Effects of GnRH immunization in sexually mature pony stallions

Reversible Contraception in Males: An Obtainable Target?

The last few decades have brought contraception to the forefront of research, with great strides made in effectively targeting and optimizing the physiology, pharmacology, and delivery processes that prevent pregnancy. However, these advances still predominantly target female contraceptives for the prevention of contraception, whereas targeting the male sex has lagged far behind. This has led to a marked deficiency in safe and effective male contraceptive agents, resulting in a heavy dependence on female contraceptives to prevent unwanted and unplanned pregnancies. Current research in the veterinary field and in rodents highlights several promising avenues whereby novel, safe, and effective male contraceptive alternatives are being developed-with an emphasis on reduced side effects and reversibility potential. This review aims to discuss current and novel male contraceptives (both human and veterinary formulations) while highlighting their efficacy, advantages, and disadvantages.

Endocrine changes induced by GnRH immunisation and subsequent early re-stimulation of testicular function with a GnRH agonist in stallions

CONTEXT

Resumption of testicular function after gonadotrophin-releasing hormone (GnRH) immunisation varies among individual animals and some stallions regain fertility only after a prolonged time.

AIMS

This study evaluated endocrine effects of GnRH immunisation and early subsequent re-stimulation with a GnRH agonist. We hypothesised that GnRH agonist treatment advances resumption of normal endocrine function in GnRH-vaccinated stallions.

METHODS

Shetland stallions were assigned to an experimental and a control group (n =6 each). Experimental stallions were GnRH-immunised twice, 4weeks apart. Each experimental stallion was hemicastrated together with an age-matched control animal when testosterone concentration decreased below 0.3ng/mL. Three weeks later, daily treatment with the GnRH agonist buserelin was initiated (4μg/day for 4weeks followed by 8μg/day). The remaining testicle was removed when testosterone concentration exceeded 0.5ng/mL in vaccinated stallions. Blood was collected for LH, FSH, oestradiol and anti-müllerian hormone (AMH) analyses, and testicular and epididymal tissue were conserved for real-time qPCR and histology.

KEY RESULTS

GnRH vaccination reduced blood concentrations of LH and FSH, with a structural deterioration of testicular tissue and disruption of spermatogenesis. Daily buserelin treatment for approximately 60days partially restored gonadotropin secretion and induced a recovery of the functional organisation of the testicular tissue with effective spermatogenesis.

CONCLUSIONS

Endocrine testicular function can be restored in GnRH-vaccinated stallions by daily low-dose buserelin treatment. The buserelin treatment protocol may potentially be improved regarding the dose, interval and duration.

IMPLICATIONS

Daily buserelin treatment can be recommended for treatment of GnRH-vaccinated stallions with prolonged inhibition of testicular function.

Carbohydrate fatty acid monosulphate ester is a potent adjuvant for low-dose seasonal influenza vaccines

There is still a need for a better and affordable seasonal influenza vaccine and the use of an adjuvant could solve both issues. Therefore, immunogenicity of a combination of low dose of 1/5TH (3 µg of HA) a licensed seasonal flu vaccine with the novel carbohydrate fatty acid monosulfate ester (CMS)-based adjuvant was investigated in ferrets and safety in rabbits. Without CMS, hemagglutination inhibition (HI) antibody titers ranged from ≤5 to 26 three weeks post immunization 1 (PV-1) and from 7 to 134 post-immunization 2 (PV-2) in ferrets. Virus neutralizing (VN) antibody titers ranged from 20 to 37 PV-1 and from 21 to 148 PV-2. CMS caused 10 to 111- fold increase in HI titers and 3 to 58- fold increase in VN titers PV-1 and PV-2, depending on influenza strain and dose of adjuvant. Eight mg of CMS generated significantly higher antibody titers than 1 or 4 mg, while 1 and 4 mg induced similar responses. Three µg of HA plus 4 mg of CMS was considered the highest human dose and safety of two-fold this dose was determined in acute and repeated-dose toxicity studies in rabbits conducted according to OECD GLP guidelines. The test item did not elicit any clinical signs, local reactions, effect on body weight, effect on urine parameters, effect on blood biochemistry, or gross pathological changes. In blood, increased numbers of neutrophils, lymphocytes and/or monocytes were noted and in iliac lymph nodes, increased cellularity of macrophages of minimal to mild degree were observed. In both ferrets and rabbits, body temperature increased with increasing dose of CMS to a maximum of 1 ˚C during the first day post-immunization, which returned to normal values during the second day. In the local tolerance study, histopathology of the site of injection at 7 days PV-1 revealed minimal, mild or moderate inflammation in 5, 8 and 5 animals, respectively. In the repeated-dose study and 21 days PV-3, minimal, mild or moderate inflammation was observed in 15, 18 and 3 animals, respectively. We concluded that the data show CMS is a potent and safe adjuvant ready for further clinical development of a seasonal influenza vaccine and combines high immunogenicity with possible antigen-sparing capacity.

