scholarly journals Intracellular Targeting Signals Contribute to Localization of Coronavirus Spike Proteins near the Virus Assembly Site

2004 ◽  
Vol 78 (11) ◽  
pp. 5913-5922 ◽  
Author(s):  
Erik Lontok ◽  
Emily Corse ◽  
Carolyn E. Machamer
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Virus Assembly ◽  
Intracellular Localization ◽  
Cytoplasmic Tail ◽  
Viral Envelope ◽  
Reporter Protein ◽  
S Protein ◽  
Cytoplasmic Tails ◽  
S Proteins

ABSTRACT Coronavirus budding at the endoplasmic reticulum-Golgi intermediate compartment (ERGIC) requires accumulation of the viral envelope proteins at this point in the secretory pathway. Here we demonstrate that the spike (S) protein from the group 3 coronavirus infectious bronchitis virus (IBV) contains a canonical dilysine endoplasmic reticulum retrieval signal (-KKXX-COOH) in its cytoplasmic tail. This signal can retain a chimeric reporter protein in the ERGIC and when mutated allows transport of the full-length S protein as well as the chimera to the plasma membrane. Interestingly, the IBV S protein also contains a tyrosine-based endocytosis signal in its cytoplasmic tail, suggesting that any S protein that escapes the ERGIC will be rapidly endocytosed when it reaches the plasma membrane. We also identified a novel dibasic motif (-KXHXX-COOH) in the cytoplasmic tails of S proteins from group 1 coronaviruses and from the newly identified coronavirus implicated in severe acute respiratory syndrome. This dibasic motif also retained a reporter protein in the ERGIC, similar to the dilysine motif in IBV S. The cytoplasmic tails of S proteins from group 2 coronaviruses lack an intracellular localization signal. The inherent differences in S-protein trafficking could point to interesting variations in pathogenesis of coronaviruses, since increased levels of surface S protein could promote syncytium formation and direct cell-to-cell spread of the infection.

scholarly journals The Cytoplasmic Tail of the Severe Acute Respiratory Syndrome Coronavirus Spike Protein Contains a Novel Endoplasmic Reticulum Retrieval Signal That Binds COPI and Promotes Interaction with Membrane Protein

2006 ◽  
Vol 81 (5) ◽  
pp. 2418-2428 ◽  
Author(s):  
Corrin E. McBride ◽  
Jie Li ◽  
Carolyn E. Machamer
Keyword(s):  
Endoplasmic Reticulum ◽  
Severe Acute Respiratory Syndrome ◽  
Virus Assembly ◽  
Cytoplasmic Tail ◽  
Viral Envelope ◽  
S Protein ◽  
Golgi Region ◽  
Vitro Binding ◽  
Intermediate Compartment

ABSTRACT Like other coronaviruses, severe acute respiratory syndrome coronavirus (SARS CoV) assembles at and buds into the lumen of the endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC). Accumulation of the viral envelope proteins at this compartment is a prerequisite for virus assembly. Previously, we reported the identification of a dibasic motif (KxHxx) in the cytoplasmic tail of the SARS CoV spike (S) protein that was similar to a canonical dilysine ER retrieval signal. Here we demonstrate that this motif is a novel and functional ER retrieval signal which reduced the rate of traffic of the full-length S protein through the Golgi complex. The KxHxx motif also partially retained two different reporter proteins in the ERGIC region and reduced their rates of trafficking, although the motif was less potent than the canonical dilysine signal. The dibasic motif bound the coatomer complex I (COPI) in an in vitro binding assay, suggesting that ER retrieval may contribute to the accumulation of SARS CoV S protein near the virus assembly site for interaction with other viral structural proteins. In support of this, we found that the dibasic motif on the SARS S protein was required for its localization to the ERGIC/Golgi region when coexpressed with SARS membrane (M) protein. Thus, the cycling of SARS S through the ER-Golgi system may be required for its incorporation into assembling virions in the ERGIC.

scholarly journals Deletion of both the Tyrosine-Based Endocytosis Signal and the Endoplasmic Reticulum Retrieval Signal in the Cytoplasmic Tail of Spike Protein Attenuates Porcine Epidemic Diarrhea Virus in Pigs

