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

Abstract

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.

PRRSV-Vaccinated, Seronegative Sows and Maternally Derived Antibodies (II): Impact on PRRSV-1 Vaccine Effectiveness and Challenge Outcomes in Piglets

“…Additionally, Balasch et al described the capability of an MLV to overcome maternal immunity when this MLV is administered to 1-day-old piglets originating from sows that have been vaccinated once [ 46 ]. Finally, in a recent study by Aguire et al, the use of a heterologous PRRSV vaccine was able to overcome the MDA interference [ 47 ]. Although the use of a heterologous PRRSV vaccine in piglets is beneficial in overcoming the MDA interference, it is not recommended to use different MLV strains in the same herd, given the risk for recombination events [ 19 , 20 , 21 ].…”

Prevalence and genetic evolution of porcine reproductive and respiratory syndrome virus in commercial fattening pig farms in China

“…In China, the outbreak of PRRSV has had a significant impact on the economic performance of pig farms, and most of the losses are caused by a decrease in the number of weaned and fattened piglets and an increase in feed costs [ 53 ]. Control of the infection is usually performed by a combination of virus monitoring, biosecurity restrictions, herd management measures and vaccination [ 54 ]. Currently, commercial vaccines provide partial protection only against L1.8 (L1C) PRRSV [ 55 – 58 ]; therefore, there is an urgent need to develop a commercial vaccine for this disease.…”

Current Status of Vaccines for Porcine Reproductive and Respiratory Syndrome: Interferon Response, Immunological Overview, and Future Prospects

“…This technology has emerged as the pig industry seeks more effective and safer vaccination methods to enhance animal welfare. Extensive studies have demonstrated that the intradermal (ID) delivery system can provide protection comparable to or better than that provided by the intramuscular (IM) route [ 179 , 199 , 200 , 201 ]. This method is effective for PRRS vaccination, as the skin contains cells from both the innate and adaptive immune systems.…”

“…Following a virus challenge, the IM vaccination group exhibited a higher PRRSV-specific antibody response according to ELISA testing, whereas the ID vaccination group showed the highest expression levels of PRRSV-specific IFN-γ-SC 21 days post vaccination, indicating a stronger cell-mediated immune response [ 179 ]. Additional studies have also shown that ID vaccination of suckling piglets positively affects their health and performance, inducing an immune response equivalent to that achieved with the traditional intramuscular route [ 199 , 200 , 201 ].…”