Unidad de Investigación en Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México, Hospital General de México, Dr. Balmis 148, Col. Doctores, CP 06726 Ciudad de México, Mexico.
Facultad de Medicina Veterinaria y Zootecnia, Departamento de Patología y Microscopía electrónica, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Av. Universidad 3000, CP 04510 Ciudad de México, Mexico.
J Immunol Res. 2020 Dec 2;2020:8894549. doi: 10.1155/2020/8894549. eCollection 2020.
Exosomes are extracellular microvesicles of endosomal origin (multivesicular bodies, MVBs) constitutively released by eukaryotic cells by fusion of MVBs to the plasma membrane. The exosomes from parasites contain an array of parasite molecules such as virulence factors and survival messengers, capable of modulating the host immune response and thereby favoring the infection of the host. We here show that exosomes of amastigotes (aExo) contain the virulence proteins gp63 and PP2C. The incubation of aExo with bone marrow-derived macrophages (BMMs) infected with led to their internalization and were found to colocalize with the cellular tetraspanin CD63. Furthermore, aExo inhibited nitric oxide production of infected BMMs, permitting enhanced intracellular parasite survival. Expressions of antigen-presenting (major histocompatibility complex class I, MHC-I, and CD1d) and costimulatory (CD86 and PD-L1) molecules were modulated in a dose-dependent fashion. Whereas MHC-I, CD86 and PD-L1 expressions were diminished by exosomes, CD1d was enhanced. We conclude that aExo of are capable of decreasing microbicidal mechanisms of infected macrophages by inhibiting nitric oxide production, thereby enabling parasite survival. They also hamper the cellular immune response by diminishing MHC-I and CD86 on an important antigen-presenting cell, which potentially interferes with CD8 T cell activation. The enhanced CD1d expression in combination with reduction of PD-L1 on BMMs point to a potential shift of the activation route towards lipid presentations, yet the effectivity of this immune activation is not evident, since in the absence of costimulatory molecules, cellular anergy and tolerance would be expected.
外泌体是起源于内体的细胞外微囊泡（多泡体，MVB），通过 MVB 与质膜融合，真核细胞持续释放外泌体。寄生虫的外泌体包含一系列寄生虫分子，如毒力因子和存活信使，能够调节宿主免疫反应，从而有利于宿主感染。我们在这里表明， 前鞭毛体的外泌体（aExo）含有毒力蛋白 gp63 和 PP2C。将 aExo 与 感染的骨髓来源巨噬细胞（BMM）孵育，导致它们被内化，并发现与细胞四跨膜蛋白 CD63 共定位。此外，aExo 抑制感染的 BMM 产生一氧化氮，允许增强细胞内寄生虫存活。抗原呈递（主要组织相容性复合体 I 类，MHC-I 和 CD1d）和共刺激（CD86 和 PD-L1）分子的表达以剂量依赖的方式被调节。虽然 MHC-I、CD86 和 PD-L1 的表达被外泌体减弱，但 CD1d 增强。我们得出结论， 的 aExo 能够通过抑制一氧化氮产生来降低感染巨噬细胞的杀菌机制，从而使寄生虫存活。它们还通过减少重要抗原呈递细胞上的 MHC-I 和 CD86 来阻碍细胞免疫反应，这可能干扰 CD8 T 细胞的激活。BMMs 上 CD1d 的增强表达与 PD-L1 的减少相结合表明激活途径可能向脂质呈递转移，但这种免疫激活的效果并不明显，因为在没有共刺激分子的情况下，预计会出现细胞无反应性和耐受性。
