2016 ACVIM Forum Research Abstract Program

Overall, all horses responded to vaccination with a significant increase (P < 0.05) in HI titers following initial vaccination compared to saline controls. Significant increases (P < 0.001) in IgGa and IgGb, but not IgGt EIV specific antibody responses to vaccination were also observed. EMS did not significantly affect (P > 0.05) humoral immune responses as measured by HI titers or IgG isotypes to influenza vaccination, however more work is needed to explore possible differences in CMI responses. It is possible that obesity as compared to insulin resistance plays a larger role in modulating the immune process considering that while EMS horses were insulin resistant and had significantly greater regional obesity (cresty neck score) compared to non-EMS controls, they had moderate general obesity (body condition score), which may have not been sufficient to impact immune response to vaccination. Pituitary pars intermedia dysfunction (PPID) is an endocrinopathy affecting 15-30% of the aged equid population. PPID is characterized by various clinical manifestations, the hallmark of which is hypertrichosis. Additionally, PPID horses exhibit immunosuppression, making them more susceptible to opportunistic infections. Our lab has established that aged horses exhibit both immunosenescence and inflamm-aging, the low-grade chronic inflammation occurring systemically with aging. To determine whether these age-related changes in cell-mediated immune responses may be affected by the presence of PPID, peripheral blood mononuclear cell (PBMC) proliferation and cytokine production were compared in age-matched PPID and non-PPID horses. PPID status was determined using thyrotropin releasing hormone (TRH) stimulation testing.