Generation and characterization of variants of NWS/G70C influenza virus after in vitro passage in 4-amino-Neu5Ac2en and 4-guanidino-Neu5Ac2en.

The compounds 4-amino-Neu5Ac2en (5-acetylamino-2,6-anhydro-4-amino-3,4,5- trideoxy-D-glycerol-D-galacto-non-2-enoic acid) and 4-guanidino-Neu5Ac2en (5-acetylamino-2,6-anhydro-4-guanidino-3,4,5- trideoxy-D-glycerol-D-galacto-non-2-enoic acid), which selectively inhibit the influenza virus neuraminidase, have been tested in vitro for their ability to generate drug-resistant variants. NWS/G70C virus (H1N9) was cultured in each drug by limiting-dilution passaging. After five or six passages in either compound, there emerged viruses which had a reduced sensitivity to the inhibitors in cell culture. Variant viruses were up to 1,000-fold less sensitive in plaque assays, liquid culture, and a hemagglutination-elution assay. In addition, cross-resistance to both compounds was seen in all three assays. Some isolates demonstrated drug dependence with an increase in both size and number of plaques in a plaque assay and an increase in virus yield in liquid culture in the presence of inhibitors. No significant difference in neuraminidase enzyme activity was detected in vitro, and no sequence changes in the conserved sites of the neuraminidase were found. However, changes in conserved amino acids in the hemagglutinin were detected. These amino acids were associated with either the hemagglutinin receptor binding site, Thr-155, or the left edge of the receptor binding pocket, Val-223 and Arg-229. Hence, mutations at these sites could be expected to affect the affinity or specificity of the hemagglutinin binding. Compensating mutations resulting in a weakly binding hemagglutinin thus seem to be circumventing the inhibition of the neuraminidase by allowing the virus to be released from cells with less dependence on the neuraminidase.

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N-Linked Glycans and K147 Residue on Hemagglutinin Synergize To Elicit Broadly Reactive H1N1 Influenza Virus Antibodies

Journal of Virology ◽

10.1128/jvi.01432-19 ◽

2019 ◽

Vol 94 (6) ◽

Cited By ~ 5

Author(s):

Ying Huang ◽

Simon O. Owino ◽

Corey J. Crevar ◽

Donald M. Carter ◽

Ted M. Ross

Keyword(s):

Amino Acids ◽

Influenza Virus ◽

Binding Site ◽

Receptor Binding ◽

Hemagglutination Inhibition ◽

Vaccine Development ◽

H1n1 Influenza ◽

Influenza Viruses ◽

Wild Type ◽

Receptor Binding Site

ABSTRACT Vaccination is the most effective way to prevent influenza virus infections. However, the diversity of antigenically distinct isolates is a challenge for vaccine development. In order to overcome the antigenic variability and improve the protective efficacy of influenza vaccines, our research group has pioneered the development of computationally optimized broadly reactive antigens (COBRA) for hemagglutinin (HA). Two candidate COBRA HA vaccines, P1 and X6, elicited antibodies with differential patterns of hemagglutination inhibition (HAI) activity against a panel of H1N1 influenza viruses. In order to better understand how these HA antigens elicit broadly reactive immune responses, epitopes in the Cb, Sa, or Sb antigenic sites of seasonal-like and pandemic-like wild-type or COBRA HA antigens were exchanged with homologous regions in the COBRA HA proteins to determine which regions and residues were responsible for the elicited antibody profile. Mice were vaccinated with virus-like particles (VLPs) expressing one of the 12 modified HA antigens (designated V1 to V12), COBRA HA antigens, or wild-type HA antigens. The elicited antisera was assessed for hemagglutination inhibition activity against a panel of historical seasonal-like and pandemic-like H1N1 influenza viruses. Primarily, the pattern of glycosylation sites and residues in the Sa antigenic region, around the receptor binding site (RBS), served as signatures for the elicitation of broadly reactive antibodies by these HA immunogens. Mice were vaccinated with VLPs expressing HA antigens that lacked a glycosylation site at residue 144 and a deleted lysine at position 147 residue were more effective at protecting against morbidity and mortality following infection with pandemic-like and seasonal-like H1N1 influenza viruses. IMPORTANCE There is a great need to develop broadly reactive or universal vaccines against influenza viruses. Advanced, next-generation hemagglutinin (HA) head-based vaccines that elicit protective antibodies against H1N1 influenza viruses have been developed. This study focused on understanding the specific amino acids around the receptor binding site (RBS) that were important in elicitation of these broadly reactive antibodies. Specific glycan sites and amino acids located at the tip of the HA molecule enhanced the elicitation of these broadly reactive antibodies. A better understanding of the HA structures around the RBS will lead to more effective HA immunogens.

