Intradermal administration of viral vaccines

Cutaneous delivery of prophylactic and therapeutic vaccines: historical perspective and future outlook

The skin has long been recognized as an attractive target for vaccine administration. A number of clinical studies have tested the epidermal and dermal routes of delivery using a variety of vaccines over the years. In many cases, cutaneous administration has been associated with immunological benefits, such as the induction of greater immune responses compared with those elicited by conventional routes of delivery. Furthermore, there is a growing body of evidence to suggest that such benefits may be particularly important for certain higher-risk populations, such as the elderly, the immunocompromised and cancer patients. Despite the potential advantages of vaccination via the skin, results have sometimes been conflicting and the full benefits of this approach have not been fully realized, partly due to the lack of delivery devices that accurately and reproducibly administer vaccines to the skin. The 5-year outlook, however, appears quite promising as new cutaneous delivery systems advance through clinical trials and become available for more widespread clinical and commercial use.

Preclinical evaluation of microneedle technology for intradermal delivery of influenza vaccines

Recent clinical studies have suggested that, for certain strains of influenza virus, intradermal (i.d.) delivery may enable protective immune responses using a lower dose of vaccine than required by intramuscular (i.m.) injection. Here, we describe the first preclinical use of microneedle technology for i.d. administration of three different types of influenza vaccines: (i) a whole inactivated influenza virus, (ii) a trivalent split-virion human vaccine, and (iii) a plasmid DNA encoding the influenza virus hemagglutinin. In a rat model, i.d. delivery of the whole inactivated virus provided up to 100-fold dose sparing compared to i.m. injection. In addition, i.d. delivery of the trivalent human vaccine enabled at least 10-fold dose sparing for the H1N1 strain and elicited levels of response across the dose range similar to those of i.m. injection for the H3N2 and B strains. Furthermore, at least fivefold dose sparing from i.d. delivery was evident in animals treated with multiple doses of DNA plasmid vaccine, although such effects were not apparent after the first immunization. Altogether, the results demonstrate that microneedle-based i.d. delivery elicits antibody responses that are at least as strong as via i.m. injection and that, in many cases, dose sparing can be achieved by this new immunization method.

Dermal testing of vaccines for children at high risk of allergies

Vaccinations for children with allergic diseases often need to be postponed or terminated because of the presumed risk of an immediate-type allergic reaction such as anaphylaxis. A new skin test protocol for predicting allergic reactions using the vaccine itself and the following stepwise vaccination method were developed and tested. Intradermal tests using 1:10 and 1:100 diluted measles vaccine indicated that the former was superior to the latter because a positive reaction against 1:10 diluted vaccine was found in 28.6% of 49 patients with severe allergic diseases including bronchial asthma, atopic dermatitis, food allergies and allergies to two or more allergens with high levels of IgE, as compared with the reaction against 1:100 diluted vaccine in 10.2% of the patients. Patients negative for 1:10 skin tests were safe from the following full-dose vaccine shots. Three patients showed very strong local reactions against measles vaccine, and avoided receiving the following full-dose shot. Positive reactions to skin tests of 1:10 diluted vaccine were found in 11 patients, who were given stepwise vaccinations. Three patients had adverse reactions, and two of them had been negative for 1:100 skin tests. In the case of influenza vaccine, skin tests were again more sensitive to 1:10 than to 1:100 diluted vaccine, because 3 out of 14 patients with positive reactions showed immediate-type adverse reactions against the following stepwise vaccinations, and 1 of them was negative for the 1:100 skin test. Moreover, the results of the skin prick test (undiluted vaccine) and the intradermal skin test (1:10 diluted vaccine) indicated that the latter was more useful in both cases of measles (54 patients) and influenza vaccine (69 patients). Overall, the skin test using 1:10 diluted vaccine was the more suitable for predicting an immediate-type reaction to measles and influenza vaccinations. Patients having negative 1:10 skin tests can be expected to show no adverse reactions to the remaining injections and even the positive subjects will complete the course of vaccine doses by the stepwise method.

Microneedle-based intradermal delivery of the anthrax recombinant protective antigen vaccine

The recombinant protective antigen (rPA) of Bacillus anthracis is a promising anthrax vaccine. We compared serum immunoglobulin G levels and toxin-neutralizing antibody titers in rabbits following delivery of various doses of vaccine by microneedle-based intradermal (i.d.) delivery or intramuscular (i.m.) injection using conventional needles. Intradermal delivery required less antigen to induce levels of antibody similar to those produced via i.m. injection during the first 2 weeks following primary and booster inoculation. This dose-sparing effect was less evident at the later stages of the immune response. Rabbits immunized i.d. with 10 mug of rPA displayed 100% protection from aerosol spore challenge, while i.m. injection of the same dose provided slightly lower protection (71%). Groups immunized with lower antigen doses were partially protected (13 to 29%) regardless of the mode of administration. Overall, our results suggest rPA formulated with aluminum adjuvant and administered to the skin by a microneedle-based device is as efficacious as i.m. vaccination.

Stress as an endogenous adjuvant: augmentation of the immunization phase of cell-mediated immunity

Stress is thought to be immunosuppressive but paradoxically exacerbates inflammatory and autoimmune diseases. We initially showed that acute stress enhances skin immunity. Such immunoenhancement could promote immunoprotection in case of wounding, infection or vaccination but could also exacerbate immunopathological diseases. Here we identify the molecular and cellular mediators of the immunoenhancing effects of acute stress. Compared with non-stressed mice, acutely stressed animals showed significantly greater pinna swelling and leukocyte infiltration, and up-regulated macrophage chemoattractant protein-1, macrophage inflammatory protein-3alpha, IL-1alpha, IL-1beta, IL-6, tumor necrosis factor-alpha and IFN-gamma, but not IL-4 gene expression at the site of primary antigen exposure. Stressed animals also showed enhanced maturation and trafficking of dendritic cells (DCs) from skin to lymph nodes (LNs), higher numbers of activated macrophages in skin and LNs, increased T cell activation in LNs, and enhanced recruitment of surveillance T cells to skin. These findings show that important interactive components of innate (DCs and macrophages) and adaptive (surveillance T cells) immunity are mediators of the stress-induced enhancement of a primary immune response. Such enhancement during primary immunization may induce a long-term increase in immunologic memory resulting in subsequent augmentation of the immune response during secondary antigen exposure. Thus, the evolutionarily adaptive fight-or-flight stress response may protectively prepare the immune system for impending danger (e.g. infection and wounding by a predator), but may also contribute to stress-induced exacerbation of inflammatory and autoimmune diseases.