Anti-GnRH antibodies can induce castrate levels of testosterone in patients with advanced prostate cancer

Influence of Humoral Response Against GnRH, Generated by Immunization with a Therapeutic Vaccine Candidate on the Evolution of Patients with Castration-Sensitive Prostate Adenocarcinoma

BACKGROUND AND AIMS

A gonadotropin-releasing hormone (GnRH)-based therapeutic vaccine candidate against hormone-sensitive prostate cancer has demonstrated its safety and signs of efficacy in phase I/II trials. In this study, we characterized the isotype/subclass profiles of the anti-GnRH humoral response generated by the vaccination and analyzed its association with patients' clinical outcomes.

METHODS

The immunoglobulin isotypes and IgG subclasses of the antibody responses of 34 patients included in a randomized, open, prospective phase I/II clinical trial were characterized. Every patient included in the study had a diagnosis of locally advanced prostate adenocarcinoma at stages 3 and 4 and received immunization with the vaccine candidate. Additionally, serum testosterone and prostate specific antigen (PSA) concentrations, serving as indicators of tumor response, were determined. The type of anti-GnRH antibody response was correlated to the time elapsed until the first biochemical recurrence in patients and the outcome of the disease.

RESULTS

All patients developed strong and prolonged anti-GnRH antibody responses, resulting in a short- to mid-term decrease in serum testosterone and PSA levels. Following immunizations, anti-GnRH antibodies of the IgM/IgG and IgG1/IgG3 subclasses were observed. Following radiotherapy, the humoral response switched to IgG (IgG1/IgG4). Patients who experienced a short-term biochemical relapse were characterized by significantly higher levels of anti-GnRH IgG titers, particularly IgG1 and IgG4 subclasses. These characteristics, along with a high response of specific IgM antibodies at the end of immunizations and the development of anti-GnRH IgA antibody responses following radiotherapy, were observed in patients whose disease progressed, compared to those with controlled disease.

CONCLUSION

The nature of the humoral response against anti-GnRH, induced by vaccination may play a key role in activating additional immunological mechanisms. Collectively, these mechanisms could contribute significantly to the regulation of tumor growth.

A phase 1 dose-sparing, randomized clinical trial of seasonal trivalent inactivated influenza vaccine combined with MAS-1, a novel water-in-oil adjuvant/delivery system

BACKGROUND

New influenza vaccines are needed to increase vaccine efficacy. Adjuvants may allow hemagglutinin (HA) dose-sparing with enhanced immunogenicity. MAS-1 is an investigational low viscosity, free-flowing, water-in-oil emulsion-based adjuvant/delivery system comprised of stable nanoglobular aqueous droplets.

METHODS

A phase 1, double-blind, safety and immunogenicity, HA dose escalation, randomized clinical trial was conducted. MAS-1 adjuvant with 1, 3, 5 or 9 µg per HA derived from licensed seasonal trivalent high dose inactivated influenza vaccine (IIV, Fluzone HD 60 µg per HA) in a 0.3 mL dose were compared to standard dose IIV (Fluzone SD, 15 µg per HA). Safety was measured by reactogenicity, adverse events, and clinical laboratory tests. Serum hemagglutination inhibition (HAI) antibody titers were measured for immunogenicity.

RESULTS

Seventy-two subjects, aged 18-47 years, received one dose of either 0.3 mL adjuvanted vaccine or SD IIV intramuscularly. Common injection site and systemic reactions post-vaccination were mild tenderness, induration, pain, headache, myalgia, malaise and fatigue. All reactions resolved within 14 days post-vaccination. Safety laboratory measures were not different between groups. Geometric mean antibody titers, geometric mean fold increases in antibody titer, seroconversion rates and seroprotection rates against vaccine strains were in general higher and of longer duration (day 85 and 169 visits) with MAS-1-adjuvanted IIV at all doses of HA compared with SD IIV. Adjuvanted vaccine induced higher antibody responses against a limited number of non-study vaccine influenza B and A/H3N2 viruses including ones from subsequent years.

CONCLUSION

MAS-1 adjuvant in a 0.3 mL dose volume provided HA dose-sparing effects without safety concerns and induced higher HAI antibody and seroconversion responses through at least 6 months, demonstrating potential to provide greater vaccine efficacy throughout an influenza season in younger adults. In summary, MAS-1 may provide enhanced, more durable and broader protective immunity compared with non-adjuvanted SD IIV. Clinical Trial Registry: ClinicalTrials.gov # NCT02500680.

MAS-1, a novel water-in-oil adjuvant/delivery system, with reduced seasonal influenza vaccine hemagglutinin dose may enhance potency, durability and cross-reactivity of antibody responses in the elderly

BACKGROUND

Increased influenza vaccine efficacy is needed in the elderly at high-risk for morbidity and mortality due to influenza infection. Adjuvants may allow hemagglutinin (HA) dose-sparing with enhanced immunogenicity. MAS-1 is an investigational water-in-oil emulsion-based adjuvant/delivery system comprised of stable nanoglobular aqueous droplets.

METHODS

A phase 1, randomized, double-blind, safety and immunogenicity, adjuvant dose escalation trial was conducted in persons aged 65 years and older. MAS-1 adjuvant dose volumes at 0.3 mL or 0.5 mL containing 9 µg per HA derived from licensed seasonal trivalent influenza vaccine (IIV, Fluzone HD 60 µg per HA, Sanofi Pasteur) were compared to high dose (HD) IIV (Fluzone HD). Safety was measured by reactogenicity, adverse events, and safety laboratory measures. Immunogenicity was assessed by serum hemagglutination inhibition (HAI) antibody titers.

RESULTS

Forty-five subjects, aged 65-83 years, were randomly assigned to receive 9 µg per HA in 0.3 mL MAS-1 (15 subjects) or HD IIV (15 subjects) followed by groups randomly assigned to receive 9 µg per HA in 0.5 mL MAS-1 (10 subjects) or HD IIV (5 subjects). Injection site tenderness, induration, and pain, and headache, myalgia, malaise and fatigue were common, resolving before day 14 post-vaccination. Clinically significant late-onset injection site reactions occurred in four of ten subjects at the 0.5 mL adjuvant dose. Safety laboratory measures were within acceptable limits. MAS-1-adjuvanted IIV enhanced mean antibody titers, mean-fold increases in antibody titer, and seroconversion rates against vaccine strains for at least 168 days post-vaccination and enhanced cross-reactive antibodies against some non-study vaccine influenza viruses.

CONCLUSION

MAS-1 adjuvant provided HA dose-sparing without safety concerns at the 0.3 mL dose, but the 0.5 mL dose caused late injection site reactions. MAS-1-adjuvanted IIV induced higher HAI antibody responses with prolonged durability including against historical strains, thereby providing greater potential vaccine efficacy in the elderly throughout an influenza season. Clinical Trial Registry: ClinicalTrials.gov # NCT02500680.

Sustainability of Pork Production with Immunocastration in Europe

Immunocastration, a technique to replace surgical castration of piglets, consists of two consecutive vaccinations to induce antibodies which transiently suppress testicular functions and avoid boar taint. It is a method to ensure both a high product quality and a high level of animal welfare. The impact of immunocastration on the three pillars of sustainability has been studied extensively. While all aspects of sustainability have been studied separately, however, a contemporary global overview of different aspects is missing. In immunocastrates, performance results are better than in barrows, but worse than in boars. The environmental impact of pork production with immunocastrates is lower than with barrows, but higher than with boars. The level of aggression is considerably lower in immunocastrates compared to boars. Societal concerns are mainly related to food safety, and are not supported by scientific evidence. After second vaccination, immunocastrates switch from a boar- to a barrow-like status. Therefore, the timing of second vaccination is a fine-tuning tool to balance advantages of boars with environmental and economic benefits against increased risk of welfare problems and boar taint. Nevertheless, both synergic and conflicting relationships between the pillars of sustainability must be communicated along the value chain to produce tailored pork products.

