Effects of the Immunocontraceptive Gonacon on Pregnancy in Brucella-Seropositive American bison (Bison bison).

The purpose of this study was to determine if the number of pregnancies in naturally infected Brucella abortus-positive bison (Bison bison) cows would be reduced over a period of 5 yr after one treatment with 3000 µg gonadotropin-releasing hormone immunocontraceptive (GonaCon) compared to a similar group of naturally infected B. abortus-positive bison cows not treated with GonaCon. In each of the 5 yr, GonaCon-treated cows produced fewer offspring in relation to number of cows than the nontreated cows. Fisher's Exact test comparing offspring produced during the first reproductive season showed a significant difference between the two groups (P=0.0028). Differences in number of calves produced in GonaCon-treated and control groups were also noted in remaining years, but statistics were not applied because of data constraints. These data indicate that one treatment with GonaCon in brucellosis-seropositive female bison reduced pregnancies over five reproductive years. Thus, immunocontraception could potentially be used to manage brucellosis in affected herds.

Evaluation of antibody response to an adjuvanted hapten-protein vaccine as a potential inhibitor of sexual maturation for farmed Atlantic salmon.

An experimental contraceptive vaccine was evaluated in Atlantic salmon (Salmo salar). A peptide derived from the beta subunit of luteinizing hormone (LH) was conjugated to two different carrier proteins, bovine serum albumin (BSA) and keyhole limpet hemocyanin (KLH), and formulated with one of four immunostimulants in a water-in-oil emulsion. Specific antibody responses to the peptide and each carrier protein were evaluated. While the antibody response to KLH was stronger than the response to BSA, both carrier proteins stimulated comparable antibody responses to the LH peptide. The immunostimulant proved to be more important for enhancing the LH peptide antibody response than the carrier protein selection; vaccines containing a combination of Aeromonas salmonicida and Vibrio anguillarum stimulated significantly greater LH peptide antibody production than any of the other three immunostimulants evaluated at 12 weeks post-vaccination. This study provides proof-of-concept for specific antibody production against a hapten-carrier protein antigen in Atlantic salmon and reinforces the importance of vaccine immunostimulant selection.

Nonsurgical fertility control for managing free-roaming dog populations: a review of products and criteria for field applications.

About 75% of dogs worldwide are free to roam and reproduce, thus creating locally overabundant populations. Problems caused by roaming dogs include diseases transmitted to livestock and humans, predation on livestock, attacks on humans, road traffic accidents, and nuisance behavior. Nonsurgical fertility control is increasingly advocated as more cost-effective than surgical sterilization to manage dog populations and their impact. The aims of this review were to 1) analyze trends in numbers of scientific publications on nonsurgical fertility control for dogs; 2) illustrate the spectrum of fertility inhibitors available for dogs; 3) examine how differences between confined and free-roaming dogs might affect the choice of fertility inhibitors to be used in dog population management; and 4) provide a framework of criteria to guide decisions regarding the use of nonsurgical fertility control for dog population management. The results showed that the 117 articles published between 1982 and 2011 focussed on long-term hormonal contraceptives, such as gonadotropin-releasing hormone agonists, immunocontraceptives, and male chemical sterilants. The number of articles published biennially increased from one to five papers produced in the early 1980s to 10 to 20 in the past decade. Differences between confined dogs and free-roaming dogs include reproduction and survival as well as social expectations regarding the duration of infertility, the costs of sterilization, and the responsibilities for meeting these costs. These differences are likely to dictate which fertility inhibitors will be used for confined or free-roaming dogs. The criteria regarding the use of fertility control for dog population management, presented as a decision tree, covered social acceptance, animal welfare, effectiveness, legal compliance, feasibility, and sustainability. The review concluded that the main challenges for the future are evaluating the feasibility, effectiveness, sustainability, and effects of mass nonsurgical sterilization campaigns on dog population size and impact as well as integrating nonsurgical fertility control with disease vaccination and public education programs.

