Experimental vaccines against potentially pandemic and highly pathogenic avian influenza viruses
TL;DR: This review discusses advances in alternative influenza vaccines, touching briefly on licensed vaccines and vaccine antigens; then reviewing recombinant subunit vaccines, virus-like particle vaccines and DNA vaccines, with the main focus on virus-vectored vaccine approaches.
Abstract: Influenza A viruses continue to emerge and re-emerge, causing outbreaks, epidemics and occasionally pandemics. While the influenza vaccines licensed for public use are generally effective against seasonal influenza, issues arise with production, immunogenicity, and efficacy in the case of vaccines against pandemic and emerging influenza viruses, and highly pathogenic avian influenza virus in particular. Thus, there is need of improved influenza vaccines and vaccination strategies. This review discusses advances in alternative influenza vaccines, touching briefly on licensed vaccines and vaccine antigens; then reviewing recombinant subunit vaccines, virus-like particle vaccines and DNA vaccines, with the main focus on virus-vectored vaccine approaches.
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TL;DR: If the SAM vaccine platform proves safe, potent, well tolerated and effective in humans, fully synthetic vaccine technologies could provide unparalleled speed of response to stem the initial wave of influenza outbreaks, allowing first availability of a vaccine candidate days after the discovery of a new virus.
Abstract: The timing of vaccine availability is essential for an effective response to pandemic influenza. In 2009, vaccine became available after the disease peak, and this has motivated the development of next generation vaccine technologies for more rapid responses. The SAM(®) vaccine platform, now in pre-clinical development, is based on a synthetic, self-amplifying mRNA, delivered by a synthetic lipid nanoparticle (LNP). When used to express seasonal influenza hemagglutinin (HA), a SAM vaccine elicited potent immune responses, comparable to those elicited by a licensed influenza subunit vaccine preparation. When the sequences coding for the HA and neuraminidase (NA) genes from the H7N9 influenza outbreak in China were posted on a web-based data sharing system, the combination of rapid and accurate cell-free gene synthesis and SAM vaccine technology allowed the generation of a vaccine candidate in 8 days. Two weeks after the first immunization, mice had measurable hemagglutinin inhibition (HI) and neutralizing antibody titers against the new virus. Two weeks after the second immunization, all mice had HI titers considered protective. If the SAM vaccine platform proves safe, potent, well tolerated and effective in humans, fully synthetic vaccine technologies could provide unparalleled speed of response to stem the initial wave of influenza outbreaks, allowing first availability of a vaccine candidate days after the discovery of a new virus.
193 citations
TL;DR: This review will discuss experimental virus-vectored vaccines for use in humans, comparing them to licensed vaccines and the hurdles faced for licensure of these next-generation influenza virus vaccines.
Abstract: Despite the availability of an inactivated vaccine that has been licensed for >50 years, the influenza virus continues to cause morbidity and mortality worldwide. Constant evolution of circulating influenza virus strains and the emergence of new strains diminishes the effectiveness of annual vaccines that rely on a match with circulating influenza strains. Thus, there is a continued need for new, efficacious vaccines conferring cross-clade protection to avoid the need for biannual reformulation of seasonal influenza vaccines. Recombinant virus-vectored vaccines are an appealing alternative to classical inactivated vaccines because virus vectors enable native expression of influenza antigens, even from virulent influenza viruses, while expressed in the context of the vector that can improve immunogenicity. In addition, a vectored vaccine often enables delivery of the vaccine to sites of inductive immunity such as the respiratory tract enabling protection from influenza virus infection. Moreover, the ability to readily manipulate virus vectors to produce novel influenza vaccines may provide the quickest path toward a universal vaccine protecting against all influenza viruses. This review will discuss experimental virus-vectored vaccines for use in humans, comparing them to licensed vaccines and the hurdles faced for licensure of these next-generation influenza virus vaccines.
47 citations
Cites background from "Experimental vaccines against poten..."
...This would likely limit the use and/or efficacy of poxvirus-vectored influenza virus vaccines for regular and seasonal use [13]....
