[The humoral immune response in mice induced by recombinant Lactococcus lactis expressing HIV-1 gag]

To analyze the humoral immune response induced by recombinant Lactococcus lactis expressing HIV-1 gag in mice immunized orally, intranasally, subcutaneously or in the combined way of above three.

Fifty BALB/c mice were randomly divided into 5 groups, 10 mice per group. The mice were immunized consecutively three times at two week intervals with 10(9) CFU of recombinant Lactococcus lactis expressing gag through oral, intranasal, subcutaneous administration or the mix of them. The mice that were immunized orally with Lactococcus lactis containing PMG36e served as a control group. The sera of mice were collected before primary immunization and 2 weeks after each immunization to detect the gag specific IgG by ELISA.

Compared with the control group, the higher titer of serum gag specific IgG was detected in the four groups immunized with recombinant Lactococcus lactis expressing gag, and it was the highest in the mixed immunization group (P<0.01). The titer of serum gag specific IgG from the oral and subcutaneous immunization groups was significantly higher than that from the intranasal immunization group (P<0.01) 6 weeks after primary immunization . The serum antibody positive rates of the oral immunization group after the first, the second, the third immunization were 40%, 40%, 90%, respectively; the positive rates of the intranasal immunization group were 10%, 20%, 20%; the positive rates of the subcutaneous immunization group were 10%, 60%, 90%; the positive rate of the combined immunization group reached 100% 2 weeks after primary immunization.

Recombinant Lactococcus lactis expressing gag can induce humoral immune response in mice by oral, intranasal, subcutaneous injection or the mix of them, and the mixed immunization can enhance the immune effects of Lactococcus lactis vector vaccine.