Abstract
The effects of using an enterotoxigenic Escherichia coli vaccine on innate immune responses following intramammary infusion of lipopolysaccharide (LPS) were investigated in midlactation Holstein-Friesian cows. Seven out of 14 cows were inoculated with E. coli vaccine. Three weeks later, 100μg of LPS dissolved in 10mL of saline was infused into 1 quarter of all cows. Milk was collected every hour from infusion to 12h after infusion, and twice daily (at 0900 and 1600h) for 4d. Blood samples were collected 0, 4, 8, 24, 48, 72, and 96h after infusion. Rectal temperatures and milk yields were measured. The somatic cell count (SCC), lingual antimicrobial peptide concentration, lactoperoxidase (LPO) activity, and lactoferrin (LF) concentration in milk, and haptoglobin concentration in serum were determined. The mean rectal temperature in vaccinated cows was higher than in control cows at 10h. The mean milk yield was decreased significantly in the infused quarter of control cows at 24h compared with pretreatment, but not in vaccinated cows. The mean SCC in milk from vaccinated cows at 12 and 55h was significantly lower than that of control cows. The lingual antimicrobial peptide and LF concentrations were significantly lower at 8h and 55h, respectively, in vaccinated cows than in control cows. The mean antibody titer in the serum against the vaccine at the time of LPS infusion into vaccinated cows was significantly higher than in control cows. These antibody titers were positively correlated with the peak concentrations of LPO and LF in milk following challenge; therefore, cows with a high antibody titer were accompanied by high LPO activity and LF concentration in milk. These results suggest that vaccination suppresses the innate immune reaction after intramammary LPS infusion; however, the elevated antibody titer was unlikely to be responsible for the modification of the innate immune reaction.
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