Modified vaccinia virus Ankara encoding influenza virus hemagglutinin induces heterosubtypic immunity in macaques.

UNLABELLED: Current influenza virus vaccines primarily aim to induce neutralizing antibodies (NAbs). Modified vaccinia virus Ankara (MVA) is a safe and well-characterized vector for inducing both antibody and cellular immunity. We evaluated the immunogenicity and protective efficacy of MVA encoding influenza virus hemagglutinin (HA) and/or nucleoprotein (NP) in cynomolgus macaques. Animals were given 2 doses of MVA-based vaccines 4 weeks apart and were challenged with a 2009 pandemic H1N1 isolate (H1N1pdm) 8 weeks after the last vaccination. MVA-based vaccines encoding HA induced potent serum antibody responses against homologous H1 or H5 HAs but did not stimulate strong T cell responses prior to challenge. However, animals that received MVA encoding influenza virus HA and/or NP had high frequencies of virus-specific CD4(+) and CD8(+) T cell responses within the first 7 days of H1N1pdm infection, while animals vaccinated with MVA encoding irrelevant antigens did not. We detected little or no H1N1pdm replication in animals that received vaccines encoding H1 (homologous) HA, while a vaccine encoding NP from an H5N1 isolate afforded no protection. Surprisingly, H1N1pdm viral shedding was reduced in animals vaccinated with MVA encoding HA and NP from an H5N1 isolate. This reduced shedding was associated with cross-reactive antibodies capable of mediating antibody-dependent cellular cytotoxicity (ADCC) effector functions. Our results suggest that ADCC plays a role in cross-protective immunity against influenza. Vaccines optimized to stimulate cross-reactive antibodies with ADCC function may provide an important measure of protection against emerging influenza viruses when NAbs are ineffective. IMPORTANCE: Current influenza vaccines are designed to elicit neutralizing antibodies (NAbs). Vaccine-induced NAbs typically are effective but highly specific for particular virus strains. Consequently, current vaccines are poorly suited for preventing the spread of newly emerging pandemic viruses. Therefore, we evaluated a vaccine strategy designed to induce both antibody and T cell responses, which may provide more broadly cross-protective immunity against influenza. Here, we show in a translational primate model that vaccination with a modified vaccinia virus Ankara encoding hemagglutinin from a heterosubtypic H5N1 virus was associated with reduced shedding of a pandemic H1N1 virus challenge, while vaccination with MVA encoding nucleoprotein, an internal viral protein, was not. Unexpectedly, this reduced shedding was associated with nonneutralizing antibodies that bound H1 hemagglutinin and activated natural killer cells. Therefore, antibody-dependent cellular cytotoxicity (ADCC) may play a role in cross-protective immunity to influenza virus. Vaccines that stimulate ADCC antibodies may enhance protection against pandemic influenza virus.

A rapid immunization strategy with a live-attenuated tetravalent dengue vaccine elicits protective neutralizing antibody responses in non-human primates.

Dengue viruses (DENVs) cause approximately 390 million cases of DENV infections annually and over 3 billion people worldwide are at risk of infection. No dengue vaccine is currently available nor is there an antiviral therapy for DENV infections. We have developed a tetravalent live-attenuated DENV vaccine tetravalent dengue vaccine (TDV) that consists of a molecularly characterized attenuated DENV-2 strain (TDV-2) and three chimeric viruses containing the pre-membrane and envelope genes of DENV-1, -3, and -4 expressed in the context of the TDV-2 genome. To impact dengue vaccine delivery in endemic areas and immunize travelers, a simple and rapid immunization strategy (RIS) is preferred. We investigated RIS consisting of two full vaccine doses being administered subcutaneously or intradermally on the initial vaccination visit (day 0) at two different anatomical locations with a needle-free disposable syringe jet injection delivery devices (PharmaJet) in non-human primates. This vaccination strategy resulted in efficient priming and induction of neutralizing antibody responses to all four DENV serotypes comparable to those elicited by the traditional prime and boost (2 months later) vaccination schedule. In addition, the vaccine induced CD4(+) and CD8(+) T cells producing IFN-γ, IL-2, and TNF-α, and targeting the DENV-2 NS1, NS3, and NS5 proteins. Moreover, vaccine-specific T cells were cross-reactive with the non-structural NS3 and NS5 proteins of DENV-4. When animals were challenged with DENV-2 they were protected with no detectable viremia, and exhibited sterilizing immunity (no increase of neutralizing titers post-challenge). RIS could decrease vaccination visits and provide quick immune response to all four DENV serotypes. This strategy could increase vaccination compliance and would be especially advantageous for travelers into endemic areas.

Preclinical evaluation of the immunogenicity and safety of an inactivated enterovirus 71 candidate vaccine.

