Generation of mouse oocyte monoclonal isoantibodies: their effects and those of antisperm monoclonal antibodies on in vitro fertilization

Monoclonal isoantibodies to mouse oocyte antigens were generated by modified hybridoma techniques similar to those described for mouse sperm monoclonals. Following isoimmunization with mouse oocytes and cell fusion, hybrid cells were cultured initially in a semi-solid medium containing methylcellulose. Seven to ten days after cell fusion about 350 hybrid clones were recovered for subculture. By an indirect immunofluorescence assay using frozen or fresh mouse oocytes, twenty hybridomas were shown to produce antibodies that bind to various oocyte components including antigens of the zona pellucida. However, they did not cross-react with mouse spermatozoa or lymphocytes.A system was established to evaluate whether monoclonal antibodies to gamete-specific antigens have any inhibitory effects on the fertilization of mouse oocytes in vitro. A monoclonal antibody against zona antigen(s), ME 56, was shown to block fertilization of mouse oocytes via the inhibition of sperm binding to the zona pellucida. On the other hand, three out of four antibodies reacting with mouse sperm acrosomes were also inhibitory to mouse in vitro fertilization, perhaps mainly due to the inhibition of sperm acrosomal reactions. Using a sodium dodecylsulfate gel/protein blot radioimmunobinding method, the molecular weight of zona antigen(s) that react with ME 56 was determined to be in the range of 95,000, whereas that of the acrosomal antigen(s) reacting with the fertilization-inhibiting antibody, MS 207, was about 30,000. The results of this preliminary study suggest that monoclonal antibodies to certain gamete antigens can be a valuable tool for the analysis of sperm-egg interactions during the fertilization processes.     

Immunocontraception

The immunological contraceptive methods whose development is described in this work appear to inhibit the action of antigenic molecules necessary for fertilization. Antigens in the gametes or their envelopes that intervene in reconnaissance or fusion of the gametes appear to be more promising targets than those at the level of gamete production in the gonads. Clinical examples show that infertility may be spontaneously acquired in both sexes through active immunization. Contraceptive action can only be sought if the gametes carry specific antigens, so that other physiological functions will not be disturbed, and if the antigens play a determining role in fertilization. Research currently is oriented toward 3 complementary targets, the sperm and the 2 envelopes of the oocyte, the zona pellucida and the cumulus oophorus. Possibilities appear to exist of preventing the intervention of several different molecules in fertilization, although most of them are still poorly understood. In the past 10 years, various monoclonal antibodies have been produced against sperm of different animal species, some of which are capable of inhibiting fertilization in the same species and also in human beings. But in vivo effects of these antibodies have not been valuated, even in the same species. Active immunization of male or female guinea pigs with a sperm surface antigen has led to sterility, through inhibition of attachment of sperm to the zona pellucida, but the monoclonal antibody against the protein does not recognize the human sperm. Polyclonal antibodies against the same protein might be possible for human contraception. The biochemical and physiological study of monoclonal antibodies against human sperm is facilitated if the antibodies cross with rodent sperm. 2 such antibodies directed against proteins secreted by the human testicles are capable of inhibiting murine and human fertilization in vitro. Attempts to achieve active or passive immunization by targeting antigens of the zona pellucida have been underway for 2 decades in different animal species using ever more selective antigenic material. But in vivo animal studies caused serious ovarian disorders that would be unacceptable in contraception. A polyclonal antibody against the intercellular matrix of the human cumulus oophorus is capable of inhibiting fertilization in vitro, with the action resulting from a strong reduction in the number of sperm attached to the zona pellucida. Numerous aspects of immunocontraception are still at the research stage. Apart from the choice of the moist appropriate antigens, active immunization in human subjects must be preceded by massive production of purified antigens. Research is needed on the adjuvant, the possibility of maintaining high levels of antibodies, and the return of fertility. Despite the obvious public health need, few laboratories are engaged in this type of research.     

