Distinct Escherichia coli transcriptional profiles in the guts of recurrent UTI sufferers revealed by pan-genome hybrid selection

Low-abundance members of microbial communities are difficult to study in their native habitat. This includes Escherichia coli, a minor, but common inhabitant of the gastrointestinal tract and opportunistic pathogen, including of the urinary tract, where it causes most infections. While our understanding of the interactions between uropathogenic Escherichia coli (UPEC) and the bladder is increasing, comparatively little is known about UPEC in its pre-infection reservoir, partly due to its low abundance there (<1% relative abundance). In order to specifically and sensitively explore the genomes and transcriptomes of diverse E. coli from gastrointestinal communities, we developed E. coli PanSelect, a set of probes designed to enrich E. coli's broad pangenome. First we demonstrated the ability of PanSelect to enrich diverse strains in an unbiased way using a mock community of known composition. Then we enriched E. coli DNA and RNA from human stool microbiomes by 158 and 30-fold, respectively. We also used E. coli PanSelect to explore the gene content and transcriptome of E. coli within the gut microbiomes of women with history of recurrent urinary tract infection (rUTI), finding differential regulation of pathways that suggests that the rUTI gut environment promotes respiratory vs fermentative metabolism. E. coli PanSelect technology holds promise for investigations of native in vivo biology of diverse E. coli in the gut and other environments, where it is a minor component of the microbial community, using unbiased, culture-free shotgun sequencing. This method could also be generally applied to other highly diverse, low abundance bacteria.

Gut microbiome perturbation, antibiotic resistance, and Escherichia coli strain dynamics associated with international travel: a metagenomic analysis

BACKGROUND

Culture-based studies have shown that acquisition of extended-spectrum β-lactamase-producing Enterobacterales is common during international travel; however, little is known about the role of the gut microbiome before and during travel, nor about acquisition of other antimicrobial-resistant organisms. We aimed to identify (1) whether the gut microbiome provided colonisation resistance against antimicrobial-resistant organism acquisition, (2) the effect of travel and travel behaviours on the gut microbiome, and (3) the scale and global heterogeneity of antimicrobial-resistant organism acquisition.

METHODS

In this metagenomic analysis, participants were recruited at three US travel clinics (Boston, MA; New York, NY; and Salt Lake City, UT) before international travel. Participants had to travel internationally between Dec 8, 2017, and April 30, 2019, and have DNA extractions for stool samples both before and after travel for inclusion. Participants were excluded if they had at least one low coverage sample (<1 million read pairs). Stool samples were collected at home before and after travel, sent to a clinical microbiology laboratory to be screened for three target antimicrobial-resistant organisms (extended-spectrum β-lactamase-producing Enterobacterales, carbapenem-resistant Enterobacterales, and mcr-mediated colistin-resistant Enterobacterales), and underwent DNA extraction and shotgun metagenomic sequencing. We profiled metagenomes for taxonomic composition, antibiotic-resistant gene content, and characterised the Escherichia coli population at the strain level. We analysed pre-travel samples to identify the gut microbiome risk factors associated with acquisition of the three targeted antimicrobial resistant organisms. Pre-travel and post-travel samples were compared to identify microbiome and resistome perturbation and E coli strain acquisition associated with travel.

FINDINGS

A total of 368 individuals travelled between the required dates, and 296 had DNA extractions available for both before and after travel. 29 travellers were excluded as they had at least one low coverage sample, leaving a final group of 267 participants. We observed a perturbation of the gut microbiota, characterised by a significant depletion of microbial diversity and enrichment of the Enterobacteriaceae family. Metagenomic strain tracking confirmed that 67% of travellers acquired new strains of E coli during travel that were phylogenetically distinct from their pre-travel strains. We observed widespread enrichment of antibiotic-resistant genes in the gut, with a median 15% (95% CI 10-20, p<1 × 10-10) increase in burden (reads per kilobase per million reads). This increase included antibiotic-resistant genes previously classified as threats to public health, which were 56% (95% CI 36-91, p=2 × 10-11) higher in abundance after travel than before. Fluoroquinolone antibiotic-resistant genes were aquired by 97 (54%) of 181 travellers with no detected pre-travel carriage. Although we found that visiting friends or relatives, travel to south Asia, and eating uncooked vegetables were risk factors for acquisition of the three targeted antimicrobial resistant organisms, we did not observe an association between the pre-travel microbiome structure and travel-related antimicrobial-resistant organism acquisition.

INTERPRETATION

This work highlights a scale of E coli and antimicrobial-resistant organism acquisition by US travellers not apparent from previous culture-based studies, and suggests that strategies to control antimicrobial-resistant organisms addressing international traveller behaviour, rather than modulating the gut microbiome, could be worthwhile.

FUNDING

US Centers for Disease Control and Prevention and National Institute of Allergy and Infectious Diseases.

Intrinsic Resistance to Colistin in the Genus Hafnia

A bacterial species is considered to be intrinsically resistant to an antimicrobial when nearly all of the wild-type isolates (i.e., those without acquired resistance) exhibit minimum inhibitory concentration (MIC) values that are sufficiently high such that susceptibility testing is unnecessary, and that the antimicrobial should not be considered for therapy. Accordingly, knowledge of intrinsic resistance influences both the selection of treatment regimens and the approach to susceptibility testing in the clinical laboratory, where unexpected results also facilitate the recognition of microbial identification or susceptibility testing errors. Previously, limited data have suggested that Hafnia spp. may be intrinsically resistant to colistin. We evaluated the in vitro activity of colistin against 119 Hafniaceae that were isolated from human samples: 75 (63%) from routine clinical cultures and 44 (37%) from stool samples of travelers undergoing screening for antimicrobial resistant organisms. Broth microdilution colistin MICs were ≥4 μg/mL for 117 of 119 (98%) isolates. Whole-genome sequencing of 96 of the isolates demonstrated that the colistin-resistant phenotype was not lineage-specific. 2 of the 96 (2%) isolates harbored mobile colistin resistance genes. Compared to whole-genome sequencing, VITEK MS matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and VITEK 2 GN ID failed to consistently distinguish between Hafnia alvei, Hafnia paralvei, and Obesumbacterium proteus. In conclusion, using a reference antimicrobial susceptibility testing method and a genetically diverse collection of isolates, we found Hafnia spp. to be intrinsically resistant to colistin. The recognition of this phenotype will help inform rational approaches by which to perform antimicrobial susceptibility testing and therapy for patients with infections that are caused by Hafnia spp.

Global phylogenomic analyses of Mycobacterium abscessus provide context for non cystic fibrosis infections and the evolution of antibiotic resistance

Mycobacterium abscessus (MAB) is an emerging pathogen that leads to chronic lung infections. To date, the global population structure of non-cystic fibrosis (CF) MAB and evolutionary patterns of drug resistance emergence have not been investigated. Here we construct a global dataset of 1,279 MAB whole genomes from CF or non-CF patients. We utilize whole genome analysis to assess relatedness, phylogeography, and drug resistance evolution. MAB isolates from CF and non-CF hosts are interspersed throughout the phylogeny, such that the majority of dominant circulating clones include isolates from both populations, indicating that global spread of MAB clones is not sequestered to CF contexts. We identify a large clade of M. abscessus harboring the erm(41) T28C mutation, predicted to confer macrolide susceptibility in this otherwise macrolide-resistant species. Identification of multiple evolutionary events within this clade, consistent with regain of wild type, intrinsic macrolide resistance, underscores the critical importance of macrolides in MAB.

