Assessment of a Live Attenuated African Swine Fever Vaccine Produced in a Stable Cell Line: Immunogenicity and Protective Potential in Wild Boar

Introduction
African Swine Fever (ASF) is a severe, highly contagious hemorrhagic disease affecting both domestic pigs and wild boar, causing major losses to animal health and the global swine industry. Since its spread across Europe (2007), Asia (2018), and the Americas (2021), the need for effective control measures has become critical. Although live attenuated vaccines have shown potential, their production depends on primary cell cultures, which limits scalability and standardization.

Methods
This study evaluated the in vivo efficacy and safety of the attenuated ASFV strain Lv17/WB/Rie1-ΔCD after its adaptation to the stable MA104 cell line. Eighteen wild boar piglets were orally vaccinated on days 0 and 21 and challenged on day 37 with the virulent Armenia 2007 strain. Clinical signs, rectal temperature, immune response, and viremia levels were monitored over a 62-day period.

Results
Oral vaccination with the adapted strain led to partial clinical protection. Vaccinated wild boar exhibited a delay in the viremia onset and a reduction in the severity of fever compared to controls. Clinical scores were lower in the vaccinated group. Additionally, viremia levels post-challenge were significantly reduced in vaccinated animals, and viral genome detection was delayed, suggesting a containment effect. However, the proportion of protected animals (i.e., surviving without severe clinical signs) was lower than that reported in previous studies using the same vaccine propagated in primary cells. Seroconversion was inconsistent, and overall antibody titters were lower, indicating a weaker humoral response. These findings point toward a potential loss of immunogenicity following adaptation to the stable cell line.

Conclusions
Adapting ASFV to a stable cell line marks progress toward scalable vaccine production. Nevertheless, these results underscore the need to optimize adaptation protocols to maintain vaccine efficacy and immunogenicity. Further refinement will be essential to achieve protection levels comparable to vaccines derived from primary cell cultures.