A Non-Hemadsorbing Live-Attenuated Virus Vaccine Candidate Protects Pigs against the Contemporary Pandemic Genotype II African Swine Fever Virus

Viruses. 2024 Aug 19;16(8):1326. doi: 10.3390/v16081326.

Abstract

African swine fever (ASF) is a highly contagious and severe hemorrhagic transboundary swine viral disease with up to a 100% mortality rate, which leads to a tremendous socio-economic loss worldwide. The lack of safe and efficacious ASF vaccines is the greatest challenge in the prevention and control of ASF. In this study, we generated a safe and effective live-attenuated virus (LAV) vaccine candidate VNUA-ASFV-LAVL3 by serially passaging a virulent genotype II strain (VNUA-ASFV-L2) in an immortalized porcine alveolar macrophage cell line (3D4/21, 50 passages). VNUA-ASFV-LAVL3 lost its hemadsorption ability but maintained comparable growth kinetics in 3D4/21 cells to that of the parental strain. Notably, it exhibited significant attenuation of virulence in pigs across different doses (103, 104, and 105 TCID50). All vaccinated pigs remained healthy with no clinical signs of African swine fever virus (ASFV) infection throughout the 28-day observation period of immunization. VNUA-ASFV-LAVL3 was efficiently cleared from the blood at 14-17 days post-infection, even at the highest dose (105 TCID50). Importantly, the attenuation observed in vivo did not compromise the ability of VNUA-ASFV-LAVL3 to induce protective immunity. Vaccination with VNUA-ASFV-LAVL3 elicited robust humoral and cellular immune responses in pigs, achieving 100% protection against a lethal wild-type ASFV (genotype II) challenge at all tested doses (103, 104, and 105 TCID50). Furthermore, a single vaccination (104 TCID50) provided protection for up to 2 months. These findings suggest that VNUA-ASFV-LAVL3 can be utilized as a promising safe and efficacious LAV candidate against the contemporary pandemic genotype II ASFV.

Keywords: African swine fever; efficacious; genotype II; live-attenuated virus; protection; safe.

MeSH terms

  • African Swine Fever Virus* / genetics
  • African Swine Fever Virus* / immunology
  • African Swine Fever* / immunology
  • African Swine Fever* / prevention & control
  • African Swine Fever* / virology
  • Animals
  • Antibodies, Viral / blood
  • Antibodies, Viral / immunology
  • Cell Line
  • Genotype*
  • Swine
  • Vaccination / veterinary
  • Vaccines, Attenuated* / administration & dosage
  • Vaccines, Attenuated* / genetics
  • Vaccines, Attenuated* / immunology
  • Viral Vaccines* / administration & dosage
  • Viral Vaccines* / genetics
  • Viral Vaccines* / immunology
  • Virulence

Substances

  • Vaccines, Attenuated
  • Viral Vaccines
  • Antibodies, Viral

Grants and funding

This research is supported by the Vietnam Ministry of Science and Technology (grant number: ĐT.02/DAKH-02/19-HĐ-ĐTĐL.CN-CNN); the National Bio and Agro-Defense Facility Transition Fund, the USDA National Institute of Food and Agriculture, Hatch-Multistate project (grant number: 1021491); the USDA ARS Non-Assistance Cooperative Agreements (grant numbers: 58-8064-8-011, 58-8064-9-007, 58-3020-9-020, and 59-0208-9-222); the USDA NIFA Award #2022-67015-36516; the USDA NIFA Subaward #25-6226-0633-002; the National Pork Board Grant (grant number: 18-059); and the Department of Homeland Security (grant number: 70RSAT19CB0000027).