Replication of bluetongue virus and epizootic hemorrhagic disease virus in pulmonary artery endothelial cells obtained from cattle, sheep, and deer.

OBJECTIVE: To compare replication of bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) in pulmonary artery endothelial cells (ECs) obtained from juvenile cattle, sheep, white-tailed deer (WTD; Odocoileus virginianus), and black-tailed deer (BTD; O hemionus columbianus). SAMPLE POPULATION: Cultures of pulmonary artery ECs obtained from 3 cattle, 3 sheep, 3 WTD, and 1 BTD. PROCEDURE: Purified cultures of pulmonary artery ECs were established. Replication, incidence of infection, and cytopathic effects of prototype strains of BTV serotype 17 (BTV-17) and 2 serotypes of EHDV (EHDV-1), and (EHDV-2) were compared in replicate cultures of ECs from each of the 4 ruminant species by use of virus titration and flow cytometric analysis. RESULTS: All 3 viruses replicated in ECs from the 4 ruminant species; however, BTV-17 replicated more rapidly than did either serotype of EHDV. Each virus replicated to a high titer in all ECs, although titers of EHDV-1 were significantly lower in sheep ECs than in ECs of other species. Furthermore, all viruses caused extensive cytopathic effects and a high incidence of cellular infection; however, incidence of cellular infection and cytopathic effects were significantly lower in EHDV-1-infected sheep ECs and EHDV-2-infected BTD ECs. CONCLUSIONS AND CLINICAL RELEVANCE: There were only minor differences in replication, incidence of infection, and cytopathic effects for BTV-17, EHDV-1, or EHDV-2 in ECs of cattle, sheep, BTD, and WTD. It is not likely that differences in expression of disease in BTV- and EHDV-infected ruminants are attributable only to species-specific differences in the susceptibility of ECs to infection with the 2 orbiviruses.

Concurrent follicular dysplasia and interface dermatitis in Boxer dogs.

Recurrent or persistent follicular dysplasia and interface dermatitis are described in nine Boxers. Data on age, sex, seasonality of alopecia and histopathological features of the follicular dysplasia in these nine Boxers are comparable with those described in previous reports. The interface dermatitis was characterized by multifocal annular crusted lesions confined to the areas of follicular dysplasia. The inflammatory lesions were neither pruritic nor painful and affected dogs were otherwise healthy. Histopathologically the clinically inflammatory lesions were characterized as an interface dermatitis. Immunohistochemical studies failed to demonstrate immunoglobulins or complement at the basement membrane zone or within blood vessel walls. In dogs with recurrent or persistent disease, the follicular dysplasia and interface dermatitis ran identical, concurrent courses of spontaneous remission and recurrence, or persistence, respectively. One dog with persistent disease was treated successfully with tetracycline and niacinamide for the interface dermatitis, and melatonin for the follicular dysplasia. Although the aetiopathogenesis of this newly described condition and the relationship between the two histological reaction patterns are not known, photoperiod and genetic predisposition appear to play a role.

The role of endothelial cell-derived inflammatory and vasoactive mediators in the pathogenesis of bluetongue.

Bluetongue is an insect-transmitted disease of sheep and wild ruminants that is caused by bluetongue virus (BTV). Cattle are asymptomatic reservoir hosts of BTV. Infection of lung microvascular endothelial cells (ECs) is central to the pathogenesis of BTV infection of both sheep and cattle, but it is uncertain as to why sheep are highly susceptible to BTV-induced microvascular injury, whereas cattle are not. Thus, to better characterize the pathogenesis of bluetongue, the transcription of genes encoding a variety of vasoactive and inflammatory mediators was quantitated in primary ovine lung microvascular ECs (OLmVECs) exposed to BTV and/or inflammatory mediators. BTV infection of OLmVECs increased the transcription of genes encoding interleukin- (IL) 1 and IL-8, but less so IL-6, cyclooxygenase-2, and inducible nitric oxide synthase. In contrast, we previously have shown that transcription of genes encoding all of these same mediators is markedly increased in BTV-infected bovine lung microvascular ECs and that BTV-infected bovine ECs produce substantially greater quantities of prostacyclin than do sheep ECs. Thus, sheep and cattle were experimentally infected with BTV to further investigate the role of EC-derived vasoactive mediators in the pathogenesis of bluetongue. The ratio of thromboxane to prostacyclin increased during BTV infection of both sheep and cattle, but was significantly greater in sheep (P = 0.001). Increases in the ratio of thromboxane to prostacyclin, indicative of enhanced coagulation, coincided with the occurrence of clinical manifestations of bluetongue in BTV-infected sheep. The data suggest that inherent species-specific differences in the production and activities of EC-derived mediators contribute to the sensitivity of sheep to BTV-induced microvascular injury.

Bluetongue virus-induced activation of primary bovine lung microvascular endothelial cells.

Bluetongue is an insect-transmitted viral disease of sheep and some species of wild ruminants. Infection of lung microvascular endothelial cells (ECs) is central to the pathogenesis of bluetongue virus (BTV) infection of ruminants, but it is uncertain as to why cattle are resistant to BTV-induced microvascular injury and bluetongue disease. Thus, in order to better understand the pathogenesis of BTV infection of cattle, mRNAs encoding a variety of inflammatory mediators were quantitated by real-time polymerase chain reaction in primary bovine lung microvascular ECs (BLmVECs) exposed to BTV and/or EC-derived mediators. BTV infection of BLmVECs significantly increased the transcription of genes encoding interleukin-1 (IL-1), IL-6, IL-8, cyclooxygenase-2, and inducible nitric oxide synthase. Treatment of BLmVECs with EC-lysates that contained BTV as well as cytokines increased both the incidence of apoptosis and expression of cellular adhesion molecules, as compared to infection of BLmVECs with BTV alone. Thus, BTV infection caused activation of BLmVECs with production of inflammatory mediators that alter the mechanism of cell death of BLmVECs and exert potentially potent effects on blood coagulation. The activities of BTV-induced-EC-derived inflammatory mediators likely contribute to the resistance of cattle to BTV-induced microvascular injury and bluetongue disease.

Infection kinetics, prostacyclin release and cytokine-mediated modulation of the mechanism of cell death during bluetongue virus infection of cultured ovine and bovine pulmonary artery and lung microvascular endothelial cells.

Bluetongue virus (BTV) infection causes a haemorrhagic disease in sheep, whereas BTV infection typically is asymptomatic in cattle. Injury to the endothelium of small blood vessels is responsible for the manifestations of disease in BTV-infected sheep. The lungs are central to the pathogenesis of BTV infection of ruminants; thus endothelial cells (ECs) cultured from the pulmonary artery and lung microvasculature of sheep and cattle were used to investigate the basis for the disparate expression of bluetongue disease in the two species. Ovine and bovine microvascular ECs infected at low multiplicity with partially purified BTV were equally susceptible to BTV-induced cell death, yet ovine microvascular ECs had a lower incidence of infection and produced significantly less virus than did bovine microvascular ECs. Importantly, the relative proportions of apoptotic and necrotic cells were significantly different in BTV-infected EC cultures depending on the species of EC origin and the presence of inflammatory mediators in the virus inoculum. Furthermore, BTV-infected ovine lung microvascular ECs released markedly less prostacyclin than the other types of ECs. Results of these in vitro studies are consistent with the marked pulmonary oedema and microvascular thrombosis that characterize bluetongue disease of sheep but which rarely, if ever, occur in BTV-infected cattle.