# Isolation and Biological Characteristics Study of Porcine Reproductive and Respiratory Syndrome Virus GZ2022 Strain

## TL;DR

Researchers isolated and studied a new PRRSV strain, GZ2022, from a Chinese swine farm, finding it moderately virulent and a recombinant of NADC30 and HuN4 strains.

## Contribution

Identification of a novel recombinant PRRSV strain with moderate virulence and partial immune evasion properties.

## Key findings

- GZ2022 is a recombinant strain with NADC30 as the major parent and HuN4 as a minor contributor.
- GZ2022 exhibits moderate virulence with typical PRRS symptoms but less severe than highly pathogenic strains.
- The strain shows a 131-amino-acid deletion in NSP2 and induces seroconversion by 14 days post-infection.

## Abstract

Porcine reproductive and respiratory syndrome (PRRS) is a significant infectious disease threatening swine production. In China, emerging NADC30-like PRRSV strains exhibit concerning features including frequent recombination events and partial immune evasion capabilities. In this study, we isolated and characterized a novel recombinant NADC30-like PRRSV strain, designated GZ2022, from a swine farm in Guizhou Province. The biological and pathogenic properties of this strain were systematically evaluated. Phylogenetic and recombination analyses revealed that GZ2022 is a recombinant virus, with NADC30 serving as the major parental strain and HuN4 as the minor contributor. In vivo experiments demonstrated that GZ2022 exhibits moderate virulence, inducing typical PRRS clinical signs in piglets, but causes less severe symptoms than highly pathogenic strains. These findings provide important insights into the molecular epidemiology and pathogenicity of PRRSV in China.

PRRSV continues to evolve, complicating its epidemiological landscape in China. In this study, we isolated a novel PRRSV strain, GZ2022, from a swine farm in Guizhou Province. Subsequent analyses performed on this isolate included complete genome sequencing, phylogenetic analysis, recombination assessment, and characterization of its biological properties. Phylogenetic analysis revealed that GZ2022 clusters within Lineage 1 (NADC30-like) and features a 131-amino-acid deletion in NSP2, consistent with NADC30-derived strains. Recombination analysis identified NADC30 as the major parental strain (75% genomic contribution), with a minor recombinant region (25%) derived from the highly pathogenic HuN4 strain. In vitro growth kinetics revealed peak viral titers in Marc-145 cells at 72 h post infection (hpi). Pathogenicity was evaluated in 21-day-old piglets infected with GZ2022, the highly pathogenic PRRSV strain WUH3, or negative controls. Both infected groups exhibited typical PRRS clinical signs (fever, respiratory distress) and histopathological lesions (interstitial pneumonia, pulmonary consolidation). However, GZ2022-infected piglets exhibited attenuated virulence compared to WUH3, with reduced pulmonary hemorrhage and 0% mortality compared to 80% in the WUH3 group. Seroconversion (N-protein antibodies) was observed at 14 dpi (days post inoculation) in GZ2022-infected animals, persisting throughout the 28-day trial. Viral shedding dynamics aligned with moderate pathogenicity. These findings classify GZ2022 as a moderately virulent NADC30-like recombinant strain with partial HuN4-derived genomic regions. The emergence of such strains underscores the need for sustained surveillance of PRRSV genetic diversity and systematic evaluation of the biological properties of novel variants to refine control measures and inform vaccine development.