Mycobacterium abscessus is an emerging infection that usually affects patients with structural lung diseases such as cystic fibrosis (CF). Here, the authors use phylogenetic analyses to demonstrate close relationships between isolates from CF and non-CF patients and identify antibiotic resistance markers.

Progesterone promotes the acrosome reaction in capacitated human spermatozoa as judged by flow cytometry and CD46 staining

The acrosome reaction is a necessary prerequisite for spermatozoa to acquire fertilizing ability. Several different moieties appear to promote the acrosome reaction through different pathways, including solubilized zona pellucidae, recombinant zona protein ZP3, follicular fluid, calcium ionophores, and mannosylated bovine serum albumin (BSA). Although many investigators have presented evidence that progesterone also promotes the acrosome reaction through the mediation of a non-genomic cell membrane receptor, this concept has been challenged. Other workers have suggested that progesterone does not promote an acrosome reaction in human spermatozoa, as judged by the detection of CD46, a complement regulatory protein present on the inner acrosome membrane, through flow cytometric analysis of large numbers of spermatozoa. Prior investigations were criticized by the limited numbers of spermatozoa enumerated visually, the use of non-specific staining techniques, and the failure to eliminate dead spermatozoa during the scoring of the acrosome reaction. We have repeated these experiments, using both a supravital dye to eliminate dead spermatozoa from flow cytometric analysis, and anti-CD46 monoclonal antibody to score acrosome-reacted spermatozoa. Care was taken to validate the adequacy of capacitation conditions, which were proven by the ability of spermatozoa to acrosome react in response to mannosylated BSA and to penetrate zona-free hamster eggs. Confocal microscopy was used to confirm that CD46 immunostaining was limited to the acrosomal region of the spermatozoon head. Our results indicate that progesterone does promote an acrosome reaction within capacitated spermatozoa.

Evidence that a functional fertilin-like ADAM plays a role in human sperm-oolemmal interactions

Fertilin is a protein initially identified in guinea pig spermatozoa; it is the prototype of a larger family of conserved, proteins designated as a disintegrin and a metalloproteinase (ADAM). These heterodimers which consist of alpha and beta subunits, containing metalloproteinase-like and disintegrin-like domains, appear to play a role in mammalian fertilization. Peptides derived from the disintegrin domains of two ADAMs, fertilin and cyritestin, interfere with gamete adhesion and sperm-egg membrane fusion in non-human species. It has been suggested that fertilin-beta binds to an oolemmal integrin, and it is proposed that the tripeptide FEE (Phe-Glu-Glu) is the integrin recognition sequence in human fertilin-beta. We evaluated whether fertilin beta plays a role in human fertilization by studying the effects of a linear octapeptide containing the FEE sequence, SFEECDLP, and a scrambled octapeptide with the same amino acids, SFPCEDEL, on the incorporation of human spermatozoa by human zona-free eggs. The effects of G4120, a potent RGD-containing (Arg-Gly-Asp) thioether-bridged cyclic peptide which blocks both fibronectin and vitronectin receptors, and the relationship between FEE- and RGD-receptor interactions on sperm-egg interactions were also studied. The FEE-containing peptide, but not the scrampled peptide, inhibited sperm adhesion to oocytes and their penetration, over the range 1-5 microM. The inhibition induced by SFEECDLP was reversible and occurred only in the presence of peptide itself. The G4120 peptide exhibited 10-fold less inhibitory effects on sperm adhesion and penetration than did SFEECDLP. When combined, SFEECDLP and G4120 exhibited strong inhibition of both adhesion and penetration at concentrations that individually had been ineffective, suggesting co-operation between the two receptor-ligand interactions during fertilization. We propose that a fertilin-like molecule is functionally active on human spermatozoa and that its interaction with an oolemmal integrin receptor plays a role in fertilization in humans.

Evidence that a functional fertilin-like ADAM plays a role in human sperm-oolemmal interactions

Fertilin is a protein initially identified in guinea pig spermatozoa; it is the prototype of a larger family of conserved, proteins designated as a disintegrin and a metalloproteinase (ADAM). These heterodimers which consist of alpha and beta subunits, containing metalloproteinase-like and disintegrin-like domains, appear to play a role in mammalian fertilization. Peptides derived from the disintegrin domains of two ADAMs, fertilin and cyritestin, interfere with gamete adhesion and sperm-egg membrane fusion in non-human species. It has been suggested that fertilin-beta binds to an oolemmal integrin, and it is proposed that the tripeptide FEE (Phe-Glu-Glu) is the integrin recognition sequence in human fertilin-beta. We evaluated whether fertilin beta plays a role in human fertilization by studying the effects of a linear octapeptide containing the FEE sequence, SFEECDLP, and a scrambled octapeptide with the same amino acids, SFPCEDEL, on the incorporation of human spermatozoa by human zona-free eggs. The effects of G4120, a potent RGD-containing (Arg-Gly-Asp) thioether-bridged cyclic peptide which blocks both fibronectin and vitronectin receptors, and the relationship between FEE- and RGD-receptor interactions on sperm-egg interactions were also studied. The FEE-containing peptide, but not the scrampled peptide, inhibited sperm adhesion to oocytes and their penetration, over the range 1-5 microM. The inhibition induced by SFEECDLP was reversible and occurred only in the presence of peptide itself. The G4120 peptide exhibited 10-fold less inhibitory effects on sperm adhesion and penetration than did SFEECDLP. When combined, SFEECDLP and G4120 exhibited strong inhibition of both adhesion and penetration at concentrations that individually had been ineffective, suggesting co-operation between the two receptor-ligand interactions during fertilization. We propose that a fertilin-like molecule is functionally active on human spermatozoa and that its interaction with an oolemmal integrin receptor plays a role in fertilization in humans.

An investigation of the latency period between sperm oolemmal adhesion and oocyte penetration

In clinical studies of the ability of capacitated human sperm to penetrate zona-free hamster eggs, we have previously observed that the ratio of oolemmal adherent to penetrating sperm varied between men. Sperm incorporation did not occur immediately following gamete adhesion and not all adherent sperm penetrated the egg. To further investigate this phenomenon, comparisons were made of the kinetics of gamete adhesion, membrane fusion, and sperm incorporation of capacitated mouse and human spermatozoa by zona-free hamster eggs and of mouse sperm by zona-free mouse and hamster eggs. Eggs were inseminated with either capacitated human or mouse sperm or combinations of both, washed out of sperm suspension after initial gamete adherence, and further incubated in sperm-free medium. Gamete membrane fusion was judged by dye transfer of Hoechst 33342 and sperm entry of the cortical ooplasm by observation of expanded sperm heads within acridine orange stained eggs. Oolemmal adherent mouse and human sperm fused with and penetrated zona-free hamster eggs at different times whether eggs were inseminated in parallel or with combinations of sperm of both species. Oolemmal adherent mouse sperm penetrated zona-free hamster eggs prior to their penetration of zona-free mouse eggs. Ultrastructural studies of zona-free human eggs inseminated with human sperm confirmed prior observations with hamster eggs that only acrosome-reacted human sperm adhere to the oolemma. These results have lead us to postulate that sperm entry into the egg may occur through a "zipper" mechanism involving the ligation of local gamete receptors similar to the incorporation of target particles by phagocytes and suggest that not all oolemmal adherent human sperm are capable of being incorporated although they have undergone an acrosome reaction.

