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

Patricia Renson,Frédéric Paboeuf,Stéphane Gorin,Céline Deblanc,Sophie Mahé,Nicolas Barbier,Juliette Bougon,Olivier Bourry,Mireille Le Dimna,Gaëlle Simon

doi:10.3390/vaccines9040356

Abstract

Modified-live vaccines (MLVs) against porcine reproductive and respiratory syndrome viruses (PRRSVs) are usually administrated to piglets at weaning when swine influenza A virus (swIAV) infections frequently occur. SwIAV infection induces a strong interferon alpha (IFNa) response and IFNa was shown to abrogate PRRSV2 MLV replication and an inherent immune response. In this study, we evaluated the impacts of swIAV infection on the replication of a PRRSV1 MLV (MLV1), post-vaccine immune responses and post-challenge vaccine efficacy at both the systemic and pulmonary levels. Piglets were either swIAV inoculated and MLV1 vaccinated 6 h apart or singly vaccinated or mock inoculated and mock vaccinated. Four weeks after vaccination, the piglets were challenged with a PRRSV1 field strain. The results showed that swIAV infection delayed MLV1 viremia by six days and post-vaccine seroconversion by four days. After the PRRSV1 challenge, the swIAV enhanced the PRRSV1-specific cell-mediated immunity (CMI) but the PRRSV1 field strain viremia was not better controlled. High IFNa levels that were detected early after swIAV infection could have been responsible for both the inhibition of MLV1 replication and CMI enhancement. Thus, whereas swIAV infection had a negative impact on humoral responses post-vaccination, it did not interfere with the protective effectiveness of the PRRSV MLV1 in our experimental conditions.

Highlights

Porcine reproductive and respiratory syndrome (PRRS) is a viral disease of swine with huge economic impact worldwide, characterized by reproductive failures in pregnant sows and respiratory disorders and growth retardation in piglets [1,2]
The objectives of the present study were to evaluate in specific pathogen free (SPF) piglets the impact of an H1N2 swine influenza A virus (swIAV) infection on (i) the replication of a PRRSV1 modified-live vaccines (MLVs) (MLV1) and (ii) the induction of the post-vaccination immune response, investigating the potential role of interferon alpha (IFNa) in these interactions
The objective of this study was to assess the hypothesis that a swIAV infection could affect the vaccine viremia, the post-vaccination immune response and the vaccine efficacy of an MLV1 in piglets, possibly through the production of large quantities of the anti-viral cytokine IFNa

Summary

Introduction

Porcine reproductive and respiratory syndrome (PRRS) is a viral disease of swine with huge economic impact worldwide, characterized by reproductive failures in pregnant sows and respiratory disorders and growth retardation in piglets [1,2]. The disease is caused by PRRS viruses (PRRSVs), which are single-strand positive sense-RNA viruses that belong to the Arteriviridae family and exist as two different species originating from Europe for the PRRSV1 or from North America for the PRRSV2 (recently re-named as Betaarterivirus suid 1 and 2, respectively) [3,4]. Nowadays, both species are distributed worldwide but only. We suggested that viral infections, through interferon alpha (IFNa) secretion, could affect the efficacy of the PRRSV MLV1 in the field [8]

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