Vaccine for contraception targeting sperm

Catalysis-Mediated Male Contraception through Black Phosphorus Nanosheets

Nanocontraception has been proposed and received extensive attention in recent years for population control. However, currently developed methods for nanocontraception still face problems in efficacy and safety. Here, we propose catalysis-mediated oxidation as a new strategy for nanocontraception. With the catalytic production of highly oxidative species, male contraception was successfully achieved after the administration of black phosphorus nanosheets into the testes of male mice. Further mechanistic studies revealed that contraception was induced by oxidative stress and apoptosis of spermatogenesis cells. Meanwhile, the apoptosis of germ cells released testis antigen and induced immune cell infiltration, which enhanced reproductive damage. Notably, the introduced black phosphorus nanosheets naturally degraded during the catalytic oxidation process and ultimately converted to harmless phosphates, indicating the safety of the strategy. Furthermore, the catalysis-mediated strategy avoids utilizing additional inducers, such as near-infrared irradiation, magnetic fields, or ultrasound, which may cause severe pain. In summary, the proposed catalysis-mediated contraception can be a self-cleared, convenient, and safe strategy for controlling male fertility.

Characterization of a spontaneously occurring self-reactive antibody against sperm in mice

We previously established a spontaneously occurring monoclonal antibody, namely Ts3, that was reactive to sperm from an aged male mouse. The present study investigated the characteristic properties and reproductive functions of Ts3. Immunofluorescent staining revealed that Ts3 reacted to epididymal sperm, and the corresponding antigen was located in the midpiece and principal piece. Immunohistochemistry revealed positive reactions in the germ cells and Sertoli cells in the testis, the epithelial cells in the epididymis and vas deferens. Through western blotting with two-dimensional electrophoresis, we demonstrated that Ts3 reacted with four spots, which were around Mr ∼25,000-60,000 and pI 5-6. MALDI-TOF/TOF mass spectrometry identified outer dense fiber 2 (ODF2) as a candidate for Ts3. ODF2 is a cytoskeletal structural component located in the midpiece and principal piece of the flagella of mammalian sperm. This was validated with the result of immunofluorescent staining, suggesting that ODF2 was the main target antigen for Ts3. Sperm immobilization test showed that Ts3 possessed sperm immobilizing activity. Furthermore, Ts3 impaired early embryo development but not in vitro fertilization. These results suggest that ODF2 plays an important role in both sperm function and early embryonic development.

Engineering sperm-binding IgG antibodies for the development of an effective nonhormonal female contraception

Many women risk unintended pregnancy because of medical contraindications or dissatisfaction with contraceptive methods, including real and perceived side effects associated with the use of exogenous hormones. We pursued direct vaginal delivery of sperm-binding monoclonal antibodies (mAbs) that can limit progressive sperm motility in the female reproductive tract as a strategy for effective nonhormonal contraception. Here, motivated by the greater agglutination potencies of polyvalent immunoglobulins but the bioprocessing ease and stability of immunoglobulin G (IgG), we engineered a panel of sperm-binding IgGs with 6 to 10 antigen-binding fragments (Fabs), isolated from a healthy immune-infertile woman against a unique surface antigen universally present on human sperm. These highly multivalent IgGs (HM-IgGs) were at least 10- to 16-fold more potent and faster at agglutinating sperm than the parent IgG while preserving the crystallizable fragment (Fc) of IgG that mediates trapping of individual spermatozoa in mucus. The increased potencies translated into effective (>99.9%) reduction of progressively motile sperm in the sheep vagina using as little as 33 μg of the 10-Fab HM-IgG. HM-IgGs were produced at comparable yields and had identical thermal stability to the parent IgG, with greater homogeneity. HM-IgGs represent not only promising biologics for nonhormonal contraception but also a promising platform for engineering potent multivalent mAbs for other biomedical applications.

Evaluation of multi-epitope recombinant protein as a candidate for a contraceptive vaccine

Contraceptive vaccine (CV) is a valuable, non-invasive, and alternative method for purposeful contraception. Sperm antigens are useful targets for producing CVs due to their specialized expression in sperm. In this study, a recombinant protein containing three main sperm epitopes (IZUMO1, SACA3, and PH-20) was designed and evaluated as CV to control fertility in male mice. The chimeric recombinant protein was expressed and purified in E. coli. Male mice were immunized by 100 μg purified protein and sera were collected to assess IgG antibodies. Evaluating the reproductive performance, immunized male mice mated with normal-fertile female mice and mating rate and the number of newborns was studied. Immunized mice were sacrificed and necropsy and histopathology studies were conducted. The results revealed that the designed chimeric protein stimulated the immune system of the mice effectively. The level of IgG antibody was significantly higher in vaccinated mouse rather than control mouse. Eighty percent of the vaccinated mice became infertile and in the remaining ones, the number of children decreased to 4-6 offspring instead of 10-12 in normal mice. Histopathological studies showed that no organs including heart, brain, lung, liver, kidney and intestine were damaged. However, Normal spermatogenesis has been disrupted and necrotic spermatogonia cells were reported in Seminiferous tubules. We concluded that the designed chimeric protein containing IZUMO1, SACA3, and PH-20 epitopes can stimulate the immune system and cause male contraception without any side effects.

Human spermatozoa anti-proprotein convertase subtilisin/kexin type 4 synthesis using New Zealand rabbit for novel immunocontraception in males

Purpose

Proprotein convertase subtilisin/kexin type 4 (PCSK4, a 54-kDa protease) is expressed in the plasma membrane of the acrosome in human spermatozoa. It plays a critical role in penetrating the zona pellucida. Synthesis of human anti-PCSK4 might be important for novel male immunocontraception.

Materials and Methods

We used semen from adult males as the source of antigen (acrosomal PCSK4). Isolation and antigen characterization were done by immunohistochemistry followed by electrophoresis. Purification of PCSK4 was done by the electroelution method, followed by immunization with an animal model (Oryctolagus cuniculus). Antibody was collected, purified, and tested by using Western blot and dot blot. Antibody in vitro potential testing was performed on human spermatozoa by laser scanning microscopy with rhodamine stain under a light microscope and on rat spermatozoa.

Results

Human anti-PCSK4 bound with PCSK4 on the head of human spermatozoa and could interfere with rat spermatozoa activity to penetrate the oocyte.

Conclusions

The result of this study can be used as a basis to develop new immunocontraceptives targeted towards males. This study shows that antibodies from induction of PCSK4 from spermatozoa may hinder fertilization.

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.

