Analysis of SARS-CoV-2 variant mutations reveals neutralization escape mechanisms and the ability to use ACE2 receptors from additional species.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants continue to emerge during the global pandemic and may facilitate escape from current antibody therapies and vaccine protection. Here we showed that the South African variant B.1.351 was the most resistant to current monoclonal antibodies and convalescent plasma from coronavirus disease 2019 (COVID-19)-infected individuals, followed by the Brazilian variant P.1 and the United Kingdom variant B.1.1.7. This resistance hierarchy corresponded with Y144del and 242-244del mutations in the N-terminal domain and K417N/T, E484K, and N501Y mutations in the receptor-binding domain (RBD) of SARS-CoV-2. Crystal structure analysis of the B.1.351 triple mutant (417N-484K-501Y) RBD complexed with the monoclonal antibody P2C-1F11 revealed the molecular basis for antibody neutralization and escape. B.1.351 and P.1 also acquired the ability to use mouse and mink ACE2 receptors for entry. Our results demonstrate major antigenic shifts and potential broadening of the host range for B.1.351 and P.1 variants, which poses serious challenges to current antibody therapies and vaccine protection.

The PRMT5/WDR77 complex restricts hepatitis E virus replication.

Hepatitis E virus (HEV) is one of the main pathogenic agents of acute hepatitis in the world. The mechanism of HEV replication, especially host factors governing HEV replication is still not clear. Here, using HEV ORF1 trans-complementation cell culture system and HEV replicon system, combining with stable isotope labelling with amino acids in cell culture (SILAC) and mass spectrometry (MS), we aimed to identify the host factors regulating HEV replication. We identified a diversity of host factors associated with HEV ORF1 protein, which were putatively responsible for viral genomic RNA replication, in these two cell culture models. Of note, the protein arginine methyltransferase 5 (PRMT5)/WDR77 complex was identified in both cell culture models as the top hit. Furthermore, we demonstrated that PRMT5 and WDR77 can specifically inhibit HEV replication, but not other viruses such as HCV or SARS-CoV-2, and this inhibition is conserved among different HEV strains and genotypes. Mechanistically, PRMT5/WDR77 can catalyse methylation of ORF1 on its R458, impairing its replicase activity, and virus bearing R458K mutation in ORF1 relieves the restriction of PRMT5/WDR77 accordingly. Taken together, our study promotes more comprehensive understanding of viral infections but also provides therapeutic targets for intervention.

Phase separation of RNA-binding protein promotes polymerase binding and transcription.

An RNA-involved phase-separation model has been proposed for transcription control. However, the molecular links that connect RNA to the transcription machinery remain missing. Here we find that RNA-binding proteins (RBPs) constitute half of the chromatin proteome in embryonic stem cells (ESCs), some being colocalized with RNA polymerase (Pol) II at promoters and enhancers. Biochemical analyses of representative RBPs show that the paraspeckle protein PSPC1 inhibits the RNA-induced premature release of Pol II, and makes use of RNA as multivalent molecules to enhance the formation of transcription condensates and subsequent phosphorylation and release of Pol II. This synergistic interplay enhances polymerase engagement and activity via the RNA-binding and phase-separation activities of PSPC1. In ESCs, auxin-induced acute degradation of PSPC1 leads to genome-wide defects in Pol II binding and nascent transcription. We propose that promoter-associated RNAs and their binding proteins synergize the phase separation of polymerase condensates to promote active transcription.

Functional and genetic analysis of viral receptor ACE2 orthologs reveals a broad potential host range of SARS-CoV-2.

