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Background <p>Porcine reproductive and respiratory syndrome (PRRS) remains a major concern for the swine industry worldwide due to its significant economic impact and its association with respiratory co-infections. Vaccination is a key strategy for PRRS control; however, the most effective commercial anti-PRRSV vaccines to date—live attenuated vaccines, also named modified live virus (MLV) vaccines—provide only partial protection. This study investigates whether oral supplementation with formulated <i>Ulva</i>-derived seaweed extracts can enhance immune responses to PRRSV-1 MLV vaccination.</p> Methods <p>Two supplementation protocols using commercial seaweed extracts formulated with vitamin A and D (Searup®) were tested: one starting one day post-vaccination for five consecutive days (post-vaccination), and another beginning one day before vaccination and continuing for two days post-vaccination (pre-vaccination).</p> <p>In this exploratory farm-based experimental setting, pigs were divided into six groups: three vaccinated groups (supplemented with seaweed either pre- or post-vaccination or not supplemented), and three non-vaccinated control groups receiving the same supplementation regimes. Serum cytokine levels, PRRSV viral loads, and anti-PRRSV antibody responses were measured to assess immune modulation.</p> Results <p>Post-vaccination supplementation had no significant effect on vaccine viral load or humoral response, though a modest reduction in viral persistence was noted at 12&#xa0;days post-vaccination (dpv). In contrast, pre-vaccination supplementation significantly increased vaccine virus levels at 4 dpv (<i>p =</i> 0.048) and enhanced anti-PRRSV IgG levels (<i>p =</i> 0.029). This protocol also induced an early and sustained decrease in pro-inflammatory cytokines, suggesting an immunomodulatory effect of algal extract supplemented with Vitamins A and D.</p> <p>We present here for the first time, in field conditions and in the target species, significant immune modifications upon realistic oral supplementation with Searup®. These findings are consistent with previous studies demonstrating the potential of pre-vaccination seaweed supplementation as a cost-effective, practical strategy to enhance humoral responses to PRRSV vaccination. Further studies are needed to evaluate its impact on neutralizing antibody production, cellular responses and protection against heterologous field PRRSV strains.</p>

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Algae extract supplementation boosts humoral immunity induced by attenuated PRRSV-1 vaccination

  • 期刊论文

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  • 发表日期：

    2025年11月7日

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  • Caroline Hervet,
  • Frédérick Bussy,
  • Anne Morvan,
  • Francisco da Rocha Pinto,
  • Catherine Belloc,
  • Olivier Bourry,
  • Pauline Maisonnasse,
  • Pi Nyvall,
  • Nicolas Bertho

摘要

Background

Porcine reproductive and respiratory syndrome (PRRS) remains a major concern for the swine industry worldwide due to its significant economic impact and its association with respiratory co-infections. Vaccination is a key strategy for PRRS control; however, the most effective commercial anti-PRRSV vaccines to date—live attenuated vaccines, also named modified live virus (MLV) vaccines—provide only partial protection. This study investigates whether oral supplementation with formulated Ulva-derived seaweed extracts can enhance immune responses to PRRSV-1 MLV vaccination.

Methods

Two supplementation protocols using commercial seaweed extracts formulated with vitamin A and D (Searup®) were tested: one starting one day post-vaccination for five consecutive days (post-vaccination), and another beginning one day before vaccination and continuing for two days post-vaccination (pre-vaccination).

In this exploratory farm-based experimental setting, pigs were divided into six groups: three vaccinated groups (supplemented with seaweed either pre- or post-vaccination or not supplemented), and three non-vaccinated control groups receiving the same supplementation regimes. Serum cytokine levels, PRRSV viral loads, and anti-PRRSV antibody responses were measured to assess immune modulation.

Results

Post-vaccination supplementation had no significant effect on vaccine viral load or humoral response, though a modest reduction in viral persistence was noted at 12 days post-vaccination (dpv). In contrast, pre-vaccination supplementation significantly increased vaccine virus levels at 4 dpv (p = 0.048) and enhanced anti-PRRSV IgG levels (p = 0.029). This protocol also induced an early and sustained decrease in pro-inflammatory cytokines, suggesting an immunomodulatory effect of algal extract supplemented with Vitamins A and D.

We present here for the first time, in field conditions and in the target species, significant immune modifications upon realistic oral supplementation with Searup®. These findings are consistent with previous studies demonstrating the potential of pre-vaccination seaweed supplementation as a cost-effective, practical strategy to enhance humoral responses to PRRSV vaccination. Further studies are needed to evaluate its impact on neutralizing antibody production, cellular responses and protection against heterologous field PRRSV strains.