Objectives—To determine effects of selectin inhibitor
TBC1269 on neutrophil infiltration, and neutrophilassociated
injury during pneumonia induced by
Mannheimia haemolytica and concentration of antimicrobial
anionic peptide (AAP) in bronchoalveolar
lavage fluid (BALF) as well as antimicrobial activity of
BALF from healthy (control) neonatal calves, neonatal
calves with M haemolytica-induced pneumonia,
neonatal calves with prior treatment with TBC1269,
and adult cattle.
Animals—Eighteen 1- to 3-day-old calves and 9 adult
Procedure—Calves were inoculated with M
haemolyticaor pyrogen-free saline (0.14M NaCl) solution
into the right cranial lung lobe, and BALF was collected
2 or 6 hours after inoculation. Thirty minutes
before and 2 hours after inoculation, 4 calves received
TBC1269. The BALF collected from 9 adult cattle was
used for comparison of BALF AAP concentration and
antimicrobial activity. Protein concentration and neutrophil
differential percentage and degeneration 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 from calves receiving TBC1269.
Similar concentrations of AAP were detected in BALF
from all calves, which were 3-fold higher than those in
BALF from adult cattle. However, BALF from
neonates had little or no anti-M haemolytica activity.
Conclusions and Clinical Relevance—These results
suggest that TBC1269 decreases 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
haemolytica. (Am J Vet Res 2001;62:665–672)