PSX-A-8 - Late-Breaking: Development of multiplex assays for equine cytokines IL-1β, IL-4, IL-6, IL-8, IL-10, and TNFα

Equine-specific assays to quantify cytokine concentrations are limited and often have a restricted range such that physiological concentrations of many cytokines are below detectable limits of the assay. We aimed to develop custom multiplex assays for equine interleukin (IL)-1β, IL-4, IL-6, IL-8, IL-10, and tumor necrosis factor (TNF) α using the Meso Scale Discovery U-PLEX platform. Equine-specific ELISA kits containing unlabeled and biotinylated polyclonal antibodies and the specific recombinant equine cytokine were purchased for each cytokine. Each biotinylated antibody was coupled to a linker specific for a unique spot within each well of the U-PLEX plates. The unlabeled antibodies were conjugated with electrochemiluminescent labels to serve as detection antibodies. Each cytokine assay was optimized individually prior to optimization in multiplex. Two preliminary experiments were performed: 1) multiplexed conjugation of equine IL-10 and TNFα to the U-PLEX plates; and 2) multiplexed conjugation of equine IL-1β, IL-4, IL-6, and IL-8 to the U-PLEX plates. Standard curves were run at concentrations ranging from 0 to 5,000 pg/mL for TNFα and IL-8, to 12,500 pg/mL for IL-10, to 25,000 pg/mL for IL-1β and IL-6, and to 50,000 pg/mL for IL-4. The minimum average concentrations measured by the standard curves were 0.065, 0.006, 0.017, 0.00013, 0.196, and 0.050 pg/mL for IL-1β, IL-4, IL-6, IL-8, IL-10, and TNFα, respectively. Test samples of equine serum (n = 5) and bronchoalveolar fluid (n = 3) before and after exercise and of ConA-stimulated equine peripheral mononuclear cell supernatants (positive control) were analyzed for each multiplexed assay. With the exception of serum from one horse, all samples ran within detectable limits of each assay. This preliminary work indicates the U-PLEX platform is a viable option to simultaneously quantify concentrations of multiple equine cytokines, allowing for expansion of research efforts focused on understanding immune responses in the horse.