Effects of long-term immunization against LHRH and androgen treatment on gonadal function

Palmitic acid-modified GnRH-Th epitope peptide immunocastration vaccine (W/O/W adjuvant) can effectively ensure the castration and reduce the smelly smell in boars

Introduction

Recent studies have demonstrated the effectiveness of Gonadotropin-releasing hormone (GnRH) in inhibiting testicular growth and development in male animals to achieve castration while improving the meat quality of various livestock species, including cattle, sheep, goats, and pigs.

Methods

In this research, a GnRH-Th vaccine was synthesized using the Fmoc solid-phase synthesis technique, and the T helper (Th) antigen was modified with palmitic acid to improve its efficacy. The vaccine was then coated with a water-in-oil-in-water adjuvant to improve stability and safety. After passing safety and stability tests, the vaccine was administered to 13-week-old boars.

Results

The results showed that it was stable, safe, and effective for up to 15 months. Moreover, the vaccine did not negatively affect the growth rate and body weight of the pigs. The palmitic acid-modified "GnRH-Th epitope peptide immunocastration vaccine (Water-in-Oil-in-Water (W/O/W)) effectively reduced the testosterone concentration and achieved castration. The concentration of androstenone and skatole hormones significantly decreased, leading to improved meat quality in the boars. The boars were then slaughtered at 33 weeks of age, and the results showed that the meat quality of the vaccinated boars was superior to that of the non-vaccinated control group (p < 0.05).

Discussion

This study demonstrated that GnRH can safely and effectively achieve immune castration in boars after coupling T cell epitopes, palmitic acid modification and W-O-W coating. Provide a better method for the further development of GnRH and the realization of animal welfare.

Gonadotrophin releasing hormone-based vaccine, an effective candidate for prostate cancer and other hormone-sensitive neoplasms

Prostate growth, development, functions, and neoplastic transformation is androgen dependent. Estrogens have similar effects in the ovary and breast. Previous studies using gonadotrophin releasing hormone (GnRH/LHRH) vaccines have shown the usefulness of immunization against this hormone in prostate (PC) and breast cancer (BC). We have synthesized a peptide mutated at position 6 and attached to the 830-844 tetanic toxoid (TT) helper T cell sequence in the same synthesis process. After repeated pig immunizations, we have demonstrated a vaccine that significantly decreased testes size (p < 0.001), prostate (p < 0.01), seminal vesicles (p < 0.01), and testosterone (T) castration [0.05 nM ml(-1) (p < 0. 01)]. Similar results were obtained in adult male and female healthy dogs and Macaca fascicularis models. These data indicate that this GnRHm1-TT vaccine is safe and able to induce significant tumor growth inhibition in the Dunning R3327-H rat androgen responsive prostate tumor model. In these rats, the immunization induced high anti-GnRH titers concomitant with T castration reduction (p < 0.01) in 90% of the animals tested. In addition, 70% of the responders exhibited tumor growth inhibition (p = 0.02) and a survival rate approximately three times longer that those of untreated rats. These data indicate that GnRHm1-TT vaccine may be a potential candidate in the treatment of PC, BC, and other hormone-dependent cancers.

Changes in spermatogenesis and endocrine function in the ram testis due to irradiation and active immunization against luteinizing hormone-releasing hormone

