Vet Microbiol. 2016 Aug 30;192:10-20. doi: 10.1016/j.vetmic.2016.06.006. Epub 2016 Jun 16.

Factors associated with herd-level PRRSV infection and age-time to seroconversion in farrow-to-finish herds.

Fablet C1, Marois-Créhan C2, Grasland B3, Simon G4, Rose N5.

Author information

1

Agence Nationale de Sécurité Sanitaire (Anses), Unité Epidémiologie et Bien-Etre du Porc, B.P. 53, 22440 Ploufragan, France; Université Bretagne Loire, Ploufragan, France. Electronic address: christelle.fablet@anses.fr.

2

Agence Nationale de Sécurité Sanitaire (Anses), Unité Mycoplasmologie Bactériologie, B.P. 53, 22440 Ploufragan, France; Université Bretagne Loire, Ploufragan, France.

3

Agence Nationale de Sécurité Sanitaire (Anses), Unité Génétique Virale et Biosécurité, B.P. 53, 22440 Ploufragan, France; Université Bretagne Loire, Ploufragan, France.

4

Agence Nationale de Sécurité Sanitaire (Anses), Unité Virologie Immunologie Porcines, B.P. 53, 22440 Ploufragan, France; Université Bretagne Loire, Ploufragan, France.

5

Agence Nationale de Sécurité Sanitaire (Anses), Unité Epidémiologie et Bien-Etre du Porc, B.P. 53, 22440 Ploufragan, France; Université Bretagne Loire, Ploufragan, France.

Abstract

Factors associated with porcine reproductive and respiratory syndrome virus (PRRSV) infection were investigated in 109 herds. Serums from four batches of pigs (4, 10, 16 and 22 weeks, 15 pigs/batch) were tested by ELISA for PRRSV antibodies. Infection by Mycoplasma hyopneumoniae (Mhp), Actinobacillus pleuropneumoniae, H1N1 and H1N2 swine influenza A viruses (swIAV) and PCV2 were detected by specific serological or PCR tests. Data related to herd characteristics, biosecurity, management housing and climatic conditions were collected during a herd visit. Factors associated with the herd's PRRSV seropositive status were identified by logistic regression. Large herd size, the lack of disinsectisation in the gestation facilities, on-farm semen collection, a short time-period for gilt quarantine and a low temperature setpoint for the ventilation controller in the fattening room significantly increased the odds of a herd being seropositive for PRRSV. Infection by Mhp and H1N2 swIAV were associated with a PRRSV seropositive status. A Cox proportional hazards model was used to identify the factors associated with the age-time to seroconversion in infected herds. Joint housing for the gilts and sows when lactating, a large nursery pen, a small number of pens per fattening room and lack of all-in all-out management in the fattening section significantly reduced the age-time to seroconversion. A small range of temperatures controlling ventilation rate in the nursery room was also associated with time to PRRSV seroconversion. Infection by Mhp and a high PCV2 infection pressure were associated with a shorter time to seroconversion. Biosecurity measures minimising the risk of introducing PRRSV into the herd, management practices reducing contacts between animals from different batches and within batches and favourable climatic conditions should be implemented to better control PRRSV infection. 

Copyright © 2016. Published by Elsevier B.V.

KEYWORDS: 

Logistic regression; PRRS; Risk factors; Survival analysis

PMID:

 

27527759

 

DOI:

 

10.1016/j.vetmic.2016.06.006

Evaluation of a 20 year old MLV vaccine on recent PRRSv isolates

Evaluation of a 20 year old porcine reproductive and respiratory syndrome (PRRS) modified live vaccine (Ingelvac (R) PRRS MLV) against two recent type 2 PRRS virus isolates in South Korea

By:Jeong, J (Jeong, Jiwoon)^[ 1 ] ; Choi, K (Choi, Kyuhyung)^[ 1 ] ; Kang, I (Kang, Ikjae)^[ 1 ] ; Park, C (Park, Changhoon)^[ 1 ] ; Chae, C (Chae, Chanhee)^[ 1 ]

VETERINARY MICROBIOLOGY

Volume: 192

 

