title: Virus-like particles of SARS-like coronavirus formed by membrane proteins from different origins demonstrate stimulating activity in human dendritic cells.
abstract: 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 (vAcBS) and the envelope (E) and membrane (M) proteins of SARS-CoV, respectively. Co-infection of insect cells with these two recombinant baculoviruses led to self-assembly of virus-like particles (BVLPs) as demonstrated by electron microscopy. Incorporation of S protein of vAcBS (BS) into VLPs was confirmed by western blot and immunogold labeling. Such BVLPs up-regulated the level of CD40, CD80, CD86, CD83, and enhanced the secretion of IL-6, IL-10 and TNF-alpha in immature dendritic cells (DCs). 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 stronger ability to stimulate DCs in terms of cytokine induction as evidenced by 2 to 6 fold higher production of IL-6 and TNF-alpha. Further study indicated that IFN-gamma+ and IL-4+ populations 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 response and a stronger T cell response 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 from SL-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. Finding in this study may provide important information for vaccine development as well as for understanding the pathogenesis of SARS-like CoV.
authors.affiliation: State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, People's Republic of China.
authors.forename: Bingke
authors.initials: B
authors.lastname: Bai
authors.forename: Qinxue
authors.initials: Q
authors.lastname: Hu
authors.forename: Hui
authors.initials: H
authors.lastname: Hu
authors.forename: Peng
authors.initials: P
authors.lastname: Zhou
authors.forename: Zhengli
authors.initials: Z
authors.lastname: Shi
authors.forename: Jin
authors.initials: J
authors.lastname: Meng
authors.forename: Baojing
authors.initials: B
authors.lastname: Lu
authors.forename: Yi
authors.initials: Y
authors.lastname: Huang
authors.forename: Panyong
authors.initials: P
authors.lastname: Mao
authors.forename: Hanzhong
authors.initials: H
authors.lastname: Wang
mesh_terms: D016367:Baculoviridae / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism; D002454:Cell Differentiation; D016207:Cytokines / Q000378:metabolism; D003713:Dendritic Cells / Q000166:cytology / Q000821:virology*; D006801:Humans; D007107:Immune System; D007371:Interferon-gamma / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000166:cytology; D008565:Membrane Proteins / Q000737:chemistry*; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D045473:Severe acute respiratory syndrome-related coronavirus / Q000378:metabolism*; D018417:Th1 Cells / Q000166:cytology
chemical_list: D016207:Cytokines; D008565:Membrane Proteins; D015847:Interleukin-4; D007371:Interferon-gamma