Limits...
Does pandemic A/H1N1 virus have the potential to become more pathogenic?

Ilyushina NA, Ducatez MF, Rehg JE, Marathe BM, Marjuki H, Bovin NV, Webster RG, Webby RJ - MBio (2010)

Bottom Line: When the pandemic virus was initially present at multiplicities of infection equal to or greater than those for the seasonal virus, only pandemic virus genotypes were detected.These adapted pandemic strains did, however, contain two nonsynonymous mutations (hemagglutinin K154Q and polymerase acidic protein L295P) that conferred a more virulent phenotype, both in cell cultures and in ferrets, than their parental strains.Our study demonstrates that the emergence of an A/H1N1 pandemic strain of higher virulence is possible and that, despite their lack of detection thus far in humans, viable seasonal/pandemic virus reassortants can be generated.

View Article: PubMed Central - PubMed

Affiliation: Department of Infectious Diseases, St. Jude Children’s Research Hospital, Memphis, Tennessee, USA.

ABSTRACT
Epidemiologic observations that have been made in the context of the current pandemic influenza virus include a stable virulence phenotype and a lack of propensity to reassort with seasonal strains. In an attempt to determine whether either of these observations could change in the future, we coinfected differentiated human airway cells with seasonal oseltamivir-resistant A/New Jersey/15/07 and pandemic A/Tennessee/1-560/09 (H1N1) viruses in three ratios (10:90, 50:50, and 90:10) and examined the resulting progeny viruses after 10 sequential passages. When the pandemic virus was initially present at multiplicities of infection equal to or greater than those for the seasonal virus, only pandemic virus genotypes were detected. These adapted pandemic strains did, however, contain two nonsynonymous mutations (hemagglutinin K154Q and polymerase acidic protein L295P) that conferred a more virulent phenotype, both in cell cultures and in ferrets, than their parental strains. The polymerase acidic protein mutation increased polymerase activity at 37°C, and the hemagglutinin change affected binding of the virus to α2,6-sialyl receptors. When the seasonal A/H1N1 virus was initially present in excess, the dominant progeny virus was a reassortant containing the hemagglutinin gene from the seasonal strain and the remaining genes from the pandemic virus. Our study demonstrates that the emergence of an A/H1N1 pandemic strain of higher virulence is possible and that, despite their lack of detection thus far in humans, viable seasonal/pandemic virus reassortants can be generated.

Show MeSH

Related in: MedlinePlus

Genotypes of virus populations recovered after three sequential passages in cultures of differentiated normal human bronchial epithelial (NHBE) cells coinfected with 10% NJ/15-90% TN/560 (A), 50% NJ/15-50% TN/560 (B), and 90% NJ/15-10% TN/560 (C) mixtures of seasonal and pandemic H1N1 influenza viruses. Results are shown for genotypes of NJ/15 or TN/560 or dual genotypes of plaque-purified viruses (n = 25).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2993010&req=5

f1: Genotypes of virus populations recovered after three sequential passages in cultures of differentiated normal human bronchial epithelial (NHBE) cells coinfected with 10% NJ/15-90% TN/560 (A), 50% NJ/15-50% TN/560 (B), and 90% NJ/15-10% TN/560 (C) mixtures of seasonal and pandemic H1N1 influenza viruses. Results are shown for genotypes of NJ/15 or TN/560 or dual genotypes of plaque-purified viruses (n = 25).

Mentions: We used differentiated normal human bronchial epithelial (NHBE) cells as a model to mimic A/H1N1 virus evolution in humans. NHBE cells were coinfected with oseltamivir-resistant seasonal A/New Jersey/15/07 (NJ/15) and pandemic A/Tennessee/1-560/09 (TN/560) (H1N1) viruses in different ratios (10:90, 50:50, and 90:10). The virus mixtures were serially passaged 10 times to provide an opportunity for selection of efficiently adapted genotypes. After three sequential passages, viruses isolated from all coinfection groups were plaque purified in Madin-Darby canine kidney (MDCK) cells, and 25 clones per group were genotyped to establish the origin of each of the eight genes that constitute the influenza virus (Fig. 1) (8, 9). The method was not quantitative and was used as a rough estimate of virus genes present. Among all the samples analyzed, TN/560 dominated over NJ/15, although dual genotypes (plaques containing the same genes of both parental viruses) were still present for all genes and in all three groups. Notably, viruses carrying the NJ/15 hemagglutinin (HA) gene were isolated at higher frequencies (39 to 50%) from NHBE cultures that were initially coinfected with a proportion of seasonal A/H1N1 equal to or higher than that of the pandemic virus (Fig. 1B and C).