Safety and Therapeutic Profile of a GnRH-Based Vaccine Candidate Directed to Prostate Cancer. A 10-Year Follow-Up of Patients Vaccinated With Heberprovac

Heberprovac is a GnRH based vaccine candidate containing 2.4 mg of the GnRHm1-TT peptide as the main active principle; 245 μg of the very small size proteoliposomes adjuvant (VSSP); and 350 μL of Montanide ISA 51 VG oil adjuvant. The aim of this study was to assess the safety and tolerance of the Heberprovac in advanced prostate cancer patients as well as its capacity to induce anti-GnRH antibodies, the subsequent effects on serum levels of testosterone and PSA and the patient overall survival. The study included eight patients with histologically-proven advanced prostate cancer with indication for hormonal therapy, who received seven intramuscular immunizations with Heberprovac within 18 weeks. Anti-GnRH antibody titers, testosterone and PSA levels, as well as clinical parameters were recorded and evaluated. The vaccine was well tolerated. Significant reductions in serum levels of testosterone and PSA were seen after four immunizations. Castrate levels of testosterone were observed in all patients at the end of the immunization schedule, which remained at the lowest level for at least 20 months. In a 10-year follow-up three out of six patients who completed the entire trial survived. In contrast only one out eight patients survived in the same period in a matched randomly selected group receiving standard anti-hormonal treatment. Heberprovac vaccination showed a good security profile, as well as immunological, biochemical and, most importantly, clinical benefit. The vaccinated group displayed survival advantage compared with the reference group that received standard treatment. These results warrant further clinical trials with Heberprovac involving a larger cohort.

Effects of GnRH vaccination in wild and captive African Elephant bulls (Loxodonta africana) on reproductive organs and semen quality

OBJECTIVES

Although the African elephant (Loxodonta africana) is classified as endangered by the International Union for Conservation of Nature (IUCN), in some isolated habitats in southern Africa, contraception is of major interest due to local overpopulation. GnRH vaccination has been promoted as a non-invasive contraceptive measure for population management of overabundant wildlife. We tested the efficacy of this treatment for fertility control in elephant bulls.

METHODS

In total, 17 male African elephants that were treated with a GnRH vaccine were examined in two groups. In the prospective study group 1 (n = 11 bulls, ages: 8-36 years), semen quality, the testes, seminal vesicles, ampullae and prostate, which were all measured by means of transrectal ultrasound, and faecal androgen metabolite concentrations were monitored over a three-year period. Each bull in the prospective study received 5 ml of Improvac® (1000 μg GnRH conjugate) intramuscularly after the first examination, followed by a booster six weeks later and thereafter every 5-7 months. In a retrospective study group (group 2, n = 6, ages: 19-33 years), one examination was performed on bulls which had been treated with GnRH vaccine for 5-11 years.

RESULTS

In all bulls of group 1, testicular and accessory sex gland sizes decreased significantly after the third vaccination. In six males examined prior to vaccination and again after more than five vaccinations, the testis size was reduced by 57.5%. Mean testicular height and length decreased from 13.3 ± 2.6 cm x 15.2 ± 2.8 cm at the beginning to 7.6 ± 2.1 cm x 10.2 ± 1.8 cm at the end of the study. Post pubertal bulls (>9 years, n = 6) examined prior to vaccination produced ejaculates with viable spermatozoa (volume: 8-175 ml, sperm concentration: 410-4000x106/ml, total motility: 0-90%), while after 5-8 injections, only 50% of these bulls produced ejaculates with a small number of immotile spermatozoa. The ejaculates of group 2 bulls (vaccinated >8 times) were devoid of spermatozoa. Faecal androgen metabolite concentrations measured in captive males decreased significantly after the fourth vaccination. None of the males entered musth during the treatment period.

CONCLUSIONS

Our results showed a marked decrease in semen quality, testicle and secondary sex gland sizes following repeated GnRH vaccinations. After 2-4 years of continuous treatment every 5-7 months, the effects were similar to surgical castration.

Effect of TLR ligands co-encapsulated with multiepitopic antigen in nanoliposomes targeted to human DCs via Fc receptor for cancer vaccines

Nanoliposomes (NLs) hold promise as new highly specific nanomedicine for anti-tumor vaccines, since they could be targeted to specific receptors on dendritic cell (DC) to induce maturation and activation and increase the anti-tumor immune response. Here we studied a NLs formulation targeted or not to FcR (the receptor for the IgG Fc fragment) for the treatment of androgen-responsive prostate cancer. Luteinizing-hormone-releasing hormone (LHRH) peptide (B- and T-cell epitopes), in tandem with a tetanus toxoid T-helper epitope (830-844 region) and several TLR (Toll-Like Receptor) ligands as adjuvants were co-encapsulated. Specific uptake in vitro of LHRH-TT liposomes targeted to the FcRs of human DCs was enhanced. DC maturation/activation, cytokine production and lymphocyte activation were consistently higher in targeted than non-targeted liposomes. Similar increase was observed as more adjuvants were administrated. Targeting to specific receptor and co-encapsulation of several TLR adjuvants are essential factors for the immune response in peptide based liposome vaccine.

Effects of active immunization against GnRH versus surgical castration on hypothalamic-pituitary function in boars

The objective was to compare effects of anti-GnRH immunization (immunocastration) versus surgical castration on hypothalamic-pituitary function in boars. Thirty-six boars were randomly divided into three groups (n = 12/group): control, surgically castrated, or immunized against GnRH at 10 wk of age (boostered 8 wk later). Compared to intact boars, immunocastration reduced (P < 0.05) serum concentrations of LH, FSH, testosterone and inhibin B and caused severe testicular atrophy, whereas surgical castration increased (P < 0.05) serum concentrations of LH and FSH. Both immunocastration and surgical castration consistently reduced hypothalamic GnRH synthesis, with decreased (P < 0.05) mRNA expressions of GnRH, GnRH up-stream gatekeeper genes kiss1 and its receptor (GPR54), and androgen receptor in the hypothalamic arcuate nucleus (ARC) and anteroventral periventricular nucleus (AVPV), as well as GnRH content in the median eminence. Inconsistently, mRNA expressions of gonadotropin-inhibitory hormone (GnIH) in ARC and AVPV as well as its receptor (GPR147) in pituitary were selectively reduced (P < 0.05), but mRNA expressions of estrogen receptor alpha and aromatase (CPY17A1) in pituitary were selectively increased (P < 0.05) in surgical castrates. In response to selectively attenuated suppressive signaling from GnIH and testosterone, mRNA expressions of GnRH receptor (GnRHR), LH-β and FSH-β in pituitary were increased (P < 0.05) in surgical castrates, whereas these pituitary gene expressions were decreased (P < 0.05) in immunocastrates, due to loss of hypothalamic GnRH signaling. We concluded that immunocastration and surgical castration consistently reduced hypothalamic GnRH synthesis due to a testosterone deficiency disrupting testosterone-Kisspeptin-GPR54-GnRH signaling pathways. Furthermore, selectively attenuated GnIH and testosterone signaling in the pituitary increased gonadotropin production in surgical castrates.

