Edwards Alexander D, Slater Nigel K H
Vaccine. 2008 Oct 23;26(45):5675-8. doi: 10.1016/j.vaccine.2008.08.024. Epub 2008 Aug 30.
Live bacterial vaccines have great promise both as vaccines against enteric pathogens and as heterologous antigen vectors against diverse diseases. Ideally, room temperature stable dry formulations of live bacterial vaccines will allow oral vaccination without cold-chain storage or injections. Attenuated Salmonella can cross the intestinal wall and deliver replicating antigen plus innate immune activation signals directly to the intestinal immune tissues; however, the ingested bacteria must survive firstly gastric acid and secondly the antimicrobial defences of the small intestine. We found that the way in which cells are grown prior to formulation markedly affects sensitivity to acid and bile. Using a previously published stable storage formulation that maintained over 10% viability after 56 days storage at room temperature, we found dried samples of an attenuated Salmonella serovar Typhimurium vaccine lost acid and bile resistance compared to the same bacteria taken from fresh culture. The stable formulation utilised osmotic pre-conditioning in defined medium plus elevated salt concentration to induce intracellular trehalose accumulation before drying. Dried bacteria grown in rich media without osmotic pre-conditioning showed more resistance to bile, but less stability during storage, suggesting a trade-off between bile resistance and stability. Further optimisation is needed to produce the ultimate room temperature stable oral live bacterial vaccine formulation.
活细菌疫苗作为抗肠道病原体的疫苗以及作为针对多种疾病的异源抗原载体都具有巨大潜力。理想情况下，室温稳定的活细菌疫苗干燥制剂将允许进行无需冷链储存或注射的口服疫苗接种。减毒沙门氏菌可穿过肠壁并将复制抗原以及先天免疫激活信号直接传递至肠道免疫组织；然而，摄入的细菌首先必须在胃酸中存活，其次要在小肠的抗菌防御中存活。我们发现，制剂前细胞的培养方式会显著影响其对酸和胆汁的敏感性。使用先前发表的一种稳定储存制剂，该制剂在室温下储存56天后仍保持超过10%的活力，我们发现，与取自新鲜培养物的相同细菌相比，减毒鼠伤寒沙门氏菌疫苗的干燥样本失去了对酸和胆汁的抗性。该稳定制剂在特定培养基中利用渗透预处理并提高盐浓度，以在干燥前诱导细胞内海藻糖积累。在没有渗透预处理的丰富培养基中生长的干燥细菌对胆汁表现出更高的抗性，但在储存期间稳定性较差，这表明在胆汁抗性和稳定性之间存在权衡。需要进一步优化以生产出最终的室温稳定口服活细菌疫苗制剂。
