Initial vaccination and revaccination with Type I PRRS 94881 MLV reduces viral load and infection with porcine reproductive and respiratory syndrome virus

Abstract

BackgroundPorcine reproductive and respiratory syndrome (PRRS) causes respiratory distress in pigs, reproductive failure in breeding-age gilts and sows, and can have devastating economic consequences in domestic herds. Several PRRS vaccines are available commercially. This study compared the effectiveness of single-vaccination and revaccination schedules using the PRRS 94881 Type I modified live virus (MLV) vaccine ReproCyc® PRRS EU with no vaccination (challenge control) in protecting against a PRRS virus (PRRSV) challenge in non-pregnant gilts.ResultsData were available from 48 gilts across three groups: a challenge control group (n = 16), which received no vaccination; a revaccination group (n = 16), which received ReproCyc® PRRS EU on Days 0 and 56; and a single vaccination group (n = 16), which received ReproCyc® PRRS EU on Day 56. All gilts were PRRSV RNA-negative (based on reverse transcription and quantitative polymerase chain reaction [RT-qPCR]) and PRRSV seronegative (based on enzyme-linked immunosorbent assay [ELISA]) at Day 0. All gilts were challenged with PRRSV strain 190136 on Day 91.Viral RNA loads in both vaccination groups were significantly reduced compared with the challenge control group on Days 98 (P < 0.0001) and 101 (P < 0.0001), indicating that vaccinated gilts were better able to respond to challenge than unvaccinated gilts. At all timepoints following challenge, mean viral RNA load and the percentage of PRRSV RNA-positive gilts were numerically higher in the single-vaccination group than in the revaccination group; these differences were statistically significant on Day 101 (P = 0.0434). Furthermore, viremia levels after challenge were significantly lower in the revaccination group than in the single-vaccination group based on median area under the curve (AUC) values for viral RNA load from Day 91 to Day 112, suggesting that revaccinated gilts had better protection from viral infection than gilts who received a single vaccination. Protection from viremia did not correlate with the proportion of seropositive gilts on Day 91. In the single-vaccination group, 94% of pigs were seropositive on Day 91 compared with 56% in the revaccination group. Vaccination was well tolerated and no safety concerns were identified.ConclusionsBoth single-vaccination and revaccination with ReproCyc® PRRS EU were effective in reducing PRRSV viremia post-challenge. These findings have important implications for herd management as both the single-vaccination and revaccination schedules protect against PRRSV challenge, with revaccination appearing to provide better protection from viremia than single vaccination.

Gilt Vaccination with a Mixed Administration of a PRRS MLV and a PPV1 Subunit Vaccine Protects against Heterologous PRRSV1 Infection and Prevents Detrimental Effects on Piglet Performance

“…In addition, a group of non-vaccinated, non-challenged control gilts was included in experiment B (i.e., group 3B-SC); these remained seronegative and viremia negative throughout the study, which reinforces the previous statement. The lack of observed vaccine-induced viremia by challenge was probably due to the resolution of viremia before 14 days post-vaccination, as previously described for the used PRRS MLV1 vaccine [11].…”

“…Thus, the aim of this study was to evaluate the efficacy of the combined administration of a PRRS MLV vaccine and a PPV1 subunit vaccine in gilts after challenge with a heterologous and pathogenic PRRSV1 strain under controlled laboratory conditions. The safety and efficacy of each vaccine applied individually have been shown in previous studies in the target species [11][12][13][14]. Moreover, the use of this combination has been already reported in the field; the safety and lack of antigen interference of the vaccines were proven in a farm where the circulation of a wild type PRRSV1 virus was confirmed [10].…”

“…In all cases, animals were challenged with the virulent, low-passage European PRRSV1 isolate 190136, propagated to a titer of 4.75 log10 median tissue culture infectious dose (TCID) 50 /mL. The origin of the challenge isolate as well as its genetic relationship with the vaccine master seed isolate have been formerly described [11,13]. Briefly, the PRRSV1 challenge isolate was originally derived from the lung tissue of a newborn piglet during a PRRS outbreak in Germany, in April 2004, and exhibits less than 87% genetic identity to the PRRS MLV vaccine isolate within the complete genome (or 88%, based on ORF5/ORF7 data).…”

“…Both ReproCyc ® PRRS EU and ReproCyc ® ParvoFLEX vaccines have been previously demonstrated to be safe and efficacious in several published works [10][11][12][13][14]. In this paper, we expand on our studies on the European-derived PRRS MLV vaccine by determining the OOI and DOI when mixed with the novel PPV1 subunit vaccine.…”

Bekämpfung des Porzinen Reproduktiven und Respiratorischen Syndroms in Sachsen und Thüringen

“…Damit lassen sich die klinischen und wirtschaftlichen Folgen verringern. Im Fall der PRRS-Impfung ist eine Verhinderung der Infektion nicht vollständig möglich [28] [29]. Gleichwohl wird diese Impfung zur Stabilisierung von Beständen eingesetzt [26][29] [30].…”