New insights into the origin, structure and role of CD52: a major component of the mammalian sperm glycocalyx

Advanced Sperm Selection Techniques for Assisted Reproduction

Male infertility accounts for approximately 40% of infertility cases. There are many causes of male infertility, including environmental factors, age, lifestyle, infections, varicocele, and cancerous pathologies. Severe oligozoospermia, cryptozoospermia, and azoospermia (obstructive and non-obstructive) are identified as severe male factor infertility, once considered conditions of sterility. Today, in vitro fertilization (IVF) techniques are the only treatment strategy in cases of male factor infertility for which new methodologies have been developed in the manipulation of spermatozoa to achieve fertilization and increase success rates. This review is an update of in vitro manipulation techniques, in particular sperm selection, emphasizing clinical case-specific methodology. The success of an IVF process is related to infertility diagnosis, appropriate choice of treatment, and effective sperm preparation and selection. In fact, selecting the best spermatozoa to guarantee an optimal paternal heritage means increasing the blastulation, implantation, ongoing pregnancy and live birth rates, resulting in the greater success of IVF techniques.

CD52 and OXPHOS-potential targets in ibrutinib-treated mantle cell lymphoma

Altered features of tumor cells acquired across therapy can result in the survival of treatment-resistant clones that may cause minimal residual disease (MRD). Despite the efficacy of ibrutinib in treating relapsed/refractory mantle cell lymphoma, the obstacle of residual cells contributes to relapses of this mature B-cell neoplasm, and the disease remains incurable. RNA-seq analysis of an ibrutinib-sensitive mantle cell lymphoma cell line following ibrutinib incubation of up to 4 d, corroborated our previously postulated resistance mechanism of a metabolic switch to reliance on oxidative phosphorylation (OXPHOS) in surviving cells. Besides, we had shown that treatment-persisting cells were characterized by increased CD52 expression. Therefore, we hypothesized that combining ibrutinib with another agent targeting these potential escape mechanisms could minimize the risk of survival of ibrutinib-resistant cells. Concomitant use of ibrutinib with OXPHOS-inhibitor IACS-010759 increased toxicity compared to ibrutinib alone. Targeting CD52 was even more efficient, as addition of CD52 mAb in combination with human serum following ibrutinib pretreatment led to rapid complement-dependent-cytotoxicity in an ibrutinib-sensitive cell line. In primary mantle cell lymphoma cells, a higher toxic effect with CD52 mAb was obtained, when cells were pretreated with ibrutinib, but only in an ibrutinib-sensitive cohort. Given the challenge of treating multi-resistant mantle cell lymphoma patients, this work highlights the potential use of anti-CD52 therapy as consolidation after ibrutinib treatment in patients who responded to the BTK inhibitor to achieve MRD negativity and prolong progression-free survival.

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.

Impact of Segmented Magnetization on the Flagellar Propulsion of Sperm-Templated Microrobots

Technical design features for improving the way a passive elastic filament produces propulsive thrust can be understood by analyzing the deformation of sperm-templated microrobots with segmented magnetization. Magnetic nanoparticles are electrostatically self-assembled on bovine sperm cells with nonuniform surface charge, producing different categories of sperm-templated microrobots. Depending on the amount and location of the nanoparticles on each cellular segment, magnetoelastic and viscous forces determine the wave pattern of each category during flagellar motion. Passively propagating waves are induced along the length of these microrobots using external rotating magnetic fields and the resultant wave patterns are measured. The response of the microrobots to the external field reveals distinct flow fields, propulsive thrust, and frequency responses during flagellar propulsion. This work allows predictions for optimizing the design and propulsion of flexible magnetic microrobots with segmented magnetization.

Regulation of Monocyte Adhesion and Type I Interferon Signaling by CD52 in Patients With Systemic Sclerosis

OBJECTIVE

Systemic sclerosis (SSc) is characterized by dysregulation of type I interferon (IFN) signaling. CD52 is known for its immunosuppressive functions in T cells. This study was undertaken to investigate the role of CD52 in monocyte adhesion and type I IFN signaling in patients with SSc.

METHODS

Transcriptome profiles of circulating CD14+ monocytes from patients with limited cutaneous SSc (lcSSc), patients with diffuse cutaneous SSc (dcSSs), and healthy controls were analyzed by RNA sequencing. Levels of CD52, CD11b/integrin αΜ, and CD18/integrin β2 in whole blood were assessed by flow cytometry. CD52 expression was analyzed in relation to disease phenotype (early, lcSSc, dcSSc) and autoantibody profiles. The impact of overexpression, knockdown, and antibody blocking of CD52 was analyzed by gene and protein expression assays and functional assays.

RESULTS

Pathway enrichment analysis indicated an increase in adhesion- and type I IFN-related genes in monocytes from SSc patients. These cells displayed up-regulated expression of CD11b/CD18, reduced expression of CD52, and enhanced adhesion to intercellular adhesion molecule 1 and endothelial cells. Changes in CD52 expression were consistent with the SSc subtypes, as well as with immunosuppressive treatments, autoantibody profiles, and monocyte adhesion properties in patients with SSc. Overexpression of CD52 led to decreased levels of CD18 and monocyte adhesion, while knockdown of CD52 increased monocyte adhesion. Experiments with the humanized anti-CD52 monoclonal antibody alemtuzumab in blood samples from healthy controls increased monocyte adhesion and CD11b/CD18 expression, and enhanced type I IFN responses. Monocytic CD52 expression was up-regulated by interleukin-4 (IL-4)/IL-13 via the STAT6 pathway, and was down-regulated by lipopolysaccharide and IFNs α, β, and γ in a JAK1 and histone deacetylase IIa (HDAC IIa)-dependent manner.

CONCLUSION

Down-regulation of the antiadhesion CD52 antigen in CD14+ monocytes represents a novel mechanism in the pathogenesis of SSc. Targeting of the IFN-HDAC-CD52 axis in monocytes might represent a new therapeutic option for patients with early SSc.