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Characterization of a new influenza virus type D

Medycyna Weterynaryjna ◽

10.21521/mw.5565 ◽

2016 ◽

Vol 72 (9) ◽

pp. 531-535

Author(s):

Iwona Markowska-Daniel ◽

Marcin Mickiewicz ◽

Lucjan Witkowski ◽

Jerzy Kita

Keyword(s):

Influenza Virus ◽

Receptor Binding ◽

Influenza A ◽

Evolutionary Relationship ◽

Influenza Viruses ◽

Virus Protein ◽

Cell Tropism ◽

Receptor Binding Site ◽

Antigenic Properties

Influenza is caused by viruses belonging to the Orthomyxoviridae family. Currently three types of influenza virus are known: A (Influenza A virus, IAV), B (IBV) and C (ICV). Despite the fact that all these viruses are derived from a common ancestor they differ from each other by the number of segments, the size and sequence of RNA segments, antigenicity, pathogenicity and the spectrum of natural reservoirs. In 2011, a new influenza virus was isolated in the USA from pigs manifesting influenza-like symptoms. The virus was the most closely related to ICV. It was able to replicate in vitro in different cell cultures and displayed much broader cell tropism than human ICV. Moreover, in contrast to ICV, it was able to replicate at 370C. Electron microscopic studies demonstrated features characteristic of Orthomyxoviruses. Despite morphological and organizational similarities, the biological properties of the new virus, including biochemical activity, differ from that of other influenza viruses. Enzymatic assays revealed that the new virus had negligible neuraminidase but detectable O-acetyloesterase activity. Further studies evidenced that the new virus varied from ICV in receptor binding, despite its sharing a conserved array of functional domains in the viral RNA genome replication and viral entry machinery. Analysis conducted with the use of the model of crystal structure of the hemagglutinin-esterase fusion protein (HE) of the new virus and its receptor demonstrated that this protein was multifunctional. It catalyzes cellular receptor binding, receptor cleavage, as well as membrane fusion. Moreover, divergent receptor-binding sites than HE of ICV have been discovered in the new virus. These amino acid differences may alter the binding specificity and affinity of the HE protein to the receptor that in turn result in the observed differences in cellular tropism between the two viruses. It also possesses an open channel between the 230-helix and 270-loop in the receptor-binding site, which is a unique feature of this virus. This might explain why the new virus has a broad cell tropism. It is possible that the sequence variation in the fusion domain may influence the replication of this virus at a higher temperature when compared to ICV. Next-generation sequencing demonstrated that the genome of the new virus, similarly to ICV, had seven single-stranded negative-sense RNA segments coding 9 viral proteins. Deep RNA sequencing found a M1 protein expression strategy different from that of ICV. Studies aimed at evaluating of the evolutionary relationship of both viruses revealed that the new virus and ICV shared an approximately 69-72% mean pairwise identity in the PB1 gene, which is reported to be the most conserved influenza virus protein. Additionally, differences were detected at 5’ and 3’ends of noncoding regions, which are also highly conserved. They both may be responsible for the lack of in vitro reassortment between ICV of human origin and the new virus. In the study characterizing antigenic properties of the new virus, no cross-reactivity was observed using HI and AGID tests. This indicates the major differences in conserved proteins M1 and NP between both viruses. Summing up, despite the fact that new virus is the most closely related to human ICV, the number of important antigenic and genetic distinctions among them is the basis for suggesting that the International Committee of Virus Taxonomy classify it as a separate genus - D. There is no doubt that the discovery of a new influenza virus genus will have a great impact on influenza research and ecology.

