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Influenza B virus lineage does not affect antiviral sensitivity, virus outcomes
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Influenza B virus lineage did not appear to impact neuraminidase sensitivity, time to virus clearance or time to symptom resolution, according to recent data.
In their analysis, researchers evaluated influenza B samples from 914 patients enrolled from January 2009 to March 2013 in the Influenza Resistance Information Study (IRIS). The lineage of all examined samples was established by coordinating hemagglutinin (HA) sequences with the reference strain B/Brisbane/60/2008e for B/Victoria and strain B/Managua/3759.01/2008 for B/Yamagata. Clinical and virological data were separately assessed for the B/Victoria and B/Yamagata virus lineages, and the investigators calculated the mean IC50 for all samples tested. Samples were tested for sensitivity to neuraminidase inhibitors (NAIs), and Kaplan-Meier plots were generated for time to viral RNA clearance, time to symptom resolution, and time to resolution of fever. Finally, Wilcoxon tests were conducted to compare the differences in these outcomes between B/Victoria and B/Yamagata lineages.
The researchers found that 586 of the patients with influenza B infection were of B/Victoria lineage, 289 were B/Yamagata, and 39 were not typed. Antivirals were used to treat 474 of the patients: 426 initiated oseltamivir monotherapy within 2 days of symptom emergence, and 34 started oseltamivir 2 or more days after symptom onset. Twelve of the patients were treated with zanamivir monotherapy, one was treated with amantadine, and one received rimantadine.
Among both B/Victoria and B/Yamagata viruses, no phenotypic resistance to oseltamivir or zanamivir was observed. Neuraminidase sequencing detected two predefined resistance mutations; I221T had decreased sensitivity to oseltamivir, and I221V demonstrated sensitivity to NAI inhibition. Times to viral clearance or symptom/fever resolution did not show any consistent disparities between virus lineages.
“From analysis of this comprehensive dataset, we conclude that influenza B viruses of both lineages were phenotypically sensitive to NAIs, with a very low incidence of naturally occurring resistance-associated mutations and no treatment-emergent resistance,” the researchers wrote. “In addition, despite a difference in baseline viral load between the two virus lineages, the duration of viral positivity and influenza symptoms was very similar.” – by Jen Byrne
Disclosure: Van der Vries reports no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.
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