Spermatogonial stem cell transplantation is a technique that has potential in livestock to enhance genetic gain and generate transgenic offspring through the male germ line. A means for depletion of endogenous germ cells in a recipient's seminiferous tubules is necessary for this technology to be applied. The objectives of this study were to evaluate several methods for depletion of endogenous germ cells in the testes of adult rams and to evaluate ultrasound-guided injections into the rete testes as a means for infusing a suspension into the seminiferous tubules. Sixteen adult rams were randomly divided into 4 treatment groups (n = 4 per group). Treatments consisted of active immunization against LHRH (IMM), localized testicular irradiation (IR), LHRH immunization + irradiation (IMM+IR), and untreated control. Serial bleedings were conducted pretreatment and monthly after treatment for 4 mo, at which time all rams were castrated. Both IMM and IMM+IR rams received exogenous gonadotropin in the form of Perganol weekly for 8 wk before castration to bypass the immunization. All rams also received an ultrasound-guided injection of PBS containing 0.4% trypan blue into the rete testis of one testicle before castration. Rams receiving IMM and IMM+IR treatments had higher (P < 0.05) average percentages of seminiferous tubule cross sections with depleted germ cells compared with controls. Serum testosterone was decreased (P < 0.05) in IMM and IMM+IR rams 1 mo after treatment and throughout the remainder of the study compared with controls and IR rams, which were not different from each other. Serum inhibin concentration was unchanged in all rams following treatment indicating that Sertoli cell function was unaltered. A greater (P < 0.05) average percentage of the total testicular area could be filled with the trypan blue solution by rete testis injection in IMM and IMM+IR rams. These data demonstrate the depletion of endogenous germ cells in adult ram testes without alteration of Sertoli cell viability and function that have potential as methods for preparing recipient animals for germ cell transplantation.

Immunotherapy of prostate cancer in a murine model using a novel GnRH based vaccine candidate

Previous studies with gonadotrophin releasing hormone (GnRH/LHRH) vaccines have shown the usefulness of immunization against this hormone in prostate cancer. To this end, we have generated a completely synthetic peptide modified at position 6 and attached to the 830-844 tetanic toxoid (TT) helper T cell sequence. Through this work we have demonstrated that the GnRHm1-TT molecule was highly immunogenic when it is formulated as an oil-based emulsion adjuvated with Montanide ISA 51. That results correlated directly with testosterone reduction and tumor growth inhibition of the Dunning R3327-H androgen responsive prostate tumor model in rats. GnRHm1-TT, proved to be safe and useful for future clinical trials.

Immune Complex Deposition in Adult Male Sprague-Dawley Rats Chronically Immunized with GnRH

PROBLEM

This study was undertaken to evaluate whether the anti-GnRH antibodies and immune complexes (IC) generated by immunization with GnRH-TT cause cellular damage within the animal.

METHOD OF STUDY

Chronic immunization of rats with GnRH-TT injected i.m. was followed by tissue/organ analysis for immune complex deposition by immunofluorescence microscopy. Two groups were studied: (1) those immunized throughout the experiment until their ultimate demise, and (2) those given a chance to recover from the effects of chronic immunization before final analysis.

RESULTS

GnRH-TT was effective in stopping spermatogenesis, which resumed after withdrawal of the immunogen. Most tissues from chronically immunized animals were not significantly different than controls, however the kidneys of treated animals exhibited a higher accumulation of IC. Despite increased IC deposition, pathologic effects were not detected at the cellular level.

CONCLUSIONS

GnRH-TT is an effective immunocontraceptive although the accumulation of glomerular IC represents a potential deleterious side effect.

Effectiveness of twenty, twenty-five diazacholesterol, avian gonadotropin-releasing hormone, and chicken riboflavin carrier protein for inhibiting reproduction in Coturnix quail

Contraception may provide a useful nonlethal management tool when it is desirable to reduce populations of birds. We tested the efficacy of 20,25 diazacholesterol, and immunization with avian gonadotropin-releasing hormone (AGnRH-I) and chicken riboflavin carrier protein (cRCP) as contraceptives and investigated their modes of action in Coturnix quail (Coturnix coturnix japonica). Females that were paired with males treated with 20,25 diazacholesterol produced lower percentages of eggs that were fertile and hatched. Females treated with 20,25 diazacholesterol and paired with control males laid fewer eggs, and lower percentages of their eggs were fertile and hatched. Treatment with 20,25 diazacholesterol reduced testosterone levels in males and progesterone levels in females. Nonesterified cholesterol levels were reduced, whereas desmosterol levels increased in birds treated with 20,25 diazacholesterol. Treatment with AGnRH-I and cRCP immunocontraceptive vaccines did not decrease average egg production and hatchability or hormone levels, but this failure might have been due to the vaccination protocol. If registered, wildlife managers may be able to use 20,25 diazacholesterol when other methods, such as lethal control, are undesirable for reducing damage caused by specific breeding behaviors such as the building of nests.

