics: Antilymphocyte Serum; Graft Rejection; HLA Antigens; Humans; Immunoglobulin G; Immunosuppressive Agents; Kidney Transplantation; Tissue Donors
PubMed: 34467625
DOI: 10.1111/ajt.16828 -
Emerging Microbes & Infections Dec 2020Pseudoviruses are useful virological tools because of their safety and versatility, especially for emerging and re-emerging viruses. Due to its high pathogenicity and...
Pseudoviruses are useful virological tools because of their safety and versatility, especially for emerging and re-emerging viruses. Due to its high pathogenicity and infectivity and the lack of effective vaccines and therapeutics, live SARS-CoV-2 has to be handled under biosafety level 3 conditions, which has hindered the development of vaccines and therapeutics. Based on a VSV pseudovirus production system, a pseudovirus-based neutralization assay has been developed for evaluating neutralizing antibodies against SARS-CoV-2 in biosafety level 2 facilities. The key parameters for this assay were optimized, including cell types, cell numbers, virus inoculum. When tested against the SARS-CoV-2 pseudovirus, SARS-CoV-2 convalescent patient sera showed high neutralizing potency, which underscore its potential as therapeutics. The limit of detection for this assay was determined as 22.1 and 43.2 for human and mouse serum samples respectively using a panel of 120 negative samples. The cutoff values were set as 30 and 50 for human and mouse serum samples, respectively. This assay showed relatively low coefficient of variations with 15.9% and 16.2% for the intra- and inter-assay analyses respectively. Taken together, we established a robust pseudovirus-based neutralization assay for SARS-CoV-2 and are glad to share pseudoviruses and related protocols with the developers of vaccines or therapeutics to fight against this lethal virus.
Topics: Animals; Antibodies, Neutralizing; Antibodies, Viral; Betacoronavirus; COVID-19; Cell Line; Coronavirus Infections; Humans; Immune Sera; Immunization, Passive; Limit of Detection; Membrane Glycoproteins; Mice; Neutralization Tests; Plasmids; Pneumonia, Viral; Reproducibility of Results; SARS-CoV-2; Sensitivity and Specificity; Spike Glycoprotein, Coronavirus; Vesicular stomatitis Indiana virus; Viral Envelope Proteins; Virus Internalization; COVID-19 Serotherapy
PubMed: 32207377
DOI: 10.1080/22221751.2020.1743767 -
Nature Mar 2022The SARS-CoV-2 Omicron BA.1 variant emerged in 2021 and has multiple mutations in its spike protein. Here we show that the spike protein of Omicron has a higher affinity...
The SARS-CoV-2 Omicron BA.1 variant emerged in 2021 and has multiple mutations in its spike protein. Here we show that the spike protein of Omicron has a higher affinity for ACE2 compared with Delta, and a marked change in its antigenicity increases Omicron's evasion of therapeutic monoclonal and vaccine-elicited polyclonal neutralizing antibodies after two doses. mRNA vaccination as a third vaccine dose rescues and broadens neutralization. Importantly, the antiviral drugs remdesivir and molnupiravir retain efficacy against Omicron BA.1. Replication was similar for Omicron and Delta virus isolates in human nasal epithelial cultures. However, in lung cells and gut cells, Omicron demonstrated lower replication. Omicron spike protein was less efficiently cleaved compared with Delta. The differences in replication were mapped to the entry efficiency of the virus on the basis of spike-pseudotyped virus assays. The defect in entry of Omicron pseudotyped virus to specific cell types effectively correlated with higher cellular RNA expression of TMPRSS2, and deletion of TMPRSS2 affected Delta entry to a greater extent than Omicron. Furthermore, drug inhibitors targeting specific entry pathways demonstrated that the Omicron spike inefficiently uses the cellular protease TMPRSS2, which promotes cell entry through plasma membrane fusion, with greater dependency on cell entry through the endocytic pathway. Consistent with suboptimal S1/S2 cleavage and inability to use TMPRSS2, syncytium formation by the Omicron spike was substantially impaired compared with the Delta spike. The less efficient spike cleavage of Omicron at S1/S2 is associated with a shift in cellular tropism away from TMPRSS2-expressing cells, with implications for altered pathogenesis.