The pandemic of COVID-19, caused by SARS-CoV-2, is a major global health threat. Epidemiological studies suggest that bats (Rhinolophus affinis) are the natural zoonotic reservoir for SARS-CoV-2. However, the host range of SARS-CoV-2 and intermediate hosts that facilitate its transmission to humans remain unknown. The interaction of coronavirus with its host receptor is a key genetic determinant of host range and cross-species transmission. SARS-CoV-2 uses angiotensin-converting enzyme 2 (ACE2) as the receptor to enter host cells in a species-dependent manner. In this study, we characterized the ability of ACE2 from diverse species to support viral entry. By analyzing the conservation of five residues in two virus-binding hotspots of ACE2 (hotspot 31Lys and hotspot 353Lys), we predicted 80 ACE2 proteins from mammals that could potentially mediate SARS-CoV-2 entry. We chose 48 ACE2 orthologs among them for functional analysis, and showed that 44 of these orthologs-including domestic animals, pets, livestock, and animals commonly found in zoos and aquaria-could bind the SARS-CoV-2 spike protein and support viral entry. In contrast, New World monkey ACE2 orthologs could not bind the SARS-CoV-2 spike protein and support viral entry. We further identified the genetic determinant of New World monkey ACE2 that restricts viral entry using genetic and functional analyses. These findings highlight a potentially broad host tropism of SARS-CoV-2 and suggest that SARS-CoV-2 might be distributed much more widely than previously recognized, underscoring the necessity to monitor susceptible hosts to prevent future outbreaks.

Susceptibilities of Human ACE2 Genetic Variants in Coronavirus Infection.

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in more than 235 million cases worldwide and 4.8 million deaths (October 2021), with various incidences and mortalities among regions/ethnicities. The coronaviruses SARS-CoV, SARS-CoV-2, and HCoV-NL63 utilize the angiotensin-converting enzyme 2 (ACE2) as the receptor to enter cells. We hypothesized that the genetic variability in ACE2 may contribute to the variable clinical outcomes of COVID-19. To test this hypothesis, we first conducted an in silico investigation of single-nucleotide polymorphisms (SNPs) in the coding region of ACE2. We then applied an integrated approach of genetics, biochemistry, and virology to explore the capacity of select ACE2 variants to bind coronavirus spike proteins and mediate viral entry. We identified the ACE2 D355N variant that restricts the spike protein-ACE2 interaction and consequently limits infection both in vitro and in vivo. In conclusion, ACE2 polymorphisms could modulate susceptibility to SARS-CoV-2, which may lead to variable disease severity. IMPORTANCE There is considerable variation in disease severity among patients infected with SARS-CoV-2, the virus that causes COVID-19. Human genetic variation can affect disease outcome, and the coronaviruses SARS-CoV, SARS-CoV-2, and HCoV-NL63 utilize human ACE2 as the receptor to enter cells. We found that several missense ACE2 single-nucleotide variants (SNVs) that showed significantly altered binding with the spike proteins of SARS-CoV, SARS-CoV-2, and NL63-HCoV. We identified an ACE2 SNP, D355N, that restricts the spike protein-ACE2 interaction and consequently has the potential to protect individuals against SARS-CoV-2 infection. Our study highlights that ACE2 polymorphisms could impact human susceptibility to SARS-CoV-2, which may contribute to ethnic and geographical differences in SARS-CoV-2 spread and pathogenicity.

Mutation Y453F in the spike protein of SARS-CoV-2 enhances interaction with the mink ACE2 receptor for host adaption.

COVID-19 patients transmitted SARS-CoV-2 to minks in the Netherlands in April 2020. Subsequently, the mink-associated virus (miSARS-CoV-2) spilled back over into humans. Genetic sequences of the miSARS-CoV-2 identified a new genetic variant known as "Cluster 5" that contained mutations in the spike protein. However, the functional properties of these "Cluster 5" mutations have not been well established. In this study, we found that the Y453F mutation located in the RBD domain of miSARS-CoV-2 is an adaptive mutation that enhances binding to mink ACE2 and other orthologs of Mustela species without compromising, and even enhancing, its ability to utilize human ACE2 as a receptor for entry. Structural analysis suggested that despite the similarity in the overall binding mode of SARS-CoV-2 RBD to human and mink ACE2, Y34 of mink ACE2 was better suited to interact with a Phe rather than a Tyr at position 453 of the viral RBD due to less steric clash and tighter hydrophobic-driven interaction. Additionally, the Y453F spike exhibited resistance to convalescent serum, posing a risk for vaccine development. Thus, our study suggests that since the initial transmission from humans, SARS-CoV-2 evolved to adapt to the mink host, leading to widespread circulation among minks while still retaining its ability to efficiently utilize human ACE2 for entry, thus allowing for transmission of the miSARS-CoV-2 back into humans. These findings underscore the importance of active surveillance of SARS-CoV-2 evolution in Mustela species and other susceptible hosts in order to prevent future outbreaks.

