Influenza hemagglutinin stem-fragment immunogen elicits broadly neutralizing antibodies and confers heterologous protection

We assessed whether influenza virus hemagglutinin stalk-based immunity protects ferrets against aerosol-transmitted H1N1 influenza virus infection. Immunization of ferrets by a universal influenza virus vaccine strategy based on viral vectors expressing chimeric hemagglutinin constructs induced stalk-specific antibody responses. Stalk-immunized ferrets were cohoused with H1N1-infected ferrets under conditions that permitted virus transmission. Hemagglutinin stalk-immunized ferrets had lower viral titers and delayed or no virus replication at all following natural exposure to influenza virus.

Section: Figsupporting

confidence: 77%

Hemagglutinin Stalk Immunity Reduces Influenza Virus Replication and Transmission in Ferrets

Nachbagauer

Miller

Hai

et al. 2016

“…A variety of approaches for eliciting HA stalkspecific antibody responses have been evaluated in animal models with various degrees of success (43,(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60). Collectively, these approaches aim to elicit HA stalk-specific responses through tactics that subvert HA globular head immunodominance.…”

Section: Discussionmentioning

confidence: 99%

“…One such tactic is the use of chimeric HA (cHA)-expressing exotic globular heads in the context of group 1 or group 2 stalk domains (61). Another promising approach for eliciting HA stalk-specific antibody responses is the use of stabilized headless HA (50,51,54,58,60). Recently, protection of mice and ferrets against virulent H5N1 influenza viruses was demonstrated following vaccination with an HA-stalk specific immunogen fused to a ferritin nanoparticle (50).…”

Section: Discussionmentioning

confidence: 99%

Sequential Infection in Ferrets with Antigenically Distinct Seasonal H1N1 Influenza Viruses Boosts Hemagglutinin Stalk-Specific Antibodies

Kirchenbaum

Carter

Ross

2016

Broadly reactive antibodies targeting the conserved hemagglutinin (HA) stalk region are elicited following sequential infection or vaccination with influenza viruses belonging to divergent subtypes and/or expressing antigenically distinct HA globular head domains. Here, we demonstrate, through the use of novel chimeric HA proteins and competitive binding assays, that sequential infection of ferrets with antigenically distinct seasonal H1N1 (sH1N1) influenza virus isolates induced an HA stalk-specific antibody response. Additionally, stalk-specific antibody titers were boosted following sequential infection with antigenically distinct sH1N1 isolates in spite of preexisting, cross-reactive, HA-specific antibody titers. Despite a decline in stalk-specific serum antibody titers, sequential sH1N1 influenza virus-infected ferrets were protected from challenge with a novel H1N1 influenza virus (A/California/07/2009), and these ferrets poorly transmitted the virus to naive contacts. Collectively, these findings indicate that HA stalk-specific antibodies are commonly elicited in ferrets following sequential infection with antigenically distinct sH1N1 influenza virus isolates lacking HA receptor-binding site cross-reactivity and can protect ferrets against a pathogenic novel H1N1 virus. IMPORTANCE The influenza virus hemagglutinin (HA) is a major target of the humoral immune response following infection and The influenza virus is highly contagious and causes an acute respiratory illness, with seasonal epidemics in the human population. Despite global vaccination efforts, influenza remains a major medical issue and is responsible for substantial morbidity and mortality annually. It is estimated that 5 to 20% of the people in the United States contract influenza virus annually, and more than 200,000 people require hospitalization due to influenza-related complications (according to the Centers for Disease Control and Prevention, Atlanta, GA [http://www.cdc.gov/flu/about/qa /disease.htm; accessed 1 September 2015]). The young, the elderly, pregnant females, and those with certain medical conditions are at an increased risk for influenza-associated complications.Current vaccination approaches primarily rely on the induction of antibodies recognizing hemagglutinin (HA) (1). The HA glycoprotein is expressed as a trimeric complex of identical subunits on the surface of influenza virus virions. HA mediates virus attachment and subsequent membrane fusion with target cells (2, 3). Individual HA monomers can be further segregated into the membrane-distal globular head and membrane-proximal stalk domains. The globular head encodes the receptor-binding site (RBS), and the stalk domain encodes the fusion peptide (2).Antibodies directed against HA and, more specifically, to epitopes in close proximity to the RBS within the globular head region are elicited following infection or vaccination (4). These antibodies possess a potent neutralization capacity through the ability to interfere with viral attachment to target cells and a...

