Dexamethasone treatment differentially alters viral shedding and the antibody and acute phase protein response after multivalent respiratory vaccination in beef steers

Our objective was to examine immunosuppression induced by dexamethasone (DEX) administration in cattle on immunological responses to a multivalent respiratory vaccine containing replicating and nonreplicating agents. Steers (n = 32; 209 ± 8 kg) seronegative to infectious bovine rhinotracheitis virus (IBRV), bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), and parainfluenza-3 virus (PI3V) were stratified by BW and randomly assigned to 1 of 3 treatments: 1) acute immunosuppression (ACU; 0.5 mg/kg BW DEX intravenously at 1000 h only on d 0), 2) chronic immunosuppression (CHR; 0.5 mg/kg BW DEX intravenously at 1000 h on d −3 to 0), or 3) a control (CON; no DEX). On d −4, steers were fitted with intravenous catheters in the jugular vein and placed into individual stanchions. At 1200 h on d 0, steers were administered a respiratory vaccine containing modified-live virus (MLV) isolates of IBRV, BVDV, BRSV, and PI3V and a Mannheimia haemolytica (MH) toxoid. On d 4, cattle were transported (177 km) and housed in an isolated outdoor pen. Serum was harvested on d 0, 7, 14, 21, 28, 35, 42, and 56 to determine IBRV-, BVDV-, BRSV-, and PI3V-specific antibody titers and MH whole cell and leukotoxin antibody concentrations. Sera from d −2, 0, 1, 3, 7, and 14 were used to quantify haptoglobin (Hp) concentration and ceruloplasmin (Cp) activity. Nasal swab specimens were collected on d 0, 3, and 14 to determine the presence of IBRV, BVDV, BRSV, and PI3V via PCR analysis. There was a treatment × day interaction (P < 0.01) such that CHR steers had a greater (P ≤ 0.07) BVDV antibody titer on d 14, 21, and 28. Moreover, IBRV-specific antibodies increased beginning on d 14 for CHR and on d 28 for ACU and remained greater through d 56 compared with CON (P ≤ 0.03). Conversely, serum MH whole cell antibody concentration was least (P ≤ 0.06) for CHR from d 7 to 28 and greatest for CON (P ≤ 0.04) on d 56. Treatment altered Hp such that CON exhibited a greater (P < 0.01) Hp concentration than CHR but was not different from ACU (P = 0.16). On d 3, Cp was greatest for CON, intermediate for ACU, and least for CHR (treatment × day; P ≤ 0.01). The prevalence of IBRV and BVDV in nasal swabs on d 14 was 67 and 56%, respectively, for CHR; 10 and 10%, respectively, for CON; and 9 and 0%, respectively, for ACU (P ≤ 0.006). Results suggest that CHR allowed increased replication of MLV vaccine agents. Conversely, DEX-induced immunosuppression blunted the acute phase protein and antibody response against the nonreplicating MH toxoid.