Effect of GnRH immunocastration on immune function in male rats

The present study aimed to reveal the effects of immunocastration on the development of the immune system in rats. Seventy rats were randomly assigned into two groups: Control (n = 35) and immunized (n = 35). Twenty-day-old rats were immunized with gonadotropin-releasing hormone (GnRH) and booster immunization was administered every two weeks (three immunizations in total). From 20-day-old rats, we collected samples every two weeks, including five immunized rats and five control rats (seven collections in total). We collected blood samples, testicles, thymuses, and spleens. The results showed that GnRH immunization increased the GnRH antibody titers and reduced the testosterone concentration (both P < 0.05). Compared with the control group, the number of CD4+CD8- cells, CD4-CD8+ cells, and CD4+CD8+ cells increased (P < 0.05) whereas the number of CD4-CD8- cells and CD4+CD25+ cells reduced in the immunized group (P < 0.05) over time. GnRH immunization also increased the relative weights of thymus and spleen (P < 0.05), serum concentrations of interleukin (IL)-2, IL-4, IL-6, IL-10, IL-17 and Interferon-γ (IFN-γ) over time (P < 0.05), and changed the mRNA levels of IL-2, IL-4, IL-6. IL-10, IL-17, IFN-γ, CD4, D8, CD19 GnRH, and GnRH receptor (GnRH-R) in thymus and spleen. Thus, GnRH immunization enhanced the immune markers in thymus, spleen, and blood immune cytokines in rats.

Re-stimulation of testicular function in GnRH-vaccinated stallions by daily GnRH agonist treatment

In stallions temporarily not intended for breeding, reversible suppression of testicular function by vaccination against GnRH can be of interest. In the present study, effects of GnRH agonist treatment on the resumption of testicular function after GnRH vaccination were investigated. Testis size, testosterone release, semen characteristics and behavior were evaluated. We hypothesized that GnRH agonist treatment would restore testicular function. Shetland stallions were assigned to an experimental and a control group (n = 6 each). Experimental stallions were GnRH-immunized twice, four weeks apart. Ejaculates for semen analysis and blood for analysis of testosterone concentration and GnRH antibody titers were collected. Each experimental stallion was hemicastrated together with an age-matched control animal when testosterone concentration decreased below 0.3 ng/mL. Three weeks thereafter, daily treatment with the GnRH agonist buserelin was initiated (4 μg/day for 4 weeks followed by 8 μg/day). The remaining testicle was removed when testosterone concentration exceeded 0.5 ng/mL in vaccinated stallions. Time from exposure to a mare until mounting increased in GnRH-vaccinated stallions and decreased with buserelin treatment. Total sperm count decreased after vaccination but increased only slightly in response to buserelin. Sperm motility and percentage of membrane-intact spermatozoa decreased after vaccination and returned to pre-vaccination values with buserelin treatment. Testosterone concentration and testis volume decreased after GnRH vaccination and started to increase with buserelin treatment. In conclusion, the downregulation of testicular function by GnRH vaccination can be counteracted with buserelin. This approach may be useful in GnRH-vaccinated stallions with prolonged suppression of testicular function.

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.

CoVaccine HT™ adjuvant is superior to Freund's in eliciting ovine polyclonal antibodies against human tumor necrosis factor-alpha

INTRODUCTION

Passive immunotherapy using polyclonal antibodies plays an important role in preventing and treating antigenic and pathogenic diseases. Polyclonal antibodies are used for therapeutic, diagnostic and investigational purposes, with adjuvants employed to enhance the immune response against proteins that are poorly antigenic or self-antigens. This study aimed to optimize current immunization methods by evaluating the novel adjuvant CoVaccine HT™ against the established Freund's at producing ovine polyclonal antibodies against pro-inflammatory cytokine human recombinant tumor necrosis factor alpha (TNF-α).

METHODS

Castrated male Aberfield cross sheep were immunized with TNF-α in CoVaccine HT™ or Freund's adjuvant. The binding titer of antibodies for TNF-α and neutralization titer were determined in vitro, as well as the strength of antibody binding by a simple small scale affinity chromatography elution experiment. Animal welfare was monitored through inspection of immunization site reactions at regular time points and graded according to reaction size. The second part of the study looked at re-immunization using Freund's adjuvant alone every 4- or 8-weeks.

RESULTS

Freund's generated significantly higher antibody binding titers than CoVaccine HT™ but were less effective at neutralizing TNF-alpha which is a better indicator of functional potency. CoVaccine HT™ also caused fewer immunization site reactions, while no statistical difference was observed in the binding strength of antibodies. Re-immunization every 4- and 8-weeks showed no statistical difference.