CD52 glycan binds the proinflammatory B box of HMGB1 to engage the Siglec-10 receptor and suppress human T cell function

Inflammation is a protective response of the body’s immune system against harmful stimuli such as pathogenic microorganisms, toxins, or damaged cells. However, if excessive or prolonged, inflammation may be harmful and therefore has to be regulated. Soluble CD52 is a natural sialoglycopeptide and immune regulator that suppresses inflammatory responses. We elucidated the mechanism of this effect by showing that soluble CD52 first sequesters a mediator of inflammation called HMGB1; in turn, this promotes binding of the sialylated CD52 glycan to an inhibitory receptor, sialic acid-binding immunoglobulin-like lectin (Siglec)-10, present on activated T cells and other immune cells. This concerted antiinflammatory mechanism driven by soluble CD52 may contribute to immune-inflammatory homeostasis and underscores the therapeutic potential of soluble CD52.

CD52, a glycophosphatidylinositol (GPI)-anchored glycoprotein, is released in a soluble form following T cell activation and binds to the Siglec (sialic acid-binding Ig-like lectin)-10 receptor on T cells to suppress their function. We show that binding of CD52-Fc to Siglec-10 and T cell suppression requires the damage-associated molecular pattern (DAMP) protein, high-mobility group box 1 (HMGB1). CD52-Fc bound specifically to the proinflammatory Box B domain of HMGB1, and this in turn promoted binding of the CD52 N-linked glycan, in α-2,3 sialic acid linkage with galactose, to Siglec-10. Suppression of T cell function was blocked by anti-HMGB1 antibody or the antiinflammatory Box A domain of HMGB1. CD52-Fc induced tyrosine phosphorylation of Siglec-10 and was recovered from T cells complexed with HMGB1 and Siglec-10 in association with SHP1 phosphatase and the T cell receptor (TCR). Thus, soluble CD52 exerts a concerted immunosuppressive effect by first sequestering HMGB1 to nullify its proinflammatory Box B, followed by binding to the inhibitory Siglec-10 receptor, triggering recruitment of SHP1 to the intracellular immunoreceptor tyrosine-based inhibitory motif of Siglec-10 and its interaction with the TCR. This mechanism may contribute to immune-inflammatory homeostasis in pathophysiologic states and underscores the potential of soluble CD52 as a therapeutic agent.

A Mouse Model for Dietary Xenosialitis: ANTIBODIES TO XENOGLYCAN CAN REDUCE FERTILITY

Humans can incorporate the xenoglycan N-glycolylneuraminic acid (Neu5Gc) from the diet into reproductive tissues and secretions. Most humans also have circulating antibodies specific for this dietary xenoglycan. The potential for inflammation induced by incorporated Neu5Gc and circulating anti-Neu5Gc antibodies, termed xenosialitis, has been discussed as a factor influencing several human diseases. Potential effects of xenosialitis on human fertility remain unknown. Here, we investigate possible adverse effects of the presence of Neu5Gc on sperm or endometrium combined with anti-Neu5Gc antibodies in semen or uterine secretions in a mouse model. We use Cmah(-/-) mice, humanized for Neu5Gc deficiency. We find that the viability, migration, and capacitation of sperm with incorporated Neu5Gc are negatively affected when these are exposed to anti-Neu5Gc antibodies. In addition, we find that after copulation, activated uterine neutrophils and macrophages show increased phagocytosis of sperm in the presence of anti-Neu5Gc antibodies via the complement receptor 3 (C3R) and Fcγ I/II/III (Fc receptor). Furthermore, Neu5Gc in endometrial cells combined with the presence of anti-Neu5Gc antibodies alters the receptivity and decidualization of endometrial explants. These studies provide mechanistic insights on how Neu5Gc on sperm and/or endometrium combined with anti-Neu5Gc antibodies in semen and uterine fluid might contribute to unexplained human infertility.

Optimization of microelectrophoresis to select highly negatively charged sperm

PURPOSE

The sperm membrane undergoes extensive surface remodeling as it matures in the epididymis. During this process, the sperm is encapsulated in an extensive glycocalyx layer, which provides the membrane with its characteristic negative electrostatic charge. In this study, we develop a method of microelectrophoresis and standardize the protocol to isolate sperm with high negative membrane charge.

METHODS

Under an electric field, the percentage of positively charged sperm (PCS), negatively charged sperm (NCS), and neutrally charged sperm was determined for each ejaculate prior to and following density gradient centrifugation (DGC), and evaluated for sperm DNA damage, and histone retention. Subsequently, PCS, NCS, and neutrally charged sperm were selected using an ICSI needle and directly analyzed for DNA damage.

RESULTS

When raw semen was analyzed using microelectrophoresis, 94 % were NCS. In contrast, DGC completely or partially stripped the negative membrane charge from sperm resulting PCS and neutrally charged sperm, while the charged sperm populations are increased with an increase in electrophoretic current. Following DGC, high sperm DNA damage and abnormal histone retention were inversely correlated with percentage NCS and directly correlated with percentage PCS. NCS exhibited significantly lower DNA damage when compared with control (P < 0.05) and PCS (P < 0.05). When the charged sperm population was corrected for neutrally charged sperm, sperm DNA damage was strongly associated with NCS at a lower electrophoretic current.

CONCLUSION

The results suggest that selection of NCS at lower current may be an important biomarker to select healthy sperm for assisted reproductive treatment.

Potential Use of Antimicrobial Peptides as Vaginal Spermicides/Microbicides

The concurrent increases in global population and sexually transmitted infection (STI) demand a search for agents with dual spermicidal and microbicidal properties for topical vaginal application. Previous attempts to develop the surfactant spermicide, nonoxynol-9 (N-9), into a vaginal microbicide were unsuccessful largely due to its inefficiency to kill microbes. Furthermore, N-9 causes damage to the vaginal epithelium, thus accelerating microbes to enter the women's body. For this reason, antimicrobial peptides (AMPs), naturally secreted by all forms of life as part of innate immunity, deserve evaluation for their potential spermicidal effects. To date, twelve spermicidal AMPs have been described including LL-37, magainin 2 and nisin A. Human cathelicidin LL-37 is the most promising spermicidal AMP to be further developed for vaginal use for the following reasons. First, it is a human AMP naturally produced in the vagina after intercourse. Second, LL-37 exerts microbicidal effects to numerous microbes including those that cause STI. Third, its cytotoxicity is selective to sperm and not to the female reproductive tract. Furthermore, the spermicidal effects of LL-37 have been demonstrated in vivo in mice. Therefore, the availability of LL-37 as a vaginal spermicide/microbicide will empower women for self-protection against unwanted pregnancies and STI.

