Early and Solid Protection Afforded by the Thiverval Vaccine Provides Novel Vaccination Alternatives Against Classical Swine Fever Virus

Figures

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  Figure 1. Detection of CSFV RNA load in samples and tissues during 21 days after vaccination. CSFV RNA load was detected by RT-qPCR and is expressed as Ct values. (-) symbol indicates samples in which fluorescence was not detected. Grey area indicates that the tissues were not collected at that time, in accordance with the experimental design described in the Materials and Methods section.

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  Figure 2. Clinical signs monitored after challenge. The individual clinical signs were recorded after CSFV “Margarita” strain infection. Animals 2 to 7 (group A) and 14 to 18 (group C) were challenged after 21 and 5 dpv, respectively. Animals 8 to 11 (group B), contacts for group A and 19 to 23 (group D), infection control group, were not vaccinated but challenged. Pigs were monitored daily for clinical signs during the 13 dpc or until euthanasia. Different shades of colour and the numerical clinical score represent the severity of the clinical signs as shown in the legend. Super-indexed letters in the mean clinical score value from each group are employed to represent statistically significant differences between the groups on that day; similar letters indicate no statistical difference, and different letters show statistical difference (p < 0.05).

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  Figure 3. IFN-α levels in sera after vaccination during 21 days. The IFN-α levels were determined at different time points after vaccination with a single dose of the Thiverval-strain vaccine. Asterisk symbol (*) refers to 4 dpv for groups A and B, and 5 dpv for groups C and D. Letters above the symbols are used to represent statistically significant differences between the groups on that day: similar letters indicate no statistical difference and different letters show statistical difference (p < 0.05).

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  Figure 4. Kinetic of E2 and Erns antibody response generated after vaccination and challenge for groups A and B. (a) Antibody response against the E2 glycoprotein was detected and is represented as blocking percentage. (b) Antibody response against Erns was detected by ELISA and reported as the S/P value in accordance with the formula previously described. Statistically significant differences between the groups A and B in the antibody response against E2 (a) and Erns (b) glycoproteins are represented by the asterisk symbol: (*) indicates p < 0.05.

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  Figure 5. Determination of the neutralising antibody response during the trial. The neutralising antibody titres after vaccination and challenge were evaluated by NPLA. Neg: The sample was negative for NPLA test; † symbol indicates that the animal was euthanized before this time point; asterisk symbol (*) indicates 21 dpv for groups A and B, and 5 dpv for groups C and D. Symbol (#) indicates animals that were euthanized at the day of challenge, according to the experimental design, see Materials and methods section.

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  Figure 6. CSFV RNA detection at different time points after challenge in samples and tissues. The samples were analyzed by RT-qPCR for (a,c) the CSFV [24] and (b,d) Margarita strain RNA [20] viral load at different time points during the 13 dpc (or until euthanasia). White area indicates negative samples. Euthanized animals are represented in grey square with hatches. Asterisk symbol (*) indicates statistically significant differences of the Ct values between the groups (p < 0.05).

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  Figure 7. Kinetic of E2 and Erns antibody response in pigs challenged at 5 dpv and controls (groups C and D). (a) Antibody response against the E2 glycoprotein was detected by ELISA and is represented as blocking percentage. (b) Antibody response against Erns was detected by ELISA and reported as the S/P value in accordance with the formula previously described. Statistically significant differences between the groups C and D in the antibody response against the E2 (a) and Erns (b) glycoproteins are represented by the asterisk symbol (*), indicating p < 0.05.

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  Figure 8. IFN-α levels in sera after challenge during 13 dpc. IFN-α levels were determined at different time points after challenge with CSFV “Margarita” strain. Asterisk symbol (*) refers to 21 dpv for group A and 5 dpv for group C. Letters above the symbols are used to represent statistically significant differences between the groups on that day: similar letters indicate no statistical difference, and different letters show statistical difference (p < 0.05).