A novel cell culture system modeling the SARS-CoV-2 life cycle.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes the global pandemic of COVID-19. SARS-CoV-2 is classified as a biosafety level-3 (BSL-3) agent, impeding the basic research into its biology and the development of effective antivirals. Here, we developed a biosafety level-2 (BSL-2) cell culture system for production of transcription and replication-competent SARS-CoV-2 virus-like-particles (trVLP). This trVLP expresses a reporter gene (GFP) replacing viral nucleocapsid gene (N), which is required for viral genome packaging and virion assembly (SARS-CoV-2 GFP/ΔN trVLP). The complete viral life cycle can be achieved and exclusively confined in the cells ectopically expressing SARS-CoV or SARS-CoV-2 N proteins, but not MERS-CoV N. Genetic recombination of N supplied in trans into viral genome was not detected, as evidenced by sequence analysis after one-month serial passages in the N-expressing cells. Moreover, intein-mediated protein trans-splicing approach was utilized to split the viral N gene into two independent vectors, and the ligated viral N protein could function in trans to recapitulate entire viral life cycle, further securing the biosafety of this cell culture model. Based on this BSL-2 SARS-CoV-2 cell culture model, we developed a 96-well format high throughput screening for antivirals discovery. We identified salinomycin, tubeimoside I, monensin sodium, lycorine chloride and nigericin sodium as potent antivirals against SARS-CoV-2 infection. Collectively, we developed a convenient and efficient SARS-CoV-2 reverse genetics tool to dissect the virus life cycle under a BSL-2 condition. This powerful tool should accelerate our understanding of SARS-CoV-2 biology and its antiviral development.

Comparative analysis reveals the species-specific genetic determinants of ACE2 required for SARS-CoV-2 entry.

Coronavirus interaction with its viral receptor is a primary genetic determinant of host range and tissue tropism. SARS-CoV-2 utilizes ACE2 as the receptor to enter host cell in a species-specific manner. We and others have previously shown that ACE2 orthologs from New World monkey, koala and mouse cannot interact with SARS-CoV-2 to mediate viral entry, and this defect can be restored by humanization of the restrictive residues in New World monkey ACE2. To better understand the genetic determinants behind the ability of ACE2 orthologs to support viral entry, we compared koala and mouse ACE2 sequences with that of human and identified the key residues in koala and mouse ACE2 that restrict viral receptor activity. Humanization of these critical residues rendered both koala and mouse ACE2 capable of binding the spike protein and facilitating viral entry. Our study shed more lights into the genetic determinants of ACE2 as the functional receptor of SARS-CoV-2, which facilitates our understanding of viral entry.

Molecular basis of ligand recognition and transport by glucose transporters.

The major facilitator superfamily glucose transporters, exemplified by human GLUT1-4, have been central to the study of solute transport. Using lipidic cubic phase crystallization and microfocus X-ray diffraction, we determined the structure of human GLUT3 in complex with D-glucose at 1.5 Å resolution in an outward-occluded conformation. The high-resolution structure allows discrimination of both α- and ß-anomers of D-glucose. Two additional structures of GLUT3 bound to the exofacial inhibitor maltose were obtained at 2.6 Å in the outward-open and 2.4 Å in the outward-occluded states. In all three structures, the ligands are predominantly coordinated by polar residues from the carboxy terminal domain. Conformational transition from outward-open to outward-occluded entails a prominent local rearrangement of the extracellular part of transmembrane segment TM7. Comparison of the outward-facing GLUT3 structures with the inward-open GLUT1 provides insights into the alternating access cycle for GLUTs, whereby the C-terminal domain provides the primary substrate-binding site and the amino-terminal domain undergoes rigid-body rotation with respect to the C-terminal domain. Our studies provide an important framework for the mechanistic and kinetic understanding of GLUTs and shed light on structure-guided ligand design.

