Whole-genome analysis of resilience based on the stability of reproduction performance during a porcine reproductive and respiratory syndrome virus outbreak in sows

The Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) is a very prevalent viral pathogen that can induce reproductive failure in infected sows. PRRSV infection can result in smaller litters, foetal death, late-term abortions and retarded growth of infected piglets. Not all sows respond equally to the infection partly due to genetic factors. In this study, we aimed to characterise the genetic variability of pig resilience to PRRSV infection by using a stability reproductive performance (SRP) index as a proxy of resilience. By comparing reproductive data from 183 sows, we selected 48 sows with extreme SRP values, measured as the difference in piglets lost at farrowings before and during a PRRSV outbreak. Short-read DNA fragments were sequenced from selected sows using an Illumina platform. The analysis of whole-genome sequencing information identified 16 genome regions associated with the SRP classification (cut-off P-value < 10⁻⁶). Functional evaluation of the positional candidates by gene-ontology identifiers and their participation in biological pathways were used to identify genes involved in virus entry and replication (vimentin, RAC1 and OAZ2) but also in immune responses from the host (IRF1, and IL4, IL5 and IL13). Importantly, genes related to chemokines, extracellular proteins and cell-to-cell junction integrity might contribute to placental microseparations, facilitating the trafficking of viral particles from sow to foetus that takes place during the pathogenesis of transplacental PRRSV infection. However, given the small number of animals in the study, these results shall need to be validated in larger populations.