Purpose: This study aimed to describe a novel cancer vaccine developed using H₂O₂-inactivated Salmonella typhimurium RE88 [with deletions of AroA (the first enzyme in the aromatic amino acid biosynthesis pathway) and DNA adenine methylase] as the carrier.
Methods: The pVLT33 plasmid was used to engineer an RE88 strain induced to express ovalbumin (OVA) by isopropylthiogalactoside (RE88-pVLT33-OVA). The immune responses and anticancer effects of H₂O₂-inactivated RE88-pVLT33-OVA were compared with those of non-inactivated RE88-pVLT33-OVA and OVA (positive control) in mice carrying OVA-expressing tumors (EG7-OVA) cells.
Results: Anti-ovalbumin IgG (immunoglobulin G) titer following vaccination with H₂O₂-inactivated RE88-pVLT33-OVA was higher for subcutaneous than for intragastric vaccination. When subcutaneous administration was used, H₂O₂-inactivated RE88-pVLT33-OVA (2 × 10⁹ CFU (colony forming units)/mouse) achieved an anti-ovalbumin IgG titer higher than that for the same dose of RE88-pVLT33-OVA and comparable to that for 10 μg ovalbumin (positive control). The binding of mouse serum antibodies to EG7-OVA cells was stronger for H₂O₂-inactivated RE88-pVLT33-OVA (2 × 10⁹ CFU/mouse) than for 10 μg ovalbumin. Furthermore, subcutaneous vaccination with H₂O₂-inactivated RE88-pVLT33-OVA (2 × 10⁹ CFU/mouse) induced greater activation of splenic T cells and more extensive tumor infiltration with CD4⁺/CD8⁺ T cells compared with 10 μg ovalbumin (positive control). The mice vaccinated subcutaneously with H₂O₂-inactivated RE88-pVLT33-OVA at a dose of 2 × 10⁸ or 6 × 10⁸ CFU/mouse had smaller tumors compared with mice in the negative control groups. Tumor weight in mice vaccinated with H₂O₂-inactivated RE88-pVLT33-OVA at a dose of 2 × 10⁹ CFU/mouse was significantly lower than that in both negative control groups (P < 0.05) and decreased with the increasing dose of H₂O₂-inactivated RE88-pVLT33-OVA. H₂O₂-inactivated RE88-pVLT33-OVA was potentially safer than the non-inactivated strain, could carry exogenous antigens, and had specific epitopes that could be exploited as natural adjuvants to facilitate the induction of cellular and humoral immune responses.
Conclusion: It was anticipated that H₂O₂-inactivated RE88-pVLT33-OVA could be used as a novel delivery system for new cancer vaccines.

Keywords: cancer vaccine, H₂O₂ inactivation, RE88-pVLT33-OVA, whole-cell bacterial vaccine


中文翻译：

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H2O2 灭活鼠伤寒沙门氏菌 RE88 菌株作为新的癌症疫苗载体：在小鼠癌症模型中的评估

目的：本研究旨在描述一种以H ₂ O _2灭活的鼠伤寒沙门氏菌RE88 [缺失AroA（芳香族氨基酸生物合成途径中的第一种酶）和DNA腺嘌呤甲基化酶]为载体开发的新型癌症疫苗。
方法： pVLT33 质粒用于改造 RE88 菌株，通过异丙基硫代半乳糖苷 (RE88-pVLT33-OVA) 诱导表达卵清蛋白 (OVA)。_{在携带 OVA 表达肿瘤 (EG7-OVA) 细胞的小鼠中，将 H 2} O ₂灭活的 RE88-pVLT33-OVA 与未灭活的 RE88-pVLT33-OVA 和 OVA（阳性对照）的免疫反应和抗癌作用进行比较.
结果：_{用H 2} O ₂灭活的RE88-pVLT33-OVA接种后的抗卵白蛋白IgG（免疫球蛋白G）滴度对于皮下接种高于对于胃内接种。当使用皮下给药时，H ₂ O ₂ -灭活的RE88-pVLT33-OVA（2×10 ⁹ CFU（菌落形成单位）/小鼠）的抗卵白蛋白IgG滴度高于相同剂量的RE88-pVLT33- OVA 与 10 μg 卵清蛋白（阳性对照）的结果相当。_{H 2} O ₂灭活的RE88-pVLT33-OVA（2×10 ⁹ CFU/小鼠）的小鼠血清抗体与EG7-OVA细胞的结合比10μg卵白蛋白的更强。此外，皮下接种 H与 10 μg 卵清蛋白（阳性对照）相比，₂ O ₂ -灭活的 RE88-pVLT33-OVA（2 × 10 ⁹ CFU/小鼠）诱导脾 T 细胞的更大活化和 CD4 ⁺ /CD8 ^{+ T 细胞更广泛的肿瘤浸润。}与阴性对照组中的小鼠相比，以2×10 ⁸或6×10 ⁸ CFU/小鼠的剂量用H ₂ O ₂灭活的RE88-pVLT33-OVA皮下接种的小鼠具有更小的肿瘤。^{以 2 × 10 9}的剂量接种 H ₂ O ₂灭活的 RE88-pVLT33-OVA 的小鼠的肿瘤重量CFU/小鼠显着低于两个阴性对照组（P < 0.05），并随着H ₂ O ₂灭活RE88-pVLT33-OVA剂量的增加而降低。H ₂ O ₂灭活的RE88-pVLT33-OVA可能比未灭活的菌株更安全，可以携带外源性抗原，并且具有可用作天然佐剂以促进细胞和体液免疫反应的诱导的特定表位。
结论：预计H ₂ O ₂灭活的RE88-pVLT33-OVA可用作新型癌症疫苗的新型递送系统。

关键词：癌症疫苗，H ₂ O₂灭活，RE88-pVLT33-OVA，全细胞细菌疫苗