Lectin binding of human sperm associates with DEFB126 mutation and serves as a potential biomarker for subfertility

Coating on the sperm surface, glycocalyx, plays a key role in sperm motility, maturation and fertilization. A comprehensive profile of sperm surface glycans will greatly facilitate both basic researches and clinical studies. Because of the capability of recognizing different glycan moieties, lectins are widely used in glycobiology. However, lacking high-throughput technology, limited lectins have been reported for analyzing the glycan of human sperm. In this study, we employed a lectin microarray for profiling the surface glycans of human sperm, on which 54 out of 91 lectins showed positive binding. Based on this technique, we compared lectin binding profiling of sperm with homozygous DEFB126 mutation (del/del) with that of wild type (wt/wt). DEFB126 was reported to contribute to the sialylation on sperm surface and its homozygous mutation was related to male subfertility. Six lectins (Jacalin/AIA, GHA, ACL, MPL, VVL and ABA) were found to develop lower binding affinity to sperm with del/del. Further validation showed that these lectins, especially ABA and MPL, can be potential biomarkers for clinical diagnosis of subfertility due to the mutation of DEFB126. Our research provides insight into the detection of some unexplained male subfertility, and the lectin microarray is generally applicable for infertility/subfertility sperm biomarker discovery.

Strategies for preventing mucosal cell-associated HIV transmission

Human immunodeficiency virus (HIV) may be transmitted through either cell-free virions or leukocytes harboring intracellular HIV in bodily fluids. In recent years, the early initiation of combination antiretroviral therapy leading to virological suppression has resulted in decreased HIV transmission to uninfected partners. Additionally, the efficacy of primary chemoprophylaxis with oral or topical antiretroviral regimens containing tenofovir (with or without emtricitabine) has been demonstrated. However, the efficacy of these approaches may be compromised by suboptimal adherence, decreased drug concentrations in mucosal compartments in women, and genital inflammation. Furthermore, in vitro studies on the effects of tenofovir on cell-associated HIV transmission have produced conflicting results. Preclinical studies suggest that combination preventive approaches may be most effective in stopping the transmission of HIV after mucosal exposure. Since the development of antibodies were found to correlate with protection in the only effective HIV vaccine trial, the administration of preformed mucosal and systemic antibodies may inform the development of safe and effective antibody-based oral, topical, and/or systemic preexposure prophylaxis agents and provide guidance in the development of HIV vaccines that effectively block cell-associated HIV transmission.

Glycan evolution in response to collaboration, conflict, and constraint

Glycans, oligo- and polysaccharides secreted or attached to proteins and lipids, cover the surfaces of all cells and have a regulatory capacity and structural diversity beyond any other class of biological molecule. Glycans may have evolved these properties because they mediate cellular interactions and often face pressure to evolve new functions rapidly. We approach this idea two ways. First, we discuss evolutionary innovation. Glycan synthesis, regulation, and mode of chemical interaction influence the spectrum of new forms presented to evolution. Second, we describe the evolutionary conflicts that arise when alleles and individuals interact. Glycan regulation and diversity are integral to these biological negotiations. Glycans are tasked with such an amazing diversity of functions that no study of cellular interaction can begin without considering them. We propose that glycans predominate the cell surface because their physical and chemical properties allow the rapid innovation required of molecules on the frontlines of evolutionary conflict.

Sperm selection based on electrostatic charge

Charge is a fundamental property of all forms of matter that exhibit attraction or repulsion in the presence of another charged particle. This electrokinetic property occurs when the particles exhibiting a net negative or positive charge are subjected to an external electric field that exerts an electrostatic force between them. Sperm surface membranes exhibit varying levels of electrostatic potential that are proportional to the levels of sialic acid residue acquired on the cell surface during maturation. Electrostatic charge-based sperm separation is a recently developed technique that uses an electric field to isolate mature sperm with reduced levels of DNA fragmentation. Two methods for the separation of sperm based on electrostatic charge, the Zeta method and a commercially available electrophoretic method using the SpermSep Cell Sorter 10, are discussed in this chapter including a detailed protocol for sperm separation based on the Zeta method.

The N-linked carbohydrate moiety of male reproductive tract CD52 (mrt-CD52) interferes with the complement system via binding to C1q

Antisperm antibody detected in infertile female patients' sera has been shown to correlate with reduced fertility. The antibody showed strong complement-dependent cytotoxicity as determined by the sperm immobilization test (SIT). CD52 is a human glycosylphosphatidylinositol (GPI)-anchored antigen present in lymphocytes and male reproductive tracts (mrt), including mature sperm and seminal plasma. Recently, purified mrt-CD52 from human seminal plasma has been reported to interfere with the classical complement pathway, but not lectin binding or alternative pathways of the complement system. The purpose of this study is to determine which stage of the classical pathway mrt-CD52 regulates. mrt-CD52 was purified from human seminal plasma or intact sperm membrane. Immunoprecipitation assay was performed with the reaction of mrt-CD52, human complement and mAb H6-3C4. Immunoprecipitate was formed by the carbohydrate moiety of mrt-CD52, but not by the GPI-anchor peptide. The C1q molecule (29 kDa) was detected in the immunoprecipitates by Western blotting analysis probed with anti C1q antibody, indicating that the carbohydrate moiety of mrt-CD52 binds to C1q. Also, the complement-dependent SIT revealed that purified CD52 inhibited sperm immobilization activity by antisperm antibody. These results suggest that mrt-CD52 protects sperm function from complement attack if antisperm antibody is generated in the female reproductive tracts.