Vaccine for human contraception targeting sperm Izumo protein and YLP12 dodecamer peptide

There is an urgent need to develop a better method of contraception which is non-steroidal and reversible to control world population explosion and unintended pregnancies. Contraceptive vaccines (CV), especially targeting sperm-specific proteins, can provide an ideal contraceptive modality. Sperm-specific proteins can induce an immune response in women as well as men, thus can be used for CV development in both sexes. In this article, we will review two sperm-specific proteins, namely Izumo protein and YLP12 dodecamer peptide. Gene-knockout studies indicate that Izumo protein is essential for sperm-egg membrane fusion. Vaccination with Izumo protein or its cDNA causes a significant reduction in fertility of female mice. The antibodies to human Izumo inhibit human sperm penetration assay. Recently, our laboratory found that a significant percentage of infertile women have antibodies to Izumo protein. The second sperm-specific protein is YLP12 , a peptide mimetic sequence present on human sperm involved in recognition and binding to the human oocyte zona pellucida. Vaccination with YLP12 or its cDNA causes long-term, reversible contraception, without side effects, in female mice. Infertile, but not fertile, men and women have antibodies to YLP12 peptide. Our laboratory has isolated, cloned, and sequenced cDNA encoding human single chain variable fragment (scFv) antibody from infertile men which reacts with YLP12 peptide. The human YLP12 scFv antibody may provide a novel passive immunocontraceptive, the first of its kind. In conclusion, sperm-specific Izumo protein and YLP12 peptide can provide exciting candidates for antisperm CV development.

Immunogenicity study of plasmid DNA encoding mouse cysteine-rich secretory protein-1 (mCRISP1) as a contraceptive vaccine

PROBLEM

To examine the immunocontraceptive properties of the plasmid pcDNA-mCRISP1 and compare them to the corresponding recombinant mCRISP1 (r-mCRISP1).

METHOD OF STUDY

RT-PCR and indirect immunofluorescence were performed to observe the mCRISP1 protein expression in COS-7 cells. Three groups of mice received three injections of r-mCRISP1, pcDNA-mCRISP1 or pcDNA vector, respectively. ELISA and Western blot were used to examine the immune responses and immunoreactivity of antisera. Sperm-egg penetration assay was performed to examine the effect of anti-mCRISP1 antibodies in vitro fertilization of mouse oocytes. Fertility and mean litter size were analysed by natural mating. Histological analysis was carried out to look for potential immunopathologic effects of the antibodies.

RESULTS

COS-7 cells transfected with pcDNA-mCRISP1 present the expression of mCRISP1. Both r-mCRISP1 and pcDNA-mCRISP1 raised an immune response against r-mCRISP1 protein and native CRISP1 in mouse sperm. The titres of anti-mCRISP1 antibodies from DNA immunized mice were significantly lower than that of r-mCRISP1 immunized mice, but it lasted relatively longer. Male and female pcDNA-mCRISP1 injected animals presented a statistically significant reduction in their fertility with no signs of immunopathologic effects.

CONCLUSION

These studies demonstrated the feasibility of generating an immune response to mCRISP1 protein by DNA vaccine and pcDNA-mCRISP1 plasmid causing significant anti-fertility potential.

Induction of specific immune response and suppression of fertility by B-cell-epitope-based mimovirus vaccine

SPINLW1 (previously known as eppin (epididymal protease inhibitor)) is a target under intense scrutiny in the study of male contraceptive vaccines. B-cell-dominant epitopes are now recognized as key parts of the induction of humoral immune responses against target antigens. The generation of robust humoral responses in vivo has become a crucial problem in the development of modern vaccines. In this study, we developed a completely novel B-cell-dominant-epitope-based mimovirus vaccine, which is a kind of virus-size particulate antigen delivery system. The mimovirus successfully self-assembled from a cationic peptide containing a cell-penetrating peptide of TAT49-57 and a plasmid DNA encoding both three SPINLW1 (103-115) copies and adjuvant C3d3. The male mice were immunized with the epitope-based mimovirus vaccine, which resulted in a gradual elevation of specific serum IgG antibody levels. These reached a peak at week 4. Mating for the fertility assay showed that the mimovirus vaccine had accomplished a moderate fertility inhibition effect and investigation into the mechanism of action showed that it did so by interfering with the reproductive function of the sperm but that it did not damage the structures of the testes or cause serum testosterone to decline. Our results suggest an ideal protocol for suppressing fertility in mice by an engineered mimovirus vaccine.

Antisperm contraceptive vaccines: where we are and where we are going?

This is a review of current status and future perspectives on the development of antisperm contraceptive vaccines (CV) and immunocontraceptives. The development of antisperm CV is an exciting proposition. There is a strong rationale and recent data indicating that this proposition can translate into reality. The search for novel sperm-specific antigens/genes, that can be used for CV, continues using various recent developing technologies. Various approaches of proteomics, genomics, reproductive biology, mucosal immunity and vaccinology and several novel technologies such as gene knockout technology, phage display technology, antibody engineering, differential display technique, subtractive hybridization, and hybridoma technology are being used to delineate sperm-specific antigens and construct CV. Various sperm antigens/genes have been delineated, cloned, and sequenced from various laboratories. Vaccination with these sperm antigens (recombinant/synthetic peptide/DNA) causes a reversible contraceptive effect in females and males of various animal species, by inducing a systemic and local antisperm antibody response. The efficacy is enhanced by combination vaccination, including peptides based on various sperm antigens. Several human novel scFv antibodies with unique complementarity-determining regions (CDRs), that react with specific well-defined fertility-related sperm antigens, have been synthesized. These human infertility-related antibodies may find application in the development of novel immunocontraceptives. Besides finding the novel sperm antigens, the present and future focus is on enhancing the immunogenicity, bioefficacy, and on obliterating the inter-individual variability of the immune response, and proceeding for primate and human clinical trials. Multi-epitope vaccines combining sperm proteins involved in various steps of fertilization cascade have been found to enhance the immunogenicity and bioefficacy of the contraceptive effect. The in vitro synthesis of infertility-related human scFv antibodies may provide unique once-a-month immunocontraceptives, the first of its kind, for human use. The multi-epitope CV and preformed engineered human antibodies of defined specificity may obliterate the concern related to inter-individual variability of the immune response.

New frontiers in nonhormonal male contraception

The world's population is nearing 6.8 billion, and we are in need of a male contraceptive that is safe, effective, reversible and affordable. Hormonal approaches, which employ different formulations of testosterone administered in combination with other hormones, have shown considerable promise in clinical trials, and they are currently at the forefront of research and development. However, the long-term effects of using hormones throughout a male's reproductive life for contraception are unknown, and it may take decades before this information becomes available. Because of this, many investigators are aiming to bring a nonhormonal male contraceptive to the consumer market. Indeed, there are several distinct but feasible avenues in which fertility can be regulated without affecting the hypothalamus-pituitary-testis axis. In this review, we discuss several approaches for fertility control involving the testis that one day may lead to the development of a nonhormonal male contraceptive.

Antifertility characteristics of the N-terminal region of mouse equatorial segment protein

To investigate antifertility characteristics of the equatorial segment protein (ESP) and its potential immunocontraceptive effect, three partially overlapping cDNA fragments P1/P2/P3, together covering the entire mouse ESP, were cloned, expressed, and purified. The roles of P1/P2/P3 in fertility were investigated through in vitro fertilization and mouse mating test. Antibodies against P1/P2 significantly reduced the rates of fertilization in vitro in the zona-intact experiments. Coincubation of zona-free mouse oocytes with capacitated mouse spermatozoa in the presence of antibodies against P1/P2 also inhibited sperm-oolemma binding and fusion, while anti-P3 antibody virtually had no effect on in vitro fertilization at the same concentration. Immunization of female BALB/c mice with N-terminal of mouse ESP (recombinant P1 and P2) resulted in a significant decrease in the fertility rate as well as the litter size. Double immunofluorescence staining showed that mouse ESP protein was localized to the equatorial segment of acrosome of mouse sperm, and was exposed and surface-accessible after acrosome reaction. Mouse ESP was also demonstrated to have complementary binding sites on the mouse egg plasma membrane by indirect immunofluorescence assay. These findings suggest that the N-terminal of mouse ESP could play an important role in fertility and might be a vaccine candidate for contraception.

