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Bovine Viral Diarrhoea Virus (BVDV) is one of the most serious pathogen, which causes tremendous economic loss to the cattle industry worldwide, meriting the development of improved subunit vaccines. Structural glycoprotein E2 is reported to be a major immunogenic determinant of BVDV virion. We have developed a novel hollow silica vesicles (SV) based platform to administer BVDV-1 Escherichia coli-expressed optimised E2 (oE2) antigen as a nanovaccine formulation. The SV-140 vesicles (diameter 50 nm, wall thickness 6 nm, perforated by pores of entrance size 16 nm and total pore volume of 0.934 cm3 g(-1)) have proven to be ideal candidates to load oE2 antigen and generate immune response. The current study for the first time demonstrates the ability of freeze-dried (FD) as well as non-FD oE2/SV140 nanovaccine formulation to induce long-term balanced antibody and cell mediated memory responses for at least 6 months with a shortened dosing regimen of two doses in small animal model. The in vivo ability of oE2 (100 μg)/SV-140 (500 μg) and FD oE2 (100 μg)/SV-140 (500 μg) to induce long-term immunity was compared to immunisation with oE2 (100 μg) together with the conventional adjuvant Quil-A from the Quillaja saponira (10 μg) in mice. The oE2/SV-140 as well as the FD oE2/SV-140 nanovaccine generated oE2-specific antibody and cell mediated responses for up to six months post the final second immunisation. Significantly, the cell-mediated responses were consistently high in mice immunised with oE2/SV-140 (1,500 SFU/million cells) at the six-month time point. Histopathology studies showed no morphological changes at the site of injection or in the different organs harvested from the mice immunised with 500 μg SV-140 nanovaccine compared to the unimmunised control. The platform has the potential for developing single dose vaccines without the requirement of cold chain storage for veterinary and human applications.

Bovine viral diarrhoea virus 1 (BVDV-1) is arguably the most important viral disease of cattle. It is associated with reproductive, respiratory and chronic diseases in cattle across the world. In this study we have investigated the capacity of the major immunological determinant of BVDV-1, the E2 protein combined with hollow type mesoporous silica nanoparticles with surface amino functionalisation (HMSA), to stimulate immune responses in sheep. The current work also investigated the immunogenicity of the E2 nanoformulation before and after freeze-drying processes. The optimal excipient formulation for freeze-drying of the E2 nanoformulation was determined to be 5% trehalose and 1% glycine. This excipient formulation preserved both the E2 protein integrity and HMSA particle structure. Sheep were immunised three times at three week intervals by subcutaneous injection with 500 μg E2 adsorbed to 6.2 mg HMSA as either a non-freeze-dried or freeze-dried nanoformulation. The capacity of both nanovaccine formulations to generate humoral (antibody) and cell-mediated responses in sheep were compared to the responses in sheep immunisation with Opti-E2 (500 μg) together with the conventional adjuvant Quil-A (1 mg), a saponin from the Molina tree (Quillaja saponira). The level of the antibody responses detected to both the non-freeze-dried and freeze-dried Opti-E2/HMSA nanoformulations were similar to those obtained for Opti-E2 plus Quil-A, demonstrating the E2 nanoformulations were immunogenic in a large animal, and freeze-drying did not affect the immunogenicity of the E2 antigen. Importantly, it was demonstrated that the long term cell-mediated immune responses were detectable up to four months after immunisation. The cell-mediated immune responses were consistently high in all sheep immunised with the freeze-dried Opti-E2/HMSA nanovaccine formulation (>2,290 SFU/million cells) compared to the non-freeze-dried nanovaccine formulation (213-500 SFU/million cells). This study is the first to demonstrate that a freeze-dried silica mesoporous nanovaccine formulation gives balanced immune responses in a production animal.

