Assessment of route of administration and dose escalation for an adenovirus-based influenza A Virus (H5N1) vaccine in chickens

Evaluation of a self-amplifying mRNA reporter vaccine in explant models of broiler chickens

In order to minimize animal loss and economical loss, industrial poultry is heavily vaccinated against infectious agents. mRNA vaccination is an effective vaccination platform, yet little to no comprehensive, comparative studies in avians can be found. Nevertheless, poultry mRNA vaccination could prove to be very interesting due to the relatively low production cost, especially true when using self-amplifying mRNA (saRNA), and their extreme adaptability to new pathogens. The latter could be particularly useful when new pathogens join the stage or new variants arise. As a first step toward the investigation of saRNA vaccines in poultry, this study evaluates a luciferase-encoding saRNA in avian tracheal explants, conjunctival explants, primary chicken cecal cells and 18-day embryonated eggs. Naked saRNA in combination with RNase inhibitor and 2 different lipid-based formulations, that is, ionizable lipid nanoparticles (LNPs) and Lipofectamine Messenger Max, were evaluated. The saRNA-LNP formulation led to the highest bioluminescent signal in the tracheal explants, conjunctival explants and cecal cell cultures. A dose-response experiment with these saRNA-LNPs (33-900 ng/well) in these avian organoids and cells showed a nonlinear dose-response relationship. After in ovo administration, the highest dose of the saRNA-LNPs (5 µg) resulted in a visual expression as a weak bioluminescence signal could be seen. The other delivery approaches did not lead to a visual saRNA expression in the embryos. In conclusion, effective entry of saRNA encapsulated in LNPs followed by successful saRNA translation in poultry was established. Hence, mRNA vaccination in poultry could be possible, but further in vivo testing is needed.

Poultry Vaccine Technology Platforms

The different technology platforms used to make poultry vaccines are reviewed. Vaccines based on classical technologies are either live attenuated or inactivated vaccines. Genetic engineering is applied to design by deletion, mutation, insertion, or chimerization, genetically modified target microorganisms that are used either as live or inactivated vaccines. Other vaccine platforms are based on one or a few genes of the target pathogen agent coding for proteins that can induce a protective immune response ("protective genes"). These genes can be expressed in vitro to produce subunit vaccines. Alternatively, vectors carrying these genes in their genome or nucleic acid-based vaccines will induce protection by in vivo expression of these genes in the vaccinated host. Properties of these different types of vaccines, including advantages and limitations, are reviewed, focusing mainly on vaccines targeting viral diseases and on technologies that succeeded in market authorization.

Protective immunity induced by oral vaccination with a recombinant Lactococcus lactis vaccine against H5Nx in chickens

BACKGROUND

The development of an influenza vaccine for poultry that provides broadly protective immunity against influenza H5Nx viruses is a challenging goal.

RESULTS

Lactococcus lactis (L. lactis)/pNZ8149-HA1-M2 expressing hemagglutinin-1 (HA1) of A/chicken/Vietnam/NCVD-15A59/2015 (H5N6) and the conserved M2 gene of A/Vietnam/1203/2004 (H5N1) was generated. L. lactis/pNZ8149-HA1-M2 could induce significant humoral, mucosal and cell-mediated immune responses, as well as neutralization antibodies. Importantly, L. lactis/pNZ8149-HA1-M2 could prevent disease symptoms without significant weight loss and confer protective immunity in a chicken model against lethal challenge with divergent influenza H5Nx viruses, including H5N6 and H5N1.

CONCLUSIONS

L. lactis/pNZ8149-HA1-M2 can serve as a promising vaccine candidate in poultry industry for providing protection against H5Nx virus infection in the field application.

Eukaryotic expression system complemented with expressivity of Semliki Forest Virus's RdRp and invasiveness of engineered Salmonella demonstrate promising potential for bacteria mediated gene therapy

This study describes an efficient eukaryotic expression system (pJHL204) built into the Salmonella delivery system to enhance the essential efficacy and effectiveness of conventional DNA therapy. The expression system utilizes RNA-dependent RNA polymerase activity (RdRp) of Semiliki Forest Virus attributing to dramatic antigen expression by cytoplasmic mRNA amplification. Functional characterization of the pJHL204 by in vitro and in vivo transfection studies revealed the improved expression of mRNA at least 150 folds than the RdRp mutant plasmid under in vitro conditions. Using green fluorescence protein (GFP) and mCherry as bait proteins this system was extensively characterized for plasmid delivery capacity, antigen expression, and safety using in vivo and in vitro models by employing flow cytometry, fluorescence microscopy, and immunohistochemical staining. Employment of Salmonella as a carrier significantly extends plasmid in vivo survivability and prolongs the effective duration until the elimination of the Salmonella carrier strain in the host. The strategy can be easily adapted for P2A connected multiple antigen delivery in a single vector system due to the significantly high cargo capacity of Salmonella. A mouse challenge study was carried out utilizing P2A connected H1N1 hemagglutinin (HA) and neuraminidase (NA) via the Salmonella carrier strain JOL2500 significantly reduced viral activity and protected mice against the H1N1 challenge and demonstrates potential to redefine in vivo DNA therapy as a reliable and safe system to treat human diseases using useful microbes like Salmonella.

