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Influenza A viruses with truncated NS1 as modified live virus vaccines: pilot studies of safety and efficacy in horses.

ABSTRACT: REASONS FOR PERFORMING STUDY:Three previously described NS1 mutant equine influenza viruses encoding carboxy-terminally truncated NS1 proteins are impaired in their ability to inhibit type I IFN production in vitro and are replication attenuated, and thus are candidates for use as a modified live influenza virus vaccine in the horse. HYPOTHESIS:One or more of these mutant viruses is safe when administered to horses, and recipient horses when challenged with wild-type influenza have reduced physiological and virological correlates of disease. METHODS:Vaccination and challenge studies were done in horses, with measurement of pyrexia, clinical signs, virus shedding and systemic proinflammatory cytokines. RESULTS:Aerosol or intranasal inoculation of horses with the viruses produced no adverse effects. Seronegative horses inoculated with the NS1-73 and NS1-126 viruses, but not the NS1-99 virus, shed detectable virus and generated significant levels of antibodies. Following challenge with wild-type influenza, horses vaccinated with NS1-126 virus did not develop fever (>38.5 degrees C), had significantly fewer clinical signs of illness and significantly reduced quantities of virus excreted for a shorter duration post challenge compared to unvaccinated controls. Mean levels of proinflammatory cytokines IL-1beta and IL-6 were significantly higher in control animals, and were positively correlated with peak viral shedding and pyrexia on Day +2 post challenge. CONCLUSION AND CLINICAL RELEVANCE:These data suggest that the recombinant NS1 viruses are safe and effective as modified live virus vaccines against equine influenza. This type of reverse genetics-based vaccine can be easily updated by exchanging viral surface antigens to combat the problem of antigenic drift in influenza viruses.

SUBMITTER: Chambers TM

PROVIDER: S-EPMC2878972 | biostudies-literature | 2009 Jan

REPOSITORIES: biostudies-literature

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Influenza A viruses with truncated NS1 as modified live virus vaccines: pilot studies of safety and efficacy in horses.

Chambers T M TM Quinlivan M M Sturgill T T Cullinane A A Horohov D W DW Zamarin D D Arkins S S García-Sastre A A Palese P P

Equine veterinary journal 20090101 1

<h4>Reasons for performing study</h4>Three previously described NS1 mutant equine influenza viruses encoding carboxy-terminally truncated NS1 proteins are impaired in their ability to inhibit type I IFN production in vitro and are replication attenuated, and thus are candidates for use as a modified live influenza virus vaccine in the horse.<h4>Hypothesis</h4>One or more of these mutant viruses is safe when administered to horses, and recipient horses when challenged with wild-type influenza hav ...[more]

PMID: 19301588

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Project description:Nonstructural protein 1 (NS1) of influenza virus is a key virulence element with multifunctional roles in virus replication and a potent antagonist of host immune response. Deletion of NS1 (DelNS1) would create a safer and more extensively immunogenic live attenuated influenza virus (LAIV) vaccine. However, DelNS1 viruses are very difficult to grow in regular vaccine-producing systems, which has hampered the application of DelNS1 LAIV vaccines in humans. We have developed two master backbones of deleted-NS1 (DelNS1) viral genomes from influenza A or B viruses which contain novel adaptive mutations to support DelNS1-LAIV replication. These DelNS1-LAIVs are highly attenuated in human cells in vitro and nonpathogenic in mice but replicate well in vaccine-producing cells. Both influenza A and influenza B DelNS1 LAIVs grow better at 33°C than at 37 to 39°C. Vaccination with DelNS1 LAIV performed once is enough to provide potent protection against lethal challenge with homologous virus and strong long-lasting cross protection against heterosubtypic or antigenically distantly related influenza viruses in mice. Mechanistic investigations revealed that DelNS1-LAIVs induce cross protective neutralizing antibody and CD8+ and CD4+ T cell immunities. Importantly, it has been shown that DelNS1-LAIV can be used to enhance specific anti-influenza immunity through expression of additional antigens from the deleted-NS1 site. Generation of DelNS1 viruses which are nonpathogenic and able to grow in vaccine-producing systems is an important strategy for making highly immunogenic LAIV vaccines that induce broad cross protective immunity against seasonal and emerging influenza.IMPORTANCE Current seasonal influenza vaccines are suboptimal and low in immunogenicity and do not provide long-lasting immunity and cross protection against influenza virus strains that have antigenically drifted. More-effective influenza vaccines which can induce both humoral immunity and T cell immunity are needed. The NS1 protein of influenza virus is a virulence element and the critical factor for regulation of the host immune response during virus infection. Deletion of the NS1 protein is a strategy to make an optimal LAIV vaccine. However, DelNS1 viruses are very difficult to grow in regular vaccine-producing systems, hampering the application of DelNS1 LAIV vaccines in humans. We have generated a panel of both influenza A and influenza B DelNS1 LAIVs which are able to grow in regular vaccine-producing cells. These DelNS1 LAIV vaccines are completely nonpathogenic, exhibit potent and long-lasting immunity, and can be used to express extra viral antigen to induce cross protective immunity against seasonal and emerging influenza.

