African Swine Fever Vaccine Candidate ASFV-G-ΔI177L/ΔLVR Protects Against Homologous Virulent Challenge and Exhibits Long-Term Maintenance of Antibodies

Figures

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  Figure 1. Rectal temperature and survival of the pigs following vaccination and challenge. The dotted line indicates the threshold for fever at 40.0 °C. The black line represents the challenge at 28 dpv; the red and blue lines indicate the challenge infection and negative control, respectively.

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  Figure 2. Group A: the submandibular lymph node from a pig vaccinated with ASFV-G-ΔI177L/ΔLVR before challenging. Macroscopic lesions (V1 to V4): all submandibular lymph nodes were normal. Microscopic lesions (V1-1 to V4-1): Sections of the submandibular lymph node. H&E stain, 100x Normal histopathological findings were confirmed in all pigs challenged after vaccination. Group A-1: submandibular lymph node from a pig challenged with the highly virulent ASFV isolate (Hwacheon/2020). Macroscopic lesions (C1 to C4): lymph nodes were swollen and edematous, with severe hemorrhages in both the cortex and medulla. Microscopic lesions (C1-1 to C4-1): Sections of the submandibular lymph node. H&E stain, 100x. Scale bar = 100 µm. Severely lymphocytic depletion affects both lymphoid follicle and is accompanied by severe hemorrhages in the medullary cords, blood infiltration of the marginal zones, and congestion of numerous vessels.

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  Figure 3. Group A: the spleen from a pig vaccinated with ASFV-G-ΔI177L/ΔLVR before viral challenge. Macroscopic lesions (V1 to V4): all spleens were normal in size and red in color. Microscopic lesions (V1-1 to V4-1): Sections of the spleen. H&E stain, 100x Normal histopathological findings were confirmed in all pigs challenged after vaccination. Group A-1: the spleen from a pig challenged with strain Hwacheon/2020. Macroscopic lesions (C1 to C4): the spleen shows an increase in size with round edges, along with friable (C1) and dark red to black color (C1 to C4). Microscopic lesions: Sections of the spleen (C1-1 to C4-1). H&E stain, 100x. Scale bar = 100 µm. Diffuse infiltration of the pulp by erythrocytes and macrophages showing severe lymphocytic depletion along with abundant pyknotic cells.

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  Figure 4. Rectal temperatures and survival of the pigs following vaccination. The dotted line indicates the threshold for fever at 40.0 °C. The black line represents monitoring up to 56 days after the first vaccination: The blue line indicates negative control.

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  Figure 5. Group B: the submandibular lymph node from a pig vaccinated with ASFV-G-ΔI177L/ΔLVR. Macroscopic lesions (V1 to V4): the submandibular lymph node of long-term-vaccinated pigs was normal. Group B-1: the submandibular lymph node from a non-vaccinated pig (negative control). Macroscopic lesions (C1 to C2): all submandibular lymph nodes were normal. Group B: the spleen from a pig vaccinated with ASFV-G-ΔI177L/ΔLVR. Macroscopic lesions (V1 to V4): the spleens of long-term-vaccinated pigs were normal, exhibiting a bright red color. Group B-1: the spleen from a non-vaccinated pig (negative control). Macroscopic lesions (C1 to C2): all spleens were normal.