Furthermore, these VLPs induced broad sero- and HI-reactivity. Based on this data we speculate that the vaccine could also protect against other,

divergent H7 strains. We have previously shown that the presence of active baculovirus in insect cell-derived VLP preparation is able to substantially increase immunogenicity and protection due to its immune-stimulatory capability [16]. We would assume that they play a substantial role in the efficacy and potent immunogenicity of the H7 VLP vaccine tested here. VLP vaccines that contain baculoviruses might prove to be useful in pandemic situations where large quantities of highly effective find more vaccines are needed. However, bioactive, live viruses in vaccine formulations might induce strong reactogenicity and safety concerns might prevent their application in humans. Importantly, a bioactive baculovirus component of a vaccine

would need to be standardised and tested for stability under different storage conditions. In addition it would be necessary to assess the minimum effective concentration of baculovirus in a vaccine dose and to establish an acceptable HA or VLP to active baculovirus ratio. Assessment of the latter ratio might be difficult due to the presence of baculovirus–VLP hybrids – baculovirus particles Cyclopamine that incorporate HA and VLPs that incorporate baculovirus capsid and envelope not proteins [45] and [46]. As a large body of research is currently focusing on baculovirus-based expression systems in vaccine manufacturing, more safety data will accumulate and more analytical methods will become available for this system in the near future [46] and [47] and might possibly spur its establishment in human applications. We thank Stefan Gross and Chen Wang for technical assistance. MK and MW are funded by the PhD programme “BioToP – Biomolecular Technology of Proteins” (Austrian Science Funds, FWF Project W1224). DP was supported

by the Austrian Science Fund (25092-B13). FK was supported by an Erwin Schrödinger fellowship (J 3232) from the Austrian Science Fund. This work was partially supported by CEIRS (Centers for Excellence for Influenza Research and Surveillance grant (HHSN26620070010C), NIH program project grant 1P01AI097092-01A1 and a PATH grant to the Palese and García-Sastre laboratories. Conflict of interest statement: The authors declare that they have no conflict of interest. “
“Influenza is an important cause of death and serious illness, particularly among adults aged ≥65 years and those with certain underlying chronic conditions. In the United States, approximately 226,000 hospital admissions are attributed to influenza each year [1].