Egg- or cell culture-derived hemagglutinin mutations impair virus stability and antigen content of inactivated influenza vaccines.

Egg-derived viruses are the only available seed material for influenza vaccine production. Vaccine manufacturing is done in embryonated chicken eggs, MDCK or Vero cells. In order to contribute to efficient production of influenza vaccines, we investigate whether the quality of inactivated vaccines is influenced by the propagation substrate. We demonstrate that H3N2 egg-derived seed viruses (A/Brisbane/10/07, IVR147, and A/Uruguay/716/07) triggered the hemagglutinin (HA) conformational change under less acidic conditions (0.2-0.6 pH units) than antigenically similar primary isolates. This phenotype was associated with HA1 (A138S, L194P) and HA2 (D160N) substitutions, and strongly related to decreased virus stability towards acidic pH and elevated temperature. The subsequent propagation of H3N2 and H1N1 egg-derived seed viruses in MDCK and Vero cells induced HA2 N50K (H1N1) and D160E (H3N2) mutations, improving virus growth in cell culture but further impairing virus stability. The prevention of the loss or recovery of stability was possible by cultivation at acidified conditions. Viruses carrying less stable HAs are more sensitive for HA conformational change during concentration, purification and storage. This results in decreased detectable HA antigen content - the main potency marker for inactivated influenza vaccines. Thus, virus stability can be a useful marker for predicting the manufacturing scope of seed viruses.

An inactivated, adjuvanted whole virion clade 2.2 H5N1 (A/Chicken/Astana/6/05) influenza vaccine is safe and immunogenic in a single dose in humans.

In this study, we assessed in humans the immunogenicity and safety of one dose (7.5 or 15 µg of hemagglutinin [HA]) of a whole-virion inactivated prepandemic influenza vaccine adjuvanted with aluminum hydroxide. The vaccine strain was made by reverse genetics from the highly pathogenic avian A/Chicken/Astana/6/05 (H5N1) clade 2.2 strain isolated from a dead bird in Kazakhstan. The humoral immune response was evaluated after a single vaccination by hemagglutination inhibition (HI) and microneutralization (MN) assays. The vaccine was safe and immunogenic, inducing seroconversion in 55% of the evaluated patients, with a geometric mean titer (GMT) of 17.1 and a geometric mean increase (GMI) of 3.42 after a dose of 7.5 µg in the HI test against the vaccine strain. The rate of seroconversion increased up to 70% when the dose of 15 µg was used. The percentages of individuals achieving anti-HA titers of ≥1:40 were 52.5% and 57.5% for the 7.5- and 15-µg dose groups, respectively. Similar results were obtained when antibodies were analyzed in an MN test. Substantial cross-neutralization titers (seroconversion in 35% and 52.5% of subjects in the two dose groups, respectively) were detected against heterologous clade 1 strain NIBRG14 (H5N1). Thus, one dose of this whole-virion prepandemic vaccine adjuvanted with aluminum has the potential to be effective against H5N1 viruses of different clades.

Fully doped oligomers of emeraldine salt: polaronic versus bipolaronic configuration.

Calculations for model oligomers of the emeraldine salt with UBLYP/6-31G*/PCM are performed. The models differ in number of monomers, in the position of the counterions (Cl(-)), and in multiplicity. The molecular features affected most prominently by the protonation, namely, structure, energetics, and electron and spin density partitioning are analyzed. The results show unequivocally that the studied molecular characteristics are essentially size independent. The octamer profiles of all parameters are repeated in the dodecamer and the hexadecamer. The bipolaronic forms are energetically more favorable than the polaronic ones within the chosen protocol. The electronic structure in the intermediate multiplicities differs from the bipolaronic and polaronic periodicity. The geometrical changes and electron density redistribution upon increase of multiplicity illustrate the pathway of intramolecular bipolaron-polaron conversion. The orbital analysis rationalizes the observed behavior of the oligomers.