Growth performance of immunologically castrated pigs slaughtered at 5, 7, or 9 weeks after the second Improvest dose and fed diets containing corn dried distillers grains with solubles

Growth performance of immunologically castrated (IC) pigs (863 total) was determined at increasing time intervals between the second Improvest (gonadotropin releasing factor analog-diphtheria toxoid conjugate; Zoetis Inc., Florham Park, NJ) dose and slaughter (TD) and with 4 different dried distillers grains with solubles (DDGS) feeding strategies (FS) in a 4 × 3 factorial arrangement of treatments. The feeding period was divided into 4 separate diet phases. Dietary treatments included 1) corn-soybean meal control diets (PCon), 2) a gradual decrease of dietary DDGS inclusion rate from 40%, 30%, 20%, and 10% in phases 1 to 4 (GD), respectively, 3) feeding 40% DDGS diets in phases 1 to 3 and removal of DDGS from the phase 4 diet (WD), and 4) feeding 40% DDGS diets in all 4 phases (NCon). Pigs received the second Improvest dose at 9 (TD9), 7 (TD7), or 5 (TD5) wk before slaughter. In each group, all pigs were slaughtered on the same day. There were no 3-way interactions among FS, TD, and week of feeding period for any measure of growth performance. Pigs fed PCon and WD had greater ( < 0.05) overall ADFI than pigs fed NCon, especially when slaughtered 9 wk after the second Improvest dose (2.45 and 2.44 vs. 2.31 ± 0.08 kg/d, respectively). This response was partly due to withdrawing DDGS from the diet at 19 wk of age (WD), which led to a tendency ( < 0.10) for increased ADFI from the wk 19 to 21 interval to the wk 21 to 24 interval (3.26 vs. 3.51 ± 0.09 kg/d, respectively). During the same time period, ADFI was unchanged ( > 0.05) in pigs fed PCon, GD, and NCon. Overall G:F was improved ( < 0.05) in TD5 pigs compared with TD9 pigs and tended ( < 0.10) to be improved compared with TD7 pigs. Final BW was similar among pigs fed GD, WD, and PCon (123.1, 122.3, and 125.3 kg, respectively), but pigs fed PCon and GD had greater ( < 0.05) BW than pigs fed NCon (120.0 kg). Throughout the growing-finishing period, BW was similar among TD treatments. The GD FS was more effective than the WD FS in maintaining overall G:F (0.424 and 0.414 ± 0.005, respectively) and ADG (0.94 and 0.93 ± 0.03 kg/d, respectively), which were similar ( > 0.05) to those of pigs fed PCon (0.427 ± 0.005 and 0.96 ± 0.03 kg/d, respectively). Growth performance of pigs fed GD more closely reflected that of pigs fed PCon than that of pigs fed WD. Delaying the second dose of Improvest from 9 to 5 wk before slaughter resulted in improved growth performance.

Vaccines for immunological control of fertility in animals

Fertility control has gained considerable momentum as a management tool to regulate populations of captive and wild animals and to control aggressive behaviour or improve meat quality in livestock. Anti-fertility vaccination (immunocontraception and immunocastration) is a humane alternative to methods that rely on surgical or chemical sterilisation and lethal control. Two types of experimental immunocontraceptive vaccine have been registered for field use in animals. They contain either porcine zona pellucida (PZP) proteins extracted from pig ovaries or synthetic conjugated gonadotrophin releasing hormone (GnRH) peptides. These vaccines require repeated injections and are limited to captive or small populations of free-ranging wild animals. Alternative immunocontraceptive vaccines are actively being developed either to improve efficacy or enable large numbers of wild animals to be targeted. Some employ live genetically modified viruses to deliver immunocontraception and have proved successful under laboratory conditions. The relative merits, risks, social acceptability and regulations controlling the use of existing and novel animal immunocontraceptives are reviewed.

[Advances in sperm membrane antigens]

A series of sperm membrane antigens, the important molecular markers associated with the program of spermatogenesis and maturation of sperm, which also are for attachment of the physiological mechanism of the sperm-egg interaction and fusion and the pathological changes in the infertility, were reviewed. Some traditional crucial sperm membrane proteins, such as FA-1, PH-20, fertilin, have been cloned and sequenced, and some novel gene which encode new proteins associated with the sperm membrane also have been screened out successively. All of these provided a basement for lucubration of these proteins and the research of the contraception vaccine.