Sperm antibodies and fertility

Some cases of infertility considered inexplicable have been found to have an immunologic basis. Spermatozoa are highly antigenic cells. When the state of immune tolerance is disrupted, auto-immunization in the man or isoimmunization in the woman can occur. The appearance of antibodies directed against the sperm antigens results in a condition of hypofertility more than of absolute sterility. Numerous antigens have been identified on sperm using monoclonal antibodies. Immunosuppressive substances have been isolated in the seminal liquid in vitro, and various other protective mechanisms have been identified. Autoimmunity apparently results from failure of the protective processes. Physical, chemical, or infectious trauma may explain the entry of immunocompetent cells. The most commonly used techniques for study of antisperm antibodies are those that detect antibodies directed against surface antigens. Sperm agglutination tests have been criticized for their numerous false positive findings and their failure to identify the classes of immunoglobulins implicated. Tests of immobilization or cytotoxicity are specific, with no false positives, but not sensitive, giving rise to false negatives. The Mixed Antiglobulin Reaction Test (MAR- test) is very specific, easy, inexpensive, and rapid, but it only detects IgG and determination of the place of fixation is difficult. The immunobead test proposed in 1982 overcame some of the limitations of the MAR-test. These two are the methods of choice in exploration of male autoimmunity. Radioimmunologic techniques, an ELISA-type test, and others have given less satisfactory results. The frequency of antisperm antibodies has been estimated at 3 to 15% in nonselected infertile men, 35% among men with some symptoms or a history of the condition, and less than 1% among fertile men. The antisperm antibodies have functional significance only when they are fixed to their antigens. Modifications of sperm mobility are the main problem, with blockage of transport to the oocyte and union with it. It is difficult to establish a prognosis because evaluation must be done individually. As the level of antibodies increases, the chances of spontaneous pregnancy decline. Several treatments have been developed but results have been disappointing. In vitro fertilization after separation of motile sperm without antibodies may improve the prospects of pregnancy.     

Sperm-zona pellucida interaction and immunological infertility

Immune reactions against gametes appear to be physiologically important for the maintenance of homeostasis in reproduction. In contrast, aberration of the immune homeostasis might give rise to ‘immunological infertility’. Antisperm antibodies cause infertility by blocking fertilization. The mechanism can be explained as inhibiting the acrosome reaction of sperm by their blocking effect on capacitation through inhibiting an increase of fluidity of the sperm membrane. Autoantibodies against zona pellucida also cause infertility by blocking sperm-zona pellucida interaction, though the definitive mechanism has not been elucidated. Pretreatment of spermatozoa with D-mannnose completely inhibited sperm penetration through, but not binding to, the zona pellucida. Furthermore, very rapid kinetics between sperm extracts and D-mannnose by a BIAcore apparatus suggest that a D-mannose ligand of the sperm surface is easy to bind to and dissociate from a D-mannose residue in the sperm receptor site on the zona pellucida. Thus, D-mannnose on the human zona pellucida might be an essential molecule acting as a second sperm receptor, through which sperm penetrate into the zona pellucida. Because these antibodies appear to not cause any deleterious clinical symptoms, sperm and zona pellucida antigens are promising candidates in the development of an immunocontraceptive.     

Inhibition of sperm penetration through human zona pellucida by antisperm antibodies

An in vitro penetration test using human spermatozoa, sera, and eggs stored in a highly concentrated salt solution was designed for examination of the effect of antisperm antibodies on the process of fertilization. Spermatozoa from a healthy fertile donor incubated in modified Biggers, Whiiten and Whittingham (BWW) medium containing 7.5% antisperm-antibody-negative serum, could penetrate through the zonae pellucidae of the stored eggs, but not when the spermatozoa from the same donor had been incubated in modified BWW medium containing 7.5% antisperm-antibody-positive serum. After the antisperm-antibody-positive serum was absorbed with washed spermatozoa, the sperm penetration was not blocked. Therefore, antisperm antibodies appear to block human sperm penetration through the human zona pellucida.     

Vasectomy: consequences of autoimmunity to sperm antigens.

