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Oseltamivir-resistant pandemic A/H1N1 virus is as virulent as its wild-type counterpart in mice and ferrets.

Hamelin ME, Baz M, Abed Y, Couture C, Joubert P, Beaulieu E, Bellerose N, Plante M, Mallett C, Schumer G, Kobinger GP, Boivin G - PLoS Pathog. (2010)

Bottom Line: Such increased levels of IL-6 were also observed in lymph nodes of ferrets infected with the mutant strain.Furthermore, the H274Y mutant strain was transmitted to ferrets.In conclusion, viral fitness of the H274Y pH1N1 isolate is not substantially altered and has the potential to induce severe disease and to disseminate.

View Article: PubMed Central - PubMed

Affiliation: CHUQ-CHUL Research Center in Infectious Diseases and Laval University, Québec City, Québec, Canada.

ABSTRACT
The neuraminidase inhibitor oseltamivir is currently used for treatment of patients infected with the pandemic A/H1N1 (pH1N1) influenza virus, although drug-resistant mutants can emerge rapidly and possibly be transmitted. We describe the characteristics of a pair of oseltamivir-resistant and oseltamivir-susceptible pH1N1 clinical isolates that differed by a single change (H274Y) in the neuraminidase protein. Viral fitness of pH1N1 isolates was assessed in vitro by determining replication kinetics in MDCK alpha2,6 cells and in vivo by performing experimental infections of BALB/c mice and ferrets. Despite slightly reduced propagation of the mutant isolate in vitro during the first 24 h, the wild-type (WT) and mutant resistant viruses induced similar maximum weight loss in mice and ferrets with an identical pyrexic response in ferrets (AUC of 233.9 and 233.2, P = 0.5156). Similarly, comparable titers were obtained for the WT and the mutant strains on days 1, 3, 6 and 9 post-infection in mouse lungs and on days 1-7 in ferret nasal washes. A more important perivascular (day 6) and pleural (days 6 and 12) inflammation was noted in the lungs of mice infected with the H274Y mutant, which correlated with increased pulmonary levels of IL-6 and KC. Such increased levels of IL-6 were also observed in lymph nodes of ferrets infected with the mutant strain. Furthermore, the H274Y mutant strain was transmitted to ferrets. In conclusion, viral fitness of the H274Y pH1N1 isolate is not substantially altered and has the potential to induce severe disease and to disseminate.

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Related in: MedlinePlus

Lung viral titers of mice infected with wild-type (WT) or H274Y mutant isolates of pH1N1.Mice were infected intranasally with 5×105 PFUs of either WT pH1N1 (A/Québec/147023/2009) or oseltamivir-resistant H274Y mutant (A/Québec/147365/2009) isolate. Three to four mice per group were sacrificed on days 1, 3, 6 and 9 for determination of lung viral titers, which were reported as TCID50 per gram of lung.
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ppat-1001015-g003: Lung viral titers of mice infected with wild-type (WT) or H274Y mutant isolates of pH1N1.Mice were infected intranasally with 5×105 PFUs of either WT pH1N1 (A/Québec/147023/2009) or oseltamivir-resistant H274Y mutant (A/Québec/147365/2009) isolate. Three to four mice per group were sacrificed on days 1, 3, 6 and 9 for determination of lung viral titers, which were reported as TCID50 per gram of lung.

Mentions: Two separate mouse experiments were conducted to assess weight loss, clinical signs, viral titers (on days 3 and 6 in the first experiment and on days 1, 6 and 9 in the second experiment) and histopathological changes. In the first experiment, the WT and oseltamivir-resistant pH1N1 isolates induced similar maximum weight loss, which peaked on day 8 at 16.3% for both groups (P = 0.81) although there was a more pronounced weight loss from days 3 to 7 with the mutant strain (Figure 2). In the second experiment, more weight loss was induced after infection with the H274Y mutant from days 3 to 8. By day 12, all mice from the two experiments had returned to their initial weight with no mortality. Lung viral titers, which were determined on days 1, 3, 6 and 9 post-infection, did not significantly differ between the WT and H274Y mutant viruses when assessed by quantitative viral culture (Figure 3) and real-time RT-PCR (Figure S1). Importantly, there was no unexpected change in the NA sequence of viruses recovered from lungs of euthanized mice.