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Random Transposon-Mediated Mutagenesis of the Essential Large Tegument Protein pUL36 of Pseudorabies Virus

Journal of Virology ◽

10.1128/jvi.00953-10 ◽

2010 ◽

Vol 84 (16) ◽

pp. 8153-8162 ◽

Cited By ~ 15

Author(s):

Britta S. Möhl ◽

Sindy Böttcher ◽

Harald Granzow ◽

Walter Fuchs ◽

Barbara G. Klupp ◽

...

Keyword(s):

Amino Acids ◽

Pseudorabies Virus ◽

Plaque Assay ◽

Tegument Protein ◽

Nuclear Pore ◽

Viral Spread ◽

One Step ◽

Step Growth ◽

Insertion Mutants

ABSTRACT Homologs of the pseudorabies virus (PrV) essential large tegument protein pUL36 are conserved throughout the Herpesviridae. pUL36 functions during transport of the nucleocapsid to and docking at the nuclear pore as well as during virion formation after nuclear egress in the cytoplasm. Deletion analyses revealed several nonessential regions within the 3,084-amino-acid PrV pUL36 (S. Böttcher, B. G. Klupp, H. Granzow, W. Fuchs, K. Michael, and T. C. Mettenleiter, J. Virol. 80:9910-9915, 2006; S. Böttcher, H. Granzow, C. Maresch, B. Möhl, B. G. Klupp, and T. C. Mettenleiter, J. Virol. 81:13403-13411, 2007), while the C-terminal 62 amino acids are essential for virus replication (K. Coller, J. Lee, A. Ueda, and G. Smith, J. Virol. 81:11790-11797, 2007). To identify additional functional domains, we performed random mutagenesis of PrV pUL36 by transposon-mediated insertion of a 15-bp linker. By this approach, 26 pUL36 insertion mutants were selected and tested in transient transfection assays for their ability to complement one-step growth and/or viral spread of a PrV UL36 null mutant. Ten insertion mutants in the N-terminal half and 10 in the C terminus complemented both, whereas six insertion mutants clustering in the center of the protein did not complement in either assay. Interestingly, several insertions within conserved parts yielded positive complementation, including those located within the essential C-terminal 62 amino acids. For 15 mutants that mediated productive replication, stable virus recombinants were isolated and further characterized by plaque assay, in vitro growth analysis, and electron microscopy. Except for three mutant viruses, most insertion mutants replicated like wild-type PrV. Two insertion mutants, at amino acids (aa) 597 and 689, were impaired in one-step growth and viral spread and exhibited a defect in virion maturation in the cytoplasm. In contrast, one functional insertion (aa 1800) in a region which otherwise yielded only nonfunctional insertion mutants was impaired in viral spread but not in one-step growth without a distinctive ultrastructural phenotype. In summary, these studies extend and refine previous analyses of PrV pUL36 and demonstrate the different sensitivities of different regions of the protein to functional loss by insertion.

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Trans-tegumental absorption of L-alanine and L-leucine by a monogenean, Diclidophora merlangi

Parasitology ◽

10.1017/s0031182000047363 ◽

1978 ◽

Vol 76 (1) ◽

pp. 29-37 ◽

Cited By ~ 21

Author(s):

D. W. Halton

Keyword(s):

