IL-6 production following vaccination in pigs--an additional immune response parameter for assessing FMD vaccine efficacy?

Foot-and-mouth disease vaccine potency testing involving live virus challenge can be problematical in pigs. Alternative methods of assessing vaccine efficacy are therefore desirable. Here we investigate the link between IL-6 in blood at time of challenge and protection against challenge by carrying out statistical analyses utilising data from six separate potency tests performed in swine with the aim of assessing whether IL-6 could be exploited as an additional parameter for confirming vaccine efficacy in pigs. These analyses confirmed that systemic IL-6 levels increased when the administered vaccine dose increased and that the odds of protection against challenge increased as IL-6 levels increased. The link between increased protection and increased antibody was reaffirmed and a significant link between IL-6 levels and antibody levels was shown. We therefore conclude that quantifying the levels of IL-6 in serum could provide additional means of qualifying whether a vaccine will afford clinical protection or not in pigs, in the absence of an actual challenge, and thus offer the possibility of improved vaccine potency testing in pigs both in terms of animal welfare as well as cost.