Safety and immune responses after intradermal application of Porcilis PRRS in either the neck or the perianal region

Intradermal Inoculation of Inactivated Foot-and-Mouth Disease Vaccine Induced Effective Immune Responses Comparable to Conventional Intramuscular Injection in Pigs

All pigs in the Republic of Korea are given the foot-and-mouth disease virus (FMDV) vaccine intramuscularly (IM) as part of the country's vaccination policy. However, the IM administration of the FMDV vaccine to pig results in residual vaccine components in the muscle and undesirable changes in muscle and soft tissues, causing economic losses in swine production. In this study, we evaluated whether intradermal (ID) vaccination could be proposed as an alternative to IM administration. ID vaccination (0.2 mL on each side of the neck muscle) and IM vaccination (2 mL on each side of the neck muscle) were performed twice, separated by 14 days, using a commercial FMD vaccine in specific-pathogen-free pigs. We observed growth performance, gross and microscopic lesions at the inoculation site, FMDV-specific antibodies, and neutralizing antibodies for 35 days after vaccination. Side effects on the skin grossly appeared following ID administration, but most were reduced within two weeks. All ID-vaccinated pigs showed inflammatory lesions limited to the dermis, but IM-vaccinated pigs had abnormal undesirable changes and pus in the muscle. ID-vaccinated pigs performed comparably to IM-vaccinated pigs in terms of growth, FMD virus-specific antibodies, protection capability against FMDV, and T-cell induction. This study demonstrated that the ID inoculation of the inactivated FMD vaccine induced immune responses comparable to an IM injection at 1/10 of the inoculation dose and that the inoculation lesion was limited to the dermis, effectively protecting against the formation of abnormal undesirable changes in muscle and soft tissues.

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.

Research Progress on the Development of Porcine Reproductive and Respiratory Syndrome Vaccines

Porcine reproductive and respiratory syndrome (PRRS) is a highly contagious disease in the pig industry, but its pathogenesis is not yet fully understood. The disease is caused by the PRRS virus (PRRSV), which primarily infects porcine alveolar macrophages and disrupts the immune system. Unfortunately, there is no specific drug to cure PRRS, so vaccination is crucial for controlling the disease. There are various types of single and combined vaccines available, including live, inactivated, subunit, DNA, and vector vaccines. Among them, live vaccines provide better protection, but cross-protection is weak. Inactivated vaccines are safe but have poor immune efficacy. Subunit vaccines can be used in the third trimester of pregnancy, and DNA vaccines can enhance the protective effect of live vaccines. However, vector vaccines only confer partial protection and have not been widely used in practice. A PRRS vaccine that meets new-generation international standards is still needed. This manuscript provides a comprehensive review of the advantages, disadvantages, and applicability of live-attenuated, inactivated, subunit, live vector, DNA, gene-deletion, synthetic peptide, virus-like particle, and other types of vaccines for the prevention and control of PRRS. The aim is to provide a theoretical basis for vaccine research and development.

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.

Evaluation of Intradermal PRRSV MLV Vaccination of Suckling Piglets on Health and Performance Parameters under Field Conditions

Porcine reproductive and respiratory syndrome virus (PRRSV) causes respiratory disease in weaning and growing pigs. A vaccination against PRRSV is one of the most important control measures. This trial aimed to evaluate the effect of the intradermal (ID) administration of a PRRSV-1 modified live virus (MLV) vaccine in comparison to the intramuscular (IM) administration on the piglets’ health and performance. A total of 187 suckling piglets of a PRRSV-positive commercial farrow-to-finish farm were assigned to four groups: group A—PRRSV ID, group B—PRRSV IM, group C—control ID, and group D—control IM. At 2 weeks of age, all the study piglets were either vaccinated with a PRRSV-1 MLV vaccine or injected with the vaccine adjuvant (controls). The collected blood serum samples were tested by ELISA and qRT-PCR. The side effects, body weight (BW), average daily gain (ADG), mortality rate, and lung and pleurisy lesions scores (LLS, PLS) were also recorded. The ELISA results indicated that the vaccination induced an important seroconversion at 4 and 7 weeks. Significant differences in the qRT-PCR results were noticed only at 10 weeks in group A vs. group C (p < 0.01) and group B vs. group C (p < 0.05). High viral loads, as evidenced by the qRT-PCR Ct values, were noticed in animals of both non-vaccinated groups at 7, 10, and 13 weeks. An ID vaccination has a positive impact on the BW at the piglets’ slaughter, while both an ID and IM vaccination had a positive impact on the ADG. The mortality rate was lower in vaccinated groups at the finishing stage. The LLS and PLS were significantly lower in the vaccinated groups. In conclusion, our study demonstrated that the ID vaccination of suckling piglets with a PRRSV-1 MLV vaccine has a positive effect on the piglets’ health and performance, including an improved BW and a lower LLS and PLS index at their slaughter, as well as a decreased mortality rate at the growing/finishing stage.