Amino functionalised mesoporous silica nanoparticles (AM-41) have been identified as a promising vaccine delivery material. The capacity of AM-41 to stabilise vaccine components at ambient temperature (23-27°C) was determined by adsorbing the model antigen ovalbumin (OVA) to AM-41 particles (OVA-41). The OVA-41 was successfully freeze-dried using the excipients 5% trehalose and 1% PEG8000. The immunological activity of OVA and the nanoparticle structure were maintained following two months storage at ambient temperature. The results of immunisation studies in mice with reconstituted OVA-41 demonstrated the induction of humoral and cell-meditated immune responses. The capacity of AM-41 particles to facilitate ambient storage of vaccine components without the loss of immunological potency will underpin the further development of this promising vaccine delivery platform., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Immunization to the model protein antigen ovalbumin (OVA) is investigated using MCM-41 mesoporous silica nanoparticles as a novel vaccine delivery vehicle and adjuvant system in mice. The effects of amino surface functionalization and adsorption time on OVA adsorption to nanoparticles are assessed. Amino-functionalized MCM-41 (AM-41) shows an effect on the amount of OVA binding, with 2.5-fold increase in binding capacity (72 mg OVA/g AM-41) compared to nonfunctionalized MCM-41 (29 mg OVA/g MCM-41). Immunization studies in mice with a 10 μg dose of OVA adsorbed to AM-41 elicits both antibody and cell-mediated immune responses following three subcutaneous injections. Immunizations at a lower 2 μg dose of OVA adsorbed to AM-41 particles results in an antibody response but not cell-mediated immunity. The level of antibody responses following immunization with nanoformulations containing either 2 μg or 10 μg of OVA are only slightly lower than that in mice which receive 50 μg OVA adjuvanted with QuilA, a crude mixture of saponins extracted from the bark of the Quillaja saponaria Molina tree. This is a significant result, since it demonstrates that AM-41 nanoparticles are self-adjuvanting and elicit immune responses at reduced antigen doses in vivo compared to a conventional delivery system. Importantly, there are no local or systemic negative effects in animals injected with AM-41. Histopathological studies of a range of tissue organs show no changes in histopathology of the animals receiving nanoparticles over a six week period. These results establish the biocompatible MCM-41 silica nanoparticles as a new method for vaccine delivery which incorporates a self-adjuvant effect., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Vaccines have been at the forefront of improving human health for over two centuries. The challenges faced in developing effective vaccines flow from complexities associated with the immune system and requirement of an efficient and safe adjuvant to induce a strong adaptive immune response. Development of an efficient vaccine formulation requires careful selection of a potent antigen, efficient adjuvant and route of delivery. Adjuvants are immunological agents that activate the antigen presenting cells (APCs) and elicit a strong immune response. In the past decade, the use of mesoporous silica nanoparticles (MSNs) has gained significant attention as potential delivery vehicles for various biomolecules. In this review, we aim to highlight the potential of MSNs as vaccine delivery vehicles and their ability to act as adjuvants. We have provided an overview on the latest progress on synthesis, adsorption and release kinetics and biocompatibility of MSNs as next generation antigen carriers and adjuvants. A comprehensive summary on the ability of MSNs to deliver antigens and elicit both humoral and cellular immune responses is provided. Finally, we give insight on fundamental challenges and some future prospects of these nanoparticles as adjuvants.

Anaplasma marginale is the most prevalent tick-borne livestock pathogen and poses a significant threat to cattle industry. In contrast to currently available live blood-derived vaccines against A. marginale, alternative safer and better-defined subunit vaccines will be of great significance. Two proteins (VirB9-1 and VirB9-2) from the Type IV secretion system of A. marginale have been shown to induce humoral and cellular immunity. In this study, Escherichia coli were used to express VirB9-1 and VirB9-2 proteins. Silica vesicles having a thin wall of 6 nm and pore size of 5.8 nm were used as the carrier and adjuvant to deliver these two antigens both as individual or mixed nano-formulations. High loading capacity was achieved for both proteins, and the mouse immunisation trial with individual as well as mixed nano-formulations showed high levels of antibody titres over 107 and strong T-cell responses. The mixed nano-formulation also stimulated high-level recall responses in bovine T-cell proliferation assays. These results open a promising path towards the development of efficient A. marginale vaccines and provide better understanding on the role of silica vesicles to deliver multivalent vaccines as mixed nano-formulations able to activate both B-cell and T-cell immunity, for improved animal health. [ABSTRACT FROM AUTHOR]