Objective:To investigate the influence of bacterial outer membrane vesicles (OMVs) tumor vaccine on tumor cell proliferation and CD8 + T cell infiltration of mouse with pancreatic cancer. Methods:The experimental study was conducted. The ovalbumin (OVA) lentivirus vector plasmid pLV-EF1a-hluc-P2A-mNeongreen-CMV-OVA-3Xflag-P2A-puro was used to construct the mouse pancreatic cancer Pan02-OVA cells. The ClyA-Catchers-OMVs (CC-OMVs) originated from Escherichia coli and labeled antigenic peptide SpyTag-OVA were used to construct the OMVs tumor vaccine. Mouse CD8 + T cells were stimulated by OMVs tumor vaccine, and the effects of OMVs tumor vaccine on inhibiting pancreatic cancer cells proliferation and stimulating CD8 + T cell infiltration were analy-zed by in vitro cell killing assay, including the OMVs tumor vaccine stimulated T cell group and the control T cell group, subcutaneous pancreatic cancer model, including the OMVs tumor vaccine group and the control group, and immunohistochemical staining. Observation indicators: (1) identification of mouse pancreatic cancer Pan02-OVA cells; (2) morphological observation of CC-OMVs; (3) inhibi-tion of mouse pancreatic cancer Pan02-OVA cells by OMVs tumor vaccine specific T cells; (4) inhibi-tion of mouse pancreatic cancer by OMVs tumor vaccine; (5) CD8 + T cell infiltration in pancreatic cancer tissue of mouse stimulated by OMVs tumor vaccine. Measurement data with normal distribu-tion were represented as Mean± SD, and comparison between groups was analyzed using the t test. Count data were described as absolute numbers or percentages. Results:(1) Identification of mouse pancreatic cancer Pan02-OVA cells. Results of laser scanning confocal microscopy showed that the mNeongreen fluorescence was expressed in Pan02-OVA cells infected with the OVA lentivirus vector plasmid of pLV-EF1a-hluc-P2A-mNeongreen-CMV-OVA-3Xflag-P2A-puro. Results of Flow cytometry showed that using the mouse pancreatic cancer Pan02 cells as references, the protein expression rate of Flag on the Pan02-OVA cells was 90.7%. (2) Morphological observation of CC-OMVs. Results of transmission electron microscopy analysis showed that the CC-OMVs were in spherical shape, with a diameter <50 nm. (3) Inhibition of mouse pancreatic cancer Pan02-OVA cells by OMVs tumor vaccine specific T cells. Results of cell proliferation toxicity test showed that the absorbance at 450 nm of mouse pancreatic cancer Pan02-OVA cells was 0.41±0.12 and 1.05±0.15 in the OMVs tumor vaccine-stimulated T cell group and the control T cell group, respectively, showing a significant difference between the two groups ( t=9.54, P<0.05). (4) Inhibition of mouse pancreatic cancer by OMVs tumor vaccine. The weight of subcutaneous tumor tissue in the back of mouse was (81±10)g and (153±17)g in the OMVs tumor vaccine group and the control group, respectively, showing a significant difference between the two groups ( t=8.26, P<0.05). (5) CD8 + T cell infiltration in pancreatic cancer tissue of mouse stimulated by OMVs tumor vaccine. Results of immuno-histochemical staining showed that the numbers of CD8 + T cells staining in the mouse back subcu-taneous tumor tissues was 28.7±3.5 and 9.3±1.5 in the OMVs tumor vaccine group and the control group, respectively, showing a significant difference between the two groups ( t=8.74, P<0.05). Conclusion:Bacterial OMVs tumor vaccine can inhibit proliferation of pancreatic cancer cells and increase the numbers of CD8 + T cells infiltrated in pancreatic cancer tissue of mouse.