Use of a GnRH vaccine, GonaCon, for prevention and treatment of adrenocortical disease (ACD) in domestic ferrets.

Adrenocortical disease (ACD) is a common problem in surgically sterilized, middle-aged to old ferrets (Mustela putorius furo). The adrenal tissues of these ferrets develop hyperplasia, adenomas, or adenocarcinomas, which produce steroid hormones including estradiol, 17-hydroxyprogesterone, and androstenedione. Major clinical signs attributable to overproduction of these hormones are alopecia (hair loss) in both sexes and a swollen vulva in females. Pruritus, muscle atrophy, hind limb weakness, and sexual activity or aggression are also observed in both sexes. Males can develop prostatic cysts, prostatitis, and urethral obstruction. ACD is thought to be linked to continuous and increased LH secretion, due to lack of gonadal hormone feedback in neutered ferrets. This continuous elevated LH acts on adrenal cortex LH receptors, resulting in adrenal hyperplasia or adrenal tumor. This study investigated whether the immunocontraceptive vaccine GonaCon, a GnRH vaccine developed to reduce the fertility of wildlife species and the spread of disease, could prevent or delay onset of ACD and treat alopecia in ferrets with existing ACD. Results showed that GonaCon provided relief from ACD by causing production of antibodies to GnRH, probably suppressing production and/or release of LH. Treatment caused many ACD symptoms to disappear, allowing the ferrets to return to a normal life. The study also found that the probability of developing ACD was significantly reduced in ferrets treated with GonaCon when young (1-3 years old) compared to untreated control animals. GonaCon caused injection site reaction in some animals when administered as an intramuscular injection but caused few side effects when administered subcutaneously. Both intramuscular and subcutaneous vaccination resulted in similar levels of GnRH antibody titers. Subcutaneous vaccination with GonaCon is thus recommended to prevent the onset of ACD and as a possible treatment for ACD-signs in domestic ferrets.

Concomitant administration of GonaCon™ and rabies vaccine in female dogs (Canis familiaris) in Mexico.

Mexico serves as a global model for advances in rabies prevention and control in dogs. The Mexican Ministry of Health (MMH) annual application of approximately 16 million doses of parenteral rabies vaccine has resulted in significant reductions in canine rabies during the past 20 years. One collateral parameter of rabies programs is dog population management. Enhanced public awareness is critical to reinforce responsible pet ownership. Surgical spaying and neutering remain important to prevent reproduction, but are impractical for achieving dog population management goals. GonaCon™, an anti-gonadotropin releasing hormone (GnRH) vaccine, was initially tested in captive female dogs on the Navajo Nation, 2008. The MMH led this international collaborative study on an improved formulation of GonaCon™ in captive dogs with local representatives in Hidalgo, Mexico in 2011. This study contained 20 bitches assigned to Group A (6 control), Group B (7 GonaCon™), and Group C (7 GonaCon™ and rabies vaccine). Vaccines were delivered IM. Animals were placed under observation and evaluated during the 61-day trial. Clinically, all dogs behaved normally. No limping or prostration was observed, in spite of minor muscle atrophy post-mortem in the left hind leg of dogs that received GonaCon™. Two dogs that began the study pregnant give birth to healthy pups. Dogs that received a GonaCon™ injection had macro and microscopic lesions consistent with prior findings, but the adverse injection effects were less frequent and lower in intensity. Both vaccines were immunogenic based on significant increases in rabies virus neutralizing antibodies and anti-GnRH antibodies in treatment Groups B and C. Simultaneous administration of GonaCon™ and rabies vaccine in Group C did not affect immunogenicity. Progesterone was suppressed significantly in comparison to controls. Future studies that monitor fertility through multiple breeding cycles represent a research need to determine the value of integrating this vaccine into dog rabies management.

Immunization with a synthetic peptide vaccine fails to protect mule deer (Odocoileus hemionus) from chronic wasting disease.

