The pathogenesis of SARS coronavirus (CoV) remains poorly understood. In the current study, two recombinant baculovirus were generated to express the spike (S) protein of SARS-like coronavirus (SL-CoV) isolated from bats (cAcBS) and the envelop (E) and membrane (M) proteins of SARS-CoV, respectively. Co-infection of insects cells with these two recombinant baculoviruses led to self-assembly of virus-like particles (BVLPs) as demonstrated bu electron microscopy. Incorporation of S protein of vAcBS (BS) into VLPs was confirmed by western blot and immunogold labelling. Such BVLPs up-regulated the level of CD40, CD80, CD86, CD83, and enhanced the secretion of IL-10 and TNF-α in immature dendritic cells (CDs). Immune responses were compared in immature DCs inoculated with BVLPs or with VLPs formed by S, E and M proteins of human SARS-CoV. BVLPs showed a stonger ability to stimulated DCs in terms of cytokine induction as evidenced by 2 to 6 fold higher production of IL-6 and TNF-α. Further study indicated that IFN-γ+ and IL-4+ population in CD4+ T cells increased upon co-cultivation with DCs pre-exposed with BVLPs or SARS-CoV VLPs. The observed difference in DC-stimulating activity between BVLPs and SARS CoV VLPs was very likely due to the S protein. In agreement, SL-CoV S DNA vaccine evoked a more vigorous antibody responce and a stronger T cell responce than SARS-CoV S DNA in mice. Our data have demonstrated for the first time that SL-CoV VLPs formed by membrane proteins of different origins, one fromSL-CoV isolated from bats (BS) and the other two from human SARS-CoV (E and M), activated immature DCs and enhanced the expression of co-stimulatory molecules and the secretion of cytokines. Findings in this study may provide important information for vaccine development as well as for understanding the pathogenesis of SARS-like CoV. © 2008 Bai et al.
Bai, B., Hu, Q., Hu, H., Zhou, P., Shi, Z., Meng, J., … Wang, H. (2008). Virus-like particles of SARS-like coronavirus formed by membrane proteins from different origins demonstrate stimulating activity in human dendritic cells. PLoS ONE, 3(7). https://doi.org/10.1371/journal.pone.0002685