Immunization of mice against a synthetic N-terminal extracellular domain gonadotropin-releasing hormone receptor peptide: evidence for a direct uterine effect

Mother-fetus immunogenetic dialogue as a factor of progeny immune system development

Despite the advances in medicine, about 4 million children under the age of 6 months die annually around the world due to infection, which is 450 deaths per hour (UNISEF, 2009). The degree of development of the immune system of children born in time is determined by many factors, including the immunogenetic similarity or difference of mother and fetus organisms, which, in turn, is due to the genotypes of mating pairs, as well as the selection of surrogate mothers duringin vitrofertilization. From our review of the literature, it follows that immunogenetic interactions of mother and fetus organisms, which occur at all stages of pre- and postnatal development, have a signifcant effect on the resistance of offspring to infections and allergens. Before implantation, the mother’s immune responses are formed under the influence of semen fluid antigens, leukocytes and cytokines, as well as under the influence of the genes of the major histocompatibility complex, which are expressed in embryos at the stage of two cells. After implantation, transplacental transfer of immunoglobulins and immunocompetent cells becomes of immunomodulating importance. It is important to emphasize that, although substances with a high molecular weight usually do not pass through the placenta, this rule does not apply to immunoglobulin G (IgG), which, with a molecular weight of about 160 kDa, overcomes the transplacental barrier due to binding to the fetal Fc receptor. The level of IgG in newborns usually correlates with the level of maternal antibodies. During the period of natural feeding, the immune protection of newborns is provided by the mechanisms of innate immunity and the factors of humoral immunity of mothers. It has been shown that immunoglobulins from the milk of many animal species are transferred through the neonatal intestinal epithelium to the blood. Since breast milk contains large amounts of various immunoactive components, including proteins, cytokines, hormones, immunoglobulins, exosomes containing micro-RNA, and viable immune cells, the immunomodulating effects of breast milk persist even after elimination of maternal immunoglobulins from the blood of the offspring, up to maturation. Analysis of a large body of experimental data shows that the study of mechanisms of “motherfetus” and “mother-newborn” interactions are the basis of a knowledge base needed to fnd means of life-long directed modulation of the descendants’ immune status.

Growth inhibition of tumor cells in vitro by using monoclonal antibodies against gonadotropin-releasing hormone receptor

As the continuation of a previous study, synthetic peptides corresponding to the extracellular domains of human gonadotropin-releasing hormone (GnRH) receptor were used to generate additional monoclonal antibodies which were further characterized biochemically and immunologically. Among those identified to recognize GnRH receptor, monoclonal antibodies designated as GHR-103, GHR-106 and GHR-114 were found to exhibit high affinity (Kd < or = 1 x 10(-8) M) and specificity to GnRH receptor as judged by the whole cell binding immunoassay and Western blot assay. Both anti-GnRH receptor monoclonal antibodies and GnRH were shown to compete for the same binding site of GnRH receptor on the surface of cultured cancer cells. Growth inhibitions of cancer cells cultured in vitro were demonstrated by cellular apoptosis experiments (TUNEL and MTT assays) under different conditions of treatment with GHR-106 monoclonal antibody or GnRH analogs. It was generally observed that both GnRH I and GHR-106 effectively induce the apoptosis of cultured cancer cells as determined by TUNEL and MTT assays. Consistently, suppressions of gene expressions at mRNA levels were demonstrated with several ribosomal proteins (P0, P1, P2 and L37), when cancer cells were incubated with GnRH or GHR-106. The widespread expressions of GnRH receptor in almost all of the studied human cancer cell lines were also demonstrated by RT-PCR and Western blot assay, as well as indirect immunofluorescence assay with either of these monoclonal antibodies as the primary antibody. In view of the longer half life of antibodies as compared to that of GnRH or its analogs, anti-GnRH receptor monoclonal antibodies in humanized forms could function as GnRH analogs and serve as an ideal candidate of anti-cancer drugs for therapeutic treatments of various cancers in humans as well as for fertility regulations.

Precycle administration of GnRH antagonist and microdose HCG decreases clinical pregnancy rates without affecting embryo quality and blastulation

The outcome of a novel protocol utilizing precycle gonadotrophin-releasing hormone (GnRH) antagonist administration and LH activity support with microdose recombinant human chorionic gonadotrophin (HCG) was compared to GnRH agonist long protocol used in patients undergoing their first ICSI (n=707) or IVF (n=571) cycles, which had resulted in one or two blastocyst transfers. In GnRH antagonist cycles, cetrorelix acetate (3 mg) was administered s.c. 4 days before FSH stimulation and a repeat dose was given when the lead follicular diameter was 13-14 mm. LH support was provided by recombinant HCG (2.5 microg). Embryo progression and blastulation were evaluated using embryo progression indices and blastocyst quality scores. The tested protocol demonstrated reduced implantation and clinical pregnancy rates as compared with GnRH agonist long protocol, although the embryo progression and blastulation parameters and blastocyst quality were comparable among the groups. Logistic regression models further supported the significant negative impact of GnRH antagonist/microdose HCG protocol on clinical pregnancy rates in both ICSI and IVF patients. Assisted reproduction cycles with fresh blastocyst transfers utilizing precycle GnRH antagonist administration and microdose HCG support resulted in lower implantation and clinical pregnancy rates as compared with GnRH agonist cycles, although the embryo progression and blastulation parameters were comparable.