Early Detection of Severe Acute Respiratory Syndrome Coronavirus 2 Antibodies as a Serologic Marker of Infection in Patients With Coronavirus Disease 2019.

BACKGROUND: Thousands of medical staff have been infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with hundreds of deaths reported. Such loss could be prevented if there were a serologic assay for SARS-CoV-2-specific antibodies for serological surveillance of its infection at the early stage of disease. METHODS: Using Chinese hamster ovarian (CHO) cell-expressed full-length SARS-CoV-2 S1 protein as capturing antigen, a coronavirus disease 2019 (COVID-19)/SARS-CoV-2 S1 serology enzyme-linked immunosorbent assay (ELISA) kit was developed and validated with negative samples collected prior to the outbreak or during the outbreak and positive samples from patients confirmed with COVID-19. RESULTS: The specificity of the ELISA kit was 97.5%, as examined against total 412 normal human samples. The sensitivity was 97.1% by testing against 69 samples from hospitalized and/or recovered COVID-19 patients. The overall accuracy rate reached 97.3%. The assay was able to detect SARS-CoV-2 antibody on day 1 after the onset of COVID-19 disease. The average antibody levels increased during hospitalization and 14 days after discharge. SARS-CoV-2 antibodies were detected in 28 of 276 asymptomatic medical staff and 1 of 5 nucleic acid test-negative "close contacts" of COVID-19 patients. CONCLUSIONS: With the assays developed here, we can screen medical staff, incoming patients, passengers, and people who are in close contact with the confirmed patients to identify the "innocent viral spreaders," protect the medical staff, and stop further spread of the virus.

Novel strategy for expression and characterization of rabies virus glycoprotein.

Rabies is a fatal zoonosis which could affect all mammals. Glycoprotein (G protein) from the rabies virus plays an important role in the binding of virus to target cells. However, expression of the G protein with native conformation has been a great challenge for many years. In this study, we solved this problem by replacing the original signal peptide of rabies virus G protein with the one from the heavy chain of human IgG. The expression levels of recombinant G protein dramatically increased from a few µg/L to 50 mg/L in the culture supernatants. The identity of the recombinant G protein was confirmed by western blotting using both 6XHis mAb 6E2 and rabies G protein mAb 7G3. The correct conformation of the recombinant G protein was shown by using rabies virus neutralizing antibodies. In addition, the recombinant G protein had immune-reactivities with mice sera raised against rabies vaccines and vice versa. Taken together, our data suggested that by replacing the signal peptide, the expression level of the G protein with native conformation could be significantly improved. This would help the development of a rabies subunit vaccine, structural studies of rabies G protein, elucidation of the signal pathway of RABV infection.

Crystal structure of an orthologue of the NaChBac voltage-gated sodium channel.

Voltage-gated sodium (Na(v)) channels are essential for the rapid depolarization of nerve and muscle, and are important drug targets. Determination of the structures of Na(v) channels will shed light on ion channel mechanisms and facilitate potential clinical applications. A family of bacterial Na(v) channels, exemplified by the Na(+)-selective channel of bacteria (NaChBac), provides a useful model system for structure-function analysis. Here we report the crystal structure of Na(v)Rh, a NaChBac orthologue from the marine alphaproteobacterium HIMB114 (Rickettsiales sp. HIMB114; denoted Rh), at 3.05 Å resolution. The channel comprises an asymmetric tetramer. The carbonyl oxygen atoms of Thr 178 and Leu 179 constitute an inner site within the selectivity filter where a hydrated Ca(2+) resides in the crystal structure. The outer mouth of the Na(+) selectivity filter, defined by Ser 181 and Glu 183, is closed, as is the activation gate at the intracellular side of the pore. The voltage sensors adopt a depolarized conformation in which all the gating charges are exposed to the extracellular environment. We propose that Na(v)Rh is in an 'inactivated' conformation. Comparison of Na(v)Rh with Na(v)Ab reveals considerable conformational rearrangements that may underlie the electromechanical coupling mechanism of voltage-gated channels.

