scholarly journals Optimization of the Codon Pair Usage of Human Respiratory Syncytial Virus Paradoxically Resulted in Reduced Viral Replication In Vivo and Reduced Immunogenicity

2019 ◽  
Vol 94 (2) ◽  
Author(s):  
Cyril Le Nouën ◽  
Cindy L. Luongo ◽  
Lijuan Yang ◽  
Steffen Mueller ◽  
Eckard Wimmer ◽  
...  
Keyword(s):  
Respiratory Syncytial Virus ◽  
Viral Replication ◽  
Virus Replication ◽  
Neutralizing Antibodies ◽  
Rna Virus ◽  
Humoral Immune ◽  
Codon Pair ◽  
Syncytial Virus ◽  
Codon Pairs

ABSTRACT We subjected various open reading frames (ORFs) in the genome of respiratory syncytial virus (RSV) to codon pair optimization (CPO) by increasing the content of codon pairs that are overrepresented in the human genome without changing overall codon usage and amino acid sequences. CPO has the potential to increase the expression of the encoded protein(s). Four viruses were made: Max A (with CPO of NS1, NS2, N, P, M, and SH ORFs), Max B (with CPO of G and F), Max L (with CPO of L), and Max FLC (with CPO of all ORFs except M2-1 and M2-2). Because of the possibility of increased viral replication, each CPO virus was attenuated by the inclusion of a codon deletion mutation (Δ1313) and a missense mutation (I1314L) in the L polymerase. CPO had no effect on multicycle virus replication in vitro, temperature sensitivity, or specific infectivity. Max A and L, which in common had CPO of one or more ORFs of proteins of the polymerase complex, exhibited global increases in viral protein synthesis. Max B alone exhibited decreased protein synthesis, and it alone had reduced single-cycle virus replication in vitro. All CPO RSVs exhibited marginal reductions in replication in mice and hamsters. Surprisingly, the CPO RSVs induced lower levels of serum RSV-neutralizing antibodies in hamsters. This reduced immunogenicity might reflect reduced viral replication and possibly also the decrease in CpG and UpA dinucleotides as immune stimulators. Overall, our study describes paradoxical effects of CPO of an RNA virus on viral replication and the adaptive humoral immune response. IMPORTANCE Using computer algorithms and large-scale DNA synthesis, one or more ORFs of a microbial pathogen can be recoded by different strategies that involve the introduction of up to thousands of nucleotide changes without affecting amino acid coding. This approach has been used mostly to generate deoptimized viruses used as vaccine candidates. However, the effects of the converse approach of generating optimized viruses are still largely unknown. Here, various ORFs in the genome of respiratory syncytial virus (RSV) were codon pair optimized (CPO) by increasing the content of codon pairs that are overrepresented in the human genome. CPO did not affect RSV replication in multicycle replication experiments in vitro. However, replication was marginally reduced in two rodents models. In hamsters, CPO RSVs induced lower levels of serum RSV-neutralizing antibodies. Thus, CPO of an RNA virus for a mammalian host has paradoxical effects on virus replication and the adaptive humoral immune response.

scholarly journals The Major Phosphorylation Sites of the Respiratory Syncytial Virus Phosphoprotein Are Dispensable for Virus Replication In Vitro

2002 ◽  
Vol 76 (21) ◽  
pp. 10776-10784 ◽  
Author(s):  
Bin Lu ◽  
Chien-Hui Ma ◽  
Robert Brazas ◽  
Hong Jin
Keyword(s):  
Respiratory Syncytial Virus ◽  
Virus Replication ◽  
Vero Cells ◽  
Phosphorylation Sites ◽  
N Protein ◽  
P Protein ◽  
Infected Cells ◽  
Syncytial Virus