Development of genetically engineered human sperm immunocontraceptives

Contraceptive vaccines targeting sperm are an exciting proposition. This review is focused on anti-sperm contraceptive vaccines and genetically engineered human antibodies that can be used as immunocontraceptives. Various methods of vaccinology and antibody engineering have been used to obtain multi-epitope contraceptive vaccines and human single chain variable fragment (scFv) antibodies from immunoinfertile and vasectomized men. Contraceptive vaccines comprised of various sperm antigens, peptide epitopes or DNA have shown various degrees of reversible contraceptive effect in the mouse model and their efficacy is enhanced with the multi-epitope combination vaccine. Failure to achieve a complete fertility block is probably due to variability in the host immune response. Using phage display technology, our laboratory has synthesized in vitro at least four novel scFv antibodies with unique complementarity determining regions (CDRs) that react with specific fertility-related sperm antigens employing cDNA from immunoinfertile and vasectomized men. These antibodies inhibit human sperm function in vitro, and their immunocontraceptive effect in vivo is being investigated. If these human scFv antibodies block fertility in vivo they may provide unique and novel immunocontraceptives, a first-in-kind for human use. The multi-epitope contraceptive vaccines and preformed engineered antibodies of defined specificity may eliminate concern related to inter-individual variability of the immune response.

In vitro and in vivo studies evaluating recombinant plasmid pCXN2-mIzumo as a potential immunocontraceptive antigen

PROBLEMS

Study on feasibility of pCXN2-mIzumo as a potential immunocontraceptive antigen.

METHOD OF STUDY

Two groups of mice received 100 microg/mouse plasmids of pCXN2-mIzumo and pCXN2 respectively. RT-PCR Immunofluorescence assay and ELISA were performed to observe pCXN2-mIzumo expression and antibody response in the inoculated mice. Sperm penetration assay and animal mating were employed to detect differences of in vitro fertilization (IVF) rate and mean litter size between the experimental and control groups.

RESULTS

Izumo cDNA positive bands were detected in sample from mice immunized with pCXN2-mIzumo. IgG response started to rise at 2 weeks after first boost and reached the highest antibody titers at 2 weeks after third boost of immunization with pCXN2-mIzumo in the experimental mice. In vitro fertilization rate in the experimental group (11.57%) was significantly lower than that in control (36.60%). Significant difference of mean litter size between female experimental and control groups was observed, and there was significant negative correlation between individual anti-serum titers and litter size (r = -0.308, P < 0.05).

CONCLUSION

pCXN2-mIzumo plasmid possesses appreciable anti-fertility potential.

Status of contraceptive vaccines

PROBLEM

This is a review of anti-sperm contraceptive vaccines (CV), and synthesis of human scFv antibodies that can be used as immunocontraceptives.

METHOD OF STUDY

Various methods of proteomics and genomics, peptide synthesis, phage display technology, and antibody engineering were used to obtain multi-epitope vaccines and human scFv antibodies from immunoinfertile and vasectomized men. The present review primarily focuses on the effect of multi-epitope vaccines and Izumo on fertility, and synthesis and characterization of sperm specific human scFv antibodies.

RESULTS

The immunization with Izumo peptides causes a contraceptive effect in female mice. The efficacy is enhanced by combination vaccination, including peptides based on other sperm antigens. Using phage display technology, we were able to synthesize at least four novel scFv antibodies with unique complementarity determining regions (CDRs) that reacted with specific fertility-related sperm antigens. These antibodies inhibited human sperm function in vitro, and their immunocontraceptive effect in vivo by these antibodies is currently being investigated.

CONCLUSION

The multi-epitope vaccines may provide an efficacious and viable approach to contraception. The human scFv antibodies, if they block fertility in vivo, may provide unique and novel immunocontraceptives, the first of its kind for human use. The multi-epitope CV and preformed engineered antibodies of defined specificity may obliterate the concern related to inter-individual variability of the immune response.

Experimental immunological infertility effect of anti-GAPDH-2 antibodies on the fertility of female mice

OBJECTIVE

To examine the relationship between an antibody against GAPDH-2, a sperm-specific protein, and infertility of female mice.

DESIGN

Basic research.

SETTING

National Research Institute for Family Planning Beijing, World Health Organization Collaboration Center of Human Reproduction.

ANIMAL(S)

New Zealand rabbit, NIH and ICR mice.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Enzyme-linked immunoabsorbent assay, Western blot and indirect immunostaining assays, standard fertility assay, and sperm agglutination assay.

RESULT(S)

Antibodies against the full-length GAPDH-2 were raised. Its specificity was assessed by immunoblotting and indirect immunostaining assays. The antibody immunoreacted with human sperm GAPDH-2 and the mouse homolog GAPDS but did not cross-react with GAPDH. Treatment of female mice with IP injection of anti-GAPDH-2 serum significantly reduced their fertility. Anti-GAPDH-2 serum caused the agglutination of normal mice sperm in vitro. The anti-GAPDH-2 antibody was detectable in the sera and uterine fluid of the mice immunized with GAPDH-2.

CONCLUSION(S)

These results show that GAPDH-2 should be further evaluated as a promising candidate in the development of an antifertility immunogen. Detecting anti-GAPDH-2 antibodies in the bodily fluid of subjects afflicted with indeterminate infertility may be a new diagnostic index.

Identification of sperm antigens as a first step towards the generation of a contraceptive vaccine to decrease fossorial water vole Arvicola terrestris Scherman proliferations

Immunocontraceptive strategies have proved to be efficient in controlling fertility of various mammalian species. In the present study we have made the first steps towards the identification of Arvicola terrestris sperm antigens that could be used as targets in the development of a contraceptive vaccine to limit the proliferations of this pest rodent. Rabbit-raised polyclonal antisera directed against complete A. terrestris spermatozoa were used to identify and characterize on 2D-gels coupled with a MALDI-TOF mass spectrometry analysis A. terrestris sperm proteins. Amongst the proteins pinpointed by this approach some were further investigated based on their tissue- and/or sperm-specific expression, and their relevance to fertility or sperm/egg interaction. In parallel, three proteins that have been already reported in the literature to be appropriate targets for the development of contraceptive vaccines in other mammalian species have also been looked for in A. terrestris. With the selected protein targets, a reverse-PCR approach using degenerate primers was employed to amplify corresponding A. terrestris cDNAs. After conceptual translation and sequence alignment, different proteins were studied to determine zones with sufficient sequence divergence and of antigenic/immunogenic nature that could be used in future assays to immunize animals.

