Deep Sequencing of Porcine Reproductive and Respiratory Syndrome Virus ORF7: A Promising Tool for Diagnostics and Epidemiologic Surveillance

ZDHHC3-LYPLA1 regulates PRRSV-2 replication through reversible palmitoylation

Porcine reproductive and respiratory syndrome virus (PRRSV) is a highly contagious swine pathogen, causing respiratory problems in piglets and reproductive failure in sows. Palmitoylation, catalyzed by zinc finger Asp-His-His-Cys (ZDHHC) domain-containing palmitoyl acyltransferases, plays intricate roles in virus infection. However, whether palmitoylation regulates PRRSV replication is incompletely understood. Here, we report that inhibition of palmitoylation by 2-bromo palmitate (2-BP) promotes PRRSV multiplication. ZDHHC3 is identified as the key palmitoyl transferase regulating PRRSV replication in PAMs infection. Mechanistically, ZDHHC3 catalyzes nucleocapsid (N) protein palmitoylation at cysteine 90. This modification prevents the Nsp9-N protein interaction and subsequent viral RNA synthesis. Furthermore, LYPLA1 de-palmitoylates N protein, thus counteracting the ZDHHC3's activity on PRRSV replication. Meanwhile, the administration of small-molecule inhibitor ML348 targeting LYPLA1 could hinder PRRSV-2 replication. In summary, our results underscore the critical role of reversible palmitoylation in PRRSV replication. These findings might provide potential new anti-PRRSV strategies.

Genome stability assessment of PRRS vaccine strain with new ARTIC-style sequencing protocol

A tiling amplicon sequencing protocol was developed to analyse the genome sequence stability of the modified live PRRSV vaccine strain, Porcilis MLV. The backbone of the ARTIC-style protocol was formed by 34 individual primer pairs, which were divided into two primer pools. Primer pairs were designed to amplify 532 to 588 bp fragments of the corresponding genomic region. The amplicons are suitable for sequencing on Illumina DNA sequencers with available 600-cycle sequencing kits. The concentration of primer pairs in the pools was optimized to obtain a balanced sequencing depth along the genome. Deep sequencing data of three vaccine batches were also analysed. All three vaccine batches were very similar to each other, although they also showed single nucleotide variations (SNVs) affecting less than 1 % of the genome. In the three vaccine strains, 113 to 122 SNV sites were identified; at these sites, the minority variants represented a frequency range of 1 to 48.7 percent. Additionally, the strains within the batches contained well-known length polymorphisms; the genomes of these minority deletion mutants were 135 to 222 bp shorter than the variant with the complete genome. Our results show the usefulness of ARTIC-style protocols in the evaluation of the genomic stability of PRRS MLV strains.