scholarly journals Pathogenicity, immunogenicity, and protective ability of an attenuated SARS-CoV-2 variant with a deletion at the S1/S2 junction of the spike protein

2020 ◽  
Author(s):  
Pui Wang ◽  
Siu-Ying Lau ◽  
Shaofeng Deng ◽  
Pin Chen ◽  
Bobo Mok ◽  
...  
Keyword(s):  
Lower Respiratory Tract ◽  
Neutralizing Antibody ◽  
Spike Protein ◽  
Wild Type Virus ◽  
Wild Type ◽  
Protective Ability ◽  
Cleavage Motif ◽  
Sterilizing Immunity

Abstract SARS-CoV-2 is zoonotic origin and contains a PRRA polybasic cleavage motif which is considered critical for efficient infection and transmission in humans. We previously reported on a panel of attenuated SARS-CoV-2 variants with deletion at the S1/S2 junction of spike protein. Here we characterize pathogenicity, immunogenicity, and protective ability of a further cell-adapted SARS-CoV-2 variant, Ca-DelMut, in in vitro and in vivo systems. Ca-DelMut replicates more efficiently than wild type or parental virus in cells, but causes no apparent disease in hamsters, despite replicating in respiratory tissues. Unlike wild type virus, Ca-DelMut causes no apparent pathological changes and does not induce elevated proinflammatory cytokines in hamster infections, but still triggers a strong neutralizing antibody response in hamsters. Ca-DelMut immunized hamsters challenged with wild type SARS-CoV-2 are fully protected with no sign of virus replication in the upper or lower respiratory tract of challenged animals, demonstrating sterilizing immunity.

scholarly journals Characterization of an attenuated SARS-CoV-2 variant with a deletion at the S1/S2 junction of the spike protein

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Pui Wang ◽  
Siu-Ying Lau ◽  
Shaofeng Deng ◽  
Pin Chen ◽  
Bobo Wing-Yee Mok ◽  
...  
Keyword(s):  
Neutralizing Antibody ◽  
T Cell Response ◽  
Spike Protein ◽  
Wild Type Virus ◽  
Wild Type ◽  
Cleavage Motif ◽  
Sterilizing Immunity

AbstractSARS-CoV-2 is of zoonotic origin and contains a PRRA polybasic cleavage motif which is considered critical for efficient infection and transmission in humans. We previously reported on a panel of attenuated SARS-CoV-2 variants with deletions at the S1/S2 junction of the spike protein. Here, we characterize pathogenicity, immunogenicity, and protective ability of a further cell-adapted SARS-CoV-2 variant, Ca-DelMut, in in vitro and in vivo systems. Ca-DelMut replicates more efficiently than wild type or parental virus in Vero E6 cells, but causes no apparent disease in hamsters, despite replicating in respiratory tissues. Unlike wild type virus, Ca-DelMut causes no obvious pathological changes and does not induce elevation of proinflammatory cytokines, but still triggers a strong neutralizing antibody and T cell response in hamsters and mice. Ca-DelMut immunized hamsters challenged with wild type SARS-CoV-2 are fully protected, with little sign of virus replication in the upper or lower respiratory tract, demonstrating sterilizing immunity.

scholarly journals Pathogenicity, immunogenicity, and protective ability of an attenuated SARS-CoV-2 variant with a deletion at the S1/S2 junction of the spike protein

2020 ◽  
Author(s):  
Pui Wang ◽  
Siu-Ying Lau ◽  
Shaofeng Deng ◽  
Pin Chen ◽  
Bobo Wing-Yee Mok ◽  
...  
Keyword(s):  
Antibody Response ◽  
Proinflammatory Cytokines ◽  
Neutralizing Antibody ◽  
Spike Protein ◽  
Parental Virus ◽  
Wild Type Virus ◽  
Type Virus ◽  
Wild Type ◽  
Cleavage Motif ◽  
Sterilizing Immunity

AbstractSARS-CoV-2 contains a PRRA polybasic cleavage motif considered critical for efficient infection and transmission in humans. We previously reported that virus variants with spike protein S1/S2 junction deletions spanning this motif are attenuated. Here we characterize a further cell-adapted SARS-CoV-2 variant, Ca-DelMut. Ca-DelMut replicates more efficiently than wild type or parental virus in cells, but causes no apparent disease in hamsters, despite replicating in respiratory tissues. Unlike wild type virus, Ca-DelMut does not induce proinflammatory cytokines in hamster infections, but still triggers a strong neutralizing antibody response. Ca-DelMut-immunized hamsters challenged with wild type SARS-CoV-2 are fully protected, demonstrating sterilizing immunity.

