Rodent population control through contraception requires species-specific oral contraceptive vaccines. Therefore, in this study, we produced putative mouse-specific contraceptive peptides, mZP2 (from oocyte) and mIzumo1 (from sperm), in plants using Agrobacterium-mediated transient expression. Peptides were produced separately in Nicotiana benthamiana using constructs encoding antigens containing three copies of each peptide. We also determined the immunogenicity and contraceptive effects of the plant-produced antigens in female BALB/c mice. Mice immunized subcutaneously with a relatively low amount of antigen (5 µg/dose of each peptide in a mixture) showed systemic immune responses against mZP2-3 and mIzumo1-3 antigens. Moreover, the mean litter size of mice treated with the plant-produced antigens was reduced by 39% compared to that of the control mice. Notably, there was a significant negative correlation between the number of pups born and individual antibody levels against both antigens. Immunofluorescence assays demonstrated the binding of induced antibodies to the oocytes of BALB/c and wild-type mice in vivo and in vitro, respectively. Our study demonstrate the feasibility of producing small contraceptive peptides in plants that can be further used to develop oral contraceptive vaccines against mouse populations.

The cyclical proliferation of the wild fossorial rodent Arvicola terrestris scherman (ATS) is critical in mid-mountain ecosystems of several European countries. Our goal is to develop an immunocontraceptive vaccine to control their fertility, as a sustainable alternative to chemical poisons currently used. Indeed, these chemicals cause the death of ATS predators and animals sharing their ecosystem, and current laws progressively limit their use, making the development of a targeted vaccination strategy an interesting and efficient alternative. In order to identify species-specific sperm antigens, male and female ATS received subcutaneous injections of whole ATS spermatozoa to elicit an immune response. The analysis of the immune sera led to the identification of 120 immunogenic proteins of sperm cells. Of these, 15 were strictly sperm-specific and located in different regions of the male gamete. Some of these antigens are proteins involved in molecular events essential to the reproductive process, such as sperm-egg interaction, acrosomal reaction, or sperm motility. This approach not only identified a panel of immunogenic proteins from ATS sperm cells, but also demonstrated that some of these proteins trigger an immune response in both male and female ATS. These spermatic antigens are good candidates for the development of a contraceptive vaccine.

BACKGROUND: The management of stray dog population has been of utmost importance due to their overpopulation, increase in dog bites incidence, and rabies. Contraceptive vaccines, a non-surgical alternative to spaying and neutering are viewed as a valuable option for the management of dog population. In this study, the contraceptive potential of a recombinant fusion protein containing the three genes GnRH, GnRH receptor, and ZP3 was explored.
RESULTS: The gene fragment encoding GnRH, GnRHR, and ZP3 along with the antigenic epitopes of canine distemper virus and tetanus toxoid was assembled, synthesized, and cloned into pET28a expression vector. The resulting construct GVAC08 was successfully transformed into BL21DE3 strain of E. coli and confirmed by colony PCR. The recombinant GVAC08 protein was expressed and purified using Ni-NTA and was confirmed to be a 50-KDa protein by SDS PAGE and Western blot. Mice were immunized with the GVAC08 protein using Freund\'s complete adjuvant followed by a booster using Freund\'s incomplete adjuvant. This induced a high antibody titer against GnRH, GnRH receptor, and ZP3 which was determined by ELISA.
CONCLUSIONS: Mating studies showed that the GVAC08 recombinant protein was able to reduce the litter size in immunized mice showing improved efficacy. However, the vaccine candidate with further improvements will be a viable contraceptive vaccine.

Contraceptive vaccine (CV) is a valuable, non-invasive, and alternative method for purposeful contraception. Sperm antigens are useful targets for producing CVs due to their specialized expression in sperm. In this study, a recombinant protein containing three main sperm epitopes (IZUMO1, SACA3, and PH-20) was designed and evaluated as CV to control fertility in male mice. The chimeric recombinant protein was expressed and purified in E. coli. Male mice were immunized by 100 μg purified protein and sera were collected to assess IgG antibodies. Evaluating the reproductive performance, immunized male mice mated with normal-fertile female mice and mating rate and the number of newborns was studied. Immunized mice were sacrificed and necropsy and histopathology studies were conducted. The results revealed that the designed chimeric protein stimulated the immune system of the mice effectively. The level of IgG antibody was significantly higher in vaccinated mouse rather than control mouse. Eighty percent of the vaccinated mice became infertile and in the remaining ones, the number of children decreased to 4-6 offspring instead of 10-12 in normal mice. Histopathological studies showed that no organs including heart, brain, lung, liver, kidney and intestine were damaged. However, Normal spermatogenesis has been disrupted and necrotic spermatogonia cells were reported in Seminiferous tubules. We concluded that the designed chimeric protein containing IZUMO1, SACA3, and PH-20 epitopes can stimulate the immune system and cause male contraception without any side effects.