Amino Acids ◽

Molecular Weight ◽

Amino Acid ◽

Sea Water ◽

Low Molecular Weight ◽

Acid Uptake ◽

Neutral Amino Acids ◽

Freeze Dried ◽

Significant Difference

SummaryAn in vitro investigation has been made of the relative roles of the gut and tegument in the absorption of the neutral amino acids L-alanine and L-leucine by a marine fish-gill parasite, Diclidophora merlangi. The use of ligatures to preclude oral ingestion of trace-labelled medium has proved inadequate, invariably damaging the tegument, as revealed by stereoscan electron microscopy, and resulting in artifactual levels of absorption. Three alternative procedures have given consistently reliable data on the route of entry of low molecular weight substrates. (1) Ultrastructural examination of worms previously incubated in electron-dense cationic tracers has shown that, in vitro, there is no oral intake of sea water. (2) The suspending of worms in trace-labelled medium with the mouth out of the medium and comparing amino acid uptake with that of worms totally immersed in medium has revealed no statistically significant difference in the absorption levels. (3) Application of section (freeze-dried) auto-radiography to detect diffusible isotope has demonstrated directly transtegumental absorption of a neutral amino acid. It is concluded from these experiments that Diclidophora has a tegumental transport system for absorbing certain neutral amino acids, and whilst, clearly, the worm is sanguinivorous and digests blood in a well-developed gut, it may also be capable of supplementing this diet with low molecular weight organic nutrient absorbed directly from sea water via the tegument.

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Development and population dynamics of Steinernema yirgalemense (Rhabditida: Steinernematidae) and growth characteristics of its associated Xenorhabdusindica symbiont in liquid culture

Journal of Helminthology ◽

10.1017/s0022149x15000450 ◽

2015 ◽

Vol 90 (3) ◽

pp. 364-371 ◽

Cited By ~ 12

Author(s):

T. Ferreira ◽

M.F. Addison ◽

A.P. Malan

Keyword(s):

Population Density ◽

Liquid Culture ◽

Commercial Application ◽

Adult Density ◽

Developmental Phase ◽

Male Density ◽

Wide Range ◽

Significant Difference

AbstractEntomopathogenic nematodes have become a valuable addition to the range of biological control agents available for insect control. An endemic nematode, Steinernemayirgalemense, has been found to be effective against a wide range of key insect pests. The next step would be the mass production this nematode for commercial application. This requires the establishment of monoxenic cultures of both the nematode and the symbiotic bacterium Xenorhabdus indica. First-stage juveniles of S. yirgalemense were obtained from eggs, while X. indica was isolated from nematode-infected wax moth larvae. The population density of the various life stages of S. yirgalemense during the developmental phase in liquid culture was determined. The recovery of infective juveniles (IJs) to the third-stage feeding juveniles, was 67 ± 10%, reaching a maximum population density of 75,000 IJs ml− 1 on day 13 after inoculation. Adult density increased after 8 days, with the maximum female density being 4600 ml− 1 on day 15, whereas the maximum male density was 4300 ml− 1 on day 12. Growth curves for X. indica showed that the exponential phase was reached 15 h after inoculation to the liquid medium. The stationary phase was reached after 42 h, with an average of 51 × 107 colony-forming units ml− 1. Virulence tests showed a significant difference in insect mortality between in vitro- and in vivo-produced nematodes. The success obtained with the production of S. yirgalemense in liquid culture can serve as the first step in the optimizing and upscaling of the commercial production of nematodes in fermenters.

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Mutations in a Conserved Residue in the Influenza Virus Neuraminidase Active Site Decreases Sensitivity to Neu5Ac2en-Derived Inhibitors

Journal of Virology ◽

10.1128/jvi.72.3.2456-2462.1998 ◽

1998 ◽

Vol 72 (3) ◽

pp. 2456-2462 ◽

Cited By ~ 124

Author(s):

Jennifer L. McKimm-Breschkin ◽

Anjali Sahasrabudhe ◽

Tony J. Blick ◽

Mandy McDonald ◽

Peter M. Colman ◽

...

