Preparation, Characterization, and Determination of Immunological Activities of Transfer Factor Specific to Human Sperm Antigen

Objective. The objective of this study was to prepare, characterize, and determine immunological activities of specific transfer factor (STF) specific to human sperm antigen (HSA) for the preparation of antisperm contraceptive vaccine that can be used as an immunocontraceptive. Methods. HSA-STF was prepared using the spleens of rabbits vaccinated with HSA. The specific immunological activities were examined by lymphocyte proliferation test (LPT), leukocyte adhesion inhibition test (LAIT), and by determining the concentrations of IL-4, γ-IFN, and IL-21. HSA-STF was a helveolous substance, having a pH value of 7.0 ± 0.4 and UV absorption maxima at 258 ± 6 nm. It contained seventeen amino acids; glycine and glutamic acids were the highest in terms of concentrations (38.8 μg/mL and 36.3 μg/mL, resp.). Results. The concentration of polypeptide was 2.34 ± 0.31 mg/mL, and ribose was 0.717 ± 0.043 mg/mL. The stimulation index for lymphocyte proliferation test was 1.84, and the leukocyte adhesion inhibition rate was 37.7%. There was a statistically significant difference between the cultural lymphocytes with HSA-STF and non-HSA-STF for γ-IFN and IL-21 (P < 0.05), but there was no statistical significance for IL-4 (P > 0.05). Conclusion. HSA-STF was prepared and characterized successfully. It had immunological activity which could transfer the immune response specific to HSA and prove to be a potential candidate for the development of male immunocontraceptive agents.


Introduction
e burgeoning population has major implications worldwide. In the face of this problem, birth control was regarded as important by many countries. Contraception is the key measure for birth control, but traditional measures have been misused in many ways; for example, easy desquamation of intrauterine ring, possible injury to person with hypodesmus, side effects of contraceptive, and condom effects. Currently available contraceptive methods are not well suited to the religious, social, economic, or health circumstances worldwide. So, there is an urgent need to develop harmless, retrievable products for contraception. Reproductive science has provided a range of fertility control measures for women, but the choices for men are few and currently limited to condoms and vasectomy [1]. Various health organizations and pharmaceutical companies actively continue to pursue research towards new contraceptive approaches [2]. Presently, based on the variable antigens (Ags) existing in the male reproductive system, researchers have developed many antibodies (Abs) or vaccines for contraception, such as Abs to SP-10 expressed in the testis that could interfere with the union of sperm and ovum [3]. e sperm-speci�c protein, Izumo, a member of immunoglobulin superfamily (IgSF) which is located on the sperm stimulates hamster to secrete high titer of Abs both in the genital tract and serum and further decreases their reproductive capability [4]. Antibodies to Eppin (epididymal protease inhibitor), a newly found protein secreted by testis and epididymis, could itself act as a candidate vaccine because of its ability to regulate the liquefaction of semen and limit sperm motility [5,6]. ere are several evident shortcomings regardless of the type T 1: Schedule for inoculating rabbits with immunogen (HSA).
of vaccination, such as weak antigenicity and short persistence time. Hence, it is extremely necessary to prepare an adjuvant to stimulate the immune system and enhance the immune response to Ags, especially, to pregnancy vaccines. Speci�c transfer factor (STF) is low molecular weight peptides composed of number of amino acid residues and capable of transferring immunity from one cell or individual to another. It is an immunoregulatory and immunosupportive agent with normalizing effect on abnormal immune response. It is prepared by the spleen or peripheral blood lymphocytes of the animals inoculated with a certain pathogen. e essential components of STF are polypeptides and nucleotides. One of the unique features of STF is that it does not have immunogenicity and genus speci�city but the STF prepared by one genus of animals like goat, rabbit, dog, and so forth has the ability of transferring the immunological activity to other genera of animals without causing hypersensitivity. Currently, several STFs have been successfully developed; mainly for herpes simplex virus type 1 (HSV-1) [7], Epstein-Barr virus [8], and Staphylococcus aureus antigens [9]. Also, STFs have been used in therapy of many diseases, for example, lyme, candidiasis, and herpes simplex [10][11][12][13][14]. However, till date no literature has been reported about the preparation of speci�c transfer factor related to pregnancy vaccine.
In context with the previous work on transfer factors [15][16][17], the present study focused on preparation, characterization, and determination of immunological activities of transfer factor speci�c to human sperm antigen. We anticipate that the �ndings from this study would provide valuable information for developing high-efficiency vaccines for birth control in China.