Gonadotropins do not induce antiphospholipid antibodies

PROBLEM

To determine whether the increased incidence of antiphospholipid antibodies (APAs) in women undergoing assisted reproduction might be secondary to superovulation with gonadotropins, predisposing women to an abnormal immune response and thus inducing APAs.

METHOD OF STUDY

Women undergoing assisted reproduction with gonadotropins for the first time were selected and tested before the initiation of the stimulation cycle, during the cycle, and at the end of the cycle (group 1). Women who had undergone gonadotropin stimulation at least 60 days earlier (group 2) and normal, nonpregnant, fertile women (group 3) also were evaluated. Serum samples were assayed by the enzyme-linked immunosorbent assay method.

RESULTS

Ten (20%) of 50 women in group 1 were positive for APAs. The 10 women who were positive for APAs remained positive throughout the treatment cycle. Positive antibodies were identified in 12 (24%) of 50 women in group 2, not significantly different from group 1 (P = 0.81). Antibodies were present in 2 of 50 normal fertile control subjects, significantly less frequently than in group 1 (P < 0.03) and in group 2 (P < 0.01).

CONCLUSIONS

These data suggest that gonadotropin administration and/or the ovarian response to stimulation does not predispose women to the induction of APAs. Moreover, the incidence of APAs in this population, which is higher than that found in normal fertile women, cannot be explained by cycle-induced events.

Prostaglandins induce calcium influx in human spermatozoa

Progesterone, prostaglandin and follicular fluid are reported to enhance the acrosome reaction through the influx of extracellular calcium into the cytoplasm of human spermatozoa. Prostaglandins are present within the male reproductive tract, and high concentrations of prostaglandins exist in seminal fluid. In order to investigate the mechanisms by which prostaglandins enhance the acrosome reaction through calcium influx, the intracellular calcium response induced by progesterone, prostaglandin E1 (PGE1), prostaglandin E2 (PGE2) and follicular fluid was measured using fura-2. PGE1 and PGE2 promoted calcium influx dose dependently through dihydropyridine insensitive calcium channels. Refractoriness of the elevation of intracellular Ca2+ concentration ([Ca2+]i) to a second stimulus occurred when 60 microg/ml PGE1 was administered 100 s after the prior administration of 60 microg/ml of PGE1, and similarly when 1 microg/ml of progesterone was administered 100 s after the prior administration of 1 microg/ml of progesterone. Refractoriness also occurred when 60 microg/ml PGE1 was administered after the prior addition of 60 microg/ml PGE2, but did not occur between PGE1 and progesterone. Pertussis toxin (PTX) did not modify the changes in [Ca2+]i after the addition of PGE1 or PGE2. In conclusion, PGE1 and PGE2 promoted calcium influx through PTX-insensitive calcium channels which appeared to be recognized by a common receptor different from that of progesterone.

Measurement of vitronectin content of human spermatozoa and vitronectin concentration within seminal fluid

OBJECTIVE

Vitronectin previously has been extracted from human spermatozoa and messenger RNA (mRNA) encoding vitronectin localized by reverse transcriptase in situ polymerase chain reaction (PCR) to spermatocytes of human testis. In the present experiments, we have established ranges for the content of vitronectin in living human spermatozoa and vitronectin concentration within seminal fluid of human ejaculates.

DESIGN

Seminal fluid was obtained by centrifugation and motile sperm selected by swim-up from men with normal and abnormal ejaculates, according to World Health Organization criteria, for vitronectin determinations.

SETTING

Academic research environment.

MAIN OUTCOME MEASURE(S)

Seminal fluid vitronectin concentrations were measured by ELISA and sperm vitronectin content by polyacrylamide gel electrophoresis and semiquantitative Western blots.

RESULT(S)

Vitronectin seminal fluid concentration was 1.35 +/- 1.0 mg/mL (mean +/- SD) for normospermic samples (n = 26) and 0.78 +/- 0.4 mg/mL for azoospermic specimens (n = 6). Vitronectin sperm content ranged from 1 to 15 ng/10(6) motile cells (n = 20). Both high- and low-molecular-weight material was observed. Sperm content of vitronectin did not vary with sperm morphology.

CONCLUSION(S)

These results suggest that spermatozoa represent a major source of seminal fluid vitronectin, but that a secondary source exists, perhaps through transudation from serum.

Detection using antisperm monoclonal antibodies of shared epitopes expressed by human spermatozoa and oocytes

OBJECTIVE

To determine whether human spermatozoa and oocytes share common antigenic epitopes, supporting the hypothesis that their cross-linking by antisperm antibodies present in the clinical sera of infertile couples could promote sperm adhesion to the oolemma.

DESIGN

Human and hamster eggs were studied for the presence of antigens recognized by a panel of World Health Organization Task Force monoclonal antibodies (mAbs) originally raised against human spermatozoa. A new technique was devised, using frozen sections of paraformaldehyde-fixed individual human and hamster eggs, to screen rapidly antisperm mAbs for egg reactivity. Living zona-free human and hamster eggs then were exposed to Covaspheres (Duke Scientific, Palo Alto, CA) coupled with these mAbs to document the presence of reactive epitopes on the oolemma.

SETTING

Academic research environment.

MAIN OUTCOME MEASURE(S)

Indirect immunofluorescence and Covasphere rosetting.

RESULT(S)

Eleven of 37 antisperm mAbs tested reacted with fixed hamster eggs and 10 reacted with human eggs. Five of 6 mAbs reactive with both fixed eggs also reacted with the oolemma of living, zona-free eggs.

CONCLUSION(S)

Common antigenic epitopes, some of which are shared with somatic tissues, exist on the oolemma of human eggs and on the plasma membrane of human spermatozoa.

Is vitronectin the velcro that binds the gametes together?

