Scientists have discovered a gene in the DNA of pigs that is needed by a deadly virus to cause infection.

Their discovery could inform the development of pigs resistant to African swine fever, a swift acting, severe condition that causes widespread illness and death, incurring high losses for the pork industry.

ASF has killed more than 200 million pigs worldwide, is a major issue across Asia, and has the potential to cause major outbreaks in Europe and America.

A team of researchers found that the gene, which is involved in the pig immune system, is essential for replication of the ASF virus.

Their finding raises the possibility of amending the gene, using gene editing, to develop pigs that are resistant to the disease. It offers scope for managing the infection, for which no vaccine or treatment is currently available.

Immunity proteins
A team led by the Friedrich-Loeffler Institute with the Roslin Institute sought to pinpoint which pig genes were needed for the virus to replicate.

In lab tests they examined a collection of pig cells, each one edited to lack a specific gene compared with the rest, to observe how they responded to ASF virus.

Their analysis pointed towards a suite of genes that produce proteins associated with the immune response to infections, known as the MHC-II complex, as key to enabling the virus to take hold.

Researchers were able to determine that a single protein in the MHC-II complex, known as SLA-DM, is essential for replication of the virus in cells.

"The collaboration with the Roslin Institute enabled us to use a CRISPR/Cas9-based gene knockout library to identify the cellular MHC II protein SLA-DM as a crucial factor in ASFV infection. This exciting finding not only improves our understanding of the biology of ASFV, but may also allow the development of new control measures," said Dr. Katrin Pannhorst, Friedrich-Loeffler-Institute.

"This collaboration brings together the Friedrich-Loeffler Institute’s capacity to study ASF virus in the lab, and gene-editing tools developed at the Roslin Institute," said Dr Finn Grey, Roslin Institute. "Our study points to genes that are candidates for editing to develop pigs resistant to African swine fever. Our study identifies target genes for editing to develop pigs resistant to African swine fever. Although more work is required, this finding represents an important first step towards the generation of ASF-resistant pigs."

Further research should seek to understand the biological processes in which virus particles and SLA-DM proteins interact, the team suggests.

The study was published in Scientific Reports.