CONCLUSION

This study provides evidence that CoVaccine HT™ is superior to Freund's adjuvant for the production of antibodies to TNF-α, and supports the use of this alternative adjuvant for clinical and experimental use. The outcomes gained through this study are applicable to passive and active immunotherapy for the generation of polyclonal antibodies in human and veterinary medicine.

A dual kisspeptin-GnRH immunogen for reproductive immunosterilization

GnRH immunogens have been extensively employed in immunocontraception of animals. While they are effective, they are not 100% efficacious and of limited duration. GnRH secretion is dependent on upstream stimulation by kisspeptin. We therefore hypothesised that a dual immunogen combining GnRH and kisspeptin may be more efficacious through targeting two levels of the axis. We have previously shown GnRH immunogen elicits permanent sterilisation when sheep are vaccinated neonatally suggesting that the efficacy of GnRH immunisation may be dependent on the stage of reproductive development. We have now studied over 300 days the efficacy of immunisation with a dual immunogen comprising GnRH linked to kisspeptin via a hepatitis B T helper peptide sequence (GKT) administered to male and female rats prepubertally, pubertally and as adults. At all stages of development all immunised animals produced antibodies to GnRH, kisspeptin and GKT but differentially in titre with respect to sex and stage of development. In immunised adult, prepubertal and pubertal males testosterone and testes length was markedly reduced by 60 days and remained at low levels until day 150. Thereafter, testosterone recovered to pre immunisation levels and testes length increased to a maximum of about 40% of controls. 80% of males were infertile in three matings over 250 days. In prepubertal and pubertal female rats a single immunisation at day 0 reduced estradiol to low levels by day 60 which remained low until termination of the experiment on day 300. In matings of these females with fertile males on days 90, 120 and 250, 74% of prepubertal females were infertile and impressively, 100% (10/10) of pubertal females were infertile after a single immunisation on day 0. These findings set the scene for exploration of immunosterilisation of wild and domestic animals after a single immunisation.

Immunocontraception of male and female giraffes using the GnRH vaccine Improvac®

The aim of this study was to develop protocols for contraception in both sexes of giraffes (Giraffa camelopardalis) by using the GnRH vaccine Improvac®. We evaluated the success of immunization by analyzing fecal reproductive hormone metabolites in female (n = 20) and male (n = 9) giraffes. Endocrine analysis provided the basis for the successful immunization protocol, as well as for assessing long-term effects. Reliable reduction of fecal steroid metabolites to baseline levels in female giraffes was achieved with three, and in males with four or five injections at 4-week intervals. Effective booster injections were administered at 2-month intervals in the first year of treatment and at three to 4-month intervals in the following years. In addition to endocrine analysis, we determined vaccination efficacy in bulls by assessing testicular atrophy. Long-term (>2 years) use in females was often accompanied by prolonged periods of persistent corpus luteum activity, although normal cycles were not observed. Problems might occur with reversibility, because in a few males and females, even after more than 2 years since treatment had been stopped, fecal hormone metabolites have not returned to pretreatment levels. The results are somewhat ambiguous, as reproduction can be suppressed by use of Improvac®, but the question of reversibility remains unsolved.

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.

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.

Inhibitory effects of long-term repeated treatments of a sustainable GnRH antagonist, degarelix acetate, on caprine testicular functions

We investigated the effects of long-term repeated treatments with a sustainable gonadotropin-releasing hormone (GnRH) antagonist, degarelix acetate, on testicular hormonal secretion, size, ultrasound images, histology and spermatogenesis in goats to assess its efficacy as a chemical castration method. Male Shiba goats (3–6 months of age) were treated subcutaneously with degarelix acetate every 4 weeks for 24 weeks. Plasma testosterone and insulin-like peptide 3 concentrations decreased (P < 0.05) within 2 days after the first treatment and remained low until 29 weeks (P < 0.05). Scrotal circumference and testicular pixel intensity were lower from 2–6 months and from 1–6 months, respectively, compared to the pretreatment values (P < 0.05). The testis and epididymis weights were lower at 24 weeks compared to those in untreated goats (P < 0.05). There were no sperm in the seminiferous tubules of testicular tissue sections or in homogenates of the epididymis at 24 weeks. These results suggest that repeated treatment with degarelix acetate is an effective chemical castration method for goats.