Sperm preparation: state-of-the-art--physiological aspects and application of advanced sperm preparation methods

For assisted reproduction technologies (ART), numerous techniques were developed to isolate spermatozoa capable of fertilizing oocytes. While early methodologies only focused on isolating viable, motile spermatozoa, with progress of ART, particularly intracytoplasmic sperm injection (ICSI), it became clear that these parameters are insufficient for the identification of the most suitable spermatozoon for fertilization. Conventional sperm preparation techniques, namely, swim-up, density gradient centrifugation and glass wool filtration, are not efficient enough to produce sperm populations free of DNA damage, because these techniques are not physiological and not modeled on the stringent sperm selection processes taking place in the female genital tract. These processes only allow one male germ cell out of tens of millions to fuse with the oocyte. Sites of sperm selection in the female genital tract are the cervix, uterus, uterotubal junction, oviduct, cumulus oophorus and the zona pellucida. Newer strategies of sperm preparation are founded on: (i) morphological assessment by means of 'motile sperm organelle morphological examination (MSOME)'; (ii) electrical charge; and (iii) molecular binding characteristics of the sperm cell. Whereas separation methods based on electrical charge take advantage of the sperm's adherence to a test tube surface or separate in an electrophoresis, molecular binding techniques use Annexin V or hyaluronic acid (HA) as substrates. Techniques in this category are magnet-activated cell sorting, Annexin V-activated glass wool filtration, flow cytometry and picked spermatozoa for ICSI (PICSI) from HA-coated dishes and HA-containing media. Future developments may include Raman microspectrometry, confocal light absorption and scattering spectroscopic microscopy and polarization microscopy.

Snake venoms as a source of compounds modulating sperm physiology: Secreted phospholipases A2 from Oxyuranus scutellatus scutellatus impact sperm motility, acrosome reaction and in vitro fertilization in mice

The goal of this study was to identify new compounds from venoms able to modulate sperm physiology and more particularly sperm motility. For this purpose, we screened the effects of 16 snake venoms cleared of molecules higher than 15 kDa on sperm motility. Venoms rich in neurotoxins like those from Oxyuranus scutellatus scutellatus or Daboia russelii, were highly potent inhibitors of sperm motility. In contrast, venoms rich in myotoxins like those from Echis carinatus, Bothrops alternatus and Macrovipera lebetina, were inactive. From the main pharmacologically-active fraction of the Taipan snake O. scutellatus s., a proteomic approach allowed us to identify 16 different proteins, among which OS1 and OS2, two secreted phospholipases A2 (sPLA(2)). Purified OS1 and OS2 mimicked the inhibitory effect on sperm motility and were likely responsible for the inhibitory effect of the active fraction. OS1 and OS2 triggered sperm acrosome reaction and induced lipid rearrangements of the plasma membrane. The catalytic activity of OS2 was required to modulate sperm physiology since catalytically inactive mutants had no effect. Finally, sperm treated with OS2 were less competent than control sperm to initiate in vitro normal embryo development. This is the first report characterizing sPLA(2) toxins that modulate in vitro sperm physiology.

Lectin-binding sites on ejaculated stallion sperm during breeding and non-breeding periods

Stallion sperm from semen collected in Southern Italy during the breeding (June-July) and non-breeding (December-January) periods were analyzed by means of twelve lectins to evaluate the glycoconjugate pattern and to verify whether there are any seasonal differences in the glycosylation pattern of the sperm glycocalyx. The acrosomal cap showed reactivity for Maackia amurensis (MAL II), Sambucus nigra (SNA), Arachis hypogaea (PNA), Glycine max (SBA), Helix pomatia (HPA), Canavalia ensiformis (Con A) Triticum vulgaris (WGA), and Griffonia simplicifolia isolectin II (GSA II) in breeding and non-breeding ejaculated sperm, suggesting the presence of oligosaccharides terminating with Neu5Ac alpha 2,3Gal beta 1,4GlcNAc, Neu5Ac alpha 2,6Gal/GalNAc, with Gal beta 1,3GalNAc, alpha/beta GalNAc and glycans with terminal/internal alpha Man and GlcNAc. During the non-breeding period, the acrosomal cap expressed oligosaccharides terminating with Gal beta 1,4GlcNAc (Ricinus communis(120) affinity) (RCA(120)) and L-Fuc alpha 1,2Gal beta 1,4GlcNAc beta (Ulex europaeus affinity) (UEA I). The equatorial segment placed between the acrosomal cap and post-acrosomal region did not display glycans terminating with GalNAc, GlcNAc, and alpha L-Fuc. The post-acrosomal region of sperm collected in the breeding and non-breeding periods bound Con A, MAL II, SNA, and SBA, thus showing the presence of N-linked oligosaccharides from high-Man content, terminating with Neu5Ac alpha 2,3Gal beta 1,4GlcNAc, Neu5Ac alpha 2,6Gal/GalNAc and GalNAc. In winter, the post-acrosomal region also expressed oligosaccharides terminating with alpha GalNAc, GlcNAc, and L-Fuc alpha 1,2Gal beta 1,4GlcNAc beta (HPA, GSA II, and UEA I staining). The tail of sperm from semen collected during the breeding and non-breeding periods showed a lectin binding pattern similar to the post-acrosomal region, except for the absence of HPA staining in sperm collected during the winter season. These results indicate that the surface of stallion sperm contains different glycocalyx domains and that the glycosylation pattern undergoes changes during the breeding and non-breeding periods.

The GPI-anchored CD52 antigen of the sperm surface interacts with semenogelin and participates in clot formation and liquefaction of human semen

CD52 is a human glycosylphosphatidylinositol (GPI)-anchored antigen exclusively expressed in leukocytes and epididymal cells. It is also present in sperm, being inserted in their plasma membrane as they pass through the epididymis. In a previous paper we identified a new CD52 form without GPI anchor by fast performance liquid chromatography (FPLC) fractionation of semen components. The form has a lower negative charge than the GPI-anchored form and occurs as the only CD52 form in prostasome-free seminal plasma. It was also found associated with the ejaculated sperm, but in contrast to the GPI-anchored one, it is lost during the capacitation process. In this paper we indicate that (1) the GPI-anchored CD52 of the sperm surface serves as receptor for semenogelin I during clot formation, (2) liquefaction involves cleavage of the GPI anchor from certain CD52 molecules, releasing sperm from the clot and the soluble antigen bound to semenogelin fragments into the seminal plasma and (3) the clot is a sponge-like structure housing sperm. Soluble CD52 was immunopurified from the soluble CD52-containing FPLC fraction using CAMPATH-1G and was found to be complexed with a semenogelin-derived peptide of the carboxyl terminal portion of semenogelin I, having the sequence SQTEKLVAGKQI and starting from amino acid 376. Immunoprecipitation and immunoblot analyses using CAMPATH-1G and anti-semenogelin as immunoprecipitating antibodies and anti-gp20 and anti-semenogelin as immunoblot detectors of the corresponding antigens, confirmed that the soluble CD52 formed a complex with semenogelin. The semenogelin-CD52 soluble form was found to be a direct consequence of the liquefaction process since only the GPI-anchored CD52 was recovered in uniquefied semen after recovering sperm and seminal plasma by urea solubilization of the clot.

