Dewerchin Hannah L, Cornelissen Els, Van Hamme Evelien, Smits Kaatje, Verhasselt Bruno, Nauwynck Hans J
Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University, Belgium.
Department of Clinical Chemistry, Microbiology and Immunology, Faculty of Medicine and Health Science, Ghent University, Belgium.
J Gen Virol. 2008 Nov;89(Pt 11):2731-2740. doi: 10.1099/vir.0.2008/002212-0.
Infection with feline infectious peritonitis virus (FIPV), a feline coronavirus, frequently leads to death in spite of a strong humoral immune response. In previous work, we reported that infected monocytes, the in vivo target cells of FIPV, express viral proteins in their plasma membranes. These proteins are quickly internalized upon binding of antibodies. As the cell surface is cleared from viral proteins, internalization might offer protection against antibody-dependent cell lysis. Here, the internalization and subsequent trafficking of the antigen-antibody complexes were characterized using biochemical, cell biological and genetic approaches. Internalization occurred through a clathrin- and caveolae-independent pathway that did not require dynamin, rafts, actin or rho-GTPases. These findings indicate that the viral antigen-antibody complexes were not internalized through any of the previously described pathways. Further characterization showed that this internalization process was independent from phosphatases and tyrosine kinases but did depend on serine/threonine kinases. After internalization, the viral antigen-antibody complexes passed through the early endosomes, where they resided only briefly, and accumulated in the late endosomes. Between 30 and 60 min after antibody addition, the complexes left the late endosomes but were not degraded in the lysosomes. This study reveals what is probably a new internalization pathway into primary monocytes, confirming once more the complexity of endocytic processes.
感染猫传染性腹膜炎病毒（FIPV，一种猫冠状病毒）后，尽管有强烈的体液免疫反应，仍常导致死亡。在之前的研究中，我们报道过，被感染的单核细胞作为FIPV在体内的靶细胞，会在其质膜上表达病毒蛋白。这些蛋白在与抗体结合后会迅速内化。随着细胞表面的病毒蛋白被清除，内化作用可能提供了针对抗体依赖性细胞裂解的保护。在此，我们使用生化、细胞生物学和遗传学方法对抗抗原-抗体复合物的内化及随后的运输进行了表征。内化作用通过一种不依赖网格蛋白和小窝的途径发生，该途径不需要发动蛋白、脂筏、肌动蛋白或rho-GTP酶。这些发现表明，病毒抗原-抗体复合物并非通过任何先前描述的途径内化。进一步的表征显示，这种内化过程独立于磷酸酶和酪氨酸激酶，但确实依赖于丝氨酸/苏氨酸激酶。内化后，病毒抗原-抗体复合物穿过早期内体，它们在早期内体中仅短暂停留，然后在晚期内体中积累。在添加抗体后30至60分钟之间，复合物离开晚期内体，但未在溶酶体中降解。这项研究揭示了一种可能是进入原代单核细胞的新内化途径，再次证实了内吞过程的复杂性。
