Department of Medical Biotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran.
Department of Immunotherapy and Leishmania Vaccine Research, Pasteur Institute of Iran, Tehran, Iran.
PLoS Negl Trop Dis. 2019 Jan 11;13(1):e0007067. doi: 10.1371/journal.pntd.0007067. eCollection 2019 Jan.
The vector-borne disease leishmaniasis is transmitted to humans by infected female sand flies, which transmits Leishmania parasites together with saliva during blood feeding. In Iran, cutaneous leishmaniasis (CL) is caused by Leishmania (L.) major and L. tropica, and their main vectors are Phlebotomus (Ph.) papatasi and Ph. sergenti, respectively. Previous studies have demonstrated that mice immunized with the salivary gland homogenate (SGH) of Ph. papatasi or subjected to bites from uninfected sand flies are protected against L. major infection.
In this work we tested the immune response in BALB/c mice to 14 different plasmids coding for the most abundant salivary proteins of Ph. sergenti. The plasmid coding for the salivary protein PsSP9 induced a DTH response in the presence of a significant increase of IFN-γ expression in draining lymph nodes (dLN) as compared to control plasmid and no detectable PsSP9 antibody response. Animals immunized with whole Ph. sergenti SGH developed only a saliva-specific antibody response and no DTH response. Mice immunized with whole Ph. sergenti saliva and challenged intradermally with L. tropica plus Ph. sergenti SGH in their ears, exhibited no protective effect. In contrast, PsSP9-immunized mice showed protection against L. tropica infection resulting in a reduction in nodule size, disease burden and parasite burden compared to controls. Two months post infection, protection was associated with a significant increase in the ratio of IFN-γ to IL-5 expression in the dLN compared to controls.
This study demonstrates that while immunity to the whole Ph. sergenti saliva does not induce a protective response against cutaneous leishmaniasis in BALB/c mice, PsSP9, a member of the PpSP15 family of Ph. sergenti salivary proteins, provides protection against L. tropica infection. These results suggest that this family of proteins in Ph. sergenti, Ph. duboscqi and Ph. papatasi may have similar immunogenic and protective properties against different Leishmania species. Indeed, this anti-saliva immunity may act as an adjuvant to accelerate the cell-mediated immune response to co-administered Leishmania antigens, or even cause the activation of infected macrophages to remove parasites more efficiently. These findings highlight the idea of applying arthropod saliva components in vaccination approaches for diseases caused by vector-borne pathogens.
由感染雌性沙蝇传播的虫媒病利什曼病会传染给人类，沙蝇在吸血时会同时传播利什曼原虫寄生虫和唾液。在伊朗，皮肤利什曼病（CL）由利什曼原虫（L.）引起。主要和 L. 热带，其主要载体分别是 Phlebotomus（Ph.）papatasi 和 Ph. sergenti。先前的研究表明，用 Ph. papatasi 唾液腺匀浆或未感染的沙蝇叮咬免疫的小鼠可预防 L. major 感染。
在这项工作中，我们测试了 BALB/c 小鼠对 14 种不同质粒编码的 Ph. sergenti 最丰富唾液蛋白的免疫反应。与对照质粒相比，编码唾液蛋白 PsSP9 的质粒在存在显著增加的 IFN-γ表达的情况下诱导 DTH 反应，并且没有检测到 PsSP9 抗体反应。用整个 Ph. sergenti SGH 免疫的动物仅产生针对唾液的抗体反应，而没有 DTH 反应。用整个 Ph. sergenti 唾液和在耳朵中用 L. tropica 加 Ph. sergenti SGH 皮内挑战免疫的小鼠，没有表现出保护作用。相比之下，PsSP9 免疫的小鼠对 L. tropica 感染表现出保护作用，导致与对照组相比，结节大小、疾病负担和寄生虫负担减少。感染后 2 个月，与对照组相比，dLN 中 IFN-γ与 IL-5 表达的比值显著增加与保护相关。
本研究表明，尽管针对整个 Ph. sergenti 唾液的免疫不能诱导 BALB/c 小鼠对皮肤利什曼病产生保护性反应，但属于 Ph. sergenti 唾液蛋白 PpSP15 家族的 PsSP9 提供了对 L. tropica 感染的保护。这些结果表明，Ph. sergenti、Ph. duboscqi 和 Ph. papatasi 中的这种蛋白家族可能对不同的利什曼原虫物种具有类似的免疫原性和保护特性。事实上，这种抗唾液免疫可能作为佐剂加速对共同给予的利什曼原虫抗原的细胞介导免疫反应，甚至导致激活受感染的巨噬细胞更有效地去除寄生虫。这些发现强调了在由虫媒病原体引起的疾病的疫苗接种方法中应用节肢动物唾液成分的想法。
