Immunostimulatory effects of the muramyl dipeptide analogue LK415 in chickens immunized with a vaccine strain of infectious bursal disease virus

The effects of muramyl dipeptide (MDP) synthetic analogue LK415 on the immu ne response of chickens immunized with a live vaccine against infectious bu rsal disease (IBD) were studied in two independent trials, using levamisole hydrochloride as comparative immunostimulant. Groups of five-week-old comm ercial chickens (Isa Brown) were immunized orally with 10 doses of the vacc ine strain of IBDV (Winterfield strain). The chickens were then given four injections of the MDP analogue LK415 in a dosage of either 0.25 mg/kg body weight (b.w.) or 2.5 mg/kg b.w. or levamisole at a daily dose of 15 mg/kg b .w. for four consecutive days, starting from the day of immunization. Histo logical examinations of bursal tissue collected on days 2, 4 and 7 postimmu nization (p.i.) showed a lower degree of destruction of bursal follicles an d earlier renewal of bursal tissue in LK415-treated chickens compared to le vamisole-treated and untreated immunized groups. Compared to the other grou ps, the LK415-treated chickens showed a significantly higher antibody respo nse to IBDV on days 14 and 28 p.i. (P < 0.01) as measured by commercial ELI SA. The present study indicates some potent immunostimulatory effects of th e MDP analogue LK415 on the chicken immune system.