Periodic Reporting for period 1 - ASFaVIP (UNDERSTANDING PERFORMANCE CHARACTERISTICS OF LIVE ATTENUATED VACCINES FOR THE PREVENTION AND CONTROL OF AFRICAN SWINE FEVER IN WILD BOAR AND DOMESTIC PIGS)
Reporting period: 2024-01-01 to 2025-06-30
African Swine Fever (ASF) devastates pig populations, threatens biodiversity, and cripples rural economies. Detection triggers trade bans and costly control, yet no global vaccine exists, hindering eradication.
Past vaccine efforts, using inactivated viruses or subunit proteins, are safe but ineffective against lethal challenges. Live attenuated vaccines offer stronger protection but pose safety risks. Recent advances involve deleting virulence genes to create safer, highly protective vaccine candidates. One promising candidate, ASFV-G-ΔI177L, derived from the Georgia 2007 strain, shows encouraging safety and efficacy in trials and is progressing toward European approval. If successful, it could enable vaccination of domestic pigs and wild boar.
The ASFaVIP project unites ecologists, virologists, immunologists, industry, and regulators across Europe and North America. It aims to develop licensed vaccines and field deployment strategies, especially in wildlife.
The project is structured into four themes: 1) standardizing trial protocols and identifying protective immune responses; 2) developing next-generation, genetically engineered vaccines and DIVA diagnostic tests; 3) conducting safety and efficacy studies, including oral vaccines for wild boar and pregnant sows; 4) translating lab results into field strategies, i.e. designing resilient bait vaccines, monitoring biomarkers, and optimizing vaccination schedules with advanced epidemiological models.
Past vaccine efforts, using inactivated viruses or subunit proteins, are safe but ineffective against lethal challenges. Live attenuated vaccines offer stronger protection but pose safety risks. Recent advances involve deleting virulence genes to create safer, highly protective vaccine candidates. One promising candidate, ASFV-G-ΔI177L, derived from the Georgia 2007 strain, shows encouraging safety and efficacy in trials and is progressing toward European approval. If successful, it could enable vaccination of domestic pigs and wild boar.
The ASFaVIP project unites ecologists, virologists, immunologists, industry, and regulators across Europe and North America. It aims to develop licensed vaccines and field deployment strategies, especially in wildlife.
The project is structured into four themes: 1) standardizing trial protocols and identifying protective immune responses; 2) developing next-generation, genetically engineered vaccines and DIVA diagnostic tests; 3) conducting safety and efficacy studies, including oral vaccines for wild boar and pregnant sows; 4) translating lab results into field strategies, i.e. designing resilient bait vaccines, monitoring biomarkers, and optimizing vaccination schedules with advanced epidemiological models.
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.
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.
The proven efficacy and safety of ASFV-G-ΔI177L significantly impact multiple fields by providing a transformative tool for ASF control in both farmed and wild pigs, benefiting animal welfare, biodiversity, and industry stability. This advances veterinary and wildlife health while supporting standardized vaccine production for large-scale European deployment. Progress in biosecurity, surveillance, non-invasive wild boar monitoring, bait design, and bioinformatic modeling enhances practical deployment and risk assessment. Identifying immune correlates and optimal dosing informs rational vaccine development and improvements. Ongoing trials will optimize oral immunization, schedules, and bait strategies tailored to regional ecologies. Research into immune mechanisms and DIVA diagnostics will bolster efficacy claims and accelerate regulatory approval, while standardizing testing methods ensures reliable, comparable results across regions.