Animals, Instruments and Reagents.
Rabbits and cony pigs were bought from the Experimental Animal Centre of Shandong University, China. All the animals were utilized by the rules related to experimental animals in China. e instruments utilized for the study were ultraspectrophotometer (model number 6405, JENWAY), tissue disintegrator (Fuhua of Jiangsu), Elx-800 microplate-reader (Bio-TEK), and Hitachi 835-50 analyzer. e reagents used included phytohemagglutinin (PHA), methyl thiazolyl tetrazolium (MTT), and D ribose. All the reagents were purchased from Sigma Ltd. Cytokine ELISA kit was purchased from BD Ltd.

Preparation of Immunogen (HSA Solution)
. Sperm samples were washed �ve times with sterile saline and diluted with Roswell Park Memorial Institute (RPMI) 1640 medium. Aer the sperm suspension concentration was adjusted to 4.0 × 10 6 sperm cells/mL, the suspension was completely subjected to comminution by Ultrasonic Cell Crusher maintained at −4 ∘ C. e human sperm antigen (HSA) solution was thus prepared.

Immunization of Rabbits.
For the initial immunization, the rabbits were injected subcutaneously with HSA solution mixed with equivalent volumes of complete Freund's adjuvant (CFA) and incomplete Freund's adjuvant (IFA). e response to immunization with HSA was considered successful if the titer of anti-HSA was 1 : 1280. e inoculation schedule for rabbits is presented in Table 1.

Preparation of HSA-STF.
Ten adult, male rabbits weighing 2-3 kg were bought from Experimental Animal Centre of Jining Medical College, China. e rabbits vaccinated with HSA were successfully slaughtered, and the spleens were collected aer cutting off vessels and fascia. e spleens were washed with sterile saline and mechanically crushed using high-speed tissue disintegrator and, subsequently, comminuted by Ultrasonic Cell Crusher under low temperature. Following this procedure, the spleen suspension thus obtained was frozen at −20 ∘ C and thawed at 37 ∘ C. is procedure was repeated six times. e liquid was dialyzed for 48 hours using dialysis tubing having molecular weight cutoff of 5,000 dalton. e dialysate was collected aer aseptic �ltration and stored in a refrigerator at −20 ∘ C for further examination.

Analysis of General Physicochemical Properties.
In accordance with the standard of transfer factor published in Chinese Pharmacopoeia (2005 Edition), the properties of HSA-STF, including color, pH, absorption peak, content of polypeptides and ribose, sterility test, pyrogen test, and safety test were determined. e content of polypeptide and ribose was detected by Orcinol assay and modi�ed Lowry assay, respectively. Sterility test, pyrogen test, and safety test were carried out using traditional methods.

Analysis of Ultraviolet Spectrum and Amino
Acids. e absorption peaks of HSA-STF solution were scanned in full wavelength using ultraspectrophotometer to �nd out the maximum absorption wavelength, and the ratio of 260 / 280 was recorded. Content of amino acids in HSA-STF was detected using Hitachi 835-50 analyzer.

Determination of Immunological Activity.
Venous blood was drawn from 20 healthy donors, and peripheral blood mononuclear cells (PBMCs) were isolated. e cells were washed twice with RPMI 1640 medium. e percentage of living cells was determined by Taipan blue staining. If the ratio was more than 95%, then, according to the experimental need, various concentrations of cell suspension were prepared with RPMI 1640 medium containing 20% fetal bovine serum (FBS). e speci�c immune activity was analyzed by lymphocyte proliferation test (LPT), leukocyte adhesion inhibition test (LAIT), and by detecting T-cell expansion.

Lymphocyte Proliferation Test (LPT).
Cell suspension (100 L) with concentration 3 × 10 6 /mL was placed into seven culture wells of 96-well plate. In the �rst six wells, 50 L PHA, 50 L HSA with optimal concentration (4.0 × 10 6 sperm cells/mL), and 50 L HSA-STF with gradient concentration (polypeptide concentration of HSA-STF 1 mg/ mL; 0.25 mg/mL; 0.063 mg/mL; 0.016 mg/mL; 0.004 mg/mL; 0.001 mg/mL) were added. e seventh well was treated as control to which only 100 L cultural solution was added. Each well was �lled with RPMI 1640 medium containing 20% FBS, until the volume was 300 L. Subsequently, the plate containing the cell suspensions and test substances were cultured at 37 ∘ C, 5% CO 2 atmosphere for 68 hours. Aer the incubation period, 20 L MTT and 200 L dimethyl sulfoxide (DMSO) were, respectively, added into each well. e �nal solution was used for measuring the optical density (OD) by enzyme-labeled meter using dual wavelength (570 nm and 630 nm). Stimulation index (SI) was calculated using the following formula:

Leukocyte Adhesion Inhibition Test (LAIT).
Cell suspension (100 L) with concentration 5 × 10 6 /mL was placed into the �rst six experimental wells of 96-well plate. en, 50 L of HSA-STF with polypeptide concentration of 0.063 mg/mL was added. Cell suspension (100 L) plus 50 L RPMI 1640 medium containing 10% FBS was added into the successive three wells treated as controls. ese solutions were cultured for 2 hours at 37 ∘ C and 5% CO 2 atmosphere. Aer the incubation period, 50 L HSA with optimal concentration (4.0 × 10 6 sperm cells/mL) and 50 L PHA solution were added to the �rst three experimental wells, and 50 L PHA plus RPMI 1640 medium containing 10% FBS were added to the remaining six wells. e solutions in all the wells were again cultured for 2 hours. Aer decanting the supernatant fraction, 180 L RPMI 1640, 20 L MTT, and 20 L DMSO were added to the remaining sperm cell fraction. e �nal solution was used for measuring the OD.
Leukocyte adhesion inhibition rate (LAIR) was calculated using the following formula:

Detection of T-Cell
Expansion. e procedure used for the preparation of cell culture was same as that for LAIT. e �rst three experimental wells were �lled with 50 L HSA-STF having polypeptide concentration of 0.063 mg/mL. In the middle three wells (control 1) and the subsequent three wells (control 2), 50 L RPMI 1640 containing 10% FBS was added. ese solutions were cultured for 2 hours at 37 ∘ C, 5% CO 2 atmosphere. Aer the incubation period, 50 L HSA was added into the �rst six wells, and 50 L RPMI 1640 containing 10% FBS was added into the remaining three wells, and again cultured for 2 hours. Finally, the supernatant was carefully collected, and the concentration of IL-4, -IFN, and IL-21 was detected using ELISA kit.

e Contents for Transfer Assays Assessed by Skin Tests.
30 BALB/c mice, each weigh about 20 g, were taken as the experimental animals, and they were divided into STF, NTF (normal transfer factor, prepared by the spleen of healthy rabbits), and control group randomly, the mice of the group were given HSA-STF, NTF, and saline water, respectively, both the concentrations of HSA-STF and NTF were same as 0.63 mg/mL, and all the doses were 0.5 mL every day. On the 8th day, the pouring was stopped, and all were injected intracutaneously with HSA 0.5 mL and observed if there were any nodules formed on the skin.

Statistical Analysis.
All data were analyzed with SPSS15.0 soware. Quantitative data was presented as (mean SD). Single elemental data analysis was performed using chisquare test whereas -test was used for comparing paired sample sets. Statistical signi�cance was at 0.0 .  Table 2). In accordance with the standards of Chinese Pharmacopeia (2005 Edition), the results of protein qualitative test, sterility test, pyrogen test, and safety test were all negative. e preparation contained 17 amino acid residues in varying concentrations, out of which glycine (Gly) and glutamic acid (Glu) were the key amino acids present in the highest amount, followed by lysine (Lys) and alanine (Ala). e amounts of threonine (r), methionine (Met), and cystine (Cys) were the lowest (Table 3).

Analysis of Ultraviolet Spectrum of HSA-STF.
Scanned in the range between 200 nm and 450 nm with ultraspectrophotometer, HSA-STF had a maximum absorption peak at 252∼262 nm as depicted in Figure 1. e 260 / 280 was 1.96 ± 0.23.

Lymphocyte Proliferation Test (LPT)
. e proliferation of lymphocytes in the experimental wells containing HSA-STF was signi�cant as compared to the control. HSA-STF could enhance the proliferation of lymphocytes signi�cantly. Moreover, the effect was dependent on the concentration of HSA-STF. e stimulation index (SI) for lymphocyte proliferation test was 1.84 when the polypeptide concentration was 0.063 mg/mL (Figure 2).

Leukocyte Adhesion Inhibition Test (LAIT).
Aer incubation with HSA-STF, the LAIR of the lymphocytes in the experimental wells containing HSA plus PHA was 37.7%, which was signi�cantly higher than other wells containing either HSA or PHA ( 0.0 ) (Figure 3). is �nding suggested that HSA-STF could inhibit leukocyte adhesion, and the effect of LAI was dependent on speci�c antigen.

Expansion of T-Cell Subpopulation.
Compared with the control-1 group, there was no signi�cant difference ( 0.0 ) in IL-4 content for the experimental group, but there was a signi�cant difference ( 0.0 ) between the two groups for the levels of -IFN and IL-21. Similar results were observed for the experimental group and control-2 group (Table 4).

e Contents for Transfer Assays Assessed by Skin Tests.
In the STF group, the skin was in�amed at the site of injection, and there were marked nodules formed, while there was no nodule observed in the mice in both NTF and control groups.