Immunisation of male mice with a plasmid DNA vaccine encoding gonadotrophin releasing hormone (GnRH-I) and T-helper epitopes suppresses fertility in vivo

Immunisation against mammalian gonadotrophin releasing hormone (GnRH-I) linked to large carrier proteins has been shown to disrupt fertility. However, various studies have shown that the carrier protein causes epitope suppression of the hapten response, resulting in short-lived immunoneutralisation, followed by a return of fertility. A range of strategies has been used to resolve this, with limited success. The aim of this study was to construct a plasmid DNA vaccine encoding GnRH-I and T-helper epitopes. A 498 bp long vaccine construct in pcDNA3.1+ was administered to male mice in conjunction with a Hemagglutinating Virus of Japanese Envelop (HVJ-E) vector or in saline solution. The vaccine efficacy was evaluated in terms of GnRH-I specific IgG antibody response, serum testosterone levels, testicular spermatogenesis and the ability to produce offspring. The vaccine appeared to induce higher anti-GnRH-I IgG antibody response and insult the fertility axis, which was characterised by a drop of epididymal sperm counts, reduction of serum testosterone levels, suppressed testicular spermatogenesis and a significant decrease in litter numbers compared to control animals. The end-point vaccine efficacy was much higher in the HVJ-E vector mediated immunisation, than in saline alone.

[Advances in the studies of epididymal protease inhibitor--Eppin]

The epididymal protease inhibitor (Eppin) abounds in human semen and on the surface of human spermatozoa, specifically produced by the testis and epididymis. Recombinant Eppin has effected infertility in the immunized monkey and promises to be an effective vaccine for human immunocontraception. This article reviews the advances in the studies of Eppin gene and protein construction and its molecular mechanism of causing immunologic infertility and regulating PSA hydrolysis of Semenogelin.

Feasibility and challenges in the development of immunocontraceptive vaccine based on zona pellucida glycoproteins

The zona pellucida (ZP) glycoproteins play a crucial role during fertilization and thus are considered as important target antigens for the development of immunocontraceptive vaccines aiming to inhibit fertility at a pre-fertilization stage. In order to evaluate the immunocontraceptive potential of ZP glycoproteins, bonnet monkey (Macaca radiata) ZP2, ZP3 and ZP4 have been cloned and expressed using either E. coli or baculovirus expression systems. Active immunization studies with the recombinant ZP glycoproteins in female baboons (Papio anubis) and bonnet monkeys revealed curtailment of fertility. In order to minimize the ovarian pathology, synthetic peptides corresponding to B cell epitopes that are devoid of 'oophoritogenic' T cell epitopes were designed and their in vitro immunocontraceptive potential explored. There are several issues that need to be addressed before ZP glycoproteins based immunocontraceptive vaccines become feasible for use in humans. Nonetheless, the utility of such a vaccine is imminent for controlling wild life population. In this direction, active immunization of female non-descript dogs with recombinant canine ZP3 conjugated to diphtheria toxoid led to curtailment of fertility. Further, canine ZP3 has also been expressed in insect cells as a fusion protein with rabies virus glycoprotein G (RV-G), an antigen that is involved in providing protection against rabies. The immunogenicity of such a recombinant protein and its potential to curtail fertility was explored both in female mice and dogs. Simultaneously, DNA vaccine encoding canine ZP3 and RV-G have been made and evaluated for their immunogenicity. The results obtained so far, current shortcomings and the possible ways to circumvent these have been discussed in the present manuscript.

Peptide vaccines against cancer, infectious diseases, and conception

The concept of peptide vaccines is based on identification and chemical synthesis of B-cell and T-cell epitopes which are immunodominant and can induce specific immune responses. B-cell epitope of a target molecule can be coupled to a promiscuous T-cell epitope to make it immunogenic. Our increased understanding of antigen recognition at molecular level has resulted in the development of rationally designed peptide vaccines. The relative ease of construction and production, chemical stability, and lack of oncogenic or infectious potential has made the peptides attractive vaccine candidates. However, several obstacles limit the widespread usefulness of peptide vaccines. These include their low immunogenicity, need for a better adjuvant and carrier, and reliable and simple assays to measure T-cell response. Nonetheless, current efforts are defying these limitations and many promising discoveries are making their way to improve this approach. The peptide vaccines against various cancers have undergone phase I and phase II clinical trials with successful immunological clinical outcome. The peptide vaccination is being examined both for palliative and prophylactic immunotherapy. The current status of many peptide vaccines which are being developed against cancer, infectious diseases, and conception is discussed in this review.

Effect of immunisation against gonadotrophin releasing hormone isoforms (mammalian GnRH-I, chicken GnRH-II and lamprey GnRH-III) on murine spermatogenesis