Keyword(s):

Influenza Virus ◽

Active Site ◽

Liquid Culture ◽

Specific Inhibitor ◽

Side Chain ◽

Enzyme Assays ◽

Hydrophobic Group ◽

Influenza Virus Neuraminidase ◽

Conserved Residue

ABSTRACT The influenza virus neuraminidase (NA)-specific inhibitor zanamivir (4-guanidino-Neu5Ac2en) is effective in humans when administered topically within the respiratory tract. The search for compounds with altered pharmacological properties has led to the identification of a novel series of influenza virus NA inhibitors in which the triol group of zanamivir has been replaced by a hydrophobic group linked by a carboxamide at the 6 position (6-carboxamide). NWS/G70C variants generated in vitro, with decreased sensitivity to 6-carboxamide, contained hemagglutinin (HA) and/or NA mutations. HA mutants bound with a decreased efficiency to the cellular receptor and were cross-resistant to all the NA inhibitors tested. The NA mutation, an Arg-to-Lys mutation, was in a previously conserved site, Arg292, which forms part of a triarginyl cluster in the catalytic site. In enzyme assays, the NA was equally resistant to zanamivir and 4-amino-Neu5Ac2en but showed greater resistance to 6-carboxamide and was most resistant to a new carbocyclic NA inhibitor, GS4071, which also has a hydrophobic side chain at the 6 position. Consistent with enzyme assays, the lowest resistance in cell culture was seen to zanamivir, more resistance was seen to 6-carboxamide, and the greatest resistance was seen to GS4071. Substrate binding and enzyme activity were also decreased in the mutant, and consequently, virus replication in both plaque assays and liquid culture was compromised. Altered binding of the hydrophobic side chain at the 6 position or the triol group could account for the decreased binding of both the NA inhibitors and substrate.

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Enhancement of SARS-CoV-2 Receptor Binding Domain -CR3022 Human Antibody Binding Affinity via in Silico Engineering Approach

10.21203/rs.3.rs-56411/v1 ◽

2020 ◽

Author(s):

Fateme Sefid ◽

Zahra Payandeh ◽

Ghasem Azamirad ◽

Behzad Mansoori ◽

Behzad Baradaran ◽

...

Keyword(s):

Amino Acids ◽

Binding Affinity ◽

Receptor Binding ◽

Neutralizing Antibodies ◽

Affinity Maturation ◽

Binding Domain ◽

Human Antibody ◽

Receptor Binding Domain ◽

Receptor Binding Site ◽

Specificity And Sensitivity

Abstract Background: The nCoV-2019 is a cause of COVID-19 disease. The surface spike glycoprotein (S), which is necessary for virus entry through the intervention of the host receptor and it mediates virus-host membrane fusion, is the primary coronavirus antigen (Ag). The angiotensin-converting enzyme 2 (ACE2) is reported to be the effective human receptor for SARS-CoVs 2. ACE2 receptor can be prevented by neutralizing antibodies (nAbs) such as CR3022 targeting the virus receptor-binding site. Considering the importance of computational docking, and affinity maturation we aimed to find the important amino acids of the CR3022 antibody (Ab). These amino acids were then replaced by other amino acids to improve Ab-binding affinity to a receptor-binding domain (RBD) of the 2019-nCoV spike protein. Finally, we measured the binding affinity of Ab variants to the Ag. Result: Our findings disclosed that several variant mutations could successfully improve the characteristics of the Ab binding compared to the normal antibodies. Conclusion: The modified antibodies may be possible candidates for stronger affinity binding to Ags which in turn can affect the specificity and sensitivity of antibodies.

