Function of prostaglandins, thromboxane A2, and histamine in hypersensitivity reaction to experimental bluetongue disease in calves.

Calves given 2 subcutaneous inoculations (4 ml, 4.5 weeks apart) of an inactivated bluetongue virus serotype 17 (BTV-17), aluminum hydroxide adjuvant, and cimetidine (600 mg) or levamisole (819 mg, 6 ml) combination were challenge exposed with virulent BTV-17 (2.5 x 10(5) embryo lethal dose) 9 weeks after the 1st inoculation and were monitored for 35 days. Plasma prostaglandins (PG) and thromboxane (Tx) B2 were measured by radioimmunoassay. Histamine was assayed spectrofluorometrically. During the inoculation period (9 weeks from the 1st inoculation to challenge exposure) PGE and histamine increased from base-line concentrations of 34 +/- 3 pg/ml and 1.2 +/- 0.1 ng/ml to 83 +/- 8 pg/ml and 2.0 +/- 0.1 ng/ml, respectively, whereas PGF2 alpha decreased from base-line values of 356 +/- 41 pg/ml to 226 +/- 16 pg/ml. Significant (P less than or equal to 0.05) changes from base-line TxB2 values (110 +/- 7 pg/ml) were not observed during the inoculation period. After challenge exposure, maximum increases were observed in TxB2 (157 +/- 10 pg/ml), PGF2 alpha (713 +/- 93 pg/ml), PGE (140 +/- 30 pg/ml), and histamine (3.6 +/- 0.2 ng/ml) concentrations at 4, 7, 7, and 14 days after challenge exposure, respectively. Concentrations of PGF2 alpha and TxB2 decreased from base-line values to 211 +/- 42 pg/ml and 75 +/- 11 pg/ml, respectively, 21 days after challenge exposure and then returned to base-line values. Significant changes were not observed in plasma concentrations of 6-keto-PGF1 alpha. Results indicate that PG, TxA2, and histamine may be involved in the hypersensitivity reaction to BTV in cattle.