Early postnatal immunisation against gonadotrophin-releasing hormone induces a high but differential immune response in heifer calves

Immunization against Gonadotropin-Releasing Hormone in Female Beef Calves to Avoid Pregnancy at Time of Slaughter

Precocious puberty in beef heifers can result in unwanted pregnancies due to accidental breeding by farm bulls. Inbreeding, premature calving followed by dystocia and a high stillbirth rate or slaughtering of pregnant heifers are the consequences of this behaviour. The aim of the study was to postpone puberty by using Improvac^®, an anti-GnRH vaccine. Therefore, n = 25 calves were twice vaccinated, once at the age of 5 and then at 6.5 months. n = 24 calves served as unvaccinated case controls. The onset of puberty was assigned if progesterone analysis in the blood exceeded 1 ng/mL. Progesterone values were excluded if the corresponding serum cortisol levels were ≥60 nmol/L. Our target was met, as in the vaccinated group none of the calves exceeded a progesterone value >1 ng/mL until the scheduled age of slaughter at 11 months and only 12.5% of the animals exceeded a progesterone value of 1 ng/mL over the whole measuring period (>400 days) compared with 56.5% of the calves in the control group. In conclusion, the favourable results from our study using the vaccine Improvac^® represent an animal-friendly, non-invasive and reliable way to avoid early pregnancy in heifers as well as the slaughter of pregnant cattle.

Serological and histological evaluation of species-specific immunocontraceptive vaccine antigens based on zona pellucida 3 in the small Indian mongoose (Herpestes auropunctatus)

The small Indian mongoose (Herpestes auropunctatus) was introduced to Japanese islands and has impacted on the island’s biodiversity. Population control has been attempted through capturing but its efficiency has rapidly declined. Therefore, new additional control methods are required. Our focus has been on the immunocontraceptive vaccines, which act in an especially species-specific manner. The amino-acid sequence of the mongoose ovum zona pellucida protein 3 (ZP3) was decoded and two types of synthetic peptides (A and B) were produced. In this study, these peptides were administered to mongooses (each n=3) and the sera were collected to verify immunogenicity using ELISA and IHC. Treated mongoose sera showed an increasing of antibody titer according to immunizations and the antigen-antibody reactions against the endogenous mongoose ZP. In addition, IHC revealed that immune sera absorbed with each peptide showed a marked reduction in reactivity, which indicated the specificity of induced antibodies. These reactions were marked in peptide A treated mongoose sera, and the antibody titer of one of them lasted for at least 21 weeks. These results indicated that peptide A was a potential antigen, inducing autoantibody generation. Moreover, immunized rabbit antibodies recognized mongoose ZP species-specifically. However, the induction of robust immune memory was not observed. Also, the actual sterility effects of peptides remain unknown, it should be verified as a next step. In any case, this study verified synthetic peptides we developed are useful as the antigen candidates for immunocontraception of mongooses.

Immunization of dogs with recombinant GnRH-1 suppresses the development of reproductive function

This study was designed to evaluate the effect of active immunization using recombinant GnRH-I protein on reproductive function in dogs. Six male and six female dogs were randomly assigned to either a control group or an immunization group (n = 3 males or 3 females/group). Dogs (aged 16 weeks) were immunized against GnRH-I with a maltose-binding protein-gonadotropin-releasing hormone I hexamer generated by recombinant DNA technology. Blood samples were taken at 4-week intervals after immunization. The serum concentrations of testosterone and estradiol and anti-GnRH-I antibodies were determined by RIA and ELISA, respectively. The results showed that active immunization with recombinant GnRH-I increased the serum levels of anti-GnRH antibodies (P < 0.05) and reduced the serum concentrations of testosterone (P < 0.05) and estradiol (P < 0.05) as compared with the controls. At 28 weeks of age, testes and ovaries were taken surgically for morphologic evaluation. Histologic studies performed on testicular and ovarian tissues revealed clear signs of atrophy in the recombinant GnRH-I-immunized dogs and a significant reduction (P < 0.05) in the weights and sizes of paired testes and ovaries in the treated dogs. Microscopically, spermatogonia were visible, but no spermatids and spermatozoa were detected in the seminiferous tubules. Neither early antral nor antral follicles were found in the immunized group. These results demonstrate that recombinant GnRH-I is an effective immunogen in dogs.