Molecular adjuvant C3d3 improved the anti-hCGbeta humoral immune response in vaginal inoculation with live recombinant Lactobacillus expressing hCGbeta-C3d3 fusion protein

To enhance the contraceptive efficiency of human chorionic gonadotrophin (hCG)-beta contraceptive vaccine, we coupled hCG-beta gene with molecular adjuvant C3d3, and cloned into live Lactobacilli (Lb.) to express fusion protein hCGbeta-C3d3. The recombinant Lb. could survive in BALB/c murine vagina for at least 3 weeks. After inoculating BALB/c and C57BL/6 mice via vagina, we found that the antibody titer peaks induced by the Lb.hCGbeta-C3d3 inoculation were higher significantly than the Lb.hCGbeta. T and B cells in spleen and vagina were significantly increased, and anti-hCGbeta IgG and IgA antibody-secreting cells in uterus and vagina were significantly increased compared to the control in different strain mice. Our study shows that the C3d3 can display apparent adjuvant efficiency to induce more powerful humoral response to the hCGbeta antigen in vaginal mucosal immunization.

Biomarkers of semen in the vagina: applications in clinical trials of contraception and prevention of sexually transmitted pathogens including HIV

Biomarkers of vaginal exposure to semen, long used in forensic medicine, are now becoming important in the development of vaginal microbicides to prevent HIV/STIs and the development of contraceptives. Semen biomarkers could help evaluate the safety of a new physical or chemical barrier, give preliminary indication of the effectiveness of physical barriers such as diaphragms or condoms, and provide information on unprotected intercourse among participants in a clinical trial who have been advised to use condoms. Candidate biomarkers of semen exposure fall into two broad categories: (1) biomarkers of seminal plasma, among which prostate-specific antigen (PSA) is the best characterized; and (2) biomarkers of spermatozoa and other cells present in semen. This paper, authored by a working group of investigators performing research in the field of semen biomarkers, summarizes the characteristics of an ideal semen biomarker, reviews preclinical and clinical data on existing and potential biomarkers, and outlines the steps that should be carried out to develop an improved biomarker of semen exposure.

Inhibition of mouse acrosome reaction and sperm-zona pellucida binding by anti-human sperm membrane protein 1 antibody

AIM

To investigate the possible functions of human sperm membrane protein (hSMP-1) in the process of fertilization.

METHODS

A 576-bp cDNA fragment of HSD-1 gene coding for the extracellular domain of hSMP-1 was cloned and expressed. The localization of this protein on human and mouse sperm was determined by indirect immunofluorescent staining by using anti-recombinant hSMP-1 (anti-rhSMP-1) antibodies. Sperm acrosome reaction and sperm-zona pellucida (ZP) binding assay were carried out in 10-week-old BALB/c mice.

RESULTS

Recombinant hSMP-1 was successfully cloned and expressed. The expression of the native protein was limited on the acrosome of human and mouse sperm. Treatment of anti-rhSMP-1 antibodies significantly decreased the average number of sperms bound to each egg. Meanwhile, the percentage of acrosome reaction was decreased in comparison to pre-immune control after treatment with anti-rhSMP-1 (P < 0.05).

CONCLUSION

The results suggest that anti-rhSMP-1 antibody inhibited mouse acrosome reaction and sperm-ZP binding.

Mucosal inoculation of Lactobacillus expressing hCGβ induces an anti-hCGβ antibody response in mice of different strains

To show that an anti-human chorionic gonadotrophin-beta (hCGbeta) antibody response can be induced by inoculating Lb. expressing hCGbeta through different mucosal pathways in mice of two strains, female BALB/c and C57BL/6 mice were immunized via vaginal, oral or nasal routes with 10(8), 10(9), and 10(10)Lb.hCGbeta (a recombinant Lactobacillus expressing hCGbeta). The mice were immunized twice with a booster in study week 3. An indirect ELISA was used to determine anti-hCGbeta IgG and IgA antibodies in vaginal lavage and serum, obtained from the 2nd to 8th week after the primary immunization. Flow cytometry was used to analyze the lymphocyte proliferation from these tissues, 1 week after the primary immunization. The hCGbeta antigen-specific antibody-secreting cells of spleen, uterus, and vagina were evaluated by enzyme-linked immunospot assay (ELISpot), 2 weeks after the booster. The analysis showed that 10(9) and 10(10)Lb.hCGbeta inoculations induced similar anti-hCGbeta antibody responses, while the three mucosal pathways induced similar antibody responses. The antiserum obtained after boosters with 10(9) and 10(10)Lb. hCGbeta was able to neutralize more than 100 ng/ml hCG antigen, both in BALB/c and C57BL/6 mice. The highest antibody titer induced by vaginal mucosal immunization was stronger than that obtained via the other mucosal pathways. The B cells in the vagina appeared to proliferate after vaginal immunization (P<0.05). The numbers of anti-hCGbeta IgG and IgA antibody-secreting cells in the uterus and vagina were greater than in the spleen. Therefore, the vaginal mucosal route appears to be a better immunization pathway to induce higher anti-hCGbeta antibody levels in the reproductive tract.

Antisperm Vaccine for Contraception

PROBLEM

This study is a review of antisperm contraceptive vaccine (CV) development with the main focus on research going on in our laboratory.

METHOD OF STUDY

Various methods of proteomics and genomics, hybridoma technology, substractive libraries, differential display method, and phage display technology were used to obtain sperm-specific genes and proteins. The present study will primarily focus on the sequences obtained by using the phage display technology and their role in CV development and human immunoinfertility.

RESULT

Four novel peptides, delineated by using the phage display technology, were found to be involved in human immunoinfertility. The vaccine based on one of these peptides, designated as YLP(12), caused a reversible contraception in female mice.

CONCLUSIONS

The vaccine targeting sperm is a feasible and exciting approach to contraception. The phage display technology is a powerful tool to delineate sperm-specific peptide sequences that can be used for the CV development and in the diagnosis and treatment of infertility mediated through antisperm antibodies.

Inoculation of Lactobacillus expressing hCG beta in the vagina induces an anti-hCG beta antibody response in murine vaginal mucosa

OBJECTIVES

To test the possibility of vaccination with lactobacillus expressing hCG beta antigen administered by vaginal mucosal immunization.

METHODS

A plasmid pIlac-hCG beta was constructed and then transfected into Lactobacillus casei CECT5276, which stably expressed hCG beta protein. RIA was used to detect hCG beta in the culture supernatant and cell lysate. Western blotting was performed to evaluate the expressed protein of interest. Female BALB/c mice aged 6-8 weeks received inoculations in the vagina of the recombinant L. casei CECT5276. ELISA was used to determine the anti-hCG beta IgA antibody in vaginal lavage fluid from the BALB/c mice after vaginal mucosal immunization.