Reproductive and Behavioral Evaluation of a New Immunocastration Dog Vaccine

Simple Summary

Population control of free-roaming dogs is a topic of great interest worldwide. Immunocastration (immune blockade of GnRH-I, the hormone that commands reproductive ability) has emerged as a complementary alternative to surgical castration. In this work, the effectiveness of an immunocastration vaccine for dogs was evaluated, as were the reproductive and behavioral characteristics of vaccinated animals. Two consecutive trials were carried out for this purpose. A first trial was conducted under experimental conditions, observing an immune response against the vaccine over a nine-month period that was associated with changes in the testicular function of the animals (decrease in testosterone and alteration of the characteristics of the ejaculate). The second trial was conducted on dogs who had owners, and vaccinated animals showed an immune response against the five-month vaccine and a decrease in unwanted behaviors associated with the presence of sex hormones. While more studies are needed, this vaccine is emerging as a promising tool for the reproductive and behavioral management of male dogs.

Abstract

Canine immunocastration development has been of interest for many years as a complementary strategy to surgical castration. The purpose of this paper was to verify the effect of a recombinant vaccine for dog immunocastration. Two tests were done, one under controlled conditions and a second under field conditions. Animals were injected with 1 mL of 500 µg GnRXG/Q recombinant protein; 500 µg of low molecular weight chitosan as adjuvant; 1 mL NaCl 0.9% q.s. In the first trial, eight Beagle male dogs between the ages of 1 and 3 comprised the sample, randomly divided into two groups: vaccinated group (n = 7) and control group (n = 2). The second trial had 32 dogs with owners. In the first controlled conditions trial, the vaccine produced specific antibodies that remained until the end of the trial (day 270), inducing reduced testosterone and spermiogram changes in the immunized animals. In a second trial, on the field, specific immunity was induced, which remained high up to day 150. The vaccine also reduced sexual agonistic and marking behaviors. This new vaccine proved to be safe, immunogenic, capable of reducing gonadal functionality, and had a positive effect on inducing reduced sexual, agonistic, and marking behavior of the animals.

Use of anti-gonadotropin-releasing hormone vaccines in African elephants (Loxodonta africana): A review

Background: Androgen-related aggressive behaviour and musth cause serious problems in captive African elephant bulls and often lead to human and animal injuries, and damage to property.Objectives: To review the work carried out with anti-gonadotropin-releasing hormone (GnRH) vaccines to control androgen-related behaviour and fertility in captive and free-ranging elephant bulls and the induction of anoestrus in elephant cows.Method: In the first study, an anti-GnRH vaccine from Pepscan was tested in six bulls (four captive and two free-ranging). Once the vaccine Improvac® became available, the effect on behaviour, the reproductive organs and semen quality was tested. Improvac® was also used to attempt induction of anoestrus in elephant cows.Results: The first study proved that aggressive behaviours are significantly associated with increased faecal androgen concentrations. Musth (n = 1) and aggressive behaviour (n = 2) were down regulated and correlated with a decline in faecal androgen concentrations. Aggression and musth could be controlled with Improvac® (600 µg), but were more consistent when the dose was increased to 1000 µg administered every five to six months. The same dose down regulated testicular function and bulls (n = 17) were rendered infertile within 12 months after commencement of treatment. Initial attempts to induce anoestrous with 600 µg in free-ranging elephant cows gave inconclusive results, but 1000 µg in captive cows delivered five-monthly was successful.Conclusion: The treatment of elephant bulls with Improvac® resulted in the successful down-regulation of androgen-related behaviour and sperm production in captive and wild elephant bulls of various ages (≤ 34 years). Preliminary studies to induce anoestrus in cows with Improvac® appear to be successful.

Reproductive effects of arteriviruses: equine arteritis virus and porcine reproductive and respiratory syndrome virus infections

Equine arteritis virus (EAV) and porcine reproductive and respiratory syndrome virus (PRRSV) are the most economically important members of the family Arteriviridae. EAV and PRRSV cause reproductive and respiratory disease in equids and swine, respectively and constitute a significant economic burden to equine and swine industries around the world. Furthermore, they both cause abortion in pregnant animals and establish persistent infection in their natural hosts, which fosters viral shedding in semen leading to sexual transmission. The primary focus of this article is to provide an update on the effects of these two viruses on the reproductive tract of their natural hosts and provide a comparative analysis of clinical signs, virus-host interactions, mechanisms of viral pathogenesis and viral persistence.

The immune profile induced is crucial to determine the effects of immunocastration over gonadal function, fertility, and GnRH-I expression

PROBLEM

Immunocastration or vaccination against the GnRH-I hormone is a promising alternative to reproductive control in different animal species. Given the low immunogenicity of this hormone, the use of adjuvants becomes necessary.

METHOD OF STUDY

This study evaluated the effects of three adjuvants that induce different immune response profiles over gonadal function, fertility, and expression of GnRH-I. Female mice (n = 6) were vaccinated at days 1 and 30 with a recombinant antigen for immunocastration and different adjuvants that induced preferentially Th1/Th2, Th2, and Th1 immune profiles.

