Topical delivery of vaccines

#This invention relates to topical delivery of substances into the skin, particularly by disruption of the stratum corneum and delivery of the substance to the epidermal layer beneath.

#Delivery of substances to the body through the skin has typically been invasive, involving needles and syringes to facilitate intradermal (ID), intramuscular (IM) or subcutaneous (SC) injection. These methods are painful for the subject, quire the skills of a trained practitioner and often produce bleeding. There have more recently been efforts to overcome these disadvantages by use of devices which disrupt or abrade the stratum corneum, the thin external layer of keratinized cells about 10-20 μm thick which serves as the skin's outer barrier, with delivery of the desired substance to the exposed epidermis. The substance can then diffuse through the epidermis to the dermis which contains blood vessels and lymphatics for absorption and delivery of the substance throughout the body. For topical delivery of vaccines, the epidermis itself is a particularly desirable target for drug delivery as it is rich in antigen presenting cells. In comparison, the dermis contains fewer antigen presenting cells. The stratum corneum and epidermis do not contain nerves or blood vessels, so this method has the advantage of being essentially painless and blood-free while giving access to the skin layers capable of responding to the antigen.

#The prior art reports a variety of devices and methods for disrupting the stratum corneum for the purpose of delivering substances to the body. For example, breach of the stratum corneum may be achieved by puncturing as taught in U.S. Pat. No. 5,679,647 to Carson, et al. This patent teaches that narrow diameter tynes, such as those found on devices used for tuberculin skin tests and allergy tests, can be coated with polynucleotides and used for delivery of such materials into the skin. The method of using such devices involves puncturing the skin with the tynes resulting in intracutaneous injection of the coated substance. This is in contrast to the present invention, where it has been unexpectedly discovered that substances coated onto the surface of narrow diameter micro-protrusions are delivered more effectively by lateral abrasion across the skin surface rather than by puncturing. U.S. Pat. No. 5,003,987; U.S. Pat. No. 5,879,326; and U.S. Pat. No. 3,964,482 teach breaching the stratum corneum by abrasion, however, little is known about how to optimize topical application methods to achieve efficient and efficacious delivery by this route. Such optimization is of particular interest for topical nucleic acid delivery, especially topical delivery of nucleic acid-based vaccines and gene therapies. In this regard, the most commonly suggested method for topical administration is to abrade the skin prior to application of the vaccine. However, it has now been unexpectedly found that delivery of nucleic acids and peptides or polypeptides such as allergens is more efficient and more efficacious when the substance is delivered simultaneously with abrasion.

#FIG. 1 illustrates levels of gene expression obtained with the various nucleic acid delivery protocols tested in Example 1.

#FIG. 2 illustrates levels of gene expression obtained by varying the number of abrasions as described in Example 2.

#FIG. 3 illustrates levels of gene expression obtained by varying the formulation of the nucleic acid and the delivery protocol as described in Example 3.

#The term “abrasion” as used herein refers to disruption of the outer layers of the skin, for example by scraping or rubbing, resulting in an area of disrupted stratum corneum. This is in contrast to “puncturing” which produces discrete holes through the stratum corneum with areas of undisrupted stratum corneum between the holes. According to the methods of the invention, substances such as nucleic acid-based vaccines and peptides or polypeptides are applied to the skin simultaneously with abrasion rather than being applied to previously abraded skin. That is, the substance is abraded into the skin rather than being passively applied to skin which has been previously abraded. This method results in improved delivery and response as compared to post-abrasion application.

#The substance may be delivered into the skin in any pharmaceutically acceptable form, but a liquid or gel formulation is preferred. In one embodiment the substance is applied to the skin and an abrading device is then moved or rubbed reciprocally over the skin and the substance. It is preferred that the minimum amount of abrasion to produce the desired result be used. Determination of the appropriate amount of abrasion for a selected substance is within the ordinary skill in the art. In another embodiment the substance may be applied in dry form to the abrading surface of the delivery device prior to application. In this embodiment, a reconstituting liquid is applied to the skin at the delivery site and the substance-coated abrading device is applied to the skin at the site of the reconstituting liquid. It is then moved or rubbed reciprocally over the skin so that the substance becomes dissolved in the reconstituting liquid on the surface of the skin and is delivered simultaneously with abrasion. Alternatively, a reconstituting liquid may be contained in the abrading device and released to dissolve the substance as the device is applied to the skin for abrasion. It has been found that nucleic acid preparations may also be coated on the abrading device in the form of a gel, although the improvement in gene expression is not as significant as in certain other embodiments of the invention.

#Any device known in the art for disruption of the stratum corneum by abrasion can be used in the methods of the invention. These include, for example, microelectromechanical (MEMS) devices with arrays of short microneedles or microprotrusions, sandpaper-like devices, scrapers and the like. If the abrading device does not include a reservoir for containment and discharge of fluids from the device, the substance-containing liquid or the reconstituting liquid must be separately applied to the skin prior to abrading, for example from a separate dispenser or pump. However, reservoirs may be an integral part of the abrading device. Typically the reservoir is in fluid communication with the abrading surface of the device, for example via channels through the needles or protrusions, or via channels which exit the reservoir between such needles or protrusions, or via porous materials. In this embodiment, the substance or reconstituting liquid is contained in the reservoir of the abrading device and is dispensed to the skin surface prior to abrasion or simultaneously with abrasion. The abrading device may also include means for controlling the rate of delivery of the substance or reconstituting liquid, or for controlling the amount of substance or reconstituting liquid delivered.