Head Start Immunity: Characterizing the Early Protection of C Strain Vaccine Against Subsequent Classical Swine Fever Virus Infection

Figures

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  Figure 1. C Strain Vaccination and Subsequent Challenge. (A) Schematic outline of the vaccine/challenge study highlighting the key time points of vaccination and challenge. Three animals per group were euthanized at day 5, 8, and 10 pv for sample acquisition (Blue arrows). (B) Mean clinical score data from both C strain vaccinated and mock inoculated animals from before the study commenced until completion. (C) Rectal temperatures of animals throughout the course of the study. (D) Peripheral blood leukocyte counts in EDTA blood samples throughout the study (E) CSFV RNA as detected in blood by reverse transcription-quantitative RT-PCR. Black arrows indicate time of challenge. Error bars indicate SD.

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  Figure 2. Overrepresented Gene Ontologies in tonsils 5 days after vaccination. (A) Gene ontologies overrepresented in the subset of genes upregulated in C strain vaccinated pigs at 5 days post vaccination. (B) Gene ontologies overrepresented in the subset of genes downregulated in C strain vaccinated pigs at 5 days post vaccination. Hypergeometric Test used to determine significance (p < 0.05). Level of significance indicated by yellow to orange coloring.

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  Figure 3. Differential expression of a cohort of genes as identified at each time point. (A) Expression of a cohort of 14 genes at day 5 post vaccination, comparing the C Strain vaccinated animals to those that received the mock inoculation. (B) Expression of a cohort of 14 genes at day 8 post vaccination (3 dpc) comparing the C Strain vaccinated animals to those that received the mock inoculation. (C) Expression of a cohort of 14 genes at day 10 post vaccination (5 dpc), comparing the C Strain vaccinated animals to those that received the mock inoculation. (D) Heat map showing the gene expression changes as they occurred over the course of the study. Expression values are from 3 pigs per condition per time point. Significance was determined using a moderated t-test p < 0.05 considered as significant.

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  Figure 4. Network analysis of Co-expressed Genes. Network assembled from a cohort of 14 genes significantly differentially regulated at each time point. Network based on interactions defined in the InnateDB. Nodes and label sizes are mapped based on betweenness centrality. Network assembled using Cytoscape 3.2.

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  Figure 5. Head Start Immunity Model. Upon vaccination with C strain, the induction of interferon results in induction of ISGs, including the ISG15 antiviral pathway resulting in the induction and activation via ISGylation of a wide variety of antiviral effectors. These antiviral effectors accumulate over the 5 days post vaccination, priming the host in an antiviral state and, for example via induction of RSAD2, instigating the adaptive immune response. If during this window a virulent strain of CSFV attempts to infect the host, the multitude of antiviral effectors are already present within the cell and can immediately prevent the replication of the virus and ultimately assist in preventing the establishment of infection. Without prior vaccination, replication of a virulent strain of CFSV is allowed as although the antiviral effectors of IFN and ISG15 pathways are induced by the virulent virus these cannot keep pace with the replication rate of virulent strains of CSFV and thus are not able to sufficiently control viral replication before adaptive responses can be activated, leading to the onset of clinical disease.