Data from studies examining the effects of vasectomy in a large number of nonhuman primates vasectomized for periods ranging up to 14 years are summarized, and these findings and speculations are used as a framework with which to review the subject of autoimmunity and vasectomy. Attention is directed to autoimmunity to sperm antigens following vasectomy (factors affecting antisperm antibody levels, characteristics of circulating antisperm antibodies, antisperm antibodies in seminal plasma, and cellular immunity following vasectomy), and immunopathology of antisperm autoimmunity (local effects on the male reproductive tract and systemic effects on the male reproductive tract). The 6 hypotheses that have been advanced to explain individual variations in dynamics and types of antisperm antibodies produced following vasectomy are reviewed. 3 tests are commonly used to detect free antisperm antibodies after vasectomy: 1) the spermagglutination test; 2) the sperm immobilization test; and 3) the immunofluorescence test. Spermagglutinating (SA) antibodies, the most common type of antibody produced after vasectomy, occur in approximately 2/3 of vasectomized men and in a majority of vasectomized rhesus monkeys. Sperm-immobilizing (SI) antibodies are also produced in a large percentage (40%) of vasectomized men and rhesus monkeys. About 30% of vasectomized men also have antiprotamine antibodies.     

Effects of antibodies to sperm surface fertilization antigen-1 on human sperm-zona pellucida interaction.

OBJECTIVE: To investigate the effects of antibodies to well-defined sperm surface antigens (the fertilization antigen [FA-1] and germ-cell antigen [GA-1]) and nuclear antigen (protamine) on human sperm-zona interaction. DESIGN: Number of total and acrosome-reacted human sperm bound to the human zona pellucida and the sperm movement characteristics assessed by computer-aided sperm analysis were evaluated after incubation of sperm with the antibodies. SETTING: Academic research environment approved by the Institute Review Board. PATIENTS: Human oocytes were obtained from ovaries removed at surgery. Semen from fertile donors was used in all assays. INTERVENTIONS: Human oocytes were stored in salt solution at -80 degrees C until used. Spermatozoa were treated with the antibodies to various sperm antigens. MAIN OUTCOME MEASURES: Total and acrosome-reacted sperm bound to zona pellucida and sperm movement characteristics were evaluated after 3 to 5 hours of incubation of the antibodies with human sperm. RESULTS: Anti-FA-1 antibodies significantly reduced human sperm fusion with zona-free hamster oocytes and sperm binding to the human zona pellucida but did not affect binding of acrosome-reacted sperm and sperm movement characteristics. Anti-GA-1 and antiprotamine antibodies did not affect sperm-oocyte interaction, acrosomal reaction, or sperm motility. CONCLUSIONS: Antibodies to FA-1 but not to GA-1 and protamine inhibit human sperm-zona interaction.     

Identification of human sperm antigens reacting with antisperm antibodies from sera and genital tract secretions.

OBJECTIVE: To identify sperm antigens reacting with antisperm antibodies relevant in human infertility. DESIGN: The reactions of separated sperm antigens with antibodies present in sera and genital tract secretions from infertile and fertile females and males were examined by immunoblotting techniques. SETTING: The patients were followed in an outpatient setting of a hospital clinic. PATIENTS: One hundred consecutive infertile males and females, referred for determinations of antisperm antibodies, comprised the study group. Fifty hospital and faculty employees with proven fertility served as a control group. RESULTS: A high proportion of sera from fertile and infertile humans contained antibodies reacting with at least one sperm antigen. However, two discrete bands of antigenic proteins with molecular weights of 44 and 72 kd reacted significantly more frequently with serum antibodies from infertile females than from fertile females. No apparent correlation could be demonstrated between any particular antigen and serum antibodies from infertile males. Nevertheless, antigenic proteins of 62 kd were identified as the major sperm antigens reacting with antibodies present in seminal plasmas from infertile males. CONCLUSIONS: The major sperm antigens reacting with systemic antibodies differ from the antigens recognized by local antisperm antibodies. Sperm antigens exhibiting relative molecular weights of 62 kd are major antigens reactive with local antisperm antibodies from infertile humans.     

Heterogeneity of antigenic determinants on human spermatozoa: relevance to antisperm antibody testing in infertile couples

