In vivo delivery of bovine viral diahorrea virus, E2 protein using hollow mesoporous silica nanoparticles

Abstract

Our work focuses on the application of mesoporous silica nanoparticles as a combined delivery vehicle and adjuvant for vaccine applications. Here we present results using the viral protein, E2, from bovine viral diarrhoea virus (BVDV). BVDV infection occurs in the target species of cattle and sheep herds worldwide and is therefore of economic importance. E2 is a major immunogenic determinant of BVDV and is an ideal candidate for the development of a subunit based nanovaccine using mesoporous silica nanoparticles. Hollow type mesoporous silica nanoparticles with surface amino functionalisation (termed HMSA) were characterised and assessed for adsorption and desorption of E2. A codon-optimised version of the E2 protein (termed Opti-E2) was produced in Escherichia coli. HMSA (120 nm) had an adsorption capacity of 80 μg Opti-E2 per mg HMSA and once bound E2 did not dissociate from the HMSA. Immunisation studies in mice with a 20 μg dose of E2 adsorbed to 250 μg HMSA was compared to immunisation with Opti-E2 (50 μg) together with the traditional adjuvant Quillaja saponaria Molina tree saponins (QuilA, 10 μg). The humoral responses with the Opti-E2/HMSA nanovaccine although slightly lower than those obtained for the Opti-E2 + QuilA group demonstrated that HMSA particles are an effective adjuvant that stimulated E2-specific antibody responses. Importantly the cell-mediated immune responses were consistently high in all mice immunised with Opti-E2/HMSA nanovaccine formulation. Therefore we have shown the Opti-E2/HMSA nanoformulation acts as an excellent adjuvant that gives both T-helper 1 and T-helper 2 mediated responses in a small animal model. This study has provided proof-of-concept towards the development of an E2 subunit nanoparticle based vaccine.

Silica vesicles as nanocarriers and adjuvants for generating both antibody and T-cell mediated immune resposes to Bovine Viral Diarrhoea Virus E2 protein

“…All the animals remained healthy throughout the duration of the trial and none of the nanovaccine formulations caused localised skin redness or reaction at the site of the injection, indicating that the SV were very well tolerated in mice. The treatment groups injected with oE2/SV-140 (50 mg/250 mg) induced excellent antibody response at 10 5 titre, which was higher than the positive control group oE2 (50 mg) plus Quil A (10 mg) (10 4 titre) as well as the responses generated by the mice treated with oE2/ HMSA (10 3 titre) [23]. In addition to elicitation of the humoral response, the oE2/SV-140 induced a stronger and higher memory response (1954e2628 SFU/million cells) compared to the group treated with Quil A (512e1369 SFU/million cells).…”

“…A recent finding, showed that intramuscular immunisation with a dose of 100 mg PCV2 per 0.7 mg HMSNs particles generated PCV2-specific antibody serum response as well as T-cell responses [35]. Previously, we have reported the induction of humoral and cellmediated immune responses by amino functionalised MSNs as well as HMSAs [23,25], however due to the low loading of proteins obtained on the nanoparticles, a direct comparison between the positive control group comprising of conventional adjuvant and the nanovaccine treatment could not be performed. In the current research study, the improvement in the particle design enabled us to directly compare the immune responses generated by the conventional adjuvant used in the positive control group (oE2 plus Quil A) and the nanovaccine treatment group.…”

“…Previously, we reported the use of (HMSA) surface functionalised with amino groups for the development of BVDV-E2 nanovaccine [23]. However, the limitation of that study was the amount of protein that could be loaded on the HMSA, which was 80 mg of the oE2 protein per mg of HMSA.…”

“…As determined by DLS the hydrodynamic size of oE2 was 7.1 nm [43]. Utilising the iTasser protein structure prediction software [46,47] and the recent publication on E2 crystal structure, which used the 2YQ2 [48] as a structural template, oE2 was hypothesised to be an elongated protein with an estimated physical size length of 12e13 nm and a width of 3e4 nm [23]. The entrance size of the SVs is in the range of 5.7e16 nm, which is larger than the estimated width size of the oE2, our assumption is that the protein gets adsorbed on the internal as well as external wall of the vesicles leading to higher loading capacity.…”

“…In our laboratory, we have previously described the use of OVA loaded amino functionalised MSNs and BVDV E2 loaded on hollow mesoporous silica nanoparticles (HMSA) (23)(24)(25). Though, we were able to get low levels of detectable antibody and cell-mediated responses, the major limitations were very low protein loading efficiency (60e80 mg/mg of particles), small entrance size (2e3.5 nm) and possibly only surface presentation of proteins on these silica nanocarriers.…”