scholarly journals Vaccinia Virus Envelope H3L Protein Binds to Cell Surface Heparan Sulfate and Is Important for Intracellular Mature Virion Morphogenesis and Virus Infection In Vitro and In Vivo

2000 ◽  
Vol 74 (7) ◽  
pp. 3353-3365 ◽  
Author(s):  
Chi-Long Lin ◽  
Che-Sheng Chung ◽  
Hans G. Heine ◽  
Wen Chang
Keyword(s):  
Cell Surface ◽  
Vaccinia Virus ◽  
Heparan Sulfate ◽  
Mutant Virus ◽  
Wild Type Virus ◽  
Type Virus ◽  
Wild Type ◽  
Virion Morphogenesis

ABSTRACT An immunodominant antigen, p35, is expressed on the envelope of intracellular mature virions (IMV) of vaccinia virus. p35 is encoded by the viral late gene H3L, but its role in the virus life cycle is not known. This report demonstrates that soluble H3L protein binds to heparan sulfate on the cell surface and competes with the binding of vaccinia virus, indicating a role for H3L protein in IMV adsorption to mammalian cells. A mutant virus defective in expression of H3L (H3L−) was constructed; the mutant virus has a small plaque phenotype and 10-fold lower IMV and extracellular enveloped virion titers than the wild-type virus. Virion morphogenesis is severely blocked and intermediate viral structures such as viral factories and crescents accumulate in cells infected with the H3L− mutant virus. IMV from the H3L− mutant virus are somewhat altered and less infectious than wild-type virions. However, cells infected by the mutant virus form multinucleated syncytia after low pH treatment, suggesting that H3L protein is not required for cell fusion. Mice inoculated intranasally with wild-type virus show high mortality and severe weight loss, whereas mice infected with H3L− mutant virus survive and recover faster, indicating that inactivation of the H3L gene attenuates virus virulence in vivo. In summary, these data indicate that H3L protein mediates vaccinia virus adsorption to cell surface heparan sulfate and is important for vaccinia virus infection in vitro and in vivo. In addition, H3L protein plays a role in virion assembly.

scholarly journals Production of Noncapped Genomic RNAs Is Critical to Sindbis Virus Disease and Pathogenicity

mBio ◽  
2020 ◽  
Vol 11 (6) ◽  
Author(s):  
Autumn T. LaPointe ◽  
V Douglas Landers ◽  
Claire E. Westcott ◽  
Kevin J. Sokoloski
Keyword(s):  
Sindbis Virus ◽  
Virus Disease ◽  
Severe Disease ◽  
Wild Type Virus ◽  
Wild Type ◽  
Genomic Rnas ◽  
Mortality And Morbidity ◽  
The Impact

ABSTRACT Alphaviruses are positive-sense RNA viruses that utilize a 5′ cap structure to facilitate translation of viral proteins and to protect the viral RNA genome. Nonetheless, significant quantities of viral genomic RNAs that lack a canonical 5′ cap structure are produced during alphaviral replication and packaged into viral particles. However, the role/impact of the noncapped genomic RNA (ncgRNA) during alphaviral infection in vivo has yet to be characterized. To determine the importance of the ncgRNA in vivo, the previously described D355A and N376A nsP1 mutations, which increase or decrease nsP1 capping activity, respectively, were incorporated into the neurovirulent AR86 strain of Sindbis virus to enable characterization of the impact of altered capping efficiency in a murine model of infection. Mice infected with the N376A nsP1 mutant exhibited slightly decreased rates of mortality and delayed weight loss and neurological symptoms, although levels of inflammation in the brain were similar to those of wild-type infection. Although the D355A mutation resulted in decreased antiviral gene expression and increased resistance to interferon in vitro, mice infected with the D355A mutant showed significantly reduced mortality and morbidity compared to mice infected with wild-type virus. Interestingly, expression of proinflammatory cytokines was found to be significantly decreased in mice infected with the D355A mutant, suggesting that capping efficiency and the production of ncgRNA are vital to eliciting pathogenic levels of inflammation. Collectively, these data indicate that the ncgRNA have important roles during alphaviral infection and suggest a novel mechanism by which noncapped viral RNAs aid in viral pathogenesis. IMPORTANCE Mosquito-transmitted alphaviruses have been the cause of widespread outbreaks of disease that can range from mild illness to lethal encephalitis or severe polyarthritis. There are currently no safe and effective vaccines or therapeutics with which to prevent or treat alphaviral disease, highlighting the need to better understand alphaviral pathogenesis to develop novel antiviral strategies. This report reveals production of noncapped genomic RNAs (ncgRNAs) to be a novel determinant of alphaviral virulence and offers insight into the importance of inflammation to pathogenesis. Taken together, the findings reported here suggest that the ncgRNAs contribute to alphaviral pathogenesis through the sensing of the ncgRNAs during alphaviral infection and are necessary for the development of severe disease.