Evidence has been presented that the adhesion of human spermatozoa to the oolemma is mediated by integrins recognizing the Arg-Gly-Asp sequence (RGD). Fibronectin and vitronectin, glycoproteins that contain functional RGD sequences, are both present on human spermatozoa, and integrins that recognize these ligands have been detected on spermatozoa and eggs. In this work, we studied the effects of oligopeptides specifically designed to block fibronectin or vitronectin receptors on the interaction of human spermatozoa with zona-free hamster oocytes. GRGDdSP, a peptide blocking cell attachment to fibronectin, was without effect, while GdRGDSP, which blocks both fibronectin and vitronectin receptors, significantly inhibited the binding of human spermatozoa to the oolemma of zona-free hamster eggs, in a concentration-dependent manner, over a range 1-100 microM. As these experiments suggested that a vitronectin receptor plays a role in sperm-oolemmal adhesion, we performed a series of experiments studying the effects of exogenous vitronectin, when added to spermatozoa and oocytes, on gamete interactions. Sperm-oolemmal adherence, as well as sperm aggregation, was promoted by vitronectin, over range of 2.2 nM to 1 microM, but only in the presence of calcium ions. We propose that vitronectin released during the sperm acrosome reaction is recognized by both gametes and plays a role in their adhesion.

P-selectin is expressed on the oolemma of human and hamster oocytes following sperm adhesion and is also detected on the equatorial region of acrosome-reacted human spermatozoa

Selectins are a family of adhesive molecules, involved in the interactions between leukocytes and endothelium and in platelet adhesion. P-selectin, one of the members of this family, is stored in alpha-granules and dense granules of platelets as well as in Weibel-Palade bodies of endothelial cells, and it is rapidly redistributed to the cell surface after activation. It recognizes carbohydrate structures as ligands, in particular sialyl-Lewis(x), which is part of the CD15 antigen. In this work we studied P-selectin expression on gametes. While zona-free human and hamster oocytes did not react with a monoclonal antibody directed against P-selectin, oocytes from both species displayed a reactivity with this antibody following their contact with human spermatozoa, as demonstrated both by covasphere binding and indirect immunofluorescence. Artificial activation of zona-intact human oocytes by means of the calcium lonophore A23187 induced the expression on the oolemma of a moiety reacting with anti-P-selectin antibody as well. P-selectin also appeared to be expressed on the sperm surface following the acrosome reaction, as demonstrated by a flow cytometric study of reactivity of spermatozoa with the anti-P-selectin antibody, using the expression of CD46 as a marker of the acrosome reaction. The localization of the P-selectin moiety on the equatorial region of the plasma membrane of acrosome reacted spermatozoa was confirmed by transmission electron microscopy using immunogold labelling. We suggest that P-selectin might be involved in gamete interactions.

The expression of alpha v, alpha 5, beta 1, and beta 3 integrin chains on ejaculated human spermatozoa varies with their functional state

Evidence has been presented suggesting the involvement of integrins and their ligands in mammalian fertilization. In this study we asked whether the alpha 5, alpha v, beta 1 and beta 3 integrin chains, which form receptors for fibronectin and vitronectin, are present on human spermatozoa. Fresh ejaculate spermatozoa and capacitated spermatozoa, before and after a calcium ionophore (A23187)-induced acrosome reaction, were either fixed and their reaction with anti-integrin monoclonal antibodies detected by immunoperoxidase staining or studied without fixation, using cytofluorimetric scanning. Expression of specific integrin chains varied with the functional state of spermatozoa. The alpha 5 chain was not detected on fresh living spermatozoa, but was present on capacitated spermatozoa, whether fixed or living. The pattern of beta 1 expression on living spermatozoa paralleled that of alpha 5. No further increase in the expression of either alpha 5 or beta 1 was observed following an ionophore-promoted acrosome reaction. In contrast, alpha v was detected on neither fresh, living ejaculate spermatozoa, nor following capacitation (< 10% reactive). The percentage of alpha v positive cells increased substantially following ionophore exposure. Expression of beta 3 was similar to alpha v, and the percentage of cells displaying beta 3 correlated with the proportion of spermatozoa that had undergone an acrosome reaction, following ionophore exposure. These results indicate that the expression of integrins on spermatozoa is dynamic, varying with their functional state and that integrin receptors for fibronectin (alpha 5 beta 1) become apparent on the spermatozoan surface during capacitation and vitronectin (alpha v beta 3) following the acrosome reaction.

Echistatin, a disintegrin, inhibits sperm-oolemmal adhesion but not oocyte penetration

OBJECTIVE

To study the effects of echistatin, a disintegrin known to block the binding of fibronectin (FN) and vitronectin to their respective integrin receptors, alpha 5 beta 1 and alpha v beta 3, on the adhesion of human spermatozoa to the oolemma of zona-free hamster eggs and their subsequent penetration.

DESIGN

Motile capacitated human spermatozoa and zona-free hamster eggs were coincubated in the presence of echistatin or in its absence and observed at short serial intervals. Whole mounts of these eggs, washed out of sperm suspension and stained with acridine orange, were scored for numbers of oolemmal adherent and penetrating sperm.

SETTING

University Hospital laboratories.

PATIENTS

Known fertile semen donors.

MAIN OUTCOME MEASURES

Numbers of spermatozoa adherent to the oolemma and those penetrating the oocyte.

RESULTS

Sperm adherence to the oolemma was reduced significantly at micromolar concentrations of echistatin, in a concentration-dependent manner. In contrast, echistatin did not inhibit the penetration of oocytes by sperm that had become adherent to the oolemma despite the presence of echistatin.

CONCLUSION

We propose that two processes occur in the binding of sperm to the oolemma, one that is echistatin sensitive and possibly involving the integrin receptors that recognize FN and vitronectin, and a second process, resistant to echistatin, that leads to gamete membrane fusion.

PCR-amplified vitronectin mRNA localizes in situ to spermatocytes and round spermatids in the human testis

Vitronectin is an adhesion protein present within the acrosomal cap region of human spermatozoa and is liberated during the acrosome reaction. The purpose of this study was to determine if vitronectin mRNA was synthesized in the male genital tract using the reverse transcriptase in-situ polymerase chain reaction (PCR) technique. Twelve genital tract tissues, which included six testes, one showing Sertoli cells only and one from a 3 year old boy, as well as sections from the prostate, seminal vesicles, and epididymis, were analysed for vitronectin transcripts. PCR-amplified vitronectin cDNA was detected in the seminiferous tubules of the four adult testes that showed normal spermatogenesis and localized to the spermatocytes and round spermatids. PCR-amplified vitronectin cDNA was not detected in the tissues of the prostate, epididymis, and seminal vesicles from the men whose testes did contain the message, nor in the testes with Sertoli cells only or that of the prepubertal boy. It is concluded that, in the male genital tract, vitronectin is transcribed exclusively in the germ cells at the spermatocyte and round spermatid stages. This demonstrates that the translated protein present in the spermatozoon is being produced in situ. Further study is needed to determine the role of this protein in the dynamics of sperm-oocyte interaction.

Vitronectin is an intrinsic protein of human spermatozoa released during the acrosome reaction

Evidence has been presented that oolemmal integrins and their ligands on spermatozoa may play a role in gamete interactions leading to fertilization. We previously demonstrated that vitronectin (Vn) could be extracted from fresh human spermatozoa and detected in Western blots, and Vn was observed on the surface of living, capacitated sperm by indirect immunofluorescence. In the present experiments, messenger RNA encoding Vn was detected in human testis poly (A+) RNA using Northern analysis, and Vn was localized within the acrosomal region of ejaculated sperm by immunoperoxidase and immunofluorescence staining. During the acrosome reaction, induced in capacitated spermatozoa by lonomycin, Vn was released into the medium in a calcium-dependent manner. Vn appears to be a specific product of intratesticular spermatozoa that is secreted during the acrosome reaction. These findings suggest that Vn is positioned to play a strategic role in gamete interactions leading to fertilization.