Topics: Adult; Aged; Aged, 80 and over; Angiotensin-Converting Enzyme 2; Animals; Antibodies, Neutralizing; Antibodies, Viral; COVID-19; COVID-19 Vaccines; Cell Line; Cell Membrane; Chlorocebus aethiops; Convalescence; Female; Humans; Immune Sera; Intestines; Lung; Male; Membrane Fusion; Middle Aged; Mutation; Nasal Mucosa; SARS-CoV-2; Serine Endopeptidases; Spike Glycoprotein, Coronavirus; Tissue Culture Techniques; Virulence; Virus Internalization; Virus Replication
PubMed: 35104837
DOI: 10.1038/s41586-022-04474-x -
Ugeskrift For Laeger Aug 2020Snakebite envenoming is a neglected tropical disease killing more than 100,000 people every year. Reducing the mortality and morbidity of snakebite envenoming depends on... (Review)
Review
Snakebite envenoming is a neglected tropical disease killing more than 100,000 people every year. Reducing the mortality and morbidity of snakebite envenoming depends on the accessibility of healthcare and antivenom, but also on sufficient knowledge on correct first aid treatment. In this review, we summarise the indications for antivenom treatment and which first-aid measures have proven effective, and which methods should be avoided, since many traditional methods of first-aid treatment of snakebites have been proven to be ineffective or even harmful.
Topics: Antivenins; Humans; Snake Bites
PubMed: 32800051
DOI: No ID Found -
The Journal of General Virology Sep 2020The sudden emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at the end of 2019 from the Chinese province of Hubei and its subsequent pandemic... (Comparative Study)
Comparative Study
The sudden emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at the end of 2019 from the Chinese province of Hubei and its subsequent pandemic spread highlight the importance of understanding the full molecular details of coronavirus infection and pathogenesis. Here, we compared a variety of replication features of SARS-CoV-2 and SARS-CoV and analysed the cytopathology caused by the two closely related viruses in the commonly used Vero E6 cell line. Compared to SARS-CoV, SARS-CoV-2 generated higher levels of intracellular viral RNA, but strikingly about 50-fold less infectious viral progeny was recovered from the culture medium. Immunofluorescence microscopy of SARS-CoV-2-infected cells established extensive cross-reactivity of antisera previously raised against a variety of non-structural proteins, membrane and nucleocapsid protein of SARS-CoV. Electron microscopy revealed that the ultrastructural changes induced by the two SARS viruses are very similar and occur within comparable time frames after infection. Furthermore, we determined that the sensitivity of the two viruses to three established inhibitors of coronavirus replication (remdesivir, alisporivir and chloroquine) is very similar, but that SARS-CoV-2 infection was substantially more sensitive to pre-treatment of cells with pegylated interferon alpha. An important difference between the two viruses is the fact that - upon passaging in Vero E6 cells - SARS-CoV-2 apparently is under strong selection pressure to acquire adaptive mutations in its spike protein gene. These mutations change or delete a putative furin-like cleavage site in the region connecting the S1 and S2 domains and result in a very prominent phenotypic change in plaque assays.
Topics: Adaptation, Biological; Animals; Antibodies, Viral; Betacoronavirus; Cell Line; Chlorocebus aethiops; Computational Biology; Conserved Sequence; Cross Reactions; Cytopathogenic Effect, Viral; High-Throughput Nucleotide Sequencing; Humans; Immune Sera; Kinetics; Mice; Microscopy, Electron; Microscopy, Fluorescence; RNA, Viral; Rabbits; Severe acute respiratory syndrome-related coronavirus; SARS-CoV-2; Vero Cells; Virus Replication
PubMed: 32568027
DOI: 10.1099/jgv.0.001453 -
Journal of Virology Jan 2022A comprehensive analysis and characterization of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection model that mimics non-severe and severe...
