The interference effect of maternally-derived antibodies on the serological performance of pigs immunized with a foot-and-mouth disease oil emulsion vaccine

Heterologous Prime-Boost Vaccination with Commercial FMD Vaccines Elicits a Broader Immune Response than Homologous Prime-Boost Vaccination in Pigs

Three commercial vaccines are administered in domestic livestock farms for routine vaccination to aid for foot-and-mouth disease (FMD) control in Korea. Each vaccine contains distinct combinations of inactivated serotype O and A FMD virus (FMDV) antigens: O/Manisa + O/3039 + A/Iraq formulated in a double oil emulsion (DOE), O/Primorsky + A/Zabaikalsky formulated in a DOE, and O/Campos + A/Cruzeiro + A/2001 formulated in a single oil emulsion. Despite the recommendation for a prime-boost vaccination with the same vaccine in fattening pigs, occasional cross-inoculation is inevitable for many reasons, such as lack of compliance with vaccination guidelines, erroneous application, or change in vaccine types by suppliers. Therefore, there have been concerns that a poor immune response could be induced by cross-inoculation due to a failure to boost the immune response. In the present study, it was demonstrated by virus neutralization and ELISA tests that cross-inoculation of pigs with three commercial FMD vaccines does not hamper the immune response against the primary vaccine strains and enhances broader cross-reactivity against heterologous vaccine antigens whether they were applied or not. Therefore, it could be concluded that the cross-inoculation of FMD vaccines can be used as a regimen to strategically overcome the limitation of the antigenic spectrum induced by the original regimen.

The C3d-fused foot-and-mouth disease vaccine platform overcomes maternally-derived antibody interference by inducing a potent adaptive immunity

Vaccination prevents and controls foot-and-mouth disease (FMD). However, the current FMD vaccine remains disadvantageous since it cannot overcome maternally-derived antibody (MDA) interference in weeks-old animals, which suppress active immunity via vaccination. To address this, we developed the immune-enhancing O PA2-C3d and A22-C3d FMD vaccine strains that can stimulate receptors on the surface of B cells by inserting C3d (a B cell epitope) into the VP1 region of O PA2 (FMDV type O) and A22 (FMDV type A). We purified inactivated viral antigens from these vaccine strains and evaluated their immunogenicity and host defense against FMDV infection in mice. We also verified its efficacy in inducing an adaptive immune response and overcome MDA interference in MDA-positive (MDA(+), FMD-seropositive) and -negative (MDA(−), FMD-seronegative) pigs. These results suggest a key strategy for establishing novel FMD vaccine platform to overcome MDA interference and induce a robust adaptive immune response.

Age-Dependent Dynamics of Maternally Derived Antibodies (MDAs) and Understanding MDA-Mediated Immune Tolerance in Foot-and-Mouth Disease-Vaccinated Pigs

Vaccine-induced active immunity in young animals may be compromised via interference caused by maternally derived antibodies (MDAs). Since the level, titer, and half-life of MDAs vary per individual, it is difficult to determine the appropriate timing of foot-and-mouth disease (FMD) vaccination in the field. In order to better understand the age-dependent characteristics of MDA in sows and piglets as well as the phenomenon of reduced vaccine-mediated active immunity due to MDAs, this study sought to determine antibody titers through structural protein (SP) O, A ELISA analyses, and virus-neutralizing (VN) antibody titers as well as their half-lives in the sera of sows and piglets derived from FMD-vaccinated mother. Furthermore, immunoglobulin (Ig) subtypes, such as IgG, IgM, and IgA, in serum were also evaluated. To understand the correlation between the inhibition of vaccine-mediated active immunity by MDA-mediated passive immunity and regulatory T (Treg) cells, Treg-related cytokine levels were explored. Our findings will help to predict the optimal timing of vaccination for overcoming MDAs and inducing a robust vaccine-mediated immune response in young individuals vaccinated against FMD. They also add to our understanding of MDA characteristics and interference, providing insight for the development of innovative strategies and novel FMD vaccine for overcoming such interference.

Impact of maternally derived immunity on immune responses elicited by piglet early vaccination against the most common pathogens involved in porcine respiratory disease complex

Background

Newborn piglets can trigger an elementary immune response, but the acquirement of specific antibodies and/or cellular immunity against pathogens before they get infected post-natally is paramount to preserve their health. This is especially important for the pathogens involved in porcine respiratory disease complex (PRDC) as they are widespread, fairly resistant at environment, and genetically variable; moreover, some of them can cause intrauterine/early life infections.

Main body

Piglet protection can be achieved by either passive transfer of maternal derived immunity (MDI) and/or actively through vaccination. However, vaccinating piglets in the presence of remaining MDI might interfere with vaccine efficacy. Hence, the purpose of this work is to critically review the putative interference that MDI may exert on vaccine efficacy against PRDC pathogens. This knowledge is crucial to design a proper vaccination schedule.

Conclusion

MDI transferred from sows to offspring could potentially interfere with the development of an active humoral immune response. However, no conclusive interference has been shown regarding performance parameters based on the existing published literature.

Evaluation of swine protection with foot-and-mouth disease O1/Campos and O/Primorsky/2014 vaccines against the O Mya-98 lineage virus from East Asia

Two type O commercial vaccines, the O₁/Campos and O/Primorsky/2014 vaccines, were studied to evaluate the in vivo efficacy in pigs against heterologous virus challenge with the O/SKR/Jincheon/2014 virus (O/SEA/Mya-98 lineage) isolated in Korea in 2014. The in vivo challenge results indicated that both vaccines induced a high heterologous virus neutralization test (VNT) titer by a single injection and successfully protected specific pathogen-free (SPF) pigs from challenge infection. To determine the optimal vaccination age, a field trial with each vaccine was conducted with three one-shot-vaccinated groups that were injected at 8, 12, or 14 weeks of age and one two-shot-vaccinated group that was injected at 8 and 12 weeks of age in the pig farms. In these field trials, the improved serological performance at 20 and 24 weeks of age expected with vaccination at 12 or 14 weeks of age was not observed, although improved serological results were expected as the result of decreasing interference of maternally derived antibodies (MDAs), as MDAs waned with age. In addition, delayed vaccination resulted in MDA depletion at 14 weeks of age. Therefore, the optimal age for primary vaccination with two different formulated vaccines was 8 weeks old in pigs, considering that MDAs could provide a protective immunity against foot-and-mouth disease (FMD) infection. Prolonged significantly higher VNT titers of immunized pigs were demonstrated in the two-shot-vaccinated groups. In total, the effectiveness of the two vaccines was demonstrated through efficacy tests and field trials in pigs.