Mammalian oocytes exhibit specific recognition of the RGD (Arg-Gly-Asp) tripeptide and express oolemmal integrins

Integrins are a family of cell adhesion receptors involved in many cell-cell and cell-matrix interactions. Some of these heterodimeric receptors, such as alpha 5 beta 1 and alpha v beta 1, specifically recognize the amino acid sequence Arg-Gly-Asp (RGD) within their ligands. The RGD sequence is found in fibronectin, vitronectin, and other extracellular matrix proteins. Our results demonstrate that the oolemmas of eggs from human and several other mammalian species contain receptors capable of binding to RGD ligands, and that integrin subunits are expressed by oocytes. Four distinct techniques were utilized to identify the presence of functional integrins on mammalian eggs. RGD-binding receptors were detected on the surfaces of zona-free eggs from all species tested. Covaspheres coated with PepTite-2000, which contains RGD, bound to the eggs and formed rosettes. Rosetting was competitively inhibited by PepTite-2000 and by GRGDTP, a soluble RGD peptide, but not by RGES. An ELISA using polyclonal antibodies directed against the cytoplasmic tails of the integrin subunits identified the integrin subunits alpha 5, beta 1, and alpha v, but not beta 3, in detergent extracts of Syrian hamster eggs. A dot blot confirmed the presence of alpha v in hamster egg lysates. Finally, the integrin subunits alpha 2, alpha 5, alpha 6, but not alpha 4, were detected on the surfaces of zona-free eggs from human and Syrian hamster. Immunobeads coated with monoclonal antibodies specific for alpha 2, alpha 5, and alpha 6 bound to the eggs and formed rosettes.(ABSTRACT TRUNCATED AT 250 WORDS)

Progesterone-evoked increases in sperm [Ca2+]i correlate with the egg penetrating ability of sperm from fertile but not infertile men

OBJECTIVES

To investigate the relationship between sperm capacitation and intracellular calcium ([Ca2+]i) and to correlate these findings with routine semen parameters and sperm fertilizing ability.

DESIGN

Baseline and P-evoked increases in [Ca2+]i of fresh versus capacitated human sperm were measured for known fertile donors and infertile men and compared with the results of semen analysis and in vitro penetration of zona-free hamster eggs.

SETTING

Andrology laboratory in a university hospital.

PATIENTS

Infertile men undergoing semen analysis.

INTERVENTIONS

Capacitation of spermatozoa and exposure of sperm to P (1 microgram/mL).

MAIN OUTCOME MEASURES

[Ca2+]i as measured using fura-2, percent zone-free hamster eggs penetrated, and number of penetrating sperm per egg.

RESULTS

Steady state [Ca2+]i increased from 74 +/- 32 nM to 166 +/- 97 nM after capacitation, as did P-evoked peak and plateau [Ca2+]i. Deletion of calcium from the assay buffer with ethylene-bis (oxy-ethylenenitriolo) tetraacetic acid abrogated the P-evoked increments. RU486, a P receptor antagonist; reduced the P-evoked response in a dose-dependent manner. Progesterone-evoked calcium responses of sperm varied between different ejaculates of the same fertile donor and correlated with their egg penetrating ability. Sperm from infertile men with abnormal morphology exhibited lower egg penetrating ability and lower mean peak P-evoked [Ca2+]i than morphologically normal sperm. However, free intracellular calcium parameters correlated only weakly with penetrating ability for individual infertile men.

CONCLUSION

Progesterone-evoked increases in [Ca2+]i in motile capacitated spermatozoa cannot be used to discriminate between dysfunctional spermatozoa and those capable of penetrating eggs.

Correlation between puberty and the development of autoimmunity to spermatozoa in men with cystic fibrosis

OBJECTIVE

To test the hypothesis that puberty is a necessary factor in the pathogenesis of autoimmunity to sperm in men with cystic fibrosis (CF), we studied prepubertal and postpubertal males with CF versus an age-matched group of males with type 1 diabetes as controls.

DESIGN

Sera from CF and diabetic males treated at University Hospital, State University of New York, Stony Brook, were tested by indirect immunobead binding for antisperm antibodies and by radioimmunoassay for testosterone (T), luteinizing hormone, and follicle-stimulating hormone. The finding of autoantibodies to spermatozoa was correlated with chronological age, as well as with clinical and hormonal pubertal status.

RESULTS

Autoimmunity to sperm, as detected by humoral antisperm antibodies, was documented solely in postpubertal males, as judged by hormonal and clinical criteria. Eighty-three percent of sexually mature CF males and 6.3% (1 of 16) diabetic males exhibited autoantibodies to sperm. These antibodies were only detected when serum T levels were > 8.7 nmol/L (250 ng/dL).

CONCLUSIONS

These results suggest that puberty, and presumably, active spermatogenesis is a requirement for the development of autoimmunity to sperm in men with CF.

Sperm surface proteins after capacitation. Expression of vitronectin on the spermatozoan head and laminin on the sperm tail

Several integrins recognize as ligands proteins containing the Arg-Gly-Asp (RGD) sequence, such as fibronectin, vitronectin, and laminin. It has been previously demonstrated that oligopeptides containing the RGD sequence competitively inhibit both the adhesion of hamster and human sperm to zona-free hamster eggs and their subsequent penetration. In addition, the appearance of fibronectin on the surface of living human spermatozoa after capacitation has been demonstrated. In this work, it is shown that spermatozoa incubated overnight under capacitating conditions, but not fresh spermatozoa, also display the RGD-containing proteins vitronectin and laminin. Whereas the expression of fibronectin does not appear to be localized to any specific region of the sperm surface, laminin is present solely on the sperm tail, and vitronectin was detected mostly as an equatorial band on the sperm head. The percent of capacitated spermatozoa within each ejaculate reacting with antivitronectin antibodies (51% to 94%) was similar to that observed with antifibronectin antibodies (72% to 100%) in a series of fertile donors, and in a series of infertile men (7% to 98% for vitronectin versus 5% to 100% for fibronectin). In contrast, the percent of spermatozoa displaying laminin was lower, ranging from 2% to 42% for fertile donors and from 5% to 34% for infertile donors, and was unrelated to the expression of fibronectin or vitronectin. The time of appearance of both fibronectin and vitronectin when spermatozoa were incubated under capacitating conditions varied for different sperm donors, suggesting a difference in the process of their expression between different men. The specificity of antivitronectin antibody binding to human spermatozoa was demonstrated by competitive inhibition with purified human vitronectin. That there was no immunologic reaction between the antivitronectin antibodies used and fibronectin was demonstrated both by the failure of free fibronectin to inhibit antivitronectin antibody binding to spermatozoa, and by Dot blot analysis. A partial cross-reaction of the polyclonal antivitronectin antibody with fibronectin was shown by Western blot analysis, but this phenomenon was not present when the monoclonal antivitronectin antibody was used. In addition, both fibronectin and vitronectin could be extracted from capacitated spermatozoa solubilized in Chaps buffer, as shown by Dot blot and Western blot analysis. These observations suggest that vitronectin and fibronectin expressed on the surface of capacitated human spermatozoa could act as a ligand for specific receptors on the egg, and play a role in sperm-oolemmal adhesion.

