Vaccination of pigs against Aujeszky's disease by the intradermal route using live attenuated and inactivated virus vaccines

Effect of vaccination route (intradermal vs. intramuscular) against porcine reproductive and respiratory syndrome using a modified live vaccine on systemic and mucosal immune response and virus transmission in pigs

BACKGROUND

Porcine reproductive and respiratory syndrome (PRRS) is a viral disease with worldwide distribution and an enormous economic impact. To control PRRS virus (PRRSV) infection, modified live vaccines (MLVs) are widely used in the field, mainly administered via an intramuscular (IM) route. Currently, some MLVs are authorized for intradermal (ID) administration, which has many practical and welfare advantages. The objectives of the study were to compare the immune responses (systemic in blood and mucosal in lungs) and vaccine efficacy in preventing challenge strain transmission after IM or needle-free ID immunization of piglets with an MLV against PRRSV-1 (MLV1).

METHODS

Groups of sixteen 5-week-old specific pathogen-free piglets were vaccinated with Porcilis PRRS® (MSD) either by an IM (V+ IM) or ID route (V+ ID) using an IDAL®3G device or kept unvaccinated (V-). Four weeks after vaccination, in each group, 8 out of the 16 piglets were challenged intranasally with a PRRSV-1 field strain, and one day later, the inoculated pigs were mingled by direct contact with the remaining 8 sentinel noninoculated pigs to evaluate PRRSV transmission. Thus, after the challenge, each group (V+ IM, V+ ID or V-) included 8 inoculated and 8 contact piglets. During the postvaccination and postchallenge phases, PRRSV replication (RT-PCR), PRRSV-specific antibodies (ELISA IgG and IgA, virus neutralization tests) and cell-mediated immunity (ELISPOT Interferon gamma) were monitored in blood and bronchoalveolar lavages (BALs).

RESULTS

Postvaccination, vaccine viremia was lower in V+ ID pigs than in V+ IM pigs, whereas the cell-mediated immune response was detected earlier in the V+ ID group at 2 weeks postvaccination. In the BAL fluid, a very low mucosal immune response (humoral and cellular) was detected. Postchallenge, the vaccine efficacy was similar in inoculated animals with partial control of PRRSV viremia in V+ ID and V+ IM animals. In vaccinated sentinel pigs, vaccination drastically reduced PRRSV transmission with similar estimated transmission rates and latency durations for the V+ IM and V+ ID groups.

CONCLUSIONS

Our results show that the tested MLV1 induced a faster cell-mediated immune response after ID immunization two weeks after vaccination but was equally efficacious after IM or ID immunization towards a challenge four weeks later. Considering the practical and welfare benefits of ID vaccination, these data further support the use of this route for PRRS MLVs.

Skin-Based Vaccination: A Systematic Mapping Review of the Types of Vaccines and Methods Used and Immunity and Protection Elicited in Pigs

The advantages of skin-based vaccination include induction of strong immunity, dose-sparing, and ease of administration. Several technologies for skin-based immunisation in humans are being developed to maximise these key advantages. This route is more conventionally used in veterinary medicine. Skin-based vaccination of pigs is of high relevance due to their anatomical, physiological, and immunological similarities to humans, as well as being a source of zoonotic diseases and their livestock value. We conducted a systematic mapping review, focusing on vaccine-induced immunity and safety after the skin immunisation of pigs. Veterinary vaccines, specifically anti-viral vaccines, predominated in the literature. The safe and potent skin administration to pigs of adjuvanted vaccines, particularly emulsions, are frequently documented. Multiple methods of skin immunisation exist; however, there is a lack of consistent terminology and accurate descriptions of the route and device. Antibody responses, compared to other immune correlates, are most frequently reported. There is a lack of research on the underlying mechanisms of action and breadth of responses. Nevertheless, encouraging results, both in safety and immunogenicity, were observed after skin vaccination that were often comparable to or superior the intramuscular route. Further research in this area will underlie the development of enhanced skin vaccine strategies for pigs, other animals and humans.