Project description:Mutants of influenza virus that encode C-terminally truncated NS1 proteins (NS1-truncated mutants) characteristically induce high interferon responses. The dual activity of interferon in blocking virus replication and enhancing the development of adaptive immune responses makes these mutants promising as self-adjuvanting live-attenuated influenza vaccine (LAIV) candidates. Yet, among the NS1-truncated mutants, the length of NS1 is not directly correlated with the interferon-inducing efficiency, the level of attenuation, or effectiveness as LAIV. Using quantitative in vitro biologically active particle subpopulation analysis as a tool to identify potential LAIV candidates from a pool of NS1-truncated mutants, we previously predicted that a NS1-truncated mutant pc2, which was less effective as a LAIV in chickens, would be sufficiently effective as a LAIV in mammalian hosts. In this study, we confirmed that pc2 protected mice and pigs against heterologous virus challenge in terms of preventing clinical signs and reducing virus shedding. pc2 expresses a unique SLSYSINWRH motif at the C-terminus of its truncated NS1. Deletion of the SLSYSINWRH motif led to ~821-fold reduction in the peak yield of type I interferon induced in murine cells. Furthermore, replacement of the SLSYSINWRH motif with the wildtype MVKMDQAIMD sequence did not restore the interferon-inducing efficiency. The diminished interferon induction capacity in the absence of the SLSYSINWRH motif was similar to that observed in other mutants which are less effective LAIV candidates. Remarkably, pc2 induced 16-fold or more interferon in human lung and monkey kidney cells compared to the temperature-sensitive, cold-adapted Ann Arbor virus that is currently used as a master backbone for LAIVs such as FluMist. Although the mechanism by which the SLSYSINWRH motif regulates the vaccine properties of pc2 has not been elucidated, this motif has potential use in engineering self-adjuvanting NS1-truncated-based LAIVs.

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Project description:Influenza B virus (FLUBV) is a major respiratory pathogen of humans. Seasonal influenza vaccines include either one or both FLUBV lineage strains, Victoria, and Yamagata. Vaccine mismatch occurs frequently, particularly in countries where vaccines contain only one of the lineages. We have previously described the safety and efficacy of modified live attenuated FLUBV vaccines based on either virus with rearranged genomes (FluB-RAM and FluB-RANS) or carrying a PB1 segment with a combination of temperature sensitive mutations and a C-terminal HA tag (FluB-att). We compared side by side the immunological responses in female and male DBA/2J mice vaccinated with either one of these vaccines and those with isogenic backgrounds encoding a chimeric HA segment carrying an N-terminal peptide encoding the IgA inducing peptide (IGIP). Recombinant viruses with or without the IGIP modification were genetically stable over multiple passages in eggs. In mice, introduction of IGIP improved attenuation of the vaccine candidates, particularly for the FluB-RAM/IGIP compared with the non-IGIP FluB-RAM counterpart. In a prime-boost regime, mice were completely protected against lethal challenge with a homologous FLUBV strain. Recombinant viruses induced antibodies against HA considered of protective value. Antibodies against NA and NP were readily detected. Compared to male mice and regardless of the vaccine used, female mice showed a clear trend towards enhanced humoral and cross-reactive IgG and IgA anti-HA responses as well as against NA and NP. The presence of IGIP in the vaccine resulted in an overall trend towards reduced anti-HA responses but enhanced anti-NA and anti-NP responses, particularly of the IgA isotype. Mucosal and serological responses two weeks after challenge showed similar trends with clear differences observed based on sex, vaccine backbone, and whether the vaccine carried the IGIP modification. These findings are significant for the development of universal influenza vaccines.

Dataset Information

Influenza A viruses with truncated NS1 as modified live virus vaccines: pilot studies of safety and efficacy in horses.

Publications

Influenza A viruses with truncated NS1 as modified live virus vaccines: pilot studies of safety and efficacy in horses.

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