Development of a novel recombinant LHRH fusion protein for therapy of androgen and estrogen dependent cancers

LHRH based vaccines are promising candidates for therapy of androgen and estrogen dependent cancers. We report in this communication development of a novel recombinant protein vaccine candidate against LHRH. A synthetic gene was designed in which the codon sequence in the LHRH decapeptide was modified by substituting the codon for 6-glycine with that of l-leucine. Further the LHRH(6leu) gene was linked to heat-labile enterotoxin of E. coli (LTB) as carrier. This LHRH(6leu)-LTB gene was cloned into a prokaryotic expression vector under the control of inducible and strong bacteriophage T7 promoter to over-express LHRH(leu) fused to LTB as recombinant protein in E. coli. Recombinant LHRH(leu)-LTB protein of ∼14 kDa size, was purified from inclusion bodies using in-situ refolding on the column and Ni-NTA based immobilized affinity chromatography. Western blot confirmed the immunoreactivity of purified LHRH(leu)-LTB fusion protein with anti-LHRH monoclonal antibody. The vaccine protein was further characterized by mass spectroscopy, circular dichroism and fluorescence spectroscopy. This communication reports a recombinant LHRH fusion protein with potential for blocking of sex hormones production for eventual therapy of sex hormones dependent neoplasms.

Targeted vaccination against the bevacizumab binding site on VEGF using 3D-structured peptides elicits efficient antitumor activity

Therapeutic targeting of the VEGF signaling axis by the VEGF-neutralizing monoclonal antibody bevacizumab has clearly demonstrated clinical benefit in cancer patients. To improve this strategy using a polyclonal approach, we developed a vaccine targeting VEGF using 3D-structured peptides that mimic the bevacizumab binding site. An in-depth study on peptide optimization showed that the antigen's 3D structure is essential to achieve neutralizing antibody responses. Peptide 1 adopts a clear secondary, native-like structure, including the typical cysteine-knot fold, as evidenced by CD spectroscopy. Binding and competition studies with bevacizumab in ELISA and surface plasmon resonance analysis revealed that peptide 1 represents the complete bevacizumab binding site, including the hairpin loop (β5-turn-β6) and the structure-supporting β2-α2-β3 loop. Vaccination with peptide 1 elicited high titers of cross-reactive antibodies to VEGF, with potent neutralizing activity. Moreover, vaccination-induced antisera displayed strong angiostatic and tumor-growth-inhibiting properties in a preclinical mouse model for colorectal carcinoma, whereas antibodies raised with peptides exclusively encompassing the β5-turn-β6 loop (peptides 15 and 20) did not. Immunization with peptide 1 or 7 (murine analog of 1) in combination with the potent adjuvant raffinose fatty acid sulfate ester (RFASE) showed significant inhibition of tumor growth in the B16F10 murine melanoma model. Based on these data, we conclude that this vaccination technology, which is currently being investigated in a phase I clinical trial (NCT02237638), can potentially outperform currently applied anti-VEGF therapeutics.

Therapies to Preserve β-Cell Function in Type 1 Diabetes

In spite of modern techniques, the burden for patients with type 1 diabetes mellitus will not disappear, and type 1 diabetes will remain a life-threatening disease causing severe complications and increased mortality. We have to learn of ways to stop the destructive process, preserve residual insulin secretion or even improve the disease via β-cell regeneration. This will give a milder disease, a more stable metabolism, simpler treatment and perhaps even cure. Therapies based on single drugs have not shown sufficient efficacy; however, there are several treatments with encouraging efficacy and no apparent, or rather mild, adverse events. As the disease process is heterogeneous, treatments have to be chosen to fit relevant subgroups of patients, and step by step efficacy can possibly be improved by the use of combination therapies. Thus immunosuppressive therapies like anti-CD3 and anti-CD20 monoclonal antibodies might be combined with fusion proteins such as etanercept [tumor necrosis factor (TNF)-α inhibitor] and/or abatacept (CTLA4-Ig) early after onset to stop the destructive process, supported by β-cell protective agents. The effect may be prolonged by using autoantigen therapy [glutamate decarboxylase (GAD) proinsulin], and by adding agents facilitating β-cell regeneration [e.g. glucagon-like peptide-1 (GLP-1)] there should be a good chance to make the disease milder, perhaps leading to cure in some patients.

Ovarian down Regulation by GnRF Vaccination Decreases Reproductive Tract Tumour Size in Female White and Greater One-Horned Rhinoceroses

Reproductive tract tumours, specifically leiomyoma, are commonly found in female rhinoceroses. Similar to humans, tumour growth in rhinoceroses is thought to be sex hormone dependent. Tumours can form and expand from the onset of ovarian activity at puberty until the cessation of sex-steroid influences at senescence. Extensive tumour growth results in infertility. The aim of this study was to down regulate reproductive function of tumour-diseased and infertile females to stop further tumour growth using a Gonadotropin releasing factor (GnRF) vaccine. Four infertile southern white (Ceratotherium simum simum) and three Greater one-horned rhinoceroses (rhinoceros unicornis) with active ovaries and 2.7 ± 0.9 and 14.0 ± 1.5 reproductive tract tumours respectively were vaccinated against GnRF (Improvac®, Zoetis, Germany) at 0, 4 and 16 weeks and re-boostered every 6-8 months thereafter. After GnRF vaccination ovarian and luteal activity was suppressed in all treated females. Three months after vaccination the size of the ovaries, the number of follicles and the size of the largest follicle were significantly reduced (P<0.03). Reproductive tract tumours decreased significantly in diameter (Greater-one horned rhino: P<0.0001; white rhino: P<0.01), presumably as a result of reduced sex-steroid influence. The calculated tumour volumes were reduced by 50.8 ± 10.9% in Greater one-horned and 48.6 ± 12.9% in white rhinoceroses. In conclusion, GnRF vaccine effectively down regulated reproductive function and decreased the size of reproductive tract tumours in female rhinoceros. Our work is the first to use down regulation of reproductive function as a symptomatic treatment against benign reproductive tumour disease in a wildlife species. Nonetheless, full reversibility and rhinoceros fertility following GnRF vaccination warrants further evaluation.

Humoral immune responses against gonadotropin releasing hormone elicited by immunization with phage-peptide constructs obtained via phage display

Phage display is based on genetic engineering of phage coat proteins resulting in fusion peptides displayed on the surface of phage particles. The technology is widely used for generation of phages with novel characteristics for numerous applications in biomedicine and far beyond. The focus of this study was on development of phage-peptide constructs that stimulate production of antibodies against gonadotropin releasing hormone (GnRH). Phage-peptide constructs that elicit production of neutralizing GnRH antibodies can be used for anti-fertility and anti-cancer applications. Phage-GnRH constructs were generated via selection from a phage display library using several types of GnRH antibodies as selection targets. Such phage constructs were characterized for sequence similarities to GnRH peptide and frequency of their occurrence in the selection rounds. Five of the constructs with suitable characteristics were tested in mice as a single dose 5×10(11) virions (vir) vaccine and were found to be able to stimulate production of GnRH-specific antibodies, but not to suppress testosterone (indirect indicator of GnRH antibody neutralizing properties). Next, one of the constructs was tested at a higher dose of 2×10(12) vir per mouse in combination with a poly(lactide-co-glycolide) (PLGA)-based adjuvant. This resulted in multifold increase in GnRH antibody production and significant reduction of serum testosterone, indicating that antibodies produced in response to the phage-GnRH immunization possess neutralizing properties. To achieve optimal immune responses for desired applications, phage-GnRH constructs can be modified with respect to flanking sequences of GnRH-like peptides displayed on phage. Anticipated therapeutic effects also might be attained using optimized phage doses, a combination of several constructs in a single treatment, or application of adjuvants and advanced phage delivery systems.