“…Membrane fusion assays using HA-transfected cells (23) or fluorescently labeled viruses (24) would better assess the fusion competency of the HA 3 -SS. Recently, many groups have been creating "headless" HA constructs to focus bnAb elicitation against the highly conserved stem (25)(26)(27)(28)(29)(30). However, since the stem domain can spontaneously adopt the postfusion conformation in the absence of the HA head (31), removal of the head component may impact the integrity of some of these immunogens.…”

mentioning

confidence: 99%

Design and Structure of an Engineered Disulfide-Stabilized Influenza Virus Hemagglutinin Trimer

Lee

Zhu

et al. 2015

We engineered a disulfide-stabilized influenza virus hemagglutinin (HA) trimer, termed HA 3 -SS, by introducing cysteine residues into the HA stem to covalently bridge the three protomers. HA 3 -SS has increased thermostability compared to wild-type HA, and binding of head-and stem-targeted antibodies (Abs) is preserved; only minor structural changes are found in the vicinity of the additional disulfide. This platform has been applied to H1 and H3 HAs and provides prospects for design of intact, stabilized influenza virus HA immunogens. Influenza viruses cause significant and unpredictable human disease on an annual basis. To combat seasonal infections, vaccination remains the best countermeasure. However, due to continual antigenic drift of circulating viruses, the vaccine formulations require nearly annual updates to match the circulating strains that are predicted to infect humans that year. The vaccines are composed of a combination (tri-or tetravalent) of different subtypes and types of the influenza virus hemagglutinin (HA) surface glycoprotein, which is the primary target of the adaptive immune response. Recent discoveries of broadly neutralizing antibodies (bnAbs) against the HA have advanced knowledge in the field and have provided renewed optimism for discovery of a universal influenza vaccine (reviewed in references 1 and 2).The HA is a type I fusion glycoprotein and is the major surface glycoprotein on influenza viruses (3). It is synthesized as a single polypeptide precursor protein (HA0), and three copies assemble into a noncovalent trimer. Host proteases cleave HA0 to generate the mature prefusion HA (HA1 or HA2), which is sensitive to low pH and hence metastable. The globular HA "head" is composed of HA1 residues and contains the receptor binding sites, whereas the helical HA "stem" that houses the fusion machinery is made up of HA2 and some HA1 residues. The HA contains six intraprotomer disulfide bonds, which include four HA1-HA1, one HA2-HA2, and one HA1-HA2 linkages (Fig. 1A).The HA from the 2009 H1N1 pandemic strain has a propensity to dissociate into monomers (4-6), and this instability has been linked with subpar immune response in vaccines (7). As such, creating a more stable, trimeric HA immunogen may enhance elicitation of a protective antibody response. This notion has been demonstrated for the respiratory syncytial virus (RSV) viral glycoprotein, where a combination of cavity-filling mutations and an introduced disulfide stabilized its prefusion antigenic structure (8). In addition, human immunodeficiency virus type 1 (HIV-1) Env glycoprotein prefusion trimers have been successfully engineered, through addition of a disulfide between gp120 and gp41, and properly display neutralizing epitopes, thereby giving promise as vaccine candidates (9). Disulfides have also been incorporated into the measles F glycoprotein and inhibit its fusion activity (10). Dissociation of the influenza virus HA protomers has also been remedied by introducing disulfides on the HA head (6). Here, we report an H...