Effects of an anti-gonadoliberin releasing hormone vaccine on testicular, epididymal and spermatogenic development in the horse.

The effects of the GnRH vaccine Improvac® on testicular and epididymal morphometrics, histology and spermatogenesis were measured in 19 young (15-20 months) colts randomly assigned to one control (saline, castration at 57 days, n = 6) or either of two GnRH vaccine-treatment groups, T-57 (castration at 57 days, n = 7) or T-100 (castration at 100 days, n = 6), respectively. All were immunized on Day 0 with a single booster on Day 28. Excised testes and epididymides were weighed and processed for histology to measure tubule, epithelial and muscle dimensions, the ratio of interstitial tissue to seminiferous tubules and determine the stage of spermatogenesis. Testis volume, unchanged within controls, decreased in T-57 and T-100 groups by 50% and 70%, respectively. Treated colts' testes were significantly lighter than controls (64% relative difference); however, epididymal mass showed no significant differences between groups. Proportionally less seminiferous tubule relative to interstitial tissue was observed in both treatment groups (5%) versus controls (22%) with a mean tubule size 28% smaller than controls. Controls exhibited a high proportion of seminiferous tubules with advanced stages of spermatogenesis, whereas treated colts showed a high proportion of tubules in the early stages of spermatogenesis. In conclusion, immunization against GnRH in prepubertal colts was effective at reducing the development of their intra-scrotal reproductive organs and preventing normal spermatogenesis. GnRH vaccination of young colts effectively and consistently reduced testis mass, tubule size and relative proportion of seminiferous tubule tissue while retarding spermatogenesis. The epididymis showed changes with a smaller tubule diameter, lower epithelial height and thicker muscle layer recorded in treated compared to control colts.

Vaccination against GnRH as a prelude to surgical castration of horses.

BACKGROUND: Surgical castration is one of the most frequently performed surgeries in horses and is associated with various post-surgical complications ranging in severity. OBJECTIVES: We investigated the effects of administering an anti-GnRH vaccine to colts for reduction of testis size on the incidence of complications associated with their subsequent surgical castration. STUDY DESIGN: Randomised open controlled trial. METHODS: Nineteen colts were randomly assigned to one of the three groups. Treatment Groups V1-57 and V2-100 received two treatments of Improvac® (Zoetis, South Africa) before their castration in the field on either Day 57 or Day 100 following first treatment, respectively. Controls similarly received placebo treatments followed by castration on Day 57. Serial measurements of testicular dimensions and serum samples for measuring serum testosterone concentrations (STCs) and anti-GnRH antibody titres (ABTs) were obtained pre- and post-vaccination and on the day of castration. Clinical data recorded for 10 days determined post-surgical complications. RESULTS: All vaccinated colts showed a baseline STC concentration at castration with a strong ABT response. Mean testicular volume of Groups V1-57 and V2-100 reduced by 49.7% and 30.8%, respectively, on Day 57 and this further reduced in Group V2-100 by 63.9% at castration on Day 100. Testis size was significantly correlated with post-surgical preputial (P = 0.001) and scrotal (P = 0.025) swelling. MAIN LIMITATIONS: A study population of young light horse breed colts and a relatively small sample size limited this pilot study. CONCLUSIONS: Administering two doses of Improvac® in colts 28 days apart prior to castration effectively reduced their testicular volumes with associated significant post-surgical improvement in both the incidence and degree of local swelling. These results may inform mitigation of potential post-surgical complications associated with castration in the field.

Serum antibody immunoreactivity and safety of native porcine and recombinant zona pellucida vaccines formulated with a non-Freund's adjuvant in horses.

Commercial and regulatory limitations associated with native porcine zona pellucida (pZP) vaccines formulated with Freund's adjuvants may be overcome by developing effective recombinant ZP vaccines (reZP) and identifying alternative adjuvant formulations. A two-part preparatory study used 15 geldings and identified potentially effective alternative adjuvant formulations based on anti-pZP antibody response following treatment with pZP formulated with Addavax (AddaVax ™, Invivogen), Quil A (Quil-A® Adjuvant, Invivogen), Quil A and Poly (I:C) (HMW VacciGrade™, Invivogen), Pet Gel A (Montanide™ Pet Gel A, Seppic) and Pet Gel A and Poly (I:C). Injection site reactions, rectal temperature and respiratory and heart rates were also monitored for three days post-treatment. Suitable anti-pZP antibody titres were seen in response to Pet Gel A and Pet Gel A and Poly (I:C). Subsequently in 31 mares, following administration of pZP, reZP and a combination of pZP and reZP proteins prepared in Pet Gel A and Poly (I:C), both serum anti-pZP and -reZP antibody responses were monitored. In addition, safety was assessed for up to seven days post-treatment by inspection and palpation of gluteal intramuscular injection sites and measurement of rectal temperature. The measured antibody titres in all treatment groups differed significantly to an adjuvant control group (P < 0.001). Temporal changes in both anti-pZP and -reZP antibody titres in all ZP treatment groups were similar to patterns reported previously in various species vaccinated with pZP formulated with Freund's adjuvants. There were no differences in anti-pZP antibody titres between the pZP and reZP treated groups (P > 0.05). Side effects were mild and transient in nature. This represents the first application of a reZP vaccine formulated with non-Freund's adjuvants evoking a similar antibody titre response to native pZP vaccination in mares.