RESULTS

The pIlac alone appeared to have a higher efficiency than pIlac-hCG beta, and the highest transfection efficiency of both plasmids was at pulse voltages of 1200 V and 1500 V. About 78.5% of the hCG beta protein was excreted into the culture supernatant. Excretion of hCG beta was most efficient when the pH of the culture medium was adjusted to around 7.0 and the concentration of lactose was around 1%. The hCG beta protein in the vaginal lavage fluid of these BALB/c mice was positive on the third day after vaginal inoculation. Anti-hCG beta IgA antibody continued to be found in the vaginal lavage fluid for 2 weeks following a booster vaginal inoculation. The splenic lymphocytes of the mice immunized with hCG beta through the vagina underwent a proliferative reaction to hCG antigen restimulation in vitro. Interferon gamma (IFN-gamma) and interleukin (IL)-4 were secreted at higher levels after vaginal mucosal immunization of L. casei expressing hCG beta than after vaginal mucosal immunization of L. casei alone.

CONCLUSIONS

Vaginal immunization of lactobacillus expressing hCG beta induced an anti-hCG beta antibody response in the murine vaginal mucosa. Induction of the antigen-specific antibodies in the reproductive tract following vaginal inoculation of recombinant lactobacillus will lead to the development of a safe, efficient, and easy-to-use form of immunocontraception.

Recent advances in contraceptive vaccine development: a mini-review

Contraceptive vaccines (CV) may provide viable and valuable alternatives to the presently available methods of contraception. The molecules that are being explored for CV development either target gamete production [luteinizing hormone-releasing hormone (LHRH)/GnRH, FSH], gamete function [sperm antigens and oocyte zona pellucida (ZP)], and gamete outcome (HCG). CV targeting gamete production have shown varied degrees of efficacy; however, they either affect sex steroids causing impotency and/or show only a partial rather than a complete effect in inhibiting gametogenesis. However, vaccines based on LHRH/GnRH are being developed by several pharmaceutical companies as substitutes for castration of domestic pets, farm and wild animals, and for therapeutic anticancer purposes such as in prostatic hypertrophy and carcinoma. These vaccines may also find applications in clinical situations that require the inhibition of increased secretions of sex steroids, such as in uterine fibroids, polycystic ovary syndrome, endometriosis and precocious puberty. CV targeting molecules involved in gamete function such as sperm antigens and ZP proteins are exciting choices. Sperm constitute the most promising and exciting target for CV. Several sperm-specific antigens have been delineated in several laboratories and are being actively explored for CV development. Studies are focused on delineating appropriate sperm-specific epitopes, and increasing the immunogenicity (specifically in the local genital tract) and efficacy on the vaccines. Anti-sperm antibody (ASA)-mediated immunoinfertility provides a naturally occurring model to indicate how a vaccine might work in humans. Vaccines based on ZP proteins are quite efficacious in producing contraceptive effects, but may induce oophoritis, affecting sex steroids. They are being successfully tested to control feral populations of dogs, deer, horses and elephants, and populations of several species of zoo animals. The current research for human applicability is focused on delineating infertility-related epitopes (B-cell epitopes) from oophoritis-inducing epitopes (T-cell epitopes). Vaccines targeting gamete outcome primarily focus on the HCG molecule. The HCG vaccine is the first vaccine to undergo Phase I and II clinical trials in humans. Both efficacy and lack of immunopathology have been reasonably well demonstrated for this vaccine. At the present time, studies are focused on increasing the immunogenicity and efficacy of the birth control vaccine, and examining its clinical applications in various HCG-producing cancers. The present article will focus on the current status of the anti-sperm, anti-ZP, anti-LHRH/GnRH and anti-HCG vaccines.

Contraceptive vaccines

The world's population is growing at a tremendous rate, affecting growth and development. Apart from this population growth, unintended pregnancies resulting in elective abortions continue to be a major public health issue. In over half of these unintended pregnancies, the women have used some type of contraception. Thus, there is an urgent need for a better method of contraception that is acceptable, effective and available. The contraceptive choices available to women at this time include steroid contraceptives, intrauterine devices, barrier methods, spermicides, natural family planning, male and female sterilisation, and recently available emergency contraceptives. Contraceptive vaccines (CVs) may provide viable and valuable alternatives that can fulfill most, if not all, properties of an ideal contraceptive. Since both the developed and most of the developing nations have an infrastructure for mass immunisation, the development of vaccines for contraception is an exciting proposition. The molecules that are being explored for CV development either target gamete production (gonadotropin releasing hormone, follicle-stimulating hormone and luteinising hormone), gamete function (zona pellucida [ZP] proteins and sperm antigens) or gamete outcome (human chorionic gonadotropin [hCG]). Disadvantages of CVs targeting gamete production are that they affect sex steroids and/or show only a partial effect in reducing fertility. CVs targeting gamete function are better choices. Vaccines based on ZP proteins are quite efficacious in producing contraceptive effects. However, they invariably induce oophoritis affecting sex steroids. Sperm antigens constitute the most promising and exciting targets for CVs. Several sperm-specific antigens have been delineated in several laboratories and are being actively explored for CV development. Antisperm antibody-mediated immunoinfertility provides a naturally occurring model to indicate how an antisperm vaccine will work in humans. Vaccines targeting gamete outcome primarily focus on the hCG molecule. The hCG vaccine is the first vaccine to undergo phase I and II clinical trials in humans. Both the efficacy and the lack of immunotoxicity have been reasonably well demonstrated for this vaccine. The present studies focus on increasing the immunogenicity and efficacy of this birth control vaccine.

Contraceptive vaccines targeting sperm

Overpopulation is a global problem of significant magnitude, with grave implications for the future. Development of new contraceptives is necessary, as existing forms of birth control are unavailable, impractical and/or too expensive for many individuals due to sociological, financial or educational limitations. Immunocontraception and, in particular, the targeting of antibodies to sperm-specific antigens implicated in sperm-egg binding and fertilisation offers an attractive approach to control fertility. Sperm-specific antibodies may impair fertility by inhibiting sperm motility, by reducing penetration of the cervical mucus by sperm, or by interfering in sperm capacitation or the acrosome reaction; alternatively, antisperm antibodies may invoke the complement cascade, resulting in sperm lysis. The antibodies raised against sperm-specific antigens have proved to be extremely effective at reducing sperm-egg interactions in vitro; fertility trials in subhuman primates will eventually be needed to prove the effectiveness of the sperm antigens in terms of contraceptive efficacy before trials in humans can be justified. In addition, existing and emerging strategies (such as sperm proteomics, the determination of molecular and structural details of sperm proteins, and the modelling of protein-ligand interactions using X-ray and/or NMR structures to name a few) are expected to provide the experimental foundation for the design of small molecule inhibitors with antifertility effects. The technology underpinning vaccine development is constantly being developed and the introduction of DNA/RNA vaccines is certain to impact upon the field of immunocontraception.

