Analyses of Co-infections with Swine Influenza and PRRS Viruses11 March 2014
In the first study of its type, researchers studied the effects of two different respiratory viruses - Swine Influenza Virus (SIV) and Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) on pig lung tissue and immune response.
Viral respiratory diseases remain problematic in swine. Among viruses, PRRSV and SIV, alone or in combination, are the two main known contributors to lung infectious diseases.
In the journal, Veterinary Microbiology, first-named author, I. Dobrescu and coauthors report that previous studies have demonstrated that experimental dual infections of pigs with PRRSV followed by SIV can cause more severe disease than the single viral infections.
Our understanding of the impact of one virus on the other at the molecular level is still extremely limited, however, so the aim of their 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 eight-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 three hours apart on PAMs and PCLS for a total of 18 hours.
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 analyse the cell and the tissue responses.
Interference caused by the first virus on replication of the second virus was observed, though to a limited extent.
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.
PRRSV infection three hours 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 super-infections in the cellular and tissue immune response at the molecular level, concluded Dobrescu and co-authors, who added that it opens the door to further research in this exciting and intriguing field.
Dobrescu I., B. Levast, K. Lai, M. Delgado-Ortega, S. Walker, S. Banman, H. Townsend, G. Simone, Y. Zhou, V. Gerdts and F. Meurens. 2014. In vitro and ex vivo analyses of co-infections with swine influenza and porcine reproductive and respiratory syndrome viruses. Veterinary Microbiology. 169 (1–2):18–32.