MAS-1 adjuvant immunotherapy generates robust Th2 type and regulatory immune responses providing long-term protection from diabetes in late-stage pre-diabetic NOD mice

MAS-1, a nanoparticular, emulsion-based adjuvant, was evaluated for its ability to promote Th2 and regulatory immune responses and prevent type 1 diabetes progression when given alone or as antigen-specific immunotherapy (ASI) using insulin B chain (IBC; MER3101) and its analog B:9-23(19Ala) (MER3102). MAS-1 formulations were administered to NOD mice at age 9 and 13 weeks and followed through 52 weeks. MER3101 and MER3102 provided long-term protection with 60% and 73% of mice remaining diabetes-free at week 35, and 60% and 47% at week 52. MAS-1 adjuvant emulsion by itself also provided protection with 60% and 40% of mice diabetes-free at 35 and 52 weeks, respectively. Higher levels of interleukin (IL)-10 and IL-2 positive T cells were detected among splenocytes by week 15 in MER3101 and MER3102 immunized mice, whereas MAS-1 alone induced higher levels of IL-10-positive T cells. Diabetes-free 52-week-old mice expressed significant levels of antigen-specific IL-10-positive type 1 regulatory T cells and FoxP3-positive T cells when stimulated ex vivo with IBC. Antibodies targeting IBC and B:9-23(19Ala) induced by MER3101 and MER3102 were overwhelmingly Th2 type IgG1 and IgG2b isotypes. Splenocyte cultures from 52 week diabetes-free, MER3101-treated mice secreted significantly increased levels of IL-4 and IL-5 Th2 cytokines. Based on these pre-clinical results and its clinical safety profile, MAS-1 has the requisite qualities to be considered for use in prophylactic or early stage disease settings to augment ASI to prevent disease progression in type 1 diabetes.

MER5101, a novel Aβ1-15:DT conjugate vaccine, generates a robust anti-Aβ antibody response and attenuates Aβ pathology and cognitive deficits in APPswe/PS1ΔE9 transgenic mice

Active amyloid-β (Aβ) immunotherapy is under investigation to prevent or treat early Alzheimer's disease (AD). In 2002, a Phase II clinical trial (AN1792) was halted due to meningoencephalitis in ∼6% of the AD patients, possibly caused by a T-cell-mediated immunological response. Thus, generating a vaccine that safely generates high anti-Aβ antibody levels in the elderly is required. In this study, MER5101, a novel conjugate of Aβ1-15 peptide (a B-cell epitope fragment) conjugated to an immunogenic carrier protein, diphtheria toxoid (DT), and formulated in a nanoparticular emulsion-based adjuvant, was administered to 10-month-old APPswe/PS1ΔE9 transgenic (Tg) and wild-type (Wt) mice. High anti-Aβ antibody levels were observed in both vaccinated APPswe/PS1ΔE9 Tg and Wt mice. Antibody isotypes were mainly IgG1 and IgG2b, suggesting a Th2-biased response. Restimulation of splenocytes with the Aβ1-15:DT conjugate resulted in a strong proliferative response, whereas proliferation was absent after restimulation with Aβ1-15 or Aβ1-40/42 peptides, indicating a cellular immune response against DT while avoiding an Aβ-specific T-cell response. Moreover, significant reductions in cerebral Aβ plaque burden, accompanied by attenuated microglial activation and increased synaptic density, were observed in MER5101-vaccinated APPswe/PS1ΔE9 Tg mice compared with Tg adjuvant controls. Last, MER5101-immunized APPswe/PS1ΔE9 Tg mice showed improvement of cognitive deficits in both contextual fear conditioning and the Morris water maze. Our novel, highly immunogenic Aβ conjugate vaccine, MER5101, shows promise for improving Aβ vaccine safety and efficacy and therefore, may be useful for preventing and/or treating early AD.

Very small size proteoliposomes (VSSP) and Montanide combination enhance the humoral immuno response in a GnRH based vaccine directed to prostate cancer

Very small size proteoliposomes (VSSP) constitute a complex of very small size proteoliposomes that includes proteins, lipids, CpG and gangliosides tumor-associated that provides a potential target for cancer immunotherapy. This compound has been described to stimulate the humoral and cellular response, dendritic cells (DC) activation and differentiation of T-helper cells, specially, in immunocompromised patients with cancer status. This work deals with the stimulating capacity of the VSSP to reach a humoral response when they are used as a component in a peptidic vaccine based on the gonadotrophin releasing hormone (GnRH). This study was carried out in male Copenhagen rats, which were immunized with 750μg of the GnRH mimetic peptide (GnRHm1-TT) with or without the VSSP. The mixtures were always emulsified with the oil adjuvant Montanide ISA 51. The anti GnRH seroconversion analysis revealed that the group immunized with the peptide GnRHm1-TT/VSSP developed a strong anti GnRH seroconversion. These antibody levels proved to be significant superior to those reached by the use of the GnRHm1-TT peptide solely emulsified in Montanide. Post-mortem analysis on the Testosterone ablation target organs (prostate and testicles) yielded a sudden decrease in their size and weight in respect to the control group. On the other hand, the group submitted to the use of GnRHm1-TT/VSSP, showed a significant difference in the reduction of these target organs in comparison with the group only immunized with GnRHm1-TT adjuvated in Montanide ISA 51. These values turned to be of p=0.023 and p=0.009 in the prostate and testicles respectively. These findings foreground the VSSP as a useful immunopotentiator to be used as part of a GnRH based vaccine to treat prostate cancer.

Pharmacological and toxicological assessment of a potential GnRH vaccine in young-adult male pigs

Active immunization against gonadotrophin-releasing hormone (GnRH) is successfully applied to prevent boar taint in pork. In men, GnRH immunization could be an alternative to hormone therapy in patients with prostate cancer. In this study, a new GnRH vaccine formulation (a modified GnRH peptide conjugate formulated with CoVaccine adjuvant) was investigated for its pharmacological efficacy and safety in young-adult male pigs. Immunization resulted in castrate-like plasma testosterone levels in all treated pigs from week 8 until the end of the study, 30 weeks after the first immunization. Testosterone depletion retarded testes growth, reduced the relative weight of the testes and accessory sex organs, and reduced sperm counts and motility. There was no clinically relevant toxicity. Typical vaccination-related adverse reactions, such as swelling at the injection site and fever, were considered acceptable. We conclude that this GnRH vaccine efficiently and rapidly reduced serum testosterone levels, without inducing chronic toxic effects, and therefore could be applicable in both veterinary and human medicine.

Effects of Kamdhenu Ark and Active Immunization by Gonadotropin Releasing Hormone Conjugate (GnRH-BSA) on Gonadosomatic Indices (GSI) and Sperm Parameters in Male Mus musculus

BACKGROUND

Active immunization against GnRH decreases the secretion of gonadotropins and causes cessation of gonadal function, thereby, inducing infertility. Based on the immunoenhancing activity of Kamdhenu ark (distilled cow urine), this study was performed to evaluate its effects on the gonadosomatic indices (GSI) and sperm parameters in male mice receiving a GnRH contraceptive vaccine.

METHODS

Sixty adult male mice of Parke's strain were divided into three groups of twenty. Group I served as the controls, while group II was immunized by GnRH-BSA conjugate (50/0.2/35 µg/ml/g BW) by four intraperitoneal injections at different intervals on days 1, 30, 60 and 90. However, group III was supplemented daily by oral Kamdhenu ark (100 ppm) along with GnRH-BSA immunizations. The animals were sacrificed after 30, 60, 90 and 120 days and their testis and epididymis were dissected out weighed and semen analysis was performed.

RESULTS

GSI values, sperm motility, sperm count and sperm morphology in male Mus musculus were decreased significantly in all the experimental groups as compared to the control group (p<0.01). Kamdhenu ark significantly enhanced the effect of GnRH vaccine on the aforesaid parameters especially in 90 and 120 days treated groups (p<0.05).

