scholarly journals A single-amino-acid substitution in the HA protein changes the replication and pathogenicity of the 2009 pandemic A (H1N1) influenza viruses in vitro and in vivo

2010 ◽  
Vol 7 (1) ◽  
pp. 325 ◽  
Author(s):  
Lili Xu ◽  
Linlin Bao ◽  
Qi Lv ◽  
Wei Deng ◽  
Yila Ma ◽  
...  
Keyword(s):  
Amino Acid ◽  
Amino Acid Substitution ◽  
H1n1 Influenza ◽  
Influenza Viruses ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid ◽  
Ha Protein

scholarly journals A Single-Amino-Acid Substitution in a Polymerase Protein of an H5N1 Influenza Virus Is Associated with Systemic Infection and Impaired T-Cell Activation in Mice

2009 ◽  
Vol 83 (21) ◽  
pp. 11102-11115 ◽  
Author(s):  
Jamie L. Fornek ◽  
Laura Gillim-Ross ◽  
Celia Santos ◽  
Victoria Carter ◽  
Jerrold M. Ward ◽  
...  
Keyword(s):  
Immune Response ◽  
Influenza Virus ◽  
Amino Acid ◽  
T Cell ◽  
Amino Acid Substitution ◽  
Systemic Infection ◽  
Influenza Viruses ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid ◽  
H5n1 Influenza

ABSTRACT The transmission of H5N1 influenza viruses from birds to humans poses a significant public health threat. A substitution of glutamic acid for lysine at position 627 of the PB2 protein of H5N1 viruses has been identified as a virulence determinant. We utilized the BALB/c mouse model of H5N1 infection to examine how this substitution affects virus-host interactions and leads to systemic infection. Mice infected with H5N1 viruses containing lysine at amino acid 627 in the PB2 protein exhibited an increased severity of lesions in the lung parenchyma and the spleen, increased apoptosis in the lungs, and a decrease in oxygen saturation. Gene expression profiling revealed that T-cell receptor activation was impaired at 2 days postinfection (dpi) in the lungs of mice infected with these viruses. The inflammatory response was highly activated in the lungs of mice infected with these viruses and was sustained at 4 dpi. In the spleen, immune-related processes including NK cell cytotoxicity and antigen presentation were highly activated by 2 dpi. These differences are not attributable solely to differences in viral replication in the lungs but to an inefficient immune response early in infection as well. The timing and magnitude of the immune response to highly pathogenic influenza viruses is critical in determining the outcome of infection. The disruption of these factors by a single-amino-acid substitution in a polymerase protein of an influenza virus is associated with severe disease and correlates with the spread of the virus to extrapulmonary sites.

scholarly journals Infection of Human Dendritic Cells by a Sindbis Virus Replicon Vector Is Determined by a Single Amino Acid Substitution in the E2 Glycoprotein

2000 ◽  
Vol 74 (24) ◽  
pp. 11849-11857 ◽  
Author(s):  
Jason P. Gardner ◽  
Ilya Frolov ◽  
Silvia Perri ◽  
Yaying Ji ◽  
Mary Lee MacKichan ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Amino Acid ◽  
Amino Acid Substitution ◽  
Sindbis Virus ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid ◽  
E2 Glycoprotein ◽  
Human Dendritic Cells ◽  
Antigen Presenting

ABSTRACT The ability to target antigen-presenting cells with vectors encoding desired antigens holds the promise of potent prophylactic and therapeutic vaccines for infectious diseases and cancer. Toward this goal, we derived variants of the prototype alphavirus, Sindbis virus (SIN), with differential abilities to infect human dendritic cells. Cloning and sequencing of the SIN variant genomes revealed that the genetic determinant for human dendritic cell (DC) tropism mapped to a single amino acid substitution at residue 160 of the envelope glycoprotein E2. Packaging of SIN replicon vectors with the E2 glycoprotein from a DC-tropic variant conferred a similar ability to efficiently infect immature human DC, whereupon those DC were observed to undergo rapid activation and maturation. The SIN replicon particles infected skin-resident mouse DC in vivo, which subsequently migrated to the draining lymph nodes and upregulated cell surface expression of major histocompatibility complex and costimulatory molecules. Furthermore, SIN replicon particles encoding human immunodeficiency virus type 1 p55Gag elicited robust Gag-specific T-cell responses in vitro and in vivo, demonstrating that infected DC maintained their ability to process and present replicon-encoded antigen. Interestingly, human and mouse DC were differentially infected by selected SIN variants, suggesting differences in receptor expression between human and murine DC. Taken together, these data illustrate the tremendous potential of using a directed approach in generating alphavirus vaccine vectors that target and activate antigen-presenting cells, resulting in robust antigen-specific immune responses.