Chronic wasting disease (CWD) adversely affects both wild and captive cervid populations. A vaccine to prevent CWD would be a highly desirable tool to aid in disease management. To this end, we tested in mule deer a combination of CWD vaccines consisting of cervid prion peptide sequences 168-VDQYNNQNTFVHDC-182 and 145-NDYEDRYYRENMYRYPNQ-164 that had previously been shown to delay onset of clinical disease and increase survival in a mouse-adapted scrapie model. Thirteen captive mule deer (Odocoileus hemionus) were divided into vaccine (n=7) and control groups (n=6), and given prime and boost vaccinations intramuscularly 5 wk apart. Eight weeks postprime (3 wk postboost), all animals were challenged via natural exposure to an environment contaminated with infective CWD prions. Deer were monitored intermittently for prion infection by rectal and tonsil biopsies beginning 275 days postchallenge. All vaccinates responded to both peptide conjugates present in the combination vaccine as measured by enzyme-linked immunosorbent assay. However, all deer eventually became infected regardless of vaccine status.

Twenty years of immunocontraceptive research: lessons learned.

The National Wildlife Research Center (NWRC) began immunocontraception vaccine research by testing porcine zona pellucida (PZP) on white-tailed deer (Odocoileus virginianus). Early PZP research demonstrated that PZP induced infertility; however, increased length of the rut was observed in PZP-treated deer. An alternative vaccine using a keyhole limpet hemocyanin-gonadotropin-releasing hormone (KLH-GnRH) conjugate formulated with modified Freund's adjuvant was developed at NWRC. Suppression of GnRH has reduced reproduction in both sexes but is most effective in females. This vaccine was effective in preventing contraception in female deer for several years after a prime and boost. Due to adverse side effects of Freund's adjuvant, NWRC developed a new adjuvant called AdjuVac, a mineral oil/surfactant adjuvant with the addition of Mycobacterium avium as an immunostimulant. The price of KLH prompted a search for a more economical hemocyanin carrier protein for the GnRH peptide. Blue protein, derived from the mollusk Concholepas concholepas, proved to be a successful option. Formulation improvements resulted in a vaccine that can be effective as a single injection for multiple years, now called GonaCon. GonaCon is registered with the Environmental Protection Agency (EPA) for use in white-tailed deer in urban/suburban areas and for wild horses (Equus caballus) and burros (Equus asinus). Future GonaCon applications may include reducing reproduction to manage populations of other wildlife species, such as prairie dogs (Cynomys ludovicianus) in urban areas and suppressing reproduction to reduce the spread of venereal diseases such as brucellosis. Research is being conducted to develop a GnRH vaccine used in combination with the rabies vaccine to control population growth in free-roaming dogs, with the secondary effect of managing the spread of rabies. The EPA would regulate all these uses. Research is also ongoing on a GnRH vaccine to delay the onset of adrenocortical disease in pet ferrets (Mustela putorius), a use regulated by the United States Department of Agriculture.

The use of contraception as a disease management tool in wildlife.

Contraception offers potential as a tool for managing certain diseases in wildlife, most notably venereally transmitted diseases or diseases transmitted at parturition. Brucellosis is an excellent example of an infectious disease present in wild populations that could potentially be managed through immunocontraception. Previous studies in bison (Bison bison) suggest that a single injection of GonaCon (National Wildlife Research Center, U.S. Department of Agriculture/Animal and Plant Health Inspection Service/Wildlife Services, Fort Collins, Colorado 80521, USA) results in 3 or more yr of infertility. Ongoing studies will determine if the use of GonaCon in bison decreases shedding of Brucella abortus from infected animals and will better define the duration of infertility following a single injection

Immunocontraception in Eastern gray squirrels (Sciurus carolinensis): morphologic changes in reproductive organs.