A new sensitive enzyme-linked immunosorbent assay (ELISA) for Alemtuzumab determination: development, validation and application

Alemtuzumab is a humanized (IgG(1)) rat monoclonal antibody to CD52 antigen and is currently used in the treatment of chronic lymphocytic leukemia (CLL) and other CD52-positive lymphoproliferative disorders. Various techniques have been developed to measure Alemtuzumab levels in human serum/plasma. The authors report on the validation of a very sensitive enzyme-linked immunosorbent assay (ELISA) to measure serum concentrations of the humanized IgG(1) using a rabbit polyclonal antibody specifically produced against the rat sequence of Alemtuzumab after papain digestion. The assay was successfully applied to test the serum samples of patients with B-lymphocyte CLL who received Alemtuzumab subcutaneously. This ELISA assay could be easily used to determine human serum levels of Alemtuzumab pre- and post-treatment to optimize dosing and scheduling and to study the relationship between dose and clinical response.

The sperm agglutination antigen-1 (SAGA-1) glycoforms of CD52 are O-glycosylated

CD52 is composed of a 12 amino acid peptide with N-linked glycans bound to the single potential glycosylation site at position 3, and a glycosylphosphatidylinositol-anchor attached at the C-terminus. Some glycoforms of this molecule expressed in the male reproductive tract are recognized by complement-dependent sperm-immobilizing antibodies in infertile patients making this antigen an important target for immunocontraception and fertility studies. Although the amount of posttranslational modification is already remarkable for such a small polypeptide, O-glycosylation of CD52 has additionally been implicated by several studies, but never rigorously characterized. In this report, we show clear evidence for the presence of O-glycans in CD52 preparations immunopurified using the murine S19 monoclonal antibody generated against sperm agglutination antigen-1 (SAGA-1), a male reproductive tract specific form of CD52. The O-glycans have been characterized by MALDI-TOF and tandem mass spectrometry after reductive elimination and permethylation. The data indicate that the major SAGA-1 O-glycans are core 1 and 2 mucin-type structures, with and without sialic acid (NeuAc(0-2)Hex(1-3)HexNAc(1-2)HexNAcitol). Minor fucosy- lated O-glycans are also present including some struc- tures with putative Le(y) epitopes (NeuAc(0-1)Fuc(1-3)Hex(1-2) HexNAc(0-1)HexNAcitol). Analysis of O-glycopeptides by tandem mass spectrometry provided an additional level of support for the O-glycosylation of SAGA-1. Elucidation of the O-glycosylation of SAGA-1 adds to the complexity of this molecule and may help to explain its biological activity.

Biochemical property and immunogenicity of mouse male reproductive tract CD52 (mrt-CD52)

Male reproductive tract CD52 (mrt-CD52) is known to be a pathogenic antigen for immunological infertility. Although human CD52 has been extensively investigated, the properties of mouse CD52 are not well elucidated. This study was conducted, therefore, to examine the tissue distribution, molecular composition and immunogenicity of mouse mrt-CD52. Immunohistological studies with an antibody to a synthetic peptide showed that mouse CD52 was localized mainly in the cauda epididymis and vas deferens, but not in the testis, liver, kidney or spleen. The molecule was composed of Asn (N)-linked and The/Ser (O)-linked carbohydrates as well as a glycosylphosphatidyl (GPI) anchor portion. Purified mrt-CD52 preparations produced antibodies by subcutaneous and intranasal immunization in both male and female mice. These antisera showed sperm-immobilizing activities with complement to mouse sperm. The research indicated mouse CD52 had similar biochemical and immunological properties to human CD52. This animal experiment is a good model for investigating human mrt-CD52 antibody detected in infertile patients.

Clinical relevance of sperm DNA damage in assisted reproduction

Many studies have shown how a 'paternal effect' can cause repeated assisted reproduction failures. In particular, with increasing experience of intracytoplasmic sperm injection (ICSI), it became evident that spermatozoa from some patients repeatedly fail to form viable embryos, although they can fertilize the oocyte and trigger early preimplantation development. Many authors have shown how this paternal effect can be traced back to anomalies in sperm chromatin organization: the spermatozoa of subfertile men are characterized by numerical abnormalities in spermatozoal chromosome content, Y chromosome microdeletions, alterations in the epigenetic regulation of paternal genome and non-specific DNA strand breaks. In particular, pathologically increased sperm DNA fragmentation is one of the main paternal-derived causes of repeated assisted reproduction failures in the ICSI era. The intention of this review is to describe nuclear sperm DNA damage, with emphasis on its clinical significance and its relationship with male infertility. Assessment of sperm DNA damage appears to be a potential tool for evaluating semen samples prior to their use in assisted reproduction, helping to select spermatozoa with intact DNA or with the least amount of DNA damage for use in assisted conception.

First recorded pregnancy and normal birth after ICSI using electrophoretically isolated spermatozoa

BACKGROUND

DNA damage in the male germ line is associated with poor fertilization and cleavage rates, impaired embryo quality and early pregnancy loss. Given these associations, embryologists are keen to develop techniques that will allow the selection of viable spermatozoa exhibiting low levels of DNA damage for assisted conception purposes.

METHODS

In this article, we describe a novel electrophoretic approach for the rapid isolation of cells possessing little DNA damage. The limits of the method were examined using cryostored and snap-frozen semen samples as well as testicular biopsy material. In addition, clinical utility was demonstrated in a case study involving treatment of a patient exhibiting persistently high levels of DNA damage in his spermatozoa.