[Control rate of increased low-density lipoprotein cholesterol levels in cardiology outpatients with coronary heart disease in Beijing].

OBJECTIVE: To investigate the low-density lipoprotein cholesterol (LDL-C) levels in outpatients with coronary heart disease (CHD) visiting cardiology outpatient clinics of 8 hospitals in Beijing. METHODS: A total of 903 outpatients with CHD were enrolled from 4 three-tier hospitals and 4 two-tier hospitals in Beijing. All patients were asked to finish the questionnaire including demographic data, CHD history, the knowledge on cholesterol, and the use of statins. Blood lipid was examined and the LDL-C control rate and related factors were then analyzed. RESULTS: Questionnaire was obtained from 876 patients [619 male: 70.7%, mean age: (64.9 ± 10.7) years old] and blood lipid data were available in 709 patients. The general LDL-C control rate was 36.9% (262/709) and was 13.5% (27/173) in very high risk CHD patients, and lower in patients treated in two-tier hospitals than patients treated in three-tier hospitals[31.3% (121/386) vs. 43.7% (141/323), P < 0.01], in female patients than in male patients [27.1% (60/261) vs. 41.3% (201/496), P < 0.01] and in diabetic patients than in non-diabetic patients [13.5% (27/200) vs. 44.7% (197/441), P < 0.01]. The LDL-C control rate was lower in patients less than 60 years old and patients over 80 years old than that in 60-70 years old patients and 70 - 80 years old patients (P < 0.05). LDL-C control rate was not affected by the history of hypertension, percutaneous coronary intervention or coronary artery bypass grafting, smoking, lipid examination frequency, knowledge on goal level of LDL-C, diet control and regularly physical exercising (all P > 0.05). There were 18.2% (129/709) patients not taking statins or not aware if they were taking statin or not. The main reason for not taking statin [47.9% (23/48)] was statin was no prescribed by doctors, followed by withdrawal by patients due to various reasons [27.1% (13/48)]. CONCLUSIONS: LDL-C control rate was low in patients with CHD visiting cardiology outpatient clinics in Beijing. The CHD patients and cardiologists should be encouraged to achieve better LDL-C control by following lipid lowering guidelines and it is also important to improve the drug compliance among CHD patients.

SARS-CoV-2 main protease cleaves MAGED2 to antagonize host antiviral defense.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the agent causing the global pandemic of COVID-19. SARS-CoV-2 genome encodes a main protease (nsp5, also called Mpro) and a papain-like protease (nsp3, also called PLpro), which are responsible for processing viral polyproteins to assemble a functional replicase complex. In this study, we found that Mpro of SARS-CoV-2 can cleave human MAGED2 and other mammalian orthologs at Gln-263. Moreover, SARS-CoV and MERS-CoV Mpro can also cleave human MAGED2, suggesting MAGED2 cleavage by Mpro is an evolutionarily conserved mechanism of coronavirus infection in mammals. Intriguingly, Mpro from Beta variant cleaves MAGED2 more efficiently than wild type, but Omicron Mpro is opposite. Further studies show that MAGED2 inhibits SARS-CoV-2 infection at viral replication step. Mechanistically, MAGED2 is associated with SARS-CoV-2 nucleocapsid protein through its N-terminal region in an RNA-dependent manner, and this disrupts the interaction between SARS-CoV-2 nucleocapsid protein and viral genome, thus inhibiting viral replication. When MAGED2 is cleaved by Mpro, the N-terminal of MAGED2 will translocate into the nucleus, and the truncated MAGED2 is unable to suppress SARS-CoV-2 replication. This work not only discovers the antiviral function of MAGED2 but also provides new insights into how SARS-CoV-2 Mpro antagonizes host antiviral response. IMPORTANCE Host factors that restrict severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection remain elusive. Here, we found that MAGED2 can be cleaved by SARS-CoV-2 main protease (Mpro) at Gln-263. SARS-CoV and MERS-CoV Mpro can also cleave MAGED2, and MAGED2 from multiple species can be cleaved by SARS-CoV-2 Mpro. Mpro from Beta variant cleaves MAGED2 more efficiently efficiently than wild type, but Omicron is the opposite. MAGED2 depletion enhances SARS-CoV-2 infection, suggesting its inhibitory role in SARS-CoV-2 infection. Mechanistically, MAGED2 restricts SARS-CoV-2 replication by disrupting the interaction between nucleocapsid and viral genomes. When MAGED2 is cleaved, its N-terminal will translocate into the nucleus. In this way, Mpro relieves MAGED2' inhibition on viral replication. This study improves our understanding of complex viral-host interaction and provides novel targets to treat SARS-CoV-2 infection.

