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<p>Emerging viral pathogens such as porcine reproductive and respiratory syndrome virus (PRRSV) remain a major threat to the swine industry, causing severe economic losses due to limited protection from current vaccines. In this study, the MARC-145 cell line was utilized as an in vitro infection model to screen lactic acid bacteria (LAB) strains with antiviral potential against PRRSV. Forty-five LAB isolates were obtained from fecal samples of nursing piglets, and after removing cytotoxic strains, the antiviral properties of the remaining 25 isolates were assessed. Among the tested strains, the intracellular fraction of HH69 provided the strongest prophylactic effect, whereas HH09 displayed the highest direct-inhibitory effect. Both HH09 and HH32-1 produced notable therapeutic effects. In the prophylactic assay, HH69 significantly suppressed PRRSV-M transcription and reduced the expression of proinflammatory cytokines, including interleukin (IL)-8 and tumor necrosis factor-α (TNF-α), as well as anti-inflammatory cytokines, including IL-10 and transforming growth factor-β1 (TGF-β1), while enhancing interferon-stimulated gene 15 (ISG15) expression in MARC-145 cells. In the direct-inhibitory assay, HH09 significantly reduced PRRSV-M and decreased IL-6, IL-8, TGF-β1, and TNF-α. In the therapeutic assay, HH09 significantly reduced PRRSV-M and decreased IL-6, IL-8, IL-10, and TGF-β1, whereas HH32-1 decreased PRRSV-M, IL-8, TGF-β1, and TNF-α while elevating the antiviral enzyme 2’-5’-oligoadenylate synthetase 1 (OAS1). Microscopic observations, biochemical characteristics, and phylogenetic analyses identified HH09 as <i>Limosilactobacillus reuteri</i>, HH32-1 as <i>Enterococcus faecium</i>, and HH69 as <i>Enterococcus faecalis</i>. These findings indicate that HH09, HH32-1, and HH69 may serve as antiviral agents against PRRSV by modulating cytokine and ISG responses.</p>

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In vitro evaluation of Limosilactobacillus and Enterococcus isolates for inhibitory activity against porcine reproductive and respiratory syndrome virus

  • 期刊论文

  • 发表日期：

    2026年3月21日

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  • Chin-Che Chang,
  • Hui-Wen Chang,
  • Je-Ruei Liu

摘要

Emerging viral pathogens such as porcine reproductive and respiratory syndrome virus (PRRSV) remain a major threat to the swine industry, causing severe economic losses due to limited protection from current vaccines. In this study, the MARC-145 cell line was utilized as an in vitro infection model to screen lactic acid bacteria (LAB) strains with antiviral potential against PRRSV. Forty-five LAB isolates were obtained from fecal samples of nursing piglets, and after removing cytotoxic strains, the antiviral properties of the remaining 25 isolates were assessed. Among the tested strains, the intracellular fraction of HH69 provided the strongest prophylactic effect, whereas HH09 displayed the highest direct-inhibitory effect. Both HH09 and HH32-1 produced notable therapeutic effects. In the prophylactic assay, HH69 significantly suppressed PRRSV-M transcription and reduced the expression of proinflammatory cytokines, including interleukin (IL)-8 and tumor necrosis factor-α (TNF-α), as well as anti-inflammatory cytokines, including IL-10 and transforming growth factor-β1 (TGF-β1), while enhancing interferon-stimulated gene 15 (ISG15) expression in MARC-145 cells. In the direct-inhibitory assay, HH09 significantly reduced PRRSV-M and decreased IL-6, IL-8, TGF-β1, and TNF-α. In the therapeutic assay, HH09 significantly reduced PRRSV-M and decreased IL-6, IL-8, IL-10, and TGF-β1, whereas HH32-1 decreased PRRSV-M, IL-8, TGF-β1, and TNF-α while elevating the antiviral enzyme 2’-5’-oligoadenylate synthetase 1 (OAS1). Microscopic observations, biochemical characteristics, and phylogenetic analyses identified HH09 as Limosilactobacillus reuteri, HH32-1 as Enterococcus faecium, and HH69 as Enterococcus faecalis. These findings indicate that HH09, HH32-1, and HH69 may serve as antiviral agents against PRRSV by modulating cytokine and ISG responses.