A microwell sperm penetration assay

Egg penetration rates in a modified SPA using microwells in tissue typing plates were comparable with those in a standard assay. This technique allows sperm penetrating ability to be determined using single zona-free hamster eggs and as few as 10,000 spermatozoa.

Monoclonal antibodies identify Fc gamma receptors on unfertilized human oocytes but not spermatozoa

Oolemmal Fc receptors have previously been shown to play a role in the promotion of adhesion by antibody labeled human spermatozoa to zona-free hamster eggs. In this work, we demonstrated the presence of Fc gamma RI, Fc gamma RII and Fc gamma RIII on the oolemma of unfertilized human oocytes by means of monoclonal antibodies directed against these receptors, detected both by immunobead rosetting and indirect immunofluorescence. These receptors were also functionally active in that they were able to bind human aggregated IgG, human IgG-Fc, mouse IgG1 and IgG2a. While the presence of oolemmal IgG-Fc receptors might play a role in reproductive failure, by their promotion of polyspermic fertilization, in cases where antisperm antibodies bound to the spermatozoan surface, their role in the normal physiology of fertilization or in other events unrelated to sperm incorporation remains to be determined. In contrast, Fc gamma receptors were not present on human spermatozoa, irrespective of their functional state (fresh ejaculated, capacitated or acrosome reacted).

Evidence for the presence of an integrin cell adhesion receptor on the oolemma of unfertilized human oocytes

The Arg-Gly-Asp peptide (RGD), contained in several extracellular matrix proteins such as fibronectin, laminin, vitronectin, and collagen, is a tripeptide that plays a role as a recognition sequence in many cell-to-cell and cell-to-matrix adhesion mechanisms, through its interaction with several receptors of the integrin family. We previously described the ability of the oolemma of hamster oocytes to bind GRGDTP coupled to the surface of activated immunobeads and demonstrated that RGD-containing oligopeptides inhibit the adhesion of human and hamster spermatozoa to zona-free hamster oocytes and their subsequent penetration. In the present experiments, we show, utilizing immunobeads coated with an RGD-containing peptide (PepTiteTM 2000), that the oolemma of unfertilized human eggs is also able to recognize this adhesion sequence. The binding of PepTiteTM 2000-coated immunobeads to the oolemma was inhibited by the oligopeptide GRGDTP as well as by fibronectin and laminin. When immunobeads were prepared with a PepTiteTM concentration of 10 micrograms/ml, GRGDTP 150 micrograms/ml, laminin 80 micrograms/ml, and fibronectin 60 micrograms/ml inhibited bead rosetting on the egg surface. These data suggest that a specific binding moiety for RGD is present on the human egg surface. The binding of fibronectin to the oolemma was also demonstrated by the rosetting of immunobeads coupled with antifibronectin antibody to human oocytes after their exposure to 1 mg/ml free fibronectin. Such binding of fibronectin to the oolemma could be inhibited by coincubation with a monoclonal antibody directed against the cell adhesion fragment of fibronectin.(ABSTRACT TRUNCATED AT 250 WORDS)

Sperm surface fibronectin. Expression following capacitation

The Arg-Gly-Asp (RGD) amino acid sequence plays a role in many cell-to-cell and cell-to-matrix adhesion systems, as a recognition sequence for cell membrane receptors termed integrins. Receptors of the VLA subfamily of integrins recognize fibronectin, laminin, and collagen. Given the authors' findings that fibronectin-derived, RDG-containing peptides competitively inhibit sperm-oolemmal adhesion and penetration in both heterologous (human-hamster) and homologous (hamster-hamster) gamete interactions, the expression of fibronectin on the surface of fresh, capacitated, and acrosome-reacted human spermatozoa was studied. The majority of fresh spermatozoa did not display fibronectin on their plasma membrane (0 to 16% positive), as demonstrated by the lack of binding of both monoclonal and polyclonal anti-fibronectin antibodies. In contrast, a significantly greater proportion of spermatozoa (varying between 18% to 100% for different donors) incubated overnight under capacitating conditions reacted with anti-fibronectin antibodies. The induction of an acrosome reaction with progesterone did not alter the proportion of sperm displaying fibronectin or its distribution on the sperm surface. A physiologic role of fibronectin in sperm-oolemmal interaction was suggested by the effects of anti-fibronectin antibodies on sperm oolemmal adhesion and penetration of hamster eggs by human spermatozoa, which were both significantly reduced (P less than 0.001).

Complement component C1q and its receptor are involved in the interaction of human sperm with zona-free hamster eggs

C1q is a component of the classical complement pathway that can react with the Fc-fragment of immunoglobulins and with other proteins, such as fibronectin, laminin, and a specific C1q receptor present on several cell types. Given its role in many adhesion systems, mainly related to phagocytosis, we tested the effects of C1q on the interaction between human spermatozoa and zona-free hamster eggs. The presence of C1q in the medium used for gamete coincubation resulted in promotion of sperm-oolemma adhesion and an inhibition of penetration. The number of adherent sperm per egg at 5 micrograms/ml concentration was 90 +/- 35 vs. 29 +/- 7 for the control (P less than 0.001). At 1 microgram/ml, the lower concentration at which C1q had an effect, the number of penetrating sperm/egg was 0.6 vs. 1.7 for the control without C1q (P less than 0.01), and the percent of penetrated eggs was 28% vs. 85%. At 50 micrograms/ml, the percent of penetrated eggs was 7%, with a penetration index of 0.07. The addition of C1q to the medium resulted in sperm agglutination, which varied between sperm donors. The presence of C1q receptors, as detected by anti-C1qR monoclonal antibodies (Mabs), was demonstrated both on zona-free hamster eggs by immunobead rosetting and on human spermatozoa by immunobead binding and indirect immunofluorescence. Mabs directed against different epitopes of C1qR had different effects on gamete interaction, with a partial inhibition of penetration mediated by some of them. The binding of C1q to antibody-free human spermatozoa was also demonstrated both by means of indirect immunofluorescence and utilizing 125I-C1q.(ABSTRACT TRUNCATED AT 250 WORDS)

Failure to detect integrins of the beta-2 subclass on the human sperm surface

Several cell-to-cell recognition systems utilize the tripeptide Asp-Gly-Arg (RGD) as a cell surface signaling sequence. Mac-1, a member of the integrin subfamily defined by the beta-2 subunit, recognizes C3bi by means of an RGD sequence. Because C3 complement components have been detected on the gamete surfaces and RGD has been demonstrated to be involved in sperm-egg interaction, we explored the possibility that a member of the b2 integrin subfamily was present on the sperm surface and involved in egg recognition. Two methods were utilized to detect integrins on the sperm surface. Sperm were exposed to Mabs directed against different epitopes of each member of this integrin subfamily; and spermatozoa were tested for their ability to bind zymosan or yeast, since Mac-1 bearing cells possess this property. Both methods failed to demonstrate such integrins on the sperm surface, suggesting that another RGD receptor is involved in gamete recognition.

