A Whole Virus Pandemic Influenza H1N1 Vaccine Is Highly Immunogenic and Protective in Active Immunization and Passive Protection Mouse Models

The recent emergence and rapid spread of a novel swine-derived H1N1 influenza virus has resulted in the first influenza pandemic of this century. Monovalent vaccines have undergone preclinical and clinical development prior to initiation of mass immunization campaigns. We have carried out a series of immunogenicity and protection studies following active immunization of mice, which indicate that a whole virus, nonadjuvanted vaccine is immunogenic at low doses and protects against live virus challenge. The immunogenicity in this model was comparable to that of a whole virus H5N1 vaccine, which had previously been demonstrated to induce high levels of seroprotection in clinical studies. The efficacy of the H1N1 pandemic vaccine in protecting against live virus challenge was also seen to be equivalent to that of the H5N1 vaccine. The protective efficacy of the H1N1 vaccine was also confirmed using a severe combined immunodeficient (SCID) mouse model. It was demonstrated that mouse and guinea pig immune sera elicited following active H1N1 vaccination resulted in 100% protection of SCID mice following passive transfer of immune sera and lethal challenge. The immune responses to a whole virus pandemic H1N1 and a split seasonal H1N1 vaccine were also compared in this study. It was demonstrated that the whole virus vaccine induced a balanced Th-1 and Th-2 response in mice, whereas the split vaccine induced mainly a Th-2 response and only minimal levels of Th-1 responses. These data supported the initiation of clinical studies with the same low doses of whole virus vaccine that had previously been demonstrated to be immunogenic in clinical studies with a whole virus H5N1 vaccine

A Pandemic Influenza H1N1 Live Vaccine Based on Modified Vaccinia Ankara Is Highly Immunogenic and Protects Mice in Active and Passive Immunizations

The development of novel influenza vaccines inducing a broad immune response is an important objective. The aim of this study was to evaluate live vaccines which induce both strong humoral and cell-mediated immune responses against the novel human pandemic H1N1 influenza virus, and to show protection in a lethal animal challenge model.For this purpose, the hemagglutinin (HA) and neuraminidase (NA) genes of the influenza A/California/07/2009 (H1N1) strain (CA/07) were inserted into the replication-deficient modified vaccinia Ankara (MVA) virus - a safe poxviral live vector – resulting in MVA-H1-Ca and MVA-N1-Ca vectors. These live vaccines, together with an inactivated whole virus vaccine, were assessed in a lung infection model using immune competent Balb/c mice, and in a lethal challenge model using severe combined immunodeficient (SCID) mice after passive serum transfer from immunized mice. Balb/c mice vaccinated with the MVA-H1-Ca virus or the inactivated vaccine were fully protected from lung infection after challenge with the influenza H1N1 wild-type strain, while the neuraminidase virus MVA-N1-Ca induced only partial protection. The live vaccines were already protective after a single dose and induced substantial amounts of neutralizing antibodies and of interferon-γ-secreting (IFN-γ) CD4- and CD8 T-cells in lungs and spleens. In the lungs, a rapid increase of HA-specific CD4- and CD8 T cells was observed in vaccinated mice shortly after challenge with influenza swine flu virus, which probably contributes to the strong inhibition of pulmonary viral replication observed. In addition, passive transfer of antisera raised in MVA-H1-Ca vaccinated immune-competent mice protected SCID mice from lethal challenge with the CA/07 wild-type virus.The non-replicating MVA-based H1N1 live vaccines induce a broad protective immune response and are promising vaccine candidates for pandemic influenza

Immunogenicity and protective efficacy of a Vero cell culture-derived whole-virus H7N9 vaccine in mice and guinea pigs.

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

Protection of mice from lung viremia and serology results after <b>two</b> vaccinations.

(1)<p>hemagglutinin-inhibition titer determined with chicken erythrocytes;</p>(2)<p>geometric mean titer;</p>(3)<p>microneutralization assay (cpe-based);</p>(4)<p>neuraminidase-inhibition titer;</p>(5)<p>two separate experiments with 6 animals per group were performed;</p>(6)<p>inactivated whole virus vaccine, subcutaneous application route;</p>(7)<p>wild-type MVA (NIH74 LVD clone 6);</p>(8)<p>wild-type vaccinia Lister strain;</p>(9)<p>the dectection limit (dl) is <10;</p

HA and NA antibody responses induced by H7N9 and H1N1pdm09 vaccines in DBA/2J mice.

<p>^a20 animals per dose group for both vaccines.</p><p>^b10 animals per dose group for both vaccines.</p><p>^c20 animals per dose group for H7N9 vaccine; 10 animals per dose group for H1N1 pdm09 vaccine.</p><p>^dGeometric mean titer</p><p>^eSeroconversion (≥4-fold increase in antibody titer and antibody titer ≥ 1:40)</p><p>n.d., not done; n.a., not applicable.</p><p>HA and NA antibody responses induced by H7N9 and H1N1pdm09 vaccines in DBA/2J mice.</p

T cell induction by the hemagglutinin expressing live vaccines in the lungs.

<p>Frequencies of influenza antigen specific IFN-γ+ CD4 T-cells (<b>A, C</b>) and CD8 T-cells (<b>B, D</b>) after immunizing two times with hemagglutinin constructs MVA-H1-Ca (<b>A, B</b>) or rVVL-H1-Ca (<b>C, D</b>) and stimulation with hemagglutinin (H1/CA-PP) or neuraminidase (N1/CA-PP) peptide pools. Lung cells or spleen cells were isolated at days 28, 41 and 45. Animals were challenged with wild-type swine flu virus on day 42, as indicated by the arrow. The filled (open) circles indicate lung (spleen) cells stimulated with the hemagglutinin peptide pool H1/CA PP. The filled (open) triangles indicate lung (spleen) cells stimulated with the neuraminidase peptide pool used as negative controls. Representative results of two independent experiments are shown.</p

Dose-dependent protection against disease symptoms and death in H7N9-challenged DBA/2J mice immunized with whole-virus H7N9 vaccine.

<p>(A) Kaplan-Meier survival curves, (B) Severity and duration of disease symptoms</p

Lung titers in Balb/c mice.

<p>The dots represent the lung titers of individual mice vaccinated with the different experimental vaccines or control preparations. Mice vaccinated with the controls (PBS, wild-type MVA (MVA wt) or Lister (VV-L wt) were not protected showing average log10 TCID50 titers of 5.2, 4.9 and 5.4, respectively. Mice vaccinated with inactivated vaccine (inact. H1N1), or two different doses (10⁶, 10⁷ pfu) of MVA-H1-Ca or rVVL-H1-Ca were close to or fully protected. Partial protection was achieved with two dosages of the MVA neuraminidase viruses (MVA-N1-Ca), while full protection was seen with the Lister-based neuraminidase virus (rVVL-N1-Ca). The dotted line represents the detection limit of log₁₀ 2.21. Low titers in range of log10<2.21 to 3.0 were confirmed by a passage assay of the lung samples in MDCK cells.</p