Design and Characterization of a Computationally Optimized Broadly Reactive Hemagglutinin Vaccine for H1N1 Influenza Viruses.

UNLABELLED: One of the challenges of developing influenza A vaccines is the diversity of antigenically distinct isolates. Previously, a novel hemagglutinin (HA) for H5N1 influenza was derived from a methodology termed computationally optimized broadly reactive antigen (COBRA). This COBRA HA elicited a broad antibody response against H5N1 isolates from different clades. We now report the development and characterization of a COBRA-based vaccine for both seasonal and pandemic H1N1 influenza virus isolates. Nine prototype H1N1 COBRA HA proteins were developed and tested in mice using a virus-like particle (VLP) format for the elicitation of broadly reactive, functional antibody responses and protection against viral challenge. These candidates were designed to recognize H1N1 viruses isolated within the last 30 years. In addition, several COBRA candidates were designed based on sequences of H1N1 viruses spanning the past 100 years, including modern pandemic H1N1 isolates. Four of the 9 H1N1 COBRA HA proteins (X1, X3, X6, and P1) had the broadest hemagglutination inhibition (HAI) activity against a panel of 17 H1N1 viruses. These vaccines were used in cocktails or prime-boost combinations. The most effective regimens that both elicited the broadest HAI response and protected mice against a pandemic H1N1 challenge were vaccines that contained the P1 COBRA VLP and either the X3 or X6 COBRA VLP vaccine. These mice had little or no detectable viral replication, comparable to that observed with a matched licensed vaccine. This is the first report describing a COBRA-based HA vaccine strategy that elicits a universal, broadly reactive, protective response against seasonal and pandemic H1N1 isolates. IMPORTANCE: Universal influenza vaccine approaches have the potential to be paradigm shifting for the influenza vaccine field, with the goal of replacing the current standard of care with broadly cross-protective vaccines. We have used COBRA technology to develop an HA head-based strategy that elicits antibodies against many H1 strains that have undergone genetic drift and has potential as a "subtype universal" vaccine. Nine HA COBRA candidates were developed, and these vaccines were used alone, in cocktails or in prime-boost combinations. The most effective regimens elicited the broadest hemagglutination inhibition (HAI) response against a panel of H1N1 viruses isolated over the past 100 years. This is the first report describing a COBRA-based HA vaccine strategy that elicits a broadly reactive response against seasonal and pandemic H1N1 isolates.

Intanza(®) 15 mcg intradermal influenza vaccine elicits cross-reactive antibody responses against heterologous A(H3N2) influenza viruses.

The aim of the present study was to explore the ability of Intanza(®) 15 µg, the intradermal (ID) trivalent inactivated split-virion influenza vaccine containing 15 µg hemagglutinin per strain, to enhance the antibody responses against heterologous circulating H3N2 strains in adults 60 years and older. During the 2006-2007 influenza season, subjects aged 60 years or older were randomly assigned to receive one dose of ID or an intramuscular (IM, Vaxigrip(®)) influenza vaccine, which contained the reassortant A/Wisconsin/67/05(H3N2) strain as the H3N2 component. Antibody responses were assessed against the homologous vaccine strain, against the A/Brisbane/10/07(H3N2) reassortant strain and against four heterologous H3N2 field isolates (A/Genoa/62/05(H3N2), A/Genoa/3/07(H3N2), A/Genoa/2/07(H3N2), A/Genoa/3/06(H3N2)). The viruses tested belonged to three different clades that were closely related antigenically to A/California/7/04(H3N2), A/Nepal/921/06(H3N2) and A/Brisbane/10/07(H3N2). Antibody responses to these viruses were measured in 25 subjects per group using both haemagglutination inhibition (HI) and neutralization (NT) assays. At least one Committee for Medicinal Products for Human Use (CHMP) immunogenicity criteria for vaccine approval in the elderly was reached by both vaccines against all the viruses used in the study. All three CHMP criteria were reached against A/California/7/04(H3N2)-like, A/Nepal/921/06(H3N2)-like and A/Brisbane/10/07(H3N2)-like viruses by Intanza(®) 15 µg ID vaccine, while IM vaccination did not meet seroprotection criteria against circulating A/Nepal/921/06(H3N2)-like and A/Brisbane/10/07(H3N2)-like viruses or seroconversion criteria against A/Brisbane/10/07(H3N2)-like viruses. Post-vaccination HI titer, seroconversion, and seroprotection rates were higher against all viruses in subjects who received Intanza(®) 15 µg. The superiority of the seroprotection rate against the A/Nepal/921/06(H3N2)-like strain attained statistical significance despite the small sample size. Upon Beyer correction for pre-vaccination status, post-immunization HI titers against A/California/7/04(H3N2)-like and A/Brisbane/10/07(H3N2)-like strains and NT post-immunization titers against A/Wisconsin/67/05(H3N2), A/California/7/04(H3N2)-like, A/Brisbane/10/07(H3N2)-like strains were significantly higher in subjects immunized with Intanza(®) 15 µg than in individuals receiving IM vaccine. This study, although limited in the size of study population, demonstrated the broader immune response elicited by an ID influenza vaccine vs. a standard IM influenza vaccine against heterologous viruses including field isolates.

Structure-guided antigen engineering yields pneumolysin mutants suitable for vaccination against pneumococcal disease.

Pneumolysin (PLY) is a cholesterol-binding, pore-forming protein toxin. It is an important virulence factor of Streptococcus pneumoniae and a key vaccine target against pneumococcal disease. We report a systematic structure-driven approach that solves a long-standing problem for vaccine development in this field: detoxification of PLY with retention of its antigenic integrity. Using three conformational restraint techniques, we rationally designed variants of PLY that lack hemolytic activity and yet induce neutralizing antibodies against the wild-type toxin. These results represent a key milestone toward a broad-spectrum protein-based pneumococcal vaccine and illustrate the value of structural knowledge in formulating effective strategies for antigen optimization.