The b-carboline harmine is an immunomodulator in cutaneous leishmaniasis favoring the balance towards a protective immune response. The b-carboline harmine is an immunomodulator in cutaneous leishmaniasis favoring the balance towards a protective immune response

Here, we investigated the impact of synthetic b-carboline harmine (ACB1801), on the immune response and pathology resulting from infection with a drug-resistant Leishmania major strain causing non-healing cutaneous lesion. Exposure to ACB1801 impacted only slightly parasite viability and parasite burden in host macrophages in vitro. However, it significantly increased MHC-II and co stimulatory molecules expression on infected DCs, suggesting enhanced immune response. Accordingly, ACB1801 monotherapy significantly decreased lesion development and parasite burden in Leishmania infected C57BL/6 mice, with similar efficacy than the widely used Amphotericin B therapy. ACB1801 impact on the immune response was validated by transcriptomics analysis showing enrichment of TNF-a, IFN-g and MHC-II Ag presentation signatures in the draining lymph nodes of treated mice. Increased frequency of protective CD4+IFN-g+TNF-α+ T cells and reduced suppressive IL-10+FoxP3- T cells was observed by flow cytometry. ACB1801 was further shown to act via the downregulation of Aryl hydroxyl receptor (AhR) signaling, decreasing immunosuppressive cytokines. Thus, these results suggest a potential use for ACB1801 alone or in combination therapy. Overall design: C57BL/6 mice were injected with 2x105 LmSd metacyclic promastigotes into the ear dermis (i.d.). The treatments with ACB1801 or vehicle were started at day 12 post infection for 10 consecutive days. Draining lymph nodes were recovered in RLT plus buffer, homogenized using tissue lyzer. mRNA was extracted using Qiagen RNAeasy mini kit. Contralateral LNs were used as non-infected controls.

本研究探究了合成型β-咔啉类化合物哈马碱（ACB1801）对耐药性硕大利什曼原虫（Leishmania major）毒株引发的非愈合性皮肤损伤相关的免疫应答与病理损伤的影响。
体外实验显示，ACB1801仅对宿主巨噬细胞内的原虫存活率与虫荷量产生轻微影响。然而，其可显著上调感染宿主树突状细胞（dendritic cells, DCs）表面的主要组织相容性复合体II（Major Histocompatibility Complex II, MHC-II）分子与共刺激分子的表达，提示免疫应答得以增强。
相应地，ACB1801单药治疗可显著降低硕大利什曼原虫感染的C57BL/6小鼠的皮肤损伤进展与虫荷量，其疗效与临床广泛使用的两性霉素B（Amphotericin B）疗法相当。
转录组学分析验证了ACB1801对免疫应答的调控作用：经治疗小鼠的引流淋巴结中富集了肿瘤坏死因子-α（Tumor Necrosis Factor-α, TNF-α）、干扰素-γ（Interferon-γ, IFN-γ）及MHC-II抗原呈递相关的特征基因集。流式细胞术检测结果显示，保护性CD4+IFN-γ+TNF-α+ T细胞的频率升高，而具有免疫抑制功能的IL-10+FoxP3- T细胞比例降低。
进一步研究表明，ACB1801通过下调芳基羟基受体（Aryl hydroxyl receptor, AhR）信号通路，减少免疫抑制性细胞因子的分泌。因此，上述结果提示ACB1801单药或联合疗法具备潜在应用价值。
实验总体设计：将2×10^5个LmSd株感染性前鞭毛体注射至C57BL/6小鼠的耳真皮层（皮内注射，i.d.）。于感染后第12天开始，连续10天给予ACB1801或溶剂对照处理。将引流淋巴结收集于RLT Plus裂解缓冲液中，利用组织破碎仪进行匀浆。采用Qiagen RNeasy Mini试剂盒提取信使RNA（messenger RNA, mRNA）。对侧淋巴结作为未感染对照样本。