scholarly journals Inhibition of Cellular Proteasome Activities Enhances Hepadnavirus Replication in an HBX-Dependent Manner

2004 ◽  
Vol 78 (9) ◽  
pp. 4566-4572 ◽  
Author(s):  
Zhensheng Zhang ◽  
Ulrike Protzer ◽  
Zongyi Hu ◽  
James Jacob ◽  
T. Jake Liang
Keyword(s):  
Recombinant Adenovirus ◽  
Hepatitis Virus ◽  
Proteasome Inhibitors ◽  
Productive Infection ◽  
Wild Type Virus ◽  
Dependent Manner ◽  
Type Virus ◽  
Wild Type

ABSTRACT The X protein (HBX) of the hepatitis B virus (HBV) is not essential for the HBV life cycle in vitro but is important for productive infection in vivo. Our previous study suggests that interaction of HBX with the proteasome complex may underlie the pleiotropic functions of HBX. With the woodchuck model, we demonstrated that the X-deficient mutants of woodchuck hepatitis virus (WHV) are not completely replication defective, possibly behaving like attenuated viruses. In the present study, we analyzed the effects of the proteasome inhibitors on the replication of wild-type and X-negative HBV and WHV. Recombinant adenoviruses or baculoviruses expressing replicating HBV or WHV genomes have been developed as a robust and convenient system to study viral replication in tissue culture. In cells infected with either the recombinant adenovirus-HBV or baculovirus-WHV, the replication level of the X-negative construct was about 10% of that of the wild-type virus. In the presence of proteasome inhibitors, the replication of the wild-type virus was not affected, while the replication of the X-negative virus of either HBV or WHV was enhanced and restored to the wild-type level. Our data suggest that HBX affects hepadnavirus replication through a proteasome-dependent pathway.

scholarly journals Discordance between Bovine Leukemia Virus Tax Immortalization In Vitro and Oncogenicity In Vivo

2000 ◽  
Vol 74 (21) ◽  
pp. 9895-9902 ◽  
Author(s):  
Jean-Claude Twizere ◽  
Pierre Kerkhofs ◽  
Arsène Burny ◽  
Daniel Portetelle ◽  
Richard Kettmann ◽  
...  
Keyword(s):  
Viral Replication ◽  
Bovine Leukemia Virus ◽  
Leukemia Virus ◽  
Wild Type Virus ◽  
Target Cells ◽  
Phosphorylation Sites ◽  
Primary Cells ◽  
Wild Type

ABSTRACT Bovine leukemia virus (BLV) Tax protein, a transcriptional activator of viral expression, is essential for viral replication in vivo. Tax is believed to be involved in leukemogenesis because of its second function, immortalization of primary cells in vitro. These activities of Tax can be dissociated on the basis of point mutations within specific regions of the protein. For example, mutation of the phosphorylation sites at serines 106 and 293 abrogates immortalization potential in vitro but maintains transcriptional activity. This type of mutant is thus particularly useful for unraveling the role of Tax immortalization activity during leukemogenesis independently of viral replication. In this report, we describe the biological properties of BLV recombinant proviruses mutated in the Tax phosphorylation sites (BLVTax106+293). Titration of the proviral loads by semiquantitative PCR revealed that the BLV mutants propagated at wild-type levels in vivo. Furthermore, two animals (sheep 480 and 296) infected with BLVTax106+293 developed leukemia or lymphosarcoma after 16 and 36 months, respectively. These periods of time are within the normal range of latencies preceding the onset of pathogenesis induced by wild-type viruses. The phenotype of the mutant-infected cells was characteristic of a B lymphocyte (immunoglobulin M positive) expressing CD11b and CD5 (except at the final stage for the latter marker), a pattern that is typical of wild-type virus-infected target cells. Interestingly, the transformed B lymphocytes from sheep 480 also coexpressed the CD8 marker, a phenotype rarely observed in tumor biopsies from chronic lymphocytic leukemia patients. Finally, direct sequencing of the tax gene demonstrated that the leukemic cells did not harbor revertant proviruses. We conclude that viruses expressing a Tax mutant unable to transform primary cells in culture are still pathogenic in the sheep animal model. Our data thus provide a clear example of the discordant conclusions that can be drawn from in vitro immortalization assays and in vivo experiments. These observations could be of interest for other systems, such as the related human T-cell leukemia virus type 1, which currently lack animal models allowing the study of the leukemogenic process.

