Viral dynamics and immune responses to foot-and-mouth disease virus in African buffalo (Syncerus caffer)

Figures

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  Figure 1. Body temperature in FMDV infected African buffalo. Body temperature, measured by temperature-sensitive data loggers, of each individual after needle or in-contact infection with FMDV SAT1 (column 1), SAT2 (column 2) or SAT3 (final column). One animal was eliminated from analysis for SAT 1 in-contact infected due to repeated high readings (animal 2). Panel (A) represents the raw temperatures over time. The dotted lines represent the normal temperatures as determined by the calculated reference range. Panel (B) represents the residuals from the fitted line, with a value above the dotted line considered a fever if the residuals stay above the line for 6 consecutive hours (72 readings). Body temperature fluctuates during the day and all NI and in-contact buffalo show high temperature within 1–2 days after virus infection (NI) and approximately 5 days after virus exposure (in-contact) and remained elevated for around 3–4 days. SAT2 NI had an earlier initial elevated temperature and compared to SAT1 NI and SAT3 NI (p = 0.02) and SAT3 in-contact showed a delay in fever (p = 0.006) compared to the SAT2 and SAT3 in-contact. All buffalo from the SAT1 NI and 1 animal from SAT2 and SAT3…

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  Figure 2. FMDV genome copy number dynamics in African buffalo. Detection of FMDV genome copy numbers (GCN) by RT-qPCR in serum (A), tonsil swab (solid lines) and probang (dashed lines) (B) and nasal swab (C) from animals needle infected with SAT1, SAT2 and SAT3 FMDV serotypes (blue lines, round symbol) versus in-contact (pink, square symbol). NI animals were needle infected on day 0 of the study, and in-contact animals were mixed with NI groups on day 2. Graphs represent the mean and SEM for each group at each time point.

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  Figure 3. Specific humoral immune response induced by FMDV infection. Neutralizing antibody titers in log10 (A) and presence of antibody levels against FMDV non-structural proteins (NSP) (B), induced by SAT1, SAT2 and SAT3 FMDV infected animals by needle infection (blue lines, round symbol) or by contact challenge (pink, square symbol). NSP results are expressed by percentage of inhibition (PI) and cut-off is determined at 50% (dash line). Graphs represent the mean and SEM for each group at each time point.

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  Figure 4. Innate immune response and acute phase proteins induced by FMDV in African buffalo. Concentrations of SAA (A), hatoglobin (B), type I/III IFN (C) and IFNɣ (D) in serum from animals infected with SAT1, SAT2 or SAT3 FMDV serotypes by NI (blue lines, round symbol) or contact challenge (pink lines, square symbol). Graphs represent the mean and SEM for each group at each time point. Cut-offs for SAA and hatoglobin were established at 546 and 802 ng/µL and cut off for type I IFN and IFNɣ was established at 0.76 iu/mL and 1.04 ng/mL, respectively.