Oseltamivir-resistant pandemic A/H1N1 virus is as virulent as its wild-type counterpart in mice and ferrets.

Hamelin ME, Baz M, Abed Y, Couture C, Joubert P, Beaulieu E, Bellerose N, Plante M, Mallett C, Schumer G, Kobinger GP, Boivin G - PLoS Pathog. (2010)

Lung viral titers of mice infected with wild-type (WT) or H274Y mutant isolates of pH1N1.Mice were infected intranasally with 5×105 PFUs of either WT pH1N1 (A/Québec/147023/2009) or oseltamivir-resistant H274Y mutant (A/Québec/147365/2009) isolate. Three to four mice per group were sacrificed on days 1, 3, 6 and 9 for determination of lung viral titers, which were reported as TCID50 per gram of lung.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2908621&req=5

ppat-1001015-g003: Lung viral titers of mice infected with wild-type (WT) or H274Y mutant isolates of pH1N1.Mice were infected intranasally with 5×105 PFUs of either WT pH1N1 (A/Québec/147023/2009) or oseltamivir-resistant H274Y mutant (A/Québec/147365/2009) isolate. Three to four mice per group were sacrificed on days 1, 3, 6 and 9 for determination of lung viral titers, which were reported as TCID50 per gram of lung.
Mentions: Two separate mouse experiments were conducted to assess weight loss, clinical signs, viral titers (on days 3 and 6 in the first experiment and on days 1, 6 and 9 in the second experiment) and histopathological changes. In the first experiment, the WT and oseltamivir-resistant pH1N1 isolates induced similar maximum weight loss, which peaked on day 8 at 16.3% for both groups (P = 0.81) although there was a more pronounced weight loss from days 3 to 7 with the mutant strain (Figure 2). In the second experiment, more weight loss was induced after infection with the H274Y mutant from days 3 to 8. By day 12, all mice from the two experiments had returned to their initial weight with no mortality. Lung viral titers, which were determined on days 1, 3, 6 and 9 post-infection, did not significantly differ between the WT and H274Y mutant viruses when assessed by quantitative viral culture (Figure 3) and real-time RT-PCR (Figure S1). Importantly, there was no unexpected change in the NA sequence of viruses recovered from lungs of euthanized mice.

Bottom Line: Such increased levels of IL-6 were also observed in lymph nodes of ferrets infected with the mutant strain.Furthermore, the H274Y mutant strain was transmitted to ferrets.In conclusion, viral fitness of the H274Y pH1N1 isolate is not substantially altered and has the potential to induce severe disease and to disseminate.

View Article: PubMed Central - PubMed

Affiliation: CHUQ-CHUL Research Center in Infectious Diseases and Laval University, Québec City, Québec, Canada.

ABSTRACT
The neuraminidase inhibitor oseltamivir is currently used for treatment of patients infected with the pandemic A/H1N1 (pH1N1) influenza virus, although drug-resistant mutants can emerge rapidly and possibly be transmitted. We describe the characteristics of a pair of oseltamivir-resistant and oseltamivir-susceptible pH1N1 clinical isolates that differed by a single change (H274Y) in the neuraminidase protein. Viral fitness of pH1N1 isolates was assessed in vitro by determining replication kinetics in MDCK alpha2,6 cells and in vivo by performing experimental infections of BALB/c mice and ferrets. Despite slightly reduced propagation of the mutant isolate in vitro during the first 24 h, the wild-type (WT) and mutant resistant viruses induced similar maximum weight loss in mice and ferrets with an identical pyrexic response in ferrets (AUC of 233.9 and 233.2, P = 0.5156). Similarly, comparable titers were obtained for the WT and the mutant strains on days 1, 3, 6 and 9 post-infection in mouse lungs and on days 1-7 in ferret nasal washes. A more important perivascular (day 6) and pleural (days 6 and 12) inflammation was noted in the lungs of mice infected with the H274Y mutant, which correlated with increased pulmonary levels of IL-6 and KC. Such increased levels of IL-6 were also observed in lymph nodes of ferrets infected with the mutant strain. Furthermore, the H274Y mutant strain was transmitted to ferrets. In conclusion, viral fitness of the H274Y pH1N1 isolate is not substantially altered and has the potential to induce severe disease and to disseminate.

Show MeSH
Related in: MedlinePlus