Prostasome antigens as targets for sperm agglutinating antibodies demonstrated by 1-D gel electrophoresis and immunoblottings

Many immunoinfertile men have sperm agglutinating antibodies that are directed against prostasome-derived antigens, but these antigens have not been defined so far. We selected serum samples with high ELISA titres against prostasomes from a group of immunoinfertile patients with sperm agglutinating antibodies and used the sera for immunoblottings on 1-D SDS-PAGE of prostasomes and sperm cells. The immunoblottings with individual antiprostasome antisera on 1-D SDS-PAGE of prostasomes, revealed three to 10 bands for each serum. Eighty-five per cent of the serum samples contained bands in the 70-75 kDa region and 80% of the samples contained bands in the 50-55 kDa region. Immunoblottings of extracted sperm cells, revealed one to six bands in the molecular weight range 25-82 kDa and two of the samples recognized two bands with molecular weights (50 and 43 kDa) similar to immunoblottings of prostasomes. The prostasomal antigens recognized by the high titre-antisera of immunoinfertile men were generally different from the sperm antigens recognized by the same sera. This suggests that prostasomes offer a new set of antigens available for research on male immunoinfertility and immunocontraception.

Immunological tools for the assessment of both humoral and cellular immune responses in Foxes (Vulpes vulpes) using ovalbumin and cholera toxin B as an antigenic model

The immune response in the fox (Vulpes vulpes), despite the success of the oral rabies vaccine is not well characterized, and specific immunological tools are needed. To investigate both the humoral and cellular immune response, we used ovalbumin (OVA) and cholera toxin B (CTB) as an antigenic model to set-up ELISA and ELISPOT antibodies secreting cells (ASC) assays in the fox model. Identification of antibodies that cross-react with fox immunoglobulin was performed by Western blot, and their use was adapted for both the ELISA and ELISPOT ASC assay. The humoral and cellular specific immune responses were assessed after intra-muscular or intra-nasal immunization. Intra-muscular immunization resulted in the development of both cellular and humoral anti-OVA and anti-CTB responses in peripheral blood mononuclear cells (PBMCs). Immunization via the intra-nasal route resulted in the development of a cellular and humoral response against CTB in PBMCs. This immune response was confirmed using splenocytes from immunized animals by ELISPOT assay at euthanasia. Females immunized via the intra-nasal route developed specific anti-CTB IgM, IgA and IgG in vaginal fluids after the initial boost (day 26) showing that mucosal immunization produces a vaginal immune response in foxes. These immunological tools developed here are now available to be adapted to other antigenic models to facilitate further immune studies in foxes.

Molecular Cloning, Expression of Testicular Transcript Abundant in Germ Cells and Immunobiological Effects of the Recombinant Protein

PROBLEM

It has been well documented that antisperm antibodies can be causative factors for infertility. In this report we have identified a protein on human sperm referred as human sperm-associated protein (HSAP) using serum of an immunoinfertile woman; it is thus a sperm-specific protein--a candidate molecule for control of fertility.

METHOD OF STUDY

An immunoinfertile woman serum showing head-head sperm agglutination and acrosomal localization, reacted with human sperm protein of apparent molecular weight of 48 kDa on Western blot. Anti-48 kDa antiserum was raised in rabbit by eluting 48 kDa protein and was used to screen the human testis cDNA expression library. A putative positive hsap cDNA clone was obtained, sequenced and subjected to tissue specificities studies by Northern blotting. The cell type-specific expression was done using in situ RNA hybridization studies. To obtain recombinant HSAP (r-HSAP), hsap cDNA was cloned in pET 22b(+) expression vector. r-HSAP was expressed as polyhistidine fusion protein in Escherichia coli and purified. Rabbits were immunized with the purified r-HSAP, which led to generation of antibodies. In order to evaluate in vitro immunocontraceptive potential, the anti-r-HSAP antibodies were characterized by agglutination assay, zona-free hamster egg penetration assay, indirect immunofluorescence (IIF) assay, and by flow cytometry analysis.

RESULTS

We have cloned a human testis gene encoding a protein (HSAP) of 328 amino acids. Antibodies against the purified recombinant protein specifically recognized approximately 40 kDa r-HSAP, and a cognate 48 kDa protein band in human sperm extract in Western blot procedure. The anti-r-HSAP antibodies localized acrosomal compartment, inhibited sperm binding/attachment in zona-free hamster penetration assay and revealed surface binding with human live sperm by flow cytometry. The cDNA sequence has been submitted to EMBL and has been given the accession number Y16676.

CONCLUSION

This study has put in evidence that novel sperm-specific r-HSAP has role in sperm function and may have application in the development of a contraceptive vaccine. The availability of the recombinant protein will facilitate studies on the assessment of its potential as a contraceptive immunogen.

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.

Effect of active immunization with the C-terminal 67-94 (R-28) region of human seminal plasma inhibin on the fecundity of adult male rabbits

PROBLEM

To characterize the specificity of antibodies to the synthetic C-terminal 67-94 (R-28) peptide of human seminal plasma inhibin (hSPI), and to examine the effect of active immunization on the fecundity of adult male animals.

METHOD OF STUDY

The specificity of R-28-DT antibodies was tested using enzyme-linked immunosorbent assay, immunohistochemical and immunofluorescence staining, and Western blotting. For fertility studies, adult male rats and rabbits were immunized and mated with females of the same strain.

RESULTS

Rabbit antibodies to R-28-DT recognized native hSPI, as demonstrated by sperm agglutination in vivo and in vitro, on the sperm head by immunofluorescence staining, and in the columnar epithelial cells of the prostate by immunohistochemical staining. Immunization with the R-28-DT conjugate elicited a poor antibody response in male rats and their fecundity remained unaffected, while in male rabbits it elicited a good immune response with reduction in their fertility.

CONCLUSION

R-28-DT antibodies recognized the native hSPI in the prostatic epithelium and agglutinated washed rat, rabbit, monkey, and human spermatozoa in vitro. Immunization of rabbits caused agglutination of spermatozoa resulting in a decrease in their fecundity. The conjugated R-28 peptide of hSPI offers promise as a male contraceptive.

Use of cauda epididymis extract as immunocontraceptive

The objective of this study was to evaluate use of a cauda epididymis extract (CEE) as an immunocontraceptive in rats. Twenty-two rats in puberty or 19 rats that gave birth once (primipara) were immunized with intraperitoneal (IP) injection of CEE. Rats in puberty received one or two injections of CEE containing 1.5 x 10(9) sperm/mL, while primipara rats received injections of CEE containing 3 x 10(6) sperm/mL up to three times. Animals were tested for the presence and concentration of anti-CEE antibody by enzyme-linked immunosorbent assay (ELISA) and monitored for pregnancy following natural insemination. Results revealed that 38 (92.6%) of the 41 rats were positive for anti-CEE antibodies, regardless of animal type or immunization procedure. However, there was no relation between pregnancy rates and concentration of anti-CEE antibody in rats immunized with CEE. These results indicate that immune response against CEE may not play a major role in contraception in rats.