Efficacy of Needle-Less Intradermal Vaccination against Porcine Epidemic Diarrhea Virus

To prevent diarrhea in suckling piglets infected by porcine epidemic diarrhea virus (PEDV), porcine epidemic diarrhea (PED) vaccines are administered mainly through intramuscular (IM) or oral routes. We found that growing pigs vaccinated with an inactivated PEDV vaccine via the intradermal (ID) route had higher neutralizing antibody titers and cytokine (IFN-γ, IL-4, and IL-10) levels than non-vaccinated pigs. In addition, suckling piglets acquired lactogenic immunity from pregnant sows inoculated with an ID PED vaccine. We evaluated the efficacy of vaccination via this route, along with subsequent protection against virulent PEDV. At six days post-challenge, the survival rate of suckling piglets exposed to virulent PEDV was 70% for the ID group and 0% for the mock group (no vaccine). At necropsy, villi length in the duodenum and ileum of piglets with lactogenic immunity provided by ID-vaccinated sows proved to be significant (p < 0.05) when compared with those in piglets from mock group sows. Thus, vaccination using an inactivated PED vaccine via the ID route provides partial protection against infection by virulent PEDV.

Efficacy of intradermally administrated E2 subunit vaccines in reducing horizontal transmission of classical swine fever virus

To investigate if intradermal (ID) vaccination and intramuscular (IM) vaccination result in a comparable reduction of horizontal transmission of classical swine fever virus (CSFV), two registered E2 subunit marker vaccines were examined. Vaccine A was a water-in-oil emulsion containing the E2 glycoprotein originating from the Alfort/Tübingen strain and vaccine B was a water-oil-water emulsion containing the E2 glycoprotein originating from the Brescia strain. Eight groups, of ten pigs each, were vaccinated with either vaccine A or B, intramuscularly (IM) or intradermally (ID). Two different vaccination-challenge intervals were used for each vaccine. Furthermore, one group was vaccinated with a tenfold ID dose of vaccine A and one non-vaccinated group served as a control group. Five pigs from each group were challenged with the moderately virulent CSFV strain Paderborn, while the remaining five pigs served as contacts. Using vaccine A, full transmission to all contact pigs in both ID vaccinated groups occurred. No virus transmission was observed when IM vaccinated pigs were challenged 14 days post-vaccination (14dpv) whereas only one out of five contact pig became infected when they were challenged 10dpv. Using vaccine B no virus transmission was observed when pigs were ID or IM vaccinated and challenged 10dpv. When challenged 3dpv full transmission occurred in the ID vaccinated group, whereas four out of five contact pigs became infected in the IM vaccinated group. This result indicates that ID vaccination does not result in better protection against horizontal CSFV transmission compared to IM vaccination, for the vaccines studied.

Efficacy of intradermal vaccination

Intradermal (ID) inoculation has been investigated as a means of vaccinating laboratory animals, domestic farm animals, and humans. Various forms of viral, bacterial, parasitic, and fungal antigens have been administered ID, with varying results. This review emphasizes results from studies reporting clinically relevant outcomes such as clinical protection and body weight change following experimental challenge. Antibody titers, cytokines, cellular responses are included as supportive data. Based on the reports reviewed, ID vaccination is a promising alternative to more traditional routes of vaccination. ID vaccination has particular appeal to the beef cattle industry based on recently emphasized quality assurance issues. It is evident that the ultimate test of vaccine efficacy is the ability to protect against clinical disease under natural challenge conditions. We propose that the immune response of ID vaccinated cattle, using clinically relevant outcomes such as morbidity, mortality, average daily gain and feed efficiency, needs to be further investigated to define the value of this potentially effective and practical means of antigen delivery, particularly for domesticated farm animals.

A study of the ability of a TK-negative and gI/gE-negative pseudorabies virus (PRV) mutant inoculated by different routes to protect pigs against PRV infection

The capacity of a TK-negative (TK-) and gI/gE-negative (gI/gE-) pseudorabies virus (PRV) mutant to protect pigs against Aujeszky's disease carried out by experimental infection with a virulent PRV strain, was tested. There were three groups, each of four susceptible pigs which were inoculated twice by two different schedules. Group 1 received the modified virus by the intradermal (first inoculation)-intramuscular (second inoculation) routes; group 2 was treated by the intranasal (first inoculation)-intramuscular (second inoculation) routes. The third group was left untreated as the control. All of the pigs were challenged intranasally with a virulent PRV strain and they were subsequently injected with dexamethasone. Two pigs in each group were necropsied on days 5 and 15 after dexamethasone inoculation. The challenge exposure resulted in mild clinical signs, increase in growth and a shorter period of virus shedding in vaccinated pigs, whereas the control group showed severe signs of Aujeszky's disease. No difference in the titre of the virulent virus which was excreted by pigs of all three groups, was observed and all animals seroconverted. Both the mutant strain and the wild-type virus established a latent infection although only the latter was reactivated and shed. Slight lesions were observed in target tissues of the vaccinated animals and no significant differences were detected between the two inoculation schedules.

