Production of single-chain fragment variable (scFv) antibodies specific to plasma membrane epitopes on bull Y-bearing sperm

Novel single-chain fragment variable antibody targeting plasma membrane epitopes on porcine Y-chromosome-bearing sperm

The aim of this study was to construct and produce a single-chain fragment variable (scFv) antibody targeting the plasma membrane epitope on porcine Y-chromosome-bearing sperm (Y-sperm). The hybridoma cloned from 4D1-E8 exhibited the highest specificity, and Y-sperm was used to generate the scFv gene. The expected combination of 450 bp (VH) and 300 bp (VL) resulted in a 795 bp scFv gene. The scFv gene was inserted into the pET22b expression vector and expressed in E. coli BL21 (DE3). The resulting H4:L4 clone produced a highly specific scFv antibody to Y-sperm. The reactivity of the H4:L4 scFv antibody to porcine Y-sperm was confirmed via ELISA and flow cytometry. The H4:L4 scFv antibody exhibited low cross-reactivity with X-sperm (4.14%). The soluble H4:L4 scFv antibody exhibited significantly less cross-reactivity with X-sperm than did the 4D1-E8 mAb (4.14% vs. 15.5%). However, H4:L4 scFv and the 4D1-E8 mAbs had high cross-reactivity with other conventional livestock semen. The scFv antibodies and mAbs were detected on the Y-sperm surface via immunofluorescence, and the fluorescence intensities were particularly strong on the plasma membranes of Y-sperm. In this study, the production of a scFv antibody against porcine Y-sperm was successful and represents a novel achievement. This scFv antibody had a high affinity for porcine Y-sperm. The soluble scFv antibody and mAb can be used to sort Y- and X-sperm in treatments involving porcine semen bearing X or Y chromosomes.

Production of monoclonal antibodies targeting plasma membrane of porcine Y-chromosome-bearing sperm

The pig industry is interested in increasing the number of female piglets by using sexed semen. Immunological sperm sexing is a promising method. This study investigated and produced a monoclonal antibody (MAbs) targeted to plasma membrane epitopes on porcine Y-chromosome-bearing sperm. Two BALB/c mice were immunized with 92.08 % high-purity porcine Y-sperm, which was separated by a cell sorter flow cytometer. The hybridoma cells were a fusion of myeloma cells (P3X63Ag8.653) and splenocyte cells from immunized mice. Indirect ELISA screening for positive antibodies produced by a single clone well (C2B2) with a high titer specific to porcine Y-sperm. The C2B2 clone was used to produce and purify C2B2-MAbs, yielding 2.78 ± 0.78 µg/mL. The C2B2-MAbs was highly specific to Y-sperm (100.00 %) and had a low cross-reactivity with X-sperm (3.25 %). Therefore, the percentage cross-reactivity of C2B2-MAbs was low for conventional sperm from various livestock, including 0.34 % for Angus, 0.38 % for Holstein-Friesian, 0.20 % for goats, and 0.25 % for buffalo. The bright fluorescence of FITC displayed by the C2B2-MAbs bound to the plasma membrane of porcine Y-sperm provided evidence of affinity between them. However, the C2B2-MAbs bound to an X-sperm lacked fluorescence. C2B2-MAbs showed specificity for the plasma membrane of porcine Y-sperm, which can be used in porcine semen sexing in further studies.

Advances in immunological sorting of X and Y chromosome-bearing sperm: from proteome to sex-specific proteins

Sex determination is the developmental assignment that results from genetic factors. The sexual characters were the specific manifestations of male and female individuals under stimulation of sexual hormonal production. The fusion of an oocyte with an X chromosome-bearing sperm will lead to a female (XX), while fusion with a Y chromosome-bearing sperm will develop into a male (XY) in mammals. Sexing technology has been developed to fertilize eggs with sorted sperm, producing offspring of the desired sex. Sperm sorting enables the sex pre-determination of offspring via in vitro fertilization (IVF) or artificial insemination (AI) in domestic animals. Flow cytometric sorting of X and Y sperm is widely considered the most applied method for sperm sorting and has been commercially applied in cattle. However, a non-invasive, immunological method for screening X and Y sperm is considered to be a feasible approach. This review summarizes the current knowledge and techniques of sperm immunological sorting, including the preparation of antibodies, application of immunomodulators, and immunoisolation. Additionally, we focus on identifying sex-specifically expressed proteins in X and Y sperm through proteomic analysis, and verifying the sex-specific proteins using experimental techniques. Furthermore, several housekeeping proteins as loading control were discussed in immunoblotting of sperm proteins. Immunological sorting of X and Y sperm could provide a convenient, cost-effective, and highly efficient technique that can improve economic benefits and achieve an advanced level of sexing technology. This review provides insight into immunological sorting of sperm and the pre-determination of sex in farm animals.

