Host responses in human skin after conventional intradermal injection or microneedle administration of virus-like-particle influenza vaccine.

Miniaturized microneedle devices are being developed for painlessly targeting vaccines to the immune cell populations in skin. As skin immunization studies are generally restricted to animal models however, where skin architecture and immunity is greatly different to human, surprisingly little is known about the local human response to intradermal (ID) vaccines. Here surgically excised human skin is used to explore for the first time the complex molecular and cellular host responses to a candidate influenza vaccine comprising nanoparticulate virus-like-particles (VLPs), administered via conventional hypodermic injection or reduced scale microneedles.

Microneedle delivery of plasmid DNA to living human skin: Formulation coating, skin insertion and gene expression.

Microneedle delivery of nucleic acids, in particular plasmid DNA (pDNA), to the skin represents a potential new approach for the clinical management of genetic skin diseases and cutaneous cancers, and for intracutaneous genetic immunisation. In this study excised human skin explants were used to investigate and optimise key parameters that will determine stable and effective microneedle-facilitated pDNA delivery. These include (i) high dose-loading of pDNA onto microneedle surfaces, (ii) stability and functionality of the coated pDNA, (iii) skin penetration capability of pDNA-coated microneedles, and (iv) efficient gene expression in human skin.

Changes in human Langerhans cells following intradermal injection of influenza virus-like particle vaccines.

There is a significant gap in our fundamental understanding of early morphological and migratory changes in human Langerhans cells (LCs) in response to vaccine stimulation. As the vast majority of LCs studies are conducted in small animal models, substantial interspecies variation in skin architecture and immunity must be considered when extrapolating the results to humans. This study aims to determine whether excised human skin, maintained viable in organ culture, provides a useful human model for measuring and understanding early immune response to intradermally delivered vaccine candidates.

Influenza virus-like particles coated onto microneedles can elicit stimulatory effects on Langerhans cells in human skin.

Virus-like particles (VLPs) have a number of features that make them attractive influenza vaccine candidates. Microneedle (MN) devices are being developed for the convenient and pain-free delivery of vaccines across the skin barrier layer. Whilst MN-based vaccines have demonstrated proof-of-concept in mice, it is vital to understand how MN targeting of VLPs to the skin epidermis affects activation and migration of Langerhans cells (LCs) in the real human skin environment.

Microneedle delivery of H5N1 influenza virus-like particles to the skin induces long-lasting B- and T-cell responses in mice.

A simple method suitable for self-administration of vaccine would improve mass immunization, particularly during a pandemic outbreak. Influenza virus-like particles (VLPs) have been suggested as promising vaccine candidates against potentially pandemic influenza viruses, as they confer long-lasting immunity but are not infectious. We investigated the immunogenicity and protective efficacy of influenza H5 VLPs containing the hemagglutinin (HA) of A/Vietnam/1203/04 (H5N1) virus delivered into the skin of mice using metal microneedle patches and also studied the response of Langerhans cells in a human skin model.

In vivo, in situ imaging of microneedle insertion into the skin of human volunteers using optical coherence tomography.

Purpose: To gather sub-surface in situ images of microneedle-treated human skin, in vivo, using optical coherence tomography (OCT). This is the first study to utilise OCT to investigate the architectural changes that are induced in skin following microneedle application.

Methods: Steel, silicon and polymer microneedle devices, with different microneedle arrangements and morphologies, were applied to two anatomical sites in human volunteers following appropriate ethical approval.

Development of an ex vivo human skin model for intradermal vaccination: tissue viability and Langerhans cell behaviour.

The presence of resident Langerhans cells (LCs) in the epidermis makes the skin an attractive target for DNA vaccination. However, reliable animal models for cutaneous vaccination studies are limited. We demonstrate an ex vivo human skin model for cutaneous DNA vaccination which can potentially bridge the gap between pre-clinical in vivo animal models and clinical studies.

Gene delivery to the epidermal cells of human skin explants using microfabricated microneedles and hydrogel formulations.

Purpose: Microneedles disrupt the stratum corneum barrier layer of skin creating transient pathways for the enhanced permeation of therapeutics into viable skin regions without stimulating pain receptors or causing vascular damage. The cutaneous delivery of nucleic acids has a number of therapeutic applications; most notably genetic vaccination. Unfortunately non-viral gene expression in skin is generally inefficient and transient.

Cutaneous DNA delivery and gene expression in ex vivo human skin explants via wet-etch micro-fabricated micro-needles.

Micro-needle arrays increase skin permeability by forming channels through the outer physical barrier, without stimulating pain receptors populating the underlying dermis. It was postulated that micro-needle arrays could facilitate transfer of DNA to human skin epidermis for cutaneous gene therapy applications. Platinum-coated "wet-etch" silicon micro-needles were shown to be of appropriate dimensions to create micro-conduits, approximately 50 microm in diameter, extending through the stratum corneum (SC) and viable epidermis.