Discussion
e development of vaccines based on sperm antigen is an exciting proposition and may represent a promising alternative to the currently available contraceptive methods [4]. In this study, we prepared and characterized HSA-STF successfully, and the physicochemical properties (including the color, absorption peak, the content of polypeptide, and ribose) were determined. e immunological activity of HSA-STF was also determined. e HSA-STF acted in accordance with the standard of transfer factor published in Chinese Pharmacopeia (2005 Edition). ere were con�icting reports for the number of amino acids present in HSA-STF. Some reported 17 while others reported 18 amino acids [18,19]. Moreover, the content of each amino acid varied from study to study. On the contrary, a study by Kirkpatrick stated that multiple combinatorial patterns between these amino acids create a vast number of different transfer factor molecules. Such large number of molecules would then satisfy the notion that STF molecule was necessary to transfer immunity to each and every speci�c antigenic determinant [20].
Lymphocyte proliferation test is used to detect the nonspeci�c characteristic of STF. e results showed that HSA-STF stimulated the proliferation of lymphocytes, which resulted in increase in the concentration of polypeptide as increased in SI. When the concentration of polypeptide was more than 0.063 mg/mL, the SI decreased. On the contrary, this phenomenon showed, that aer stimulation by HSA-STF, the increase or decrease in lymphocytes was dependent upon the concentration of polypeptide. ese results were in line with another study by Lawrence [21]. A study by Xiao et al. 2004 [22] reported that the optical concentration of TF speci�c to tuberculosis was 0.50 mg/mL. is is probably due to the differences in HSA-STF components, which decide its stimulation activities. According to this characteristic, a study by Kirkpatrick et al. 1985 [23] was focused to prepare STF by immunizing mice with arti�cial amino acids. is resulted in successful transfer of the delayed type hypersensitivity (DTH) speci�c to the peptide in the unimmunized group.
In the results of LAIT, the LAIR of the group containing HSA, HSA-STF, and PHA was signi�cantly higher than the other groups. is proved that, in the presence of HSA, transfer factor speci�c to HSA could signi�cantly enhance the immunological activity of the lymphocyte. Moreover, it also raised the capability of speci�c response to differential immunogen. us, the data of this study demonstrated that HSA-STF possessed antigen speci�c activity, which depended on the antigen and the capacity of combining with the speci�c antigens [24].
Speci�c transfer factor plays an important role in regulating the immune response. A study by Pineda et al., 2005, [10] determined the role of STF in regulating the immune response using the mouse model of pleomorphism malignancy glioma and revealed that STF increases the number of CD2, CD4, CD8, and NK cells; it enhances the apoptosis of number of tumor cells and the expression of 1 subpopulation in tumor tissue. Another study by Fujisawa et al. 1991 reported that, through a possible mechanism of STF, it could affect peripheral blood mononuclear cells, raise the production of leukocyte movement inhibition factor, promote the quantity of -IFN, IL-1, CD4, and CD3, and also could stimulate the expression of IL-2R [25]. e �ndings from a study by Fujisawa et al. 1991 [25] showed that the contents of IL-4, -IFN, and IL-21 were detected as the key products of T helper 1 cells (1). It also revealed that -IFN concentration was signi�cantly higher than the lymphocytes without stimulation by HSA-STF. ese results were in line with another study by Kirkpatrick et al. 1970 [26]; however, the level of IL-4 was not affected by HSA-STF. is indicated that TF speci�c to HSA had no effect on T helper 2 cells (2). ese results demonstrate that HSA-STF can increase the ratio of 1/2 by increasing the expression of 1, and by relatively decreasing the 2 clonal activity. e results of this study also demonstrate that HSA-STF could enhance cellular immunity while decreasing the humoral immunological response. Further, this study revealed that the concentration of IL-21 was the same as that of -IFN, but it was signi�cantly higher than the lymphocytes without stimulation by HSA-STF. In line with our results [27,28] Batten et al. (2010) and Eto et al. (2011) reported that IL-21 is a key cytokine secreted by T follicular helper cells (T), it promotes the activity of T and also mediates the secretion function of B cells. On the other hand, cytokines have the ability to directly affect B cells through combining IL-21R expressed on the B-cell membrane, and, thus, this helps to increase the levels of immunoglobulin secreted, which in turn enhances the humoral immunity. us, the results from the current study demonstrate that HSA-STF plays an important role in transferring cellular immunity to the receiver, and it also has the ability to mediate humoral immunological response.

Conclusion
In conclusion, we were successful in preparing the HSA-STF vaccine. Its physicochemical properties were evaluated, and these were in accordance with the Chinese standard of STF; HSA-STF had immunological activity which could transfer the immune response speci�c to HAS, and thus it could