In mammals, the hypothalamic decapeptide, gonadotrophin releasing hormone (GnRH-I), is regarded as the major fertility regulating peptide. However, a range of isoforms also exists, varying only in the core region between amino acids 5-8. The physiological role of two of these, GnRH-II and GnRH-III, remains controversial, particularly with regard to fertility. The basis of the present study was to examine whether there is potential for GnRH-II and GnRH-III to be developed into highly specific vaccines, and to determine what the impact of their neutralisation would be on fertility. Computer modelling was used to predict how many common amino acids could be sequentially removed from the N-terminus, without loss of conformational structure. Sequences predicted to retain structure, were synthesised and conjugated to tetanus toxoid. Male mice were actively immunised, in study weeks 0, 2, 4 and 6 and peptide specific ELISA carried out. Mice immunised with TT-GnRH-I, TT-GnRH-II and TT-GnRH-III conjugates induced high antibody titres to the respective peptide. However, serum from TT-GnRH-I treated mice showed cross-reactivity to GnRH-II and GnRH-III peptides, and serum from TT-GnRH-II immunised mice showed cross-reactivity to GnRH-III. On the other hand, serum from only two of the TT-GnRH-III treated animals showed cross-reactivity to GnRH-II. Histological examination of the testes enabled comparative quantification of the disruption to spermatogenesis. Immunisation against TT-GnRH-I and TT-GnRH-III caused 66% and 68%, respectively, of seminiferous tubules viewed to show evidence of spermatogenesis, compared with 82% and 92% against TT-GnRH-II and untreated controls, respectively. Endocrine analysis revealed that only the TT-GnRH-I immunised animals showed significant reduction (p<0.05) in follicle stimulating hormone, while testosterone levels were reduced in the TT-GnRH-I and TT-GnRH-III treated animals. Taken together, our data suggests that GnRH-I and GnRH-III are implicated in spermatogenesis, unlike GnRH-II.

Immunocontraception in companion animals

There is real need worldwide to control the population growth of companion animals. Throughout the world and particularly in the United States, overpopulation of unwanted dogs and cats is a concern for many reasons. Feral populations pose risk to native species by spread of disease and predation. That unwanted animals are humanely eradicated is of concern to many persons. The need to control population growth has led to various approaches to contraception, including immunocontraception. Concerns regarding efficacy, duration of action, harm to the individual, and species specificity are among the issues being addressed. As new technologies emerge, ethical, political, and safety issues evoke differing opinions. It is hoped that in the near future, different strategies will be developed to solve this disturbing problem.

A COMPARISON OF FREUND'S COMPLETE AND FREUND'S MODIFIED ADJUVANTS USED WITH A CONTRACEPTIVE VACCINE IN WILD HORSES (EQUUS CABALLUS)

Fifteen captive wild mares (Equus caballus) were treated with porcine zona pellucida contraceptive vaccine and either Freund's Complete Adjuvant (n = 7) or Freund's Modified Adjuvant (n = 8). All mares received a booster inoculation of porcine zona pellucida plus Freund's Incomplete Adjuvant a month later. Anti-porcine zona pellucida antibodies were measured over 10 mo following the initial inoculation. There were no significant differences in antibody titers at any point during the 10 mo, and seven of the eight mares in the Freund's Modified Adjuvant group were above the 60% level at the end of the study, which is considered to be the contraceptive threshold for horses. There were no significant differences in titers between pregnant and nonpregnant horses, nor was there a significant correlation between age and titers. One local injection site reaction occurred after booster treatment with Freund's Incomplete Adjuvant, and 11 healthy foals were born during the course of the study. These data suggest that Freund's Modified Adjuvant is an acceptable substitute for Freund's Complete Adjuvant in certain free-ranging and captive wildlife species.

Identification of a New, Testis-Specific Sperm Antigen Localized on the Principal Piece of the Spermatozoa Tail in the Fox (Vulpes vulpes)1

Fox (Vulpes vulpes) sperm antigens were identified to assess them as a potential target for a contraceptive vaccine. We report here the cloning and sequencing of fSP13, a fox sperm protein of 97 kDa. The fSP13 protein was both auto- and iso-antigenic in foxes; it was recognized by sera of foxes immunized with fox sperm proteins and vasectomized foxes. The NH2-terminal sequence of fSP13 was determined, and a piece of cDNA was amplified from testicular RNA by reverse transcription polymerase chain reaction. This piece was used to screen a cDNA library from fox testis by Southern blot. A sequence of 1662 base pairs was obtained, including a major open reading frame coding for 498 amino acid. Mass spectrometry analysis confirmed the position of the open reading frame and the presence of posttranscriptional modifications. Analysis of the predicted amino acid sequence revealed no apparent transmembrane regions. Comparison of the protein sequence with the Prosite database demonstrated the presence of four potential N-linked glycosylation sites. The fSP13 bears the closest amino acid similarity to two human sperm proteins: fibrousheathin 2 and testis-specific calcium binding protein 86-VII. The deduced 80 N-terminal amino acid sequence also presents similarity with the RIIalpha domain. By using a serum against fSP13, this antigen was localized on the principal piece of the fox spermatozoa. Northern blot analysis showed that fSP13 is specifically expressed in testis. The fSP13 is one of the first fox sperm antigens to be cloned and sequenced.

Reversible immunocontraception in male monkeys immunized with eppin

Various forms of birth control have been developed for women; however, there are currently few options for men. The development of male contraceptives that are effective, safe, and reversible is desired for family planning throughout the world. We now report contraception of male nonhuman primates (Macaca radiata) immunized with Eppin, a testis/epididymis-specific protein. Seven out of nine males (78%) developed high titers to Eppin, and all of these high-titer monkeys were infertile. Five out of seven (71%) high-anti-Eppin titer males recovered fertility when immunization was stopped. This study demonstrates that effective and reversible male immunocontraception is an attainable goal. This method of immunocontraception may be extended to humans.

