Abstract
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.
Highlights
Anaplasma marginale is the most prevalent tick-borne livestock pathogen which causes an infection within cattle, commonly known as ‘Tick Fever’ [1, 2]
The amplified DNA fragments were cloned into pGEX4T1 glutathione S-transferase (GST) tagged expression vector with the thrombin recognition site sequence mutated into tobacco etch virus (TEV) protease recognition site sequence
High pH is not suitable for downstream purification as the GST affinity column optimally works in the range of pH 6.5–8.0, pH 8.0 buffer was chosen for protein purification
Summary
Anaplasma marginale is the most prevalent tick-borne livestock pathogen which causes an infection within cattle, commonly known as ‘Tick Fever’ [1, 2]. Combavac 3 in 1 live tick fever vaccine [5] is one of the marketed vaccines against A. marginale It has many disadvantages, such as cold chain for transport and storage, a short shelf life after thawing, and the requirement of multiple doses for vaccination [5]. For these reasons, the currently available vaccines for A. marginale are considered neither safe nor efficacious [2, 4]
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