ABSTRACT The phosphoprotein (P protein) of respiratory syncytial virus (RSV) is a key component of the viral RNA-dependent RNA polymerase complex. The protein is constitutively phosphorylated at the two clusters of serine residues (116, 117, and 119 [116/117/119] and 232 and 237 [232/237]). To examine the role of phosphorylation of the RSV P protein in virus replication, these five serine residues were altered to eliminate their phosphorylation potential, and the mutant proteins were analyzed for their functions with a minigenome assay. The reporter gene expression was reduced by 20% when all five phosphorylation sites were eliminated. Mutants with knockout mutations at two phosphorylation sites (S232A/S237A [PP2]) and at five phosphorylation sites (S116L/S117R/S119L/S232A/S237A [PP5]) were introduced into the infectious RSV A2 strain. Immunoprecipitation of 33Pi-labeled infected cells showed that P protein phosphorylation was reduced by 80% for rA2-PP2 and 95% for rA2-PP5. The interaction between the nucleocapsid (N) protein and P protein was reduced in rA2-PP2- and rA2-PP5-infected cells by 30 and 60%, respectively. Although the two recombinant viruses replicated well in Vero cells, rA2-PP2 and, to a greater extent, rA2-PP5, replicated poorly in HEp-2 cells. Virus budding from the infected HEp-2 cells was affected by dephosphorylation of P protein, because the majority of rA2-PP5 remained cell associated. In addition, rA2-PP5 was also more attenuated than rA2-PP2 in replication in the respiratory tracts of mice and cotton rats. Thus, our data suggest that although the major phosphorylation sites of RSV P protein are dispensable for virus replication in vitro, phosphorylation of P protein is required for efficient virus replication in vitro and in vivo.

scholarly journals In Vitro Primer-Based RNA Elongation and Promoter Fine Mapping of the Respiratory Syncytial Virus

2020 ◽  
Vol 95 (1) ◽  
Author(s):  
Dongdong Cao ◽  
Yunrong Gao ◽  
Claire Roesler ◽  
Samantha Rice ◽  
Paul D'Cunha ◽  
...  
Keyword(s):  
Respiratory Syncytial Virus ◽  
Fine Mapping ◽  
Rna Synthesis ◽  
De Novo ◽  
Rna Viruses ◽  
Rna Virus ◽  
Promoter Sequence ◽  
Mechanistic Understanding ◽  
Syncytial Virus

ABSTRACT Respiratory syncytial virus (RSV) is a nonsegmented negative-sense (NNS) RNA virus and shares a similar RNA synthesis strategy with other members of NNS RNA viruses, such as measles, rabies virus, and Ebola virus. RSV RNA synthesis is catalyzed by a multifunctional RNA-dependent RNA polymerase (RdRP), which is composed of a large (L) protein that catalyzes three distinct enzymatic functions and an essential coenzyme phosphoprotein (P). Here, we successfully prepared highly pure, full-length, wild-type and mutant RSV polymerase (L-P) complexes. We demonstrated that the RSV polymerase could carry out both de novo and primer-based RNA synthesis. We defined the minimal length of the RNA template for in vitro de novo RNA synthesis using the purified RSV polymerase as 8 nucleotides (nt), shorter than previously reported. We showed that the RSV polymerase catalyzed primer-dependent RNA elongation with different lengths of primers on both short (10-nt) and long (25-nt) RNA templates. We compared the sequence specificity of different viral promoters and identified positions 3, 5, and 8 of the promoter sequence as essential to the in vitro RSV polymerase activity, consistent with the results previously mapped with the in vivo minigenome assay. Overall, these findings agree well with those of previous biochemical studies and extend our understanding of the promoter sequence and the mechanism of RSV RNA synthesis. IMPORTANCE As a major human pathogen, RSV affects 3.4 million children worldwide annually. However, no effective antivirals or vaccines are available. An in-depth mechanistic understanding of the RSV RNA synthesis machinery remains a high priority among the NNS RNA viruses. There is a strong public health need for research on this virus, due to major fundamental gaps in our understanding of NNS RNA virus replication. As the key enzyme executing transcription and replication of the virus, the RSV RdRP is a logical target for novel antiviral drugs. Therefore, exploring the primer-dependent RNA elongation extends our mechanistic understanding of the RSV RNA synthesis. Further fine mapping of the promoter sequence paves the way to better understand the function and structure of the RSV polymerase.