Molecular targets for immunocontraception

Effective contraception is necessary in countries where limiting population growth has become a public policy imperative. The main antigenic targets for contraceptive vaccine development can be listed as following: 1) sperm antigens, 2) zona pellucida antigens, 3) gonadotrophin-releasing hormone, 4) chorionic gonadotrophin, 5) other protein/peptide hormones (follicle-stimulating hormone, luteinizing hormone, luteinizing hormone-releasing hormone), and 6) gonadal steroid hormones. New techniques, such as the application of monoclonal antibodies, hybridoma and DNA recombinant technologies, have become useful in search for contraceptive candidates. Current state of development of contraceptive vaccines based on specific antigenic targets and trials in animal/human models are presented in this article.

Assessment of contraceptive vaccines based on recombinant mouse sperm protein PH20

Mouse PH20 (mPH20), the mouse homologue to guinea pig hyaluronidase protein PH20 (gpPH20), was used to produce contraceptive vaccines that target both sexes of mice. Previously, immunization with a female gamete antigen (the zona pellucida subunit 3 protein) delivered in a recombinant murine cytomegalovirus (MCMV), or as a purified recombinant protein, has been shown to induce infertility in female mice. There is evidence, however, that sperm protein antigens could provide broader contraceptive coverage by affecting both males and females, and the most promising has been gpPH20 when tested in a guinea pig model. Mice were therefore either inoculated with a recombinant MCMV expressing mPH20 or immunized directly with purified recombinant mPH20 protein fused to maltose-binding protein. Mice treated with either vaccine formulation developed serum antibodies that cross-reacted to a protein band of 55 kDa corresponding to mPH20 in Western blots of mouse sperm. However, there was no significant reduction in the fertility of males or females compared with control animals with either formulation. We conclude from our data that recombinant mPH20 is not a useful antigen for inclusion in immunocontraceptive vaccines that target mice.

Passive immunization for immunocontraception: lessons learned from infectious diseases

Development of vaccine for contraception is an exciting proposition that could provide a valuable alternative to the presently available methods for birth control. Various targets such as gonadotropin releasing hormone (GnRH), follicle stimulating hormone (FSH), leutinizing hormone (LH), zona pellucida (ZP) antigens, sperm antigens, and human chorionic gonadotropin (hCG) are being explored for immunocontraception. Besides specific concerns associated with each contraceptive vaccine, the progress has been restricted by the variability of the immune response after active immunization, attain and maintain high antibody titers, time lag to achieve reasonably good antibody titers, and uncertainty regarding how long the bioeffective antibodies will remain in circulation. It is envisaged that these concerns may be taken care of by using the preformed antibodies in the passive immunization approach. The antibody therapies have been tried and found to be successful against various infectious diseases both in animals as well as humans. Some have become treatment modalities in the clinics. This manuscript will review the data available for the passive immunization of preformed polyclonal and murine/humanized/human monoclonal antibodies, their efficacy, mode of delivery, duration of the effects, and limitations, if any. The overall objective is to examine the feasibility and practicability of the passive immunization approach for immunocontraception.

Contraceptive vaccines

The control of human fertility would be revolutionised by the development of a safe, effective, long-acting contraceptive vaccine. The pursuit of this objective has involved the selection of appropriate targets within the reproductive process that are amenable to interference with antibodies. To date, three major targets have been researched. The zona pellucida (ZP) plays key roles in folliculogenesis, fertilisation and early development, and is comprised of powerful cell-specific antigens. The induction of infertility requires high ZP antibody titres that are difficult to maintain without inducing ovarian pathology characterised by a premature loss of primordial follicles. As a premature menopause would be a high price to pay for long-term contraception, this approach to a vaccine cannot progress until the cause of the ovarian pathology has been resolved. Sperm surface antigens represent another promising approach to contraceptive vaccine development. While there is some clinical data to support the likely efficacy of this strategy, none of the gamete-specific molecules characterised to date have fulfilled this promise. Anti-human chorionic gonadotropin (hCG) vaccines terminate pregnancy by preventing the maternal recognition of pregnancy. This vaccine has reached the stage of clinical trials, and preliminary indications are that the approach is safe and potentially effective. However, reliability may be an issue, given the observed inter-individual variability in antibody generation. The future of contraceptive vaccine development will clearly involve a continuation of the intense search for suitable targets and the development of improved immunisation procedures that exploit the latest innovations in vaccine technology.

