Epidermal immunization by a needle-free powder delivery technology: Immunogenicity of influenza vaccine and protection in mice

Abstract

Human vaccines are typically injected into muscle despite its inconsequential function in the induction of subsequent immune responses. In contrast, skin, a potent immunological induction site, is rarely used for vaccination because of its poor accessibility by needle and its poor permeability to topically applied vaccines. When special delivery systems are used, administering vaccines to the skin is very efficacious. Vaccination with a live attenuated vaccine by skin scarification led to global eradication of the deadly smallpox disease 1,2 . Particle-mediated DNA immunization to the skin requires 0.4-4% the DNA required for intramuscular injection 3,4 .Human skin consists of an epidermis of columnar epithelium and a dermis of fibrous connective tissue. The keratinized epidermal cells with their tight conjunction form the stratum corneum that prevents molecules of 500 Da or greater to penetrate 5,6 . The underlying viable epidermis, with its dense network of antigen-presenting cells (Langerhans cells) and relative lack of sensory nerve endings, has long been recognized as a safe and effective target tissue for vaccination 7 . However, the epidermis is too thin for needle injection. Topical application of protein antigens can result in an immune response, although high antigen dose and toxic adjuvant may be required 8-10 . Here we describe a new technology, epidermal powder immunization (EI), that effectively delivers powdered vaccines to the viable epidermis by using a heliumpowered, needle-free PowderJect system. EI induced serum antibody response to the influenza vaccines and provided protection against homologous and heterologous challenge in a mouse challenge model. Powder delivery systemThe helium-powered PowderJect device for delivering powdered vaccines has been described 11,12 . The device used here was a reusable research model 15 cm in length with an 'actuation' button, a helium gas chamber, a vaccine cassette, a nozzle and a 'silencer' (Fig. 1). The stainless steel gas chamber was filled with approximately 5 ml medical-grade helium gas to a pressure of 50 bar. When the device was activated, the released helium gas ruptured the membranes of the trilaminate cassette and accelerated the entrapped vaccine powders to a high speed so that the particles perforated the stratum corneum and landed in the epidermis. The helium gas was reflected off the skin and was 'exhausted' through the vented silencer. Comparison of EI and needle injectionAlthough the intramuscular route is commonly used for administering human vaccines, subcutaneous, intraperitoneal and intramuscular routes are often used interchangeably for immunizing experimental animals such as mice. To compare EI with needle injection through these conventional routes, we used a formalin-inactivated Aichi/68 influenza virus to immunize BALB/c mice (n = 8 per group). For EI, the vaccine was formulated with trehalose into a powder with microscopic particles 20-53 µm in diameter. We administered 1 mg powder containing 5 µg vaccine (total viral protein) to t...

Enabling topical immunization via microporation: a novel method for pain-free and needle-free delivery of adenovirus-based vaccines

“…However, protein-based and conventional flu vaccines have recently been formulated for gene-gun mediated delivery resulting in CTL responses which are not normally produced by standard inoculation of these vaccines. 8,28 Whether or not live vaccines (eg rdAd) can Figure 8 Growth of B16 tumors following immunization with AdhTRP-2 applied to microporated skin. AdhgTRP-2 (5 Â 10 6 pfu/ml) was applied to both microporated and intact skin of C57Bl/6 mice two times, 21 days apart.…”

“…Other devices that are being developed to deliver vaccines to the epidermis include, ballistic particle delivery ('gene gun'), microprojections, electroporation and liquid jet injectors. [7][8][9][10] There are no clear criteria at this point to identify the optimal device for epidermal delivery, however, the flexibility, reproducibility, and ease of use of the microporation technology makes it highly attractive for this application.…”

Targeting epidermal Langerhans cells by epidermal powder immunization

“…EPI has its roots in a technology that was developed in the early1990s for genetically engineering plants and then was adapted for DNA immunization [41][42][43]. EPI delivers antigens in the form of microscopic particles to the epidermis using a needle-free powder delivery system (or PowderJect device) and elicits broad immune responses [44]. Here we will review our findings using this technology to deliver traditional vaccines in relation to LC targeting and its potential applications in the prevention and treatment of infectious diseases and immune disorders.…”

“…Many traditional vaccines such as proteins, peptides, polysaccharides, inactivated pathogens etc are suitable for EPI [44][45][46][47]. Vaccine powders can be prepared by coating antigens onto 1-2 mm gold particles or embedding them into 20-50 mm particles using sugar excipients (trehalose, mannitol, sucrose, or combinations) [44], [47].…”

“…Vaccine powders can be prepared by coating antigens onto 1-2 mm gold particles or embedding them into 20-50 mm particles using sugar excipients (trehalose, mannitol, sucrose, or combinations) [44], [47]. The driving force of the device is pressured helium gas.…”