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Chloroquine Inhibits Dengue Virus Type 2 Replication in Vero Cells but Not in C6/36 Cells

The Scientific World JOURNAL ◽

10.1155/2013/282734 ◽

2013 ◽

Vol 2013 ◽

pp. 1-5 ◽

Cited By ~ 36

Author(s):

Kleber Juvenal Silva Farias ◽

Paula Renata Lima Machado ◽

Benedito Antônio Lopes da Fonseca

Keyword(s):

Dengue Virus ◽

Virus Type ◽

Mammalian Cells ◽

Plaque Assay ◽

Antiviral Drug ◽

Vero Cells ◽

Significant Difference ◽

Dengue Virus Type 2

Dengue viruses are the most important arthropod-borne viruses in terms of morbidity and mortality in the world. Since there is no dengue vaccine available for human use, we have set out to investigate the use of chloroquine as an antiviral drug against dengue. Chloroquine, an amine acidotropic drug known to affect intracellular exocytic pathways by increasing endosomal pH, was used in the in vitro treatment of Vero and C6/36 cells infected with dengue virus type 2 (DENV-2). Real-time RT-PCR and plaque assays were used to quantify the DENV-2 load in infected Vero and C6/36 cells after chloroquine treatment. Our results showed that a dose of 50 μg/ml of chloroquine was not toxic to the cells and induced a statistically significant inhibition of virus production in infected Vero cells when compared to untreated cells. In C6/36 cells, chloroquine does not induce a statistically significant difference in viral replication when compared to untreated cells, showing that this virus uses an unlikely pathway of penetration in these cells, and results were also confirmed by the plaque assay (PFU). These data suggest that the inhibition of virus infection induced by chloroquine is due to interference with acidic vesicles in mammalian cells.

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Loss of the N-Linked Glycan at Residue 173 of Human Parainfluenza Virus Type 1 Hemagglutinin-Neuraminidase Exposes a Second Receptor-Binding Site

Journal of Virology ◽

10.1128/jvi.00474-08 ◽

2008 ◽

Vol 82 (17) ◽

pp. 8400-8410 ◽

Cited By ~ 15

Author(s):

Irina V. Alymova ◽

Garry Taylor ◽

Vasiliy P. Mishin ◽

Makiko Watanabe ◽

K. Gopal Murti ◽

...

Keyword(s):

Binding Site ◽

Receptor Binding ◽

Sendai Virus ◽

Receptor Binding Site ◽

Parainfluenza Viruses ◽

Mutant Sequence ◽

Lethal Infection ◽

Human Parainfluenza Virus

ABSTRACT BCX 2798 (4-azido-5-isobutyrylamino-2,3-didehydro-2,3,4,5-tetradeoxy-d-glycero-d-galacto-2-nonulopyranosic acid) effectively inhibited the activities of the hemagglutinin-neuraminidase (HN) of human parainfluenza viruses (hPIV) in vitro and protected mice from lethal infection with a recombinant Sendai virus whose HN was replaced with that of hPIV-1 (rSeV[hPIV-1HN]) (I. V. Alymova, G. Taylor, T. Takimoto, T. H. Lin., P. Chand, Y. S. Babu, C. Li, X. Xiong, and A. Portner, Antimicrob. Agents Chemother. 48:1495-1502, 2004). The ability of BCX 2798 to select drug-resistant variants in vivo was examined. A variant with an Asn-to-Ser mutation at residue 173 (N173S) in HN was recovered from mice after a second passage of rSeV(hPIV-1HN) in the presence of BCX 2798 (10 mg/kg of body weight daily). The N173S mutant remained sensitive to BCX 2798 in neuraminidase inhibition assays but was more than 10,000-fold less sensitive to the compound in hemagglutination inhibition tests than rSeV(hPIV-1HN). Its susceptibility to BCX 2798 in plaque reduction assays was reduced fivefold and did not differ from that of rSeV(hPIV-1HN) in mice. The N173S mutant failed to be efficiently eluted from erythrocytes and released from cells. It demonstrated reduced growth in cell culture and superior growth in mice. The results for gel electrophoresis analysis were consistent with the loss of the N-linked glycan at residue 173 in the mutant. Sequence and structural comparisons revealed that residue 173 on hPIV-1 HN is located close to the region of the second receptor-binding site identified in Newcastle disease virus HN. Our study suggests that the N-linked glycan at residue 173 masks a second receptor-binding site on hPIV-1 HN.

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