Abstract
Cell-mediated immunity (CMI), IL-10, and the protective efficacy of modified-live porcine reproductive and respiratory syndrome virus (PRRSV) vaccines (MLV) against co-challenge with PRRSV-1 and PRRSV-2 (HP-PRRSV) were investigated. Seventy, PRRSV-free, 3-week old, pigs were allocated into 7 groups. Six groups were intramuscularly vaccinated with MLV, including Porcilis (PRRSV-1 MLV, MSD Animal Health, The Netherlands), Amervac (PRRSV-1 MLV, Laboratorios Hipra, Spain), Fostera (PRRSV-2 MLV, Zoetis, USA), Ingelvac PRRS MLV and Ingelvac PRRS ATP (PRRSV-2, Boehringer Ingelheim, USA), and Prime Pac PRRS (PRRSV-2 MLV, MSD Animal Health, The Netherlands). Unvaccinated pigs were left as control. Lymphocyte proliferative response, IL-10 and IFN-γ production were determined. At 35 days post-vaccination (DPV), all pigs were inoculated intranasally with 2 ml of each PRRSV-1 (105.4 TCID50/ml) and PRRSV-2 (105.2 TCID50/ml, HP-PRRSV). Following challenge, sera were quantitatively assayed for PRRSV RNA. Pigs were necropsied at 7 days post-challenge. Viremia, macro- and microscopic lung lesion together with PRRSV antigen presence were evaluated in lung tissues. The results demonstrated that, regardless of vaccine genotype, CMI induced by all MLVs was relatively slow. Increased production of IL-10 in all vaccinated groups was observed at 7 and 14 DPV. Pigs in Amervac, Ingelvac MLV and Ingelvac ATP groups had significantly higher levels of IL-10 compared to Porcilis, Fostera and Prime Pac groups at 7 and 14 DPV. Following challenge, regardless to vaccine genotype, vaccinated pigs had significantly lower lung lesion scores and PRRSV antigens than those in the control group. Both PRRSV-1 and PRRSV-2 RNA were significantly reduced. Prime Pac pigs had lowest PRRSV-1 and PRRSV-2 RNA in serum, and micro- and macroscopic lung lesion scores (p < 0.05) compared to other vaccinated groups. In conclusion, PRRSV MLVs, regardless of vaccine genotype, can reduce viremia and lung lesions following co-challenge with PRRSV-1 and PRRSV-2 (HP-PRRSV). The main difference between PRRSV MLV is the production of IL-10 following vaccination.
Highlights
Porcine reproductive and respiratory syndrome (PRRS) is a devastating disease in pigs characterized by reproductive and respiratory failures
Our results revealed that vaccination with porcine reproductive and respiratory syndrome virus (PRRSV) modified-live vaccines (MLV), regardless of vaccine genotype, provide partial cross-protection against PRRSV infection
At 7 days post-vaccination (DPV), the Ingelvac MLV group had the highest amount of CD4+IL-10+ cells as compared to the PRRSV-1 or PRRSV-2 MLV vaccination and NonVac groups (Fig. 2A)
Summary
Porcine reproductive and respiratory syndrome (PRRS) is a devastating disease in pigs characterized by reproductive and respiratory failures. Two antigenically distinct genotypes of PRRSV, PRRSV-1 and PRRSV-2, have been recognized. Several PRRSV modified-live vaccines (MLV) against PRRSV-1 and PRRSV-2 have been commercially available and licensed in several countries worldwide depending on circulating virus genotypes. The use of PRRSV MLV depends on PRRSV genotype circulating in that region. The criteria for vaccine selection should include the induction of the cell-mediated immunity (CMI) and the protection against PRRSV infection, especially against genotypes and isolates that are circulating in the affected region. Our results revealed that vaccination with PRRSV MLVs, regardless of vaccine genotype, provide partial cross-protection against PRRSV infection. This approach provided novel information regarding the vaccine selection for use in the presence of co-existence of both PRRSV genotypes
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