Zona pellucida glycoproteins based immunocontraceptive vaccines: strategies for development and their applications

The mammalian oocyte is surrounded by an extra-cellular matrix, the zona pellucida (ZP), composed of three major glycoproteins (ZP1, ZP2 and ZP3). The ZP glycoproteins, by virtue of their tissue specificity and critical role during mammalian fertilization, have emerged as potential candidate antigens for the development of an immunocontraceptive vaccine. Molecular characterization of ZP glycoproteins from several species, reveals a variable degree of homology among the deduced primary amino acid sequences, which provided an opportunity to undertake active immunization studies in heterologous animal models. Active immunization of various animal species with either native ZP glycoproteins or those obtained by recombinant DNA technology led to the inhibition of fertility. Thus ZP glycoproteins based immunocontraceptive vaccines offer an attractive proposition for controlling wild life population. To make it a practical proposition, additional research inputs are required to optimize and devise novel strategies for vaccine delivery. Observed ovarian dysfunction, often associated with immunization by ZP glycoproteins is one of the major stumbling blocks for their use in humans. Ongoing studies to delineate appropriate B cell epitopes of ZP glycoproteins that are devoid of oophoritogenic T-cell epitopes, which will inhibit fertility without concomitant oophoritis, will be critical to determine their feasibility for human use.

[Specific mucosal immunity in the female reproductive tract: protection against infectious diseases and regulation of fertility (part 2)]

Immune mediated defense against pathogenic microorganisms and maintenance of immune tolerance to allogeneic antigens of sperm and fetus are main function of female reproductive tract mucosal immune system. Specific mechanisms concerning development of mucosal vaccines to sexually transmitted diseases and the immune regulation of fertility are reviewed in this article.

Use of gamma-inulin/liposomes/Vitamin E adjuvant combination in contraceptive vaccines

The adjuvanticity of two gamma inulin/liposomes/Vitamin E combinations was evaluated in the mouse, in contraceptive vaccines with sperm protein extracts or a synthetic HE2 peptide ("Human Epididymis gene product"; residues 15-28) as antigen. The HE2 peptide was not conjugated to a protein carrier, to ensure that the antibodies elicited were specific against the HE2 peptide. The adjuvant combinations were designed to increase adjuvanticity, as their components have complementary mechanisms, and their performance was compared to Freund's adjuvant. Antibody production against native sperm structures was determined in sera by ELISA immunoassay and immunohistology. Toxicity of adjuvants was determined by histopathological study and treated mice were monitored for signs of pain or distress. Our results show that the gamma inulin (1-2 microm particle size)/liposomes/Vitamin E combination, with sperm protein extracts, is better than Freund's adjuvant because it elicits good antibody titres without any toxicity. When the synthetic HE2 peptide is used as antigen, the gamma inulin (1-2 microm particle size)/liposomes/Vitamin E combination is less effective than Freund's adjuvant; nevertheless, the anti-HE2 antibodies elicited are highly specific and recognize native structures in sperm.

Ecological basis for fertility control in the house mouse (Mus domesticus) using immunocontraceptive vaccines

Laboratory studies confirm the potential for fertility control in the house mouse Mus domesticus using mouse cytomegalovirus (MCMV) as a vector for an immunocontraceptive vaccine. This article presents an overview of key results from research in Australia on enclosed and field populations of mice and the associated epidemiology of MCMV. The virus is geographically widespread in Australia. It also persists in low population densities of mice, although if population densities are low for at least a year, transmission of the virus is sporadic until a population threshold of approximately 40 mice ha(-1) is reached. The serological prevalence of MCMV was high early in the breeding season of four field populations. Enclosure studies confirm that MCMV has minimal impact on the survival and breeding performance of mice and that it can be transmitted to most adults within 10-12 weeks. Other enclosure studies indicate that about two-thirds of females would need to be sterilized to provide effective control of the rate of growth of mouse populations. If this level is not maintained for 20-25 weeks after the commencement of breeding, the mouse population can compensate through increased recruitment per breeding female. The findings from this series of descriptive and manipulative population studies of mice support the contention that MCMV would be a good carrier for an immunocontraceptive vaccine required to sustain female sterility levels at or above 65%.

Analysis of a human sperm CD52 glycoform in primates: identification of an animal model for immunocontraceptive vaccine development

