Intramuscular vs. Intradermic Needle-Free Vaccination in Piglets: Relevance for Animal Welfare Based on an Aversion Learning Test and Vocalizations.

The aim of the present study was to compare intramuscular injection with a needle and intradermic needle-free vaccinations against porcine reproductive and respiratory syndrome (PRRS) in piglets at 28 days old by studying behavioral and physiological reactions. A total of 72 piglets divided into 2 sex-balanced batches were assessed. Within each batch, the piglets were divided into three treatments, which were Hipradermic (0.2 ml of UNISTRAIN® PRRS vaccine administered with an intradermic needle-free device), Intramuscular (IM, 2.0 ml of vaccine), and Control (not vaccinated). Before the vaccination, the piglets were trained to cross a 4-m-long raceway to perform an aversion learning test. The day of vaccination, the time taken to cross the raceway was registered for each piglet at different times: prior to the vaccination and 10 min, 2, 24, 48, and 72 h after the vaccination, to measure variations in these times as signs of aversion to the vaccination process. Vocalizations, as potential signs of pain, were recorded as well at the end of this raceway to analyze their frequency (Hz), duration, and level of pressure (dB) at the moment of vaccination. Salivary cortisol, as a sign of the HPA-axis activity, was assessed 10 min after the vaccination. In addition, activity budgets, local reaction to the vaccine, and serological titer were also considered in the study. Ten minutes after the vaccination, the IM piglets took longer (p < 0.001) to cross the raceway than did the Hipradermic and Control piglets. Vocalizations were significantly different between the three treatments: the Control piglets produced vocalizations with the lowest frequency (p < 0.001) and level of pressure (p < 0.001), and IM with the highest, with Hipradermic in a significant intermediate position (p < 0.001). Accordingly, the day of the vaccination, IM and Hipradermic animals were lying on the side of the vaccine administration a greater proportion of time than were the Control piglets (10, 11, and 6%, respectively; p = 0.027). Salivary cortisol was not significantly different between treatments. The serum titer of antibodies against the PRRS was higher (p < 0.001) in both vaccinated treatments in comparison to the Control piglets. It is concluded that the Hipradermic needle-free vaccination may result in a less aversive experience in piglets than did intramuscular vaccination.

Proof of Concept for Prevention of Natural Colonization by Oral Needle-Free Administration of a Microparticle Vaccine.

There has been substantial interest in the development of needle-free vaccine administration that has led to a variety of approaches for delivery through the skin for induction of a systemic immune response. The mucosal administration of vaccines has inherently been needle-free, but the simple application of vaccines on the mucosal surface by itself does not lead to mucosal immunity. Since many important bacterial infections develop after initial colonization of the upper respiratory tract of the host, prevention of colonization could not only prevent infection but also eliminate the reservoir of pathogens that reside exclusively in that ecologic niche. This study was designed to provide proof of concept for a needle-free immunization approach that would reduce or eliminate colonization and prevent infection. In order to accomplish this a microparticle vaccine preparation was delivered just below the oral mucosal epithelial cell layer where it would lead to a robust immune response. A vaccine antigen (mutant transferrin binding protein B) shown to be capable of preventing infection in pigs was incorporated into a polyphosphazene microparticle preparation and delivered by a needle-free device to the oral sub-epithelial space of pigs. This vaccination regimen not only provided complete protection from infection after intranasal challenge by Glaesserella parasuis but also eliminated natural colonization by this bacterium. Notably, the complete prevention of natural colonization was dependent upon delivery of the microparticle preparation below the epithelial layer in the oral mucosa as intradermal or intramuscular delivery was not as effective at preventing natural colonization. This study also demonstrated that a primary immunization in the presence of maternal antibody limited the resulting antibody response but a robust antibody response after the second immunization indicated that maternal antibody did not prevent induction of B-cell memory.

Current Progress in Particle-Based Systems for Transdermal Vaccine Delivery.

Transcutaneous immunization (TCI) via needle-free and non-invasive drug delivery systems is a promising approach for overcoming the current limitations of conventional parenteral vaccination methods. The targeted access to professional antigen-presenting cell (APC) populations within the skin, such as Langerhans cells (LCs), various dermal dendritic cells (dDCs), macrophages, and others makes the skin an ideal vaccination site to specifically shape immune responses as required. The stratum corneum (SC) of the skin is the main penetration barrier that needs to be overcome by the vaccine components in a coordinated way to achieve optimal access to dermal APC populations that induce priming of T-cell or B-cell responses for protective immunity. While there are numerous approaches to penetrating the SC, such as electroporation, sono- or iontophoresis, barrier and ablative methods, jet and powder injectors, and microneedle-mediated transport, we will focus this review on the recent progress made in particle-based systems for TCI. This particular approach delivers vaccine antigens together with adjuvants to perifollicular APCs by diffusion and deposition in hair follicles. Different delivery systems including nanoparticles and lipid-based systems, for example, solid nano-emulsions, and their impact on immune cells and generation of a memory effect are discussed. Moreover, challenges for TCI are addressed, including timely and targeted delivery of antigens and adjuvants to APCs within the skin as well as a deeper understanding of the ill-defined mechanisms leading to the induction of effective memory responses.

Advances Towards Painless Vaccination and Newer Modes of Vaccine Delivery.

Vaccines have been successful in reducing the mortality and morbidity, but most of them are delivered by intramuscular or intravenous route. They are associated with pain to the baby and bring lot of anxiety for the parents. There has been a marked increase in the number of injections required in first two years of life for completing the vaccination schedule. Hence, there is a need to have a painless vaccine delivery system. Numerous new routes of vaccination like, oral, nasal and transdermal routes are being tried. Oral polio and intranasal influenza have already been a success. Other newer approaches like edible vaccines, nasal sprays, dry powder preparations, jet injectors, microneedles and nanopatches are promising in delivering painless vaccines. Many of them are under clinical trials. These vaccine delivery systems will not only be painless but also cost effective, safe and easy to administer in mass population. They may be devoid of the need of cold chain. Painless delivery system will ensure better compliance to vaccination schedule.