Immunization against GnRH in male species (comparative aspects)

Active immunization against gonadotropin-releasing hormone (GnRH) was recognized in the 1970s as a potential means by which the reproductive system of mammals might be shut down for various practical and clinical reasons. Numerous studies in males have been performed since that time to determine the applicability of the technique as an alternative to surgical removal of the testes. Reasons for such immunocastration include improvement of meat and carcass characteristics for cattle, sheep, goats, and swine; improvement in feed efficiency relative to castrates in those same species; reduction in male aggressive behavior; reduction in male-associated odors in goats and swine; and fertility neutralization in pet species. Although application as a fertility control agent in men is unlikely, there is renewed interest in active immunization against GnRH as a means of treating prostate cancers and related steroid-dependent pathologies.

Fertility Control: An Option for Non-Lethal Control of Wild Carnivores?

Three types of fertility control, surgical sterilization, hormonal chemosterilization, and immunosterilization, are reviewed with regard to their potential for controlling problematic populations of carnivores. The fertility control agent and delivery protocol of choice may vary considerably according to: (i) the reason for control; (ii) the degree, urgency and duration of population reduction required; (iii) concerns about ethics and public opinion; and (iv) the status, population dynamics, social structure, mating system, size, behaviour and reproductive endocrinology of the target animals. Although they are often perceived and advocated as more preferable methods of population control than lethal approaches, it is important that wildlife managers as well as members of the public realize that the ethical acceptability of the various fertility control techniques may differ considerably - and that numerous questions regarding their effectiveness, humaneness and ecological safety remain unanswered.

Active immunization against LHRH alone or combined with LHRH-analogue treatment impedes growth of androgen-dependent prostatic carcinoma

PROBLEM

To determine whether active immunization against LHRH can serve as treatment for androgen-dependent prostatic carcinoma.

METHOD

Male rats of Copenhagen X Fisher strain, implanted with Dunning R-3327 prostatic carcinoma cells were either immunized against LHRH, treated with LHRH-antagonist, or received a combined treatment of active immunization against LHRH and LHRH-antagonist.

RESULTS

Testicular histology was consistent with infertility in all treatment groups. The rate of tumor growth was inhibited by all three treatment regimens. Tumor size increased by 3.8 +/- 1.4 cm2 in the LHRH-antagonist group, 3.2 +/- 1.1 cm2 in the immunized group, and 1.0 +/- 0.4 cm2 in the combined treatment group, as compared to 8.2 +/- 2.6 cm2 in non-treated control group.

CONCLUSION

LHRH-antagonist administration combined with immunization against LHRH appeared to exert a synergistic effect. This may be due to the blockade of prostatic LHRH-like receptors by the antagonist, while androgen depletion was rapidly achieved by LHRH-antagonist, and maintained by continued gonadotropin suppression caused by active immunization against LHRH once antagonist treatment had been discontinued.

Basic aspects of immunomodulation through active immunization

This paper reviews how immunomodulation through active vaccination has evolved in the past 25 years. Although initially it progressed isolated from the main stream of immunological research and vaccine development, lately it merged with this main stream and is taking full advantage of the newest developments in vaccinology. The first immunomodulation vaccine is already on the market, while various others are close to it. Not in the least because one of the major stumbling blocks of immunomodulation through active vaccination, the inherent low immunogenicity of 'self' antigens, has in a number of other cases been solved. Most progress has been made in veterinary applications and has helped to formulate practical rules, necessary to break immunotolerance. It is not unlikely that these rules will be used to design better immunomodulation vaccines to be used in humans; notably to control fertility or combat tumours.