Sperm quality variables of sex-sorted bull semen produced by magnetic-activated cell sorting coupled with recombinant antibodies targeting Y-chromosome-bearing sperm

The immunological sexing method using antibodies offers cost-effective, high-volume production but faces challenges in terms of X-sperm purity in sexed semen. This research aimed to produce sexed bull semen using highly specific recombinant antibodies in magnetic-activated cell sorting (MACS), evaluate sperm quality and kinematic parameters, and verify the sex ratio of sperm, embryos, and live calves. Fresh semen from two Angus bulls was separated into two equal groups: conventional (CONV) semen and semen sexed using MACS with Y-scFv antibody conjugation to separate two fractions, i.e., the X-enriched and Y-enriched fractions. Then, computer assisted semen analysis and imaging flow cytometry were used to evaluate sperm motility and kinematic variables, acrosomal integrity, sperm viability, and sperm sex ratios. The results showed that sperm motility and quality did not differ between X-enriched and CONV semen. However, the Y-enriched fraction showed significantly lower sperm quality than the X-enriched fraction and CONV semen. The sperm ratio revealed that X-sperm accounted for up to 79.50% of the X-enriched fraction, while Y-sperm accounted for up to 78.56% of the Y-enriched fraction. The sex ratio of embryos was examined using in vitro fertilization. The cleavage rates using CONV and X-enriched semen were significantly higher than that using Y-enriched semen. Accordingly, 88.26% female blastocysts were obtained by using X-enriched semen, and 83.58% male blastocysts were obtained by using Y-enriched semen. In farm trials, 304 cows were subjected to AI using X-enriched and CONV semen. The pregnancy rate did not differ between the X-enriched and CONV semen groups. On the other hand, X-enriched semen generated significantly more live female calves (83.64%) than CONV semen (47.00%). The MACS sexing method significantly enhanced the X-sperm purity in sexed semen, producing high-quality sperm, a high percentage of female blastocytes, and a high percentage of live female calves.

Biochemical Features of X or Y Chromosome-Bearing Spermatozoa for Sperm Sexing

This review presents information on biochemical features of spermatozoa bearing X or Y chromosome, enabling production of a sperm fraction with pre-defined sex chromosome. The almost only technology currently used for such separation (called sexing) is based on the fluorescence-activated cell sorting of sperm depending on DNA content. In addition to the applied aspects, this technology made it possible to analyze properties of the isolated populations of spermatozoa bearing X or Y chromosome. In recent years, existence of the differences between these populations at the transcriptome and proteome level have been reported in a number of studies. It is noteworthy that these differences are primarily related to the energy metabolism and flagellar structural proteins. New methods of sperm enrichment with X or Y chromosome cells are based on the differences in motility between the spermatozoa with different sex chromosomes. Sperm sexing is a part of the widespread protocol of artificial insemination of cows with cryopreserved semen, it allows to increase proportion of the offspring with the required sex. In addition, advances in the separation of X and Y spermatozoa may allow this approach to be applied in clinical practice to avoid sex-linked diseases.