Microneedles: quick and easy delivery methods of vaccines.

Vaccination is the most efficient method for infectious disease prevention. Parenteral injections such as intramuscular, intradermal, and subcutaneous injections have several advantages in vaccine delivery, but there are many drawbacks. Thus, the development of a new vaccine delivery system has long been required. Recently, microneedles have been attracting attention as new vaccination tools. Microneedle is a highly effective transdermal vaccine delivery method due to its mechanism of action, painlessness, and ease of use. Here, we summarized the characteristics of microneedles and the possibilities as a new vaccine delivery route.

Microneedles: quick and easy delivery methods of vaccines

Vaccination is the most efficient method for infectious disease prevention. Parenteral injections such as intramuscular, intradermal, and subcutaneous injections have several advantages in vaccine delivery, but there are many drawbacks. Thus, the development of a new vaccine delivery system has long been required. Recently, microneedles have been attracting attention as new vaccination tools. Microneedle is a highly effective transdermal vaccine delivery method due to its mechanism of action, painlessness, and ease of use. Here, we summarized the characteristics of microneedles and the possibilities as a new vaccine delivery route.

Influenza nucleoprotein DNA vaccination by a skin targeted, dry coated, densely packed microprojection array (Nanopatch) induces potent antibody and CD8(+) T cell responses.

DNA vaccines have many advantages such as thermostability and the ease and rapidity of manufacture; for example, in an influenza pandemic situation where rapid production of vaccine is essential. However, immunogenicity of DNA vaccines was shown to be poor in humans unless large doses of DNA are used. If a highly efficacious DNA vaccine delivery system could be identified, then DNA vaccines have the potential to displace protein vaccines. In this study, we show in a C57BL/6 mouse model, that the Nanopatch, a microprojection array of high density (>21,000 projections/cm(2)), could be used to deliver influenza nucleoprotein DNA vaccine to skin, to generate enhanced antigen specific antibody and CD8(+) T cell responses compared to the conventional intramuscular (IM) delivery by the needle and syringe. Antigen specific antibody was measured using ELISA assays of mice vaccinated with a DNA plasmid containing the nucleoprotein gene of influenza type A/WSN/33 (H1N1). Antigen specific CD8(+) T cell responses were measured ex-vivo in splenocytes of mice using IFN-γ ELISPOT assays. These results and our previous antibody and CD4(+) T cell results using the Nanopatch delivered HSV DNA vaccine indicate that the Nanopatch is an effective delivery system of general utility that could potentially be used in humans to increase the potency of the DNA vaccines.

Nanoengineering of vaccines using natural polysaccharides.

Currently, there are over 70 licensed vaccines, which prevent the pathogenesis of around 30 viruses and bacteria. Nevertheless, there are still important challenges in this area, which include the development of more active, non-invasive, and thermo-resistant vaccines. Important biotechnological advances have led to safer subunit antigens, such as proteins, peptides, and nucleic acids. However, their limited immunogenicity has demanded potent adjuvants that can strengthen the immune response. Particulate nanocarriers hold a high potential as adjuvants in vaccination. Due to their pathogen-like size and structure, they can enhance immune responses by mimicking the natural infection process. Additionally, they can be tailored for non-invasive mucosal administration (needle-free vaccination), and control the delivery of the associated antigens to a specific location and for prolonged times, opening room for single-dose vaccination. Moreover, they allow co-association of immunostimulatory molecules to improve the overall adjuvant capacity. The natural and ubiquitous character of polysaccharides, together with their intrinsic immunomodulating properties, their biocompatibility, and biodegradability, justify their interest in the engineering of nanovaccines. In this review, we aim to provide a state-of-the-art overview regarding the application of nanotechnology in vaccine delivery, with a focus on the most recent advances in the development and application of polysaccharide-based antigen nanocarriers.

A study of the effectiveness of a needle-free injection device compared with a needle and syringe used to vaccinate calves against bovine viral diarrhea and infectious bovine rhinotracheitis viruses.

The aim of this study was to compare the effectiveness of a needle-free injection device (NF) with a needle and syringe (NS) when used to vaccinate calves against bovine viral diarrhea virus (BVDV) and infectious bovine rhinotracheitis virus (IBRV). The study was conducted in two independent phases. Ninety-six crossbred beef calves were vaccinated in the spring and 98 beef calves in the autumn. The calves were vaccinated using a NF or NS at 2 months of age (day 0) and again on day 119, with a modified-live virus vaccine containing IBRV, BVDV (types 1 and 2), parainfluenza-3 virus, and bovine respiratory syncytial virus. In each herd 10 calves were left unvaccinated to determine whether exposure to either BVDV or IBRV occurred. Visible vaccine residue at the surface of the skin/hair was apparent immediately following vaccination with NF in 30% of the spring-born calves following both the primary and booster vaccination. In the autumn, visible vaccine residues occurred in 19% and 8% of NF-vaccinated calves following the primary and booster vaccination. Post-vaccination skin reactions recorded on days 21, 42, 119 and 140 occurred with greater frequency in NF-vaccinated calves than NS-vaccinated ones. Blood samples were collected on days 0, 21, 42, 119, and 140 and tested for antibodies to BVDV and IBRV. Vaccination technique had no significant effect on BVDV or IBRV antibody concentrations at any time point. NF was as effective as NS vaccination in eliciting BVDV and IBRV antibody responses.