Male contraception

The provision of safe, effective contraception has been revolutionized in the past 40 yr following the development of synthetic steroids and the demonstration that administration of combinations of sex steroids can be used to suppress ovulation and, subsequently, other reproductive functions. This review addresses the current standing of male contraception, long the poor relation in family planning but currently enjoying a resurgence in both scientific and political interest as it is recognized that men have a larger role to play in the regulation of fertility, whether seen in geopolitical or individual terms. Condoms and vasectomy continue to be popular at particular phases of the reproductive lifespan and in certain cultures. Although not perfect contraceptives, condoms have the additional advantage of offering protection from sexually transmitted infection. The hormonal approach may have acquired the critical mass needed to make the transition from academic research to pharmaceutical development. Greatly increased understanding of male reproductive function, partly stimulated by interest in ageing and the potential benefits of androgen replacement, is opening up other avenues for investigation taking advantage of nonhormonal regulatory pathways specific to spermatogenesis and the reproductive tract.

A male genital tract-specific carbohydrate epitope on human CD52: implications for immunocontraception

The identification of unique sperm surface epitopes that are not expressed or exposed in the female reproductive tract is a key element in the development of antibody-based contraceptives. Western blotting and immunohistochemistry were performed to define the tissue distribution of the S19 epitope, which has been proposed as a target for immunocontraception. S19 is an IgG1 murine monoclonal antibody (mAb) directed to an N-linked carbohydrate epitope on a 15-25 kDa glycoprotein, sperm agglutination antigen-1 (SAGA-1), containing a peptide core identical to that of the lymphocytic surface protein CD52. In this study, the S19 epitope was shown to be absent from human lymphocytes, demonstrating a distinction between this epitope and the CAMPATH epitope that is recognized by an antibody against the terminal tripeptide and GPI-anchor of CD52. Further tissue specificity analysis identified the S19 epitope in the epithelium of the human epididymis and vas deferens, as well as on both epididymal and ejaculated spermatozoa. In contrast, the S19 epitope was absent in the five human female reproductive tract and 18 other somatic tissues tested. These results support the use of the S19 epitope as a contraceptive immunogen and the suitability of the S19 mAb as an intravaginal contraceptive. To test the agglutinating activity of the S19 mAb in a formulation designed for vaginal use, S19 mAb were bound to the surface of Novasomes, a multilamellar liposome delivery vehicle. S19-Novasome formulations agglutinated human spermatozoa and were as effective as unbound S19 mAb, demonstrating the feasibility of spermistatic contraceptives targeted to the male reproductive tract specific carbohydrate epitope.

Molecular cloning and sequencing of cDNA encoding for human FA-1 antigen

The cDNA encoding for the human FA-1 sperm antigen was cloned and sequenced from the in-house constructed subtractive human testis cDNA expression library in lambda Ziplox using the FA-1 monoclonal antibody (mAb). The full--length sequence was obtained by using the 5' rapid amplification of 5'-cDNA end (5'-RACE) procedure. It is 1,576-bp long, and has an open reading frame (ORF) of 283 amino acids (aa) with the first ATG Met start codon at nucleotide (nt) 57 and the stop codon TAG at nt 906. It has two termination codons at the 5' end before the ATG start codon. The translated protein has a calculated molecular weight of 32.1 kDa and estimated isoelectric point (pI) of 11.59. It has one potential N-linked glycosylation site and one tyrosine phosphorylation site, besides several O-linked glycosylation and serine and threonine phosphorylation sites. Hydrophilicity analysis of the deduced aa sequence showed it to be a membrane-anchored protein. Extensive computer search in the database did not identify any known nt/aa sequence having homology with FA-1 cDNA or deduced aa, indicating it to be a novel gene. The Northern blot and reverse transcription-polymerase chain reaction (RT-PCR)-Southern blot analyses indicated the testis-specific expression of FA-1 antigen at the mRNA level. The ORF of the FA-1 was subcloned into pGEX- 1lambda T for expression. The expressed FA-1 recombinant protein had a molecular size of approximately 40 kDa, and was recognized by the FA-1 mAb, and not by the myeloma control Ig. The rabbit antibodies (Ab) raised against the recombinant (r) FA-1 antigen recognized the rFA-1 antigen as well as the native (n) FA-1 antigen. The rFA-1 Ab specifically recognized a protein band of approximately 50 kDa in human testis extract in the Western blot involving 11 types of human tissue extracts, indicating the testis-specific expression of FA-1 at the protein level. The Ab showed binding with live and methanol-fixed human sperm at the post-acrosomal, mid-piece, and tail regions. The Ab caused a significant (P < 0.001) and concentration-dependent inhibition of human sperm capacitation/acrosome reaction by blocking tyrosine phosphorylation of the FA-1 antigen. The sperm-specific human FA-1 recombinant antigen may find applications in immunocontraception, and diagnosis and treatment of immunoinfertility in humans.

The development of contraceptive vaccines

The use of vaccination as a means of controlling fertility was established during the last decade with the publication of a successful Phase II trial demonstrating the efficacy of this approach to family planning. However, only this one Phase II trial has been completed despite a plethora of hormonal and gamete antigens that have been proposed as candidate vaccines. Improvements in the design and formulation of contraceptive vaccines are underway and will be a necessary prelude to further clinical trials.

Human sperm-specific peptide vaccine that causes long-term reversible contraception

A novel dodecamer peptide sequence, YLP(12), was identified on human sperm that is involved in oocyte binding. We investigated its immunocontraceptive effects in a murine model. A vaccine was prepared by conjugating the synthetic YLP(12) peptide with the binding subunit of recombinant cholera toxin. Vaccination of female mice by i.m. or intranasal routes without any additional adjuvant induced a sperm-specific immune response in serum and the vaginal tract that caused a long-term contraceptive state. Fertility was fully regained when antibody reactivity diminished at 305-322 days. The contraceptive effect was also completely reversed voluntarily by intravaginal administration of the peptide. Antibodies affected fertility at the prefertilization stage by inhibiting sperm capacitation and the acrosome reaction, and sperm-oocyte binding. The peptide sequence is an epitope of a 50 +/- 5-kDa membrane protein localized on the acrosome and tail of spermatozoa. Thus, the sperm-specific YLP(12) is an attractive candidate for contraceptive vaccine.

Immunization of female cynomolgus macaques with a synthetic epitope of sperm-specific lactate dehydrogenase results in high antibody titers but does not reduce fertility

Previous studies have reported reduced fertility in female baboons immunized with a synthetic peptide derived from the sperm-specific isozyme of lactate dehydrogenase (LDH-C). In this study, a similar approach was used to immunize female cynomolgus macaques with the same peptide sequence (bC5-19) conjugated to a T-cell epitope from tetanus toxin (TT). Twelve female monkeys were immunized with bC5-19:TT delivered with Ribi MPL adjuvant vehicle, and 10 control female monkeys were injected with the adjuvant vehicle only. All 12 females in the treatment group developed LDH-C-specific serum antibodies as measured by ELISA, but anti-LDH-C antibodies were not detected in vaginal fluids of the immunized animals. After 4 months of timed mating immediately following the immunizations, five of the ten immunized females became pregnant, as did six of the ten control females. Anti-sera from both pregnant and nonpregnant bC5-19:TT-immunized females recognize a single band at 35 kDa on Western blots of whole sperm extracts, and purified Igs from the same sera localize along the principle piece of the flagellum of permeabilized sperm.

