Vaccines with MF59 Adjuvant Expand the Antibody Repertoire to Target Protective Sites of Pandemic Avian H5N1 Influenza Virus

Abstract

Vaccines against influenza viruses with pandemic potential, including H5N1, are under development. Because of a lack of preexisting immunity to these viruses, adjuvants (immune potentiators or enhancers) are needed to improve immune responses, to conserve scarce vaccine, and for cross-protection against strains that have drifted evolutionarily from the original. Aluminum-based adjuvants do not improve vaccine immunogenicity for influenza subunit vaccines, whereas oil-in-water adjuvants are effective, especially with H5N1-inactivated vaccines. We used whole-genome-fragment phage display libraries followed by surface plasmon resonance (SPR) technologies to elucidate the effect of different adjuvants on the antibody repertoire against H5N1 vaccine in humans. The oil-in-water adjuvant MF59 induced epitope spreading from HA2 to HA1 in hemagglutinin (HA) and neuraminidase relative to unadjuvanted or aluminum-adjuvanted vaccines. Moreover, we observed an increase by a factor of 20 in the frequency of HA1-to-HA2-specific phage clones in sera after MF59-adjuvanted vaccine administration and a factor of 2 to 3 increase in the avidity of antibodies binding to properly folded HA1(28-319), as measured by SPR. The adjuvant-dependent increase in binding to conformational HA1 epitopes correlated with broadening of cross-clade neutralization and predicted improved in vivo protection. Thus, MF59 adjuvant improves the immune response to a H5N1 vaccine by inducing qualitative and quantitative expansion of the antibody repertoires with protective potential.

Bacterial HA1 Vaccine against Pandemic H5N1 Influenza Virus: Evidence of Oligomerization, Hemagglutination, and Cross-Protective Immunity in Ferrets

“…To better understand the role of HA1 structure-function and its effect on generating protective immunity after immunization, we expressed a series of H5N1-derived HA1 proteins with N-and C-terminal deletions and evaluated their ability to form oligomers and to agglutinate RBCs. The intact H5N1 HA1 and a series of truncated proteins were expressed in E. coli and isolated from inclusion bodies by denaturation and slow renaturation under controlled redox refolding conditions as previously described (11,12). The His 6 -tagged fusion proteins were purified using Ni-NTA chromatography to Ͼ95% purity ( Agglutination of red cells is a surrogate for the binding of influenza virus to its sialic acid receptors.…”

“…Most of the influenza virus protective antigenic sites are conformation dependent and map primarily to the HA1 globular head (22,30). Previously, we used H5N1 whole-genome phage display libraries to map the antibody repertoires following human infection with HP H5N1 (A/Vietnam/1203/2004) AIV, as well as in post-H5N1 vaccination sera (11,12). We have identified large HA1 fragments, encompassing the receptor-binding domain (RBD), that bound broadly neutralizing human monoclonal antibodies and polyclonal sera from H5N1 recovered individuals.…”

H5N1 Virus-Like Particle Vaccine Elicits Cross-Reactive Neutralizing Antibodies That Preferentially Bind to the Oligomeric Form of Influenza Virus Hemagglutinin in Humans

“…FLU-GFPDL (H5N1) allowed the identification of large viral epitopes recognized by antibodies in sera of individuals who recovered from HP H5N1 infection (18). In a follow-up study we deciphered the role of oil-in-water adjuvant in augmenting the immune response following vaccinations against H5N1 (A/Vietnam) and H1N1pdm09 viruses (16,19).…”

MF59^® Adjuvanted Seasonal and Pandemic Influenza Vaccines

“…7,8) As the HA1 contains the viral receptor binding domain and principal neutralizing epitopes, this qualitative shift in the antibody repertoire may explain the more cross-reactive adjuvanted response to antigenically divergent in‰uenza viral strains. In addition, the antibodies also exhibit a higher a‹nity for properly folded HA, seen in higher equilibrium levels and a tenfold increased resistance to dissociation under treatment with 7M urea, as measured by surface plasmon resonance.…”

“…The slower dissociation was highly correlated with increasing neutralizing antibody titer. 7,8) SEASONAL ATIV-OLDER ADULTS ATIV was developed to improve the lower antibody response and suboptimal e‹cacy of TIV in older adults-estimated to be 50％ in the only placebocontrolled trial in this age group. 9,10) Numerous small comparative trials in older adults (over 65 years of age) have shown that hemagglutination inhibition (HI) and microneutraliziation (MNT) antibody responses to ATIV are approximately 1.5 fold higher than to identical but unadjuvanted TIV, with strain to strain variability of the geometric mean ratios (GMR) ranging from 1.2 1.8 fold higher.…”