Human enterovirus 71 (EV71) is a significant cause of morbidity and mortality from Hand, Foot and Mouth Disease (HFMD) and neurological complications, particularly in young children in the Asia-Pacific region. There are no vaccines or antiviral therapies currently available for prevention or treatment of HFMD caused by EV71. Therefore, the development of therapeutic and preventive strategies against HFMD is of growing importance. We report the immunogenic and safety profile of inactivated, purified EV71 preparations formulated with aluminum hydroxide adjuvant in preclinical studies in mice and rabbits. In mice, the candidate vaccine formulations elicited high neutralizing antibody responses. A toxicology study of the vaccine formulations planned for human use performed in rabbits showed no vaccine-related pathological changes and all animals remained healthy. Based on these preclinical studies, Phase 1 clinical testing of the EV71 inactivated vaccine was initiated.

Cross-protective immunity against multiple influenza virus subtypes by a novel modified vaccinia Ankara (MVA) vectored vaccine in mice.

Development of an influenza vaccine that provides cross-protective immunity remains a challenge. Candidate vaccines based on a recombinant modified vaccinia Ankara (MVA) viral vector expressing antigens from influenza (MVA/Flu) viruses were constructed. A vaccine candidate, designated MVA/HA1/C13L/NP, that expresses the hemagglutinin from pandemic H1N1 (A/California/04/09) and the nucleoprotein (NP) from highly pathogenic H5N1 (A/Vietnam/1203/04) fused to a secretory signal sequence from vaccinia virus was highly protective. The vaccine elicited strong antibody titers to homologous H1N1 viruses while cross-reactive antibodies to heterologous viruses were not detectable. In mice, this MVA/HA1/C13L/NP vaccine conferred complete protection against lethal challenge with A/Vietnam/1203/04 (H5N1), A/Norway/3487-2/09 (pandemic H1N1) or A/Influenza/Puerto Rico/8/34 (seasonal H1N1) and partial protection (57.1%) against challenge with seasonal H3N2 virus (A/Aichi/68). The protective efficacy of the vaccine was not affected by pre-existing immunity to vaccinia. Our findings highlight MVA as suitable vector to express multiple influenza antigens that could afford broad cross-protective immunity against multiple subtypes of influenza virus.

Effects of route and coadministration of recombinant raccoon poxviruses on immune responses and protection against highly pathogenic avian influenza in mice.

We previously demonstrated that recombinant raccoonpox (RCN) virus could serve as a vector for an influenza vaccine. RCN constructs expressing the hemagglutinin (HA) from H5N1 viruses were immunogenic in chickens. In the current study, we generated several recombinant RCN constructs expressing influenza (H5N1) antigens and a molecular adjuvant (Heat-Labile enterotoxin B from E. coli: RCN-LTB), demonstrated their expression in vitro, and evaluated their ability to protect mice against H5N1 virus challenge. RCN-HA provided strong protection when administered intradermally (ID), but not intranasally (IN). Conversely, the RCN-neuraminidase (NA) construct was highly efficacious by the IN route and elicited high titers of neutralizing antibodies in mice. Vaccination by combined ID (RCN-HA) and IN (RCN-NA) routes offered mice the best protection against an IN challenge with heterologous H5N1 virus. However, protection was reduced when the different RCN constructs were pre-mixed, perhaps due to reduced expression of antigen.

Immunogenicity and efficacy of chimeric dengue vaccine (DENVax) formulations in interferon-deficient AG129 mice.

Formulations of chimeric dengue vaccine (DENVax) viruses containing the pre-membrane (prM) and envelope (E) genes of serotypes 1-4 expressed in the context of the attenuated DENV-2 PDK-53 genome were tested for safety, immunogenicity and efficacy in interferon receptor knock-out mice (AG129). Monovalent formulations were safe and elicited robust neutralizing antibody responses to the homologous virus and only limited cross-reactivity to other serotypes. A single dose of monovalent DENVax-1, -2, or -3 vaccine provided eighty or greater percent protection against both wild-type (wt) DENV-1 (Mochizuki strain) and DENV-2 (New Guinea C strain) challenge viruses. A single dose of monovalent DENVax-4 also provided complete protection against wt DENV-1 challenge and significantly increased the survival times after challenge with wt DENV-2. In studies using tetravalent mixtures, DENVax ratios were identified that: (i) caused limited viremia, (ii) induced serotype-specific neutralizing antibodies to all four DENV serotypes with different hierarchies, and (iii) conferred full protection against clinical signs of disease following challenge with either wt DENV-1 or DENV-2 viruses. Overall, these data highlight the immunogenic profile of DENVax, a novel candidate tetravalent dengue vaccine and the advantage of sharing a common attenuated genomic backbone among the DENVax monovalent vaccines that confer protection against homologous or heterologous virus challenge.

Dengue virus-specific CD4+ and CD8+ T lymphocytes target NS1, NS3 and NS5 in infected Indian rhesus macaques.