Genomics Integrated Systems Transgenesis (GENISYST) for gain-of-function disease modelling in Göttingen Minipigs

Göttingen Minipigs show several anatomical, physiological, and pathogenetical similarities to humans and serve an important role in translational studies for example as large animal models of disease. In recent years, the number of transgenic Göttingen Minipigs models has increased, as advanced genetic techniques simplify the generation of animals with precisely tailored modifications. These modifications are designed to replicate genetic alterations responsible for human disease. In addition to serving as valuable large animal disease models, transgenic Göttingen Minipigs are also considered promising donors for xenotransplantation. Current technologies for generation of transgenic minipigs demand a long development and production time of typically 2-3 years. To overcome this limitation and expand the use of Göttingen Minipigs for disease modelling and drug testing, we developed the GENISYST (Genomics Integrated Systems Transgenesis) technology platform for rapid and efficient generation of minipigs based transgenic disease models. As proof of concept, we report the successful generation of transgenic minipigs expressing green fluorescent protein (GFP) in multiple disease-relevant tissues including liver, heart, kidney, lungs, and the central nervous system (CNS). Our data demonstrates the feasibility, efficiency, and utility of GENISYST for rapid one-step generation of transgenic minipigs for human disease modelling in drug discovery and development.

Intragastric delivery of recombinant Lactococcus lactis displaying ectodomain of influenza matrix protein 2 (M2e) and neuraminidase (NA) induced focused mucosal and systemic immune responses in chickens

Compounding with the problem of frequent antigenic shift and occasional drift of the segmented genome of Avian Influenza Virus (AIV), vaccines based on major surface glycoproteins such as haemagglutinin (HA) to counter heterosubtypic AIV infection in chickens remain unsuccessful. In contrast, neuraminidase (NA), the second most abundant surface glycoprotein present in viral capsid is less mutable and, in some instances, successful in eliciting inter-species cross-reactive antibody responses. However, without selective activation of B-cells and T-cells, the ability of NA to induce strong cell mediated immune responses is limited, thus NA based vaccines cannot singularly address the risk of virus escape from host defence. To this end, the highly conserved ectodomain of influenza matrix protein-2 (M2e) has emerged as an attractive cross-protective vaccine target. The present study describes the potential of recombinant Lactococcus lactis (rL. lactis) in expressing functional influenza NA or M2e proteins and conferring effective mucosal and systemic immune responses in the intestine as well as in the upper respiratory airways (trachea) of chickens. In addition, lavages collected from trachea and intestine of birds administered with rL. lactis expressing influenza NA or M2e protein were found to protect MDCK cells against avian influenza type A/PR/8/34 (H1N1) virus challenge. Although minor, the differences in the expression of pro-inflammatory cytokines gene transcripts targeted in this study among the birds administered with either empty or rL. lactis could be attributed to the activation of innate response by L. lactis.

Veterinary vaccine nanotechnology: pulmonary and nasal delivery in livestock animals

Veterinary vaccine development has several similarities with human vaccine development to improve the overall health and well-being of species. However, veterinary goals lean more toward feasible large-scale administration methods and low cost to high benefit immunization. Since the respiratory mucosa is easily accessible and most infectious agents begin their infection cycle at the mucosa, immunization through the respiratory route has been a highly attractive vaccine delivery strategy against infectious diseases. Additionally, vaccines administered via the respiratory mucosa could lower costs by removing the need of trained medical personnel, and lowering doses yet achieving similar or increased immune stimulation. The respiratory route often brings challenges in antigen delivery efficiency with enough potency to induce immunity. Nanoparticle (NP) technology has been shown to enhance immune activation by producing higher antibody titers and protection. Although specific mechanisms between NPs and biological membranes are still under investigation, physical parameters such as particle size and shape, as well as biological tissue distribution including mucociliary clearance influence the protection and delivery of antigens to the site of action and uptake by target cells. For respiratory delivery, various biomaterials such as mucoadhesive polymers, lipids, and polysaccharides have shown enhanced antibody production or protection in comparison to antigen alone. This review presents promising NPs administered via the nasal or pulmonary routes for veterinary applications specifically focusing on livestock animals including poultry.

