Porcine reproductive and respiratory syndrome virus (PRRSV) infection in pigs is economically devastating for the global swine industry. The viral infection leads to reproductive disorder in sows and respiratory problems in infected newborn and growing pigs. Unfortunately, high genetic variability of the virus and differing disease-causing strength or virulence hinders vaccine development and complicates disease management. Not much is known of the factors contributing to viral disease severity or the anti-viral immune responses.

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Source: College of Veterinary Medicine, Jeonbuk National University

PRRSV infection in growing pigs is a significant drawback for the swine industry. The study findings reveal that differing virulence of PRRSV triggers distinct immune responses in the lungs of the infected animal. Improved understanding of immune mechanisms will aid in efficient disease management and development of vaccines and targeted therapeutics.

Dr. Jun-Mo Kim, Associate Professor at the Department of Animal Science and Technology, Chung-Ang University, Korea has focused his research efforts on filling this gap in understanding.

“Using a PRRSV infection model, our goal is to advance the comprehensive understanding of the infection and response mechanism in order to minimize industrial damage,” shared Dr. Kim. Recently, his group analyzed protein-coding RNA transcripts isolated from single cells and fluid collected from lungs of PRRSV-infected pigs. They monitored immune cell alterations triggered by PRRSV strains of varying virulence. This paper was made available online on January 28, 2025 and was published in Volume 16 Issue 1 of Nature Communications.

Protective macrophages

The study shows that high virulence PRRSV strain triggered early, severe lung damage and overall immune imbalance marked by significant reduction in macrophages. In contrast, PRRSV strain of intermediate strength led to delayed lung damage with fewer immune alterations. Importantly, higher numbers of protective anti-inflammatory M2-like macrophages (SPP1-CXCL14high) were observed in less virulent infections, suggesting a potential role in promoting lung healing.

While fewer than 5% of macrophages were directly infected by virus, cell death and immune responses were widespread indicating that extracellular vesicles or exosomes containing microRNAs released from the PRRSV-infected cells likely contributed to pathogenesis and cell death in non-infected bystander cells.

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“Our study findings will aid the development of innovative therapeutic strategies with the potential to mitigate severe lung damage and promote efficient recovery in PRRSV-infected animals, paving the way for effective viral disease management,” explains Dr. Kim, elaborating on the long-term implications of their findings. In addition to the obvious impact on livestock health, global food security, and in securing the economy of the swine industry, the findings from this study may find a parallel in other human respiratory viruses and therapeutic strategies are likely to be applicable and effective broadly.

With these insights, researchers are one step closer to turning scientific discovery into real-world solutions that safeguard both animal and human health.

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