RESULTS

From a range of difficult starting materials (biopsies, cryostored semen and snap-frozen sperm suspensions), the electrophoretic system rapidly isolated populations of motile, viable, morphologically normal spermatozoa exhibiting high levels of DNA integrity. Clinical application in a couple suffering from long-term infertility associated with extensive DNA damage in the male germ line led to the first human pregnancy following such electrophoretic sperm isolation.

CONCLUSIONS

The electrophoretic procedure holds promise as a convenient method for the rapid preparation of high-quality spermatozoa for assisted conception purposes.

Antigenic epitope for sperm-immobilizing antibody detected in infertile women

CD52 is a glycosylphosphatidylinositol (GPI) anchor protein occurring in lymphocytes, the epididymis, seminal plasma and on ejaculated sperm surface. The molecular structure of male reproductive tract CD52 (mrtCD52) is quite different from that of lymphocyte CD52 except for a peptide sequence comprising 12 amino acids. The carbohydrate molecule may thus provide antigenic epitopes to females. The repeated N-acetyllactosamine units of the N-linked carbohydrate present in the mrtCD52 were identified as a pathogenic antigen for infertility using a monoclonal antibody (MAb H6-3C4) generated from an infertile patient's peripheral blood lymphocyte. We suggested also the possible presence of O-linked carbohydrate in human mrtCD52, although it is not known whether this carbohydrate is immunogenic or not. This article gives an overview of the structure and function of mrtCD52 as well as the fertilization-blocking mechanism of the antibody against this molecule.

Spermadhesin AQN1 is a candidate receptor molecule involved in the formation of the oviductal sperm reservoir in the pig

Sperm are stored in the isthmic region of the oviduct under conditions that maintain viability and suppress early capacitation steps until ovulation occurs. The initial contact between sperm and oviductal epithelium is mediated by carbohydrate-protein interactions. In the pig, the carbohydrate recognition system has been shown to involve oligomannosyl structures. The spermadhesins AWN and AQN1 are the dominant porcine carbohydrate-binding sperm proteins. The objective of this study was to demonstrate that AQN1 contributes to sperm binding to the oviductal epithelium. AQN1 showed a broad carbohydrate-binding pattern as it recognizes both alpha- and beta-linked galactose as well as Manalpha1-3(Manalpha1-6)Man structures, whereas AWN bound only the galactose species. Binding of ejaculated sperm to oviductal epithelium was inhibited by addition of AQN1 but not by AWN. Mannose-binding sites were localized over the rostral region of the sperm head. Flow cytometry showed that, under capacitating conditions, the population of live sperm was shifted within 30 min toward an increase in the proportion of cells with low mannose- and high galactose-binding. The loss of mannose-binding sites was accompanied by the loss of AQN1 in sperm extracts and the significant reduction in the sperm-oviduct binding. The oviductal epithelium was shown by GNA-lectin histochemistry and by SDS-PAGE and lectin blotting of the apical membrane fraction to express mannose components that could be recognized by AQN1. These results demonstrate that the sperm lectin AQN1 fulfils the criteria for an oviduct receptor in the pig and may play a role in the formation of the oviductal sperm reservoir.

Development of a novel electrophoretic system for the isolation of human spermatozoa

BACKGROUND

Optimization of assisted conception outcomes involves the development of rapid, safe, effective techniques for the isolation of functional human spermatozoa free from significant DNA damage. In this study we describe a novel electrophoretic sperm isolation technique that achieves these objectives.

METHODS

The separation system consisted of a cassette comprising two 400 mul chambers separated by a polycarbonate filter containing 5 micromol/l pores and bounded by a 15 kDa polyacrylamide membrane to allow the free circulation of buffer. Semen was introduced into one chamber, current applied (75 mA at variable voltage) and within seconds a purified suspension of spermatozoa could be collected from the adjacent chamber. These cells were assessed for their count, viability, motility, morphology and DNA integrity.

RESULTS

The suspensions generated by the electrophoretic separation technique contained motile, viable, morphologically normal spermatozoa and exhibited low levels of DNA damage. Moreover, these cell suspensions were free from contaminating cells, including leukocytes. The technique was comparable to discontinuous gradient centrifugation except that it took a fraction of the time and generated cells with significantly less DNA damage.

CONCLUSION

Electrophoretic separation represents a highly effective, novel approach for the isolation of spermatozoa for assisted conception purposes.

Possible presence of O-linked carbohydrate in the human male reproductive tract CD52

Male reproductive tract CD52 (mrtCD52) is an antigen recognized by a complement-dependent sperm-immobilizing monoclonal antibody (SI-Abs) derived in an infertile patient. The molecule has been shown to contain a unique N-linked carbohydrate that does not cross-react with other tissues. In this study, we have investigated whether O-linked carbohydrate as well as N-linked carbohydrate is present in mrtCD52 using specific lectins and anti-CD52 core peptide antiserum. The lectin PNA, which recognizes O-linked carbohydrate [Galbeta1-3GalNAc], reacted with mrtCD52 and showed a similar polymorphic reaction pattern to that of the anti-peptide antiserum in western blotting analysis on two-dimensional SDS-PAGE. The PNA-reactive spots disappeared after removal of O-linked carbohydrate, but not after removal of N-linked carbohydrate. These results suggest that O-linked carbohydrate is present in mrtCD52. The moiety may possibly contribute to a specific antigenic epitope of mrtCD52.

T-cell depleting antibodies: new hope for induction of allograft tolerance in bone marrow transplantation?

