Antibody study in canine distemper virus nucleocapsid protein gene-immunized mice

The gene for the nucleocapsid (N) protein of canine distemper virus was cloned into the pMD-18T vector, and positive recombinant plasmids were obtained by enzyme digestion and sequencing. After digestion by both EcoRI and KpnI, the plasmid was directionally cloned into the eukaryotic expression vector pcDNA; the positive clone pcDNA-N was screened by electrophoresis and then transfected into COS-7 cells. Immunofluorescence analysis results showed that the canine distemper virus N protein was expressed in the cytoplasm of transfected COS-7 cells. After emulsification in Freund's adjuvant, the recombinant plasmid pcDNA-N was injected into the abdominal cavity of 8-week-old BABL/c mice, with the pcDNA original vector used as a negative control. Mice were immunized 3 times every 2 weeks. The blood of immunized mice was drawn 2 weeks after completing the immunizations to measure titer levels. The antibody titer in the pcDNA-N test was 10(1.62 ± 0.164), while in the control group this value was 10(0.52 ± 0.56), indicating that specific humoral immunity was induced in canine distemper virus nucleocapsid protein-immunized mice.