Pages: 102-109

DOI: 10.1016/j.vetmic.2016.07.006

Published: AUG 30 2016

View Journal Information

Abstract

Type 2 porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV) was first isolated in Korea in 1994. The commercial PRRS modified live vaccine (Ingelvac (R) PRRS MLV, Boehringer Ingelheim Vetmedica Inc., St. Joseph, Missouri, USA) based on type 2 PRRSV, was first licensed for use in 3- to 18-week-old pigs in Korea in 1996. The objective of the present study was to evaluate the efficacy of this 20 year old commercial PRRS modified live vaccine (MLV) against two recent PRRSV isolates. Two genetically distant type 2 PRRSV strains (SNUVR150004 for lineage 1 and SNUVR150324 for lineage 5), isolated in 2015, were used as challenge virus. Regardless of the challenge virus, vaccination of pigs effectively reduced the level of viremia, the lung lesions, and of the PRRSV antigen within the lung lesions. The induction of virus specific interferon-gamma secreting cells by the PRRS vaccine produced a protective immune response, leading to the reduction of PRRSV viremia. There were no significant differences in efficacy against the two recently isolated viruses by the PRRS MLV based on virological results, immunological responses, and pathological outcomes. This study demonstrates that the PRRS MLV used in this study is still effective against recently isolated heterologous type 2 PRRSV strains even after 20 years of use in over 35 million pigs (C) 2016 Elsevier B.V. All rights reserved.

Keywords

Author Keywords:Porcine reproductive and respiratory; syndrome virus; Respiratory disease; PRRSV modified live vaccine; Vaccine efficacy

KeyWords Plus:POLYMERASE-CHAIN-REACTION; REAL-TIME PCR; NORTH-AMERICAN; LELYSTAD VIRUS; PROTECTIVE IMMUNITY; MOLECULAR-BIOLOGY; CHALLENGE; INFECTION; PIGS; US

Author Information

Reprint Address: Chae, C (reprint author) 

Seoul Natl Univ, Coll Vet Med, Dept Vet Pathol, 1 Gwanak Ro, Seoul 151742, South Korea.

Addresses:

[ 1 ] Seoul Natl Univ, Coll Vet Med, Dept Vet Pathol, 1 Gwanak Ro, Seoul 151742, South Korea

E-mail Addresses:swine@snu.ac.kr

Effect of maternally-derived antibodies on piglet response to PRRSv infection

Vet Microbiol. 2016 Aug 30;192:175-80. doi: 10.1016/j.vetmic.2016.07.014. Epub 2016 Jul 25.

Maternally-derived antibodies (MDAs) impair piglets' humoral and cellular immune responses to vaccination against porcine reproductive and respiratory syndrome (PRRS).

Fablet C1, Renson P2, Eono F3, Mahé S4, Eveno E3, Le Dimna M4, Normand V5, Lebret A5, Rose N3, Bourry O4.

Author information

Abstract

The influence of maternally-derived antibodies (MDAs) on the post-vaccination humoral and cellular immune responses in piglets vaccinated against PRRS was studied. The piglets came from a vaccinated breeding herd. Thirty piglets with a low (A-) or high level (A+) of PRRSV-neutralizing MDAs were vaccinated (V+) with a modified live vaccine at 3 weeks of age. Blood samples were collected before vaccination and then at 2, 4, 8 and 14 weeks post-vaccination (WPV). The samples were analysed to detect the vaccine viraemia (RT-PCR) and quantify the post-vaccination humoral (ELISA and virus neutralisation test) and cellular (ELISPOT IFNγ) immune responses. PRRSV vaccine strain was detected in 60%, 64%, 36% and 0% of A-V+ piglets 2, 4, 8 and 14 WPV respectively. No virus was detected in A+V+ piglets during the first four WPV but 32% and 6% of A+V+ piglets were PCR-positive at 8 and 14 WPV. Eighty-five percent of A-V+ piglets and 0% of A+V+ piglets seroconverted (ELISA) between 2 and 4 WPV. Neutralising antibodies appeared 4 WPV in the A-V+ piglets and 14 WPV in the A+V+ piglets. The number of PRRSV-specific IFNγ-secreting cells was significantly higher in A-V+ piglets at 2 and 4 WPV than in A+V+ piglets. These results show that MDAs can affect both post-vaccination humoral and cellular immuneresponses in piglets. Further studies are required to assess the impact of MDAs on vaccine efficacy following a PRRSV challenge and its ability to reduce viral transmission. 

Copyright © 2016 Elsevier B.V. All rights reserved.

KEYWORDS: 

Immune response; Maternal neutralizing antibody; PRRS; Vaccination

PMID:

 

27527780

 

DOI:

 

10.1016/j.vetmic.2016.07.014

Chimeric PRRSV to enhance cross-protection among strains

Vaccine. 2016 Aug 5;34(36):4335-42. doi: 10.1016/j.vaccine.2016.06.069. Epub 2016 Jul 9.

Attempts to enhance cross-protection against porcine reproductive and respiratory syndromeviruses using chimeric viruses containing structural genes from two antigenically distinct strains.