scholarly journals Targeting Human Immunodeficiency Virus (HIV) Type 2 Integrase Protein into HIV Type 1

1999 ◽  
Vol 73 (10) ◽  
pp. 8831-8836 ◽  
Author(s):  
Hongmei Liu ◽  
Xiaoyun Wu ◽  
Hongling Xiao ◽  
John C. Kappes
Keyword(s):  
Human Immunodeficiency Virus ◽  
Reverse Transcription ◽  
Wild Type Virus ◽  
Strand Transfer ◽  
Wild Type ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Integrase (IN) is the only retroviral enzyme necessary for the integration of retroviral cDNA into the host cell’s chromosomes. The structure and function of IN is highly conserved. The human immunodeficiency virus type 2 (HIV-2) IN has been shown to efficiently support 3′ processing and strand transfer of HIV-1 DNA substrate in vitro. To determine whether HIV-2 IN protein (IN2) could substitute for HIV-1 IN function in vivo, we used HIV-1 Vpr to deliver the IN2 into IN mutant HIV-1 virions by expression intrans as a Vpr-IN fusion protein.Trans-complementation with IN2 markedly increased the infectivity of IN-minus HIV-1. Compared with the homologous trans-IN protein, infectivity was increased to a level of 16%. Since IN has been found to play a role in reverse transcription (Wu et al., J. Virol. 73:2126–2135, 1999), cells infected with IN2-complemented HIV-1 were analyzed for DNA products of reverse transcription. DNA levels of approximately 18% of that of wild type were detected. The homologous trans-IN protein restored the synthesis of viral cDNA to approximately 86% of that of wild-type virus. By complementing integration-defective HIV-1 IN mutant viruses, which were not impaired in cDNA synthesis, thetrans-IN2 protein was shown to support integration up to a level of 55% compared with that of the homologoustrans-IN protein. The delivery of heterologous IN protein into HIV-1 particles in trans offers a novel approach to understand IN protein function in vivo.

scholarly journals Ultrapotent bispecific antibodies neutralize emerging SARS-CoV-2 variants

2021 ◽  
Author(s):  
Hyeseon Cho ◽  
Kristina Kay Gonzales-Wartz ◽  
Deli Huang ◽  
Meng Yuan ◽  
Mary Peterson ◽  
...  
Keyword(s):  
Bispecific Antibody ◽  
Complete Loss ◽  
Memory B Cells ◽  
Spike Protein ◽  
Bispecific Antibodies ◽  
Wild Type Virus ◽  
Type Virus ◽  
Wild Type ◽  
Hamster Model

The emergence of SARS-CoV-2 variants that threaten the efficacy of existing vaccines and therapeutic antibodies underscores the urgent need for new antibody-based tools that potently neutralize variants by targeting multiple sites of the spike protein. We isolated 216 monoclonal antibodies targeting SARS-CoV-2 from plasmablasts and memory B cells of COVID-19 patients. The three most potent antibodies targeted distinct regions of the RBD, and all three neutralized the SARS-CoV-2 variants B.1.1.7 and B.1.351. The crystal structure of the most potent antibody, CV503, revealed that it binds to the ridge region of SARS-CoV-2 RBD, competes with the ACE2 receptor, and has limited contact with key variant residues K417, E484 and N501. We designed bispecific antibodies by combining non-overlapping specificities and identified five ultrapotent bispecific antibodies that inhibit authentic SARS-CoV-2 infection at concentrations of <1 ng/mL. Through a novel mode of action three bispecific antibodies cross-linked adjacent spike proteins using dual NTD/RBD specificities. One bispecific antibody was >100-fold more potent than a cocktail of its parent monoclonals in vitro and prevented clinical disease in a hamster model at a 2.5 mg/kg dose. Notably, six of nine bispecific antibodies neutralized B.1.1.7, B.1.351 and the wild-type virus with comparable potency, despite partial or complete loss of activity of at least one parent monoclonal antibody against B.1.351. Furthermore, a bispecific antibody that neutralized B.1.351 protected against SARS-CoV-2 expressing the crucial E484K mutation in the hamster model. Thus, bispecific antibodies represent a promising next-generation countermeasure against SARS-CoV-2 variants of concern.

scholarly journals Residues in the Heptad Repeat A Region of the Fusion Protein Modulate the Virulence of Sendai Virus in Mice