RESULTS

Th1/Th2 response is the most efficient to block reproductive activity in vaccinated animals, reducing the number of luteal bodies and pre-ovulatory follicles. Th2 and Th1/Th2 responses induced an increase in GnRH-I at the hypothalamus.

CONCLUSION

The immune profile induced by different adjuvants is essential on the effects over fertility, gonadal function, and hypothalamic GnRH-I expression in immunocastrated animals.

Carbohydrate fatty acid monosulphate esters are safe and effective adjuvants for humoral responses

Carbohydrate fatty acid sulphate esters (CFASEs) formulated in a squalane-in-water emulsion are effective adjuvants for humoral responses to a wide range of antigens in various animal species but rise in body temperature and local reactions albeit mild or minimal hampers application in humans. In rabbits, body temperature increased 1°C one day after intramuscular (IM) injection, which returned to normal during the next day. The effect increased with increasing dose of CFASE but not with the number of injections (up to 5). Antigen enhanced the rise in body temperature after booster immunization (P<0.01) but not after priming. Synthetic CFASEs are mixtures of derivatives containing no sulphate, one or multiple sulphate groups and the monosulphate derivatives (CMS) were isolated, incorporated in a squalane in-water emulsion and investigated. In contrast to CFASE, CMS adjuvant did not generate rise in body temperature or local reactions in rabbits immunized with a purified, recombinant malaria chimeric antigen R0.10C. In comparison to alum, CMS adjuvant revealed approximately 30-fold higher antibody titres after the first and >100-fold after the second immunization. In ferrets immunized with 7.5μg of inactivated influenza virus A/H7N9, CMS adjuvant gave 100-fold increase in HAI antibody titres after the first and 25-fold after the second immunisation, which were 10-20-fold higher than with the MF59-like AddaVax adjuvant. In both models, a single immunisation with CMS adjuvant revealed similar or higher titres than two immunisations with either benchmark, without detectable systemic and local adverse effects. Despite striking chemical similarities with monophospholipid A (MPL), CMS adjuvant did not activate human TLR4 expressed on HEK cells. We concluded that the synthetic CMS adjuvant is a promising candidate for poor immunogens and single-shot vaccines and that rise in body temperature, local reactions or activation of TLR4 is not a pre-requisite for high adjuvanticity.

Non-surgical sterilisation methods may offer a sustainable solution to feral horse (Equus caballus) overpopulation

Feral horses are a significant pest species in many parts of the world, contributing to land erosion, weed dispersal and the loss of native flora and fauna. There is an urgent need to modify feral horse management strategies to achieve public acceptance and long-term population control. One way to achieve this is by using non-surgical methods of sterilisation, which are suitable in the context of this mobile and long-lived species. In this review we consider the benefits of implementing novel mechanisms designed to elicit a state of permanent sterility (including redox cycling to generate oxidative stress in the gonad, random peptide phage display to target non-renewable germ cells and the generation of autoantibodies against proteins essential for conception via covalent modification) compared with that of traditional immunocontraceptive approaches. The need for a better understanding of mare folliculogenesis and conception factors, including maternal recognition of pregnancy, is also reviewed because they hold considerable potential in providing a non-surgical mechanism for sterilisation. In conclusion, the authors contend that non-surgical measures that are single shot and irreversible may provide a sustainable and effective strategy for feral horse control.

Prospects for immunocontraception in feral horse population control: exploring novel targets for an equine fertility vaccine

Feral horses populate vast land areas and often induce significant ecological and economic damage throughout the landscape. Non-lethal population control methods are considered favourable in light of animal welfare, social and ethical considerations; however, no single effective, safe and species-specific contraceptive agent is currently available for use in free-ranging wild and feral horses. This review explores aspects of equine reproductive physiology that may provide avenues for the development of specific and long-lasting immunocontraceptive vaccines and some of the novel strategies that may be employed to facilitate appropriate antigen discovery in future research. Potential antigen targets pertaining to spermatozoa, the ovary and oocyte, as well as the early conceptus and its associated factors, are reviewed in the context of their suitability for immunocontraceptive vaccine development.

Immunocontraception for Animals: Current Status and Future Perspective

An alternative to surgical sterilization for fertility control of animals (wild, zoo, farm, and domestic) is needed to prevent problems related to overpopulation, including culling and relocation. A PubMed and Google Scholar database search was conducted using the keywords 'contraceptive vaccine animals,' 'immunocontraception animals,' 'non-surgical sterilization animals,' 'PZP vaccine,' and 'GnRH vaccine.' The searches from 1972 to 2015 yielded over 1500 publications. These articles were read, and 375 were selected for detailed analysis. Articles referenced in these publications were also thoroughly examined. PZP and GnRH contraceptive vaccines (CVs) have been extensively investigated for fertility control of wild, zoo, farm, and domestic animal populations. Both vaccines have shown tremendous success with PZP vaccines taking the lead. Novel technologies and targets are being developed to improve existing vaccines and generate second-generation CVs. Single-shot vaccines, which can be delivered remotely, will greatly advance the field of immunocontraception for animal use with potential human application.