Sun D1, Khatun A2, Kim WI3, Cooper V4, Cho YI1, Wang C4, Choi EJ5, Yoon KJ6.

Author information

1

Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50010, USA.

2

College of Veterinary Medicine, Chonbuk National University, Iksan, Republic of Korea.

3

College of Veterinary Medicine, Chonbuk National University, Iksan, Republic of Korea. Electronic address: kwi0621@jbnu.ac.kr.

4

Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50010, USA.

5

Viral Disease Division, Animal Plant Fisheries Quarantine Agency, Anyang, Republic of Korea.

6

Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50010, USA; Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50010, USA. Electronic address: kyoon@iastate.edu.

Abstract

Due to significant antigenic variations between field isolates of porcine reproductive and respiratory syndrome virus (PRRSV), suboptimal cross-protection between different viruses impedes the effective control of PRRS via vaccination. Our previous study showed that chimeric viruses containing mixed structural genes from two distinct strains (VR2332 and JA142) of PRRSV were highly susceptible to the viral neutralizing activity of antisera generated against both parental strains. In this study, three chimeric viruses (JAP5, JAP56 and JAP2-6) were constructed by replacing ORF5, ORFs 5 and 6, and ORFs 2-6 of VR2332 with the corresponding genes of JA142, respectively, and their ability to confer cross-protection against challenge with the VR2332 and JA142 strains was evaluated in vivo. A total of 114 pigs were divided into 6 groups, and each group was intramuscularly injected with one of the 3 chimeric viruses (n=16 pigs per group), VR2332 (n=24), JA142 (n=24), or sham inoculum (n=18). At 44days post-inoculation (dpi), these pigs were further divided into 15 groups (n=6 or 8 pigs per group) and intranasally challenged with VR2332, JA142, or sham inoculum. All pigs inoculated with one of the chimeric viruses prior to challenge had lower viremia levels than the challenge control pigs. Prior inoculation with JAP56 markedly decreased viremia to nearly undetectable levels in pigs challenged with either VR2332 or JA142. These results suggest that chimeric viruses harboring mixed structural genes from two distinct PRRSV strains can provide protection against both donor viruses. 

Copyright © 2016 Elsevier Ltd. All rights reserved.

KEYWORDS: 

Chimeric virus; Cross protection; Infectious clone; PRRSV; Reverse genetics; Structural genes; Vaccine

PMID:

 

27406935

 

DOI:

 

10.1016/j.vaccine.2016.06.069

Pig genetic factors influencing response to PRRSV infection

Comparison of host genetic factors influencing pig response to infection with two North American isolates of porcine reproductive and respiratory syndrome virus

By: Hess, Andrew S.; Islam, Zeenath; Hess, Melanie K.; et al.

GENETICS SELECTION EVOLUTION   Volume: 48     Article Number: 43   Published: JUN 20 2016

Background: Porcine reproductive and respiratory syndrome (PRRS) is one of the most important swine diseases in the world and genetic selection of pigs for increased resistance to PRRS is an attractive method to improve the health status of the swine herd. This study compared phenotypic and genetic responses to infection with one of two genetically distinct type 2 PRRS virus (PRRSV) isolates: NVSL-97-7895 (NVSL) and KS-2006-72109 (KS06), and evaluated whether the single nucleotide polymorphism (SNP) WUR10000125 (WUR) on chromosome 4 that was associated with viral load and weight gain under infection with NVSL also has an effect on response to infection across North American PRRSV isolates. Wood's lactation curve was fitted to repeated viremia measurements to derive five curve characteristics that were evaluated.

Results: Infection with NVSL was characterized by reaching a 14 +/- 2 % higher peak viremia (PV) 2.5 +/- 0.6 days earlier (time to peak; TP) than KS06, followed by 36 +/- 1 % faster virus clearance, which occurred 3.9 +/- 0.7 days sooner. Weight gain from 0 to 42 days post-infection (WG) tended to be higher under infection with KS06 than NVSL (3.7 +/- 1.5 kg). Estimates of heritability were moderate for both PRRSV isolates for viral load from 0 to 21 days post-infection (VL) (NVSL: 0.31 +/- 0.06; KS06: 0.51 +/- 0.09) and WG (NVSL: 0.33 +/- 0.06; KS06: 0.31 +/- 0.09). Strong negative genetic correlations were observed between VL and WG for both NVSL (-0.74 +/- 0.10) and KS06 (-0.52 +/- 0.17) infected pigs. Pigs with genotype AB at the WUR SNP had a more desirable phenotype than AA pigs for all traits under infection with NVSL, but only for VL and PV with KS06; effects on other traits were smaller and not significantly different from zero (P > 0.05). Genetic correlations of host response between isolates were strong for VL, WG and PV. Accounting for WUR genotype had little impact on these correlations, suggesting that response to PRRSV infection has a substantial polygenic component that is common between these two isolates.