Sera from 1074 male and 947 female partners of infertile marriages were tested by enzyme-linked immunosorbent assay for antibodies to motile sperm purified from ejaculates of the male partners or a donor. In men, 9.2% of the sera were positive for immunoglobulin A, 7.9% for immunoglobulin G, and 5.1% for immunoglobulin M antibodies to their own sperm. In women, immunoglobulin M antibodies to the husband's sperm predominated (10.1%), with immunoglobulins G (8.3%) and A (5.9%) following. Differences between men and women in the incidence of immunoglobulin A (p less than 0.01) and M (p less than 0.005) antibodies were significant. In both sexes only about two thirds of the antibody-positive sera remained positive when donor sperm was substituted for partners' sperm in the assay. The decreased occurrences of antisperm immunoglobulins A (p less than 0.025) and G (p less than 0.01) in men and of immunoglobulins G (p less than 0.025) and M (p less than 0.01) in women were significant. Incubation of donor sperm in the husband's cell-free seminal fluid before analysis led to the acquisition of sperm reactivity with husband-specific antisperm antibodies in only one of eight women. Women with husband-specific antisperm antibodies also exhibited differences in their cell-mediated immune responses to sperm from various men. Thus sperm from different individuals vary in their ability to react with the immune system of sperm-sensitized men or women.     

The detection in human sera of antisperm antibodies reactive with FA-1, an evolutionarily conserved antigen, and with murine spermatozoa

Evolutionarily conserved antigens are present on spermatozoa of several mammalian species. We tested sera from infertile men and women containing antisperm antibodies (ASAs) for their reactivity with FA-1, an antigen known to be present on murine and human spermatozoa. Fifty percent of male sera and 63% of female sera contained anti-FA-1 antibodies, as judged by enzyme linked immunosorbent assay (ELISA). Fourteen percent of male sera and 50% of female sera were also shown to possess ASAs reactive with living mouse spermatozoa, and murine in vitro fertilization was inhibited by human antibodies. These results suggest that the transfer of immunoglobulins from human sera to spermatozoa of other species may provide a model to study how ASAs effect sperm function.     

Detection of autoimmunity to sperm: mixed antiglobulin reaction (MAR) test or sperm agglutination? A study on 537 men from infertile couples

Two different ways of testing for antisperm antibodies were compared: the mixed antiglobulin reaction (MAR) test for demonstration of antibodies of the IgG and IgA classes bound in vivo to the sperm membrane antigens and the gelatin agglutination test for detection of nonbound antisperm antibodies in serum and seminal plasma. Samples from 537 men from infertile couples were investigated. Antibodies bound to the sperm membrane were detected in 49 men (9.1%), IgG in 44 (8.2%), and IgA in 38 cases (7.1%). Sperm agglutinins were recorded in seminal plasma from 30 men (5.6%) and in serum (titer greater than or equal to 16) from 43 men (8.0%). The investigation revealed a very close correlation between the results of MAR testing and the occurrence of sperm agglutinins in serum and seminal plasma. However, if one focuses on antisperm antibodies of the IgA class, which seem to play the major role in male immune infertility, the MAR test offered the advantage that a minor group of patients with pure IgG responses could be distinguished, and rare cases with mainly or exclusively locally produced IgA antibodies could be detected.     

Detection of antisperm antibodies: their localization to human sperm antigens that are transferred to the surface of zona-free hamster oocytes during the sperm penetration assay

The authors have developed an extension of the sperm penetration assay for detecting serum immunoglobulins to sperm antigens that are transferred to the plasma membrane of a sperm-penetrated hamster oocyte. After the hamster oocytes have been scored for sperm penetration by observing for the presence of swollen sperm heads, they are incubated in serum followed by either a 20-minute treatment with rhodamine-conjugated protein A (which binds to most subclasses of IgA, IgG, and IgM) or a 2-hour incubation in guinea pig serum (complement). Positive fluorescence indicates that the serum contains antibodies to sperm antigens that were transferred to the surface of an oocyte during gamete fusion. Complement-mediated lysis indicates that the immunoglobulin that is bound can also fix complement. The advantages of this assay for detection of serum antisperm antibodies are that it is an extension of a widely used assay, is rapid and requires readily available reagents and equipment, can detect most subclasses of IgA, IgG, and IgM, detects antibodies to those sperm antigens that may be transferred to the oocyte during fertilization, and indicates whether the detected antisperm antibodies can mediate complement-dependent lysis of the fertilized oocyte.     