Inhibition of human sperm-zona pellucida tight binding in the presence of antisperm antibody positive polyclonal patient sera

Patient sera previously characterized as containing high levels of IgG and IgA antisperm antibodies that bound to the sperm surface, most specifically the head region, were evaluated for their effect on sperm-zona pellucida tight binding as assessed by the hemizona assay (HZA). Of the ten patient sera tested, 7 reduced zona binding by approximately half. Two of the most strongly inhibitory (greater than 70% inhibition) were examined for their effect on the prefertilization maturation of sperm. The patient sera did not affect sperm motion characteristics, or development of hyperactivated motility. However, in the presence of these sera some impedance was noted in calcium uptake after stimulation with human follicular fluid and in the acrosome reaction after calcium ionophore induction. Whether these two sera specifically affect sperm-zona pellucida binding or non-specifically affect the normal progression of capacitation remains to be eludicated.

Evidence that an Arg-Gly-Asp adhesion sequence plays a role in mammalian fertilization

The Arg-Gly-Asp (RGD) sequence is known to play a role in many recognition systems involved in cell-to-cell and cell-to-matrix adhesion. In our experiments we demonstrated that an RGD-dependent recognition is involved in sperm-oolemmal adhesion and egg penetration. Following coincubation of RGD-containing oligopeptides in a heterologous system (human sperm and zona-free hamster eggs), a significant decrease in the number of oolemma-adherent sperm was noted at 15 microM RGDV (Arg-Gly-Asp-Val) and at 5 microM GRGDTP (Gly-Arg-Gly-Asp-Thr-Pro), and fertilization was completely inhibited at 250 microM RGDV and 30 microM GRGDTP. In a homologous system (hamster sperm and zona-free hamster eggs), a concentration-dependent decrease in oolemmal adhesion and egg penetration was also noted, with complete inhibition of fertilization at 200 microM GRGDTP. The specificity of the receptor was confirmed by the fact that small changes in aminoacid composition impaired the peptide's effectiveness and that peptide-dependent inhibition of fertilization was partially reversible in competition studies. The presence of a molecule on the oolemma capable of binding the RGD sequence was demonstrated by using immunobeads coupled with an RGD-containing hexapeptide (GRGDTP), which rosetted over the egg surface in a manner reversible by the addition of free GRGDTP in the medium.

Effects of incubation time in serum and capacitation on spermatozoal reactivity with antisperm antibodies

Sperm reside within the female reproductive tract before the occurrence of fertilization. During this time they undergo surface modifications associated with changes in their functional state. To study their antigenic expression, capacitated and acrosome-reacted sperm were incubated with sera that had previously been tested for antisperm antibodies against fresh washed sperm, as detected by indirect immunobead binding. Forty-eight percent of previously positive and 20% of previously negative sera reacted differently with sperm after an extended time (18 hours) of incubation in serum or after sperm capacitation. These results suggest that current techniques of antisperm antibodies detection be modified to include testing sera after prolonged incubation times with both capacitated as well as fresh sperm.

Sperm-oolemmal interaction: role of the Arg-Gly-Asp (RGD) adhesion peptide

The Arg-Gly-Asp tripeptide (RGD) plays a widespread role in cell-to-cell and cell-to-matrix recognition. We demonstrated that an RGD-containing peptide (Arg-Gly-Asp-Val, RGDV) inhibits both oolemmal binding and penetration of zona-free hamster eggs by human spermatozoa in vitro when added to the incubation medium. These results suggest that RGD-containing proteins may play a role in sperm-oolemmal interactions required for fertilization.

Antisperm antibodies induce polyspermy by promoting adherence of human sperm to zona-free hamster eggs

Certain antisperm antibodies (ASAs) in the sera of infertile men or women promote the penetration of zona-free hamster eggs by spermatozoa. We have shown previously that this enhancement of penetration occurs through mechanisms other than an alteration in the acrosomal structure of antibody-labelled spermatozoa. In the present study, small limited populations of antibody-labelled and antibody-free spermatozoa from fertile donors were observed serially by phase contrast, epifluorescence and scanning electron microscopy following their adherence to the oolemma of zona-free hamster eggs. The adherence of ASA-labelled spermatozoa to the zona-free hamster egg was markedly increased and occurred earlier when compared with antibody-free spermatozoa from the same ejaculate. The likelihood of entry of an antibody-labelled spermatozoon into the ooplasm, however, once adherent to the oolemma was not different to that of an antibody-free spermatozoa, and the ultrastructural steps of incorporation of antibody-labelled human spermatozoa were also similar to those observed during fertilization of hamster eggs by spermatozoa of several other species. These observations indicate that ASAs promote polyspermic fertilization of zona-free hamster eggs primarily through their enhancement of sperm--oolemmal binding.

Identification of an oolemmal IgG Fc receptor: its role in promoting binding of antibody-labelled human sperm to zona-free hamster eggs

Antisperm antibodies (ASAs) present in sera of infertile men and women have been shown either to promote or inhibit penetration of zona-free hamster eggs by antibody-labelled human spermatozoa. Increased numbers of oolemmal-bound sperm have been noted in association with increased sperm penetration frequencies, following antibody labelling, when compared with antibody-free sperm. The promotion of adherence of ASA-labelled sperm to the oolemma could be mediated through the binding of antibodies to common epitopes present on the sperm and egg surfaces or through Fc-mediated binding to an oolemmal Fc receptor. In support of the latter hypothesis, we report that zona-free hamster eggs bind aggregated human IgG and IgG Fc fragments. The presence of an oolemmal IgG Fc receptor has been confirmed using a rat monoclonal antibody (2.4G2) directed against a murine IgG Fc receptor (Fc gamma RII) as judged both by indirect immunofluorescence and by immunobead binding. In addition, the pre-incubation of zona-free hamster eggs with IgG Fc diminished both adhesion to and penetration of the oolemma by human spermatozoa.

Characterization of humoral antibodies reactive with spermatozoa, N-acetyl galactosamine, and a putative blood group antigen in seminal plasma

Antisperm antibodies in sera of infertile women may react differently with spermatozoa of different men. We studied the reactivity of these antibodies with spermatozoa from men of varying blood group status. Increased immunoglobulin binding to sperm of group A or AB men was noted when compared with group O men. A diminution in binding of immunoglobulins to spermatozoa after absorption of these sera with human group A or AB red blood cells was noted as well as after coincubation of sera and sperm with N-acetyl galactosamine, the terminal sugar of blood group antigen A. These observations suggest that antibodies directed against blood group antigens adsorbed to sperm of secretor males may account in part for variations in immunobead binding levels between sperm of different men.

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.

