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. 1998 Jun;72(6):4931-9.

Induction of Systemic and Mucosal Immune Responses to Human Immunodeficiency Virus Type 1 by a DNA Vaccine Formulated With QS-21 Saponin Adjuvant via Intramuscular and Intranasal Routes

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Free PMC article

Induction of Systemic and Mucosal Immune Responses to Human Immunodeficiency Virus Type 1 by a DNA Vaccine Formulated With QS-21 Saponin Adjuvant via Intramuscular and Intranasal Routes

S Sasaki et al. J Virol. .
Free PMC article

Abstract

Induction of mucosal and cell-mediated immunity is critical for development of an effective vaccine against human immunodeficiency virus (HIV). We compared intramuscular and intranasal immunizations with a DNA vaccine encoding env of HIV-1 and evaluated the QS-21 saponin adjuvant for augmentation of the systemic and mucosal immune responses to HIV-1 in a murine model. Vaccination via the two routes elicited comparable systemic immune responses, and QS-21 consistently enhanced antigen-specific serum immunoglobulin G2a (IgG2a) production, delayed-type hypersensitivity reaction, and cytolytic activity of splenocytes. Intestinal secretory IgA production and cytolytic activity of the mesenteric lymph node cells are preferentially elicited by intranasal immunization, and QS-21 augmented these activities as well. This adjuvant augmented production of interleukin-2 (IL-2) and gamma interferon (IFN-gamma) associated with decrease in IL-4 synthesis by antigen-restimulated splenocytes. The serum immunoglobulin subtype profile showed a dominant IgG2a response and less strong IgG1 and IgE production in a QS-21 dose-dependent manner. As expected, enhancements of humoral and cell-mediated immune responses by QS-21 were abrogated by treatment with anti-IL-2 and anti-IFN-gamma monoclonal antibodies. These results suggest that the intranasal route of DNA immunization is more efficient than the intramuscular route in inducing mucosal immunity mediated by sIgA and mesenteric lymphocytes. Furthermore, QS-21 is able to act as a mucosal adjuvant in DNA vaccination and demonstrates its immunomodulatory property via stimulation of the Th1 subset. This study emphasizes the importance of the route of immunization and the use of an adjuvant for effective DNA vaccination against HIV-1.

Figures

FIG. 1
FIG. 1
HIV-1-specific antibody responses induced by DNA vaccination via the i.m. (A) and i.n. (B) routes. BALB/c mice were immunized with 5 μg of IIIB/REV formulated with the indicated doses of QS-21. Inoculation was performed twice with a 2-week interval. The HIV-1 env-specific antibody titers were determined by EIA in duplicate on samples collected 2 weeks following the second immunization. The results are expressed as means ± SEM for six (experimental group) or four (control group) mice. ∗, significant enhancement of the antibody response compared with IIIB/REV alone (P < 0.05). Similar results were obtained in a repeat experiment (not shown). N.D., not detected.
FIG. 2
FIG. 2
HIV-1-specific serum immunoglobulin subtype profiles induced by QS-21-mediated DNA vaccination via the i.m. (A) and i.n. (B) routes. The inoculation procedure and the time of blood collection were the same as those for Fig. 1. The subtype profile was determined by EIA and is presented as optical density at 450 nm. The results are expressed as means ± SEM for five or six (experimental group) or three or four (control group) mice. ∗ and #, significant enhancement or decrease in the antibody amount, respectively, compared with IIIB/REV alone (P < 0.05). Similar results were obtained in a repeat experiment (not shown).
FIG. 3
FIG. 3
DTH response induced by the V3 peptide (helper epitope of HIV-1IIIB). BALB/c mice were inoculated as described in the legend for Fig. 1. (A and B) Dose-related DTH reactions induced by the i.m. and i.n. immunizations, respectively. The DTH response was assayed by the footpad swelling test 2 weeks following the second immunization. For the test, mice were injected with V3 and the myoglobin peptide into the right and left footpads, respectively, and the swelling responses 24 h after the peptide injection were measured with a dial thickness gauge. The mean swelling responses ± SEM for five or six (experimental group) or four (control group) mice are given in 10−2 mm. ∗, significant enhancement of the swelling response compared with IIIB/REV alone (P < 0.05). Similar results were obtained in a separate experiment.
FIG. 4
FIG. 4
Cytolytic activity of the immune lymphoid cells harvested from animals receiving QS-21-mediated DNA vaccination as described in the legend to Fig. 1. (A to C) Cytolytic activities of splenic mononuclear cells from i.m.-immunized mice, splenic mononuclear cells from i.n.-immunized mice, and mesenteric lymphoid cells from i.n.-immunized mice, respectively. Splenocytes were harvested and cultured with the V3 peptide (a CTL epitope of HIV-1IIIB) for 5 days. Syngeneic cells (P815 cells; H-2d) pulsed with or without the same peptide were used as targets, and percent target cell lysis was determined by a 5-h 51Cr-releasing assay. The activity was titrated at E/T ratios of 5, 20, and 80. Nonspecific cytolytic activity (open bars) was measured at an E/T ratio of 80. The results were determined by duplicate assays and are presented as means ± SEM for three to six mice for each group.
FIG. 5
FIG. 5
Cytokine amounts in the culture media of the splenocytes harvested from the mice inoculated with the vaccine formulated as shown. Mice were treated as specified in the legend to Fig. 1, and the cells were also harvested at 2 weeks after the second immunization. These cells were cultured in the presence of the V3 peptide, and 48 h later, cell-free supernatants were collected and subjected to the cytokine enzyme-linked immunosorbent assay by using appropriate assay kits. The results were determined by a duplicate assay and are presented as means ± SEM for three and six mice for control and experimental groups, respectively.
FIG. 6
FIG. 6
Inhibition of DNA-derived humoral and cell-mediated immunity by treatment with anticytokine MAbs. (A to C) Influences of the antibodies on the serum antibody profile, DTH reaction, and cytolytic response, respectively. MAbs were intraperitoneally injected at 3- or 4-day intervals (twice per week) from the day of primary immunization until the day of assay. An anti-β-Gal MAb was used as a control antibody. (D) Inhibition of cytokine production by in vivo treatment with anticytokine MAbs. The procedure for determination of each response and mode of data presentation are identical to those for Fig. 2 to 5.

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