In the presence of non-neutralising maternally derived antibodies, intradermal and intramuscular vaccination with a modified live vaccine against porcine reproductive and respiratory syndrome virus 1 (PRRSV-1) induce similar levels of neutralising antibodies or interferon-gamma secreting cells

The purpose of this study was to compare the immune response generated by the intramuscular and the intradermal vaccination route against the porcine reproductive and respiratory syndrome virus (PRRSV). Piglets from a seronegative and a seropositive farm were selected (n = 28 piglets per farm), and each group was divided into two groups and vaccinated after weaning with modified live vaccine Unistrain® PRRS (Laboratorios Hipra Amer, Spain) by the intramuscular (IM) or the intradermic (ID) route. For the following 6 weeks, animals were weekly bled to assess the humoral response by PRRSV-specific antibody ELISA and viral neutralisation test. At 0-, 3-, 4- and 6 weeks post-vaccination, peripheral mononuclear blood cells (PBMC) from eight animals per group were recovered to analyse cellular response by IFN-γ ELISPOT and lymphoproliferation. Serum IL-12 was also quantified by ELISA. Seroconversion was first detected 14 days post-vaccination (dpv) for both IM and ID routes, and peaked at 35 dpv (both IM groups and ID seropositive) or 42 dpv (ID seronegative). At 3 weeks after vaccination, 6/27 (22.22%) animals from negative origin had not seroconverted, and neutralising titres were significantly lower at 35 dpv compared to the seropositive origin (mean log2 titres of 1.36 and 4.25 respectively) Also, it was 10 times more probable for them to have high levels of IL-12 a week after vaccination than for animals of seropositive origin. Cellular immune response analysed by lymphoproliferation and IFN-γ ELISPOT was already present at 21 dpv and until 42 dpv, with no significant differences between groups except for a higher lymphoproliferation at 35 dpv in the IM seropositive group (Kruskal-Wallis, p < 0.05). These results indicate that the intradermal route induces an immune response equivalent to the classical intramuscular route even in presence of non-neutralising maternal immunity, which in this study has proven to facilitate seroconversion after vaccination with an heterologous strain.

Angiotensin II Blood Serum Levels in Piglets, after Intra-Dermal or Intra-Muscular Vaccination against PRRSV

Simple Summary

Porcine reproductive and respiratory syndrome virus (PRRSV) infection causes massive financial losses in pig production worldwide. Vaccination is still the most cost-effective tool to handle PRRSV infection. PRRSV induces apoptosis in different organs. Angiotensin II (Ang II) participates in the inflammatory response, cell proliferation, migration, and apoptosis. The objective of the current study was to assess the concentration of Ang II in the serum of piglets following immunization against PRRSV through intradermal (ID) or intramuscular (IM) vaccination with a commercial PRRS modified live virus (MLV) vaccine. The results indicated differences in viremia of tested piglets at 7 weeks of age, while piglets at 10 weeks of age were all found qRT-PCR positive for PRRSV. Moreover, significant differences were noticed in Ang II in 7-week-old piglets. In conclusion, our study provides evidence that ID vaccination induces less tissue damage, based on the lower measurements of Ang II in the serum of ID vaccinated piglets.

