Phase I trial of two candidate live oral salmonella enterica serovar paratyphi A

肠道发热是由伤寒沙门氏菌和甲型或B型副伤寒沙门氏菌引起的临床综合征。 最近的频率增加的S。亚洲甲型副伤寒（SPA）和抗生素耐药性的出现 治疗复杂，对美国旅行者构成风险。与S.伤寒，没有疫苗， 防止SPA，这是对美国食品来源的B类优先生物恐怖威胁。我们设计了两个SPA 通过缺失guaBA染色体基因座（其编码两种酶）来制备候选活口服疫苗菌株 在远端从头嘌呤生物合成途径中），并且还在c/pX（编码一个或多个氨基酸序列）中引入缺失。 ATP酶）或dpP（编码蛋白酶），以分别产生菌株CVD 1902和CVD 1903。删除 guaBA已经成为减毒致病性伤寒沙门氏菌的有前途的策略。在以下两种情况中引入删除 dpXP复合物的一个组分提供了第二个独立的减毒突变，以使风险最小化。 理论上可以恢复野生型基因型，也可能增强保护作用， 通过鞭毛蛋白的超表达，鞭毛蛋白是一种保护性抗原， 免疫反应。dpP、dpX、或clpXP中缺失的沙门氏菌产生系统性 感染，但所得dpXP突变体仍然能够保护小鼠免受野生型攻击。 我们建议进行一项I期试验，以评估逐步增加的 CVD 1902和CVD 1903的剂量（107、108和109 CPU）。三个连续的队列（每个队列接受 14名18-45岁的健康受试者将被纳入CVD研究 隔离病房20天，随后在6个月时进行4次门诊和一次电话联系。受试者 每个队列将随机（双盲）接受CVD 1902单次口服接种（N=6） 或CVD 1903（N=6）疫苗或安慰剂（N=2）。在180天的参与期间，受试者将密切关注 观察临床反应，并将捐献一系列血液和粪便样本，以检测 疫苗株，以确保通过符合方案的抗生素消除该菌株，并评价 疫苗刺激相关粘膜、体液和细胞介导的免疫应答的能力。的 将分析结果，目的是选择耐受性良好且具有免疫原性的疫苗株， 进一步临床开发。

Enteric fever is a clinical syndrome caused by Salmonella enterica serovar Typhi and Paratyphi A or B. Recent increases in the frequency of S. Paratyphi A (SPA) in Asia and emergence of antibiotic resistance have complicated treatment and posed a risk to U.S. travelers. In contrast to S. Typhi, there is no vaccine to prevent SPA, a category B priority bioterror threat to U.S. food sources. We have engineered two SPA candidate live oral vaccine strains by deleting the guaBA chromosomal locus (which encodes two enzymes in the distal de novo purine biosynthesis pathway) and also introducing deletions in either c/pX (encoding an ATPase) or dpP (encoding a protease), to create strains CVD 1902 and CVD 1903, respectively. Deleting guaBA has been a promising strategy for attenuating pathogenic S.Typhi. Introducing a deletion in either component of the dpXP complex provides a second, independent attenuating mutation to minimize the risk of a recombination that could theoretically restore the wild type genotype and may also enhance protection by hyper-expression of flagellar protein, a protective antigen that elicits both humoral and cell-mediated immune responses. Salmonella deleted in dpP, dpX, orclpXP have decreased ability to produce systemic infection yet the resultant dpXP mutants remain capable of protecting mice against wild type challenge. We propose to conduct a Phase 1 trial to evaluate the safety, tolerability, and immunogenicity of escalating dosages (107, 108, and 109 CPU) of CVD 1902 and CVD 1903. Three consecutive cohorts (each receiving a higher dosage of vaccine) of 14 healthy subjects 18-45 years of age will be admitted to the CVD Research Isolation Ward for 20 days followed by 4 outpatient visits and a telephone contact at 6 months. Subjects in each cohort will be randomized (double-blind) to receive a single oral inoculation with either CVD 1902 (N=6) or CVD 1903 (N=6) vaccine or placebo (N=2). During their 180-day participation, subjects will be closely observed for clinical response and will donate serial samples of blood and stool to detect colonization with the vaccine strain, to ensure that the strain was eliminated by per-protocol antibiotics, and to evaluate the ability of the vaccines to stimulate relevant mucosal, humoral, and cell-mediated immune responses. The results will be analyzed with the aim of selecting a well-tolerated and immunogenic vaccine strain and dosage for further clinical development.