Eastern gray squirrels (EGS) (Sciurus carolinensis) damage trees through bark stripping or gnawing due to territorial marking or agonistic gnawing behavior in concert with higher densities. This study was conducted to determine the effects of a contraceptive vaccine on EGS and its reproductive organ histology. Free-ranging urban EGS were vaccinated with the immunocontraceptive GonaCon. All EGS were > or = 6 mo of age as determined by a combination of pelage characteristics and body weights. The vaccine was administered by injection at a dosage rate of 0.4 ml containing 400 microg of GnRH-mollusk protein conjugate i.m. in the thigh to 33 EGS (17 male [m], 16 female [f]) in trapping session 1 (TS1), 23 (14 m, 9 f) in trapping session 2 (TS2), and 11 (8 m, 3 f) in trapping session 3 (TS3). A sham injection containing 0.4 ml saline-AdjuVac was given as control to 22 EGS (16 m, 6 f) in TS1, 20 (12 m, 8 f) in TS2, and 8 (4 m, 4 f) in TS3. In the last trapping session (TS4), 35 EGS (16 treated, 19 control) were killed for necropsy to evaluate histologic changes in testes and ovaries. Treated EGS males had testicular, prostatic, and epididymal atrophy compared with control EGS males. The tubuli seminiferi and prostatic glandular lumen of treated EGS males were atrophic, and the epididymal lumen contained no sperm cells. No histologic changes were observed in treated EGS females; however, females likely were not collected when changes due to GonaCon would have been observed. There were no observable histologic differences in the pituitary gland of treated and control EGS. There were no statistically significant differences in either testosterone or progesterone concentrations between control and treated EGS. Although there were no serious side effects to the vaccine, six EGS developed injection site abscesses. GonaCon may be a potential tool for EGS population control.

Long-term fertility control in female cats with GonaCon™, a GnRH immunocontraceptive.

The uncontrolled reproduction of free-roaming feral cats contributes to overpopulation and associated concerns regarding their welfare and impact on public health and the environment. Nonsurgical fertility control that could be administered to feral cats in the field would be a powerful tool for cat population control. The objective was to test the efficacy and duration of activity of a single-dose GnRH immunocontraceptive vaccine (GonaCon™) on the fertility of adult female laboratory cats. Vaccinated cats (n = 15) received a single injection of vaccine containing a GnRH-KLH conjugate (200 µg) emulsified in a mycobacterial and oil adjuvant on study Day 0. Sham-treated cats (n = 5) received a single injection containing all vaccine components except the GnRH-KLH conjugate. A breeding trial started on study Day 120. Vaccinated cats had a longer time to conception (median 39.7 mo) compared to sham-treated cats (4.4 mo; P < 0.001). A total of 93% of vaccinated cats remained infertile for the first year following vaccination, whereas 73, 53, and 40% were infertile for 2, 3, and 4 y, respectively. At study termination (5 y after a single GnRH vaccine was administered), four cats (27%) remained infertile. The GnRH antibody titers declined more rapidly in short-term responding cats with < 2 y of infertility (n = 4), compared to long-term responding cats that experienced fertility control for >2 y (n = 11) (P < 0.05). Non-painful but persistent late-onset granulomatous injection site masses appeared 2 y after initial vaccination in five cats. We concluded that GnRH immunocontraception is an ideal candidate for further development for feral cat control.

Effect of GonaCon™ vaccine on black-tailed prairie dogs: immune response and health effects.