Does pandemic A/H1N1 virus have the potential to become more pathogenic?

Ilyushina NA, Ducatez MF, Rehg JE, Marathe BM, Marjuki H, Bovin NV, Webster RG, Webby RJ - MBio (2010)

Genotypes of virus populations recovered after three sequential passages in cultures of differentiated normal human bronchial epithelial (NHBE) cells coinfected with 10% NJ/15-90% TN/560 (A), 50% NJ/15-50% TN/560 (B), and 90% NJ/15-10% TN/560 (C) mixtures of seasonal and pandemic H1N1 influenza viruses. Results are shown for genotypes of NJ/15 or TN/560 or dual genotypes of plaque-purified viruses (n = 25).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2993010&req=5

f1: Genotypes of virus populations recovered after three sequential passages in cultures of differentiated normal human bronchial epithelial (NHBE) cells coinfected with 10% NJ/15-90% TN/560 (A), 50% NJ/15-50% TN/560 (B), and 90% NJ/15-10% TN/560 (C) mixtures of seasonal and pandemic H1N1 influenza viruses. Results are shown for genotypes of NJ/15 or TN/560 or dual genotypes of plaque-purified viruses (n = 25).
Mentions: We used differentiated normal human bronchial epithelial (NHBE) cells as a model to mimic A/H1N1 virus evolution in humans. NHBE cells were coinfected with oseltamivir-resistant seasonal A/New Jersey/15/07 (NJ/15) and pandemic A/Tennessee/1-560/09 (TN/560) (H1N1) viruses in different ratios (10:90, 50:50, and 90:10). The virus mixtures were serially passaged 10 times to provide an opportunity for selection of efficiently adapted genotypes. After three sequential passages, viruses isolated from all coinfection groups were plaque purified in Madin-Darby canine kidney (MDCK) cells, and 25 clones per group were genotyped to establish the origin of each of the eight genes that constitute the influenza virus (Fig. 1) (8, 9). The method was not quantitative and was used as a rough estimate of virus genes present. Among all the samples analyzed, TN/560 dominated over NJ/15, although dual genotypes (plaques containing the same genes of both parental viruses) were still present for all genes and in all three groups. Notably, viruses carrying the NJ/15 hemagglutinin (HA) gene were isolated at higher frequencies (39 to 50%) from NHBE cultures that were initially coinfected with a proportion of seasonal A/H1N1 equal to or higher than that of the pandemic virus (Fig. 1B and C).

Bottom Line: When the pandemic virus was initially present at multiplicities of infection equal to or greater than those for the seasonal virus, only pandemic virus genotypes were detected.These adapted pandemic strains did, however, contain two nonsynonymous mutations (hemagglutinin K154Q and polymerase acidic protein L295P) that conferred a more virulent phenotype, both in cell cultures and in ferrets, than their parental strains.Our study demonstrates that the emergence of an A/H1N1 pandemic strain of higher virulence is possible and that, despite their lack of detection thus far in humans, viable seasonal/pandemic virus reassortants can be generated.

View Article: PubMed Central - PubMed

Affiliation: Department of Infectious Diseases, St. Jude Children’s Research Hospital, Memphis, Tennessee, USA.

ABSTRACT
Epidemiologic observations that have been made in the context of the current pandemic influenza virus include a stable virulence phenotype and a lack of propensity to reassort with seasonal strains. In an attempt to determine whether either of these observations could change in the future, we coinfected differentiated human airway cells with seasonal oseltamivir-resistant A/New Jersey/15/07 and pandemic A/Tennessee/1-560/09 (H1N1) viruses in three ratios (10:90, 50:50, and 90:10) and examined the resulting progeny viruses after 10 sequential passages. When the pandemic virus was initially present at multiplicities of infection equal to or greater than those for the seasonal virus, only pandemic virus genotypes were detected. These adapted pandemic strains did, however, contain two nonsynonymous mutations (hemagglutinin K154Q and polymerase acidic protein L295P) that conferred a more virulent phenotype, both in cell cultures and in ferrets, than their parental strains. The polymerase acidic protein mutation increased polymerase activity at 37°C, and the hemagglutinin change affected binding of the virus to α2,6-sialyl receptors. When the seasonal A/H1N1 virus was initially present in excess, the dominant progeny virus was a reassortant containing the hemagglutinin gene from the seasonal strain and the remaining genes from the pandemic virus. Our study demonstrates that the emergence of an A/H1N1 pandemic strain of higher virulence is possible and that, despite their lack of detection thus far in humans, viable seasonal/pandemic virus reassortants can be generated.

Show MeSH
Related in: MedlinePlus