Conclusions: These results suggest that the KS06 PRRSV isolate is less virulent than NVSL but that genetic selection for increased resistance to either of these genetically distinct isolates is expected to increase resistance to the other isolate.

======================================

Genetic and genomic basis of antibody response to porcine reproductive and respiratory syndrome(PRRS) in gilts and sows

By: Serao, Nick V. L.; Kemp, Robert A.; Mote, Benny E.; et al.

GENETICS SELECTION EVOLUTION   Volume: 48     Article Number: 51   Published: JUL 14 2016

Background: Our recent research showed that antibody response to porcine reproductive and respiratory syndrome (PRRS), measured as sample-to-positive (S/P) ratio, is highly heritable and has a high genetic correlation with reproductive performance during a PRRS outbreak. Two major quantitative trait loci (QTL) on Sus scrofa chromosome 7 (SSC7; QTL(MHC) and QTL(130)) accounted for similar to 40 % of the genetic variance for S/P. Objectives of this study were to estimate genetic parameters for PRRS S/P in gilts during acclimation, identify regions associated with S/P, and evaluate the accuracy of genomic prediction of S/P across populations with different prevalences of PRRS and using different single nucleotide polymorphism (SNP) sets.

Methods: Phenotypes and high-density SNP genotypes of female pigs from two datasets were used. The outbreak dataset included 607 animals from one multiplier herd, whereas the gilt acclimation (GA) dataset included data on 2364 replacement gilts from seven breeding companies placed on health-challenged farms. Genomic prediction was evaluated using GA for training and validation, and using GA for training and outbreak for validation. Predictions were based on SNPs across the genome (SNPAll), SNPs in one (SNPMHC and SNP130) or both (SNPSSC7) QTL, or SNPs outside the QTL (SNPRest).

Results: Heritability of S/P in the GA dataset increased with the proportion of PRRS-positive animals in the herd (from 0.28 to 0.47). Genomic prediction accuracies ranged from low to moderate. Average accuracies were highest when using only the 269 SNPs in both QTL regions (SNPSSC7, with accuracies of 0.39 and 0.31 for outbreak and GA validation datasets, respectively. Average accuracies for SNPALL, SNPMHC, SNP130, and SNPRest were, respectively, 0.26, 0.39, 0.21, and 0.05 for the outbreak, and 0.28, 0.25, 0.22, and 0.12, for the GA validation datasets.

Conclusions: Moderate genomic prediction accuracies can be obtained for PRRS antibody response using SNPs located within two major QTL on SSC7, while the rest of the genome showed limited predictive ability. Results were obtained using data from multiple genetic sources and farms, which further strengthens these findings. Further research is needed to validate the use of S/P ratio as an indicator trait for reproductive performance during PRRS outbreaks.

Efficacy of type 1 MLV vaccine against a field type 2 PRRSv challenge

Efficacy of commercial genotype 1 porcine reproductive and respiratory syndrome virus (PRRSV) vaccine against field isolate of genotype 2 PRRSV

By:Ko, SS (Ko, Seong-sik)^[ 1 ] ; Seo, SW (Seo, Sang-won)^[ 1 ] ; Sunwoo, SY (Sunwoo, Sun-young)^[ 1 ] ; Yoo, SJ (Yoo, Sung J.)^[ 1 ] ; Kim, MH (Kim, Myung-hyee)^[ 2 ] ; Lyoo, YS (Lyoo, Young S.)^[ 1 ]

VETERINARY IMMUNOLOGY AND IMMUNOPATHOLOGY

Volume: 172

 