2018 ◽  
Vol 93 (2) ◽  
Author(s):  
Yixuan Hou ◽  
Tea Meulia ◽  
Xiang Gao ◽  
Linda J. Saif ◽  
Qiuhong Wang
Keyword(s):  
Endoplasmic Reticulum ◽  
Vero Cell ◽  
Porcine Epidemic Diarrhea Virus ◽  
Cytoplasmic Tail ◽  
S Protein ◽  
Diarrhea Virus ◽  
Neonatal Piglets ◽  
Porcine Epidemic Diarrhea ◽  
Intracellular Sorting ◽  
S Proteins

ABSTRACTPorcine epidemic diarrhea virus (PEDV) causes high mortality in neonatal piglets. The PEDV spike (S) protein contains two intracellular sorting motifs, YxxΦ (tyrosine-based motif YEVF or YEAF) and KVHVQ at the cytoplasmic tail, yet their functions have not been fully elucidated. Some Vero cell-adapted and/or attenuated PEDV variants contain ablations in these two motifs. We hypothesized that these motifs contribute to viral pathogenicity. By transiently expressing PEDV S proteins with mutations in the motifs, we confirmed that the motif KVHVQ is involved in retention of the S proteins in the endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC). In addition, we showed that the YxxΦ motif triggers endocytosis of S proteins. These two motifs synergistically regulate the level of S expressed on the cell surface. To investigate their role in viral pathogenicity, we generated three recombinant PEDVs by introducing deletions or a mutation in the two motifs of the infectious clone of PEDV PC22A strain (icPC22A): (i) icΔ10aa (ΔYxxΦEKVHVQ), (ii) icΔ5aa (ΔKVHVQ), and (iii) icYA (Y1378A, to an inactivated motif, AEVF). Infection of Vero cells with icΔ10aa resulted in larger syncytia and more virions, with reduced numbers of S protein projections on the surface compared with icPC22A. Furthermore, we orally inoculated five groups of 5-day-old gnotobiotic piglets with the three mutants, icPC22A, or a mock treatment. Mutant icΔ10aa caused less severe diarrhea rate and significantly milder intestinal lesions than icPC22A, icΔ5aa, and icYA. These data suggest that the deletion of both motifs can reduce the virulence of PEDV in piglets.IMPORTANCEMany coronaviruses (CoVs) possess conserved motifs YxxΦ and/or KxHxx/KKxx in the cytoplasmic tail of the S protein. The KxHxx/KKxx motif has been identified as the ER retrieval signal, but the function of the YxxΦ motif in the intracellular sorting of CoV S proteins remains controversial. In this study, we showed that the YxxΦ of PEDV S protein is an endocytosis signal. Furthermore, using reverse genetics technology, we evaluated its role in PEDV pathogenicity in neonatal piglets. Our results explain one attenuation mechanism of Vero cell-adapted PEDV variants lacking functional YxxΦ and KVHVQ motifs. Knowledge from this study may aid in the design of efficacious live attenuated vaccines against PEDV, as well as other CoVs bearing the same motif in their S protein.

scholarly journals Role of Endocytosis and Low pH in Murine Hepatitis Virus Strain A59 Cell Entry

2007 ◽  
Vol 81 (19) ◽  
pp. 10758-10768 ◽  
Author(s):  
Patricia Eifart ◽  
Kai Ludwig ◽  
Christoph Böttcher ◽  
Cornelis A. M. de Haan ◽  
Peter J. M. Rottier ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Virus Strain ◽  
Hepatitis Virus ◽  
Low Ph ◽  
Viral Envelope ◽  
Murine Hepatitis Virus ◽  
S Protein ◽  
Fluorescence Confocal Microscopy ◽  
Murine Fibroblast ◽  
Intracellular Compartments

