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PB1-F2 proteins from H5N1 and 20 century pandemic influenza viruses cause immunopathology.

McAuley JL, Chipuk JE, Boyd KL, Van De Velde N, Green DR, McCullers JA - PLoS Pathog. (2010)

Bottom Line: However, PB1-F2 proteins from the three pandemic strains of the 20(th) century and a highly pathogenic strain of the H5N1 subtype were shown to enhance the lung inflammatory response resulting in increased pathology.Recently circulating seasonal influenza A strains were not capable of this pro-inflammatory function, having lost the PB1-F2 protein's immunostimulatory activity through truncation or mutation during adaptation in humans.These data suggest that the PB1-F2 protein contributes to the virulence of pandemic strains when the PB1 gene segment is recently derived from the avian reservoir.

View Article: PubMed Central - PubMed

Affiliation: Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee, United States of America.

ABSTRACT
With the recent emergence of a novel pandemic strain, there is presently intense interest in understanding the molecular signatures of virulence of influenza viruses. PB1-F2 proteins from epidemiologically important influenza A virus strains were studied to determine their function and contribution to virulence. Using 27-mer peptides derived from the C-terminal sequence of PB1-F2 and chimeric viruses engineered on a common background, we demonstrated that induction of cell death through PB1-F2 is dependent upon BAK/BAX mediated cytochrome c release from mitochondria. This function was specific for the PB1-F2 protein of A/Puerto Rico/8/34 and was not seen using PB1-F2 peptides derived from past pandemic strains. However, PB1-F2 proteins from the three pandemic strains of the 20(th) century and a highly pathogenic strain of the H5N1 subtype were shown to enhance the lung inflammatory response resulting in increased pathology. Recently circulating seasonal influenza A strains were not capable of this pro-inflammatory function, having lost the PB1-F2 protein's immunostimulatory activity through truncation or mutation during adaptation in humans. These data suggest that the PB1-F2 protein contributes to the virulence of pandemic strains when the PB1 gene segment is recently derived from the avian reservoir.

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Related in: MedlinePlus

PB1-F2 causes cell death.Induction of cell death was determined in human epithelial A549 and mouse macrophage RAW264.7 cell lines by detection of Annexin+PI+ events after A & B) exposure to a panel of 27-mer peptides derived from the C-terminal region of the PB1-F2 protein (see Figure 1 for definition), an N-terminal 27-mer peptide derived from PR8 (final concentration 50 µM for each peptide), or no peptide for 1 hour; and infection with a panel of recombinant virus (see methods for definitions of viruses; the H3N2 PB1 is from A/Wuhan/359/95) at a multiplicity of infection of 1.0 at C) 12 hours and D) 8 hours post-infection. An asterisk (*) indicates a significant difference compared to A) all other peptides and controls, B) all peptides and controls except PR8 and 1918, C &D) all viruses with a PB1 gene segment derived from an H1N1 virus and the no virus control by ANOVA (p<0.05).
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ppat-1001014-g002: PB1-F2 causes cell death.Induction of cell death was determined in human epithelial A549 and mouse macrophage RAW264.7 cell lines by detection of Annexin+PI+ events after A & B) exposure to a panel of 27-mer peptides derived from the C-terminal region of the PB1-F2 protein (see Figure 1 for definition), an N-terminal 27-mer peptide derived from PR8 (final concentration 50 µM for each peptide), or no peptide for 1 hour; and infection with a panel of recombinant virus (see methods for definitions of viruses; the H3N2 PB1 is from A/Wuhan/359/95) at a multiplicity of infection of 1.0 at C) 12 hours and D) 8 hours post-infection. An asterisk (*) indicates a significant difference compared to A) all other peptides and controls, B) all peptides and controls except PR8 and 1918, C &D) all viruses with a PB1 gene segment derived from an H1N1 virus and the no virus control by ANOVA (p<0.05).

Mentions: First, we exposed the human lung epithelial cell line A549 and the BalbcJ mouse derived macrophage cell line RAW264.7 to the panel of peptides for 1 hour at a final concentration of 50µM. Evaluation of necrosis via flow cytometric analysis of AnnexinV+PI+ events revealed that only the peptide derived from the laboratory strain PR8 induced a significant amount of cell death in the human epithelial cell line A549 (Figure 2A). Both PR8 and the peptide derived from the 1918 pandemic strain caused cell death in RAW264.7 cells (Figure 2B), but the 1918 peptide had no effect in A549. Exposure of RAW264.7 or A549 cells to peptides derived from virus strains other than those derived from PR8 or the 1918 strain did not affect viability, similar to exposure to an N-terminal peptide control or unexposed controls. There were negligible AnnexinV+ only events in either cell line exposed to peptides, which suggests that the cells were dying as a result of necrosis in this assay, rather than apoptosis.