Effect of active and passive immunization of male and female rats with a recombinantly expressed bonnet monkey pituitary GnRH receptor fragment

Gonadotropin releasing hormone (GnRH) exerts its action by binding to the specific receptor which belongs to the family of G-protein coupled receptors that are characterized by the presence of seven transmembrane domains linked together by extracellular and intracellular loops. A fragment of the pituitary receptor of the bonnet monkey (Macaca radiata) corresponding to amino acids 164-266 was cloned and expressed in Escherichia coli. This was used to raise antibodies to the receptor in rabbits. Active and passive immunization studies in both male and female rats were carried out using, both the 'overexpressed' fragment, as well as antibodies raised to the receptor fragment. Both active, as well as passive immunization in the male rats brought about an agonistic effect in terms of increase in serum LH level, as well as increase in serum and testicular testosterone levels. However, in the female rats, active immunization with the receptor fragment did not have any effect on the gonadal steroid levels but had a selective effect on the uterine morphology.

The role of gonadotropin-releasing hormone in murine preimplantation embryonic development

Previous studies have established the presence of an extrahypothalamic GnRH in a variety of tissues. GnRH receptor is known to be present in the placenta, which produces and secretes the decapeptide from the very early stages of placentation. We hypothesized that GnRH may play a role in the preimplantation development of embryos. To examine this hypothesis, we assessed GnRH and GnRH receptor messenger RNA (mRNA; RT-PCR) and protein expression (Immunohistochemistry) in preimplantation murine embryos at various developmental stages. Furthermore, preimplantation murine embryos were cultured with GnRH agonist and antagonist in vitro to assess the influence of GnRH analogs on embryo development. GnRH is expressed in the developing mouse embryo from morula to hatching blastocyst stages at the mRNA and protein levels. GnRH receptor mRNA is also present in the developing embryos studied. Preimplantation embryonic development was significantly enhanced by incubation with increasing concentrations of GnRH agonist and is significantly decreased by GnRH antagonist compared with that in the control group. Moreover, GnRH antagonist (5 and 10 microM) was able to completely block embryo development. The deleterious effect of GnRH antagonist on embryo development was reversed by increasing concentrations of the agonist, as determined by the number of embryos reaching the blastocyst stage.

Immunolocalization of a gonadotropin-releasing hormone receptor site in murine endometrium that mediates apoptosis

Circumstantial evidence from a previous study indicated that antibodies generated against a synthetic N-terminal extracellular domain mouse pituitary gonadotropin-releasing hormone (GnRH) receptor peptide acted directly on the murine uterus affecting endometrial regression. Affinity-purified polyclonal sheep antibodies were used to assess tissue-specificity of antibody reactions in diestrous mice. Antibody binding was localized by immunofluorescence staining to anterior pituitary gland and endometrium. Ovary, brain, liver, kidneys, heart, lungs, spleen, gastrointestinal tract, adrenal glands, thymus, thyroid gland, muscle, and adipose were unreactive. Fragmented deoxyribonucleic acid, a marker of programmed cell death/apoptosis, was detected by digoxigenin labeling-immunoperoxidase in endometrial (but not pituitary) glands of animals injected with antipeptide antibodies or native ligand. It appears that luteal phase endometrium of mice expresses a GnRH receptor moiety that is coupled to a cell death (endonuclease) transduction pathway.

Immunoregulation of mammalian fertility

Fertility management is a global issue of agricultural, medical, economic, and social consequence. Although many methods have been devised to both inhibit and assist reproduction, more acceptable alternatives are needed. Regulation by immune intervention is a promising technology as applied to livestock, pets, wildlife, and human beings. Outcome is dictated by site within the reproductive axis that is targeted. Fertility is suppressed by immunization against gonadotropin-releasing hormone, gonadotropins, prostaglandin F2 alpha, oxytocin, gonadotropin receptors, and gamete/embryonic antigens. It also is possible to lyse gonadal cells with ligand-antibody hybrid molecules. Ovulation rates are enhanced by vaccination with inhibin. Antibodies to sex steroid hormones have yielded mixed results. Perhaps recombinant viral vectors can be used to deliver reproductive immunogens. A new and simple technique to generate sustained autoimmune reactions to hormones and cellular antigens entails direct gene transfer into somatic cells. Evolving advances in reproductive immunology and biotechnology should furnish us with novel nonsurgical contraceptives and profertility agents that can be efficiently and safely implemented.