Abstract:

BACKGROUND: Tumor necrosis factor-α (TNF-α) is one of important cytokines to promote the maturation of dendritic cells. Blockage of TNF-α action by binding with soluble tumor necrosis factor receptor 1 (sTNFR1) may arrest dendritic cells in an immature state and induce stable, long-term tolerance.
OBJECTIVE: To construct the lentiviral vectors carrying sTNFR1 gene and investigate sTNFR1 expression in immature dendritic cells. 
METHODS: Total RNA of human peripheral blood mononuclear cells was taken as a template. The sTNFR1 gene fragment was amplified by RT-PCR, subcloned to the lentiviral vectors pXZ208, and ligated to the enhanced green fluorescent protein (eGFP) reporter gene to establish lentiviral vector, called pXZ9-sTNFR1. DNA sequencing was performed for lentiviral vector identification. Lentivirus was prepared by transfection of 293 FT cells with pXZ9-sTNFR1. Viral titer was determined by eGFP expression. C57BL/6 mouse bone marrow-derived dendritic cells were in vitro cultured with low-dose granulocyte-macrophage colony stimulating factors and interleukin 4. On day 5 of culture, immature dendritic cells were transfected with pXZ9-sTNFR1 recombinant lentiviral supernatant. sTNFR1 transcription was detected by RT-PCR, sTNFR1 protein expression by Western blot analysis. Following sTNFR1 gene modification and lipopolysaccharide stimulation, the phenotype characteristics of dendritic cells were observed.
RESULTS AND CONCLUSION: Recombinant plasmid pXZ9-sTNFR1 was successfully constructed. Twenty-four hours after 293 FT cell transfection, eGFP expression was observed and viral titer was over 106 U/L. RT-PCR demonstrated that pXZ9-sTNFR1-transfected immature dendritic cells showed sTNFR1 positive expression. Western blot analysis revealed that sTNFR1 protein appeared in the immature dendritic cells and supernatant following 293 FT cell transfection. On day 5 of culture, dendritic cells expressed low level of class Ⅱ major histocompatibility complex (MHC Ⅱ), as well as CD40, CD86, CD80, molecules. However, following lipopolysaccharide stimulation, dendritic cells expressed high level of MHC II, as well as CD40, CD80, and CD86, molecules, exhibiting the phenotype characteristics of mature dendritic cells. But after sTNFR modification, the expression level of MHC II, as well as CD40, CD80, and CD86, molecules was not altered obviously. Lentiviral vectors carrying sTNFR1 gene and eGFP reporter gene were successfully constructed, and recombinant lentiviral plasmids with high titer were acquired. Following high efficacy of lentiviral gene transfection, immature dendritic cells stably express sTNFR1 mRNA and protein, which prevents immature dendritic cells from activation by exogenous lipopolysaccharide and maintains the immature state.