Graft versus host disease (GVHD) remains the main barrier to successful allogeneic bone marrow transplant outcomes. Depletion of graft T cells is an effective way of reducing the incidence of acute and chronic GVHD, and a variety of methods have been used to achieve this depletion. Donor CD8+ T cells seem to be the critical effector cells; GVHD is reduced when the depletion process eliminates these cells, but not when CD4 cells are targeted alone. However, despite the successful reduction in GVHD, transplant outcomes are usually inferior with T-cell depleted transplants, because of increased graft failure, infections and relapse. Alternative approaches are needed. In vivo T-cell depletion, using antithymocyte globulin (ATG) as part of the conditioning regimen, seems an attractive option. Pre-transplant ATG lingers in the bone marrow to deplete engrafting donor T cells, but also depletes host T cells to prevent graft rejection and allow de-escalation of the conditioning regimen. It also avoids the need for graft manipulation with its associated costs, need for expertise and CD34+ cell loss. The efficacy of pre-transplant horse ATG remains anecdotal but it has been reported to modestly lower GVHD in single arm studies. Rabbit ATG has been studied in prospective randomised trials. There is evidence of a dose-response effect in reducing GVHD; however, there was no improvement in outcome, because of increased mortality associated with infection. In contrast, pre-transplant alemtuzumab (campath-1H) or an earlier version of this molecule (campath-1G), which target CD52+ cells, do appear to be effective in reducing both acute and chronic GVHD. There is speculation that this is not solely due to the effect of campath on T cells but that it may also be due to the elimination of host antigen-presenting cells (APC), which seem to be important in GVHD pathogenesis. Host APC are more efficient at expressing endogenous and exogenous host antigens on class I MHC to donor CD8+ cells than donor APC, which need to cross-prime exogenous antigen. Campath-1G eliminates host dendritic cells by the time of graft infusion, supporting this as a possible mechanism of action. Pre-transplant alemtuzumab has not yet been studied in a prospective randomised study, and this is required to quantify any benefit on outcome; despite this, published studies do show cause for optimism.

Immortalization by large T-antigen of the adult epididymal duct epithelium

The SV40 large T-antigen has been widely used to convert various cell types to a transformed phenotype, and also to induce progressive tumours in transgenic animals. The objectives of this review are to compare and discuss three different approaches to generate epididymal epithelial cell lines using the large T-antigen. In the first approach, retroviral transfection of primary cultures was used to immortalize canine epididymal cells in vitro; the other two approaches used transgenic mice expressing the large T-antigen. In one of these in vivo approaches, a construct consisting of the coding sequence of a temperature sensitive (ts) SV40 large T-antigen was inserted in a mouse genome. When the cells are exposed to the permissive temperature of 33 degrees C, functional expression of the large T-antigen occurs and cells start to proliferate. In the second in vivo approach a tissue-specific promoter, the 5kb GPX5 promoter, was used to direct expression of the large T-antigen to the epididymal duct epithelium.

Expression of gp20, a human sperm antigen of epididymal origin, is reduced in spermatozoa from subfertile men

gp20, a sialylglycoprotein of human sperm homologous to CD52, is present everywhere on the surface of the freshly ejaculated sperm but is prevalently localized in the equatorial region of the head of capacitated sperm. In the present study, we confirmed this feature on large scale and correlated equatorial exposure of the antigen to the presence of serum albumin (SA) in the capacitation medium. Furthermore, we analyzed the relationship between the presence of the antigen and its equatorial exposure after capacitation and fertility, by comparing immunostaining for gp20 in the motile fraction of spermatozoa from fertile and subfertile men. A significantly higher percentage of nonimmunostained spermatozoa before capacitation (38.5% +/- 23 vs. 12% +/- 7, P < 0.0001) and a lower increase in the percentage of sperm with equatorial localization after capacitation (19.3% +/- 25 vs. 34.6% +/- 22, P = 0.039) were observed in subfertile men (n = 60) compared to fertile men (n = 15). In the whole study group, a positive correlation was also found between the percentage of spermatozoa exhibiting equatorial localization in capacitated samples and normal head forms (R = 0.50; P < 0.0001).

Circulating CD20 and CD52 in patients with non-Hodgkin's lymphoma or Hodgkin's disease

The cell surface proteins CD20 and CD52 differ significantly in their structures and are expressed on the majority of B cells. Both circulating CD20 (cCD20) and circulating CD52 (cCD52) have been recently documented in patients with chronic lymphocytic leukaemia. A retrospective study to establish whether cCD20 and/or cCD52 were detectable in patients with lymphoma, and the clinical associations of these soluble antigens if detected, was conducted. cCD20 and cCD52 levels were analysed in a cohort of 65 patients with non-Hodgkin's lymphoma (NHL) and 37 with Hodgkin's disease (HD). Patients with NHL had elevated pretherapy levels of cCD20 and cCD52 compared with normal individuals. Patients with HD had significantly lower than normal pretherapy levels of both cCD20 and cCD52. cCD20 levels were marginally elevated post-therapy in NHL patients while in patients with HD, cCD20 levels remained significantly lower than normal after therapy. Serum cCD52 levels became significantly lower than normal post-therapy in NHL patients, and remained significantly lower than normal in HD patients. No predictive effects were found for pretherapy or post-therapy levels of cCD52 on survival for either cohort of patients. Post-therapy cCD20 levels independently highly correlated with survival in patients with NHL. Prospective evaluation will be required to establish if cCD20 and cCD52 may be used as biomarkers in the diagnosis, prognostic categorization, and monitoring of the clinical course in patients with lymphoma. The clinical significance of circulating antigen in patients receiving monoclonal antibody therapy directed against CD20 and/or CD52 warrants study.

Nasal immunization with diphtheria toxoid conjugated-CD52 core peptide induced specific antibody production in genital tract of female mice

PROBLEM

The common mucosal immune system (CMIS) has developed as a barrier for the numerous encounters between the host and various pathogens. It is possible to exploit this system to induce secretion of IgA antibody which inhibits sperm penetration in the female genital tract. In this study, the immunogenicity of a human sperm surface antigen (CD52) introduced by intranasal immunization was investigated with a view to developing a contraceptive vaccine.

METHOD OF STUDY

A synthetic peptide corresponding to CD52 core peptide (GQNDTSQTSSPS) was prepared and conjugated with diphtheria toxoid (DT) as a carrier protein. The immunogen was given to mice with DOTAP:cholesterol liposome adjuvant intranasally, followed by determination of Ig and IgA class antibody levels in the sera and vaginal washes.

RESULTS

The CD52 core peptide elicited IgA class as well as Ig antibodies both in the sera and vaginal secretions after intranasal immunization. An additional nasal inoculation after decrease of the antibody titer raised the antibody level to its highest level during the experiment.

