Abstract: E. coli heat-labile enterotoxin B subunit (rLTB) exerts most effective adjuvant effects on mucosal immune responses. In order to elucidate the dynamic and the safety of rLTB for clinical use in duck, the concentra- tions of rLTB in sera, histopathological changes and tissue distribution of rLTB were examined. Ducks were bled pri- or to injection and at different time intervals post-intramuscular injection (IM) with 1,50,100 mg/kg rLTB, respec- tively. GM1-ELISA was applied for the determination of rLTB concentration in sera. The autopsy of ducks was con- ducted at different time points after IM of rLTB once a day,3 times in a row. Samples of heart, liver, spleen, lung, kidney and brain were fixed in 10% paraformaldehyde and the tissue sections were examined after coloration with haematoxylin and eosin(HE) or immunohistochemical(IHC) staining. The result showed that there was positive correlation between concentration and duration of rLTB in sera and the dosages of application. In 1 mg/kg group the amount of rLTB peaked at 2 hour post injection (HPI),and started to decline at 6 HPI,and could not be detected at 24 HPI. In 50 mg/kg group and 100 mg/kg group the peak were achieved at 2 HPI and 1 HPI,respectively and began to decrease at 12 HPI,and beyond the detection limit at 48 HPI. The slight cloudy swelling and degeneration of hepa- tocellular,inflammatory cell infiltration in lung were observed in 50 mg/kg group ducks. Obvious cloudy swelling and degeneration of hepatocellular,severe inflammatory cell infiltration in lung and focal necrosis in brain tissue were ob- served in 100 mg/kg group. IHC staining results showed that rLTB was deteceted in all 6 kinds of examined organs and the highest amount rLTB was observed in brain. The conclusion is that the high dosage of rLTB may cause histo- logical lesions and the rLTB should be used under 50 mg/kg for safe in duck.

Key words: E. coli heat-labile enterotoxin B subunit(LTB), Duck, Dynamic, Distribution

CLC Number: 

• S834