CONCLUSION

The changes witnessed in sperm parameters suggested that the GnRH-BSA immunization suppressed the activities of gonadotropins and testosterone directly through hypothalamo-hypophysial-gonadal axis and indirectly by acting on the testes which may modulate the sperm morphology, sperm count and motility. However, Kamdhenu ark seems to have enhanced these effects because of its immune-modulatory properties too.

Immunization with a recombinant GnRH vaccine fused to heat shock protein 65 inhibits mammary tumor growth in vivo

Gonadotrophin-releasing hormone (GnRH) is the prime decapeptide hormone in the regulation of mammalian reproduction. Active immunization against GnRH has been a good treatment option to fight against hormone-dependent disease such as breast cancer. We designed and purified a novel protein vaccine Hsp65-GnRH(6) containing heat shock protein 65 (Hsp65) and six copies of GnRH in linear alignment. Immunization with Hsp65-GnRH(6) evoked strong humoral response in female mice. The generation of specific anti-GnRH antibodies was detected by ELISA and verified by western blot. In addition, anti-GnRH antibodies effectively neutralized endogenous GnRH activity in vivo, as demonstrated by the degeneration of the ovaries and uteri in the vaccinated mice. Moreover, the growth of EMT-6 mammary tumor allografts was inhibited by anti-GnRH antibodies. Histological examinations have shown that there was increased focal necrosis in tumors. Taken together, our results showed that immunization with Hsp65-GnRH(6) elicited high titer of specific anti-GnRH antibodies and further led to atrophy of reproductive organs. The specific antibodies could inhibit the growth of EMT-6 murine mammary tumor probably via an indirect mechanism that includes the depletion of estrogen. In view of these results, the protein vaccine Hsp65-GnRH(6) appears to be a promising candidate vaccine for hormone-dependent cancer therapy.

New frontiers in nonhormonal male contraception

The world's population is nearing 6.8 billion, and we are in need of a male contraceptive that is safe, effective, reversible and affordable. Hormonal approaches, which employ different formulations of testosterone administered in combination with other hormones, have shown considerable promise in clinical trials, and they are currently at the forefront of research and development. However, the long-term effects of using hormones throughout a male's reproductive life for contraception are unknown, and it may take decades before this information becomes available. Because of this, many investigators are aiming to bring a nonhormonal male contraceptive to the consumer market. Indeed, there are several distinct but feasible avenues in which fertility can be regulated without affecting the hypothalamus-pituitary-testis axis. In this review, we discuss several approaches for fertility control involving the testis that one day may lead to the development of a nonhormonal male contraceptive.

Versatile virus-like particle carrier for epitope based vaccines

BACKGROUND

Recombinant proteins and in particular single domains or peptides are often poorly immunogenic unless conjugated to a carrier protein. Virus-like-particles are a very efficient means to confer high immunogenicity to antigens. We report here the development of virus-like-particles (VLPs) derived from the RNA bacteriophage AP205 for epitope-based vaccines.

METHODOLOGY/PRINCIPAL FINDINGS

Peptides of angiotensin II, S.typhi outer membrane protein (D2), CXCR4 receptor, HIV1 Nef, gonadotropin releasing hormone (GnRH), Influenza A M2-protein were fused to either N- or C-terminus of AP205 coat protein. The A205-peptide fusions assembled into VLPs, and peptides displayed on the VLP were highly immunogenic in mice. GnRH fused to the C-terminus of AP205 induced a strong antibody response that inhibited GnRH function in vivo. Exposure of the M2-protein peptide at the N-terminus of AP205 resulted in a strong M2-specific antibody response upon immunization, protecting 100% of mice from a lethal influenza infection.

CONCLUSIONS/SIGNIFICANCE

AP205 VLPs are therefore a very efficient and new vaccine system, suitable for complex and long epitopes, of up to at least 55 amino acid residues in length. AP205 VLPs confer a high immunogenicity to displayed epitopes, as shown by inhibition of endogenous GnRH and protective immunity against influenza infection.

Vaccines for immunological control of fertility

Vaccines have been proposed as one of the strategies for population control. Immunocontraceptive vaccines can be designed to inhibit: (1) production of gametes (sperm and egg); (2) functions of gametes, leading to blocking of fertilization; and (3) gamete outcome (pregnancy). Immunization with gonadotropin-releasing hormone coupled to different carriers has shown curtailment in the production of sperm with concomitant infertility in various species. Immunization of nonhuman primates and men with ovine follicle stimulating hormone has also resulted in reduced sperm output. Various spermatozoa-specific proteins such as FA1, PH-20, LDH-C₄, SP-10, SP-17, sp56, SPAG9, and Izumo have been proposed as candidate antigens to develop contraceptive vaccines, which have shown efficacy in inhibiting fertility in different animal models. Immunization with zona pellucida glycoproteins-based immunogens also results in curtailment of fertility in a variety of species. However, ways to overcome the observed oophoritis associated with zona proteins immunization have yet to be discovered, a necessary step before their proposal for control of human population. Nonetheless, this is a very promising approach to control wildlife animal population. Phase II clinical trials of β-human chorionic gonadotropin-based vaccine in women have established the proof of principle that it is possible to inhibit fertility without any untoward side-effects by vaccination. Further scientific inputs are required to increase the efficacy of contraceptive vaccines and establish their safety beyond doubt, before they can become applicable for control of fertility in humans.

Gonadotrophin releasing hormone-based vaccine, an effective candidate for prostate cancer and other hormone-sensitive neoplasms

Prostate growth, development, functions, and neoplastic transformation is androgen dependent. Estrogens have similar effects in the ovary and breast. Previous studies using gonadotrophin releasing hormone (GnRH/LHRH) vaccines have shown the usefulness of immunization against this hormone in prostate (PC) and breast cancer (BC). We have synthesized a peptide mutated at position 6 and attached to the 830-844 tetanic toxoid (TT) helper T cell sequence in the same synthesis process. After repeated pig immunizations, we have demonstrated a vaccine that significantly decreased testes size (p < 0.001), prostate (p < 0.01), seminal vesicles (p < 0.01), and testosterone (T) castration [0.05 nM ml(-1) (p < 0. 01)]. Similar results were obtained in adult male and female healthy dogs and Macaca fascicularis models. These data indicate that this GnRHm1-TT vaccine is safe and able to induce significant tumor growth inhibition in the Dunning R3327-H rat androgen responsive prostate tumor model. In these rats, the immunization induced high anti-GnRH titers concomitant with T castration reduction (p < 0.01) in 90% of the animals tested. In addition, 70% of the responders exhibited tumor growth inhibition (p = 0.02) and a survival rate approximately three times longer that those of untreated rats. These data indicate that GnRHm1-TT vaccine may be a potential candidate in the treatment of PC, BC, and other hormone-dependent cancers.

Immunotherapy of prostate cancer in a murine model using a novel GnRH based vaccine candidate

Previous studies with gonadotrophin releasing hormone (GnRH/LHRH) vaccines have shown the usefulness of immunization against this hormone in prostate cancer. To this end, we have generated a completely synthetic peptide modified at position 6 and attached to the 830-844 tetanic toxoid (TT) helper T cell sequence. Through this work we have demonstrated that the GnRHm1-TT molecule was highly immunogenic when it is formulated as an oil-based emulsion adjuvated with Montanide ISA 51. That results correlated directly with testosterone reduction and tumor growth inhibition of the Dunning R3327-H androgen responsive prostate tumor model in rats. GnRHm1-TT, proved to be safe and useful for future clinical trials.

