During the initial reporting period, the consortium achieved several key results.
Three LAV candidates, namely ASFV-G-ΔI177L, ASFV-G-ΔMGF, and ASFV-G-Δ9GL/ΔUK, were tested in harmonized multicenter trials. ASFV-G-ΔI177L showed the highest protective efficacy, with survival linked to early antibody responses (ELISA/IPT) by 28 days post-vaccination. Sentinel pigs showed no shedding, indicating safety, and survivors had lower viral loads, with only ASFV-G-ΔI177L correlating with pre-challenge viral genomes. Elevated IFN‑α at 7 days post-vaccination predicted better outcomes, while early activation of immune pathways was associated with protection. Higher IL‑8 related to worse clinical scores; SPF pigs exhibited lower baseline inflammation. T-cell analyses identified protective IFN‑γ-producing cells, and survivors generally had pre-challenge antibodies, though one protected pig was antibody-negative, suggesting cellular immunity can also confer protection.
ASFV-G-ΔI177L was successfully propagated on a stable porcine cell line, with standardized SOPs for production. Safety testing in breeding boars revealed adverse effects: clinical signs, reduced semen quality, and presence of the vaccine virus in semen. High viremia and vaccine dissemination correlated with organ infection severity.
Oral vaccination showed low efficacy (~20%) when directly administered. Increasing doses improved responses, and Montanide Gel 01 PR and walnut shreds enhanced immunogenicity, though walnuts were unsuitable as bait. Montanide Gel remains the preferred adjuvant for bait formulations. HIMB and Montanide GR were ineffective.
A heat- and humidity-resistant bait formulation (corn flour, piglet feed, honey, sucrose) was developed, featuring color and aroma to minimize non-target uptake. Field trials showed wild boars consumed 94% of bait, with smaller groups and multiple heaps improving equitable access. Biomarkers and sampling tools (colored feces, rope swabs, environmental DNA) are under development to monitor bait uptake and vaccination coverage in wild populations.