A vaccine that prevents pregnancy in women

We report here results of clinical trials on a birth control vaccine, consisting of a heterospecies dimer of the beta subunit of human chorionic gonadotropin (hCG) associated noncovalently with the alpha subunit of ovine luteinizing hormone and conjugated to tetanus and diphtheria toxoids as carriers, that induces antibodies of high avidity (K(a) approximately 10(10) M-1) against hCG. Fertile women exposed to conception over 1224 cycles recorded only one pregnancy at antibody titers of > 50 ng/ml (hCG bioneutralization capacity). The antibody response declines with time; fertility was regained when titers fell to < 35 ng/ml. This study presents evidence of the feasibility of a vaccine for control of human fertility.

Efficient immunocastration of male piglets by immunoneutralization of GnRH using a new GnRH-like peptide

Active immunization to immunomodulate regulatory processes suffers from the disadvantage that the antigen is usually 'self' and therefore poorly immunogenic. This has been well illustrated by the long-standing experience with immunocastration vaccines targeting GnRH, a ten amino acid peptide. Not all animals vaccinated with these vaccines are equally affected, even after multiple vaccinations. This is a severe handicap when immunocastration vaccines are applied to male piglets to circumvent surgical castration. Surgical castration is universally practised to prevent boar taint, produced in the testicles of mature boars. Alternative immunocastration is only acceptable if all animals are equally affected using a minimum of vaccinations. Vaccines based on the GnRH peptide itself cannot meet these goals. We showed that using a GnRH-like peptide, a 20 amino acid tandem repeat of the amino acid sequence of the GnRH peptide, these goals can be attained. Using the tandem GnRH peptide to vaccinate male piglets completely abolished the development and endocrinological functioning of the testicles, in contrast to monomer GnRH. These results show that superior antigens can be made for effective immunomodulation by appropriate alteration of the antigen.

Immunoregulation of mammalian fertility

Fertility management is a global issue of agricultural, medical, economic, and social consequence. Although many methods have been devised to both inhibit and assist reproduction, more acceptable alternatives are needed. Regulation by immune intervention is a promising technology as applied to livestock, pets, wildlife, and human beings. Outcome is dictated by site within the reproductive axis that is targeted. Fertility is suppressed by immunization against gonadotropin-releasing hormone, gonadotropins, prostaglandin F2 alpha, oxytocin, gonadotropin receptors, and gamete/embryonic antigens. It also is possible to lyse gonadal cells with ligand-antibody hybrid molecules. Ovulation rates are enhanced by vaccination with inhibin. Antibodies to sex steroid hormones have yielded mixed results. Perhaps recombinant viral vectors can be used to deliver reproductive immunogens. A new and simple technique to generate sustained autoimmune reactions to hormones and cellular antigens entails direct gene transfer into somatic cells. Evolving advances in reproductive immunology and biotechnology should furnish us with novel nonsurgical contraceptives and profertility agents that can be efficiently and safely implemented.

Synthetic gonadotrophin-releasing hormone (GnRH) vaccines incorporating GnRH and synthetic T-helper epitopes

A vaccine against the gonadotrophin-releasing hormone (GnRH) is being developed as an immunological method for treatment of prostatic hypertrophy, based on the observation that active immunization against GnRH leads to the production of anti-GnRH antibodies which results in the shrinkage of the prostate gland. We have been investigating the regulation of anti-GnRH antibody responses by carrier molecules. In previous studies we showed that the use of large protein molecules as carriers limits the use of such a vaccine owing to potential problems of carrier-induced anti-haptenic suppression. In this report we show that synthetic T-helper epitopes can be used as carriers for the generation of anti-GnRH antibody responses.