scholarly journals The Central Conserved Cystine Noose of the Attachment G Protein of Human Respiratory Syncytial Virus Is Not Required for Efficient Viral Infection In Vitro or In Vivo

2002 ◽  
Vol 76 (12) ◽  
pp. 6164-6171 ◽  
Author(s):  
Michael N. Teng ◽  
Peter L. Collins
Keyword(s):  
Respiratory Syncytial Virus ◽  
Amino Acid ◽  
Respiratory Tract ◽  
G Protein ◽  
Virus Replication ◽  
Central Region ◽  
Syncytial Virus ◽  
Amino Acid Segment

ABSTRACT The G glycoprotein of human respiratory syncytial virus (RSV) was identified previously as the viral attachment protein. Although we and others recently showed that G is not essential for replication in vitro, it does affect the efficiency of replication in a cell type-dependent fashion and is required for efficient replication in vivo. The ectodomain of G is composed of two heavily glycosylated domains with mucin-like characteristics that are separated by a short central region that is relatively devoid of glycosylation sites. This central region contains a 13-amino acid segment that is conserved in the same form among RSV isolates and is overlapped by a second segment containing four cysteine residues whose spacings are conserved in the same form and which create a cystine noose. The conserved nature of the cystine noose and flanking 13-amino acid segment suggested that this region likely was important for attachment activity. To test this hypothesis, we constructed recombinant RSVs from which the region containing the cysteine residues was deleted together with part or all of the conserved 13-amino acid segment. Surprisingly, each deletion had little or no effect on the intracellular synthesis and processing of the G protein, the kinetics or efficiency of virus replication in vitro, or sensitivity to neutralization by soluble heparin in vitro. In addition, neither deletion had any discernible effect on the ability of RSV to infect the upper respiratory tract of mice and both resulted in a 3- to 10-fold reduction in the lower respiratory tract. Thus, although the G protein is necessary for efficient virus replication in vivo, this activity does not require the central conserved cystine noose region.

scholarly journals RSV604, a Novel Inhibitor of Respiratory Syncytial Virus Replication

2007 ◽  
Vol 51 (9) ◽  
pp. 3346-3353 ◽  
Author(s):  
Joanna Chapman ◽  
Elizabeth Abbott ◽  
Dagmar G. Alber ◽  
Robert C. Baxter ◽  
Sian K. Bithell ◽  
...  
Keyword(s):  
Respiratory Syncytial Virus ◽  
Virus Replication ◽  
Cell Model ◽  
Antiviral Treatment ◽  
Effective Vaccine ◽  
Initial Development ◽  
Basolateral Side ◽  
Syncytial Virus ◽  
Tract Infections

ABSTRACT Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infections worldwide, yet no effective vaccine or antiviral treatment is available. Here we report the discovery and initial development of RSV604, a novel benzodiazepine with submicromolar anti-RSV activity. It proved to be equipotent against all clinical isolates tested of both the A and B subtypes of the virus. The compound has a low rate of in vitro resistance development. Sequencing revealed that the resistant virus had mutations within the nucleocapsid protein. This is a novel mechanism of action for anti-RSV compounds. In a three-dimensional human airway epithelial cell model, RSV604 was able to pass from the basolateral side of the epithelium effectively to inhibit virus replication after mucosal inoculation. RSV604, which is currently in phase II clinical trials, represents the first in a new class of RSV inhibitors and may have significant potential for the effective treatment of RSV disease.

scholarly journals The Secreted Form of Respiratory Syncytial Virus G Glycoprotein Helps the Virus Evade Antibody-Mediated Restriction of Replication by Acting as an Antigen Decoy and through Effects on Fc Receptor-Bearing Leukocytes