Evolution of Immune Evasion and Host Range Expansion by the SARS-CoV-2 B.1.1.529 (Omicron) Variant.

Recently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant B.1.1.529 (Omicron) has rapidly become the dominant strain, with an unprecedented number of mutations within its spike gene. However, it remains unknown whether these variants have alterations in their entry efficiency, host tropism, and sensitivity to neutralizing antibodies and entry inhibitors. In this study, we found that Omicron spike has evolved to escape neutralization by three-dose inactivated-vaccine-elicited immunity but remains sensitive to an angiotensin-converting enzyme 2 (ACE2) decoy receptor. Moreover, Omicron spike could use human ACE2 with a slightly increased efficiency while gaining a significantly increased binding affinity for a mouse ACE2 ortholog, which exhibits limited binding with wild-type (WT) spike. Furthermore, Omicron could infect wild-type C57BL/6 mice and cause histopathological changes in the lungs. Collectively, our results reveal that evasion of neutralization by vaccine-elicited antibodies and enhanced human and mouse ACE2 receptor engagement may contribute to the expanded host range and rapid spread of the Omicron variant. IMPORTANCE The recently emerged SARS-CoV-2 Omicron variant with numerous mutations in the spike protein has rapidly become the dominant strain, thereby raising concerns about the effectiveness of vaccines. Here, we found that the Omicron variant exhibits a reduced sensitivity to serum neutralizing activity induced by a three-dose inactivated vaccine but remains sensitive to entry inhibitors or an ACE2-Ig decoy receptor. Compared with the ancestor strain isolated in early 2020, the spike protein of Omicron utilizes the human ACE2 receptor with enhanced efficiency while gaining the ability to utilize mouse ACE2 for cell entry. Moreover, Omicron could infect wild-type mice and cause pathological changes in the lungs. These results reveal that antibody evasion, enhanced human ACE2 utilization, and an expanded host range may contribute to its rapid spread.

Mpox vaccine and infection-driven human immune signatures.

Background: Mpox (formerly known as monkeypox) outbreaks outside endemic areas peaked in July 2022, infecting > 85,000 people and raising concerns about our preparedness against this emerging viral pathogen. Licensed and approved for mpox, the JYNNEOS vaccine has fewer side effects than previous smallpox vaccines and demonstrated efficacy against mpox infection in humans. Comparing JYNNEOS vaccine- and mpox-induced immunity is imperative to evaluate JYNNEOS' immunogenicity and inform vaccine administration and design. Methods: We examined the polyclonal serum (ELISA) and single B cell (heavy chain gene and transcriptome data) antibody repertoires and T cells (AIM and ICS assays) induced by the JYNNEOS vaccine as well as mpox infection. Findings: Gene-level plasmablast and antibody responses were negligible and JYNNEOS vaccinee sera displayed minimal binding to recombinant mpox proteins and native proteins from the 2022 outbreak strain. In contrast, recent mpox infection (within 20-102 days) induced robust serum antibody responses to A29L, A35R, A33R, B18R, and A30L, and to native mpox proteins, compared to vaccinees. JYNNEOS vaccine recipients presented comparable CD4 and CD8 T cell responses against orthopox peptides to those observed after mpox infection. Interpretation: JYNNEOS immunization does not elicit a robust B cell response, and its immunogenicity may be mediated by T cells. Funding: Research reported in this publication was supported, in part, by the National Cancer Institute of the National Institutes of Health under Award Number U54CA267776, U19AI168631(VS), as well as institutional funds from the Icahn School of Medicine.

