Figure 3: Comparison of maximal antibody titers following low-volume jet injection (0.35 ± 0.13) and particle bombardment (0.33 ± .05) at a 1:250 serum dilution. Maximal antibody titers are defined as the highest antibody titer that was measured in each individual rabbit. Mean ± S.E is shown. There was no significant difference in maximal antibody titers between the two methods (ANOVA, P = 0.875).

Mentions: Injections of plasmid DNA encoding the Hepatitis B Surface Antigen (HBSAg) were performed at Days 0, 14 and 28. Antibody titers were determined prior to any injection (Day 0), two weeks after each of the three injections (Days 14, 28, and 42), and four weeks after the third and final injection (Day 56). By days 14 and 28 two of five rabbits immunized by low-volume jet injection demonstrated a statistically significant and titratable response at serial time points that persisted through day 56 (Figure 2A) (ANOVA, P = 0.009 at the 1:250 dilution; P = 0.003 at the 1:2,500 dilution at day 56). The number of injections before response and the maximal antibody responses were comparable to rabbits that received DNA immunization by particle bombardment. By days 14 (1) and 42 (2) three of five rabbits immunized by particle bombardment demonstrated a statistically significant response at serial time points (Figure 2B). One rabbit expired during anesthesia at the day 28-injection time point. At day 56 the immune response was statistically significant only at the 1:250 dilution in the two remaining rabbits (ANOVA, P < 0.001 at the 1:250 dilution; P = 0.609 at the 1:2,500 dilution). There was no statistically significant difference in maximal antibody titers between low-volume jet injection and particle bombardment (ANOVA, P = 0.875) (Figure 3). In contrast to immunization with either low-volume jet or particle bombardment, there was no significant titratable antibody response in rabbits that received DNA immunization by needle and syringe injection (ANOVA, P = 0.062 at the 1:250 dilution; P = 0.140 at the 1:2,500 dilution at day 56). Longer-term experiments and larger groups of rabbits will be required to determine if persistence of antibody is different between the low-volume jet injected and particle bombardment groups.

Ren S, Li M, Smith JM, DeTolla LJ, Furth PA - BMC Biotechnol. (2002)

Bottom Line: There were no significant differences between jet injection and particle bombardment in the maximal antibody titers or number of injections before response.In the jet injection and particle bombardment groups, gene expression levels in the skin did not predict response.While immune responses were similar, luciferase gene expression levels in the skin following particle bombardment were 10-100 times higher than jet injection.Low-volume jet injection is a simple, effective methodology for intradermal DNA immunization.

Affiliation: Department of Oncology, Lombardi Cancer Center, Georgetown University, 3970 Reservoir Rd, NW, Washington, DC 20007, USA. rs94@georgetown.edu

Abstract: This study tested a low-volume (20-30 microl/20-30 microg DNA) jet injection method for intradermal delivery of a DNA vaccine. Jet injection offers the advantages of a needle-less system, low-cost, rapid preparation of the injected DNA solution, and a simple delivery system. More than one construct can be injected simultaneously and the method may be combined with adjuvants.Low-volume jet injection targeted delivery of a DNA solution exclusively to the dermis and epidermis of rabbits. A three injection series of plasmid DNA, encoding the Hepatitis B Surface Antigen stimulated a humoral immune response in 2/5 rabbits. One rabbit developed a significant rise in antibody titer after 1 injection and one following 2 injections. There were no significant differences between jet injection and particle bombardment in the maximal antibody titers or number of injections before response. A three injection series of the same plasmid DNA by particle bombardment elicited a significant rise in antibody titer in 3/5 rabbits. One rabbit developed antibody after 1 injection and two after 3 injections. In contrast, 0/5 rabbits receiving DNA by needle and syringe injection responded. In the jet injection and particle bombardment groups, gene expression levels in the skin did not predict response. While immune responses were similar, luciferase gene expression levels in the skin following particle bombardment were 10-100 times higher than jet injection.Low-volume jet injection is a simple, effective methodology for intradermal DNA immunization.