scholarly journals Virus Susceptibility Analyses from a Phase IV Clinical Trial of Inhaled Zanamivir Treatment in Children Infected with Influenza

2013 ◽  
Vol 57 (4) ◽  
pp. 1677-1684 ◽  
Author(s):  
Phillip J. Yates ◽  
Nalini Mehta ◽  
Joseph Horton ◽  
Margaret Tisdale
Keyword(s):  
Amino Acid ◽  
Amino Acid Substitution ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Drug Pressure ◽  
Receptor Binding Site ◽  
Virus Susceptibility ◽  
Susceptibility Data

ABSTRACTA zanamivir postapproval efficacy study was conducted in children (n= 279) in Japan during three influenza seasons. Pharyngeal swab specimens (n= 714) were obtained for detailed resistance analysis. From 371 cultured viruses, 3 viruses (A/H1N1) from two subjects showed reduced susceptibility to zanamivir at day 1 (before treatment), 1 had an N74S amino acid substitution (fold shift, 46), and 2 (day 1 and day 2) had a Q136K amino acid substitution (fold shifts, 292 and 301). Q136K was detected only in cultured virus and not in the swab. From the remaining 118 cultured viruses obtained during or after treatment with zanamivir, no shifts in virus susceptibility were detected. Neuraminidase (NA) population sequencing showed that viruses from 12 subjects had emergent amino acid substitutions, but 3 with susceptibility data were not zanamivir resistant. The remainder may be natural variants. Further analysis is planned. Hemagglutinin (HA) sequencing showed that viruses from 20 subjects had 9 HA amino acid substitutions that were previously implicated in resistance to neuraminidase inhibitors inin vitroassays or that were close to the receptor binding site. Their role inin vivoresistance appears to be less important but is not well understood. NA clonal sequence analysis was undertaken to determine if minority species of resistant viruses were present. A total of 1,682 clones from 90 subjects were analyzed. Single clones from 12 subjects contained amino acid substitutions close to the NA active site. It is unclear whether these single amino acid substitutions could have been amplified after drug pressure or are just chance mutations introduced during PCR.

scholarly journals Evolution of moth sex pheromone composition by a single amino acid substitution in a fatty acid desaturase

2015 ◽  
Vol 112 (41) ◽  
pp. 12586-12591 ◽  
Author(s):  
Aleš Buček ◽  
Petra Matoušková ◽  
Heiko Vogel ◽  
Petr Šebesta ◽  
Ullrich Jahn ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Amino Acid ◽  
Amino Acid Substitution ◽  
Functional Characterization ◽  
Fatty Acid Desaturase ◽  
Fatty Acyl ◽  
Site Directed Mutagenesis ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid

For sexual communication, moths primarily use blends of fatty acid derivatives containing one or more double bonds in various positions and configurations, called sex pheromones (SPs). To study the molecular basis of novel SP component (SPC) acquisition, we used the tobacco hornworm (Manduca sexta), which uses a blend of mono-, di-, and uncommon triunsaturated fatty acid (3UFA) derivatives as SP. We identified pheromone-biosynthetic fatty acid desaturases (FADs) MsexD3, MsexD5, and MsexD6 abundantly expressed in the M. sexta female pheromone gland. Their functional characterization and in vivo application of FAD substrates indicated that MsexD3 and MsexD5 biosynthesize 3UFAs via E/Z14 desaturation from diunsaturated fatty acids produced by previously characterized Z11-desaturase/conjugase MsexD2. Site-directed mutagenesis of sequentially highly similar MsexD3 and MsexD2 demonstrated that swapping of a single amino acid in the fatty acyl substrate binding tunnel introduces E/Z14-desaturase specificity to mutated MsexD2. Reconstruction of FAD gene phylogeny indicates that MsexD3 was recruited for biosynthesis of 3UFA SPCs in M. sexta lineage via gene duplication and neofunctionalization, whereas MsexD5 representing an alternative 3UFA-producing FAD has been acquired via activation of a presumably inactive ancestral MsexD5. Our results demonstrate that a change as small as a single amino acid substitution in a FAD enzyme might result in the acquisition of new SP compounds.