Every year, Dengue virus (DENV) infects approximately 100 million people. There are currently several vaccines undergoing clinical studies, but most target the induction of neutralizing antibodies. Unfortunately, DENV infection can be enhanced by subneutralizing levels of antibodies that bind virions and deliver them to cells of the myeloid lineage, thereby increasing viral replication (termed antibody-dependent enhancement [ADE]). T lymphocyte-based vaccines may offer an alternative that avoids ADE. The goal of our study was to describe the cellular immune response generated after primary DENV infection in Indian rhesus macaques. We infected eight rhesus macaques with 105 plaque-forming units (PFU) of DENV serotype 2 (DENV2) New Guinea C (NGC) strain, and monitored viral load and the cellular immune response to the virus. Viral replication peaked at day 4 post-infection and was resolved by day 10. DENV-specific CD4+ and CD8+ T lymphocytes targeted nonstructural (NS) 1, NS3 and NS5 proteins after resolution of peak viremia. DENV-specific CD4+ cells expressed interferon-gamma (IFN-γ) along with tumor necrosis factor-alpha (TNF-α), interleukin-2 (IL-2), and macrophage inflammatory protein-1 beta (MIP-1ß). In comparison, DENV-specific CD8+ cells expressed IFN-γ in addition to MIP-1ß and TNF-α and were positive for the degranulation marker CD107a. Interestingly, a fraction of the DENV-specific CD4+ cells also stained for CD107a, suggesting that they might be cytotoxic. Our results provide a more complete understanding of the cellular immune response during DENV infection in rhesus macaques and contribute to the development of rhesus macaques as an animal model for DENV vaccine and pathogenicity studies.

Efficacy of a tetravalent chimeric dengue vaccine (DENVax) in Cynomolgus macaques.

Three tetravalent formulations of chimeric dengue (DENVax) viruses containing the pre-membrane and envelope genes of serotypes 1-4 expressed by the attenuated DENV-2 PDK-53 genome were tested for safety, immunogenicity, and efficacy in cynomolgus macaques (Macaca fascicularis). Subcutaneous injection of the DENVax formulations was well-tolerated. Low levels of viremia of only one of the four vaccine viruses were detected yet virus neutralizing antibody titers were induced against all four dengue virus serotypes after one or two administrations of vaccine. All animals immunized with the high-dose formulation were protected from viremia, and all immunized animals were completely protected from DENV-3 and DENV-4 challenge. A lower dose of DENVax formulation partially protected animals from DENV-1 or DENV-2 challenge. In contrast, all control animals developed high levels of viremia for multiple days after challenge with DENV 1-4. This study highlights the immunogenicity and efficacy of the tetravalent DENVax formulations in nonhuman primates.

Efficacy and safety of a modified vaccinia Ankara (MVA) vectored plague vaccine in mice.

The efficacy and safety of plague vaccines based on the modified vaccinia Ankara (MVA) viral vector was evaluated. MVA recombinants were constructed expressing Yersinia pestis antigens under the translational control of the encephalomyocarditis virus (EMCV) internal ribosomal entry site (IRES) and/or fused to the tissue plasminogen activator (tPA) secretory signal. A MVA/Y. pestis recombinant that expressed a truncated version of the low-calcium response V antigen (MVA/IRES/tPA/V(307)), conferred significant protection (87.5-100%) against intranasal or intraperitoneal challenge with CO92 (encapsulated) or Java 9 (non-encapsulated) strains of Y. pestis, respectively. In contrast, a MVA/Y. pestis recombinant that expressed the full-length V antigen provided only 37.5% protection against challenge with CO92 or Java 9 strains, respectively. Interestingly, a MVA/Y. pestis recombinant that expressed the capsular protein (F1) did not elicit significant antibody titers but still conferred 50% and 25% protection against CO92 or Java 9 challenge, respectively. The MVA/Y. pestis recombinant viruses did not demonstrate any mortality or morbidity in SCID mice. Based on their safety and efficacy in mice, these MVA/Y. pestis recombinants are candidates for further development as biodefense and public health vaccines.

Leukocyte profile of cattle persistently infected with bovine viral diarrhea virus.

Animals acutely infected with bovine viral diarrhea virus (BVDV) exhibit transient immunosuppression as a result of the virus' predilection for cells that play critical roles in the host immune system. Acute BVDV infections have major effects on thymic and follicular T-lymphocytes, as well as follicular B-lymphocytes, often resulting in severe reduction in circulating numbers of lymphocytes and suppression of functional activities of these cells. Granulocytes and monocytes are equally susceptible to BVDV infections with reduction in numbers and suppression functions. However, there is limited information on the leukocyte profile of cattle persistently infected (PI) with BVDV. This study reports on phagocytic activities of granulocytes and monocytes as well as immunophenotyping by flow cytometric analysis of leukocytes isolated from healthy non-PI (NPI) and PI animals. No significant differences were found between the leukocyte profiles and the phagocytic activities of PI animals when compared to a group of healthy NPI animals.