Management of prairie dogs in the past has included poisoning, fumigants, barriers, and relocation. Because of the diverse attitudes related to prairie dog management, nonlethal methods that allow the existence of prairie dogs but help minimize damage related to population growth need to be developed. GonaCon™ is an immunocontraceptive vaccine that elicits antibodies to native GnRH; this prevents the secretion of reproductive hormones necessary for sperm and oocyte production. Prairie dogs were vaccinated with 0.1, 0.2, or 0.4 mL of the GonaCon™ emulsion intramuscularly in the upper thigh containing 100, 200, or 400 µg GnRH conjugate, respectively. Control animals were vaccinated with 0.4 mL saline emulsion in the upper thigh. Blood samples (≤1 mL) were taken from the femoral vein once pretreatment and at 1, 2, 3, 4, 6, and 15 months post-vaccination. Age (adult or juvenile) did not affect immune response to GonaCon™. Antibody titers were higher in the 200 and 400 µL GonaCon™ groups than in the 100 µL group, and there was no difference between the 200 and 400 µL GonaCon™ groups. No adverse effects of GonaCon™ were noted on weight or blood chemistry parameters during the study. GonaCon™ will likely contracept prairie dogs for ≥1 year in the field using either 200 or 400 µg conjugate. GonaCon™ could be incorporated into management plans to help maintain prairie dog populations while reducing habitat degradation due to overpopulation.

Review of issues concerning the use of reproductive inhibitors, with particular emphasis on resolving human-wildlife conflicts in North America.

This manuscript provides an overview of past wildlife contraception efforts and discusses the current state of research. Two fertility control agents, an avian reproductive inhibitor containing the active ingredient nicarbazin and an immunocontraceptive vaccine, have received regulatory approval with the Environmental Protection Agency and are commercially available in the USA. OvoControl G Contraceptive Bait for Canada Geese and Ovo Control for pigeons are delivered as oral baits. An injectable immunocontraceptive vaccine (GonaCon Immunocontraceptive Vaccine) was registered with the Environmental Protection Agency for use in female white-tailed deer in September 2009. An injectable product (GonaCon Immunocontraceptive Vaccine) is registered for use in female white-tailed deer. Both products are labeled for use in urban/suburban areas where these species are overabundant. Several other compounds are currently being tested for use in wildlife in the USA, Europe, Australia and New Zealand that could have promise in the future. The development and use of reproductive inhibitors for resolving human-wildlife conflicts will depend on a number of factors, including meeting the requirements of regulatory agencies for use in the environment and on the biological and economical feasibility of their use. Use will also be dependent on health and safety issues and on public acceptance of the techniques.

No adverse effects of simultaneous vaccination with the immunocontraceptive GonaCon and a commercial rabies vaccine on rabies virus neutralizing antibody production in dogs.

Parenteral vaccination campaigns are integral to the elimination of canine rabies. To maximize herd immunity in dogs, immunocontraception provided at the time of rabies vaccination should reduce fecundity and dog abundance. GonaCon has been used successfully as an immunocontraceptive in a variety of mammals, and by inference, the dog would be an ideal candidate for testing. As an initial step in evaluating a combination-vaccination program, we assessed the effects of GonaCon on rabies virus neutralizing antibody production in dogs after administration of a veterinary rabies vaccine. Eighteen feral/free ranging dogs were included in this initial study: six were given GonaCon only, six were given rabies vaccination only, and six received GonaCon and rabies vaccination. Antibody levels were evaluated over 82 days. The use of the immunocontraceptive GonaCon did not affect the ability of dogs to seroconvert in response to the rabies vaccine. Thus, GonaCon provides a potential immunocontraceptive for use in combination with rabies vaccine to increase herd immunity and address dog population over abundance to better manage rabies.

The single-shot GnRH immunocontraceptive vaccine (GonaCon) in white-tailed deer: comparison of several GnRH preparations.

PROBLEM: An effective, single-injection, multi-year, GnRH contraceptive agent is needed to control reproduction in overabundant white-tailed deer populations. METHOD OF STUDY: Two GnRH conjugates, GonaCon (GnRH-KLH) and GonaCon-B (GnRH-blue protein), were prepared in emulsion form as one-injection and two-injection immunocontraceptive vaccine formulations. In addition, the GnRH-KLH protein conjugate was lyophilized and suspended in AdjuVac adjuvant to produce a fifth vaccine formulation. Each formulation was administered to a group of five captive adult female white-tailed deer. Reproductive performance of treated female deer was monitored for 5 years to determine the comparative efficacy of the various treatments. RESULTS: The longevity of the contraceptive response (2-5 years) was strongly influenced by the design of the conjugate antigen, the adjuvant used, and the delivery form of the vaccine. CONCLUSION: One-injection and two-injection formulations of GonaCon and GonaCon-B produced multi-year contraception in adult female white-tailed deer. GonaCon-B provided a longer lasting contraceptive effect.