Mpox vaccine and infection-driven human immune signatures: an immunological analysis of an observational study.

BACKGROUND: Monkeypox virus has recently infected more than 88 000 people, raising concerns about our preparedness against this emerging viral pathogen. Licensed and approved for mpox, the JYNNEOS vaccine has fewer side-effects than previous smallpox vaccines and has shown immunogenicity against monkeypox in animal models. This study aims to elucidate human immune responses to JYNNEOS vaccination compared with mpox-induced immunity. METHODS: Peripheral blood mononuclear cells and sera were obtained from ten individuals vaccinated with one or two doses of JYNNEOS and six individuals diagnosed with monkeypox virus infection. Samples were obtained from seven individuals before vaccination to serve as a baseline. We examined the polyclonal serum (ELISA) and single B-cell (heavy chain gene and transcriptome data) antibody repertoires and T-cell responses (activation-induced marker and intracellular cytokine staining assays) induced by the JYNNEOS vaccine versus monkeypox virus infection. FINDINGS: All participants were men between the ages of 21 and 60 years, except for one woman in the group of mpox-convalescent individuals, and none had previous orthopoxvirus exposure. All mpox cases were mild. Vaccinee samples were collected 6-33 days after the first dose and 5-40 days after the second dose. Mpox-convalescent samples were collected 20-102 days after infection. In vaccine recipients, gene-level plasmablast and antibody responses were negligible and sera displayed moderate binding to recombinant orthopoxviral proteins (A29L, A35R, E8L, A30L, A27L, A33R, B18R, and L1R) and native proteins from the 2022 monkeypox outbreak strain. By contrast, recent monkeypox virus infection (within 20-102 days) induced robust serum antibody responses to monkeypox virus proteins and to native monkeypox virus proteins from a viral isolate obtained during the 2022 outbreak. JYNNEOS vaccine recipients presented robust orthopoxviral CD4+ and CD8+ T-cell responses. INTERPRETATION: Infection with monkeypox virus resulted in robust B-cell and T-cell responses, whereas immunisation with JYNNEOS elicited more robust T-cell responses. These data can help to inform vaccine design and policies for preventing mpox in humans. FUNDING: National Cancer Institute (National Institutes of Health), National Institute of Allergy and Infectious Diseases (National Institutes of Health), and Icahn School of Medicine.

Structural insights into the binding of SARS-CoV-2, SARS-CoV, and hCoV-NL63 spike receptor-binding domain to horse ACE2.

Severe acute respiratory syndrome coronavirus (SARS-CoV), SARS-CoV-2, and human coronavirus (hCoV)-NL63 utilize ACE2 as the functional receptor for cell entry, which leads to zoonotic infection. Horses (Equus caballus) attracted our attention because the spike protein receptor-binding domains (RBDs) of SARS-CoV-2 and SARS-CoV-2-related coronaviruses bind equine ACE2 (eACE2) with high affinity. Here we show that eACE2 binds the RBDs of these three coronaviruses and also SARS-CoV-2 variants but with lower affinities compared with human ACE2 (hACE2). Structural analysis and mutation assays indicated that eACE2-H41 accounts for the lower binding affinity of eACE2 to the RBDs of SARS-CoV-2 variants (Alpha, Beta, and Gamma), SARS-CoV, and hCoV-NL63. Pseudovirus infection assays showed that the SARS-CoV-2 Delta strain (B.1.617.2) displayed a significantly increased infection efficiency in eACE2-expressing HeLa cells. Our results reveal the molecular basis of eACE2 binding to the RBDs of SARS-CoV, SARS-CoV-2, and hCoV-NL63, which provides insights into the potential animal transmission of these ACE2-dependent coronaviruses.

Characterization of SARS-CoV-2 Variants B.1.617.1 (Kappa), B.1.617.2 (Delta), and B.1.618 by Cell Entry and Immune Evasion.