ABSTRACT Infection by the coronavirus mouse hepatitis virus strain A59 (MHV-A59) requires the release of the viral genome by fusion with the respective target membrane of the host cell. Fusion is mediated by the viral S protein. Here, the entry pathway of MHV-A59 into murine fibroblast cells was studied by independent approaches. Infection of cells assessed by plaque reduction assay was strongly inhibited by lysosomotropic compounds and substances that interfere with clathrin-dependent endocytosis, suggesting that MHV-A59 is taken up via endocytosis and delivered to acidic endosomal compartments. Infection was only slightly reduced in the presence of substances inhibiting proteases of endosomal compartments, precluding that the endocytic uptake is required to activate the fusion potential of the S protein by its cleavage. Fluorescence confocal microscopy of labeled MHV-A59 confirmed that virus is taken up via endocytosis. Bright labeling of intracellular compartments suggests their fusion with the viral envelope. No fusion with the plasma membrane was observed at neutral pH conditions. However, when virus was bound to cells and the pH was lowered to 5.0, we observed a strong labeling of the plasma membrane. Electron microscopy revealed low pH triggered conformational alterations of the S ectodomain. Very likely, these alterations are irreversible because low-pH treatment of viruses in the absence of target membranes caused an irreversible loss of the fusion activity. The results imply that endocytosis plays a major role in MHV-A59 infection and the acidic pH of the endosomal compartment triggers a conformational change of the S protein mediating fusion.

scholarly journals Roles for the Cytoplasmic Tails of the Fusion and Hemagglutinin-Neuraminidase Proteins in Budding of the Paramyxovirus Simian Virus 5

2002 ◽  
Vol 76 (18) ◽  
pp. 9284-9297 ◽  
Author(s):  
David L. Waning ◽  
Anthony P. Schmitt ◽  
George P. Leser ◽  
Robert A. Lamb
Keyword(s):  
Amino Acids ◽  
Tissue Culture ◽  
Double Mutant ◽  
Virus Assembly ◽  
Cytoplasmic Tail ◽  
Simian Virus ◽  
F Protein ◽  
Recombinant Viruses ◽  
Simian Virus 5 ◽  
Cytoplasmic Tails

ABSTRACT The efficient release of many enveloped viruses from cells involves the coalescence of viral components at sites of budding on the plasma membrane of infected cells. This coalescence is believed to require interactions between the cytoplasmic tails of surface glycoproteins and the matrix (M) protein. For the paramyxovirus simian virus 5 (SV5), the cytoplasmic tail of the hemagglutinin-neuraminidase (HN) protein has been shown previously to be important for normal virus budding. To investigate a role for the cytoplasmic tail of the fusion (F) protein in virus assembly and budding, we generated a series of F cytoplasmic tail-truncated recombinant viruses. Analysis of these viruses in tissue culture indicated that the cytoplasmic tail of the F protein was dispensable for normal virus replication and budding. To investigate further the requirements for assembly and budding of SV5, we generated two double-mutant recombinant viruses that lack 8 amino acids of the predicted 17-amino-acid HN protein cytoplasmic tail in combination with truncation of either 10 or 18 amino acids from the predicted 20-amino-acid F protein cytoplasmic tail. Both of the double mutant recombinant viruses displayed a replication defect in tissue culture and a budding defect, the extent of which was dependant on the length of the remaining F cytoplasmic tail. Taken together, this work and our earlier data on virus-like particle formation (A. P. Schmitt, G. P. Leser, D. L. Waning, and R. A. Lamb, J. Virol. 76:3953-3964, 2002) suggest a redundant role for the cytoplasmic tails of the HN and F proteins in virus assembly and budding.

scholarly journals The Cytoplasmic Tail of Glycoprotein M (gpUL100) Expresses Trafficking Signals Required for Human Cytomegalovirus Assembly and Replication

2007 ◽  
Vol 81 (19) ◽  
pp. 10316-10328 ◽  
Author(s):  
Magdalena Krzyzaniak ◽  
Michael Mach ◽  
William J. Britt
Keyword(s):  
Human Cytomegalovirus ◽  
Secretory Pathway ◽  
Virus Assembly ◽  
Intracellular Localization ◽  
Cytoplasmic Tail ◽  
Viral Gene ◽  
Gene Encoding ◽  
Particle Assembly ◽  
Reading Frame ◽  
Virion Envelope