Comparison of immune and adverse effects induced by AdjuVac and Freund's complete adjuvant in New Zealand white rabbits (Oryctolagus cuniculus).

Though Freund's complete adjuvant effectively increases immune response to vaccines in various species, its potentially severe inflammatory effects have led many animal researchers to seek alternative immunological adjuvants. In a study of New Zealand white rabbits, the authors compared the immune and adverse effects of Freund's complete adjuvant with the effects of two formulations of AdjuVac, an immunological adjuvant previously developed by their group. All three adjuvants improved humoral immune response but also caused inflammation. Inflammatory reactions caused by AdjuVac, however, tended to be less severe than those caused by Freund's complete adjuvant.

Pathophysiology of white-tailed deer vaccinated with porcine zona pellucida immunocontraceptive.

White-tailed deer (n=14 treated, n=7 control) were examined postmortem to identify any possible pathophysiology resulting from PZP immunocontraception vaccination. Deer were treated twice in 1997; given a booster in 1998, with six being revaccinated in September 2000. Granulomas were found at injection sites of most deer, even 2 years post-treatment. Eosinophilic oophoritis occurred in 6 of 8 (75%) deer vaccinated in 1998, and 3 of 6 (50%) revaccinated in 2000. The 2000 revaccinates without oophoritis, had significantly fewer normal secondary follicles than control females (P=0.03), and deer in the 1998 treatment group (P=0.04). PZP immunocontraceptive vaccine elicited ovarian pathologies in deer similar to those observed in other species.

GnRH immunocontraception of male cats.

The development of nonsurgical contraceptives for cats may facilitate population control of the species. The purpose of this study was to investigate the utility of GnRH for immunocontraception of male cats. Male cats (n=12) were divided into groups of three and were immunized once with 0 (sham), 50, 200, or 400 microg synthetic GnRH coupled to keyhole limpet hemocyanin and combined with a mycobacterial adjuvant to enhance immunogenicity. GnRH antibody titer, serum testosterone concentration, and scrotal size were determined monthly. At 6 months, semen was collected by electroejaculation and testes were examined histologically. GnRH antibodies were detected in all cats receiving GnRH vaccine by 1 month post-treatment and persisted throughout the study. No dose effect of GnRH was observed; titers were not different among cats treated with 50, 200, or 400 microg GnRH (P=0.5). Six of nine treated cats were classified as responders based on high GnRH antibody titers (>32,000). By 3 months post-treatment, responder cats had undetectable testosterone concentrations and testicular atrophy. Nonresponder cats had GnRH titers of 4000-32,000 and testosterone concentrations intermediate between responder and sham-treated cats. At 6 months, total sperm counts were similar for sham-treated cats (3.1+/-1.8 x 10(6) sperm) and nonresponder cats (3.4+/-1.6 x 10(6) sperm; P=0.7). Only one of the six responder cats produced sperm, none of which were motile. Combined testicular weights of responder cats (1.3+/-0.1 g) were lower than sham-treated controls (5.3+/-1.3 g; P=0.02) and nonresponder cats (2.9+/-0.3 g; P=0.02). Histologic evaluation of the testes revealed that in responder cats, the interstitial cells that were present were pale and shrunken compared to the plump, polyhedral eosinophilic cells in sham-treated cats. GnRH responder cats had marked tubular atrophy with vacuolated Sertoli cells and a paucity of germ cells. Single-dose GnRH treatment resulted in testosterone concentrations and semen quality consistent with immunocastration in a majority of cats treated.