A comprehensive analysis and characterization of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection model that mimics non-severe and severe coronavirus disease 2019 (COVID-19) in humans is warranted for understating the virus and developing preventive and therapeutic agents. Here, we characterized the K18-hACE2 mouse model expressing human (h)ACE2 in mice, controlled by the human keratin 18 (K18) promoter, in the epithelia, including airway epithelial cells where SARS-CoV-2 infections typically start. We found that intranasal inoculation with higher viral doses (2 × 10 and 2 × 10 PFU) of SARS-CoV-2 caused lethality of all mice and severe damage of various organs, including lung, liver, and kidney, while lower doses (2 × 10 and 2 × 10 PFU) led to less severe tissue damage and some mice recovered from the infection. In this hACE2 mouse model, SARS-CoV-2 infection damaged multiple tissues, with a dose-dependent effect in most tissues. Similar damage was observed in postmortem samples from COVID-19 patients. Finally, the mice that recovered from infection with a low dose of virus survived rechallenge with a high dose of virus. Compared to other existing models, the K18-hACE2 model seems to be the most sensitive COVID-19 model reported to date. Our work expands the information available about this model to include analysis of multiple infectious doses and various tissues with comparison to human postmortem samples from COVID-19 patients. In conclusion, the K18-hACE2 mouse model recapitulates both severe and non-severe COVID-19 in humans being dose-dependent and can provide insight into disease progression and the efficacy of therapeutics for preventing or treating COVID-19. The pandemic of coronavirus disease 2019 (COVID-19) has reached nearly 240 million cases, caused nearly 5 million deaths worldwide as of October 2021, and has raised an urgent need for the development of novel drugs and therapeutics to prevent the spread and pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To achieve this goal, an animal model that recapitulates the features of human COVID-19 disease progress and pathogenesis is greatly needed. In this study, we have comprehensively characterized a mouse model of SARS-CoV-2 infection using K18-hACE2 transgenic mice. We infected the mice with low and high doses of SARS-CoV-2 to study the pathogenesis and survival in response to different infection patterns. Moreover, we compared the pathogenesis of the K18-hACE2 transgenic mice with that of the COVID-19 patients to show that this model could be a useful tool for the development of antiviral drugs and therapeutics.
Topics: Angiotensin-Converting Enzyme 2; Animals; COVID-19; Disease Models, Animal; Humans; Immune Sera; Keratin-18; Mice; Mice, Transgenic; Promoter Regions, Genetic; Reinfection; SARS-CoV-2; Viral Proteins
PubMed: 34668775
DOI: 10.1128/JVI.00964-21 -
BMJ (Clinical Research Ed.) Jan 2022
Review
Topics: Antivenins; Humans; Practice Guidelines as Topic; Primary Health Care; Snake Bites
PubMed: 34996773
DOI: 10.1136/bmj-2020-057926 -
Cell Reports Dec 2022Temperate phages dynamically switch between lysis and lysogeny in their full life cycle. Some Bacillus-infecting phages utilize a quorum-sensing-like intercellular...
Temperate phages dynamically switch between lysis and lysogeny in their full life cycle. Some Bacillus-infecting phages utilize a quorum-sensing-like intercellular communication system, the "arbitrium," to mediate lysis-lysogeny decisions. However, whether additional factors participate in the arbitrium signaling pathway remains largely elusive. Here, we find that the arbitrium signal induces the expression of a functionally conserved operon downstream of the arbitrium module in SPbeta-like phages. SPbeta yopM and yopR (as well as phi3T phi3T_93 and phi3T_97) in the operon play roles in suppressing phage lytic propagation and promoting lysogeny, respectively. We further focus on phi3T_93 and demonstrate that it directly binds antitoxin MazE in the host MazF/MazE toxin-antitoxin (TA) module and facilitates the activation of MazF's toxicity, which is required for phage suppression. These findings show events regulated by the arbitrium system and shed light on how the interplay between phages and the host TA module affects phage-host co-survival.
Topics: Antitoxins; Bacteriophages
PubMed: 36476854
DOI: 10.1016/j.celrep.2022.111752