LALAPG variant of the Human Contraception Antibody (HCA) reduces Fc-mediated effector functions while maintaining sperm agglutination activity.

High rates of unintended pregnancies worldwide indicate a need for more accessible and acceptable methods of contraception. We have developed a monoclonal antibody, the Human Contraception Antibody (HCA), for use by women in vaginal films and rings for contraception. The divalent F(ab')2 region of HCA binds to an abundant male reproductive tract-specific antigen, CD52g, and potently agglutinates sperm. Certain other antibody activities mediated by the Fc region such as mucus trapping, complement-dependent cytotoxicity (CDC) and antibody-dependent cellular phagocytosis (ADCP) could have beneficial or negative effects. The purpose of this study was to document HCA Fc effector functions and determine whether an engineered variant of HCA with a modified Fc region, HCA-LALAPG, retains desirable contraceptive activity while minimizing Fc-mediated effects. Fab and Fc functions were compared between HCA and HCA-LALAPG. Fab activity was assessed using sperm agglutination and modified swim-up ("sperm escape") assays. Fc functions were assessed by CDC (sperm immobilization), ADCP, and cervical mucus penetration assays. HCA and HCA-LALAPG showed equivalent activity in assays of Fab function. In the assays of Fc function, HCA supported strong CDC, ADCP, and sperm trapping in cervical mucus whereas HCA-LALAPG demonstrated little to no activity. HCA and the HCA-LALAPG variant were both highly effective in the sperm agglutination assays but differed in Fc mediated functions. Use of the HCA-LALAPG variant for contraception in women could reduce antibody-mediated inflammation and antigen presentation but may have reduced contraceptive efficacy due to much weaker sperm trapping in mucus and complement-dependent sperm immobilization activity.

Canine-specific tail-in, head-out sperm agglutination.

An interesting pattern of tail-in, head-out sperm agglutination was identified in a Brucella canis seronegative subfertile dog. Centrifuged seminal plasma from this dog could induce a similar pattern of agglutination in six other dogs, but not in ejaculates from a single stallion and two rams. The agglutination pattern was short-lived and appeared to depend on motility of spermatozoa, although intensity of agglutination may have been affected by concentration of agglutinating factor.

Caffeine induces sperm detachment from sperm head-to-head agglutination in bull.

Sperm head-to-head agglutination is a well-known known phenomenon in mammalian and non-mammalian species. Although several factors have been reported to induce sperm agglutination, information on the trigger and process of sperm detachment from the agglutination is scarce. Since hyperactivated motility is involved in bovine sperm detachment from the oviduct, we focused on caffeine, a well-known hyperactivation inducer, and aimed to determine the role of caffeine in sperm detachment from agglutination. Agglutination rate of bovine sperm was significantly decreased upon incubation with caffeine following pre-incubation without caffeine. Additionally, we observed that bovine sperm were detached from agglutination only when the medium contained caffeine. The detached sperm showed more asymmetrical flagellar beating compared to the undetached motile sperm, regardless of whether before or after the detachment. Intriguingly, some sperm that detached from agglutination re-agglutinated with different sperm agglutination. These findings indicated caffeine as a trigger for sperm detachment from the agglutination in bull. Furthermore, another well-known hyperactivation inducer, thimerosal, also significantly reduced the sperm agglutination rate. Overall, the study demonstrated the complete process of sperm detachment from sperm head-to-head agglutination and proposed that hyperactivated motility facilitates sperm detachment from another sperm. These findings would provide a better understanding of sperm physiology and fertilization process in mammals.

Flow-cytometric analysis of membrane integrity of stallion sperm in the face of agglutination: the "zombie sperm" dilemma.

PURPOSE: To define the effect of sperm agglutination, associated with incubation under capacitating conditions, on accuracy of membrane assessment via flow cytometry and to develop methods to mitigate that effect. METHODS: Sperm motility was measured by CASA. Sperm were stained with PI-PSA or a novel method, LD-PSA, using fixable live/dead stain and cell dissociation treatment, before flow-cytometric analysis. Using LD-PSA, acrosome reaction and plasma membrane status were determined in equine sperm treated with 10 µm A23187 for 10 min, followed by 0, 1, or 2 h incubation in capacitating conditions. RESULTS: Using PI-PSA, measured membrane integrity (MI; live sperm) was dramatically lower than was total motility (TMOT), indicating spurious results ("zombie sperm"). Sperm aggregates were largely of motile sperm. Loss of motility after A23187 treatment was associated with disaggregation and increased MI. On disaggregation using LD-PSA, MI rose, and MI then corresponded with TMOT. In equine sperm incubated after A23187 treatment, as the percentage of live acrosome-reacted sperm increased, TMOT decreased to near 0. CONCLUSION: Flow cytometry assesses only individualized sperm; thus, agglutination of viable sperm alters recorded membrane integrity. As viable sperm become immotile, they individualize; therefore, factors that decrease motility, such as A23187, result in increased measured MI. Disaggregation before assessment allows more accurate determination of sperm membrane status; in this case we documented a mismatch between motility and live acrosome-reacted equine sperm that may relate to the poor repeatability of A23187 treatment for equine IVF. These findings are of profound value to future studies on sperm capacitation.