Progress on adenovirus-vectored universal influenza vaccines

Influenza virus (IFV) infection causes serious health problems and heavy financial burdens each year worldwide. The classical inactivated influenza virus vaccine (IIVV) and live attenuated influenza vaccine (LAIV) must be updated regularly to match the new strains that evolve due to antigenic drift and antigenic shift. However, with the discovery of broadly neutralizing antibodies that recognize conserved antigens, and the CD8(+) T cell responses targeting viral internal proteins nucleoprotein (NP), matrix protein 1 (M1) and polymerase basic 1 (PB1), it is possible to develop a universal influenza vaccine based on the conserved hemagglutinin (HA) stem, NP, and matrix proteins. Recombinant adenovirus (rAd) is an ideal influenza vaccine vector because it has an ideal stability and safety profile, induces balanced humoral and cell-mediated immune responses due to activation of innate immunity, provides 'self-adjuvanting' activity, can mimic natural IFV infection, and confers seamless protection against mucosal pathogens. Moreover, this vector can be developed as a low-cost, rapid-response vaccine that can be quickly manufactured. Therefore, an adenovirus vector encoding conserved influenza antigens holds promise in the development of a universal influenza vaccine. This review will summarize the progress in adenovirus-vectored universal flu vaccines and discuss future novel approaches.

Immunogenicity of an adenoviral-based Middle East Respiratory Syndrome coronavirus vaccine in BALB/c mice

A new type of coronavirus has been identified as the causative agent underlying Middle East Respiratory Syndrome (MERS). The MERS coronavirus (MERS-CoV) has spread in the Middle East, but cases originating in the Middle East have also occurred in the European Union and the USA. Eight hundred and thirty-seven cases of MERS-CoV infection have been confirmed to date, including 291 deaths. MERS-CoV has infected dromedary camel populations in the Middle East at high rates, representing an immediate source of human infection. The MERS-CoV spike (S) protein, a characteristic structural component of the viral envelope, is considered as a key target of vaccines against coronavirus infection. In an initial attempt to develop a MERS-CoV vaccine to ultimately target dromedary camels, we constructed two recombinant adenoviral vectors encoding the full-length MERS-CoV S protein (Ad5.MERS-S) and the S1 extracellular domain of S protein (Ad5.MERS-S1). BALB/c mice were immunized with both candidate vaccines intramuscularly and boosted three weeks later intranasally. All the vaccinated animals had antibody responses against spike protein, which neutralized MERS-CoV in vitro. These results show that an adenoviral-based vaccine can induce MERS-CoV-specific immune responses in mice and hold promise for the development of a preventive vaccine that targets the animal reservoir, which might be an effective measure to eliminate transmission of MERS-CoV to humans.

Effect of dose and route of immunisation on the immune response induced in cattle by heterologous Bacille Calmette-Guerin priming and recombinant adenoviral vector boosting

BCG is used experimentally as a vaccine against tuberculosis (TB), induced by Mycobacterium bovis, in cattle (bTB). However, the efficacy of BCG is variable in humans, cattle and guinea pigs. An adenoviral vector expressing Antigen 85A (Ad5Ag85A) has enhanced protection against TB in mice when used in combination with BCG for prime-boost experiments. However, the route of immunisation affects the degree of protection seen. This work examines the immunogenicity of a new vectored vaccine (Ad5-TBF) that expresses Ag85A, Rv0287, Rv0288 and Rv0251c to explore the effects of dose of adenoviral boost and route of inoculation on immunogenicity. We found that 2×10(9) infectious units (iu) delivered intradermally conferred the most consistent and strongest responses of the different regimes tested.

Adenovirus-Based Vectors for the Development of Prophylactic and Therapeutic Vaccines

