Reproductive component vaccine developments for contraceptive and non-contraceptive uses

Active immunization with recombinant GnRH6-CRM197 inhibits reproductive function of male rats

Gonadotropin-releasing hormone (GnRH) vaccines have been successfully used for the inhibition of gonadal development and function, but current GnRH-based vaccines often present variability in the response. Cross-reactive material 197 (CRM197) has been used as carrier molecules to enhance an immune response to associated antigens. So, the synthetic mammalian tandem-repeated GnRH hexamer (GnRH6) gene was integrated into the expression plasmid pET-21a. Recombinant GnRH6-CRM197 protein was subsequently overexpressed in Escherichia coli strain BL21 and purified through Nickel column affinity chromatography and the antigenicity and biological effects of GnRH6-CRM197 were evaluated in rats. Sixteen 4-month-old adult male rats were randomly divided into two groups: the GnRH6-CRM197 group (n = 8) and the control group (n = 8). The GnRH6-CRM197 group rats were subcutaneously immunized with 100 μg of GnRH6-CRM197, administered thrice at 2-week intervals with GnRH6-CRM197.The control group received only a white oil adjuvant. Following the initial immunization, the weights of animals were recorded, and blood samples were collected from the orbital sinus at 4, 4.5, 5, 5.5, 6, 6.5, and 7 months. Serum antibody titers and testosterone concentrations were quantified using ELISA and CLIA, respectively. Additionally, testicular tissues were collected for morphological examination. The results revealed a significant increase in serum GnRH antibody titers (p < 0.05), but a significant decrease in serum testosterone concentrations (p < 0.05), and the weight, length, width, and girth of the testis, and the number of spermatogonia cells, spermatocytes, and sperm cells in the immunized rats. Furthermore, seminiferous tubules revealed significant atrophy and no sperm were observed in the immunized animals. Thus, GnRH6-CRM197 may be an effective antigen and a potential immunocastration vaccine.

Strategies for successful designing of immunocontraceptive vaccines and recent updates in vaccine development against sexually transmitted infections - A Review

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Effect of active immunization using a novel GnRH vaccine on reproductive function in rats

To investigate the effect of gonadotropin-releasing hormone 2-multiple antigen peptide (GnRH2-MAP) on reproductive function. In our study, 20-day-old male rats (n = 90) were randomly allocated to one of three treatment groups: GnRH2-MAP immunization, GnRH2 immunization, and non-immunized control groups. The immunized animals were administered three doses of GnRH2-MAP or GnRH2 vaccines from 0 to 6 weeks at 2-week intervals. The control group only received oil adjuvant. Blood and right testis samples were collected, and the left testis was weighed and its volume was measured at 0, 2, 4, 6, 8, 10 and 12 weeks after the first immunization. The serum antibody titer and testosterone concentration were determined by ELISA, and the right testis samples were collected for histological analysis. The results revealed that the serum of vaccinated rats elicited a significantly higher antibody titer and a lower T concentration compared with the control group two weeks after the first immunization (P < 0.05), but the highest antibody titer and lowest T concentration were found in animals treated with GnRH2-MAP (P < 0.05). The second immunization resulted in a significant decrease in testicular weight and volume (P < 0.05) in both immunized groups compared to the control, but these values were significantly lower in the GnRH2-MAP group than in the GnRH2 group. Furthermore, seminiferous tubules revealed more significant atrophy in the GnRH2-MAP group than in the GnRH2 group, and no sperm were observed in rats of the GnRH2-MAP group. Thus, GnRH2-MAP may be an effective antigen and a potential immunocastration vaccine with higher effectiveness.

Discovery of human posterior head 20 (hPH20) and homo sapiens sperm acrosome associated 1 (hSPACA1) immunocontraceptive epitopes and their effects on fertility in male and female mice

The key goals of immunocontraception research are to obtain full contraceptive effects using vaccines administered to both males and females. Current research concerning human anti-sperm contraceptive vaccines is focused on delineating infertility-related epitopes to avoid autoimmune disease. We constructed phage-display peptide libraries to select epitope peptides derived from human posterior head 20 (hPH20) and homo sapiens sperm acrosome associated 1 (hSPACA1) using sera collected from infertile women harbouring anti-sperm antibodies. Following five rounds of selection, positive colonies were reconfirmed for reactivity with the immunoinfertile sera. We biopanned and analysed the chemical properties of four epitope peptides, named P82, Sa6, Sa37 and Sa76. Synthetic peptides were made and coupled to either bovine serum albumin (BSA) or ovalbumin. We used the BSA-conjugated peptides to immunise BALB/c mice and examined the effects on fertility in female and male mice. The synthetic peptides generated a sperm-specific antibody response in female and male mice that caused a contraceptive state. The immunocontraceptive effect was reversible and, with the disappearance of peptide-specific antibodies, there was complete restoration of fertility. Vaccinations using P82, Sa6 and Sa76 peptides resulted in no apparent side effects. Thus, it is efficient and practical to identify epitope peptide candidates by phage display. These peptides may find clinical application in the specific diagnosis and treatment of male and female infertility and contraceptive vaccine development.