Sperm agglutination antigen-1 (SAGA-1) is a human male reproductive tract glycoform of CD52. Unique modification of CD52 N-linked oligosaccharide chains in the epididymis and vas deferens results in the appearance of a carbohydrate epitope that is localized over the entire surface of human spermatozoa. SAGA-1 was characterized by the sperm-inhibitory murine monoclonal antibody (mAb) S19, and it is the target antigen of a human mAb (H6-3C4) associated with antibody-mediated infertility. Collectively, sperm surface localization, antibody inhibition of sperm function, and potential reproductive-tissue specificity identify SAGA-1 as an attractive candidate contraceptive immunogen. To establish an animal model for the study of SAGA-1 in immunologic infertility and immunocontraceptive development, we investigated the appearance of the S19 carbohydrate epitope in nonhuman primates. The S19 mAb demonstrated little to no immunoreactivity by Western blot analysis with protein extracts of spermatozoa from the baboon, marmoset, bonnet, cynomolgus, and pigtailed macaques. Immunohistochemical analysis identified CD52 in the bonnet monkey epididymis; however, the N-linked carbohydrate moiety recognized by the S19 mAb, and unique to SAGA-1, was absent. In contrast, the S19 carbohydrate epitope was identified in chimpanzee sperm extracts by Western blot analysis and in chimpanzee epididymal tissue sections by immunohistochemical analysis, indicating that it is conserved in this close relative of the human. Chimpanzee testis, seminal vesicle, and prostate do not express the S19 epitope. Although anti-CD52 immunoreactivity was identified in the spleen, the carbohydrate moiety recognized by the S19 mAb was absent, corroborating data in the human that demonstrated tissue-specific glycosylation of sperm CD52. Immunofluorescent analysis indicated that the chimpanzee homologue of sperm CD52 was present over the entire spermatozoon. In addition, the S19 mAb agglutinated chimpanzee spermatozoa in a manner similar to the effect observed on human spermatozoa. These data indicate that the distinctive carbohydrate moiety of human sperm CD52 is present in the chimpanzee, and they identify the chimpanzee as the most appropriate primate model to study the potential of this unique CD52 glycoform as a contraceptive immunogen.

Future prospects for vaccines to control fertility

Vaccination is used routinely to protect against infectious disease and is being explored increasingly as a method of protection against tumors. Also, it has been established that vaccination using antigens associated with reproduction can protect against undesired pregnancy. Substantial progress over the past decade suggests that, if the remaining immunological and socioeconomic issues can be resolved, antifertility vaccines could be a valuable, additional method of family planning.

Influence of active immunization against GnRH on VIP- and NPY-positive innervation of the porcine testis

The influence of an anti-GnRH vaccine on VIP- and NPY-positive innervation of testes was studied in the pig. The immunization prevented the occurrence of changes in the pattern of VIP- and NPY-positive testicular innervation associated with the sexual maturation: it maintained the density of innervation at the high level characteristic for sexually immature animals. The effect was dependent on the method of immunization: the application of two doses of the vaccine was more efficient than application of only one dose, and vaccination with adjuvant was more efficient than vaccination with the plain vaccine. The studies on VIP and NPY concentration in the testicular tissue with radioimmunoassay (RIA) revealed immunization-dependent changes in the peptide concentration, however, some discrepancies between morphological changes and peptide levels were observed.

Life-style vaccines

Multiple immunotherapy approaches are under development to treat various chronic diseases or conditions. Thanks to dramatic technological improvements, the field of vaccinology can now extend from prophylaxis to therapy, and from infectious diseases to dysimmune disorders like cancer or autoimmunity, or even to non-immune related conditions, including neurological or cardiovascular disorders. Life-style vaccines defined as vaccines to manage chronic conditions in healthy individuals can, therefore, also be envisaged. Three examples will be reviewed and discussed here, from both technical and ethical aspects: contraceptive vaccines, vaccines to treat addictions, and anti-dental caries vaccines.

The role of follicle-stimulating hormone in spermatogenesis: lessons from knockout animal models

The development of knockout mouse models for the FSH-beta subunit, the FSH receptor, and LH-receptor performed in different laboratories has confirmed and extended our knowledge concerning the critical role of these hormone-signaling systems in spermatogenesis. In this article, we summarize the phenotypic changes observed in male FSH receptor knockout (FORKO) mice. Young FORKO males have underdeveloped testis with 50% reduction in Sertoli cells, suggesting that FSH-R signaling is required very early for gonadal development, maturity, and function. These mice experience delayed puberty with postponement in the formation of round spermatids. Adult males show reduction in serum testosterone levels despite normal circulating LH concentration, indicating disturbances in Sertoli-Leydig cell communication. As a consequence of reduced sperm production and sperm quality, adult FORKO males have reduced fertility. Aberrant sperm from FORKO males have retention of cytoplasmic droplets and inadequate DNA compaction, hallmarks of infertility in many species including man. Interestingly, these changes are also experimentally inducible in FSH- and/or FSH-R-immunized male bonnet monkeys, creating a state of infertility. Reports of human mutations in FSH-beta and the FSH receptor also indicate that spermatogenesis is dependent on this system. Further investigations in FORKO males should be helpful in uncovering the downstream genes involved in sustaining Sertoli cell function and maintenance of the quantitative and qualitative aspects of spermatogenesis. This might pave the way for treatment of male infertility and contraception.

Molecular mechanisms involved in mammalian gamete fusion

Fusion between gametes is a key event in the fertilization process involving the interaction of specific domains of the sperm and egg plasma membranes. During recent years, efforts have been made toward the identification of the specific molecular components involved in this event. The present work will focus on the best characterized candidates for mediating gamete membrane fusion in mammals. These molecules include members of the ADAM (a disintegrin and a metalloprotease domain) family, i.e., testicular proteins fertilin alpha, fertilin beta, and cyritestin, which are thought to interact with integrins in the egg plasma membrane through their disintegrin domains, and a member of the cysteine-rich secretory proteins (CRISP) family, i.e., epididymal protein DE, which participates in an event subsequent to sperm-egg binding and leading to fusion through specific complementary sites localized on the fusogenic area of the egg surface. The identification and characterization of these molecules will contribute not only to a better understanding of the molecular mechanisms underlying mammalian sperm-egg fusion but also to the development of new methods for both fertility regulation and diagnosis and treatment of human infertility.

