The Effectiveness of recombinant OL fusion protein (ovalbumin-LHRH-7) in suppressing reproductive functions when injected in single-dose vaccination protocols with different adjuvants

The objective of this study was to evaluate the effectiveness of recombinant LHRH fusion protein, Ovalbumin-LHRH-7 (OL), using a single-dose vaccination protocol in combination with different adjuvants in suppressing reproductive functions in buck kids. For this purpose, either a mixture of free OL antigen and encapsulated OL antigen, or encapsulated OL antigen was used. Thirty-nine native buck kids at 12 weeks of age were divided into control (n = 7) and treatment groups (n = 8 bucks/group). The four treatment groups were formed according to the different vaccine formulations: Group CpG received 0.5 mg free OL protein together with 1.0 mg of encapsulated protein with CpG adjuvant. Group mFCA received 0.5 mg free OL protein together with 1.0 mg of encapsulated protein with modified Freundʹs complete adjuvant. Group IS received 1.5 mg encapsulated OL protein with a mix of inulin and saponin adjuvants. Group ISmFCA received 1.5 mg encapsulated OL protein with a mix of inulin, saponin and modified Freundʹs complete adjuvants. Scrotal circumference in CpG and mFCA groups were significantly smaller than that of Control, IS and ISmFCA groups (P < 0.05). Numbers and percentage of bucks having spermatozoa in their ejaculate were significantly lower in CpG and mFCA groups (P < 0.05). OL immunization completely suppressed sperm production, except one buck, in CpG and mFCA groups (P < 0.05). These results imply that it is possible to use OL protein in a single injection protocol for the purpose of immunocastration. Further investigation with a larger number of animals should be carried out to determine the longevity of response to a single injection.