Pre-vaccination immunity and immune responses to a cell culture-derived whole-virus H1N1 vaccine are similar to a seasonal influenza vaccine
ABSTRACT Immune responses to novel pandemic influenza vaccines may be influenced by previous exposure to antigenically similar seasonal strains.
An open-label, randomized, phase I/II study was conducted to assess the immunogenicity and safety of a non-adjuvanted, inactivated whole-virus H1N1 A/California/07/2009 vaccine. 408 subjects were stratified by age (18-59 and >60 years) and randomized 1:1 to receive two vaccinations with either 3.75 or 7.5 μg hemagglutinin antigen 21 days apart. Safety, immunogenicity and the influence of seasonal influenza vaccination and antibody cross-reactivity with a seasonal H1N1 strain was assessed.
A single vaccination with either dose induced substantial increases in H1N1 A/California/07/2009 hemagglutination inhibition (HI) and neutralizing (MN) antibody titers in both adult and elderly subjects. A single 7.5 μg dose induced seroprotection rates of 86.9% in adults and 75.2% in elderly subjects. Two 7.5 μg vaccinations induced seroprotection rates in adult and elderly subjects of 90.9% and 89.1%, respectively. The robust immune response to vaccination was confirmed by analyses of neutralizing antibody titers. Both HI and MN antibodies persisted for ≥ 6 months post-vaccination. Between 34% and 49% of subjects had seroprotective levels of H1N1 A/California/07/2009 antibodies at baseline. Higher baseline HI titers were associated with receipt of the 2008-09 or 2009-10 seasonal influenza vaccine. High baseline A/California/07/2009 neutralizing antibody titers were also associated with high baseline titers against A/New Caledonia/20/99, a seasonal H1N1 strain which circulated and was included in the seasonal vaccine from 2000-01 to 2006-07. Pre-adsorption with A/H1N1/New Caledonia/20/99 antigen reduced A/H1N1/California/07/2009 baseline titers in 55% of tested sera. The vaccine was well tolerated with low rates of fever.
A whole-virus H1N1 A/California/07/2009 vaccine was safe and well tolerated and a single dose induced substantial immune responses similar to seasonal influenza vaccines, probably due to immunological priming by previous seasonal influenza vaccines or infections.
SourceAvailable from: PubMed Central[Show abstract] [Hide abstract]
ABSTRACT: A novel avian H7N9 virus with a high case fatality rate in humans emerged in China in 2013. We evaluated the immunogenicity and protective efficacy of a candidate Vero cell culture-derived whole-virus H7N9 vaccine in small animal models. Antibody responses induced in immunized DBA/2J mice and guinea pigs were evaluated by hemagglutination inhibition (HI), microneutralization (MN), and neuraminidase inhibition (NAi) assays. T-helper cell responses and IgG subclass responses in mice were analyzed by ELISPOT and ELISA, respectively. Vaccine efficacy against lethal challenge with wild-type H7N9 virus was evaluated in immunized mice. H7N9-specific antibody responses induced in mice and guinea pigs were compared to those induced by a licensed whole-virus pandemic H1N1 (H1N1pdm09) vaccine. The whole-virus H7N9 vaccine induced dose-dependent H7N9-specific HI, MN and NAi antibodies in mice and guinea pigs. Evaluation of T-helper cell responses and IgG subclasses indicated the induction of a balanced Th1/Th2 response. Immunized mice were protected against lethal H7N9 challenge in a dose-dependent manner. H7N9 and H1N1pdm09 vaccines were similarly immunogenic. The induction of H7N9-specific antibody and T cell responses and protection against lethal challenge suggest that the Vero cell culture-derived whole-virus vaccine would provide an effective intervention against the H7N9 virus.PLoS ONE 02/2015; 10(2):e0113963. DOI:10.1371/journal.pone.0113963 · 3.53 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: The threat of an outbreak of avian-origin influenza H7N9 and the devastating consequences that a pandemic could have on global population health and economies has mobilized programs of constant surveillance and the implementation of preemptive plans. Central to these plans is the production of prepandemic vaccines that can be rapidly deployed to minimize disease severity and deaths resulting from such an occurrence. In this article, we review current H7N9 vaccine strategies in place and the available technologies and options that can help accelerate vaccine production and increase dose-sparing capabilities to provide enough vaccines to cover the population. We also present possible means of reducing disease impact during the critical period after an outbreak occurs before a strain matched vaccine becomes available and consider the use of existing stockpiles and seed strains of phylogenetically related subtypes, alternate vaccination regimes and vaccine forms that induce cross-reactive immunity.Expert Review of Vaccines 07/2014; 13(11). DOI:10.1586/14760584.2014.938641 · 4.22 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Studies on candidate pandemic vaccines against avian influenza virus have focussed on H5N1, but viruses of other subtypes, such as A/H9N2, are also considered to have pandemic potential. We investigated the safety and immunogenicity of two immunizations with one of five different antigen doses (ranging from 3.75 to 45 μg hemagglutinin antigen) of a non-adjuvanted, whole-virus G9-lineage H9N2 vaccine in healthy adults aged 18-49 years. Antibody responses were measured by hemagglutination inhibition (HI), microneutralization (MN) and single radial hemolysis (SRH) assays. To investigate a hypothesis that previous exposure to H2N2 viruses in subjects born in or before 1968 might prime for more robust antibody responses to H9N2 vaccination, a post-hoc age-stratified analysis of antibody responses was done. Both vaccinations in all dose groups were safe and well-tolerated. No vaccine-related serious adverse events were reported, and the majority of adverse reactions were rated as mild. Injection site reaction rates were lower in the 3.75 μg and 7.5 μg dose groups compared to the higher dose groups; systemic reaction rates were similar across all dose groups. Seroprotection rates among the different dose groups 21 days after the second immunization ranged from 52.8% to 88.9% measured by HI assay, from 88.7% to 98.1% or 82.7% to 96.2% measured by MN assay (MN titer cut-off 1:40 and 1:80, respectively), and from 94.2% to 100% measured by SRH assay. Higher antibody responses were not induced in subjects born in or before 1968. These data indicate that a non-adjuvanted, whole-virus H9N2 vaccine is well-tolerated and immunogenic in healthy adults.Clinical and vaccine Immunology: CVI 10/2014; DOI:10.1128/CVI.00275-14 · 2.37 Impact Factor