A single amino acid substitution improves the in vivo immunogenicity of the HPV16 oncoprotein E7(11–20) cytotoxic T lymphocyte epitope

Vaccine ◽  
2005 ◽  
Vol 23 (31) ◽  
pp. 4005-4010 ◽  
Author(s):  
Marco W.J. Schreurs ◽  
Esther W.M. Kueter ◽  
Kirsten B.J. Scholten ◽  
François A. Lemonnier ◽  
Chris J.L.M. Meijer ◽  
...  
Keyword(s):  
Amino Acid ◽  
T Lymphocyte ◽  
Amino Acid Substitution ◽  
Cytotoxic T Lymphocyte ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid

scholarly journals Lessons from a Single Amino Acid Substitution: Anticancer and Antibacterial Properties of Two Phospholipase A2-Derived Peptides

2021 ◽  
Vol 44 (1) ◽  
pp. 46-62
Author(s):  
José R. Almeida ◽  
Bruno Mendes ◽  
Marcelo Lancellotti ◽  
Gilberto C. Franchi ◽  
Óscar Passos ◽  
...  
Keyword(s):  
Amino Acid ◽  
Phospholipase A2 ◽  
Snake Venom ◽  
Amino Acid Substitution ◽  
In Silico ◽  
Fine Tuning ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid ◽  
Significant Activity

The membrane-active nature of phospholipase A2-derived peptides makes them potential candidates for antineoplastic and antibacterial therapies. Two short 13-mer C-terminal fragments taken from snake venom Lys49-PLA2 toxins (p-AppK and p-Acl), differing by a leucine/phenylalanine substitution, were synthesized and their bioactivity was evaluated. Their capacity to interfere with the survival of Gram-positive and Gram-negative bacteria as well as with solid and liquid tumors was assessed in vitro. Toxicity to red blood cells was investigated via in silico and in vitro techniques. The mode of action was mainly studied by molecular dynamics simulations and membrane permeabilization assays. Briefly, both peptides have dual activity, i.e., they act against both bacteria, including multidrug-resistant strains and tumor cells. All tested bacteria were susceptible to both peptides, Pseudomonas aeruginosa being the most affected. RAMOS, K562, NB4, and CEM cells were the main leukemic targets of the peptides. In general, p-Acl showed more significant activity, suggesting that phenylalanine confers advantages to the antibacterial and antitumor mechanism, particularly for osteosarcoma lines (HOS and MG63). Peptide-based treatment increased the uptake of a DNA-intercalating dye by bacteria, suggesting membrane damage. Indeed, p-AppK and p-Acl did not disrupt erythrocyte membranes, in agreement with in silico predictions. The latter revealed that the peptides deform the membrane and increase its permeability by facilitating solvent penetration. This phenomenon is expected to catalyze the permeation of solutes that otherwise could not cross the hydrophobic membrane core. In conclusion, the present study highlights the role of a single amino acid substitution present in natural sequences towards the development of dual-action agents. In other words, dissecting and fine-tuning biomembrane remodeling proteins, such as snake venom phospholipase A2 isoforms, is again demonstrated as a valuable source of therapeutic peptides.

scholarly journals A Region in the Bacillus subtilisTranscription Factor Spo0A That Is Important for spoIIGPromoter Activation

1998 ◽  
Vol 180 (14) ◽  
pp. 3578-3583 ◽  
Author(s):  
Cindy M. Buckner ◽  
Ghislain Schyns ◽  
Charles P. Moran
Keyword(s):  
Amino Acid ◽  
Dna Binding ◽  
Rna Polymerase ◽  
Amino Acid Substitution ◽  
Dna Binding Protein ◽  
Single Amino Acid ◽  
Promoter Activation ◽  
Additional Amino Acid

ABSTRACT Spo0A is a DNA binding protein in Bacillus subtilisrequired for the activation of spoIIG and other promoters at the onset of endospore formation. Activation of some of these promoters may involve interaction of Spo0A and the ςAsubunit of RNA polymerase. Previous studies identified two single-amino-acid substitutions in ςA, K356E and H359R, that specifically impaired Spo0A-dependent transcription in vivo. Here we report the identification of an amino acid substitution in Spo0A (S231F) that suppressed the sporulation deficiency due to the H359R substitution in ςA. We also found that the S231F substitution partially restored use of the spoIIG promoter by the ςA H359R RNA polymerase in vitro. Alanine substitutions in the 231 region of Spo0A revealed an additional amino acid residue important for spoIIG promoter activation, I229. This amino acid substitution in Spo0A did not affect repression of abrB transcription, indicating that the alanine-substituted Spo0A was not defective in DNA binding. Moreover, the alanine-substituted Spo0A protein activated the spoIIApromoter; therefore, this region of Spo0A is probably not required for Spo0A-dependent, ςH-directed transcription. These and other results suggest that the region of Spo0A near position 229 is involved in ςA-dependent promoter activation.

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