Currently available influenza virus vaccines have inadequate effectiveness and are reformulated annually due to viral antigenic drift. Thus, development of a vaccine that confers long-term protective ...immunity against antigenically distant influenza virus strains is urgently needed. The highly conserved influenza virus hemagglutinin (HA) stalk represents one of the potential targets of broadly protective/universal influenza virus vaccines. Here, we evaluate a potent broadly protective influenza virus vaccine candidate that uses nucleoside-modified and purified mRNA encoding full-length influenza virus HA formulated in lipid nanoparticles (LNPs). We demonstrate that immunization with HA mRNA-LNPs induces antibody responses against the HA stalk domain of influenza virus in mice, rabbits, and ferrets. The HA stalk-specific antibody response is associated with protection from homologous, heterologous, and heterosubtypic influenza virus infection in mice.
Influenza vaccines must be updated regularly because influenza viruses continuously acquire mutations in antibody binding sites of hemagglutinin (HA). The majority of H3N2 strains circulating in the ...Northern Hemisphere during the 2014–2015 season are antigenically mismatched to the A/Texas/50/2012 H3N2 vaccine strain. Recent H3N2 strains possess several new HA mutations, and it is unknown which of these mutations contribute to the 2014–2015 vaccine mismatch. Here, we use reverse genetics to demonstrate that mutations in HA antigenic site B are primarily responsible for the current mismatch. Sera isolated from vaccinated humans and infected ferrets and sheep had reduced hemagglutination inhibition and in vitro neutralization titers against reverse-genetics-derived viruses possessing mutations in the HA antigenic site B. These data provide an antigenic explanation for the low influenza vaccine efficacy observed during the 2014–2015 influenza season. Furthermore, our data support the World Health Organization’s decision to update the H3N2 component of future vaccine formulations.
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•Recent H3N2 strains are antigenically distinct in comparison to the 2014–2015 vaccine strain•Most humans produce antigenic site B HA antibodies•New mutations in antigenic site B of HA likely led to 2014–2015 vaccine mismatch
Most H3N2 influenza viruses circulating during the 2014–2015 influenza season were antigenically mismatched to the H3N2 component of the 2014–2015 influenza vaccine. Chambers et al. use reverse genetics to identify the hemagglutinin mutations responsible for this antigenic mismatch.
Influenza viruses typically cause the most severe disease in children and elderly individuals. However, H1N1 viruses disproportionately affected middle-aged adults during the 2013–2014 influenza ...season. Although H1N1 viruses recently acquired several mutations in the hemagglutinin (HA) glycoprotein, classic serological tests used by surveillance laboratories indicate that these mutations do not change antigenic properties of the virus. Here, we show that one of these mutations is located in a region of HA targeted by antibodies elicited in many middle-aged adults. We find that over 42% of individuals born between 1965 and 1979 possess antibodies that recognize this region of HA. Our findings offer a possible antigenic explanation of why middle-aged adults were highly susceptible to H1N1 viruses during the 2013–2014 influenza season. Our data further suggest that a drifted H1N1 strain should be included in future influenza vaccines to potentially reduce morbidity and mortality in this age group.
Significance Influenza viruses typically cause a higher disease burden in children and the elderly, who have weaker immune systems. During the 2013–2014 influenza season, H1N1 viruses caused an unusually high level of disease in middle-aged adults. Here, we show that recent H1N1 strains possess a mutation that allows viruses to avoid immune responses elicited in middle-aged adults. We show that current vaccine strains elicit immune responses that are predicted to be less effective in some middle-aged adults. We suggest that new viral strains should be incorporated into seasonal influenza vaccines so that proper immunity is elicited in all humans, regardless of age and pre-exposure histories.
Antibodies targeting the receptor binding site (RBS) of the influenza virus hemagglutinin (HA) protein are usually not broadly reactive because their footprints are typically large and extend to ...nearby variable HA residues. Here, we identify several human H3N2 HA RBS-targeting monoclonal antibodies (mAbs) that are sensitive to substitutions in conventional antigenic sites and are therefore not broadly reactive. However, we also identify an H3N2 HA RBS-targeting mAb that is exceptionally broadly reactive despite being sensitive to substitutions in residues outside of the RBS. We show that similar antibodies are present at measurable levels in the sera of some individuals but that they are inefficiently elicited by conventional vaccines. Our data indicate that HA RBS-targeting antibodies can be effective against variable viral strains even when they are somewhat sensitive to substitutions in HA residues adjacent to the RBS.
