Dynamic visualization of dendritic cell-antigen interactions in the skin following transcutaneous immunization.

Delivery of vaccines into the skin provides many advantages over traditional parenteral vaccination and is a promising approach due to the abundance of antigen presenting cells (APC) residing in the skin including Langerhans cells (LC) and dermal dendritic cells (DDC). However, the main obstacle for transcutaneous immunization (TCI) is the effective delivery of the vaccine through the stratum corneum (SC) barrier to the APC in the deeper skin layers. This study therefore utilized microneedles (MN) and a lipid-based colloidal delivery system (cubosomes) as a synergistic approach for the delivery of vaccines to APC in the skin. The process of vaccine uptake and recruitment by specific types of skin APC was investigated in real-time over 4 hours in B6.Cg-Tg (Itgax-EYFP) 1 Mnz/J mice by two-photon microscopy. Incorporation of the vaccine into a particulate delivery system and the use of MN preferentially increased vaccine antigen uptake by a highly motile subpopulation of skin APC known as CD207⁺ DC. No uptake of antigen or any response to immunisation by LC could be detected.

Transcutaneous immunization using microneedles and cubosomes: Mechanistic investigations using Optical Coherence Tomography and Two-Photon Microscopy.

Transcutaneous (TCI) immunization is a novel vaccination approach that provides many advantages over traditional parenteral vaccination. However, a major barrier to TCI is mediating penetration of vaccine antigens through the stratum corneum (SC) to the deeper tissue layers. Many approaches have been investigated for enhancing drug penetration into the skin including microneedles (MNs) to transiently breach the SC barrier and incorporation of vaccines into penetration-enhancing delivery systems. This study utilized MNs and a lipid-based colloidal delivery system (cubosomes) as a synergistic approach for the delivery of vaccines through the skin. The penetration and permeation of the peptide antigen into and through skin were analysed quantitatively and qualitatively using techniques including Optical Coherence Tomography and two-photon microscopy. It was found that while the use of MNs increased the permeation of an aqueous peptide mixture through skin, cubosome-formulated peptide and cubosomes were retained in the skin. Therefore, it is proposed that a combined approach using MNs and cubosomes will be an efficient system for the local delivery of antigen to immunocompetent cells in the skin.

Comparative study of liposomes, transfersomes, ethosomes and cubosomes for transcutaneous immunisation: characterisation and in vitro skin penetration.

OBJECTIVES: Lipid colloidal vaccines, including liposomes, transfersomes, ethosomes and cubosomes, were formulated, characterised and investigated for their ability to enhance penetration of a peptide vaccine through stillborn piglet skin in vitro. METHODS: Liposomes and transfersomes were formulated using a film-hydration method, ethosomes using a modified reverse phase method and cubosomes using a lipid precursor method. The size, zeta potential, peptide loading and interfacial behaviour of the formulations were characterised. Skin penetration studies were performed using Franz diffusion cells with piglet skin as the membrane. The localization of peptide in the skin was examined using confocal laser scanning microscopy. KEY FINDING: The various formulations contained negatively charged particles of similar size (range: 134-200 nm). Addition of the saponin adjuvant Quil A to the formulations destabilised the monolayers and reduced peptide loading. Cubosomes and ethosomes showed superior skin retention compared with the other systems. Confocal laser scanning microscopy showed greater peptide penetration and accumulation in the skin treated with cubosomes and ethosomes. With the other systems peptide was only located in the vicinity of the hair follicles and within the hair shaft. CONCLUSIONS: We conclude from the in-vitro studies that cubosomes and ethosomes are promising lipid carriers for transcutaneous immunisation.