2009 ◽  
Vol 84 (2) ◽  
pp. 810-821 ◽  
Author(s):  
Laura E. Luque ◽  
Olga A. Bridges ◽  
John N. Mason ◽  
Kelli L. Boyd ◽  
Allen Portner ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Sendai Virus ◽  
Syncytium Formation ◽  
Heptad Repeat ◽  
Wild Type Virus ◽  
Type Virus ◽  
Wild Type ◽  
F Protein

ABSTRACT While the molecular basis of fusion (F) protein refolding during membrane fusion has been studied extensively in vitro, little is known about the biological significance of membrane fusion activity in parainfluenza virus replication and pathogenesis in vivo. Two recombinant Sendai viruses, F-L179V and F-K180Q, were generated that contain F protein mutations in the heptad repeat A region of the ectodomain, a region of the protein known to regulate F protein activation. In vitro, the F-L179V virus caused increased syncytium formation (cell-cell membrane fusion) yet had a rate of replication and levels of F protein expression and cleavage similar to wild-type virus. The F-K180Q virus had a reduced replication rate along with reduced levels of F protein expression, cleavage, and fusogenicity. In DBA/2 mice, the hyperfusogenic F-L179V virus induced greater morbidity and mortality than wild-type virus, while the attenuated F-K180Q virus was much less pathogenic. During the first week of infection, virus replication and inflammation in the lungs were similar for wild-type and F-L179V viruses. After approximately 1 week of infection, the clearance of F-L179V virus was delayed, and more extensive interstitial inflammation and necrosis were observed in the lungs, affecting entire lobes of the lungs and having significantly greater numbers of syncytial cell masses in alveolar spaces on day 10. On the other hand, the slower-growing F-K180Q virus caused much less extensive inflammation than wild-type virus, presumably due to its reduced replication rate, and did not cause observable syncytium formation in the lungs. Overall, the results show that residues in the heptad repeat A region of the F protein modulate the virulence of Sendai virus in mice by influencing both the spread and clearance of the virus and the extent and severity of inflammation. An understanding of how the F protein contributes to infection and inflammation in vivo may assist in the development of antiviral therapies against respiratory paramyxoviruses.

scholarly journals Recombinant Respiratory Syncytial Virus That Does Not Express the NS1 or M2-2 Protein Is Highly Attenuated and Immunogenic in Chimpanzees

2000 ◽  
Vol 74 (19) ◽  
pp. 9317-9321 ◽  
Author(s):  
Michael N. Teng ◽  
Stephen S. Whitehead ◽  
Alison Bermingham ◽  
Marisa St. Claire ◽  
William R. Elkins ◽  
...  
Keyword(s):  
Protective Efficacy ◽  
Neutralizing Antibody ◽  
Target Population ◽  
Large Deletion ◽  
Upper Respiratory Tract ◽  
Wild Type ◽  
Upper Respiratory ◽  
Syncytial Virus

ABSTRACT Mutant recombinant respiratory syncytial viruses (RSV) which cannot express the NS1 and M2-2 proteins, designated rA2ΔNS1 and rA2ΔM2-2, respectively, were evaluated as live-attenuated RSV vaccines. The rA2ΔNS1 virus contains a large deletion that should have the advantageous property of genetic stability during replication in vitro and in vivo. In vitro, rA2ΔNS1 replicated approximately 10-fold less well than wild-type recombinant RSV (rA2), while rA2ΔM2-2 had delayed growth kinetics but reached a final titer similar to that of rA2. Each virus was administered to the respiratory tracts of RSV-seronegative chimpanzees to assess replication, immunogenicity, and protective efficacy. The rA2ΔNS1 and rA2ΔM2-2 viruses were 2,200- to 55,000-fold restricted in replication in the upper and lower respiratory tracts but induced a level of RSV-neutralizing antibody in serum that was only slightly reduced compared to the level induced by wild-type RSV. The replication of wild-type RSV in immunized chimpanzees after challenge was reduced more than 10,000-fold at each site. Importantly, rA2ΔNS1 and rA2ΔM2-2 were 10-fold more restricted in replication in the upper respiratory tract than was thecpts248/404 virus, a vaccine candidate that retained mild reactogenicity in the upper respiratory tracts of 1-month-old infants. Thus, either rA2ΔNS1 or rA2ΔM2-2 might be appropriately attenuated for this age group, which is the major target population for an RSV vaccine. In addition, these results show that neither NS1 nor M2-2 is essential for RSV replication in vivo, although each is important for efficient replication.

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