Recently, highly transmissible severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants B.1.617.1 (Kappa), B.1.617.2 (Delta), and B.1.618 with mutations within the spike proteins were identified in India. The spike protein of Kappa contains the four mutations E154K, L452R, E484Q, and P681R, and Delta contains L452R, T478K, and P681R, while B.1.618 spike harbors mutations Δ145-146 and E484K. However, it remains unknown whether these variants have alterations in their entry efficiency, host tropism, and sensitivity to neutralizing antibodies as well as entry inhibitors. In this study, we found that Kappa, Delta, or B.1.618 spike uses human angiotensin-converting enzyme 2 (ACE2) with no or slightly increased efficiency, while it gains a significantly increased binding affinity with mouse, marmoset, and koala ACE2 orthologs, which exhibit limited binding with wild-type (WT) spike. Furthermore, the P681R mutation leads to enhanced spike cleavage, which could facilitate viral entry. In addition, Kappa, Delta, and B.1.618 exhibit a reduced sensitivity to neutralization by convalescent-phase sera due to the mutation E484Q, T478K, Δ145-146, or E484K, but remain sensitive to entry inhibitors such as ACE2-Ig decoy receptor. Collectively, our study revealed that enhanced human and mouse ACE2 receptor engagement, increased spike cleavage, and reduced sensitivity to neutralization antibodies of Kappa, Delta and B.1.618 may contribute to the rapid spread of these variants. Furthermore, our results also highlight that ACE2-Ig could be developed as a broad-spectrum antiviral strategy against SARS-CoV-2 variants. IMPORTANCE SARS-CoV-2, the causative agent of pandemic COVID-19, is rapidly evolving to be more transmissible and to exhibit evasive immune properties, compromising neutralization by antibodies from vaccinated individuals or convalescent-phase sera. Recently, SARS-CoV-2 variants B.1.617.1 (Kappa), B.1.617.2 (Delta), and B.1.618 with mutations within the spike proteins were identified in India. In this study, we examined cell entry efficiencies of Kappa, Delta, and B.1.618. In addition, the variants, especially the Delta variant, exhibited expanded capabilities to use mouse, marmoset, and koala ACE2 for entry. Convalescent sera from patients infected with nonvariants showed reduced neutralization titers among the Kappa, Delta, and B.1.618 variants. Furthermore, the variants remain sensitive to ACE2-Ig decoy receptor. Our study thus could facilitate understanding how variants have increased transmissibility and evasion of established immunity and also could highlight the use of an ACE2 decoy receptor as a broad-spectrum antiviral strategy against SARS-CoV-2 variants.

Next generation of anti-PD-L1 Atezolizumab with enhanced anti-tumor efficacy in vivo.

FDA-approved anti-PD-L1 antibody drug Atezolizumab is a human IgG1 without glycosylation by an N297A mutation. Aglycosylation of IgG1 has been used to completely remove the unwanted Fc-mediated functions such as antibody-dependent cytotoxicity (ADCC). However, aglycosylated Atezolizumab is very unstable and easy to form aggregation, which causes quick development of anti-drug antibody (ADA) in 41% of Atezolizumab-treated cancer patients, eventually leading to loss of efficacy. Here, we report the development of the anti-PD-L1 antibody drug Maxatezo, a glycosylated version of Atezolizumab, with no ADCC activity, better thermo-stability, and significantly improved anti-tumor activity in vivo. Using Atezolizumab as the starting template, we back-mutated A297N to re-install the glycosylation, and inserted a short, flexible amino acid sequence (GGGS) between G237 and G238 in the hinge region of the IgG1 heavy chain. Our data shows that insertion of GGGS, does not alter the anti-PD-L1's affinity and inhibitory activity, while completely abolishing ADCC activity. Maxatezo has a similar glycosylation profile and expression level (up to 5.4 g/L) as any normal human IgG1. Most importantly, Maxatezo's thermal stability is much better than Atezolizumab, as evidenced by dramatic increases of Tm1 from 63.55 °C to 71.01 °C and Tagg from 60.7 °C to 71.2 °C. Furthermore, the levels of ADA in mice treated with Maxatezo were significantly lower compared with animals treated with Atezolizumab. Most importantly, at the same dose (10 mg/kg), the tumor growth inhibition rate of Maxatezo was 98%, compared to 68% for Atezolizumab.