miRNA-Mediated Regulation: Learning from Pseudorabies Virus Infected Pigs

MicroRNAs (miRNAs) are key regulators of gene expression. They are highly conserved across species, expressed across cell types, and active against a large proportion of the transcriptome.

Herpesviruses produce latent infections and are completely dependent upon latency as mode of persistence. Most of them encode miRNAs with targets in their own genomes and that of their host. Among alpha-herpesviruses, the Pseudorabies (PrV) is the most amenable to genetic manipulation, and its genome contains 11 miRNA genes clustered in the Large Latency Transcript (LLT) region. PrV establishes latent infections primarily in the trigeminal ganglia, and during this phase LLT is the only viral transcript detected.  

We used the pig-PrV system as a model to study the biological role of viral and host miRNAs in host-pathogen interaction. A mutant PrV clone was depleted of a miRNA cluster. An in vivo experimental infection was carried out to compare the ability of the mutant and wild type PrV to establish latency. RNA-seq and Small RNA-seq reads from trigeminal ganglia were mapped on the viral and pig genomes and analyzed using established pipelines. Validations of candidate interactions were carried out in PK15 and in a porcine neuroblast cell line.

All infected animals carried PrV in the latent state, but differences were found in both viral and host phenotypes between wild type and mutant virus infected samples, pointing to alterations of the host cell-mediated immune response.

These results will be presented and discussed in the framework of the AGEncode initiative for farm animals.