Effects of exogenous lactoferrin on characteristics and functions of bovine epididymal, ejaculated and frozen-thawed sperm.

The purpose of this study was to investigate effects of addition of lactoferrin on characteristics and functions of bovine epididymal, ejaculated, and frozen-thawed sperm. The addition of lactoferrin was significantly (p < .05) effective on increasing values of progressive motility, straightness, and linearity in caput epididymal sperm and values of motility in cauda epididymal sperm. When ejaculated sperm were incubated in capacitation medium, percentages of motile and progressively motile sperm decreased largely within the first period of 30 min, followed by only minor changes. However, the addition of lactoferrin significantly lessened the early decreases of these parameters and additionally promoted capacitation-dependent changes of chlortetracycline staining patterns (from F pattern to B pattern). In other experiments, when ejaculated sperm were exposed to oxidative stress with 100-µM H2 O2 , the addition of lactoferrin partially protected them from dysfunction of flagellar movement and loss of progressive movement. In final experiments with frozen-thawed samples incubated in the capacitation medium, the addition of lactoferrin effectively survived dying sperm and suppressed occurrence of sperm agglutination. These results may suggest biological and biotechnological potentials of lactoferrin for modulation of bovine sperm viability, motility, capacitation state, and preservation in vitro.

Effects of chelating calcium in cryopreservation extender on frozen-thawed dog semen / [Efeitos da quelação de cálcio no meio de criopreservação no sêmen descongelado de cão]

We evaluated the effect of reducing free calcium in the cryopreservation medium, using the calcium chelator ethylene diamine tetracetic acid (EDTA) at 0.3% and 0.5% concentrations. Three male mixed breed dogs were subjected to semen collection by digital manipulation (n=16). Each ejaculate was divided in three aliquots, and each one was diluted in TRIS-glucose-egg yolk extender with 6% glycerol and 0.5% Equex STM Paste® (TGE, control); and added with 0.3% EDTA (EDTA 0.3) or 0.5% EDTA (EDTA 0.5). Calcium concentration reduced in EDTA 0.3 and all the calcium ions were chelated in EDTA 0.5. The EDTA addition did not affect sperm morphology or plasma membrane integrity; however, by removing all free calcium (EDTA 0.5), the sperm motility reduced (64.7% in TGE and 45% in EDTA 0.5; p<0.05). Acrosome integrity and sperm binding ability were not improved by calcium chelation. The failure to prevent the premature AR may explain why sperm longevity was not affected by calcium removal. Thus, the partial or complete calcium removal, through EDTA addition, is not able to prevent acrosomal damage or premature acrosomal reaction, and therefore does not improve the dog sperm binding ability.(AU)

Avaliou-se o efeito da redução do cálcio livre no meio de congelamento, usando-se o quelante de cálcio etilenodiaminotetracético (EDTA) a 0,3% e 0,5%. Três cães machos sem raça definida foram submetidos à coleta de sêmen por manipulação digital (n=16). Cada ejaculado foi diluído em diluidor controle com TRIS-glicose - gema de ovo (TGE, controle), ou em diluidor TGE enriquecido com 0,3% (EDTA 0,3) ou 0,5% de EDTA (EDTA 0,5). A concentração de cálcio reduziu no meio EDTA 0,3, e todos os íons de cálcio foram quelados no meio EDTA 0,5. A adição do EDTA e a consequente quelação do cálcio não afetaram a morfologia espermática ou a integridade da membrana plasmática, no entanto, ao remover todo o cálcio do meio (EDTA 0,5), a motilidade espermática se reduziu (64,7% no TGE e 45% no EDTA 0,5; P<0,05). A integridade do acrossoma e a capacidade de ligação do espermatozoide não melhoraram com a quelação do cálcio. Apesar da influência da concentração de cálcio sobre a motilidade espermática após o descongelamento, a falha em prever a reação acrossomal prematura pode explicar por que a longevidade espermática não foi afetada pela remoção do cálcio no meio. Dessa forma, a remoção parcial ou total do cálcio, por meio da adição de EDTA, não é capaz de prevenir o dano no acrossoma ou a reação acrossomal prematura e, portanto, não aumenta a capacidade do espermatozoide de se ligar ao oócito.(AU)

Engineering tetravalent IgGs with enhanced agglutination potencies for trapping vigorously motile sperm in mucin matrix.

