Effects of cecropin B transgene expression on Mannheimia haemolytica serotype 1 colonization of the nasal mucosa of calves.
OBJECTIVE
To express a cecropin B transgene on bovine nasal mucosa and determine the effect on Mannheimia haemolytica serotype 1 (S1) colonization.


METHODS
27 crossbred beef calves.


METHODS
The antibacterial efficacy of cecropin B against M. haemolytica S1 was first determined by measuring its minimum inhibitory concentration (MIC). The peptide was also diluted in pooled bovine nasal secretions, and its antibacterial activity was evaluated. The nasal passages of 16 calves were aerosolized with 25, 50, or 100 microg of plasmid DNA/nostril, whereas 11 control calves were aerosolized with only the transfection reagent. In 2 of the experiments, 12 treated and 8 control calves were exposed intranasally with an aerosol of M. haemolytica S1. Nasal swab specimens and secretions were collected and analyzed by use of polymerase chain reaction (PCR), real-time PCR, real-time reverse-transcriptase PCR, ELISA, and bacterial culture.


RESULTS
In vitro, cecropin B inhibited M. haemolytica S1 at an MIC of 2 microg/mL and its antibacterial activity was not affected by proteolytic activity in nasal secretions. Cecropin B transgene expression was detected in calves transfected with 50 or 100 microg of DNA/nostril. Antibacterial activity against M. haemolytica S1 was observed in all calves transfected with 100 microg of DNA/nostril but in only 2 of the 4 calves transfected with 50 microg of DNA/nostril.


CONCLUSIONS
In vitro, cecropin B has an effective antibacterial activity against M. haemolytica S1 and can prevent colonization of the nasal mucosa after transfection of a vector expressing cecropin B in vivo.
Boudreaux
Charles M
CM
Louisiana Agricultural Experiment Station, Department of Veterinary Science, Louisiana State University Agricultural Center, Baton Rouge 70803, USA.
Corstvet
Richard E
RE
Cooper
Richard K
RK
Enright
Frederick M
FM
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000235:genetics / Q000382:microbiology* / Q000628:therapy*; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D015316:Genetic Therapy / Q000379:methods / Q000662:veterinary*; D019476:Insect Proteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D016978:Mannheimia haemolytica / Q000187:drug effects / Q000254:growth & development* / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D009297:Nasal Mucosa / Q000378:metabolism / Q000382:microbiology; D012766:Pasteurellosis, Pneumonic / Q000382:microbiology* / Q000628:therapy; D010957:Plasmids / Q000235:genetics; D012313:RNA / Q000737:chemistry / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D014162:Transfection / Q000662:veterinary
D019476:Insect Proteins; D012313:RNA; C031162:cecropin B protein, Insecta