The functional competence of leukemia inhibitory factor (LIF), as immunocontraceptive vaccine in mice, was investigated. Balb/c mice were divided into two groups of vaccinated and controls. The recombinant human LIF (rhLIF) protein and phosphate buffer saline was emulsified with Freund\'s adjuvant and injected into vaccinated and control groups, respectively. Theinhibition of implantation was evaluated in mice uterine. The concentration of secreted interferon-γ (IFN-γ) and interleukin (IL)-4 were measured in cultured splenocyte of mice stimulated by rhLIF. The expressions of immune responsive gene 1 (IRG-1), cochlin (COCH), amphiregulin(Ar), and heparin-binding EGF-like growth factor (HB-EGF) genes were determined. Mice were assessed for inhibition of fertility after delivery, reversibility of immune response against rhLIF, and survival rate. Active immunization of mice with rhLIF resulted in reduction of the implantation and fertility rate up to 80.49% and 75%, respectively. All mice produced a high titer of anti-rhLIF antibodies in serums and vaginal fluids washes after 16 weeks; however, these antibodies were cleared from vaginal fluid washes after six months. A significant down-regulation in mRNA levels of IRG-1, Ar and HB-EGF was observed in vaccinated group compared to controls; however, no significant change in the expression profile of cochlin gene was detected. The results showed that rhLIF prevented pregnancy in a high percentage of female mice. Although the immunization of female Balb/c mice with rhLIF inhibited fertility and expression of genes associated with this molecule, further studies are needed to support this protein as a suitable candidate for contraceptive vaccine in mammals.

Human leukemia inhibitory factor (hLIF) is a cytokine of interleukin-6 family. This study aimed to evaluate the recombinant production rate of active hLIF by different vector-host systems under various conditions. Moreover, a rabbit polyclonal antibody (pAb) against recombinant hLIF (rhLIF) was produced and its anti-fertility effects were explored in Balb/c mice. Four different constructs including pET22b/hLIF, pET28b/hLIF, pET32b/hLIF and pColdI/hLIF were designed and transformed into BL21-(DE3), Rosetta-(DE3), Origami-(DE3) and Shuffle T7-(DE3) host cells. The expression level and proliferative effect of rhLIF were measured by SDS-PAGE and MTT assays, respectively. Rabbit pAb to rhLIF was produced and characterized using enzyme-linked immunosorbent assay and western blot techniques. The Balb/c mice were divided into two intervention and control groups. Then, they were intraperitoneally injected by purified rabbit anti-rhLIF and non-immunized rabbit pAb, respectively. After sacrifice on day 7, the number of implantation sites was counted. The rhLIF was successfully expressed by pET32b/hLIF and pColdI/hLIF vectors in all hosts with no significant difference in the rate of their expression. The rhLIF was purified and checked for activity. The results showed that it is functionally active and the produced anti-rhLIF pAb could specifically bind to commercial rhLIF. Passive immunization results showed that anti-rhLIF antibody completely inhibited fertility in all injected Balb/c mice compared to controls. Although previous studies showed expression of rhLIF using various methods, using different vector-host systems ensures us of successful biological active expression of it. The pAb against rhLIF could be a powerful tool for inducing in vivo infertility.

