In vitro and ex vivo analyses of co-infections with swine influenza and porcine reproductive and respiratory syndrome viruses

Abstract

Viral respiratory diseases remain problematic in swine. Among viruses, porcine reproductive and respiratory syndrome virus (PRRSV) and swine influenza virus (SIV), alone or in combination, are the two main known contributors to lung infectious diseases. Previous studies demonstrated that experimental dual infections of pigs with PRRSV followed by SIV can cause more severe disease than the single viral infections. However, our understanding of the impact of one virus on the other at the molecular level is still extremely limited. Thus, the aim of the current study was to determine the influence of dual infections, compared to single infections, in porcine alveolar macrophages (PAMs) and precision cut lung slices (PCLS). PAMs were isolated and PCLS were acquired from the lungs of healthy 8-week-old pigs. Then, PRRSV (ATCC VR-2385) and a local SIV strain of H1N1 subtype (A/Sw/Saskatchewan/18789/02) were applied simultaneously or with 3h apart on PAMs and PCLS for a total of 18 h. Immuno-staining for both viruses and beta-tubulin, real-time quantitative PCR and ELISA assays targeting various genes (pathogen recognition receptors, interferons (IFN) type I, cytokines, and IFN-inducible genes) and proteins were performed to analyze the cell and the tissue responses. Interference caused by the first virus on replication of the second virus was observed, though limited. On the host side, a synergistic effect between PRRSV and SIV co-infections was observed for some transcripts such as TLR3, RIG-I, and IFNβ in PCLS. The PRRSV infection 3h prior to SIV infection reduced the response to SIV while the SIV infection prior to PRRSV infection had limited impact on the second infection. This study is the first to show an impact of PRRSV/SIV co-infection and superinfections in the cellular and tissue immune response at the molecular level. It opens the door to further research in this exciting and intriguing field.

Association of the presence of influenza A virus and porcine reproductive and respiratory syndrome virus in sow farms with post-weaning mortality

“…The lack of samplings in which simultaneous circulation of these two pathogens could be demonstrated is likely related with the PRRSV status of the sow farms at weaning: herds were stable for the most part of the study and by definition very low number of PRRSV-positive pigs would be weaned. Still, a significantly lower incidence of PRRSV in H1N1 IAV-positive farms has been described in the past, what could be also reflecting more complex interactions between both viruses, or the impact of management measures to control one of the pathogens (Dobrescu et al, 2014;Jimenez et al, 2014). Infections with either pathogen could have also occurred after weaning in the WF site, what would have impacted the postweaning mortality.…”

“…In our study, there were no batches that tested positive to both IAV and PRRSV in the sow farm, which made impossible to evaluate the likely interaction between the two pathogens. Recent in-vitro and ex-vivo studies have demonstrated a synergistic effect of co-infections with both IAV and PRRSV, although the clinical implications of this finding could not be clearly established (Dobrescu et al, 2014). Concomitant infection with PRRSV was also found to impair IAV vaccine efficacy (Kitikoon et al, 2009), but there is conflicting evidence on the effect of a combined infection under experimental conditions (Van Reeth et al, 1996;Pol et al, 1997).…”

“…Even though the main impact of PRRSV infection is due to the occurrence of reproductive failure and increased preweaning mortality (Zimmerman et al, 2006), PRRSV has been also associated with respiratory issues and increased postweaning mortality (Dewey et al, 2006), with in-vivo and in-vitro data suggesting that co-infection with IAV may increase the severity of disease (Van Reeth et al, 1996;Kitikoon et al, 2009;Dobrescu et al, 2014). Control and elimination of PRRSV in breeding herds can be pursued using different strategies with the common goal to wean non-infected piglets (Corzo et al, 2010).…”

Dynamic Virus-Bacterium Interactions in a Porcine Precision-Cut Lung Slice Coinfection Model: Swine Influenza Virus Paves the Way for Streptococcus suis Infection in a Two-Step Process

“…PCLS have been used previously to study a variety of viral infections, such as SIV and PRRS (4,29), but has hardly been used for bacterial pathogens (30). Porcine PCLS have not yet been used for viral-bacterial coinfections.…”

Lack of strong anti-viral immune gene stimulation in Torque Teno Sus Virus1 infected macrophage cells

“…Each transfection experiment was repeated twice with two technical replicates (total of 4 values). A panel of 22 immune genes and 5 housekeeping genes were examined, essentially as described previously (Dobrescu et al, 2014). The immune genes studied included IFN-α, IFN-β, Mx1, Mx2, OAS-1, PKR, RNaseL (innate immune genes), IFN-ɣ, IL-10,IL-13, IL-4 (adaptive immune genes), IL-1β, IL-6, NLRP3, TNF-α, TRAIL (inflammatory genes), SOCS-1, PD-1 (regulatory genes), TLR9, DAI-ZBP-1 ( DNA pattern recognition receptors) and β2M, HPRT,GAPDH,HPL-19,TBP-1 (house-keeping genes).…”