News Scan for Feb 25, 2016

Saudi MERS cases
Flu vaccine strain recommendation
H1N1 replication study

Saudi Arabia reports 2 more MERS cases

Saudi Arabia's Ministry of Health (MOH) today confirmed two new MERS-CoV cases, both primary infections in men who had indirect contact with camels.

The first MERS-CoV (Middle East respiratory syndrome coronavirus) case-patient is a 60-year-old Saudi man from the southern city of Najran. He is in stable condition and is not a healthcare worker, the MOH said.

The second MERS infection involves a 56-year-old man in the northwestern city of Ha'il. He is hospitalized in critical condition and is not a healthcare worker.

Saudi Arabia has now had 1,302 MERS cases since the outbreak began in 2012, the MOH said. Of those cases, 742 people have recovered, 554 have died, and 6 involve patients still undergoing treatment.
Feb 25 Saudi MOH update


WHO advisers switch out 2 vaccine strains for 2016-17 flu season

Advisers to the World Health Organization (WHO) today recommended changing two of the three strains for the trivalent flu vaccines that manufacturers will make for the Northern Hemisphere's 2016-17 season.

The new recommendation swaps out the H3N2 A/Switzerland-like virus for influenza A/Hong Kong-like H3N2 and replaces the influenza B/Phuket-like virus with an influenza B/Brisbane-like virus. The influenza switch represents a lineage change, from Yamagata to Victoria.

The WHO said there are two newly emerging 2009 H1N1 subclades that continue to evolve, but viruses in them aren't antigenically distinguishable from the A/California-like vaccine strain.

For quadrivalent vaccines that contain vaccine viruses against both influenza B lineages, the WHO team recommends an influenza B/Phuket-like virus for the Yamagata strain.

The new recommendations match the ones the WHO made in September for the Southern Hemisphere's 2016 flu season.

The WHO bases its recommendations on a global analysis of circulating strains and their genetics, announcing its picks several months ahead of the upcoming flu seasons to account for the lengthy process of growing the viruses in eggs and cell culture and then manufacturing scale-up.

In a companion recommendation on the latest circulating zoonotic flu viruses, the same group recommended that two new candidate vaccine viruses be prepared: one against H5N6 avian flu and one against variant H1N1 (H1N1v).
Jan 25 WHO strain selection report
Jan 25 WHO zoonotic influenza candidate vaccine virus recommendations


Study: Mutations lead to increased pH1N1 replication, potential virulence

Experimentally induced adaptations in the 2009 H1N1 influenza virus led to dramatically increased replication rates and decreased receptor-binding affinity in human lung cells, according to findings published this week in Virology.

A team of German and Austrian researchers serially passaged a 2009 H1N1 variant isolate in human A549 lung epithelial cells to determine factors that might affect the strain's future virulence.

After six passages, the virus's replication rate abruptly rose, causing a 100-fold increase in viral titers. Both the original isolate and the adapted strain infected A549 cells with similar effectiveness.

Investigators identified five mutations that occurred with a frequency of more than 20% in viral hemagglutinin (HA). Three of these mutations led to an amino acid change in viral proteins.

Two HA mutations, HA1 D130E and HA2 I91L, caused significant changes to the A549 receptor-binding affinity. The mutation HA1 D130E affects the HA globular head near the cell receptor binding site, while HA2 I91L is located on the HA stem.

HA1 D130E led to an eightfold reduction in cell receptor binding strength and was also responsible for increased viral titers in mice infected with the adapted strain.

The mutation HA1 D130 is significant for future surveillance efforts, as it was seen at a frequency of only 0.14% in H1N1 viruses in 2009 and 2010, yet has increased to a frequency of 2.8% in recent years, the authors note. They said that their study has importance for surveillance of changes in H1N1 virulence and vaccine development needed to respond to potentially high viral titers.
Feb 23 Virology study

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