Vaccination at two weeks of age with Ingelvac PRRSFLEX® EU in the presence of maternally derived antibodies (MDA) protects piglets against a heterologous PRRSV1 challenge

  • 10 minutes
  • Expertise article
  • Christian Kraft; Marta Noguera; Poul H. Rathkjen; Marius Kunze, Karla Dreckmann; Rimma Hennies
Add to my reading list Remove from my reading list

Christian Kraft1; Marta Noguera1; Poul H. Rathkjen1; Marius Kunze3, Karla Dreckmann1; Rimma Hennies1

1Boehringer Ingelheim Veterinary Research Center GmbH & Co. KG, Hannover Germany; 2Boehringer Ingelheim AH Denmark A/S, Copenhagen, Denmark; 3Boehringer Ingelheim Vetmedica GmbH, Ingelheim, Germany; christian.kraft@boehringer-ingelheim.com

 

Introduction

Porcine Reproductive and Respiratory Syndrome (PRRS) Virus is one of the major pathogens in pigs that have a significant economic impact on the swine industry worldwide. Modified life vaccine (MLV) against PRRSV has been demonstrated as an effective tool to control clinical signs related to infection. In literature, it is described that maternally derived antibodies (MDA) might interfere with MLV vaccination efficacy.

Materials and methods

On a farm all sows of the breeding herd were vaccinated with ReproCyc PRRS® EU in a mass vaccination scheme. A total of 59 piglets were randomized in two groups, 30 piglets were vaccinated at two weeks of age, and 29 piglets remained untreated. At weaning piglets were transferred to a controlled laboratory environment. At 10 weeks of age piglets were challenged with a heterologous PRRSV1 strain and necropsied 10 days post challenge.

Blood was collected at birth, and at 2, 4, 6, 9, 10 weeks of age as well as at necropsy for serum (ELISA) and viremia (qPCR, necropsy only).

Lung tissue was collected at necropsy to detect viremia (qPCR). Lungs were investigated for PRRSv specific lesions and mean lung lesion scores were calculated.

Peripheral Blood Mononuclear Cells (PBMC) were collected before challenge and at necropsy and stimulated for a PRRSv specific Interferon (IFN)-γ response.

Results

Piglets of both groups were tested positive for MDA after colostrum intake. Mean antibody titers were declining over time in the untreated group and turned below the cutoff level of the test at 9 weeks of age. In contrast, the vaccinated piglets remained sero-positive throughout the time of challenge (1). After challenge both groups showed rising antibody levels with significantly higher levels in the vaccinated piglets (p<0.0001). Mean lung lesion scores were calculated at necropsy. The vaccinated piglets showed a significantly reduced score compared to the non-vaccinated group (p=0.0125).

Viremia was measured in the blood and in lung tissue at time of necropsy. All piglets of the non-vaccinated group were tested positive by qPCR while only 90% of the vaccinated animals were tested positive 10 days post challenge. Vaccinated piglets showed a significantly reduced viral load both in serum and in lung tissue compared to the non-vaccinated piglets (p<0.0465). Stimulation of PBMC before challenge showed no response to PRRSv specific stimulation in the non-vaccinated group while the vaccinated group showed a robust primary response. After challenge the non-vaccinated showed an immune response comparable to pre-challenge levels of the vaccinated group, however, the vaccinated group showed a significant raise in the number of PRRSv specific responding cells (p=0.0052).

Discussion

The transfer of maternally derived antibodies from sow to piglet has been shown to interfere with the antibody response to PRRSv vaccination (2). This study provided data that vaccination with Ingelvac PRRSFLEX® EU at two weeks of age is capable to induce a cellular and humoral immune response in the presence of MDA that leads to clinical protection by reducing viral load in tissue and serum as well as a reduction of lung lesions after controlled artificially challenge with a PRRSV1 strain. These results confirm previous experiences gathered in field situations were vaccinated piglets showed a significantly reduced viremia in a side-by-side study (3).

Conclusion

Ingelvac PRRSFLEX® EU is able to overcome limitations of other PRRSV1 MLV vaccines by providing protection against heterologous challenge in the presence of MDA.

References

  1. Kraft C. et al., 2019. PLoS One 14(10):e0223060
  2. Renson P. et al., 2019. Vaccine 37(31):4318–24.
  3. Balka G. et al., 2016. Porcine Health Management 2016 2:24