Grevelinger Janaïna

Abstract :

The swine influenza A virus (swIAV) primarily targets respiratory epithelial cells but also interacts with alveolar macrophages (AM), which can modulate their immune response. swIAV is part of the porcine respiratory disease complex, along with the porcine reproductive and respiratory syndrome virus (PRRSV), which replicates within AM. This thesis examines the interactions between these viruses during co- and super-infections, evaluating the impact of swIAV on 1) AM and their response to PRRSV, and 2) the immune response of pigs during subsequent infection with PRRSV.
We showed in vivo that swIAV induces an increase in the expression of pro-inflammatory cytokines in AM up to three weeks after virus inoculation. Other in vitro studies revealed that swIAV replicates abortively in AM while inhibiting the replication of PRRSV, likely through the induction of type I IFN through the induction of type I interferon, an effect amplified when AM are co-cultured with epithelial cells. Finally, we showed in vivo that a primary infection with swIAV, inoculated one week before PRRSV, does not interfere with the early stages of the second infection. However, several parameters of the cellular antiviral response, including PRRSV-specific Th1 lymphocytes, are significantly increased, which could lead to faster clearance of the virus at later stages of infection in animals pre-infected with swIAV.
These results highlight the complexity of interactions between viral infections and the importance of continuing research to better understand the underlying mechanisms and their implications for swine health.

Keywords:

Porcine respiratory disease complex, co-infection, super-infection, viral interactions, immune response, interference