Increased interleukin-6 activity in the serum of ponies acutely infected with equine infectious anaemia virus

Seven ponies were infected with the virulent wild-type Wyoming strain of eq uine infectious anaemia Virus (EIAV). Infection status was monitored by ser um reverse transcriptase activity, rectal temperature, and complete blood c ount. Preinfection serum and serum obtained during the initial febrile epis ode following infection were assayed for interleukin 6 (IL-6) activity. Pos tinfection IL-6 activity was significantly increased as compared to preinfe ction values. The magnitude of increase in IL-6 was positively correlated w ith reverse transcriptase activity (an indirect measure of viraemia) but wa s not correlated with rectal temperature. IL-6 production in response to EI AV infection may play a role in pathogenesis of disease, especially the hyp erglobulinaemia and apparent polyclonal B cell activation in these horses.