Contraception of bison by GnRH vaccine: a possible means of decreasing transmission of brucellosis in bison.

Preventing pregnancy in brucellosis-infected bison (Bison bison) provides a potential means of preventing transmission of disease. To determine whether a gonadotropin-releasing hormone (GnRH) vaccine was effective in reducing pregnancy in bison and to study the safety of injecting GnRH in pregnant bison, a study was conducted at the Idaho Fish and Game Wildlife Health Laboratory in Caldwell, Idaho (USA). Four pregnant and two nonpregnant female bison were given a single injection of GnRH vaccine, and five pregnant adult females were given a sham injection that contained only adjuvant. Three of the GnRH-vaccinated bison that were pregnant at the time of vaccination delivered healthy calves. One treated bison had dystocia that resulted in a dead calf. All control bison delivered healthy calves. After calving, females of both groups were exposed to two bulls. Treated bison were palpated 6 wk after exposure to the bulls, and blood was drawn for pregnancy-specific protein B analysis. The six treated bison were not pregnant. The sham-treated bison became pregnant and delivered viable calves. This study demonstrates that a single dose of GnRH vaccine is effective in preventing pregnancy in female bison for at least 1 yr.

Desmosterol: a biomarker for the efficient development of 20,25-diazacholesterol as a contraceptive for pest wildlife.

20,25-Diazacholesterol is being evaluated as a contraceptive for the nonlethal control of avian and mammalian wildlife pests. The identification of an analyte in blood which was highly correlated with absorbed dose and efficacy is valuable for determining effective formulations and dosing variables. Such an analyte or biomarker is also valuable for determining the percentage of pest populations that consume an effective dose of the active ingredient in the field. HPLC analyses of blood collected from dosed animals failed to detect 20,25-diazacholesterol but indicated that levels of free cholesterol and related compounds were affected by 20,25-diazacholesterol absorption. The greatest percent change in chromatographic peak area associated with 20,25-diazacholesterol administration was observed for desmosterol, a cholesterol precursor. 20,25-Diazacholesterol appeared to block the conversion of desmosterol to cholesterol, resulting in an elevated concentration of the precursor. The elevation of blood desmosterol levels is being used as an indicator of 20,25-diazacholesterol absorption and to facilitate the development of a 20,25-diazacholesterol-based contraceptive for pest wildlife.

In search of the active PZP epitope in white-tailed deer immunocontraception.

Native porcine zona pellucida (PZP) has been shown to be highly effective as an immunocontraceptive in white-tailed deer. However, the immunogenicity of PZP extracted from pig ovaries may vary from lot to lot and the extract has the potential of containing either viral or pathogenic material. Determination of the immunocontraceptive epitopes of PZP would allow portions of the molecule to be synthesized or inserted into a recombinant system for production of a consistent and safe vaccine. In this study, epitopes of PZP were selected and tested by in vitro binding, immunogenicity in rabbits, immunogenicity and immunocontraception in deer. Sera from PZP immunocontracepted deer were tested on ELISA plates containing immobilized peptides from ZP1 and ZP3alpha. Peptides with which sera from infertile deer reacted (six peptides from ZP1 and six peptides from ZP3alpha) were selected, synthesized and tested for immunogenicity in rabbits. Deer were then immunized with combinations of peptides from either the ZP1 or ZP3alpha groups. ZP3alpha peptides induced high immune titers against native PZP, but did not induce infertility in the deer. Although ZP1 peptides induced lower titers, deer immunized with two ZP1 peptides exhibited multiple estrus events and infertility, typical of that for deer immunized with native PZP vaccine. Competitive inhibition assays using the ZP1 peptides demonstrated that the peptide comprising pins 10-16 was most effective in blocking binding by the serum antibody of native PZP immunized deer. This peptide was used to immunocontracept deer, resulting in a significant reduction in fawning for 1 year.