Abstract
The objective of the present study was to determine the effects of the commercially available type 2 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV)-based modified live vaccine against type 1 and type 2 PRRSV challenge in pregnant sows. Half of the sows in the study were vaccinated with a type 2 PRRSV-based vaccine 4 weeks prior to artificial insemination while the other half remained non-vaccinated. Sows were then challenged intranasally with type 1 or type 2 PRRSV at 93 days of gestation. The sows which received the type 2 PRRSV-based vaccine followed by type 2 PRRSV challenge had significantly higher neutralizing antibody titers against type 2 PRRSV than they did against type 1 PRRSV. These same sows had higher frequencies of IFN-γ-secreting cells when stimulated with type 2 PRRSV compared to those stimulated with type 1 PRRSV. Subsequent virological evaluation demonstrated that the type 2 PRRSV-based vaccine reduced the type 2 PRRSV load but not the type 1 PRRSV load present in the blood of the sows. Additionally, vaccination of pregnant sows with the type 2 PRRSV-based vaccine effectively reduced the level of type 2 PRRSV nucleic acids observed in fetal tissues from type 2 PRRSV-challenged sows but did not reduce the level of type 1 PRRSV nucleic acid observed in fetal tissues from type 1 PRRSV-challenged sows. This study demonstrates that the vaccination of pregnant sows with the type 2 PRRSV-based vaccine protects against type 2 PRRSV challenge but does not protect against type 1 PRRSV challenge.
Highlights
Porcine Reproductive and Respiratory Syndrome (PRRS) Virus (PRRSV) is a widely disseminated and economically important swine virus that is known to cause reproductive failure in pregnant sows and respiratory disease in nursery and grower/finishing pigs [1]
Anti-Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) IgG antibodies were not detected in the serum samples at −28 days of gestation in sows from any of the 6 groups but were detected in the serum samples at days 0 (28 days post-vaccination), 56, and 93 of gestation in sows that received the PRRSV vaccine
This study clearly demonstrates that the vaccination of sows with the commercial type 2 PRRSV-based vaccine protects pregnant sows against heterologous type 2 PRRSV challenge but not against type 1 PRRSV challenge
Summary
Porcine Reproductive and Respiratory Syndrome (PRRS) Virus (PRRSV) is a widely disseminated and economically important swine virus that is known to cause reproductive failure in pregnant sows and respiratory disease in nursery and grower/finishing pigs [1]. The commercial modified live virus (MLV) vaccine (Ingelvac® PRRS MLV, Boehringer Ingelheim Vetmedica Inc., St. Joseph, MO, USA) based on type 2 PRRSV was first licensed for worldwide use in 3 to 18-week-old pigs in 1994 and in pregnant female breeding-stock pigs in 1996. MO, USA) based on type 2 PRRSV was first licensed for worldwide use in 3 to 18-week-old pigs in 1994 and in pregnant female breeding-stock pigs in 1996 This MLV vaccine has been used extensively by swine producers to protect pigs against PRRSV infection across the globe. The objective of this study was to determine the effects of the type 2 PRRSVbased vaccine against type 1 and type 2 PRRSV challenge in pregnant sows, using clinical, immunological, virological, and pathological measures for evaluation
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