While
fever and
inflammation are hallmark features of bovine
ephemeral fever (BEF), the
cytokine networks that underlie the acute phase of the disease have not been empirically defined in cattle. This study characterised the plasma kinetics of proinflammatory
cytokines (IL-1β, IL-6, TNF-α) and
IL-10 during acute BEF and elucidated on the relationship between the onset of the virus
neutralizing antibody response and resolution of viraemia in natural BEF virus (BEFV)
infections in cattle. Plasma from three BEFV-infected and three uninfected cattle was tested for the study
cytokines by a cELISA, viraemia monitored by qRT-PCR, and virus
neutralizing antibody titres determined using a standard protocol. Unlike the negative controls, plasma concentrations of IL-1β, TNF-α,
IL-6, and
IL-10 were consistently increased in the three virus-infected animals. Two of the infected heifers were recumbent and pyrexic on the first day of monitoring and increased
cytokine production was already in progress by the time viraemia was detected in all the three infected animals. In all the virus-infected heifers, IL-1β was the most strongly expressed
cytokine,
IL-6 and
IL-10 manifested intermediate plasma concentrations while TNF-α was the least expressed and demonstrated bi-phasic peaks three and five days after the onset of
pyrexia. In two of the BEFV-infected heifers, viraemia resolved on the day of seroconversion while in the other infected animal,
viral RNA was detectable up to three days after seroconversion. The present data document variable increase in plasma IL-1β,
IL-6, TNF-α, and
IL-10 during natural BEFV
infections and the fact that upregulation of all but TNF-α precedes seroconversion. In addition to virus neutralising
antibodies, it is likely that
cytokine-mediated cellular mechanisms may be required for resolution of viraemia in BEF. Considering the anti-inflammatory properties of
IL-10, its upregulation may potentially antagonise the
fever response in BEFV-infected cattle.