Immunization against GnRH in the male camel (Camelus dromedarius): effects on sexual behavior, testicular volume, semen characteristics and serum testosterone concentrations

The effect of immunization against gonadotrophin releasing hormone (GnRH) on sexual behavior, total scrotal size, semen characteristics and serum concentrations of testosterone, was evaluated for 24 wks in sexually mature camels (Camelus dromedarius). Eight bull camels were randomly divided into a treatment and control group. Four male camels were immunized using 2 mg GnRH - tandem-dimer conjugated to ovalbumin, (Pepscan Systems, the Netherlands) administered subcutaneously, 4 wks apart. Control male camels received the same amount of saline solution. Significant decline in serum testosterone level was observed in three immunized camels out of four, whereas one camel showed no effect. The testosterone levels reached to <1.0 ng/mL serum by week 4 after booster injection and remained suppressed through the course of the study. The total testicular volume was not affected until the end of the experiment. In treated animals, the sexual behavior negatively affected after the booster injection. Anti-GnRH vaccine had a seriously detrimental effect on the acrosin amidase activity and normal acrosome percentages in treated male camels. It is concluded that the vaccine was effective in reducing serum testosterone levels and libido, and it had a serious harmful effect on the acrosin amidase activity and percentages of spermatozoa with normal acrosome. The immunogen did not affect the total testicular volume.

Vaccination against gonadotropin-releasing factor (GnRF) with Bopriva significantly decreases testicular development, serum testosterone levels and physical activity in pubertal bulls

The aim of this study was to evaluate the effects of vaccination against gonadotropin-releasing factor (GnRF) on testicular development, testosterone secretion, and physical activity in pubertal bulls. The experiment was performed using 44 bulls aged between 6 and 7 mo. Twenty-three animals were vaccinated twice 4 wk apart with 1 mL of Bopriva (Pfizer, Animal Health, Parkville, Australia) and 21 bulls served as matched controls. Serum GnRF antibody titer and testosterone concentration as well as body weight and scrotal circumference were determined in all bulls for 24 wk from the first vaccination. In addition, physical activity was analyzed in 11 vaccinated and in 10 control animals using the ALPRO DeLaval activity meter system (DeLaval AG, Sursee, Switzerland). The results show that vaccination significantly (P < 0.05) influenced all parameters evaluated except body weight. Antibody titers to GnRF began to rise 2 wk after the first vaccination and reached peak values 2 wk after the second injection. Significant group differences in anti-GnRF titer were present for 22 wk following the first vaccination. Testosterone concentrations were significantly lower between weeks 6 to 24 after first vaccination in bulls with Bopriva compared with control animals. In vaccinated bulls testicular development was impaired after the second injection and scrotal circumference was significantly smaller between weeks 8 to 24 after first vaccination. Physical activity of vaccinated bulls was reduced after the booster injection with significant group differences for a continuous period of 106 days. In conclusion, vaccination against GnRF with Bopriva in pubertal bulls decreased testosterone levels in peripheral blood, testicular development, and physical activity but did not affect weight gain.

Pharmacological and toxicological assessment of a potential GnRH vaccine in young-adult male pigs

Active immunization against gonadotrophin-releasing hormone (GnRH) is successfully applied to prevent boar taint in pork. In men, GnRH immunization could be an alternative to hormone therapy in patients with prostate cancer. In this study, a new GnRH vaccine formulation (a modified GnRH peptide conjugate formulated with CoVaccine adjuvant) was investigated for its pharmacological efficacy and safety in young-adult male pigs. Immunization resulted in castrate-like plasma testosterone levels in all treated pigs from week 8 until the end of the study, 30 weeks after the first immunization. Testosterone depletion retarded testes growth, reduced the relative weight of the testes and accessory sex organs, and reduced sperm counts and motility. There was no clinically relevant toxicity. Typical vaccination-related adverse reactions, such as swelling at the injection site and fever, were considered acceptable. We conclude that this GnRH vaccine efficiently and rapidly reduced serum testosterone levels, without inducing chronic toxic effects, and therefore could be applicable in both veterinary and human medicine.