Current status of veterinary vaccines

The major goals of veterinary vaccines are to improve the health and welfare of companion animals, increase production of livestock in a cost-effective manner, and prevent animal-to-human transmission from both domestic animals and wildlife. These diverse aims have led to different approaches to the development of veterinary vaccines from crude but effective whole-pathogen preparations to molecularly defined subunit vaccines, genetically engineered organisms or chimeras, vectored antigen formulations, and naked DNA injections. The final successful outcome of vaccine research and development is the generation of a product that will be available in the marketplace or that will be used in the field to achieve desired outcomes. As detailed in this review, successful veterinary vaccines have been produced against viral, bacterial, protozoal, and multicellular pathogens, which in many ways have led the field in the application and adaptation of novel technologies. These veterinary vaccines have had, and continue to have, a major impact not only on animal health and production but also on human health through increasing safe food supplies and preventing animal-to-human transmission of infectious diseases. The continued interaction between animals and human researchers and health professionals will be of major importance for adapting new technologies, providing animal models of disease, and confronting new and emerging infectious diseases.

Influence of immunization against GnRH on reproductive cyclicity and estrous behavior in the mare

The aim of this study was to evaluate the effect of active immunization against GnRH on ovarian activity, plasma progesterone and estradiol concentrations and on estrous behavior in adult mares. Eighteen cyclic mares were randomly divided into a treatment and control group. Nine mares were immunized twice with 2 mL (400 microg GnRH-protein conjugate) of a GnRH-vaccine (Improvac, CSL Limited, Australia) administered intramuscularly, 4 weeks apart. Control mares received the same amount of saline solution. Ovaries and uterus of all mares were examined weekly by ultrasonography from 3 weeks before to 60 weeks after first immunization. Thereafter, vaccinated mares were evaluated monthly until 100 weeks after first vaccination. In addition, mares were teased with a stallion for assessment of estrous behavior and blood was collected for progesterone, estradiol-17beta and GnRH antibody titer determination. Results demonstrate that vaccination against GnRH significantly (P<0.05) influenced all parameters, except estradiol-17beta concentration. All vaccinated mares ceased reproductive cyclicity (plasma progesterone <1 ng/mL, follicles <3 cm) within 8 weeks after the first injection and ovarian activity remained suppressed for a minimum of 23 weeks. Five mares resumed cyclicity (follicles >3 cm, progesterone >1 ng/mL) while three mares showed only follicular activity (follicles >3 cm) and one mare remained completely suppressed for the entire duration of the study. In spite of ovarian suppression, four mares expressed sporadic and one mare continuous estrous behavior. In conclusion, reproductive cyclicity in adult mares can be successfully suppressed by immunization against GnRH but the timing of resumption of cyclicity is highly variable and estrous behavior may occur in spite of ovarian suppression.

Effect of docetaxel chemotherapy on the activity of a gonadotropin releasing hormone vaccine in patients with advanced prostate cancer

BACKGROUND

Gonadotropin releasing hormone (GnRH)-DT vaccine elicits antibody that may inhibit prostate cancers indirectly by blocking GnRH induced gonadotropin release, and consequent androgen synthesis, and directly by immune effector and antiproliferative mechanisms. A pilot study was performed to determine how to best combine GnRH-DT vaccine with potentially immunosuppressive chemotherapy.

METHODS

Patients with metastatic, hormone-refractory prostate cancer were randomized into either a concurrent cohort, in which they received docetaxel on day 1 of weeks 1, 4, 7, and 10 and GnRH-DT vaccine on day 2 of weeks 1, 3, and 7 or a sequential cohort, in which they received GnRH-DT vaccine on weeks 1, 3, and 7 before beginning docetaxel on week 10. GnRH-DT vaccine was administered intramuscularly. Docetaxel was infused intravenously after pre-medication with high-dose dexamethasone, and infusions repeated every 3 weeks in the absence of toxicity or progressive cancer.

RESULTS

GnRH-DT vaccine and docetaxel were well tolerated without evidence of significant local or systemic toxicities. Anti-GnRH antibody was elicited in six of six treated concurrently and five of six treated sequentially. The kinetics of antibody induction and the titers of antibody achieved in both treatment cohorts were similar. Anti-GnRH antibody persisted for up to 28 weeks in a patient maintained on docetaxel.

CONCLUSION

The administration of docetaxel with high-dose dexamethasone does not inhibit the ability of patients with advanced prostate cancer to be immunized with GnRH-DT vaccine.

GnRH tandem peptides for inducing an immunogenic response to GnRH-I without cross-reactivity to other GnRH isoforms

Gonadotropin releasing hormone (GnRH) occurs in various isoforms in mammals, i.e. GnRH-I (mammalian GnRH), GnRH-II (chicken GnRH-II), GnRH-III (salmon GnRH) and two forms of lamprey GnRH. The function of the latter four molecules have only been partially investigated. Also not much is known about the physiological effects of GnRH-I immunization on the function of these GnRH isoforms. In order to avoid possible harmful side-effects due to undesired neutralization of GnRH isoforms, GnRH-I specificity of antibodies raised against a panel of alternative GnRH antigens was determined. The results show that GnRH antigens can be designed which generate antibodies that specifically bind GnRH-I, without cross-reacting with other GnRH isoforms.

Recent advances in contraceptive vaccine development: a mini-review

Contraceptive vaccines (CV) may provide viable and valuable alternatives to the presently available methods of contraception. The molecules that are being explored for CV development either target gamete production [luteinizing hormone-releasing hormone (LHRH)/GnRH, FSH], gamete function [sperm antigens and oocyte zona pellucida (ZP)], and gamete outcome (HCG). CV targeting gamete production have shown varied degrees of efficacy; however, they either affect sex steroids causing impotency and/or show only a partial rather than a complete effect in inhibiting gametogenesis. However, vaccines based on LHRH/GnRH are being developed by several pharmaceutical companies as substitutes for castration of domestic pets, farm and wild animals, and for therapeutic anticancer purposes such as in prostatic hypertrophy and carcinoma. These vaccines may also find applications in clinical situations that require the inhibition of increased secretions of sex steroids, such as in uterine fibroids, polycystic ovary syndrome, endometriosis and precocious puberty. CV targeting molecules involved in gamete function such as sperm antigens and ZP proteins are exciting choices. Sperm constitute the most promising and exciting target for CV. Several sperm-specific antigens have been delineated in several laboratories and are being actively explored for CV development. Studies are focused on delineating appropriate sperm-specific epitopes, and increasing the immunogenicity (specifically in the local genital tract) and efficacy on the vaccines. Anti-sperm antibody (ASA)-mediated immunoinfertility provides a naturally occurring model to indicate how a vaccine might work in humans. Vaccines based on ZP proteins are quite efficacious in producing contraceptive effects, but may induce oophoritis, affecting sex steroids. They are being successfully tested to control feral populations of dogs, deer, horses and elephants, and populations of several species of zoo animals. The current research for human applicability is focused on delineating infertility-related epitopes (B-cell epitopes) from oophoritis-inducing epitopes (T-cell epitopes). Vaccines targeting gamete outcome primarily focus on the HCG molecule. The HCG vaccine is the first vaccine to undergo Phase I and II clinical trials in humans. Both efficacy and lack of immunopathology have been reasonably well demonstrated for this vaccine. At the present time, studies are focused on increasing the immunogenicity and efficacy of the birth control vaccine, and examining its clinical applications in various HCG-producing cancers. The present article will focus on the current status of the anti-sperm, anti-ZP, anti-LHRH/GnRH and anti-HCG vaccines.