Construction of a catsper1 DNA vaccine and its antifertility effect on male mice

Cation channel of sperm 1 (CATSPER1) is a unique sperm cation channel protein, and essential for sperm function and male fertility. CATSPER1 exclusively expresses in meiotic and postmeiotic spermatogenic cells, thus belongs to the spermatogenesis-specific antigen that escape central tolerance. We have previously demonstrated the immunocontraceptive potential of its transmembrane domains and pore region, and reported the antifertility effects of its B-cell epitopes on male mice. Aiming to develop DNA vaccine targeting CATSPER1 for male contraception, here the whole open reading frame of mouse Catsper1 was cloned into the plasmid pEGFP-N1 to obtain a DNA vaccine pEGFP-N1-Catsper1. The vaccine was confirmed to be transcribed and translated in mouse N2a cell in vitro and mouse muscle tissue in vivo. Intramuscular injection with the vaccine on male mice induced specific immune reaction and caused significant inhibition on sperm hyperactivated motility and progressive motility (P<0.001 for both), and consequently reduced male fertility. The fertility rate of experimental group was 40.9%, which was significant lower (P=0.012) than control group (81.8%). No significant change in mating behavior, sperm production and histology of testis/epididymis was observed. Given that Catsper1 exhibits a high degree of homology among different species, Catsper1 DNA vaccine might be a good strategy for developing an immunocontraceptive vaccine for human and animal use.

The preparation and application of N-terminal 57 amino acid protein of the follicle-stimulating hormone receptor as a candidate male contraceptive vaccine

Follicle-stimulating hormone receptor (FSHR), which is expressed only on Sertoli cells and plays a key role in spermatogenesis, has been paid attention for its potential in male contraception vaccine research and development. This study introduces a method for the preparation and purification of human FSHR 57-amino acid protein (FSHR-57aa) as well as determination of its immunogenicity and antifertility effect. A recombinant pET-28a(+)-FSHR-57aa plasmid was constructed and expressed in Escherichia coli strain BL21 Star TM (DE3) and the FSHR-57aa protein was separated and collected by cutting the gel and recovering activity by efficient refolding dialysis. The protein was identified by Western blot and high-performance liquid chromatography analysis with a band of nearly 7 kDa and a purity of 97.4%. Male monkeys were immunized with rhFSHR-57aa protein and a gradual rising of specific serum IgG antibody was found which reached a plateau on day 112 (16 weeks) after the first immunization. After mating of one male with three female monkeys, the pregnancy rate of those mated with males immunized against FSHR-57aa was significantly decreased while the serum hormone levels of testosterone and estradiol were not disturbed in the control or the FSHR-57aa groups. By evaluating pathological changes in testicular histology, we found that the blood-testis barrier remained intact, in spite of some small damage to Sertoli cells. In conclusion, our study demonstrates that the rhFSHR-57aa protein might be a feasible male contraceptive which could affect sperm production without disturbing hormone levels.

Assessment of the antigen-specific antibody response induced by mucosal administration of a GnRH conjugate entrapped in lipid nanoparticles

Vaccines administered parenterally have been developed against gonadotrophin-releasing hormone (GnRH) for anti-fertility and anti-cancer purposes. The aim of this study was to demonstrate whether mucosal delivery using GnRH immunogens entrapped in lipid nanoparticles (LNP) could induce anti-GnRH antibody titers. Immunogens consisting of KLH (keyhole limpet hemocyanin) conjugated to either GnRH-I or GnRH-III analogues were entrapped in LNP. Loaded non-ionic surfactant vesicles (NISVs) were administered subcutaneously, while nasal delivery was achieved using NISV in xanthan gum and oral delivery using NISV containing deoxycholate (bilosomes). NISV and bilosomes had similar properties: they were spherical, in the nanometre size range, with a slightly negative zeta potential and surface properties that changed with protein loading and inclusion of xanthan gum. Following immunization in female BALB/c mice, systemic antibody responses were similar for both GnRH-I and GnRH-III immunization. Only nasal delivery proved to be successful in terms of producing systemic and mucosal antibodies.

FROM THE CLINICAL EDITOR

The main research question addressed in this study was whether mucosal delivery using gonadotrophin-releasing hormone immunogens entrapped in lipid nanoparticles could induce anti-GnRH antibody titers. Only nasal delivery proved to be successful in terms of producing systemic and mucosal antibodies with this approach.