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•Many mAbs target the RBS of H3 HA, but most are not broadly reactive•Rare H3 HA RBS mAbs are tolerant of substitutions in adjacent sites•Broadly reactive H3 HA RBS Abs are not efficiently elicited by vaccines
Zost et al. show that most antibodies targeting the RBS of the H3N2 HAs are not broadly reactive. They identify one broadly reactive H3 HA RBS antibody that is tolerant of substitutions in adjacent antigenic sites but show that these types of antibodies are not efficiently elicited by vaccination.
Acute respiratory tract viral infections (ARTIs) cause significant morbidity and mortality. CD8 T cells are fundamental to host responses, but transcriptional alterations underlying anti-viral ...mechanisms and links to clinical characteristics remain unclear. CD8 T cell transcriptional circuitry in acutely ill pediatric patients with influenza-like illness was distinct for different viral pathogens. Although changes included expected upregulation of interferon-stimulated genes (ISGs), transcriptional downregulation was prominent upon exposure to innate immune signals in early IFV infection. Network analysis linked changes to severity of infection, asthma, sex, and age. An influenza pediatric signature (IPS) distinguished acute influenza from other ARTIs and outperformed other influenza prediction gene lists. The IPS allowed a deeper investigation of the connection between transcriptional alterations and clinical characteristics of acute illness, including age-based differences in circuits connecting the STAT1/2 pathway to ISGs. A CD8 T cell-focused systems immunology approach in pediatrics identified age-based alterations in ARTI host response pathways.
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•Patients with influenza have distinct transcriptional changes in blood CD8 T cells•Influenza pediatric signature developed that outperforms other prediction gene lists•Gene expression modules correlate with clinical characteristics•Age-dependent alterations in gene circuits underlying host response to influenza
Henrickson et al. measure transcriptional alterations in blood CD8 T cells from pediatric patients with acute respiratory tract infections and correlate gene modules with clinical characteristics. This approach defines an influenza prediction signature that is effective across ages, revealing age-based alterations in genetic circuitry underlying host responses to influenza.
H3N2 viruses continuously acquire mutations in the hemagglutinin (HA) glycoprotein that abrogate binding of human antibodies. During the 2014–2015 influenza season, clade 3C.2a H3N2 viruses ...possessing a new predicted glycosylation site in antigenic site B of HA emerged, and these viruses remain prevalent today. The 2016–2017 seasonal influenza vaccine was updated to include a clade 3C.2a H3N2 strain; however, the egg-adapted version of this viral strain lacks the new putative glycosylation site. Here, we biochemically demonstrate that the HA antigenic site B of circulating clade 3C.2a viruses is glycosylated. We show that antibodies elicited in ferrets and humans exposed to the egg-adapted 2016–2017 H3N2 vaccine strain poorly neutralize a glycosylated clade 3C.2a H3N2 virus. Importantly, antibodies elicited in ferrets infected with the current circulating H3N2 viral strain (that possesses the glycosylation site) and humans vaccinated with baculovirus-expressed H3 antigens (that possess the glycosylation site motif) were able to efficiently recognize a glycosylated clade 3C.2a H3N2 virus. We propose that differences in glycosylation between H3N2 egg-adapted vaccines and circulating strains likely contributed to reduced vaccine effectiveness during the 2016–2017 influenza season. Furthermore, our data suggest that influenza virus antigens prepared via systems not reliant on egg adaptations are more likely to elicit protective antibody responses that are not affected by glycosylation of antigenic site B of H3N2 HA.
Seasonal influenza vaccines offer little protection against pandemic influenza virus strains. It is difficult to create effective prepandemic vaccines because it is uncertain which influenza virus ...subtype will cause the next pandemic. In this work, we developed a nucleoside-modified messenger RNA (mRNA)-lipid nanoparticle vaccine encoding hemagglutinin antigens from all 20 known influenza A virus subtypes and influenza B virus lineages. This multivalent vaccine elicited high levels of cross-reactive and subtype-specific antibodies in mice and ferrets that reacted to all 20 encoded antigens. Vaccination protected mice and ferrets challenged with matched and mismatched viral strains, and this protection was at least partially dependent on antibodies. Our studies indicate that mRNA vaccines can provide protection against antigenically variable viruses by simultaneously inducing antibodies against multiple antigens.