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...availability of current inactivated vaccines, live-attenuated and virus-vectored vaccines are still considered one of the best options for the induction of broad and efficacious immunity to the influenza virus [13]....
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TL;DR: Results of this study revealed that vector-based vaccines comprise a significant part of all GM vaccines in the pipeline, and highlights that poxviruses and adenoviruses are among the most prominent vectors in GM vaccine development.
43 citations
Cites background from "Experimental vaccines against poten..."
...Measles virus – HIV infection – Measles/HIV combination – West Nile virus infection – RNA virus, unable to integrate in host genome – Well known homologous vaccine – Can induce both mucosal and systemic immunity – Pre-existing immunity – Moderate foreign antigenic load [9,28,38]...
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...– Gradient gene expression – Instable genome [38]...
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...– Administration both intranasally and intramuscularly – No pre-existing immunity – No clinical safety data for use in humans available [38,47]...
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...[47] Tripp RA, Tompkins SM. Virus-vectored influenza virus vaccines....
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...[38] Mooney AJ, Tompkins SM. Experimental vaccines against potentially pandemic and highly pathogenic avian influenza viruses....
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TL;DR: Although NA is immunologically subdominant to HA, and clinical studies have shown variable NA responses to vaccination, this study shows that vaccination with parainfluenza virus 5 recombinant vaccine candidate expressing NA (PIV5-NA) from a pandemic influenza virus or highly pathogenic avian influenza (H5N1) virus elicits robust, cross-reactive protection from influenza virus infection in two animal models.
Abstract: Seasonal human influenza virus continues to cause morbidity and mortality annually, and highly pathogenic avian influenza (HPAI) viruses along with other emerging influenza viruses continue to pose pandemic threats. Vaccination is considered the most effective measure for controlling influenza; however, current strategies rely on a precise vaccine match with currently circulating virus strains for efficacy, requiring constant surveillance and regular development of matched vaccines. Current vaccines focus on eliciting specific antibody responses against the hemagglutinin (HA) surface glycoprotein; however, the diversity of HAs across species and antigenic drift of circulating strains enable the evasion of virus-inhibiting antibody responses, resulting in vaccine failure. The neuraminidase (NA) surface glycoprotein, while diverse, has a conserved enzymatic site and presents an appealing target for priming broadly effective antibody responses. Here we show that vaccination with parainfluenza virus 5 (PIV5), a promising live viral vector expressing NA from avian (H5N1) or pandemic (H1N1) influenza virus, elicited NA-specific antibody and T cell responses, which conferred protection against homologous and heterologous influenza virus challenges. Vaccination with PIV5-N1 NA provided cross-protection against challenge with a heterosubtypic (H3N2) virus. Experiments using antibody transfer indicate that antibodies to NA have an important role in protection. These findings indicate that PIV5 expressing NA may be effective as a broadly protective vaccine against seasonal influenza and emerging pandemic threats.IMPORTANCE Seasonal influenza viruses cause considerable morbidity and mortality annually, while emerging viruses pose potential pandemic threats. Currently licensed influenza virus vaccines rely on the antigenic match of hemagglutinin (HA) for vaccine strain selection, and most vaccines rely on HA inhibition titers to determine efficacy, despite the growing awareness of the contribution of neuraminidase (NA) to influenza virus vaccine efficacy. Although NA is immunologically subdominant to HA, and clinical studies have shown variable NA responses to vaccination, in this study, we show that vaccination with a parainfluenza virus 5 recombinant vaccine candidate expressing NA (PIV5-NA) from a pandemic influenza (pdmH1N1) virus or highly pathogenic avian influenza (H5N1) virus elicits robust, cross-reactive protection from influenza virus infection in two animal models. New vaccination strategies incorporating NA, including PIV5-NA, could improve seasonal influenza virus vaccine efficacy and provide protection against emerging influenza viruses.
27 citations
TL;DR: TLC analysis of these extracts showed that flavonoids and saponins were the major classes of natural products found in the shoot extracts that may be responsible for these antiviral activities.
