Journal Article

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

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

2025

Overview

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.

• Publisher: BioMed Central,BioMed Central Ltd,BMC
• Subject: Algae / Algae extract / Animal Feed - analysis / Animals / Antibodies, Viral - blood / antibody formation / Attenuated vaccines / B cells / Betaarterivirus suid 1 / blood serum / cost effectiveness / cytokines / Cytokines - blood / Dietary Supplements / economic impact / Health aspects / humoral immunity / Immune response / Immunity, Humoral - drug effects / Immunoglobulin G / immunomodulation / immunomodulators / Infection / Life Sciences / macroalgae / Medicine / Medicine & Public Health / Oral supplementation / Plant Extracts - administration & dosage / Plant Extracts - pharmacology / Porcine / Porcine reproductive and respiratory syndrome / Porcine Reproductive and Respiratory Syndrome - immunology / Porcine Reproductive and Respiratory Syndrome - prevention & control / Porcine respiratory and reproductive syndrome virus - immunology / Pork industry / Prevention / PRRSV / Seaweed - chemistry / species / Swine / Testing / Transgenics / Vaccination / Vaccination - veterinary / Vaccine / vaccines / Vaccines, Attenuated - immunology / Veterinary Medicine/Veterinary Science / Viral Load / Viral Vaccines - administration & dosage / Viral Vaccines - immunology / viruses / Vitamin A / Zoology