The long-term predictive value of the zona-free hamster ova sperm penetration assay

Three hundred sixty-nine infertile couples were followed for 2 to 5 years in a study designed to determine the clinical long-term predictive value of the zona-free hamster ova sperm penetration assay (SPA). Semen analysis (SA), SPA, and a full infertility workup were done in all cases, and only couples in whom the female had no evident cause of infertility were included in the study. During the follow-up period, 106 couples (29%) achieved a pregnancy. Sixteen percent of 131 men who had an SPA of 0%, 23% of 120 men with 1% to 19%, and 48% of 118 men who had a penetration of greater than 19% impregnated their wives 2 to 5 years after the assays. Significant difference in fertility prognosis was found between those who had an SPA greater than 19% and those with an SPA less than 20% (48% versus 20%). Sperm penetration assay greater than 19% was predictive of higher pregnancy rates in both oligospermic (41% versus 17%) and unexplained infertile couples (52% versus 24%). The specificity and positive predictive values of the SPA were higher than those of the SA (77% versus 57% and 48% versus 37%). These findings emphasize the value and importance of the SPA in determining the long-term fertility potential of men.

Effects of anti-sperm antibodies on human sperm ultrastructure and function

The ultrastructural appearance of a highly motile population of spermatozoa from a fertile donor was evaluated following antibody labeling with each of several sperm head-directed anti-sperm antibodies (ASAs) and subsequent incubation in a capacitating medium in vitro. Acrosomes were classified into categories which are believed to represent stages in the acrosome reaction. Quantitative analysis revealed no difference in acrosomal morphology of antibody-labeled sperm between treatment groups despite a varying degree of enhancement or inhibition of sperm egg-penetrating ability. We conclude that ASAs affect gamete interaction through mechanisms other than an alteration in the acrosome reaction.

Documentation of IgA1 and IgA2 antisperm antibodies within seminal fluid

Antisperm antibodies of the IgA class, when bound to sperm, impair the sperm's ability to penetrate cervical mucus. IgA proteases offer a potential treatment of autoimmunity to spermatozoa in infertile men by enzymatically degrading immunoglobulins on the sperm surface. As IgA1 but not IgA2 is cleaved by IgA proteases, we determined through use of IgA subclass-specific monoclonal antibodies the presence and relative proportions of antisperm IgA1 and IgA2 in seminal fluid. This ratio varies substantially between men, perhaps reflecting differences in the etiology of autoimmunity to sperm.

Intrauterine insemination as treatment for antisperm antibodies in the female

Ninety-one women with long-standing infertility in the presence of humoral antisperm antibodies (ASA) underwent 473 cycles of intrauterine insemination of washed sperm (IUI), resulting in 26 pregnancies. Nine pregnancies were achieved in 67 women who underwent 285 IUI during unstimulated cycles (13% pregnancy rate; 3% pregnancy/cycles of treatment). Twenty women underwent 86 IUI after clomiphene citrate (CC) stimulation, resulting in 6 pregnancies (30%; 7% per cycle), while 28 underwent 102 cycles of IUI after human menopausal gonadotropins (hMG) stimulation, resulting in 11 pregnancies (39%; 11% per cycle). Twenty-one of the 26 pregnancies (81%) were achieved in the first 2 IUI cycles. During unstimulated and CC IUI cycles, all pregnancies occurred in the first two cycles of treatment, while with hMG stimulation pregnancies also occurred in the third, fourth, and fifth IUI cycles. Nine of these 91 women subsequently conceived spontaneously, and three others conceived through in vitro fertilization. Only 6 of the 38 pregnancies resulted in spontaneous abortion (16%). Thus, pregnancies achieved in women with ASA have no increased risk of abortion.

Luteal phase sera and progesterone enhance sperm penetration in the hamster egg assay

The hormonal factors responsible for variation in sperm penetration rates of zona-free hamster ova caused by the use of human sera were investigated. Sera obtained at different times in the menstrual cycle, 17-beta estradiol (E2), or progesterone (P) was added to Biggers Whitten and Whittingham (BWW) medium used for the sperm penetration assay. Luteal phase sera enhanced egg penetration significantly when compared with either follicular or preovulatory sera (48.8% versus 23% and 25%; P less than 0.01). E2 at concentrations of 2 pg/ml to 2 X 10(6) pg/ml had no effect on sperm motility or egg penetration. Addition of P to control media at final concentrations of 0.5 to 50 ng/ml caused a significant elevation of egg penetration (68% to 91% to 96%; P less than 0.01) without affecting sperm motility. Since P has been shown to have a direct effect on plasma membranes and to bind to spermatozoan plasma membrane, the authors propose that P could have a physiologic role during capacitation or sperm egg interaction in vivo.

Detection in human sera of antibodies directed against the hamster egg oolemma

Heteroantibodies were demonstrated by indirect immunofluorescence in human sera, which reacted with unfertilized and fertilized hamster eggs. Oolemmal antigens to which these antibodies were directed were distinct from antigen present on the surface of living human spermatozoa. Both species-specific and tissue-specific heteroantibodies were demonstrated by absorption with hamster liver and ovary. An increased degree of heteroantibody binding was noted following penetration of zona-free hamster eggs by human spermatozoa, indicating that an alteration in oolemmal antigen distribution had occurred. No evidence was found, however, that antisperm antibodies in these sera reacted with zona-free hamster eggs following their fertilization.

Seminal fluid antisperm antibodies do not reflect those present on the sperm surface

Given the increasing evidence that head-directed antibodies can impair fertilization in vitro, as well as play a role in the impaired entry of sperm into cervical mucus, our findings provide strong support for the direct analysis of immunoglobulins bound to the sperm surface, rather than by indirect analysis through the study of seminal fluid.

Effects of sperm-reactive monoclonal antibodies on the cervical mucus penetrating ability of human spermatozoa

A group of monoclonal antibodies (Mabs) was tested by immunobead binding and indirect immunofluorescence to determine its reactivity with antigenic moieties present either on the surface of motile human spermatozoa or internally. Those Mabs reactive with the surface of motile spermatozoa impaired their ability to penetrate cervical mucus in vitro, while Mabs solely reactive with freeze-thawed, nonmotile sperm (presumptive subsurface epitopes) were without effect on sperm function.

The effect of an IgA1 protease on immunoglobulins bound to the sperm surface and sperm cervical mucus penetrating ability

A major site of impaired fertility in men with autoimmunity to sperm rests at the level of restricted sperm entry and motion within cervical mucus. We studied the effects of a protease derived from Neisseria gonorrhoeae, whose substrate specificity is limited to human IgA1, on the ability of antibody-bound sperm to penetrate human cervical mucus in vitro. IgA on the sperm surface, but not IgG, was degraded by IgA1 protease. A correlation was seen between the levels of IgA bound relative to IgG and the improvement in sperm cervical mucus penetrating ability after IgA1 protease exposure. These results provide evidence that antisperm autoantibodies of both IgA and IgG classes impair the ability of spermatozoa to populate the female reproductive tract. They implicate the Fc region of the immunoglobulin molecule in mediating this effect and offer the potential to restore male fertility by treating antibody-bound sperm in vitro with immunoglobulin-directed bacterial proteases, before insemination.