2008 ◽  
Vol 82 (24) ◽  
pp. 12191-12204 ◽  
Author(s):  
Alexander Bukreyev ◽  
Lijuan Yang ◽  
Jens Fricke ◽  
Lily Cheng ◽  
Jerrold M. Ward ◽  
...  
Keyword(s):  
Respiratory Syncytial Virus ◽  
Neutralizing Antibodies ◽  
Inflammatory Cells ◽  
Antiviral Effect ◽  
Specific Antibodies ◽  
Membrane Bound ◽  
Syncytial Virus ◽  
Prior Infection

ABSTRACT Respiratory syncytial virus (RSV) readily infects and reinfects during infancy and throughout life, despite maternal antibodies and immunity from prior infection and without the need for significant antigenic change. RSV has two neutralization antigens, the F and G virion glycoproteins. G is expressed in both membrane-bound (mG) and secreted (sG) forms. We investigated whether sG might act as a decoy for neutralizing antibodies by comparing the in vitro neutralization of wild-type (wt) RSV versus recombinant mG RSV expressing only mG. wt RSV indeed was less susceptible than mG RSV to monovalent G-specific and polyvalent RSV-specific antibodies, whereas susceptibility to F-specific antibodies was equivalent. This difference disappeared when the virus preparations were purified to remove sG. Thus, sG appears to function as a neutralization decoy. We evaluated this effect in vivo in mice by comparing the effects of passively transferred antibodies on the pulmonary replication of wt RSV versus mG RSV. Again, wt RSV was less sensitive than mG RSV to G-specific and RSV-specific antibodies; however, a similar difference was also observed with F-specific antibodies. This confirmed that sG helps wt RSV evade the antibody-dependent restriction of replication but indicated that in mice, it is not acting primarily as a decoy for G-specific antibodies, perhaps because sG is produced in insufficient quantities in this poorly permissive animal. Rather, we found that the greater sensitivity of mG versus wt RSV to the antiviral effect of passively transferred RSV antibodies required the presence of inflammatory cells in the lung and was Fcγ receptor dependent. Thus, sG helps RSV escape the antibody-dependent restriction of replication via effects as an antigen decoy and as a modulator of leukocytes bearing Fcγ receptors.

scholarly journals 4'-Fluorouridine is a broad-spectrum orally efficacious antiviral blocking respiratory syncytial virus and SARS-CoV-2 replication

2021 ◽  
Author(s):  
Julien Sourimant ◽  
Carolin Lieber ◽  
Megha Aggarwal ◽  
Robert Cox ◽  
Josef Wolf ◽  
...  
Keyword(s):  
Respiratory Syncytial Virus ◽  
Broad Spectrum ◽  
Rna Virus ◽  
Oral Treatment ◽  
The Elderly ◽  
Virus Infections ◽  
Once Daily ◽  
Syncytial Virus ◽  
Well Differentiated

The COVID-19 pandemic has underscored the critical need for broad-spectrum therapeutics against respiratory viruses. Respiratory syncytial virus (RSV) is a major threat to pediatric patients and the elderly. We describe 4'-fluorouridine (4'-FlU, EIDD-2749), a ribonucleoside analog that inhibits RSV, related RNA viruses, and SARS-CoV-2 with high selectivity index in cells and well-differentiated human airway epithelia. Polymerase inhibition in in vitro RdRP assays established for RSV and SARS-CoV-2 revealed transcriptional pauses at positions i or i+3/4 post-incorporation. Once-daily oral treatment was highly efficacious at 5 mg/kg in RSV-infected mice or 20 mg/kg in ferrets infected with SARS-CoV-2 WA1/2020 or variant-of-concern (VoC) isolate CA/2020, initiated 24 or 12 hours after infection, respectively. These properties define 4'-FlU as a broad-spectrum candidate for the treatment of RSV, SARS-CoV-2 and related RNA virus infections.

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