Abstract

The Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) induces apoptosis in different organs. Angiotensin II (Ang II) is the main effector of the renin-angiotensin system and participates in apoptosis. Thus, this study aimed to investigate changes in piglet serum Ang II levels following intradermal (ID) and intramuscular (IM) vaccination with a commercial PRRS modified live virus (MLV) vaccine. The trial was conducted in a commercial pig farm, including 104 piglets which were randomly allocated to four groups: Group A—Porcilis PRRS ID, Group B—Porcilis PRRS IM, Group C—Diluvac ID and Group D—Diluvac IM. The study piglets were either vaccinated or injected at 2 weeks of age and they were tested by qRT-PCR for PRRSV and by ELISA for Ang II. The results indicated differences in viremia of tested piglets at 7 weeks of age, while piglets at 10 weeks of age were all found qRT-PCR positive for PRRSV. In addition, significant differences were noticed in Ang II in 7-week-old piglets. In conclusion, the present study provides evidence that ID vaccination induces less tissue damage, based on the lower measurements of Ang II in the serum of ID vaccinated piglets.

Investigation of Fas (APO-1)-Related Apoptosis in Piglets Intradermally or Intramuscularly Vaccinated with a Commercial PRRSV MLV

Porcine reproductive and respiratory syndrome virus (PRRSV) induces apoptosis through the activation of death receptors, including cell-surface Fas receptor. The aim of this study was to investigate the impact of intradermal (ID) and intramuscular (IM) vaccination with a commercial PRRSV-modified live vaccine in piglets on Fas-related apoptosis. The study included 104 suckling piglets from a commercial farrow-to-finish pig farm, suffering from positive unstable PRRSV status. Animals were assigned in four groups: group A-Porcilis PRRS ID-vaccinated pigs, group B-Porcilis PRRS IM-vaccinated pigs, group C-Diluvac ID adjuvant-administered pigs, and group D-Diluvac IM adjuvant-administered pigs. Vaccines were administered at 2 weeks of age. Blood samples were collected from the same pigs at 4, 7, and 10 weeks of age. Sera were examined by quantitative real-time reverse transcription-PCR (qRT-PCR) for PRRSV and by ELISA for soluble Fas (sFas). At 4 weeks of age, all groups were negative qRT-PCR for PRRSV; at 7 weeks only group A was negative; and at 10 weeks all groups were positive. sFas was significantly increased in groups C (4 vs. 7, 4 vs. 10, and 7 vs. 10 weeks) and D (7 vs. 10 weeks). Significant differences among groups were noticed only at 10 weeks (A vs. C, A vs. D, B vs. C, B vs. D). A significant positive and moderate correlation between PRRSV viral load and Fas level was observed. In unvaccinated piglets, increased serum sFas levels reveal apoptotic suppression compared with vaccinated piglets. In the latter, vaccine-derived antibodies limit the infection and may attribute to the reduced Fas expression, suggesting a weak induction of lymphocyte-mediated cytotoxicity.

Efficacy of Simultaneous Intradermal Vaccination of Swine against Porcine Circovirus 2, Porcine Reproductive and Respiratory Syndrome Virus, Mycoplasma hyopneumoniae and Lawsonia intracellularis

The combined application of vaccines in swine offers many benefits, including reduced time and labour costs, and improved animal welfare, due to fewer injections and manipulations. This study investigated if simultaneous intradermal vaccinations against porcine circovirus 2, porcine reproductive and respiratory syndrome virus, Mycoplasma hyopneumoniae, and Lawsonia intracellularis, using a specialised needle-free applicator would confer comparable protection against experimental infection compared to the single vaccines. In all cases, the administration of the vaccines together was as efficacious as the administration of the vaccines alone, significantly reducing clinical signs associated with each of the four pathogens.

Swine as biomedical animal model for T-cell research-Success and potential for transmittable and non-transmittable human diseases

Swine is biologically one of the most relevant large animal models for biomedical research. With its use as food animal that can be exploited as a free cell and tissue source for research and its high susceptibility to human diseases, swine additionally represent an excellent option for both the 3R principle and One Health research. One of the previously most limiting factors of the pig model was its arguably limited immunological toolbox. Yet, in the last decade, this toolbox has vastly improved including the ability to study porcine T-cells. This review summarizes the swine model for biomedical research with focus on T cells. It first contrasts the swine model to the more commonly used mouse and non-human primate model before describing the current capabilities to characterize and extend our knowledge on porcine T cells. Thereafter, it not only reflects on previous biomedical T-cell research but also extends into areas in which more in-depth T-cell analyses could strongly benefit biomedical research. While the former should inform on the successes of biomedical T-cell research in swine, the latter shall inspire swine T-cell researchers to find collaborations with researchers working in other areas - such as nutrition, allergy, cancer, transplantation, infectious diseases, or vaccine development.