Anti-LHRH and anti-pituitary gonadotropin vaccines: their development and clinical applications

Active immunization against hormones involved in the regulation of reproduction is a promising approach to immunocontraception. The hypothalamic peptide, LHRH, controls the synthesis and release of the pituitary gonadotropins, LH and FSH, which regulate gonadal steroidogenesis, sperm production, follicular development and ovulation. Immunizing female primates against LHRH or LH induces infertility, but also disrupts the menstrual cycle. Immunization against the beta subunit of the placental hormone, chorionic gonadotropin (hCG), or its fragment prevents pregnancy without interfering with menstrual cycles or ovulation. hCG vaccines have reached the stage of clinical trials. FSH and LHRH have been tested for immunocontraception in male primates. While active as well as passive immunization against FSH reduced spermatogenesis severely, azoospermia could not be achieved consistently. Immunization against LHRH effectively suppressed spermatogenesis in rats and rabbits. Normal sexual behaviour was maintained by concomitant androgen administration. Fertility was restored when antibody titres declined and no adverse effects were observed. A number of LHRH vaccine preparations are being tested in men in several countries, including the United States. Since the LHRH vaccine reduces serum testosterone levels the first clinical studies involve men with prostate cancer. These trials will be followed by immunization of normal men if the antibody response is sufficient and no adverse effects are observed.

Immunoneutralization of gonadotropin-releasing hormone and subsequent treatment with testosterone Silastic implants in rats: an approach toward developing a male contraceptive

STUDY OBJECTIVE

To determine the extent to which increasing doses of exogenous testosterone (T) administered via Silastic implants can restore spermatogenesis and fertility to rats made azoospermic by active immunization against gonadotropin-releasing hormone (GnRH).

DESIGN

Male rats were made azoospermic by active immunization against GnRH. Increasing doses of exogenously administered T (via Silastic implants) were administered for 8 weeks, and testicular sperm concentration and ability to impregnate female rats were evaluated.

SETTING

Reproductive Endocrinology Laboratory, Department of Obstetrics and Gynecology, University of Colorado Health Sciences Center, Denver, Colorado.

ANIMALS

Sexually mature male Sprague Dawley rats (SASCO, Omaha, NE).

RESULTS

Suppression of gonadotropins and azoospermia was achieved by actively immunizing rats against GnRH. Testosterone was capable of restoring quantitatively complete spermatogenesis and fertility in GnRH-immunized azoospermic rats. This relationship was dose-dependent, as evidenced by the partial restoration of spermatogenesis and fertility observed in animals replaced with smaller T Silastic implants.

CONCLUSION

Gonadotropin-releasing hormone immunization and T-filled Silastic implants may provide a model to study isolated gonadotropin deficiency and for the development of a reversible male contraceptive.

Active immunization against LHRH: I. Effects of conjugation site and dose

Active immunization against LHRH is a promising method of contraception for men. In order to be acceptable, sufficient amounts of anti-LHRH antibodies must be induced rapidly after vaccination. In previously reported animal studies, we found that it took considerable time (up to 5 months) to obtain antibody titers (AT) that were sufficiently high for complete suppression of spermatogenesis. The possibility of accelerating the immune response to LHRH by increasing the dose of immunogen was investigated in the male rat. Six doses of LHRH conjugated to tetanus toxoid (TT) in the 10 position (LHRH10-TT), ranging from 2.5 to 612 micrograms, and three doses of LHRH1-TT (50 to 612 micrograms) were tested. The magnitude of the immune response did not depend on the dose of the antigen, provided a threshold dose had been surpassed. Antigenicity of LHRH conjugated to TT at either the 1-, 6-, or 10-position was compared in rats and rabbits. In both species LHRH1-TT induced sufficient antibody concentrations to suppress pituitary gonadotropins (LH and FSH) and, subsequently, serum testosterone (T) levels faster than either the 6- or 10-conjugates. Only materials permitted for use in humans were utilized in these experiments.

CONCLUSION

Active immunization against LHRH conjugated to TT at the 1-position has potential as a fast, convenient method of male contraception.