Induction of procoagulant activity in virus infected bovine alveolar macrophages and the effect of lipopolysaccharide

Three viruses known to be associated with the bovine respiratory disease complex were evaluated in vitro for potential impact upon the procoagulant activity (PCA) of bovine alveolar macrophages (bAM). Cultures of bAM were inoculated with bovine parainfluenza virus Type 3 (PI-3), cytopathic bovine viral diarrhea virus (cpBVDV), non-cytopathic BVDV (ncpBVDV), or bovine herpes virus Type 1 (BHV-1) and incubated for several time periods (24, 48, 72, 96 h). BAM were then exposed to E. coli lipopolysaccharide (LPS), or LPS with bovine serum. The amount of PCA expressed was quantified using a chromogenic assay. inoculation increased bAM expression of PCA (P < 0.01). The increase in PCA expression was larger at higher rates of viral inoculation (P < 0.01). LPS enhanced PCA expression by bAM at low rates of viral inoculation (P < 0.01). The effect of LPS-serum treatment was greater than the LPS alone (P < 0.01). At high rates of viral inoculation, LPS had no enhancing effect on PCA expression. The effect of LPS on virus inoculated bAM varied with virus type, rate of inoculation, and duration of virus exposure (P < 0.01). The results suggest that these four viruses initiate the production of PCA by bAM independently of LPS. In the field situation, an initial viral infection may induce fibrin deposition in the pulmonary alveoli prior to the establishment of a secondary gram negatmtive bacterial infection.