ABSTRACT The virion envelope of human cytomegalovirus (HCMV) is complex and consists of an incompletely defined number of glycoproteins. The gM/gN protein complex is the most abundant protein component of the envelope. Studies have indicated that deletion of the viral gene encoding either gM or gN is a lethal mutation. Analysis of the amino acid sequence of gM disclosed a C-terminal acidic cluster of amino acids and a tyrosine-containing trafficking motif, both of which are well-described trafficking/sorting signals in the cellular secretory pathway. To investigate the roles of these signals in the trafficking of the gM/gN complex during virus assembly, we made a series of gM (UL100 open reading frame) mutants in the AD169 strain of HCMV. Mutant viruses that lacked the entire C-terminal cytoplasmic tail of gM were not viable, suggesting that the cytoplasmic tail of gM is essential for virus replication. In addition, the gM mutant protein lacking the cytoplasmic domain exhibited decreased protein stability. Mutant viruses with a deletion of the acidic cluster or alanine substitutions in tyrosine-based motifs were viable but exhibited a replication-impaired phenotype suggestive of a defect in virion assembly. Analysis of these mutant gMs using static immunofluorescence and fluorescence recovery after photobleaching demonstrated delayed kinetics of intracellular localization of the gM/gN protein to the virus assembly compartment compared to the wild-type protein. These data suggest an important role of the glycoprotein gM during virus assembly, particularly in the dynamics of gM trafficking during viral-particle assembly.

scholarly journals The effect of MEP pathway and other inhibitors on the intracellular localization of a plasma membrane-targeted, isoprenylable GFP reporter protein in tobacco BY-2 cells

F1000Research ◽  
2013 ◽  
Vol 2 ◽  
pp. 170 ◽  
Author(s):  
Michael Hartmann ◽  
Andrea Hemmerlin ◽  
Elisabet Gas-Pascual ◽  
Esther Gerber ◽  
Denis Tritsch ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Intracellular Localization ◽  
Test System ◽  
Mep Pathway ◽  
Reporter Protein ◽  
Visualization System ◽  
Gfp Reporter ◽  
Carboxy Terminal ◽  
The Impact

We have established an in vivo visualization system for the geranylgeranylation of proteins in a stably transformed tobacco BY-2 cell line, based on the expression of a dexamethasone-inducible GFP fused to the carboxy-terminal basic domain of the rice calmodulin CaM61, which naturally bears a CaaL geranylgeranylation motif (GFP-BD-CVIL). By using pathway-specific inhibitors it was demonstrated that inhibition of the methylerythritol phosphate (MEP) pathway with known inhibitors like oxoclomazone and fosmidomycin, as well as inhibition of the protein geranylgeranyltransferase type 1 (PGGT-1), shifted the localization of the GFP-BD-CVIL protein from the membrane to the nucleus. In contrast, the inhibition of the mevalonate (MVA) pathway with mevinolin did not affect the localization. During the present work, this test system has been used to examine the effect of newly designed inhibitors of the MEP pathway and inhibitors of sterol biosynthesis such as squalestatin, terbinafine and Ro48-8071. In addition, we also studied the impact of different post-prenylation inhibitors or those suspected to affect the transport of proteins to the plasma membrane on the localization of the geranylgeranylable fusion protein GFP-BD-CVIL.

scholarly journals Influenza A Virus M2 Protein Apical Targeting Is Required for Efficient Virus Replication

2018 ◽  
Vol 92 (22) ◽  
Author(s):  
Nicholas Wohlgemuth ◽  
Andrew P. Lane ◽  
Andrew Pekosz
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Influenza A Virus ◽  
Virus Replication ◽  
Influenza A ◽  
Infectious Virus ◽  
Virus Assembly ◽  
Apical Plasma Membrane ◽  
M2 Protein ◽  
Particle Release