PB1-F2 proteins from H5N1 and 20 century pandemic influenza viruses cause immunopathology.

McAuley JL, Chipuk JE, Boyd KL, Van De Velde N, Green DR, McCullers JA - PLoS Pathog. (2010)

PB1-F2 causes cell death.Induction of cell death was determined in human epithelial A549 and mouse macrophage RAW264.7 cell lines by detection of Annexin+PI+ events after A & B) exposure to a panel of 27-mer peptides derived from the C-terminal region of the PB1-F2 protein (see Figure 1 for definition), an N-terminal 27-mer peptide derived from PR8 (final concentration 50 µM for each peptide), or no peptide for 1 hour; and infection with a panel of recombinant virus (see methods for definitions of viruses; the H3N2 PB1 is from A/Wuhan/359/95) at a multiplicity of infection of 1.0 at C) 12 hours and D) 8 hours post-infection. An asterisk (*) indicates a significant difference compared to A) all other peptides and controls, B) all peptides and controls except PR8 and 1918, C &D) all viruses with a PB1 gene segment derived from an H1N1 virus and the no virus control by ANOVA (p<0.05).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2908617&req=5

ppat-1001014-g002: PB1-F2 causes cell death.Induction of cell death was determined in human epithelial A549 and mouse macrophage RAW264.7 cell lines by detection of Annexin+PI+ events after A & B) exposure to a panel of 27-mer peptides derived from the C-terminal region of the PB1-F2 protein (see Figure 1 for definition), an N-terminal 27-mer peptide derived from PR8 (final concentration 50 µM for each peptide), or no peptide for 1 hour; and infection with a panel of recombinant virus (see methods for definitions of viruses; the H3N2 PB1 is from A/Wuhan/359/95) at a multiplicity of infection of 1.0 at C) 12 hours and D) 8 hours post-infection. An asterisk (*) indicates a significant difference compared to A) all other peptides and controls, B) all peptides and controls except PR8 and 1918, C &D) all viruses with a PB1 gene segment derived from an H1N1 virus and the no virus control by ANOVA (p<0.05).
Mentions: First, we exposed the human lung epithelial cell line A549 and the BalbcJ mouse derived macrophage cell line RAW264.7 to the panel of peptides for 1 hour at a final concentration of 50µM. Evaluation of necrosis via flow cytometric analysis of AnnexinV+PI+ events revealed that only the peptide derived from the laboratory strain PR8 induced a significant amount of cell death in the human epithelial cell line A549 (Figure 2A). Both PR8 and the peptide derived from the 1918 pandemic strain caused cell death in RAW264.7 cells (Figure 2B), but the 1918 peptide had no effect in A549. Exposure of RAW264.7 or A549 cells to peptides derived from virus strains other than those derived from PR8 or the 1918 strain did not affect viability, similar to exposure to an N-terminal peptide control or unexposed controls. There were negligible AnnexinV+ only events in either cell line exposed to peptides, which suggests that the cells were dying as a result of necrosis in this assay, rather than apoptosis.

Bottom Line: However, PB1-F2 proteins from the three pandemic strains of the 20(th) century and a highly pathogenic strain of the H5N1 subtype were shown to enhance the lung inflammatory response resulting in increased pathology.Recently circulating seasonal influenza A strains were not capable of this pro-inflammatory function, having lost the PB1-F2 protein's immunostimulatory activity through truncation or mutation during adaptation in humans.These data suggest that the PB1-F2 protein contributes to the virulence of pandemic strains when the PB1 gene segment is recently derived from the avian reservoir.

View Article: PubMed Central - PubMed

Affiliation: Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee, United States of America.

ABSTRACT
With the recent emergence of a novel pandemic strain, there is presently intense interest in understanding the molecular signatures of virulence of influenza viruses. PB1-F2 proteins from epidemiologically important influenza A virus strains were studied to determine their function and contribution to virulence. Using 27-mer peptides derived from the C-terminal sequence of PB1-F2 and chimeric viruses engineered on a common background, we demonstrated that induction of cell death through PB1-F2 is dependent upon BAK/BAX mediated cytochrome c release from mitochondria. This function was specific for the PB1-F2 protein of A/Puerto Rico/8/34 and was not seen using PB1-F2 peptides derived from past pandemic strains. However, PB1-F2 proteins from the three pandemic strains of the 20(th) century and a highly pathogenic strain of the H5N1 subtype were shown to enhance the lung inflammatory response resulting in increased pathology. Recently circulating seasonal influenza A strains were not capable of this pro-inflammatory function, having lost the PB1-F2 protein's immunostimulatory activity through truncation or mutation during adaptation in humans. These data suggest that the PB1-F2 protein contributes to the virulence of pandemic strains when the PB1 gene segment is recently derived from the avian reservoir.

Show MeSH
Related in: MedlinePlus