T follicular helper (Tfh) cells are required to develop germinal center (GC) responses and drive immunoglobulin class switch, affinity maturation, and long-term B cell memory. In this study, we ...characterize a recently developed vaccine platform, nucleoside-modified, purified mRNA encapsulated in lipid nanoparticles (mRNA-LNPs), that induces high levels of Tfh and GC B cells. Intradermal vaccination with nucleoside-modified mRNA-LNPs encoding various viral surface antigens elicited polyfunctional, antigen-specific, CD4
T cell responses and potent neutralizing antibody responses in mice and nonhuman primates. Importantly, the strong antigen-specific Tfh cell response and high numbers of GC B cells and plasma cells were associated with long-lived and high-affinity neutralizing antibodies and durable protection. Comparative studies demonstrated that nucleoside-modified mRNA-LNP vaccines outperformed adjuvanted protein and inactivated virus vaccines and pathogen infection. The incorporation of noninflammatory, modified nucleosides in the mRNA is required for the production of large amounts of antigen and for robust immune responses.
Abstract
Background
The H3N2 component of egg-based 2017–2018 influenza vaccines possessed an adaptive substitution that alters antigenicity. Several influenza vaccines include antigens that are ...produced through alternative systems, but a systematic comparison of different vaccines used during the 2017–2018 season has not been completed.
Methods
We compared antibody responses in humans vaccinated with Fluzone (egg-based, n = 23), Fluzone High-Dose (egg-based, n = 16), Flublok (recombinant protein–based, n = 23), or Flucelvax (cell-based, n = 23) during the 2017–2018 season. We completed neutralization assays using an egg-adapted H3N2 virus, a cell-based H3N2 virus, wild-type 3c2.A and 3c2.A2 H3N2 viruses, and the H1N1 vaccine strain. We also performed enzyme-linked immunosorbent assays using a recombinant wild-type 3c2.A hemagglutinin. Antibody responses were compared in adjusted analysis.
Results
Postvaccination neutralizing antibody titers to 3c2.A and 3c2.A2 were higher in Flublok recipients compared with Flucelvax or Fluzone recipients (P < .01). Postvaccination titers to 3c2.A and 3c2.A2 were similar in Flublok and Fluzone High-Dose recipients, though seroconversion rates trended higher in Flublok recipients. Postvaccination titers in Flucelvax recipients were low to all H3N2 viruses tested, including the cell-based H3N2 strain. Postvaccination neutralizing antibody titers to H1N1 were similar among the different vaccine groups.
Conclusions
These data suggest that influenza vaccine antigen match and dose are both important for eliciting optimal H3N2 antibody responses in humans. Future studies should be designed to determine if our findings directly impact vaccine effectiveness.
Clinical Trials Registration
NCT03068949.
We measured antibody responses in humans vaccinated with Fluzone (egg-based), Fluzone High-Dose (egg-based), Flublok (recombinant protein–based), or Flucelvax (cell-based) during the 2017–2018 season. Our studies demonstrate that different influenza vaccine platforms elicit substantially different antibody responses in humans.
Maternal antibodies provide short-term protection to infants against many infections. However, they can inhibit de novo antibody responses in infants elicited by infections or vaccination, leading to ...increased long-term susceptibility to infectious diseases. Thus, there is a need to develop vaccines that are able to elicit protective immune responses in the presence of antigen-specific maternal antibodies. Here, we used a mouse model to demonstrate that influenza virus-specific maternal antibodies inhibited de novo antibody responses in mouse pups elicited by influenza virus infection or administration of conventional influenza vaccines. We found that a recently developed influenza vaccine, nucleoside-modified mRNA encapsulated in lipid nanoparticles (mRNA-LNP), partially overcame this inhibition by maternal antibodies. The mRNA-LNP influenza vaccine established long-lived germinal centers in the mouse pups and elicited stronger antibody responses than did a conventional influenza vaccine approved for use in humans. Vaccination with mRNA-LNP vaccines may offer a promising strategy for generating robust immune responses in infants in the presence of maternal antibodies.
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