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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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PB1-F2 peptides enhance inflammation in the lung.Groups of mice were exposed to a panel of peptides (100 mM final concentration, see Figure 1 for definitions) and euthanized 24 hours later. BAL fluid from the animals was assayed by flow-cytometry [10] for the mean number of A) macrophages and B) neutrophils compared to unexposed mice or mice exposed to an N-terminal control peptide. An asterisk (*) indicates a significant difference compared to the 1995 H3N2 peptide and controls by ANOVA (p<0.05). A double asterisk (**) indicates a significant difference compared to the controls. Error bars indicate the standard deviation from the mean. C) In a separate set of experiments, mice exposed to peptide were monitored for overt signs of illness and percentage change from initial weight. For clarity, peptides are grouped by their inflammatory potential as determined in A & B.
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ppat-1001014-g004: PB1-F2 peptides enhance inflammation in the lung.Groups of mice were exposed to a panel of peptides (100 mM final concentration, see Figure 1 for definitions) and euthanized 24 hours later. BAL fluid from the animals was assayed by flow-cytometry [10] for the mean number of A) macrophages and B) neutrophils compared to unexposed mice or mice exposed to an N-terminal control peptide. An asterisk (*) indicates a significant difference compared to the 1995 H3N2 peptide and controls by ANOVA (p<0.05). A double asterisk (**) indicates a significant difference compared to the controls. Error bars indicate the standard deviation from the mean. C) In a separate set of experiments, mice exposed to peptide were monitored for overt signs of illness and percentage change from initial weight. For clarity, peptides are grouped by their inflammatory potential as determined in A & B.

Mentions: Mice were exposed to a panel of PB1-F2 derived peptides and were euthanized 24 hours later for collection of bronchoalveolar lavage fluid (BALF). C-terminal PB1-F2 peptides derived from PR8, the pandemic strains from 1918 (H1N1), 1957 (H2N2) and 1968 (H3N2), and the 2004 H5N1 virus all caused significant influx of white blood cells into the BALF compared to controls. Several cell types were increased including T-cells (data not shown), dendritic cells (data not shown), macrophages (Figure 4A) and neutrophils (Figure 4B). Interestingly, the peptide derived from a more recent H3N2 strain, A/Wuhan/359/1995, did not cause an appreciable increase in inflammatory cells over controls. When peptide exposed mice were followed for morbidity for 7 days, striking differences were seen comparing the five peptides that caused inflammation with the 1995 H3N2 peptide and the controls. The “pro-inflammatory” peptides caused huddling, hunching, labored breathing, ruffled fur and weight loss which peaked in the first 24–48 hours after exposure, while the “non-inflammatory” exposures caused no clinical signs (data not shown) or weight loss (Figure 4C). Thus, the ability to cause lung inflammation appears to be a property of PB1-F2 proteins recently emerged from the avian gene pool. H1N1 strains circulating in humans since about 1950 have a truncated PB1-F2 that lacks the C-terminal residues responsible for this effect and in contrast to their pandemic forbear from 1968, recently circulating H3N2 strains lack a PB1-F2 capable of causing inflammation.


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 peptides enhance inflammation in the lung.Groups of mice were exposed to a panel of peptides (100 mM final concentration, see Figure 1 for definitions) and euthanized 24 hours later. BAL fluid from the animals was assayed by flow-cytometry [10] for the mean number of A) macrophages and B) neutrophils compared to unexposed mice or mice exposed to an N-terminal control peptide. An asterisk (*) indicates a significant difference compared to the 1995 H3N2 peptide and controls by ANOVA (p<0.05). A double asterisk (**) indicates a significant difference compared to the controls. Error bars indicate the standard deviation from the mean. C) In a separate set of experiments, mice exposed to peptide were monitored for overt signs of illness and percentage change from initial weight. For clarity, peptides are grouped by their inflammatory potential as determined in A & B.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2908617&req=5

ppat-1001014-g004: PB1-F2 peptides enhance inflammation in the lung.Groups of mice were exposed to a panel of peptides (100 mM final concentration, see Figure 1 for definitions) and euthanized 24 hours later. BAL fluid from the animals was assayed by flow-cytometry [10] for the mean number of A) macrophages and B) neutrophils compared to unexposed mice or mice exposed to an N-terminal control peptide. An asterisk (*) indicates a significant difference compared to the 1995 H3N2 peptide and controls by ANOVA (p<0.05). A double asterisk (**) indicates a significant difference compared to the controls. Error bars indicate the standard deviation from the mean. C) In a separate set of experiments, mice exposed to peptide were monitored for overt signs of illness and percentage change from initial weight. For clarity, peptides are grouped by their inflammatory potential as determined in A & B.
Mentions: Mice were exposed to a panel of PB1-F2 derived peptides and were euthanized 24 hours later for collection of bronchoalveolar lavage fluid (BALF). C-terminal PB1-F2 peptides derived from PR8, the pandemic strains from 1918 (H1N1), 1957 (H2N2) and 1968 (H3N2), and the 2004 H5N1 virus all caused significant influx of white blood cells into the BALF compared to controls. Several cell types were increased including T-cells (data not shown), dendritic cells (data not shown), macrophages (Figure 4A) and neutrophils (Figure 4B). Interestingly, the peptide derived from a more recent H3N2 strain, A/Wuhan/359/1995, did not cause an appreciable increase in inflammatory cells over controls. When peptide exposed mice were followed for morbidity for 7 days, striking differences were seen comparing the five peptides that caused inflammation with the 1995 H3N2 peptide and the controls. The “pro-inflammatory” peptides caused huddling, hunching, labored breathing, ruffled fur and weight loss which peaked in the first 24–48 hours after exposure, while the “non-inflammatory” exposures caused no clinical signs (data not shown) or weight loss (Figure 4C). Thus, the ability to cause lung inflammation appears to be a property of PB1-F2 proteins recently emerged from the avian gene pool. H1N1 strains circulating in humans since about 1950 have a truncated PB1-F2 that lacks the C-terminal residues responsible for this effect and in contrast to their pandemic forbear from 1968, recently circulating H3N2 strains lack a PB1-F2 capable of causing inflammation.

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