Emerging and reemerging infectious diseases as well as cancer pose great global health impacts on the society. Vaccines have emerged as effective treatments to prevent or reduce the burdens of already developed diseases. This is achieved by means of activating various components of the immune system to generate systemic inflammatory reactions targeting infectious agents or diseased cells for control/elimination. DNA virus-based genetic vaccines gained significant attention in the past decades owing to the development of DNA manipulation technologies, which allowed engineering of recombinant viral vectors encoding sequences for foreign antigens or their immunogenic epitopes as well as various immunomodulatory molecules. Despite tremendous progress in the past 50 years, many hurdles still remain for achieving the full clinical potential of viral-vectored vaccines. This chapter will present the evolution of vaccines from “live” or “attenuated” first-generation agents to recombinant DNA and viral-vectored vaccines. Particular emphasis will be given to human adenovirus (Ad) for the development of prophylactic and therapeutic vaccines. Ad biological properties related to vaccine development will be highlighted along with their advantages and potential hurdles to be overcome. In particular, we will discuss (1) genetic modifications in the Ad capsid protein to reduce the intrinsic viral immunogenicity, (2) antigen capsid incorporation for effective presentation of foreign antigens to the immune system, (3) modification of the hexon and fiber capsid proteins for Ad liver de-targeting and selective retargeting to cancer cells, (4) Ad-based vaccines carrying “arming” transgenes with immunostimulatory functions as immune adjuvants, and (5) oncolytic Ad vectors as a new therapeutic approach against cancer. Finally, the combination of adenoviral vectors with other non-adenoviral vector systems, the prime/boost strategy of immunization, clinical trials involving Ad-based vaccines, and the perspectives for the field development will be discussed.

Advances and future challenges in recombinant adenoviral vectored H5N1 influenza vaccines

The emergence of a highly pathogenic avian influenza virus H5N1 has increased the potential for a new pandemic to occur. This event highlights the necessity for developing a new generation of influenza vaccines to counteract influenza disease. These vaccines must be manufactured for mass immunization of humans in a timely manner. Poultry should be included in this policy, since persistent infected flocks are the major source of avian influenza for human infections. Recombinant adenoviral vectored H5N1 vaccines are an attractive alternative to the currently licensed influenza vaccines. This class of vaccines induces a broadly protective immunity against antigenically distinct H5N1, can be manufactured rapidly, and may allow mass immunization of human and poultry. Recombinant adenoviral vectors derived from both human and non-human adenoviruses are currently being investigated and appear promising both in nonclinical and clinical studies. This review will highlight the current status of various adenoviral vectored H5N1 vaccines and will outline novel approaches for the future.

Evaluation of oral immunization with recombinant avian influenza virus HA1 displayed on the Lactococcus lactis surface and combined with the mucosal adjuvant cholera toxin subunit B

The development of safe and efficient avian influenza vaccines for human and animal uses is essential for preventing virulent outbreaks and pandemics worldwide. In this study, we constructed a recombinant (pgsA-HA1 gene fusion) Lactococcus lactis strain that expresses and displays the avian influenza virus HA1 antigens on its surface. The vectors were administered by oral delivery with or without the addition of cholera toxin subunit B (CTB). The resulting immune responses were analyzed, and the mice were eventually challenged with lethal doses of H5N1 viruses. Significant titers of hemagglutinin (HA)-specific serum IgG and fecal IgA were detected in the group that also received CTB. Cellular immunities were also shown in both cell proliferation and gamma interferon (IFN-γ) enzyme-linked immunospot (ELISpot) assays. Most importantly, the mice that received the L. lactis pgsA-HA1 strain combined with CTB were completely protected from lethal challenge of the H5N1 virus. These findings support the further development of L. lactis-based avian influenza virus vaccines for human and animal uses.

miRNA-mediated silencing in hepatocytes can increase adaptive immune responses to adenovirus vector-delivered transgenic antigens

Adenovirus vectors based on human serotype 5 can induce potent CD8 T cell responses to vector-encoded transgenic antigens. However, the individual contribution of different cell types expressing antigen upon adenovirus vector injection to the generation of antigen-directed adaptive immune responses is poorly understood so far. We investigated the role of hepatocytes, skeletal muscle, and hematopoietic cells for the induction of cellular and humoral immune responses by miRNA-mediated tissue-specific silencing of antigen expression. Using hepatitis B small surface antigen (HBsAg) as the vector-encoded transgene we show that adenovirus vector dissemination from an intramuscular (i.m.) injection site into the liver followed by HBsAg expression in hepatocytes can limit early priming of CD8 T cells and the generation of anti-HBsAg antibody responses. However, hepatocyte-specific miRNA122a-mediated silencing of HBsAg expression overcame these limitations. Early clonal expansion of K(b)/S(190-197)-specific CD8 T cells was significantly enhanced and improved polyfunctionality of CD8 T cells was found. Furthermore, miRNA122a-mediated antigen silencing induced significantly higher anti-HBsAg antibody titers allowing an up to 100-fold vector dose reduction. These results indicate that miRNA-mediated regulation of antigen expression in the context of adenovirus vectors can significantly improve transgene product-directed immune responses. This finding could be of interest for future adenovirus vaccine vector development.