Helix stabilization in the C-terminal peptide of chicken riboflavin carrier protein enhances immunogenicity and prolongs contraceptive potential as an epitope-based vaccine in female rats

Earlier investigations have shown that (a) antibodies against a carrier-coupled 20-residue synthetic peptide (C-20), (200)HACQKKLLKFEALQQEEGEE(219), corresponding to the C-terminal partially helical sequence of chicken riboflavin carrier protein (RCP; 219 AA) curtail pregnancy in mammals and (b) helix stabilization by introducing appropriately spaced salt bridges in the flanking sequences of its B-cell epitopic structure enhances RCP antigenicity to peptide antibodies. Among such engineered C-20 analogs, HE-20 (HAEQKKLLKFEALEQEKGKE) exhibited maximum helical propensity. Since C-20 per se, i.e., without carrier conjugation, elicits RCP-reactive neutralizing antibodies in rodents, we mapped its T-cell epitope which overlaps its B-cell epitope, both of which remain unmodified in HE-20. Comparative evaluation of immunogenicity of the two epitope-based peptide vaccines showed that HE-20 was far superior to C-20 in generating RCP-reactive antibodies in terms of both affinity and titer. With regard to bioefficacy, passive immunoneutralization of RCP in pregnant rats by administering purified IgG from either of the antipeptide sera terminated pregnancy. Similarly, active immunization of fertile female rats with the individual peptide analogs curtailed pregnancy. However, HE-20 was more efficient in eliciting higher affinity, longer-lasting, RCP-crossreactive antibodies with consequently more prolonged immunocontraceptive efficacy.

Blocking effect of antisera to recombinant zona pellucida proteins (r-ZPA) on in vitro fertilization

PROBLEM

The zona pellucida is a good target antigen for contraceptive vaccines due to its strong immunogenicity and high tissue specificity. However, this contraceptive effect is inevitably associated with ovarian failure. Therefore, it is necessary to define an epitope of the zona antigen to which the antibody produced inhibits fertilization without any undesirable side effects.

METHOD OF STUDY

The DNA fragment coding for the NH2-terminal region of porcine zona pellucida proteins (ZPA) (1-198 amino acids) and human ZPA (1-206 amino acids) was prepared to produce recombinant porcine ZPA (r-ZPA), r-pZPA1-198 and r-hZPA1-206. Using Freund's complete adjuvant. antisera against these proteins were raised in rabbits.

RESULTS

The resultant antisera to r-pZPA1-198 and r-hZPA1-206 were cross-reacted with each other on enzyme-linked immunosorbent assay and immunofluorescent staining. The antiserum to r-pZPA1-198 inhibited in vitro fertilization in pigs, but not human sperm binding to the zona pellucida, while the antiserum to r-hZPA1-206 inhibited the human sperm-binding assay.

CONCLUSIONS

Antiserum to r-ZPA inhibited fertilization in the animal species possessing a homologous amino-acid sequence as an immunogen. The recombinant protein, r-hZPA1-206 seems to be a feasible candidate for the development of contraceptive vaccines for humans.

[Biosynthesis of a single peptide chain containing human chorionic gonadotropin beta and C3D of complement]

In view of the strong immunity-enhancing function of HEL-C3d3 designed by Dr. Paul W. Dempsey, we made our efforts to produce a similar recombinant protein of hCG beta. With polymerase chain reaction, we introduced a Bam HI restriction site into the 3' terminal of hCG beta cDNA. The new cDNA and its terminal's correctness has been confirmed by sequencing. Then we have it covalently attached to the C3d3 cDNA at the pre-designed Bam HI/Bgl II site. Having the chimeric DNA correctly cloned into the protein nuclear polyhedrosis virus (AcNPV) expression vector pVL1393, we constructed the expression vector pVL1393-(hCG beta-C3d3). The insect cells were co-transfected with the expression vector and linearized nuclear polyhedrosis virus DNA, and recombinant viruses AcNPV-(hCG beta-C3d3) were screened out. Through anti-hCG beta immunoaffnity chromatography, the recombinant hCG beta-C3d3 chimera polypeptide was purified from culture supernatant of insect cells infected by the recombinant viruses. In RIA test, the expressed product competitively inhibits the binding of 125I-hCG beta to hCG beta-antibody. On SDS-PAGE and Western blot, the recombinant peptide hCG beta-C3d3 obviously appears to be with a molecular weight of 116KD. Therefore, we arrive at a conclusion that it has a normal immunogenic ability.