Welfare Benefits of Intradermal Vaccination of Piglets

Vaccination is reported as a stressful and painful event for animals. This study investigated whether needle-free intradermal vaccination improves the welfare of weaned pigs through the reduction of stress and pain biomarkers and improvement of behavioural parameters compared to traditional intramuscular injection with a needle. A total of 339 weaned piglets were allocated to 3 treatment groups: Intradermal Application of Liquids (IDAL) pigs, vaccinated against Porcine Circovirus type 2 (PCV2) by means of intradermal vaccination using a needle-free device Porcilis^® PCV ID; Intramuscular (IM) pigs vaccinated against PCV2 with Porcilis^® PCV intramuscularly with a needle; CONTROL pigs were managed identically but did not receive any vaccine injection. At the time of the injection, the reaction of IDAL piglets was similar to control piglets, whereas a greater percentage of piglets vaccinated intramuscularly displayed high-pitch vocalizations (7% CONTROL, 7% IDAL, 32% IM) and retreat attempts (3% CONTROL, 7% IDAL, 39% IM). The day after vaccination, IDAL piglets did not differ from the control piglets for any of the behavioural variables studied through scan samplings. IM piglets showed a lower frequency of social negative interactions (p = 0.001) and rope manipulation (p = 0.04) compared to the CONTROL group. Resting postures did not differ between treatments. At 28 h post-vaccination, IDAL piglets presented lower blood C-reactive protein levels (CONTROL = 20 μg/mL; IDAL = 39 μg/mL; IM = 83 μg/mL, p < 0.0001) and blood Haptoglobin (CONTROL = 1.8 mg/mL; IDAL = 1.9 mg/mL vs. IM = 3.1 mg/mL, p < 0.0001) compared to IM piglets. Salivary chromogranin A and alpha-amylase did not differ between treatment groups when measured 25 min post-vaccination. The method of vaccination did not affect the growth of the piglets or their rectal temperature. These results support that needle-free intradermal vaccination reduces vaccination-related pain in growing pigs.

Dynamics and Differences in Systemic and Local Immune Responses After Vaccination With Inactivated and Live Commercial Vaccines and Subsequent Subclinical Infection With PRRS Virus

The goals of our study were to compare the immune response to different killed and modified live vaccines against PRRS virus and to monitor the antibody production and the cell mediated immunity both at the systemic and local level. In the experiment, we immunized four groups of piglets with two commercial inactivated (A1-Progressis, A2-Suivac) and two modified live vaccines (B3-Amervac, B4-Porcilis). Twenty-one days after the final vaccination, all piglets, including the control non-immunized group (C5), were i.n., infected with the Lelystad strain of PRRS virus. The serum antibody response (IgM and IgG) was the strongest in group A1 followed by two MLV (B3 and B4) groups. Locally, we demonstrated the highest level of IgG antibodies in bronchoalveolar lavages (BALF), and saliva in group A1, whereas low IgA antibody responses in BALF and feces were detected in all groups. We have found virus neutralization antibody at DPV 21 (days post vaccination) and higher levels in all groups including the control at DPI 21 (days post infection). Positive antigen specific cell-mediated response in lymphocyte transformation test (LTT) was observed in groups B3 and B4 at DPV 7 and in group B4 at DPV 21 and in all intervals after infection. The IFN-γ producing lymphocytes after antigen stimulation were found in CD4-CD8+ and CD4+CD8+ subsets of all immunized groups 7 days after infection. After infection, there were obvious differences in virus excretion. The virus was detected in all groups of piglets in serum, saliva, and occasionally in feces at DPI 3. Significantly lower virus load was found in groups A1 and B3 at DPI 21. Negative samples appeared at DPI 21 in B3 group in saliva. It can be concluded that antibodies after immunization and infection, and the virus after infection can be detected in all the compartments monitored. Immunization with inactivated vaccine A1-Progressis induces high levels of antibodies produced both systemically and locally. Immunization with MLV-vaccines (Amervac and Porcilis) produces sufficient antibody levels and also cell-mediated immunity. After infection virus secretion gradually decreases in group B3, indicating tendency to induce sterile immunity.