However, oseltamivir-resistant

viruses have been associated with antiviral treatment and poor clinical Imatinib mouse outcome [6] and [7]. The exceptional adaptive ability of the virus and the lack of human pre-immunity and of available vaccines underline the necessity of rapid measures to be taken and research on the development on human H7 vaccines is underway [8], [9], [10], [11], [12], [13] and [14]. Here, we assess the efficacy of a single low vaccine dose of influenza A H7 virus-like particles (VLPs) of Avian Influenza A (H7N9) virus origin to protect against a stringent viral challenge in the mouse model. Two-component influenza virus-like particles, containing HAs from the first H7N9 virus isolates (A/Anhui/1/13 or A/Shanghai/1/13, respectively) and the

matrix protein (M1) from A/Udorn/307/1972, Dinaciclib concentration were produced in the Trichoplusia ni insect cell line High Five (BTI-TN-5B1-4) using the baculovirus expression system. Previous studies conclusively demonstrated the potent immune stimulating properties of live baculovirus in vaccine preparations [15] and [16]. Hence, in order to keep the by-product in the vaccine formulation, we concentrated the VLPs and residual baculovirus from the culture supernatant by one-step sucrose-cushion purification. Mice received one VLP vaccine dose containing different amounts of HA (3 μg, 0.3 μg and 0.03 μg) and 5 weeks later were challenged with a stringent viral dose (100 mLD50) of the A/Shanghai/1/13 H7N9 strain. Pre-challenge serum was evaluated for the breadth of reactivity and hemagglutination inhibition (HI) activity of the elicited humoral response to divergent H7 HAs, as well as representatives of all group 2 HA subtypes. Even the lowest tested vaccine doses conferred full protection against the stringent viral challenge. In addition, a single vaccination with the H7 VLP vaccine induced serum antibodies that

were broadly reactive and HI active against divergent H7 subtyped viruses. We also detected sero-reactivity to heterosubtypic members of the group 2 HAs, such as H15 and H3. Sf9 insect cells (ATCC # CRL-1711) were routinely propagated at 27 °C in TNM-FH medium (Gemini Bio-Products, West Sacramento, CA) supplemented with 0.1% (v/v) Pluronic 68 (Sigma, St. Louis, MO), 10% (v/v) foetal bovine serum (FBS) (Atlanta Biologicals, Norcross, GA) Ribonucleotide reductase and Penicillin–Streptomycin antibiotic mixture (Life Technologies, Carlsbad, CA). For baculovirus amplification, the medium was switched to 3% (v/v) FBS. BTI-TN-5B1-4 (High Five – Vienna Institute of Biotechnology subclone) [17] cells were used for expression of VLPs and maintained at 27 °C in custom modified serum-free IPL-41 medium (PAN-Biotech GmbH, Aidenbach, Germany) at 27 °C as described in [18] supplemented with Penicillin–Streptomycin antibiotic mixture. Recombinant influenza viruses were generated by reverse genetics as described before [19], [20] and [21].