Episomal expression of truncated listeriolysin O in LmddA-LLO-E7 vaccine enhances antitumor efficacy by preferentially inducing expansions of CD4+FoxP3- and CD8+ T cells.
Episomal expression of truncated listeriolysin O in LmddA-LLO-E7 vaccine enhances antitumor efficacy by preferentially inducing expansions of CD4+FoxP3- and CD8+ T cells.
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DOI：
10.1158/2326-6066.cir-13-0197
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发表时间：
2014-09
影响因子：
10.1
通讯作者：
Khleif SN
中科院分区：
文献类型：
--
作者：
Chen Z;Ozbun L;Chong N;Wallecha A;Berzofsky JA;Khleif SN
研究表明，表达截短型李斯特菌溶血素O(LLO)和人乳头瘤病毒(HPV)E7蛋白的融合蛋白(LM-LLO-E7)的单核细胞增生性李斯特氏菌(Lm)疫苗可诱导调节性T细胞(Treg)减少，并使小鼠已建立的HPV-TC-1肿瘤完全消退。然而，基于LM的疫苗如何导致Tregs减少仍不清楚。使用高度减毒的LmddA疫苗，我们报道了载体LmddA足以通过依赖和直接由LLO介导的机制优先扩增Δ+−和CD8+T细胞，从而诱导Tregs比例的下降。在LM(LmddA-LLO)中非溶血性截短LLO(LmddA-LLO)的外源表达显著增强了扩增，从而进一步降低了Treg频率。虽然过继转移Tregs会影响LmddA-LLO-E7疫苗的抗肿瘤效果，但LmddA-LLO与表达E7蛋白的LM疫苗(LM-E7)的组合可诱导对已建立的TC-1肿瘤的完全消退。表达产气荚膜溶血素O(PFO)的工程菌LLO-Lm能够使重组菌在没有LLO的情况下退出吞噬溶酶体，证实佐剂效应依赖于LLO。提示LLO可能通过优先诱导−+−T细胞和CD8+T细胞的扩增，从而降低Tregs/CD8+T细胞的比例，有利于免疫应答，从而达到治疗肿瘤的目的，是一种有希望的佐剂。
Studies have shown that Listeria monocytogenes (Lm)-based vaccine expressing a fusion protein comprising truncated listeriolysin O (LLO) and human papilloma virus (HPV) E7 protein (Lm-LLO-E7) induced a decrease in regulatory T cells (Treg) and complete regression of established, transplanted HPV-TC-1 tumors in mice. However, how the Lm-based vaccine causes a decrease in Tregs remains unclear. Using a highly attenuated Lm dal dat ΔactA strain (LmddA)-based vaccine, we report here that the vector LmddA was sufficient to induce a decrease in the proportion of Tregs by preferentially expanding CD4+FoxP3− T cells and CD8+ T cells, by a mechanism dependent on and directly mediated by LLO. Episomal expression of a nonhemolytic truncated LLO in Lm (LmddA-LLO) significantly augmented the expansion, thus further decreasing Treg frequency. While adoptive transfer of Tregs compromised the antitumor efficacy of the LmddA-LLO-E7 vaccine, a combination of LmddA-LLO and an Lm-based vaccine expressing E7 protein (Lm-E7) induced complete regression against established TC-1 tumors. An engineered LLO-minus Lm expressing perfringolysin O (PFO) that enables the recombinant bacteria to exit from the phagolysosome without LLO confirmed that the adjuvant effect was dependent on LLO. These results suggest that LLO may serve as a promising adjuvant by preferentially inducing the expansions of CD4+FoxP3− T cells and CD8+ T cells, thus reducing the ratio of Tregs to CD4+FoxP3− T cells and to CD8+ T cells favoring immune responses to eradicate tumor.