Cell-mediated immune response and protective efficacy of porcine reproductive and respiratory syndrome virus modified-live vaccines against co-challenge with PRRSV-1 and PRRSV-2

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 (10 5.4 tciD 50 /ml) and PRRSV-2 (10 5.2 tciD 50 /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. Porcine reproductive and respiratory syndrome (PRRS) is a devastating disease in pigs characterized by reproductive and respiratory failures. PRRS virus (PRRSV), an enveloped, positive-sense single-stranded RNA virus belonging to the Arteriviridae family, order Nidovirales, is the causative agent 1. Two antigenically distinct genotypes of PRRSV, PRRSV-1 and PRRSV-2, have been recognized. The genomes of both genotypes are 15 kb in

Commercial PRRS Modified-Live Virus Vaccines

“…These findings are consistent in field studies, where the MLV2 vaccine is also effective against respiratory disease in PRRSV-1 and PRRSV-2 concurrent endemically infected farms [ 69 , 70 , 71 ]. This dual challenge study contradicted another study, where a significant difference between MLV1 and MLV2 against dual PRRSV-1 and PRRSV-2 challenge did not occur [ 72 ]. The discrepancy between two dual challenge studies may be due to the different challenge virus used per study.…”

Concomitant Swine Influenza A Virus Infection Alters PRRSV1 MLV Viremia in Piglets but Does Not Interfere with Vaccine Protection in Experimental Conditions

“…As reviewed by Van Reeth et Ma in 2013, an intranasal route or an endotracheal route using a lower swIAV dose lead to slower and lower viral load peaks in lungs, milder lung inflammation (lower levels of IFNa, IFNg and pro-inflammatory cytokines in BALF) and less influenza-specific symptoms [ 40 ]. The MLV1 vaccination route could additionally have impacted the results obtained in this study as it was demonstrated that intramuscular PRRSV vaccination induced a lower cell-mediated immune response than intradermal vaccination [ 5 , 41 ].…”

Impacts of Quarterly Sow Mass Vaccination with a Porcine Reproductive and Respiratory Syndrome Virus Type 1 (PRRSV-1) Modified Live Vaccine in Two Herds

“…In Denmark, 98.8 percent of the PRRSV-1 vaccines sold for breeding animals in 2020 were MLV vaccines (https://vetstat.fvst.dk/vetstat/, accessed on 5 April 2021), which is in accordance with the situation in other countries. The prescription of MLV vaccines towards reproductive failure in sow herds is supported by research in the field [7][8][9][10]. However, repeated exposure of breeding animals to PRRSV MLV is often "off-label" use and may lead to negative side effects [11,12].…”