Monoclonal antibody against human sperm-specific YLP12 peptide sequence involved in oocyte binding

The monoclonalantibody (mAb) against YLP12 peptide was raised and its immunobiological properties were examined. In the Western blot procedure, the YLP12 mAb recognized a specific protein band of approximately 50 +/- 5 kD in human sperm extract and approximately 72 +/- 5 kD in human testis extract. The myeloma Ig control did not recognize these specific protein bands. In the immunofluorescence studies, the YLP12 mAb, and not the myeloma Ig, predominantly reacted with the acrosome regions of methanol-fixed human sperm. In the acrosome reaction assay, the YLP12 mAb showed a significant (p < .001) and a concentration-dependent inhibition of acrosome reaction. The myeloma Ig did not affect the acrosome reaction. There was no apparent effect of antibodies on sperm motility. Thus, the monoclonal antibody, if humanized by genetic engineering technology, may provide a useful immunocontraceptive agent.

Down regulation of B cells by immunization with a fusion protein of a self CD20 peptide and a foreign IgG.Fc fragment

In vivo studies of mice were performed to investigate whether auto-reactive antibodies specific for self CD20 antigen on B cells could be induced by immunizing with a CD20 peptide linked to a foreign, human IgG.Fc fragment through a T cell immunologically inert linker peptide and how such an auto-reactivity, if generated, would affect the levels of B cells. The dimeric Fc fusion protein containing the extracellular 44-amino acid portion of CD20, and the CH2-CH3 domains of human gamma 1 immunoglobulin were prepared. After several subcutaneous immunizations with this CD20-Fc protein, mice produced anti-CD20 antibodies that can bind to native CD20 on normal B cells and B-lymphoma cells. In mice immunized with the CD20-Fc protein, the fraction of B cells in total peripheral blood lymphocytes decreased to about 40%, significantly lower than that of mice immunized with human IgG. In addition, antibody response towards an irrelevant bystander antigen, chicken ovalbumin, was weakened compared with that of mice immunized with human IgG. These results show that auto-reactive antibodies specific for CD20 can be induced by immunizing with an autologous CD20 peptide fused with a foreign IgG.Fc and that the auto-antibodies can partially reduce the levels of B cells and their response to other antigens.

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.

Testis-specific antigen (TSA-1) is expressed in murine sperm and its antibodies inhibit fertilization

PROBLEM

We recently cloned and sequenced a sperm-specific antigen, designated as testis-specific antigen-1 (TSA-1), from human testis. The present study was conducted to examine its expression and function in murine sperm, in order to find out whether or not the mouse can provide a suitable model for examining its immunocontraceptive effects.

METHOD OF STUDY

The antibodies (Ab) were raised against purified human rTSA-1 in virgin female rabbits. The rTSA-1 was run in sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and the gel containing the approximately 18 kDa band was cut, minced and used for immunization to obtain the specific Ab. The immunoglobulins from preimmune bleed and from animals injected with adjuvant alone served as control. These Ab were analysed in enzyme-linked immunosorbent assay (ELISA), Western blot procedure, immunoprecipitation procedure, immunocytochemical technique (ICT), immunobead binding technique (IBT), acrosome reaction and sperm-zona binding assay.

RESULTS

Active immunization of female rabbits with purified rTSA-1 protein of 18 kDa, produced high titer Ab against the recombinant antigen. These Ab to rTSA-1 were used in the present study. In Western blot procedure, rTSA-1 Ab recognized a specific protein band of approximately 24 +/- 3 kDa in murine sperm extract, the band similar to found in human sperm extract. In the immunoprecipitation procedure, rTSA-1 Ab immunoprecipitated the protein band of similar size from extracts of murine sperm and murine testis. The ICT and the IBT studies revealed the subcellular localization of TSA-1 on the surface of acrosome and tail regions of the non-capacitated and capacitated murine sperm cells. In functional bioassays, rTSA-1 Ab inhibited the acrosome reaction and sperm-egg binding in vitro.

CONCLUSIONS

These data indicate that the TSA-1 is expressed in murine sperm and may have a biological role in sperm function and sperm-egg binding. In vitro inhibition of capacitation/acrosome reaction and sperm-zona binding suggests that the mouse can provide a suitable model to examine the immunocontraceptive effects of TSA-1 in actively immunized animals.

Molecular and immunological characteristics of sperm antigens involved in egg binding

Development of a vaccine(s) based on sperm antigens represents a promising approach to contraception. The utility of an antigen in immunocontraception is contingent upon sperm/testis-specificity and its involvement in the fertilization process. Since, the sperm-zona pellucida (ZP) recognition and binding constitutes the most important event in the fertilization process, molecules involved at this site are attractive candidates for immunocontraception. Using hybridoma technology, subtractive hybridization, and differential display technology, our laboratory has delineated several sperm antigens. These antigens have testis-specific expression and have a role in the fertilization process. The cDNAs encoding for the antigens have been cloned and sequenced. Among these, the fertilization antigen (FA-1) is particularly interesting, because it is involved in immuno-infertility in humans. Using the phage peptide display technique, a novel dodecamer sequence of a approximately 72+/-5 kD antigen, designated as YLP(12), that is testis-specific and involved in human sperm-ZP recognition/binding, was identified. A synthetic 12-mer peptide was generated based on this sequence. In the hemizona assay, YLP(12) peptide and its monovalent Fab' antibodies specifically and significantly inhibited human sperm-ZP binding. Furthermore, the presence of specific antibodies reactive with YLP(12) peptide, were identified in the serum and seminal plasma of immuno-infertile men. Thus, FA-1 and YLP(12) are promising target antigens for the development of contraceptive vaccines as well as for specific diagnosis and treatment of male infertility.

Effect of antibodies to sperm-specific recombinant contraceptive vaccinogen (rCV) on murine fertilization: search for an animal model to examine its contraceptive potential

Recently, we cloned and sequenced a sperm-specific antigen, designated as Contraceptive Vaccinogen (rCV), from human testis (Naz et al., 2001). The present study was conducted to examine its proteomic homologue and function in murine sperm, in order to find out whether or not the mouse can provide a suitable model for examining its immunocontraceptive effects. This was examined by using purified antibodies (Ab) raised against the recombinant (r) human CV antigen of approximately 44 kD. In the Western blot procedure, rCV antibodies recognized a specific protein band of approximately 64 +/- 5 kD in murine testis and murine sperm extracts, the band similar to that found in human testis and human sperm. In the immunoprecipitation procedure, rCV Ab immunoprecipitated a protein band of similar size from murine sperm and murine testis extracts. The immunocytochemical (ICT), immunoscanning electronmicroscopic (ISEM) and the immunobead binding technique (IBT) revealed the subcellular localization of CV antigen on the surface of acrosome and tail regions of the noncapacitated and capacitated murine sperm cell. In functional bioassays, rCV Ab inhibited the acrosome reaction as well as sperm-egg binding in vitro. These data indicate that the CV antigen is expressed in murine sperm and has a biological role in sperm function and sperm-egg binding. In vitro inhibition of capacitation/acrosome reaction and sperm-zona binding suggest that the mouse can provide a suitable model to examine the immunocontraceptive effects of CV antigen in actively-immunized animals.