Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, MD, USA.
Vaccine Platform Group, MedImmune, Gaithersburg, MD, USA.
Vaccine. 2018 Jun 27;36(28):4023-4031. doi: 10.1016/j.vaccine.2018.05.101. Epub 2018 May 31.
Vaccination can significantly reduce worldwide morbidity and mortality to infectious diseases, thereby reducing the health burden as a result of microbial infections. Effective vaccines contain three components: a delivery system, an antigenic component of the pathogen, and an adjuvant. With the growing use of purely recombinant or synthetic antigens, there is a need to develop novel adjuvants that enhance the protective efficacy of a vaccine against infection. Using a structure-activity relationship (SAR) model, we describe here the synthesis of a novel TLR4 ligand adjuvant compound, BECC438, by bacterial enzymatic combinatorial chemistry (BECC). This compound was identified using an in vitro screening pipeline consisting of (i) NFκB activation and cytokine production by immortalized cell lines, (ii) cytokine production by primary human PBMCs, and (iii) upregulation of surface costimulatory markers by primary human monocyte-derived dendritic cells. Using this SAR screening regimen, BECC438 was shown to produce an innate immune activation profile comparable to the well-characterized TLR4 agonist adjuvant compound, phosphorylated hexa-acyl disaccharide (PHAD). To evaluate the in vivo adjuvant activity of BECC438, we used the known protective Yersinia pestis (Yp) antigen, rF1-V, in a murine prime-boost vaccination schedule followed by lethal challenge. In addition to providing protection from lethal challenge, BECC438 stimulated production of higher levels of rF1-V-specific total IgG as compared to PHAD after both prime and boost vaccinations. Similar to PHAD, BECC438 elicited a balanced IgG1/IgG2c response, indicative of active T2/T1-driven immunity. These data demonstrate that the novel BECC-derived TLR4L adjuvant, BECC438, elicits cytokine profiles in vitro similar to PHAD, induces high antigen-specific immune titers and a T1-associated IgG2c immune titer skew, and protects mice against a lethal Yp challenge.
疫苗接种可以显著降低全球传染病的发病率和死亡率，从而减轻微生物感染导致的健康负担。有效的疫苗包含三个组成部分：传递系统、病原体的抗原成分和佐剂。随着纯重组或合成抗原的应用日益广泛，需要开发新型佐剂来提高疫苗对感染的保护效力。本研究利用结构活性关系（SAR）模型，描述了一种新型 TLR4 配体佐剂化合物 BECC438 的合成，该化合物是通过细菌酶组合化学（BECC）合成的。通过体外筛选，我们确定了这种化合物，该筛选过程包括：（i）永生化细胞系的 NFκB 激活和细胞因子产生；（ii）原代人 PBMCs 的细胞因子产生；（iii）原代人单核细胞衍生树突状细胞表面共刺激标记物的上调。利用这种 SAR 筛选方案，BECC438 产生的先天免疫激活谱与公认的 TLR4 激动剂佐剂化合物磷酸化六酰基二糖（PHAD）相当。为了评估 BECC438 的体内佐剂活性，我们在已知保护性鼠疫耶尔森菌（Yp）抗原 rF1-V 的小鼠初免-加强免疫接种方案中进行了研究，随后进行了致死性挑战。除了提供对致死性挑战的保护外，与 PHAD 相比，BECC438 在初免和加强免疫后均可刺激产生更高水平的 rF1-V 特异性总 IgG。与 PHAD 相似，BECC438 诱导出平衡的 IgG1/IgG2c 反应，表明存在活跃的 T2/T1 驱动的免疫。这些数据表明，新型 BECC 衍生的 TLR4L 佐剂 BECC438 在体外产生与 PHAD 相似的细胞因子谱，诱导高抗原特异性免疫滴度和 T1 相关 IgG2c 免疫滴度倾斜，并保护小鼠免受致命 Yp 挑战。