Pages: 43-49

DOI: 10.1016/j.vetimm.2016.02.016

Published: APR 2016

View Journal Information

Abstract

Although several recent studies have found that type 1 porcine reproductive and respiratory syndrome virus (PRRSV) modified live virus (MLV) vaccine showed appreciable levels of cross-protection against type 2 PRRSV infection, the possibility of cross-protection between two genotype of PRRSV is still controversial. To determine potential protective efficacy against hetero-genotype field strain of PRRSV and to improve understandings of the mechanisms underlying performance improvement after infection in vaccinated animals, piglets were vaccinated with type 1 PRRSV MLV vaccine and challenged with type 2 field strain of PRRSV. As a result, vaccinated animals gained on average 8.45 kg in comparison to 4.77 kg measured in non-vaccinated animals during a 3-week period after viral challenge, which shows using a certain PRRSV vaccine could be clinically effective against heterologous genotypic virus challenge. In vaccinated animals, viremia was reduced and cleared rapidly, whilst viral load was much higher and reduced more slowly, indicating rebound viremia in non-vaccinated animals. The titers of neutralizing antibody against the type 2 PRRSV did not exceed the protective level in any animal from both vaccinated and control groups. Instead, antibody avidity of vaccinated animals was much higher than in the control group clearly. Furthermore, a strong negative correlation between antibody avidity and viremia was noted in 80% of vaccinated animals. Through those results from tests evaluating degree of antibody maturation and its relevance with clearing viremia, it could be suggested that non-neutralizing antibodies induced by vaccination prior to challenge might play a key role in protection against PRRSV infection, especially in early time course. (C) 2016 Elsevier B.V. All rights reserved.

Author Information

Reprint Address: Lyoo, YS (reprint author) 

Konkuk Univ, Dept Immunopathol, Coll Vet Med, Neungdong Ro120, Seoul, South Korea.

Addresses:

	[ 1 ] Konkuk Univ, Dept Immunopathol, Coll Vet Med, Neung Dong St 120, Seuol, South Korea
	[ 2 ] Hipra Korea Inc, Jeongjail Ro 177, Songnam, Gyeonggi Do, South Korea

E-mail Addresses:lyoo@konkuk.ac.kr

Publisher

ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS

A PRRSv candidate vaccine based on the synthetic attenuated virus engineering approach

Vaccine. 2016 Nov 4;34(46):5546-5553. doi: 10.1016/j.vaccine.2016.09.049. Epub 2016 Oct 11.

A porcine reproductive and respiratory syndrome virus candidate vaccine based on the synthetic attenuated virus engineering approach is attenuated and effective in protecting against homologous virus challenge.

Evenson D1, Gerber PF2, Xiao CT1, Halbur PG1, Wang C1, Tian D3, Ni YY3, Meng XJ3, Opriessnig T4.

Author information

• 1Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA.
• 2The Roslin Institute and The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK.
• 3Department of Biomedical Sciences and Pathobiology, College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.
• 4Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA; The Roslin Institute and The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK. Electronic address: Tanja.Opriessnig@roslin.ed.ac.uk.

Abstract

Current porcine reproductive and respiratory syndrome virus (PRRSV) vaccines sometimes fail to provide adequate immunity to protect pigs from PRRSV-induced disease. This may be due to antigenic differences among PRRSV strains. Rapid production of attenuated farm-specific homologous vaccines is a feasible alternative to commercial vaccines. In this study, attenuation and efficacy of a codon-pair de-optimized candidate vaccine generated by synthetic attenuated virus engineering approach (SAVE5) were tested in a conventional growing pig model. Forty pigs were vaccinated intranasally or intramuscularly with SAVE5 at day 0 (D0). The remaining 28 pigs were sham-vaccinated with saline. At D42, 30 vaccinated and 19 sham-vaccinated pigs were challenged with the homologous PRRSV strain VR2385. The experiment was terminated at D54. The SAVE5 virus was effectively attenuated as evidenced by a low magnitude of SAVE5 viremia for 1-5 consecutive weeks in 35.9% (14/39) of the vaccinated pigs, lack of detectable nasal SAVE5 shedding and failure to transmit the vaccine virus from pig to pig. By D42, all vaccinated pigs with detectable SAVE5 viremia also had detectable anti-PRRSV IgG. Anti-IgG positive vaccinated pigs were protected from subsequent VR2385 challenge as evidenced by lack of VR2385 viremia and nasal shedding, significantly reduced macroscopic and microscopic lung lesions and significantly reduced amount of PRRSV antigen in lungs compared to the non-vaccinated VR2385-challenged positive control pigs. The nasal vaccination route appeared to be more effective in inducing protective immunity in a larger number of pigs compared to the intramuscular route. Vaccinated pigs without detectable SAVE5 viremia did not seroconvert and were fully susceptible to VR2385 challenge. Under the study conditions, the SAVE approach was successful in attenuating PRRSV strain VR2385 and protected against homologous virus challenge. Virus dosage likely needs to be adjusted to induce replication and protection in a higher percentage of vaccinated pigs.

Copyright © 2016 Elsevier Ltd. All rights reserved.

KEYWORDS: 

Attenuation; Efficacy; Porcine reproductive and respiratory syndrome virus (PRRSV); Synthetic attenuated virus engineering (SAVE); Vaccine

PMID:

 

27742217

 

DOI:

 

10.1016/j.vaccine.2016.09.049