Evaluation of parenteral vaccination methods with glycoproteins against Aujeszky's disease in pigs

A comparative evaluation of vaccination methods with glycoproteins for the induction of immune responses and protection of the pig against Aujeszky's disease virus (ADV) was performed. Different vaccination routes (intradermal (i.d.) versus intramuscular (i.m.)), inoculation sites (the neck versus the back) and number of inoculation points (2 versus 6) per site were compared. Body weight (BW) changes and viral excretion after challenge were compared with virus-neutralizing titers, antigen-specific IgG and IgA responses in serum and virus-specific lymphoproliferative responses in peripheral blood during the immunisation period. According to BW changes better protection was obtained with six-point than two-point i.d. injections. i.d. vaccination in the back at six points gave similar results as i.m. vaccination in the neck but appeared inferior in the reduction of virus excretion. Regarding the immunological parameters, the virus-specific IgA response in serum gave the best indication for protection. It can be concluded that according to BW changes, six-point i.d. immunisation in the back and i.m. immunisation in the neck provided the best protection and that six-point i.d. injections resulted in a better vaccination than two-point i.d. injections.

Vaccination of maternally immune pigs with a live Aujeszky's disease vaccine by coarse spray and other routes

33 ten weeks old passively immune weaners were inoculated with live, attenuated Aujeszky's disease (AD) vaccine, according to four different vaccination protocols: (groups A/A2) 3 x coarse spray vaccination at 10, 11 and 13 weeks of age, (groups B/B2) 1 x coarse spray at 10 weeks of age followed by 1 x intramuscularly at 13 weeks, (C) 1 x intranasal instillation at 10 weeks of age, and (groups D/D2) 2 x intramuscularly at 10 and 13 weeks of age. A further 10 weaners were included as unvaccinated controls (E/E2). Spray vaccination was technically simple to perform but on average, 20% of subjects were reluctant to expose themselves to the spray. Clinical reactions were absent apart from mild fever in one pig from group B. Weight gains between 10 and 17 weeks of age were slightly lower in group A and group B weaners, compared to control unvaccinated pigs and pigs vaccinated by other routes. Virus neutralising (VN) antibody response was extremely uneven between individuals in groups A and B. Group D pigs vaccinated 2 x intramuscularly showed a 3 week lag in developing high levels of antibody but the intramuscular route, as well vaccination by intransal instillation, proved to be the most dependable technique for inducing uniformly high levels of VN antibody. Challenge with virulent ADV at 17 weeks of age resulted in death from Aujeszky's disease of all five control pigs. One pig in group A which had no VN antibody, also died. All other pigs were protected against death.(ABSTRACT TRUNCATED AT 250 WORDS)

Protection of mice and swine from pseudorabies virus conferred by vaccinia virus-based recombinants

Glycoproteins gp50, gII, and gIII of pseudorabies virus (PRV) were expressed either individually or in combination by vaccinia virus recombinants. In vitro analysis by immunoprecipitation and immunofluorescence demonstrated the expression of a gII protein of approximately 120 kDa that was proteolytically processed to the gIIb (67- to 74-kDa) and gIIc (58-kDa) mature protein species similar to those observed in PRV-infected cells. Additionally, the proper expression of the 90-kDa gIII and 50-kDa gp50 was observed. All three of these PRV-derived glycoproteins were detectable on the surface of vaccinia virus-PRV recombinant-infected cells. In vivo, mice were protected against a virulent PRV challenge after immunization with the PRV glycoprotein-expressing vaccinia virus recombinants. The coexpression of gII and gIII by a single vaccinia virus recombinant resulted in a significantly reduced vaccination dose required to protect mice against PRV challenge. Inoculation of piglets with the various vaccinia virus-PRV glycoprotein recombinants also resulted in protection against virulent PRV challenge as measured by weight gain. The simultaneous expression of gII and gp50 in swine resulted in a significantly enhanced level of protection as evaluated by weight evolution following challenge with live PRV.