Intranasal priming with HIV DNA vaccine and systemic boosting with recombinant vaccinia induce vigorous immune responses: experiment with mice

Abstract

To explore the strategy to raise both mucosal and systemic anti-HIV-1 immunity. Eighteen BALB/c rats were randomly divided into 2 groups, experimental group and control group. The experimental group were further subdivided into 4 subgroups of 3 mice: 3-dose HIV DNA vaccine group, 3-dose DNA vaccine + cholera toxin (CT) adjuvant subgroup, 1-dose recombinant Tiantan strain vaccinia-based vaccine subgroup, and 3-dose DNA vaccine + CT adjuvant + Tiantan strain vaccinia-based vaccine subgroup. The control group was subdivided into 2 subgroups of 3 mice: 3-dose DNA blank vector subgroup, and 3-dose DNA blank vector + Tiantan strain vaccinia-based vaccine subgroup. Intranasal administration of DNA vaccine-based vaccine (10 microg) was done on the days 0, 14, and 28 as the mucosal priming, and recombinant Tiantan vaccinia (1 x 10(7) PFU) was injected intramuscularly as systemic boosting on the day 42. On the day 56 the mice were killed and specimens of serum, nasopharynx wash, lung wash, and spleen were collected and splenocytes were isolated. Splenocytes were added into the phosphate-buffered saline with anti-mouse interferon-gamma (IFN-gamma) envelop antibody to count the number of spot-forming cells (SFCs). Indirect ELISA was used to detect the HIV-1 specific antibody in the nasopharynx wash and lung wash. Immunohistochemistry was used to detect the intracellular staining of IFN-gamma in the splenocytes. The number of spot forming cells in the HIV-1 DNA vaccine + CT adjuvant group was (14 +/- 11) SFCs/10(6) splenocytes, significantly more than that of the HIV-1 DNA vaccine group [(2 +/- 1) SFCs/10(6) spleen cells (P < 0.01). The number of SFCs of the 1-dose DNA-vaccine subgroup was [(30 +/- 18) SFCs/10(6) spleen cells], significantly higher than that of the only DNS vaccine group (P < 0.01). The number of SFCs of DNA vaccine + CT adjuvant + recombinant Tiantan vaccinia-based vaccine was (61 +/- 35) SFCs/10(6) splenocytes, significantly higher than those of the other groups (all P < 0.01). Flow cytometry showed that the rate of HIV-1 Gag specific CD8(+) T cell was 1.8% +/- 1.4%. The value of specific IgG of the DNA vaccine + adjuvant + Tiantan vaccinia-based vaccine was 1.50 +/- 0.30, significantly higher than those of the blank vector, single-dose Tiantan vaccinia-based vaccine, and single-dose DNA vaccine + CT adjuvant subgroups (0.42 +/- 0.02, 0.74 +/- 0.13, and 0.75 +/- 0.02 respectively, all P < 0.05). In different subgroups the levels of specific IgA in the lung wash were all higher than those in the nasopharynx wash. The levels of specific IgA in the lung and nasopharynx wash of the DNA vaccine + CT adjuvant subgroup were higher than those of the other subgroups whether or not with boosting of Tiantan. The specific IgA levels of the groups enhanced by Tiantan vaccinia-based vaccine were all significantly higher than those of the corresponding subgroups without enhancement (all P < 0.01). The IgA level of lung wash of the DNA vaccine + CT adjuvant subgroup was 1.82 +/- 0.76, significantly higher than that of the one-dose Tiantan vaccinia-based vaccine group (0.52 +/- 0.19, P < 0.05). The vaccination modality of mucosal priming and systemic boosting induces both mucosal and systemic immune responses.