A Chimeric PRRSV Vaccine with Dual Nsp2 Deletions Elicits Cross-Lineage Protection Against Heterologous Challenge.

Chimeric rFX1701 vaccine provides cross-lineage PRRSV protection superior to current commercial vaccines.

This study describes the development and evaluation of rFX1701, a chimeric PRRSV vaccine engineered with dual Nsp2 deletions to provide cross-lineage protection. The vaccine was constructed using a lineage 8.7 backbone with an additional 131-amino acid deletion characteristic of lineage 1.8 strains. In vitro studies demonstrated efficient viral replication with an attenuated phenotype. Vaccinated piglets developed low-level transient viremia without clinical signs. The vaccine induced robust antibody responses with cross-neutralizing activity against both lineages and a balanced Th1/Th2 cytokine response. Following heterologous challenge with lineage 1.8 virus, rFX1701-vaccinated pigs remained clinically healthy with minimal lung pathology and effectively cleared challenge virus, whereas a commercial HP-PRRSV-based MLV vaccine provided no protection. These results suggest that incorporating lineage-specific deletions into a chimeric vaccine platform may effectively broaden cross-lineage immunity against PRRSV.

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