ABSTRACTThe influenza A virus (IAV) M2 protein is a multifunctional protein with critical roles in virion entry, assembly, and budding. M2 is targeted to the apical plasma membrane of polarized epithelial cells, and the interaction of the viral proteins M2, M1, HA, and NA near glycolipid rafts in the apical plasma membrane is hypothesized to coordinate the assembly of infectious virus particles. To determine the role of M2 protein apical targeting in IAV replication, a panel of M2 proteins with basolateral plasma membrane (M2-Baso) or endoplasmic reticulum (M2-ER) targeting sequences was generated. MDCK II cells stably expressing M2-Baso, but not M2-ER, complemented the replication of M2-stop viruses. However, in primary human nasal epithelial cell (hNEC) cultures, viruses encoding M2-Baso and M2-ER replicated to negligible titers compared to those of wild-type virus. M2-Baso replication was negatively correlated with cell polarization. These results demonstrate that M2 apical targeting is essential for IAV replication: targeting M2 to the ER results in a strong, cell type-independent inhibition of virus replication, and targeting M2 to the basolateral membrane has greater effects in hNECs than in MDCK cells.IMPORTANCEInfluenza A virus assembly and particle release occur at the apical membrane of polarized epithelial cells. The integral membrane proteins encoded by the virus, HA, NA, and M2, are all targeted to the apical membrane and believed to recruit the other structural proteins to sites of virus assembly. By targeting M2 to the basolateral or endoplasmic reticulum membranes, influenza A virus replication was significantly reduced. Basolateral targeting of M2 reduced the infectious virus titers with minimal effects on virus particle release, while targeting to the endoplasmic reticulum resulted in reduced infectious and total virus particle release. Therefore, altering the expression and the intracellular targeting of M2 has major effects on virus replication.

scholarly journals The Cytoplasmic Tails of Uukuniemi Virus (Bunyaviridae) GN and GC Glycoproteins Are Important for Intracellular Targeting and the Budding of Virus-Like Particles

2007 ◽  
Vol 81 (20) ◽  
pp. 11381-11391 ◽  
Author(s):  
Anna K. Överby ◽  
Vsevolod L. Popov ◽  
Ralf F. Pettersson ◽  
Etienne P. A. Neve
Keyword(s):  
Intracellular Localization ◽  
Point Mutations ◽  
Cytoplasmic Tail ◽  
Single Amino Acid ◽  
Specific Information ◽  
Particle Generation ◽  
Intracellular Targeting ◽  
C Terminus ◽  
Single Amino Acid Residue ◽  
Cytoplasmic Tails

ABSTRACT Functional motifs within the cytoplasmic tails of the two glycoproteins GN and GC of Uukuniemi virus (UUK) (Bunyaviridae family) were identified with the help of our recently developed virus-like particle (VLP) system for UUK virus (A. K. Overby, V. Popov, E. P. Neve, and R. F. Pettersson, J. Virol. 80:10428-10435, 2006). We previously reported that information necessary for the packaging of ribonucleoproteins into VLPs is located within the GN cytoplasmic tail (A. K. Overby, R. F. Pettersson, and E. P. Neve, J. Virol. 81:3198-3205, 2007). The GN glycoprotein cytoplasmic tail specifically interacts with the ribonucleoproteins and is critical for genome packaging. In addition, two other regions in the GN cytoplasmic tail, encompassing residues 21 to 25 and 46 to 50, were shown to be important for particle generation and release. By the introduction of point mutations within these two regions, we demonstrate that leucines at positions 23 and 24 are crucial for the initiation of VLP budding, while leucine 46, glutamate 47, and leucine 50 are important for efficient exit from the endoplasmic reticulum and subsequent transport to the Golgi complex. We found that budding and particle generation are highly dependent on the intracellular localization of both glycoproteins. The short cytoplasmic tail of UUK GC contains a lysine at position −3 from the C terminus that is highly conserved among members of the Phlebovirus, Hantavirus, and Orthobunyavirus genera. Mutating this single amino acid residue in GC resulted in the mislocalization of not only GC but also GN to the plasma membrane, and VLP generation was compromised in cells expressing this mutant. Together, these results demonstrate that the cytoplasmic tails of both GN and GC contain specific information necessary for efficient virus particle generation.

scholarly journals African Swine Fever Virus Is Wrapped by the Endoplasmic Reticulum

1998 ◽  
Vol 72 (3) ◽  
pp. 2373-2387 ◽  
Author(s):  
Isabelle Rouiller ◽  
Sharon M. Brookes ◽  
Alex D. Hyatt ◽  
Miriam Windsor ◽  
Thomas Wileman
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Virus Assembly ◽  
African Swine Fever Virus ◽  
African Swine Fever ◽  
Viral Envelope ◽  
Immunogold Electron Microscopy ◽  
Icosahedral Symmetry ◽  
Structural Protein ◽  
Intracellular Membrane

