Host Responses to Live-Attenuated ASFV (HLJ/18-7GD)

Area of Science:

• Veterinary Immunology
• Virology
• Vaccinology

Background:

• African swine fever (ASF) is a devastating viral disease impacting swine populations globally.
• The novel vaccine candidate HLJ/18-7GD, lacking multigene families and the CD2v gene, has shown promise in preliminary safety and efficacy trials.
• Understanding the precise immune mechanisms of HLJ/18-7GD is crucial for its successful deployment.

Purpose of the Study:

• To investigate the immune-protective mechanisms of the African swine fever vaccine candidate HLJ/18-7GD.
• To analyze the humoral and cellular immune responses in pigs following immunization with HLJ/18-7GD.
• To compare the immune response induced by HLJ/18-7GD with that of the parent virus.

Main Methods:

• Pigs were immunized with a single dose of HLJ/18-7GD (10^6 TCID50).
• Humoral immunity was assessed by measuring specific antibody levels.
• Cellular immunity was evaluated by analyzing T lymphocyte subsets (Th, CTL, DP-T cells) and cytokine production (GM-CSF, IFN-γ, TNF-α) in peripheral blood mononuclear cells (PBMCs) after immunization and challenge with virulent virus.
• In vitro assays were performed to assess PBMC responses to the HLJ/18 strain.

Main Results:

• HLJ/18-7GD immunization induced high levels of specific antibodies in pigs.
• A transient increase in T lymphocyte subsets (Th, CTL, DP-T cells) was observed in PBMCs post-immunization.
• Following challenge with virulent HLJ/18, immunized pigs showed significantly elevated Th, CTL, and DP-T cell percentages.
• Upregulation of GM-CSF, IFN-γ, and TNF-α was noted at 7 days post-inoculation, contrasting with results from parent virus infection.
• PBMCs from immunized pigs promoted higher CD8+ T cell responses against the HLJ/18 strain in vitro.

Conclusions:

• The vaccine candidate HLJ/18-7GD elicits robust specific antibody and T lymphocyte responses.
• The observed immune responses, including cytokine production, contribute to the protective effects of HLJ/18-7GD.
• These findings provide a theoretical foundation for the use of HLJ/18-7GD as a safe and effective vaccine against African swine fever.