Comparison of bronchoalveolar lavage fluid obtained from Mannheimia haemolytica-inoculated calves with and treatment with the selectin without prior inhibitor TBC 1269

Objectives-To determine effects of selectin inhibitor TBC1269 on neutrophii infiltration, and neutrophil-associated injury during pneumonia induced by Mannheimia haemolytica and concentration of antimicrobial anionic peptide (AAP) in bronchoalveolar ravage fluid (BALF) as well as antimicrobial activ ity of BALF from healthy (control) neonatal calves, neonatal calves with M haemolytica-induced pneumonia, neonatal calves with prior treatment with TB C1269, and adult cattle. Animals-Eighteen 1- to 3-day-old calves and 9 adult cattle. Procedure-Calves were inoculated with M haemolytica or pyrogen-free saline (0.14M NaCl) solution into the right cranial lung lobe, and BALF was collec ted 2 or 6 hours after inoculation. Thirty minutes before and 2 hours after inoculation, 4 calves received TBC1269. The BALF collected from 9 adult ca ttle was used for comparison of BALF AAP concentration and antimicrobial ac tivity. Protein concentration and neutrophil differential percentage and de generation in BALF were determined. An ELISA and killing assay were used to determine BALF AAP concentration and antimicrobial activity, respectively. Results-Total protein concentration was significantly decreased in BALF fro m calves receiving TBC1269. Similar concentrations of AAP were detected in BALF from all calves, which were 3-fold higher than those in BALF from adul t cattle. However, BALF from neonates had little or no anti-M haemolytica a ctivity. Conclusions and Clinical Relevance-These results suggest that TBC1269 decre ases pulmonary tissue injury in neonatal calves infected with M haemolytica . Although AAP is detectable in neonatal BALF at 3 times the concentration detected in adult BALF, neonatal BALF lacks antimicrobial activity for M ha emolytica.