Effects of GnRH immunization in sexually mature pony stallions

Immunization against gonadotrophin releasing hormone (GnRH) was studied as an alternative for the commonly used surgical castration in stallions. Two GnRH vaccines comprising non-mineral oil adjuvants were evaluated for their potential to induce high antibody titers directed against GnRH and subsequent effects on reproductive characteristics. Twelve sexually mature male hemicastrated Shetland ponies were assigned to three groups. Group 1 and 2 were injected with 1mg peptide equivalent of G6k-GnRH-tandem-dimer conjugated to ovalbumin (OVA) in CoVaccine HT adjuvant (GnRH/CoVaccine) and in Carbopol (GnRH/Carbopol), respectively, and group 3 was injected with CoVaccine HT adjuvant without antigen (controls). After immunization no adverse effects were observed with respect to the injections sites or general health. Two weeks after the second vaccination antibody titers against GnRH increased rapidly in all animals of the GnRH/CoVaccine group, at the same time reducing serum testosterone levels maximally for the further duration of the experiment. In the GnRH/Carbopol group antibody responses and effects on testosterone levels were intermediate in two stallions and not apparent in the remaining stallions of this group. Semen evaluation showed that from 2 weeks after the second immunization onwards, sperm motility was affected in all stallions treated with GnRH/CoVaccine and one stallion treated with GnRH/Carbopol. Seven weeks after the second immunization, no semen could be collected from two stallions, one of each group, due to suppressed libido. Histological examination of the testes, 15 weeks after the initial immunization, demonstrated reduction in seminiferous tubuli diameters in all stallions of the GnRH/CoVaccine group and one stallion of the GnRH/Carbopol group. Furthermore, spermatogenesis was extremely disorganized in these stallions, as indicated by absence of the lumen in the seminiferous tubules, the absence of spermatozoa and spermatids in the tubular cross-sections and the impossibility to determine the stage of the tubular cross-sections. Testis size was also substantially reduced in three out of four stallions treated with GnRH/CoVaccine. The results demonstrate that two immunizations with G6k-GnRH-tandem-dimer-OVA conjugate in a suitable adjuvant such as CoVaccine HT caused a rapid and complete reduction of serum testosterone levels in sexually mature stallions, subsequently leading to reduced sperm motility and affected testis function, while no adverse reactions were observed after immunizations.

Contraceptive vaccines

The world's population is growing at a tremendous rate, affecting growth and development. Apart from this population growth, unintended pregnancies resulting in elective abortions continue to be a major public health issue. In over half of these unintended pregnancies, the women have used some type of contraception. Thus, there is an urgent need for a better method of contraception that is acceptable, effective and available. The contraceptive choices available to women at this time include steroid contraceptives, intrauterine devices, barrier methods, spermicides, natural family planning, male and female sterilisation, and recently available emergency contraceptives. Contraceptive vaccines (CVs) may provide viable and valuable alternatives that can fulfill most, if not all, properties of an ideal contraceptive. Since both the developed and most of the developing nations have an infrastructure for mass immunisation, the development of vaccines for contraception is an exciting proposition. The molecules that are being explored for CV development either target gamete production (gonadotropin releasing hormone, follicle-stimulating hormone and luteinising hormone), gamete function (zona pellucida [ZP] proteins and sperm antigens) or gamete outcome (human chorionic gonadotropin [hCG]). Disadvantages of CVs targeting gamete production are that they affect sex steroids and/or show only a partial effect in reducing fertility. CVs targeting gamete function are better choices. Vaccines based on ZP proteins are quite efficacious in producing contraceptive effects. However, they invariably induce oophoritis affecting sex steroids. Sperm antigens constitute the most promising and exciting targets for CVs. Several sperm-specific antigens have been delineated in several laboratories and are being actively explored for CV development. Antisperm antibody-mediated immunoinfertility provides a naturally occurring model to indicate how an antisperm vaccine will work in humans. Vaccines targeting gamete outcome primarily focus on the hCG molecule. The hCG vaccine is the first vaccine to undergo phase I and II clinical trials in humans. Both the efficacy and the lack of immunotoxicity have been reasonably well demonstrated for this vaccine. The present studies focus on increasing the immunogenicity and efficacy of this birth control vaccine.

A totally synthetic vaccine of generic structure that targets Toll-like receptor 2 on dendritic cells and promotes antibody or cytotoxic T cell responses

A simple generic peptide-based vaccine structure that targets Toll-like receptor 2-expressing dendritic cells and causes their activation is described. The vaccines are totally synthetic, serve as their own adjuvant, and are composed of (i) a single helper T cell epitope, (ii) a target epitope that is either recognized by CD8+ T cells or B cells, and (iii) a Toll-like receptor 2-targeting lipid moiety, S-[2,3-bis(palmitoyloxy)propyl]cysteine, that is situated between the peptide epitopes to form a branched configuration. The different CD8+ T cell epitopes examined were from (i) influenza virus, (ii) the intracellular bacterium Listeria monocytogenes, and (iii) ovalbumin as a model tumor antigen. Vaccines containing a B cell epitope from gastrin or luteinizing hormone-releasing hormone as a B cell epitope were also examined for their ability to elicit antibody against the parent hormones. Each of the vaccines was capable of inducing either CD8+ T cell or antibody-mediated immune responses. The lipidated vaccines, but not the nonlipidated vaccines, were able to mediate protection against viral or bacterial infection and mediate prophylactic and therapeutic anticancer activity. The two hormone-based vaccines induced high antibody titers, which in the case of luteinizing hormone-releasing hormone resulted in abrogation of reproductive function. These results highlight the utility of simple, totally synthetic, epitope-based vaccines.

Efficacy of an anti-fertility vaccine based on mammalian gonadotrophin releasing hormone (GnRH-I)—a histological comparison in male animals

A N-terminal modified gonadotrophin releasing hormone (GnRH-I, tetanus toxoid-CHWSYGLRPG-NH2) conjugate was evaluated histologically in a number of male animal species (mice, dogs and sheep). The immunogen has previously been shown to be highly effective in rats, by suppressing both steroidogenesis and spermatogenesis. However, cross-species efficacy of peptide vaccines is known to be highly variable. Therefore, a comparative evaluation of reproductive tissues from animals immunized against this immunogen adsorbed onto an alum-based adjuvant was made. The sheep and dogs were chosen, as use of anti-fertility vaccines in these species is important in farming and veterinary practice. Changes in testicular size were measured during the immunization period and the greatest alteration (attributed to gonadal atrophy) was observed in the rat. Following euthanasia, the testicular tissue was evaluated for spermatogenesis. The most susceptible species to GnRH-I ablation was the rat, which showed significant (P < 0.0001) arrest in spermatogenesis compared with untreated controls. Testicular sections taken from treated animals were completely devoid of spermatozoa or spermatids, in comparison with 94% of the untreated controls showing evidence of spermatogenesis. The immunized mice and rams also showed significant arrest (P < 0.0001). There was a 30-45% decrease in spermatogenesis and total azoospermia was not apparent. However, the least responsive were the dogs, which showed little significant variation compared to untreated animals and only a 5% decrease in activity. A comparison of the specific IgG response to GnRH-I indicated that in sheep and dogs the response was not maintained, unlike in rodents, suggesting that suppression of fertility may be due to differences in immune responses in different animal species.

Binding and cytotoxicity of conjugated and recombinant fusion proteins targeted to the gonadotropin-releasing hormone receptor

Pokeweed antiviral protein (PAP) is a plant-derived, highly potent ribosome inactivating protein that causes inhibition of protein translation and rapid cell death. We and others have delivered this protein to various cell types, including cancer cells, using hormones to specifically target cells bearing the hormone receptor. Here, we compare binding and cytotoxicity of GnRH-PAP hormonotoxins prepared either by protein conjugation (GnRH-PAP conjugate) or through recombinant DNA technology (GnRH-PAP fusion). Although GnRH-PAP conjugate protein bound specifically to and caused cell death in cells bearing the gonadotropin-releasing hormone (GnRH) receptor, we could not detect binding or cytotoxicity using two different versions of the fusion protein in receptor-positive cells. We conclude that generation of an active GnRH-PAP fusion protein may not be feasible either because both ends of the GnRH molecule are required for receptor binding, but only the NH(2) terminus is free in the fusion protein and/or that more potent analogues of GnRH (inclusion of which is not feasible in the fusion protein) are needed for efficient targeting. In contrast, the GnRH-PAP conjugate shows promise as a novel anticancer agent, capable of targeting cancer cells expressing the GnRH receptor such as prostate, breast, ovarian, endometrial, and pancreatic cells. It may also be useful as a therapeutic agent to eliminate pituitary gonadotrophs, eliminating the need for chronic GnRH analogue administration to treat hormone-sensitive diseases.