Multivalent antibodies such as sIgA can crosslink motile entities such as sperm and bacteria, creating agglomerates that are too large to permeate the dense mucin matrix in mucus, a process commonly referred to as immune exclusion. Unfortunately, sIgA remains challenging to produce in large quantities, and easily aggregates, which prevented their use in clinical applications. To develop sIgA-like tetravalent antibodies that are stable and can be easily produced in large quantities, we designed two IgGs possessing 4 identical Fab domains, with the Fabs arranged either in serial or in the diametrically opposite orientation. As a proof-of-concept, we engineered these tetravalent IgG constructs to bind a ubiquitous sperm antigen using a Fab previously isolated from an immune infertile woman. Both constructs possess at least 4-fold greater agglutination potency and induced much more rapid sperm agglutination than the parent IgG, while exhibiting comparable production yields and identical thermostability as the parent IgG. These tetravalent IgGs offer promise for non-hormonal contraception and underscores the multimerization of IgG as a promising strategy to enhance antibody effector functions based on immune exclusion.

Characteristics and Possible Role of Bovine Sperm Head-to-Head Agglutination.

Although sperm head-to-head agglutination has been reported in many mammalian species, the biological significance of this unique sperm-sperm interaction remains largely unknown. Here, we aimed to examine the functional characteristics of agglutinated bovine sperm to determine the possible role of sperm agglutination in the fertilization process. We initially examined temporal changes to the degree of head-to-head agglutination in culture, and found that bovine sperm agglutinated despite the lack of sperm agglutination inducers in medium. Sperm viability and motility were evaluated by SYBR14/PI and JC-1 staining, respectively, to identify the relationship between sperm agglutination and fertilizing ability. Agglutinated sperm had increased motility, viability, and intact mitochondrial function compared with unagglutinated sperm. Furthermore, we found that heparin significantly increased the percentage of unagglutinated sperm, but did not affect viability of both agglutinated and unagglutinated sperm, suggesting that sperm agglutination dictated the viability. In conclusion, agglutinated bovine sperm maintained viability and motility for a longer time than unagglutinated sperm. Thus, we propose that the head-to-head agglutination is a crucial sperm-sperm interaction to ensure the fertilizing ability of sperm.

Role of Lactobacillus in Female Infertility Via Modulating Sperm Agglutination and Immobilization.

Infertility has become a common problem in recent decades. The pathogenesis of infertility is variable, but microbiological factors account for a large proportion of it. Dysbiosis of vaginal microbiota is reportedly associated with female infertility, but the influence of normal vaginal microbiota on infertility is unclear. In this review, we summarize the physiological characteristics of the vaginal tract and vaginal microbiota communities. We mainly focus on the bacterial adherence of vaginal Lactobacillus species. Given that the adherent effect plays a crucial role in the colonization of bacteria, we hypothesize that the adherent effect of vaginal Lactobacillus may also influence the fertility of the host. We also analyze the agglutination and immobilization effects of other bacteria, especially Escherichia coli, on ejaculated spermatozoa, and speculate on the possible effects of normal vaginal microbiota on female fertility.

Evaluation of Sperm Impairing Factor from Serratia marcescens as Male Contraceptive in Mouse Model.

The present study was carried out to assess the contraceptive efficacy of sperm agglutinating factor (SAF) isolated from Serratia marcescens, in male Balb/c mice. Mice were administered via an intratesticular route with different concentrations of SAF, viz., 10, 50, 100, 200, or 400 µg, in the right testis only which served as a test while the left side served as control except otherwise stated. Mice were sacrificed on day 3, 7, 14, 21, 30, 45, 60, and 90 after administration, and results in terms of change in body weight, seminal parameters, tissue somatic indices (TSI), hematological parameters, serum level of testosterone, lipid peroxidation, and histology were studied. The body weight and TSI remained unaffected in all the experimental groups. In case of seminal parameters, the right testis treated with 10 µg, 50 µg, 100 µg, 200 µg, or 400 µg of SAF showed azoospermia up to day 7, 14, 21, 45, and 90, respectively. The hematological indices, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) were found to be unaltered when the group receiving SAF (test) was compared with the groups receiving phosphate buffer saline (control) in the right testis; however, the treatment had a negative effect on the serum level of testosterone. It also affected the oxidative status of the right testis. Furthermore, histological studies revealed hypospermatogenesis and alterations in the seminiferous tubules which included intraepithelial vacuolation and exfoliation in the right side as compared to the left side. Thus, the results suggest that SAF (400 µg) causes suppression of spermatogenesis, without causing apparent toxic effects.