Department of Biotechnology, Faculty of Applied Sciences, AIMST University, 08100, Semeling, Kedah, Malaysia.
Department of Medical Microbiology and Parasitology, School of Medical Sciences, Universiti Sains Malaysia, 16150, Kubang Kerian, Kelantan, Malaysia.
BMC Immunol. 2020 May 25;21(1):29. doi: 10.1186/s12865-020-00360-1.
Cholera, an acute watery diarrhoeal disease caused by Vibrio cholerae serogroup O1 and O139 across the continents. Replacing the existing WHO licensed killed multiple-dose oral cholera vaccines that demand 'cold chain supply' at 2-8 °C with a live, single-dose and cold chain-free vaccine would relieve the significant bottlenecks and cost determinants in cholera vaccination campaigns. In this direction, a prototype cold chain-free live attenuated cholera vaccine formulation (LACV) was developed against the toxigenic wild-type (WT) V. cholerae O139 serogroup. LACV was found stable and retained its viability (5 × 10 CFU/mL), purity and potency at room temperature (25 °C ± 2 °C, and 60% ± 5% relative humidity) for 140 days in contrast to all the existing WHO licensed cold-chain supply (2-8 °C) dependent killed oral cholera vaccines.
The LACV was evaluated for its colonization potential, reactogenicity, immunogenicity and protective efficacy in animal models after its storage at room temperature for 140 days. In suckling mice colonization assay, the LACV recorded the highest recovery of (7.2 × 10 CFU/mL) compared to those of unformulated VCUSM14P (5.6 × 10 CFU/mL) and the WT O139 strain (3.5 × 10 CFU/mL). The LACV showed no reactogenicity even at an inoculation dose of 10-10 CFU/mL in a rabbit ileal loop model. The rabbits vaccinated with the LACV or unformulated VCUSM14P survived a challenge with WT O139 and showed no signs of diarrhoea or death in the reversible intestinal tie adult rabbit diarrhoea (RITARD) model. Vaccinated rabbits recorded a 275-fold increase in anti-CT IgG and a 15-fold increase in anti-CT IgA antibodies compared to those of rabbits vaccinated with unformulated VCUSM14P. Vibriocidal antibodies were increased by 31-fold with the LACV and 14-fold with unformulated VCUSM14P.
The vaccine formulation mimics a natural infection, is non-reactogenic and highly immunogenic in vivo and protects animals from lethal wild-type V. cholerae O139 challenge. The single dose LACV formulation was found to be stable at room temperature (25 ± 2 °C) for 140 days and it would result in significant cost savings during mass cholera vaccination campaigns.
霍乱是一种由霍乱弧菌血清群 O1 和 O139 引起的急性水样腹泻病，在各大洲均有发生。用一种无需冷链供应（在 2-8°C 下）的、可单次口服且无需冷链的活疫苗替代现有的世界卫生组织许可的、多剂量口服霍乱疫苗，将缓解霍乱疫苗接种活动中的重大瓶颈和成本决定因素。为此，针对产毒性野生型（WT）霍乱弧菌 O139 血清群，开发了一种无需冷链供应的原型活减毒霍乱疫苗制剂（LACV）。LACV 在室温（25°C ± 2°C，60% ± 5%相对湿度）下储存 140 天，其稳定性、存活能力（5×10 CFU/mL）、纯度和效力均保持不变，而所有现有的世界卫生组织许可的依赖冷链供应（2-8°C）的灭活口服霍乱疫苗均无法做到这一点。
在室温下储存 140 天后，对 LACV 的定植潜力、反应原性、免疫原性和保护效力进行了评估。在幼鼠定植试验中，LACV 的回收量最高（7.2×10 CFU/mL），高于未配方 VCUSM14P（5.6×10 CFU/mL）和 WT O139 株（3.5×10 CFU/mL）。在兔回肠袢模型中，即使接种剂量为 10-10 CFU/mL，LACV 也没有表现出反应原性。用 LACV 或未配方 VCUSM14P 接种的兔子在 WT O139 挑战中存活下来，并且在可逆性肠结扎成年兔腹泻（RITARD）模型中没有出现腹泻或死亡迹象。与用未配方 VCUSM14P 接种的兔子相比，接种 LACV 或未配方 VCUSM14P 的兔子的抗 CT IgG 增加了 275 倍，抗 CT IgA 抗体增加了 15 倍。LACV 使杀弧菌抗体增加了 31 倍，未配方 VCUSM14P 使杀弧菌抗体增加了 14 倍。
该疫苗制剂模拟了自然感染，在体内具有非反应原性和高度免疫原性，并能保护动物免受致死性野生型霍乱弧菌 O139 的攻击。单次剂量的 LACV 制剂在室温（25°C ± 2°C）下可稳定 140 天，这将在大规模霍乱疫苗接种活动中节省大量成本。