The infertile male--diagnosis

PURPOSE: To discuss a variety of tests used to diagnose the subfertile male and to impart based on clinical experience, reading, and personal research, this editor's view of the relative value of these tests. METHODS: The tests discussed include motile density, sperm morphology, the hypo-osmotic swelling test, antisperm antibodies, sperm chromatin structure assay, DNA integrity tests, reactive oxygen species, sperm penetration assay, sperm-zona pellucida binding tests, sperm creatine kinase activity, plasma membrane mannose-ligand receptor assay, and nuclear morphology. RESULTS: Except when extremely low (< 2.5 x 10(6)/ml) motile density does not identify the subfertile male very well. In contrast to other studies, my group's data suggest that neither low normal morphology by WHO standards or strict criteria identify the subfertile male. The best predictor of male subfertility is the hypo-osmotic swelling test when it is < 50%, which does not result in fertilization failure, but implantation failure. A high percentage of sperm coated by antisperm antibodies is very predictive of fertilization failure. CONCLUSIONS: The physician must be careful when concluding that the male is subfertile or fertile based on standard tests of concentration, motility, and especially morphology.     

Studies on biological actions of sperm immobilizing antibody on human fertilization in vitro

Effects of sperm immobilizing antibodies on sperm penetration through human zonae pellucidae have been studied. Exposure of human spermatozoa obtained from fertile donors to seven serum samples with sperm immobilizing antibody impaired sperm penetration completely in six cases and incompletely in one case. During the course of treatment of a patient with circulating sperm immobilizing antibody by means of an in vitro fertilization and embryo transfer program, it was found that fertilization was completely blocked in the presence of the patient's serum, but three matured ova fertilized successfully when umbilical cord serum was used instead of autoserum from the patient. Furthermore, when spermatozoa were exposed to an IgG fraction of sera containing sperm immobilizing antibody, sperm binding and penetration were markedly inhibited. The spermatozoa, preincubated with sperm immobilizing antibody, showed penetrability across the zona pellucida. However, exposure of possibly capacitated sperm to the antibody completely blocked sperm binding to and penetration through the zona pellucida. These results suggest that sperm immobilizing antibodies cause infertility by preventina sperm binding to and penetration through the zona pellucida, possibly by interfering with the step of fertilization beyond sperm capacitation.     

Macrophages and infertility: enhancement of human macrophage-mediated sperm killing by antisperm antibodies

The mechanism by which antisperm antibodies inhibit fertility is not completely understood. Macrophages may play a role in mediating infertility by interacting with sperm and destroying gametes. Experiments were conducted evaluating the effect of antisperm antibody on the phagocytosis and lysis of sperm by human peritoneal macrophages in vitro. Sperm from a fertile man treated with sera from normal men and women or medium alone had 5 to 280 molecules of IgG/sperm, as determined by a 125I-labeled anti-human IgG monoclonal antibody assay. By contrast, sperm treated with sera containing antisperm antibodies had 310 to 1240 molecules of IgG/sperm. Peritoneal macrophages harvested from infertile women with tubal/adhesive problems mediated phagocytosis and lysis of 111In-labeled sperm which was enhanced by treatment of the sperm with sera containing antisperm antibodies (39.0% +/- 1.5% versus 76.3% +/- 3.2% phagocytosis, and 3.3% +/- 0.3% versus 23.3% +/- 2.3% lysis of sperm [control versus antibody-treated]). The likelihood of fertilization in couples with antisperm antibody may be determined not only by the antibody but also by the presence of genital tract macrophages capable of destroying the antibody-coated sperm.     

