# Molecular Characterization of a Recombinant NADC30-like PRRSV Strain with a Novel Gene Deletion Pattern in Nsp2 Gene

## TL;DR

A new PRRSV strain with unique gene deletions and recombinations was identified in China, offering insights into its evolution and potential vaccine development.

## Contribution

Discovery of a novel Nsp2 gene deletion pattern and mosaic genome structure in a PRRSV strain.

## Key findings

- HeB2023092 has a unique 41-amino acid deletion in Nsp2 and a mosaic genome with sequences from multiple PRRSV strains.
- The strain replicates in PAMs but not in Marc-145 cells and shows antigenic and glycosylation changes in GP3 and GP5.
- Recombination analysis revealed three distinct regions with genetic contributions from JXA1-like and NADC34-like strains.

## Abstract

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) continues to pose a significant worldwide challenge for swine production. In this study, we investigated a newly identified strain, HeB2023092, responsible for an outbreak in a pig farm in China. The detailed molecular analysis revealed that this strain is genetically related to NADC30-like PRRSV, but possesses a unique, previously unreported deletion pattern in its Nsp2 gene. Furthermore, we discovered its genetic makeup is a blend of different PRRSV strains, indicating it has undergone complex genetic mixing. The constant evolution makes PRRSV a difficult adversary. By monitoring these novel molecular changes and recombination patterns at viral genome level, we can develop more effective vaccines and control strategies to safeguard pig health.

PRRSV poses a persistent global challenge to the swine industry due to its rapid evolution. This study aimed to characterize a novel PRRSV2 strain, HeB2023092, isolated from a suspected outbreak in China in September 2023. We performed virus isolation in porcine alveolar macrophages (PAMs), genome sequencing, phylogenetic analysis, and comprehensive genetic characterization. HeB2023092 replicated effectively in PAMs but not in Marc-145 cells. Phylogenetic analysis consistently grouped it with NADC30-like strains (L1.8). Notably, genomic analysis revealed a unique 41-amino acid deletion (478–518 aa) in Nsp2, in addition to the characteristic 111-amino acid deletion of NADC30-like strains. Significant amino acid variations were also found in the antigenic epitopes and N-glycosylation patterns of GP3 and GP5. Comprehensive recombination analysis identified three distinct recombinant regions, revealing a mosaic genome with a predominant NADC30-like backbone. The backbone incorporated genetic sequences from JXA1-like (L8.7) strains in two regions and from NADC34-like (L1.5) strains in one region. These findings highlight the continuous genetic evolution and complex epidemiology of PRRSV, underscoring the critical need for sustained surveillance and detailed characterization of circulating strains to inform effective control and vaccine development strategies.