Intradermal vaccination via microneedles

Abstract

The vaccine has been used as a biological preparation against many infectious diseases such as influenza. After the vaccine was developed by E. Jenner, the dramatically improvement of vaccine has been achieved. Moreover, that improvement provided the higher quality of life and eradication of several infectious diseases such as smallpox and measles. However, there are still many disease, such as HIV, which are uncovered by vaccination. The vaccinations are separated by the type of antigens, excipients, and delivery tools. This paper focused on the novel delivery tool, microneedle, to improve the vaccination efficacy. Most of the traditional vaccinations have been used a hypodermic syringe. However, the vaccination by syringe induced pain, fear and stress. Moreover, the invasion or reuse of the needle of syringe could induce blood-borne infections. To solve those disadvantages of traditional vaccination systems, the novel vaccination systems have been developed. For example, mucosal vaccination targets the mucosal tissues through the nasal, sublingual, pulmonary, ocular and gastrointestinal routes. The other example, transcutaneous immunization, targets epidermis and dermis of the skin using liquid jet and epidermal powder injections. Both two novel vaccination systems showed improved immunogenicity and induction of protective immune response. In this paper, the intradermal vaccination system was used via vaccine coated microneedles. An array of 5 micrometer-sized stainless steel needles was mainly used in this paper. Because of their small invasion size, the microneedle array dose not induce the pain. Therefore, the microneedle system provides remarkably improved the patient compliance and safety from blood-borne infections. Furthermore, it provides an improvement in immunogenicity, because it delivers the vaccine into the skin, which have high density of immune cells. Microneedles are classified into 4 types-solid, coated, dissolving and hollow microneedles-according to antigen delivery types. Among them, the coated microneedle system was used in this research. This study was performed to find more optimized coating formulation for stainless steel microneedles against influenza A (H1N1) virus. The conventional formulation was a combination of carboxymethylcellulose sodium salt and trehalose as viscosity enhancer and stabilizer. We screened formulations using different viscosity enhancers and stabilizers. Finally, two formulations were selected and our two new formulations showed significantly more stable vaccine condition at room temperature for 3 months. Moreover, they elicited superior immune responses comparing with conventional formulation in mouse model.