Dose sparing and enhanced immunogenicity of inactivated rotavirus vaccine administered by skin vaccination using a microneedle patch

Abstract

Skin immunization is effective against a number of infectious diseases, including smallpox and tuberculosis, but is difficult to administer. Here, we assessed the use of an easy-to-administer microneedle (MN) patch for skin vaccination using an inactivated rotavirus vaccine (IRV) in mice. Female inbred BALB/c mice in groups of six were immunized once in the skin using MN coated with 5 μg or 0.5 μg of inactivated rotavirus antigen or by intramuscular (IM) injection with 5 μg or 0.5 μg of the same antigen, bled at 0 and 10 days, and exsanguinated at 28 days. Rotavirus-specific IgG titers increased over time in sera of mice immunized with IRV using MN or IM injection. However, titers of IgG and neutralizing activity were generally higher in MN immunized mice than in IM immunized mice; the titers in mice that received 0.5 μg of antigen with MN were comparable or higher than those that received 5 μg of antigen IM, indicating dose sparing. None of the mice receiving negative-control, antigen-free MN had any IgG titers. In addition, MN immunization was at least as effective as IM administration in inducing a memory response of dendritic cells in the spleen. Our findings demonstrate that MN delivery can reduce the IRV dose needed to mount a robust immune response compared to IM injection and holds promise as a strategy for developing a safer and more effective rotavirus vaccine for use among children throughout the world.

Keywords: IRV; Microneedle; Rotavirus; Skin immunization.

Fig. 1

Stability and antigenicity of inactivated rotavirus particles coated on MN. A: Electron micrographs of inactivated CDC-9 IRV particles before coating (left) and after reconstitution from MN one day after coating (right). Triple-layered CDC-9 particles were stained with phosphotungstic acid and examined with an electron microscope. Bar = 100 nm. The central image shows two MN devices each with a row of five MN (circle shows a five-MN array). B: Levels of rotavirus antigen detected in original and reconstituted preparations by EIA. Similar levels of absorbance in original and reconstituted CDC9 preparations were observed. A blank was tested as a negative control.

Fig. 2

Phenotype and maturation of DCs in the spleens of mice that received IRV by MN and IM administration. Splenocytes were stimulated with rotavirus, purified for DCs, and examined for the expression of surface and co-stimulatory markers CD11c, CD80 and CD86 as described in the text. A: Representative FACS plots showing the phenotype and maturation expressing CD80 and CD86 of mDCs in the spleens of mice 28 days after receiving 5 µg of IRV using a MN patch, following in vitro stimulation with rotavirus. B and C: Proportions of activated mDCs with CD80 or CD86 expression in stimulated splenocytes of mice 28 days after receiving IRV by MN or IM administration. The character “*” indicates IRV reconstituted from coated MN.

Fig. 3

Rotavirus-specific IgG (A) and neutralizing activity (B) in sera of vaccinated mice. Mice (n = 6 per group) were immunized with MN coated with 5 µg, 0.5 µg, or 0 µg (mock) of IRV or by IM injection with 5 µg or 0.5 µg of IRV, or 5 µg of IRV reconstituted from coated MN. Serum samples collected at days 0, 10 and 28 after vaccination were analyzed for IgG and sera collected on day 28 were examined for neutralizing activity as described in the text. The character “*” indicates IRV reconstituted from coated MN. Error bars show standard deviation.

Fig. 4

IgG subclasses IgG1 (A) and IgG2a (B) in sera of mice that received IRV by MN or IM administration. Pooled sera on day 28 were tested by EIA for IgG1 and IgG2a as described in the text. Data showing the ratio of IgG2a and IgG1 are shown in panel C. The character “*” indicates IRV reconstituted from coated MN.