ABSTRACT African swine fever (ASF) virus is a large DNA virus that shares the striking icosahedral symmetry of iridoviruses and the genomic organization of poxviruses. Both groups of viruses have a complex envelope structure. In this study, the mechanism of formation of the inner envelope of ASF virus was investigated. Examination of thin cryosections by electron microscopy showed two internal membranes in mature intracellular virions and all structural intermediates. These membranes were in continuity with intracellular membrane compartments, suggesting that the virus gained two membranes from intracellular membrane cisternae. Immunogold electron microscopy showed the viral structural protein p17 and resident membrane proteins of the endoplasmic reticulum (ER) within virus assembly sites, virus assembly intermediates, and mature virions. Resident ER proteins were also detected by Western blotting of isolated virions. The data suggested the ASF virus was wrapped by the ER. Analysis of the published sequence of ASF virus (R. J. Yanez et al., Virology 208:249–278, 1995) revealed a reading frame, XP124L, that encoded a protein predicted to translocate into the lumen of the ER. Pulse-chase immunoprecipitation and glycosylation analysis of pXP124L, the product of the XP124L gene, showed that pXP124L was retained in the ER lumen after synthesis. When analyzed by immunogold electron microscopy, pXP124L localized to virus assembly intermediates and fully assembled virions. Western blot analysis detected pXP124L in virions isolated from Percoll gradients. The packaging of pXP124L from the lumen of the ER into the virion is consistent with ASF virus being wrapped by ER cisternae: a mechanism which explains the presence of two membranes in the viral envelope.

scholarly journals A Linkage-specific Sialic Acid Labeling Strategy Reveals Different Site-specific Glycosylation Patterns in SARS-CoV-2 Spike Protein Produced in CHO and HEK Cell Substrates

2021 ◽  
Vol 9 ◽  
Author(s):  
Qiong Wang ◽  
Yan Wang ◽  
Shuang Yang ◽  
Changyi Lin ◽  
Lateef Aliyu ◽  
...  
Keyword(s):  
Immune System ◽  
Sialic Acid ◽  
Viral Envelope ◽  
Site Specific ◽  
S Protein ◽  
Hek Cells ◽  
High Mannose ◽  
The Impact ◽  
S Proteins ◽  
Spike Proteins

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus utilizes the extensively glycosylated spike (S) protein protruding from the viral envelope to bind to angiotensin-converting enzyme-related carboxypeptidase (ACE2) as its primary receptor to mediate host-cell entry. Currently, the main recombinant S protein production hosts are Chinese hamster ovary (CHO) and human embryonic kidney (HEK) cells. In this study, a recombinant S protein truncated at the transmembrane domain and engineered to express a C-terminal trimerization motif was transiently produced in CHO and HEK cell suspensions. To further evaluate the sialic acid linkages presenting on S protein, a two-step amidation process, employing dimethylamine and ammonium hydroxide reactions in a solid support system, was developed to differentially modify the sialic acid linkages on the glycans and glycopeptides from the S protein. The process also adds a charge to Asp and Glu which aids in ionization. We used MALDI-TOF and LC-MS/MS with electron-transfer/higher-energy collision dissociation (EThcD) fragmentation to determine global and site-specific N-linked glycosylation patterns. We identified 21 and 19 out of the 22 predicted N-glycosites of the SARS-CoV-2 S proteins produced in CHO and HEK, respectively. It was found that the N-glycosite at 1,158 position (N1158) and at 122, 282 and 1,158 positions (N122, N282 and N1158) were absent on S from CHO and HEK cells, respectively. The structural mapping of glycans of recombinant human S proteins reveals that CHO-Spike exhibits more complex and higher sialylation (α2,3-linked) content while HEK-Spike exhibits more high-mannose and a small amount of α2,3- and α2,6-linked sialic acids. The N74 site represents the most abundant glycosite on both spike proteins. The relatively higher amount of high-mannose abundant sites (N17, N234, N343, N616, N709, N717, N801, and N1134) on HEK-Spike suggests that glycan-shielding may differ among the two constructs. HEK-Spike can also provide different host immune system interaction profiles based on known immune system active lectins. Collectively, these data underscore the importance of characterizing the site-specific glycosylation of recombinant human spike proteins from HEK and CHO cells in order to better understand the impact of the production host on this complex and important protein used in research, diagnostics and vaccines.

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