22 citations
References
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TL;DR: Once a neglected cell type, dendritic cells can now be readily obtained in sufficient quantities to allow molecular and cell biological analysis and the realization that these cells are a powerful tool for manipulating the immune system is realized.
Abstract: B and T lymphocytes are the mediators of immunity, but their function is under the control of dendritic cells. Dendritic cells in the periphery capture and process antigens, express lymphocyte co-stimulatory molecules, migrate to lymphoid organs and secrete cytokines to initiate immune responses. They not only activate lymphocytes, they also tolerize T cells to antigens that are innate to the body (self-antigens), thereby minimizing autoimmune reactions. Once a neglected cell type, dendritic cells can now be readily obtained in sufficient quantities to allow molecular and cell biological analysis. With knowledge comes the realization that these cells are a powerful tool for manipulating the immune system.
14,532 citations
"Experimental vaccines against poten..." refers background in this paper
...Moreover, plasmid-vaccinated animals have been shown to express the DNA vaccine in dendritic cells, improving T-cell and global vaccine responses [45]....
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...Adenoviruses infect dendritic cells, among a wide range of other cells, leading to eff icient antigen presentation to the immune system [45]....
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TL;DR: Oligodeoxynucleotides containing CpG ODN enhance the development of acquired immune responses for prophylactic and therapeutic vaccination and protect against lethal challenge with a wide variety of pathogens.
Abstract: Unmethylated CpG motifs are prevalent in bacterial but not vertebrate genomic DNAs. Oligodeoxynucleotides (ODN) containing CpG motifs activate host defense mechanisms leading to innate and acquired immune responses. The recognition of CpG motifs requires Toll-like receptor (TLR) 9, which triggers alterations in cellular redox balance and the induction of cell signaling pathways including the mitogen activated protein kinases (MAPKs) and NF kappa B. Cells that express TLR-9, which include plasmacytoid dendritic cells (PDCs) and B cells, produce Th1-like proinflammatory cytokines, interferons, and chemokines. Certain CpG motifs (CpG-A) are especially potent at activating NK cells and inducing IFN-alpha production by PDCs, while other motifs (CpG-B) are especially potent B cell activators. CpG-induced activation of innate immunity protects against lethal challenge with a wide variety of pathogens, and has therapeutic activity in murine models of cancer and allergy. CpG ODN also enhance the development of acquired immune responses for prophylactic and therapeutic vaccination.
2,557 citations
"Experimental vaccines against poten..." refers background in this paper
...DNA-based vaccines DNA-based vaccines (reviewed in [42]) in short, are bacterial plasmids containing an optimized mammalian promoter driving expression of the gene of interest [42], nucleotide sequences (cytidine phosphate guanosine, or CpG) that stimulate the innate immune system via TLR-9 (reviewed in [43]), and usually a selection marker required for production of the plasmid in bacteria....
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TL;DR: This article corrects the article on p. 496 in vol.
1,986 citations
TL;DR: It is shown that TLR7 recognizes the single-stranded RNA viruses, vesicular stomatitis virus and influenza virus, and insights into the pathways used by the innate immune cells in the recognition of viral pathogens are provided.
Abstract: Viral infection of mammalian host results in the activation of innate immune responses. Toll-like receptors (TLRs) have been shown to mediate the recognition of many types of pathogens, including viruses. The genomes of viruses possess unique characteristics that are not found in mammalian genomes, such as high CpG content and double-stranded RNA. These genomic nucleic acids serve as molecular signatures associated with viral infections. Here we show that TLR7 recognizes the single-stranded RNA viruses, vesicular stomatitis virus and influenza virus. The recognition of these viruses by plasmacytoid dendritic cells and B cells through TLR7 results in their activation of costimulatory molecules and production of cytokines. Moreover, this recognition required intact endocytic pathways. Mice deficient in either the TLR7 or the TLR adaptor protein MyD88 demonstrated reduced responses to in vivo infection with vesicular stomatitis virus. These results demonstrate microbial ligand recognition by TLR7 and provide insights into the pathways used by the innate immune cells in the recognition of viral pathogens.
1,833 citations