Requirement of multiple injections of contraceptive vaccines to achieve infertility is one of the important impediments for their application. In the present study, attempts have been made to reduce the number of injections of contraceptive vaccine.
Fusion protein encompassing C-terminus fragment of sperm protein Sp17 (aa residues 76-126) and two copies of gonadotropin-releasing hormone along with T-cell epitopes and dilysine linkers (abbreviated as Sp17C -GnRH2 ) was expressed in Escherichia coli. Its immunogenicity and contraceptive efficacy have been evaluated in female FVB/J mice using different adjuvants and delivery platforms.
Immunization of female mice with recombinant Sp17C -GnRH2 (25 μg/injection/mouse) emulsified with squalene-arlacel A following two injections schedule led to failure of 88.8% immunized animals to conceive, which was not significantly different from mice immunized with same protein along with alum following three injections schedule. To make single-dose vaccine, poly d,l-lactic acid-based microparticles (PLA-MPs) entrapping Sp17C -GnRH2 were prepared. Immunization of female mice with a combination of soluble Sp17C -GnRH2 (12.5 μg/injection/mouse) along with Sp17C -GnRH2 entrapped in PLA-MPs (12.5 μg/injection/mouse) in alum showed higher antibody titres and contraceptive efficacy as compared to mice immunized with Sp17C -GnRH2 entrapped in PLA-MPs alone in alum. Immunization with recombinant Sp17C -GnRH2 led to long-term infertility as second mating (150 days after immunization) of various groups of immunized mice showed similar infertility as observed during first mating.
Single-dose immunization with PLA-MPs entrapping Sp17C -GnRH2 along with soluble recombinant protein in alum generated long-lasting infertility in female mice.

BACKGROUND: Stray dogs are the reservoirs and carriers of rabies and are definitive hosts of echinococcosis. To control the overpopulation of stray dogs, zona pellucida 3 (ZP3), a primary receptor for sperm, is a potential antigen for developing contraceptive vaccines. To enhance the immune responses and contraceptive effects of canine ZP3 (cZP3), dog gonadotropin-releasing hormone (GnRH) and a T cell epitope of chicken ovalbumin (OVA) were selected to construct two fusion proteins with cZP3, ovalbumin-GnRH-ZP3 (OGZ) and ovalbumin-ZP3 (OZ), and their contraceptive effects were evaluated in mice.
METHODS: The synthesized DNA sequences of OGZ and OZ were cloned into plasmid pET-28a respectively. The fusion proteins OGZ and OZ were identified by SDS-PAGE and Western blot. Mice were immunized with OGZ, OZ and cZP3, and the infertility rates were monitored. Mice immunized with mouse ZP3 (mZP3) or adjuvant alone were used as positive control and negative control, respectively. cZP3- and GnRH-specific antibodies (Abs) were detected by ELISA. The bindings of the Abs to oocytes were detected by indirect immunofluorescence assay. The paraffin sections of mice ovaries were observed under microscope for analyzing pathological characteristics.
RESULTS: SDS-PAGE and Western blot analyses showed that the two fusion proteins OGZ and OZ were correctly expressed. ELISA results showed that OGZ vaccine induced both cZP3- and GnRH-specific Abs, and OZ vaccine induced cZP3-specific Ab, which lasted for up to 168 days. The levels of follicle stimulating hormone (FSH) and estradiol (E2) in sera were significantly decreased in OGZ immunized mice. Indirect immunofluorescence results showed that Abs induced by cZP3 and mZP3 could bind to the mouse ZP and dog ZP each other. Compared with the adjuvant group, all vaccine immunized groups significantly decreased the fertility rate and mean litter size. Interestingly, the fertility rate in OGZ-immunized group is the lowest, and only 1 mouse out of 10 mice is fertile. Histological analysis of murine ovarian sections indicated that most of the infertile mice in the immunized groups lacked mature follicles as well as accompanied by inflammatory infiltration. Meanwhile, immunization with OGZ decreased the number of corpora lutea in the infertile mice.
CONCLUSIONS: The fusion protein OGZ resulted in the lowest fertility rate and the least mean litter size in the immunized mice. OGZ might be a promising antigen for developing a new contraceptive vaccine for stray dog controlling.

OBJECTIVE: To overcome availability of the purified native zona pellucida (ZP) glycoproteins for immunocontraception, porcine ZP3, and ZP4 were expressed in E. coli.
METHODS: Purified recombinant proteins were characterized by SDS-PAGE and Western blot, and immunogenicity and contraceptive efficacy determined in FvB/J female mice.
RESULTS: Purified ZP3, ZP3 with promiscuous T-cell epitope of tetanus toxoid, ZP4 and ZP4 incorporating promiscuous T-cell epitope of bovine RNase revealed ~44-, ~49-, ~53-, and ~55-kDa bands by SDS-PAGE and Western blot, respectively. Immunization of female mice with recombinant proteins elicited high antibody titers as well as T-cell responses. Immune sera recognized mouse oocyte ZP and also inhibited in vitro fertilization. Immunized mice showed significant decrease in fertility. Recombinant proteins were able to recall memory antibody response in female mice primed with porcine native ZP.
CONCLUSIONS: Availability of recombinant porcine proteins will be useful in the development of contraceptive vaccine.