Feasibility of single-shot H5N1 influenza vaccine in ferrets, macaques and rabbits

The feasibility of a single-shot, low-dose vaccination against pandemic influenza was investigated. The immunogenicity and safety of whole inactivated, cell culture-derived H5N1 virus plus CoVaccine HT™ as adjuvant was tested in various animal species. In ferrets, doses of 4.0 and 7.5 μg H5N1 (NIBRG-14; A/Vietnam/1194/04; clade 1) without adjuvant gave low geometric mean haemagglutination inhibition (HI) titres (GMTs) of 21-65 three weeks after intramuscular (IM) injection. The addition of 0.25-4 mg CoVaccine HT™ resulted in GMTs of 255-1470 corresponding with 4-25-fold increases. A second immunization caused GMTs of 8914-23,525 two weeks later, which confirmed strong priming. One out of 8 ferrets injected with antigen alone and 5 out of 32 ferrets injected with adjuvanted H5N1 demonstrated minimal transient, local reactions and two animals immunized with adjuvanted H5N1 exhibited increased body temperature one day after injection. In macaques, 5 μg H5N1 with CoVaccine HT™ or aluminium hydroxide as adjuvant elicited GMTs of 172 and 11, respectively three weeks later. A second immunization resulted in GMTs of 1751 and 123, respectively four weeks later. Analysis of cross-reactivity of antibodies after the first immunization with NIBRG-14 adjuvanted plus CoVaccine HT™ revealed GMTs of 69 against NIBRG-23 (A/turkey/Turkey/1/05; clade 2.2) and 42 against IBCDC-RG-2 (A/Indonesia/5/05-like; clade 2.1.3) while titres with aluminium hydroxide were <10. After the second immunization with CoVaccine HT™, GMT against NIBRG-23 was 599 and against IBCDC-RG-2 254, while those with aluminium hydroxide were 23 and 13, respectively. No local or systemic adverse events were detected in macaques. Safety of 5 μg H5N1 plus 0, 2 or 4 mg CoVaccine HT™ was investigated in a repeated dose study in rabbits. Groups of 6 or 9 male and female animals were immunized IM three times at three week intervals. None of the animals exerted treatment-related adverse reactions during the study or at necropsy 3 or 4 days after treatment. We concluded that a low dose of whole inactivated influenza virus plus CoVaccine HT™ is a promising, single-shot vaccine against pandemic influenza.

A single immunization with CoVaccine HT-adjuvanted H5N1 influenza virus vaccine induces protective cellular and humoral immune responses in ferrets

Highly pathogenic avian influenza A viruses of the H5N1 subtype continue to circulate in poultry, and zoonotic transmissions are reported frequently. Since a pandemic caused by these highly pathogenic viruses is still feared, there is interest in the development of influenza A/H5N1 virus vaccines that can protect humans against infection, preferably after a single vaccination with a low dose of antigen. Here we describe the induction of humoral and cellular immune responses in ferrets after vaccination with a cell culture-derived whole inactivated influenza A virus vaccine in combination with the novel adjuvant CoVaccine HT. The addition of CoVaccine HT to the influenza A virus vaccine increased antibody responses to homologous and heterologous influenza A/H5N1 viruses and increased virus-specific cell-mediated immune responses. Ferrets vaccinated once with a whole-virus equivalent of 3.8 microg hemagglutinin (HA) and CoVaccine HT were protected against homologous challenge infection with influenza virus A/VN/1194/04. Furthermore, ferrets vaccinated once with the same vaccine/adjuvant combination were partially protected against infection with a heterologous virus derived from clade 2.1 of H5N1 influenza viruses. Thus, the use of the novel adjuvant CoVaccine HT with cell culture-derived inactivated influenza A/H5N1 virus antigen is a promising and dose-sparing vaccine approach warranting further clinical evaluation.

The novel adjuvant CoVaccineHT increases the immunogenicity of cell-culture derived influenza A/H5N1 vaccine and induces the maturation of murine and human dendritic cells in vitro

A candidate influenza H5N1 vaccine based on cell-culture-derived whole inactivated virus and the novel adjuvant CoVaccineHT was evaluated in vitro and in vivo. To this end, mice were vaccinated with the whole inactivated influenza A/H5N1 virus vaccine with and without CoVaccineHT and virus-specific antibody and cellular immune responses were assessed. The addition of CoVaccineHT increased virus specific primary and secondary antibody responses against the homologous and an antigenically distinct heterologous influenza A/H5N1 strain. The superior antibody responses induced with the CoVaccineHT-adjuvanted vaccine correlated with the magnitude of the virus-specific CD4+ T helper cell responses. CoVaccineHT did not have an effect on the magnitude of the CD8+ T cell response. In vitro, CoVaccineHT upregulated the expression of co-stimulatory molecules both on mouse and human dendritic cells and induced the secretion of pro-inflammatory cytokines TNF-alpha, IL-6, IL-1beta and IL-12p70 in mouse- and IL-6 in human dendritic cells. Inhibition experiments indicated that the effect of CoVaccineHT is mediated through TLR4 signaling. These data suggest that CoVaccineHT also will increase the immunogenicity of an influenza A/H5N1 vaccine in humans.