Testis-specific proteins and their role in contraceptive vaccine development

Development of a vaccine(s) based on sperm antigens represents a promising approach for contraception. The utility of an antigen in immunocontraception is contingent upon its testis/sperm specificity and involvement in spermatogenesis and/or fertilization. The aim of the present article is to review the information regarding the proteins that have been reported to be testis/sperm-specific and may have an important function in spermatogenesis and/or fertilization. The potential role of these proteins in the development an antisperm contraceptive vaccine(s) is discussed.

A potential approach to antifertility vaccine by expression of sperm membrane peptide in Salmonella

A synthetic oligonucleotide, HSD-2a, encoding a peptide segment of the extracellular domain of a human sperm membrane protein, YWK-II, was inserted by blunt-end ligation at the EcoRV site in the hypervariable, antigenically determinant region IV of Salmonella flagellin gene fliC (d). The recombinant plasmid (pLS408-H1) was transferred into the nonpathogenic aroA live vaccine Salmonella dublin strain SL5928, which is flagellin-negative. Location of the HSD-2a protein on the surface of the flagella was demonstrated by ELISA and by immunogold-labeling electron microscopy using mouse anti-YWK-II antiserum. A 60 kD protein, corresponding to the chimeric flagellin, was isolated from the recombinant S. dublin and found to contain the expressed HSD-2a peptide determined by Western blot analysis using anti-YWK-II antiserum. The Salmonella strain carrying the recombinant plasmid-pLS408-H1 may thus be a potential source of antifertility vaccine.

[Biosynthesis of a single peptide chain containing human chorionic gonadotropin beta and ovine common alpha subunits tandem]

hCG beta-oLH alpha chimeric cDNA was constructed by using overlapping PCR to contact the codons of C-terminal end of hCG beta with the codons of N-terminal end of oLH alpha, then it was subcloned into nuclear polyhedrosis virus (AcNPV) expression vector pVL1393 to construct expression vector pVL1393-hCG beta-oLH alpha. The insect cells (Sf9) were cotransfected by the expression vector pVL1393-hCG beta-oLH alpha and BaculoGold AcNPV linearized genomic DNA, and recombinant viruses AcNPV-hCG beta-oLH alpha were screened out by plaque assay. Further the insect cells were infected by the recombinant viruses, the recombinant hCG beta-oLH alpha was purified by immunoaffinity chromatography column coupling anti-hCG beta monoclonal antibody from the conditioned media of infected cells. The results of SDS-PAGE silver staining and western blotting showed that hCG beta-oLH alpha single peptide chain had apparent molecular weights of 40.5 kD and 38.0 kD under non-reducing and reducing conditions respectively, indicating the occurrence of disulfide bonds and significant tertiary structure in the single peptide chain. From the results of competitive inhibition of 125I-hCG beta binding we can conclude that the anti-hCG beta antibody-binding activity of hCG beta-oLH alpha chimera is lower than that of native hCG, but higher than that of native hCG beta. Therefore, we assume that the hCG beta-oLH alpha chimera should have potential application as a target antigen of anti-hCG fertility regulatory vaccine.

Reproductive rights and population control in Zimbabwe

The author argues that population control in Zimbabwe, in other developing countries, and even in developed countries is targeted at non-whites and at the poorer classes. She discusses fertility vaccines and male sterilization in this context, and makes the point that while the technology of population control flows from the North to the South, resources from the South are flowing North to maintain the economic status quo. "I think that the real population problem is the widening gap between a few greedy, irresponsible people, most of whom happen to be located in the North, and the rest of humankind, whose lives have been so denigrated that they are now merely statistics.... We can easily see that what should be feeding, clothing, housing, healing, pleasing Africans, goes North, all in the name of ¿development'."

Salmonella may offer contraceptive

A reversible, inexpensive birth control vaccine for men and women may come from an unlikely source--genetically altered salmonella bacteria. The bacteria cause food poisoning, typhoid and diarrhea. But with some genes removed and others spliced in, an altered form produces proteins that make the immune system reject sperm and does not cause disease, says Dr. Roy Curtiss, a biology professor at Washington University in St. Louis, Missouri, US. The approach was announced in November at a US meeting of the Council for the Advancement of Science Writing. "Salmonella act as the factory, making specific antigens. It is a slow-release system," he says. The altered bacteria produce sperm antigens, and both male and female immune systems make antibodies against them. To sustain immunity, a booster vaccine might be necessary every 6 to 12 months. Numerous concerns, however, have been raised over the use of such live vaccines. A live vaccine, for example, could accidentally immunize people through fecal contamination of water or food. Researchers are testing the vaccine approach in mice and are scheduled to begin experiments soon with macaque monkeys and baboons. Experiments among humans are not yet scheduled and would not begin until ethical and health issues are resolved. The contraceptive vaccine could be inexpensive to produce and would require no refrigeration, making it easy to store. It would probably be administered orally, eliminating costs and risks associated with injections, Dr. Curtiss says.