Occurrence of serum antisperm antibodies in patients with cystic fibrosis

OBJECTIVE: To determine if acquired obstruction of the vas deferens in men with cystic fibrosis (CF) induced the development of antisperm antibodies with genital tract obstruction similar to other men. DESIGN: Serum antisperm antibodies were assayed by an indirect immunobead test and an indirect immunofluorescence assay. Both homologous (human sperm/human zona) and heterologous (human sperm/zona-free hamster ova) sperm/egg interactions were evaluated in the presence of serum antisperm antibodies from patients with CF. SETTING: Cystic Fibrosis Clinic at the University of Oklahoma Health Sciences Center, a tertiary care referral center. PATIENTS: Fifteen CF patients (10 male and 5 female), 3 non-CF antisperm antibody-positive infertile patients (2 male and 1 female), 20 fertile controls (7 males and 13 females), and 9 fertile sperm donors were used. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Serum antisperm antibody levels in patients with CF. In those patients with antisperm antibodies, determine effect of these sperm antibodies on sperm/egg interactions and complement-mediated events. RESULTS: Sera from 3 (30%) of 10 men with CF demonstrated immunoglobulin (Ig)G, IgA, and/or IgM antisperm antibodies, whereas sera from all 5 CF women and the 20 control sera were negative for antisperm antibodies. The maximal titers for IgG, IgA, and IgM antisperm antibody were 1:8, 192, 1:256, and 1:64, respectively. The immunobead binding, which was restricted to the sperm head and tail-tip or the midpiece and tail-tip, correlated with the indirect immunofluorescence pattern. Antisperm antibody-positive sera from men with CF impaired both the binding and penetration of human zonae and the penetration of hamster ova by human sperm. CONCLUSIONS: Similar to other men with congenital or acquired obstruction of their genital tract, antisperm antibodies may occur in some men with CF. Antisperm antibodies may contribute to immune sperm dysfunction in some men with CF by activated complement-mediated events and interfering with sperm/egg interactions.     

A new look at antifertility vaccines

This article reviews new advances in biochemistry, biotechnology, and immunology relevant to antifertility vaccine development and evaluates the current status and future prospects of contraceptive vaccines and other immunologic approaches to fertility regulation. Contraceptive vaccine candidates include human chorionic gonadotropin, human luteinizing hormone and luteinizing hormone releasing hormone, and reproductive steroid hormones. Sperm enzymes are attractive for a contraceptive vaccine; among the sperm antigens studied are antibodies to hyaluronidase, acrosin, and lactate dehydrogenase-C4. Several laboratories have developed monoclonal antibodies to a variety of sperm antigens and are using them to identify and characterize new sperm proteins and their roles in fertility. Considerable progress has been made toward biochemical characterization of unique glycoproteins constituting the zona pellucida. Zona pellucida antigens are good candidates because antizona antibodies may block both fertilization and implantation, and low amounts of antibody would be sufficient because of the small number of mature eggs with zona present at any time. Studies are underway to identify human embryonic antigens through examination of the protein profile of human teratocarcinoma cell lines at various stages of differentiation and through analysis of antibodies in human pregnancy and infertility sera. Placental and extraembryonic membranes produce several tissue-specific antigens that have been considered for antifertility vaccines, but concern that they could produce late or incomplete abortion has prevented their serioud consideration. Because of possibly serious systemic side effects, presence of the blood-testis barrier, and large number of sperm produced daily, it is unlikely that sperm vaccines can be safely administered to men. Nautural protective mechanisms will probably render some immunocontraceptive approaches ineffective. The possibility of serious pathogenic side effects of contraceptive vaccines demands vaccines demands a cautious approach to their development.     

Blocking of human fertilization in vitro by sera with sperm-immobilizing antibodies

Serum samples with sperm-immobilizing antibody activity from six women were examined for ability to block sperm-egg interaction by a zona penetration test where human follicular ova matured in vitro were used. Exposure of spermatozoa from a fertile healthy donor to the sera impaired binding to and penetration through the zona pellucida of the spermatozoa completely in five cases and incompletely in one case. Successful fertilization in vitro was achieved by using fetal cord serum instead of autoserum of the patient included in the in vitro fertilization and embryo transfer program. These results suggest that interference with sperm-egg interaction may be an additional mechanism of infertility that is caused by antisperm antibodies.     

Antisperm antibodies to sperm surface antigens in women with genital tract infection

Antisperm antibodies to sperm surface antigens in nulligravid women with primary upper genital tract infections were measured by the sperm mixed agglutination reaction assay. As many as 56% of women with a primary episode of pelvic inflammatory disease had antisperm antibodies. In addition, 69% of those women with no history of genital tract infection but with laparoscopic evidence of past pelvic infection had significant levels of circulating antisperm antibodies. Electroimmunoblots of sperm preparations probed with the sera of women who had either known or presumed upper genital tract infection revealed a uniformly recognized 69 kd antigen. In contrast, women with circulating antisperm antibodies before primary upper genital tract infection recognized up to five distinct sperm antigen determinants of 27, 54, 131, 146, and 174 kd. It is a distinct possibility that genital tract infections may lead to immunopotentiation of antisperm antibodies that could affect fertility.