[show abstract][hide abstract] ABSTRACT: The ability of human cells to defend against viruses originating from distant species has long been ignored. Owing to the pressure of natural evolution and human exploration, some of these viruses may be able to invade human beings. If their 'fresh' host had no defences, the viruses could cause a serious pandemic, as seen with HIV, SARS (severe acute respiratory syndrome) and avian influenza virus that originated from chimpanzees, the common palm civet and birds, respectively. It is unknown whether the human immune system could tolerate invasion with a plant virus. To model such an alien virus invasion, we chose TMV (tobacco mosaic virus) and used human epithelial carcinoma cells (HeLa cells) as its 'fresh' host. We established a reliable system for transfecting TMV-RNA into HeLa cells and found that TMV-RNA triggered autophagy in HeLa cells as shown by the appearance of autophagic vacuoles, the conversion of LC3-I (light chain protein 3-I) to LC3-II, the up-regulated expression of Beclin1 and the accumulation of TMV protein on autophagosomal membranes. We observed suspected TMV virions in HeLa cells by TEM (transmission electron microscopy). Furthermore, we found that TMV-RNA was translated into CP (coat protein) in the ER (endoplasmic reticulum) and that TMV-positive RNA translocated from the cytoplasm to the nucleolus. Finally, we detected greatly increased expression of GRP78 (78 kDa glucose-regulated protein), a typical marker of ERS (ER stress) and found that the formation of autophagosomes was closely related to the expanded ER membrane. Taken together, our data indicate that HeLa cells used ERS and ERS-related autophagy to defend against TMV-RNA.
[show abstract][hide abstract] ABSTRACT: CD8(+) natural killer T (NKT) cells from EBV-associated tumour patients are quantitatively and functionally impaired. EBV-induced CD8(+) NKT cells drive syngeneic T cells into a Th1-bias response to suppress EBV-associated malignancies. IL-4-biased CD4(+) NKT cells do not affect either syngeneic T cell cytotoxicity or Th cytokine secretion. Circulating mDC1 cells from patients with EBV-associated malignancies impair the production of IFN-gamma by CD8(+) NKT cells. In this study, we have established a human-thymus-SCID chimaera model to further investigate the underlying mechanism of EBV-induced CD8(+) NKT cells in suppressing EBV-associated malignancies. In the human-thymus-SCID chimera, EBV-induced CD8(+) NKT cells suppress EBV-associated malignancies in a manner dependent on the Th1-bias response and syngeneic CD3(+) T cells. However, adoptive transfer with CD4(+) NKT cells alone inhibits T cell immunity. Interestingly, CD4(+) NKT cells themselves secrete high levels of IL-2, enhancing the persistence of adoptively transferred CD8(+) NKT cells and T cells, thereby leading to a more pronounced T cell anti-tumour response in chimaeras co-transferred with CD4(+) and CD8(+) NKT cells. Thus, immune reconstitution with EBV-induced CD4(+) and CD8(+) NKT cells synergistically enhances T cell tumour immunity, providing a potential prophylactic and therapeutic treatment for EBV-associated malignancies.