Evaluation of 'Section-Ligation-Release (SLR)' technique devised for castration in the stallion

A novel technique [Section-Ligation-Release (SLR)] was evaluated for castration in the horse. Clinical traits, serum testosterone concentrations after challenge with human chorionic gonadotrophin (hCG), and histopathological changes of the testicular tissue were assessed. Five stallions, aged 24-48 months, were castrated using SLR technique under general anaesthesia. Both spermatic cords in each stallion were exposed at the scrotal neck by two 5-cm long incisions, followed by sharp dissection through the parietal vaginal tunic. Both vascular and non-vascular structures in the cords were triple clamped, transected and ligated. Both testes were left in situ. Serum testosterone concentrations were measured pre-operatively and at 2 months after castration following IV administration of 1 x 10(4) IU of hCG. Both testes from each castrate were collected at 2 months for histopathologic examination. SLR castration was successfully achieved. Moderated scrotal and preputial swelling was the only experienced short-term complication. Serum testosterone concentrations were significantly lower than basal pre-operative levels at 2 months after castration, and did not respond to hCG. On histopathology, hyalinization of the seminiferous tubules and loss of testicular interstitial tissue were indicative of complete avascular necrosis. This novel primary closure castration technique of stallion is a simple practical method, with minimal post-operative complications; and could be safely advocated as an alternative to the traditional castration techniques allowing for second intention healing of scrotal wounds.

The use of a GnRH vaccine to suppress mare ovarian activity in a large group of mares under field conditions

The aim of this study was to evaluate the effect of active immunisation against GnRH on ovarian activity and serum progesterone concentrations in a large group of mares (10 control and 55 experimental) under field conditions as a model for wildlife species such as zebra and African elephants. Within the experimental group, mares were subdivided into three age categories: Category 1 (4 years and younger, n = 26), Category 2 (4–10 years old, n = 18), and Category 3 (≥11 years old, n = 11). Experimental mares were vaccinated intramuscularly with 2 mL (400 μg) of the GnRH vaccine Improvac (Pfizer Animal Health, Sandton, South Africa). Control mares received the same amount of saline solution. The vaccinations were repeated 35 days later. The ovaries and reproductive tracts of each mare were examined by means of rectal palpation and ultrasonography on Days 0, 35 and 70. Blood was collected weekly for determination of serum progesterone concentration until Day 175. On Day 35 after primary vaccination all of the control mares and 14.5% of the experimental mares showed evidence of ovarian activity on the basis of clinical examination and serum progesterone concentration. On Day 70, all control mares and none of the experimental mares showed evidence of cyclic activity. No age-related effect within treatment groups was found. The serum progesterone concentration indicated that all experimental mares remained in anoestrus until Day 175. Five of the control mares fell pregnant between Days 35 and 70. The five non-pregnant control mares continued to cycle until the end of the observation period. Having achieved such promising results in this trial we now plan to test the GnRH vaccine in Burchell’s zebra mares and African elephant cows.

Fertility control in wildlife: humans as a model

In a time of accelerated extinction rates and biodiversity loss, it may seem illogical to be concerned with methods limiting the reproduction of wild populations; however, there is an urgent need to inhibit the proliferation of a wide variety of species. The range of animals for which fertility control is desired makes the development of a single method impossible. The various reproductive strategies used by individual species, the desired outcome of contraceptive programs (reversible or irreversible; male or female directed) and our ignorance of the reproductive biology of many endangered species necessitate thorough species-specific investigations. As fertility control in humans is a reality and research into methods of fertility control is more advanced, humans serve as a model for developing contraceptive approaches for wild species. Population control by traditional methods (indirect or direct intervention by culling, poisoning, translocation, etc.) is increasingly unacceptable to the public, making human studies even more valuable for finding solutions to overabundant wild populations. This review compares and contrasts the range of contraceptive methods used in both wildlife and humans.

Modulating reproductive activity in stallions: A review

Situations in which suppression or stimulation of reproductive activity in stallions has been attempted, or is desired, include resolution of the equine arteritis virus 'shedding' state, induction of testicular descent in inguinal cryptorchids, and the improvement of sperm production capacity and/or semen quality in sub-fertile stallions. However, the most common reason for wanting to modulate reproductive activity in a stallion is to alter the expression of sexual behaviour. In the case of intact stallions used for competitive or recreational purposes, the overt expression of sexual or aggressive behaviour can be distracting for both animal and owner and, in some cases, dangerous to all concerned. By the same token, a breeding stallion that displays little interest in mounting a mare/phantom, or is slow to achieve erection and/or ejaculation, can be extremely frustrating. This paper reviews the major pharmacological agents reported to usefully modify reproductive activity in stallions, and outlines their pros and cons when compared to training, management or surgical alternatives.