CONCLUSIONS

These results indicate that the CMIS could induce Ig and IgA class antibodies reactive to CD52 core peptide in the female genital tract. Intranasal immunization of a sperm-specific antigen would be a promising regimen for a safe and easy contraceptive vaccine.

Prion protein is secreted in soluble forms in the epididymal fluid and proteolytically processed and transported in seminal plasma

The presence of prion protein in sperm and fluids collected from different parts of the ram genital tract was investigated by immunoblotting with monoclonal antibodies. A slightly immunoreactive 25- to 30-kDa protein was recognized on Western blots of testicular and epididymal sperm extracts. Immunoreactivity increased on ejaculated sperm extracts and 2 other bands at 35 and 43 kDa also reacted. Seminal plasma showed several immunoreactive bands, the main bands being detected at 43 and 35 kDa, whereas less reactive bands were observed at 30, 25, 20, and <14 kDa. All these bands strongly decreased in the seminal plasma after vasectomy, indicating a testicular or an epididymal origin. Testicular fluid showed almost no reactivity, whereas caudal epididymal fluid contained the 2 strong immunoreactive bands at 43 and 35 kDa and in some cases a faint 30-kDa band. The 43-kDa band was also found in the fluid from the proximal caput, whereas the 35-kDa band appeared in the distal caput. Immunoprecipitation of (35)S-labeled proteins secreted in the epididymal fluid indicated that the 43-kDa form was synthesized in caput and caudal regions and the 35-kDa form in the distal caput to the distal corpus. Treatment of caudal fluid and seminal plasma by N-glycosidase resulted in the formation of 3 bands: 1 highly reactive at about 25 kDa, a second less reactive at about 28 kDa, and a third at approximately 20 kDa. The pattern of prion protein distribution in epididymal fluids was found to be similar in scrapie-infected rams to that of healthy rams. Cauda epididymal fluid and seminal plasma from infected animals could not be treated directly with proteinase K, because of the presence of protease inhibitors. However, the prion protein immunoprecipitated from these fluids was completely cleaved by proteinase K, whereas in the same conditions this from an infected sheep brain gave the usual resistant band pattern.

Carbohydrate-based interactions of oviductal sperm reservoir formation-studies in the pig

Competitive inhibition of sperm to explants of the oviductal epithelium was used to study the complementary receptor system that may be involved in the establishment of the oviductal sperm reservoir in the pig. Sperm binding to the oviductal explants is expressed as Binding Index (BI = sperm cells/0.01 mm(2)). From a set of glycoproteins with known oligosaccharide structures, only asialofetuin and ovalbumin showed inhibitory activity, indicating that ovalbumin may block high affinity binding sites (IC(50) congruent with 1.3 microM) and asialofetuin low affinity sites (IC(50) congruent with 18 microM) of the complementary receptor systems, whereas fetuin carrying terminal sialic acid has no effect. Ovalbumin glycopeptides were isolated by Con A affinity chromatography and reverse-phase HPLC following tryptic digestion. Glycopeptides and enzymatically released glycans were analyzed by MS, and were shown to represent preferentially the two high mannose type glycans (Man)(5)(GlcNAc)(2) and (Man)(6)(GlcNAc)(2), and as a minor component the hybrid type glycan (Hex)(4)(GlcNAc)(5). Glycopeptides (84% inhibition) and glycans (81% inhibition) significantly reduced sperm-oviduct binding at a concentration of 3 microM, whereas the deglycosylated peptides showed no inhibitory activity. Mannopentaose (IC(50) congruent with 0.8 microM) representing the oligomannose residue of the high mannose glycans of ovalbumin was as effective as ovalbumin. These data indicate that the carbohydrate-based mechanisms underlying the formation of the oviductal sperm reservoir in the pig is the result of the concerted action of at least the high-affinity binding sites for oligomannose or nonreducing terminal mannose residues and low-affinity binding of galactose.

Function of the mammalian oviductal sperm reservoir

Sperm are stored in the isthmic region of the oviduct under conditions that maintain sperm viability and suppress motility. This region is also the site in which essential steps of the capacitation process are coordinated with the appearance of the ovulated egg. The influx of Ca(2+) and phosphorylation of sperm proteins are features of the ongoing capacitation process. Using a cell-culture system of oviductal epithelial cells, it was found that sperm bound to the epithelial cells showed a reduced Ca(2+) uptake and almost no tyrosine phosphorylation as shown by indirect immunofluorescence. Furthermore, sperm viability, measured as membrane integrity with propidium iodide, is significantly prolonged as compared to sperm in suspension. The formation of the sperm reservoir appears to be mediated by carbohydrate-protein interaction. In the pig, it has been found that mannosyl-oligosaccharides exposed by the epithelial cells are high-affinity ligands for sperm-associated lectins. Ovalbumin and mannopentaose are effective inhibitors of sperm binding to explants of oviductal epithelium. Spermadhesins, a new class of animal lectins and the major secretory products of the porcine seminal vesicle, associate with the sperm surface at ejaculation and are candidate molecules for the receptors of the epithelial carbohydrates.

Molecular basis of human sperm-zona pellucida interaction

The recognition of carbohydrate sequences by complimentary receptors has been shown to be a critical factor in gamete interaction in many different animal species. We have proposed the hypothesis that, in the human, sperm binding to the zona pellucida requires a 'selectin-like' interaction. We have used the hemizona assay (a unique internally controlled bioassay that evaluates tight binding of human sperm to the homologous zona pellucida) and advanced methods of carbohydrate analysis to test this hypothesis. We provide compelling evidence that demonstrates that oligosaccharide recognition is also required for specific, tight human gamete binding. Hapten inhibition tests, zona pellucida lectin-binding studies and removal/modification of functional carbohydrates by chemical and enzymatic methods provide evidence for the involvement of defined carbohydrate moieties in initial binding. Our studies suggest the existence of distinct zona-binding proteins on human sperm that can bind to selectin ligands. Additionally, results suggest a possible convergence in the types of carbohydrate sequences recognized during initial human gamete binding and immune/inflammatory cell interactions. Full characterization of the glycoconjugates that manifest selectin-ligand activity on the human zona pellucida will allow for a better understanding of human gamete interaction in physiological and pathological situations.