Ex vivo coccidioidal antigen chitinase-1 stimulation increases production of interleukin-1β in healthy cats

Objective To evaluate coccidioidal antigen–stimulated production of cytokines in healthy cats and determine optimum testing conditions (ie, incubation time and antigen concentration). Methods 6 client-owned, healthy cats that were seronegative for Coccidioides spp antibodies were included in this prospective experimental study. Whole blood cultures were performed with exposure to PBS (vehicle control) or a coccidioidal antigen (recombinant coccidioidal antigen chitinase-1 [rCTS1]_105–310) at 5 final well concentrations (1 µg/mL, 10 µg/mL, 25 µg/mL, 50 µg/mL, and 75 µg/mL) with incubation times of 12 hours and 24 hours. A validated feline-specific, multiplex bead–based assay was used to measure 10 cytokines in cell culture supernatant. Results Supernatant concentrations of IL-1β increased when stimulated with rCTS1_105–310 for 12 hours at 50 µg/mL (274.4 pg/mL; P = .02) and 75 µg/mL (298.4 pg/mL; P = .003) compared to control (PBS; 102.9 pg/mL). Similarly, IL-1β concentrations increased after exposure to rCTS1_105–310 for 24 hours at 50 µg/mL (340.3 pg/mL) and 75 µg/ mL (364.8 pg/mL) compared to control (110.5 pg/mL; P = .04). Production of IL-1β was greater when whole blood was stimulated with rCTS1_105–310 at 1 µg/mL for 24 hours (237.0 pg/mL) compared with 12 hours (116.8 pg/mL; P = .04). No other differences in cytokine concentrations were identified at either incubation time or rCTS1_105–310 concentration compared to control. Conclusions Exposure of whole blood to rCTS1_105–310 increases production of IL1β in healthy cats. Incubation time and rCTS1_105–310 concentration did not seem to impact production of most cytokines in this study.