High-Efficiency Bovine Sperm Sexing Used Magnetic-Activated Cell Sorting by Coupling scFv Antibodies Specific to Y-Chromosome-Bearing Sperm on Magnetic Microbeads

Sperm sexing technique is favored in the dairy industry. This research focuses on the efficiency of bovine sperm sexing using magnetic-activated cell sorting (MACS) by scFv antibody against Y-chromosome-bearing sperm (Y-scFv) coupled to magnetic microbeads and its effects on kinematic variables, sperm quality, and X/Y-sperm ratio. In this study, the optimal concentration of Y-scFv antibody coupling to the surface of magnetic microbeads was 2–4 mg/mL. PY-microbeads revealed significantly enriched Y-chromosome-bearing sperm (Y-sperm) in the eluted fraction (78.01–81.43%) and X-chromosome-bearing sperm (X-sperm) in the supernatant fraction (79.04–82.65%). The quality of frozen–thawed sexed sperm was analyzed by CASA and imaging flow cytometer, which showed that PY-microbeads did not have a negative effect on X-sperm motility, viability, or acrosome integrity. However, sexed Y-sperm had significantly decreased motility and viability. The X/Y-sperm ratio was determined using an imaging flow cytometer and real-time PCR. PY-microbeads produced sperm with up to 82.65% X-sperm in the X-enriched fraction and up to 81.43% Y-sperm in the Y-enriched fraction. Bovine sperm sexing by PY-microbeads showed high efficiency in separating Y-sperm from X-sperm and acceptable sperm quality. This initial technique is feasible for bovine sperm sexing, which increases the number of heifers in dairy herds while lowering production expenses.

Antibody-Conjugated Magnetic Beads for Sperm Sexing Using a Multi-Wall Carbon Nanotube Microfluidic Device

This study proposes a microfluidic device used for X-/Y-sperm separation based on monoclonal antibody-conjugated magnetic beads, which become positively charged in the flow system. Y-sperms were selectively captured via a monoclonal antibody and transferred onto the microfluidic device and were discarded, so that X-sperms can be isolated and commercially exploited for fertilization demands of female cattle in dairy industry. Therefore, the research team used monoclonal antibody-conjugated magnetic beads to increase the force that causes the Y-sperm to be pulled out of the system, leaving only the X-sperm for further use. The experimental design was divided into the following: Model 1, the microfluid system for sorting positive magnetic beads, which yielded 100% separation; Model 2, the sorting of monoclonal antibody-conjugated magnetic beads in the fluid system, yielding 98.84% microcirculation; Model 3, the sorting of monoclonal antibody-conjugated magnetic beads with sperm in the microfluid system, yielding 80.12% microcirculation. Moreover, the fabrication microfluidic system had thin film electrodes created via UV lithography and MWCNTs electrode structure capable of erecting an electrode wall 1500 µm above the floor with a flow channel width of only 100 µm. The system was tested using a constant flow rate of 2 µL/min and X-/Y-sperm were separated using carbon nanotube electrodes at 2.5 V. The structure created with the use of vertical electrodes and monoclonal antibody-conjugated magnetic beads technique produced a higher effective rejection effect and was able to remove a large number of unwanted sperm from the system with 80.12% efficiency.

Spermatological parameters of immunologically sexed bull semen assessed by imaging flow cytometry, and dairy farm trial

This study compared the quality parameters of bull semen sexed using an immunological method with those of conventional semen by imaging flow cytometry and applied this semen in dairy farm trials. Semen samples were collected from ten ejaculates from five bulls. Each sample was divided into two treatments: conventional semen (CON) and semen sexed using monoclonal male-specific antibodies combined with the complement system for cytotoxicity reaction (IC-sexed). After obtaining frozen-thawed semen, we used imaging flow cytometry to assess acrosome integrity, sperm sex ratio and viability. Sperm morphology was evaluated using eosin-nigrosin staining. The percentage acrosome integrity did not differ between IC-sexed and CON semen (P = 0.313). The sperm sex ratio showed that the percentage of live X-chromosome-bearing sperm was higher than that of live Y-chromosome-bearing sperm in IC-sexed semen (P = 0.001). IC-sexed semen showed a higher percentage of head and tail defects than did CON semen (P = 0.019). In field trials, 585 cows were subjected randomly to AI with CON or IC-sexed semen. The pregnancy rate of the IC-sexed group did not differ from that of the CON group (P = 0.535). However, IC-sexed semen produced a significantly higher percentage of female calves than did CON semen (P = 0.031). Thus, immunological sexing did not adversely affect the acrosome integrity of sperm. Furthermore, a female calf birth rate of over 74 % can potentially be achieved using IC-sexed semen. These findings could help farmers to replace heifers in their herds.