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Volume 49, Number 6, December 2016

Heterologous expression of carcinoembryonic antigen in Lactococcus lactis via LcsB-mediated surface displaying system for oral vaccine development 

Xiaowei Zhang, Shumin Hu, Xue Du, Tiejun Li, Lanlan Han, Jian Kong


Corresponding author:

Jian Kong 


Background and purpose: 

Carcinoembryonic antigen (CEA) is an attractive target for immunotherapy because it is expressed minimally in normal tissue, but is overexpressed in a wide variety of malignant epithelial tissues. Lactic acid bacteria (LABs), widely used in food processes, are attractive candidates for oral vaccination. Thus, we examined whether LABs could be used as a live vaccine vector to deliver CEA antigen. 



CEA was cloned into an Escherichia coli/Lactococcus lactis shuttle vector pSEC:LEISS under the control of a nisin promoter. For displaying the CEA on the cell surface of the L. lactis strain, the anchor motif LcsB from the S-layer protein of Lactobacillus crispatus was fused with CEA. Intracellular and cell surface expression of the CEA–LcsB fusion was confirmed by western blot analysis. 



Significantly higher levels of CEA-specific secretory immunoglobulin A in the sera of mice were observed upon oral administration of strain cultures containing the CEA–LcsB fused protein. In addition, the CEA–LcsB antigen group showed a higher spleen index compared to the CEA antigen alone or negative control, demonstrating that surface-displayed CEA antigen could induce a higher immune response. 



These results provided the first evidence for displaying CEA antigen on the cell surfaces of LABs as oral vaccines against cancer or infectious diseases. 


Key words:

carcinoembryonic antigen, gene expression, Lactococcus lactis, S-layer