Prokarium Ltd., London Bioscience Innovation Centre, 2 Royal College Street, London NW1 0NH, UK.
Int J Mol Sci. 2021 Mar 23;22(6):3287. doi: 10.3390/ijms22063287.
Enteric fever is a major global healthcare issue caused largely by serovars Typhi and Paratyphi A. The objective of this study was to develop a novel, bivalent oral vaccine capable of protecting against both serovars. Our approach centred on genetically engineering the attenuated Typhi ZH9 strain, which has an excellent safety record in clinical trials, to introduce two Paratyphi A immunogenic elements: flagellin H:a and lipopolysaccharide (LPS) O:2. We first replaced the native Typhi gene encoding flagellin with the highly homologous gene from Paratyphi A using Xer-cise technology. Next, we replaced the Typhi gene encoding tyvelose epimerase with a spacer sequence to enable the sustained expression of O:2 LPS and prevent its conversion to O:9 through tyvelose epimerase activity. The resulting new strain, ZH9PA, incorporated these two genetic changes and exhibited comparable growth kinetics to the parental ZH9 strain. A formulation containing both ZH9 and ZH9PA strains together constitutes a new bivalent vaccine candidate that targets both Typhi and Paratyphi A antigens to address a major global healthcare gap for enteric fever prophylaxis. This vaccine is now being tested in a Phase I clinical trial (NCT04349553).
肠热病是一个主要的全球医疗保健问题，主要由伤寒血清型 Typhi 和 Paratyphi A 引起。本研究的目的是开发一种新型的、双价口服疫苗，能够预防这两种血清型。我们的方法集中在基因工程改造减毒伤寒血清型 ZH9 株上，该株在临床试验中具有极好的安全性记录。我们引入了两种 Paratyphi A 的免疫原性成分：鞭毛蛋白 H:a 和脂多糖（LPS）O:2。我们首先使用 Xer-cise 技术，用来自 Paratyphi A 的高度同源的基因替换了天然的 Typhi 编码鞭毛蛋白的基因。接下来，我们用间隔序列替换了 Typhi 编码 tyvelose 差向异构酶的基因，以实现 O:2 LPS 的持续表达，并通过 tyvelose 差向异构酶活性防止其转化为 O:9。由此产生的新菌株 ZH9PA 包含这两个遗传变化，其生长动力学与亲本 ZH9 株相当。包含 ZH9 和 ZH9PA 两种菌株的配方构成了一种新的双价疫苗候选物，针对伤寒血清型 Typhi 和 Paratyphi A 抗原，以解决肠热病预防的一个主要全球医疗保健差距。该疫苗目前正在进行 I 期临床试验（NCT04349553）。