Synthetic luteinizing hormone releasing hormone (LHRH) vaccine for effective androgen deprivation and its application to prostate cancer immunotherapy

We have designed a peptide-based immunotherapeutic vaccine for treatment of androgen-responsive prostate cancer. The vaccine targets the luteinizing hormone-releasing hormone (LHRH) decapeptide that results in an androgen-deprivation immunotherapy. The design elements of the peptide immunogens are the LHRH peptide or B cell epitope synthetically linked to different promiscuous helper T cell (Th) sequences, the UBITh epitopes, derived from four natural pathogens for effective immunogenicity in outbred populations, and in some cases, also linked to an adjuvanting peptide from Yersinia invasin (Inv) protein. The UBITh LHRH immunogens are adsorbed on Alhydrogel or formulated as several different oil-based emulsions and tested in rodents, dogs, and a non-human primate, baboons. The immunogens generate an anti-LHRH antibody response specific to the LHRH decapeptide element in contrast to LHRH conjugate-carrier protein vaccines where only a small portion of the antibody response is directed to the target epitope and epitopic suppression is noted. Individual UBITh peptide domains, but not the LHRH and Inv peptide domains, are stimulatory in lymphocyte cultures. The UBITh LHRH immunogens in a clinically applicable formulation, controlled the growth of Dunning R3327-H androgen-responsive prostate tumor cells in rats. The results demonstrate universal responsiveness and long duration of androgen deprivation from three diverse species, and thus vaccine efficacy.

A Vaccination Strategy for the Long-Term Suppression of Androgens in Advanced Prostate Cancer

OBJECTIVES

We have previously reported the ability of D17DT (formerly GnRH-DT) vaccination to produce castrate levels of androgens in men with advanced prostate cancer. This study examines the efficacy and tolerability of 3 and 15 micrograms of D17DT in 12 patients with advanced prostate cancer to establish a dose-response relationship.

METHODS

12 patients received either 3 or 15 micrograms of D17DT as 3 deep intramuscular injections over 6 weeks. Outcome was assessed in terms of physical and biochemical evaluations of clinical progression and antibody titres.

RESULTS

Significant titres of anti-GnRH antibodies were detected in 2 out of 6 subjects who received 15 micrograms of D17DT; suppression of testosterone to castrate levels accompanied by a significant and prolonged reduction in PSA was also demonstrated. No responses were seen following treatment with 3 micrograms of D17DT.

CONCLUSION

The induction of anti-GnRH antibodies through vaccination with 15 micrograms D17DT can produce and sustain castrate levels of testosterone in men with advanced prostate cancer.

Immunization against luteinizing hormone-releasing hormone fusion proteins does not decrease prostate cancer in the transgenic adenocarcinoma mouse prostate model

This study was undertaken to test the effect of immunization against luteinizing hormone-releasing hormone (LHRH) fusion proteins on the development and progression of prostate cancer in the transgenic adenocarcinoma mouse prostate (TRAMP) model. Two LHRH fusion proteins, ovalbumin with seven LHRH peptides (OV-LHRH-7), and thioredoxin with seven LHRH peptides (TH-LHRH-7) were used in a cocktail vaccine. Two groups of male TRAMP mice were immunized with the cocktail. Primary immunizations were at either 4 or 8 weeks of age. LHRH immunized mice (n=19) were compared with castrated (n=19) and intact mice (n=18) for testosterone concentration, tumor weight, and lifespan. Immunization against LHRH in the TRAMP mice resulted in significant production of antibodies to LHRH compared with surgically castrated and intact control mice. Testicular weight was significantly reduced in the LHRH immunized groups compared with intact control mice. Serum testosterone was reduced (P<0.05) in the immunized mice compared with intact control mice and was not different from that of castrated mice (P>0.05). Tumor weight was variable and inconsistent throughout all treatment groups. Lifespan was not increased by immunization against LHRH or castration. Intact control mice (lived the longest (227+/-11 days), whereas immunized mice lived 206+/-11 days and castrated mice lived 213+/-13 days. Tumors from immunized TRAMP mice appeared more aggressive than tumors of castrated and intact mice, as demonstrated by 35% expression of gross lung tumors in the immunized mice whereas none were observed in the castrated or intact TRAMP mice. Prostate cancer is initially dependent upon androgens for growth and development, but cells have the ability to escape androgen dependence and progress to an androgen independent state, which was evident in this study. The TRAMP mouse model immunized against LHRH may have utility in future studies and treatments of the androgen independent prostate cancer.

Current advances in antifertility vaccines for fertility control and noncontraceptive applications

The search for effective antifertility vaccines has been actively pursued for decades in clinical applications as contraceptives or in the treatment of hormone-dependent conditions. More recently, innovations have seen immunocontraception being employed successfully in veterinary and farming applications, as well as in population control of a number of different wildlife species. Although the basic principle behind these vaccines is the same, design considerations and criteria for commercialization are very different. This review will examine current advances in this field and evaluate the future scope of antifertility vaccines.

Part II: influence of dimerization of a modified GnRH-I peptide sequence on a male antifertility vaccine

PROBLEM

In the previous paper, we described how the tetanus toxoid (TT) conjugated monomer, CHWSYGLRPG-NH2, induced high neutralizing antibody titres, which resulted in decreased levels of testosterone and subsequent antifertility. However, its counterpart HWSYGLRPGC, induced low avidity antibody titres. We wanted to know whether peptide dimerization would improve the efficacy of both peptides.

METHOD OF STUDY

Male Sprague-Dawley rats were immunized with modified dimerized GnRH-I peptides (HWSYGLRPGCCGPRLGYSWH and GPRLGYSWHCCHWSYGLRPG-NH2), with or without conjugation to TT.

RESULTS

The unconjugated dimers were not effective in causing castration, although the first peptide dimer did induce production of antibodies. When conjugated to TT, both dimers showed the same level of efficacy in causing castration as each other. However, there were differences in antibody binding to native GnRH.

CONCLUSIONS

Dimerization and conjugation to a carrier improved the antifertility efficacy of HWSYGLRPGC, whereas the conjugated monomer CHWSYGLRPG-NH2 showed a greater level of consistent castration than its conjugated dimer.

In vivo properties of an anti-GnRH Spiegelmer: an example of an oligonucleotide-based therapeutic substance class

Spiegelmers are high-affinity l-enantiomeric oligonucleotide ligands that display high resistance to enzymatic degradation compared with d-oligonucleotides. The target binding properties of Spiegelmers can be designed by an in vitro-selection process starting from a random pool of oligonucleotides. Applying this method, a Spiegelmer with high affinity (K(D) = 20 nM) for the peptide hormone, gonadotropin-releasing hormone (GnRH) was isolated. The Spiegelmer acts as an antagonist to GnRH in Chinese hamster ovary cells stably expressing the human GnRH receptor, and its activity is unchanged by linking to 40-kDa polyethylene glycol. In a castrated rat model the Spiegelmer further demonstrated strong GnRH antagonist activity, which is more pronounced and persists longer with the polyethylene glycol-linked derivative. Furthermore, in rabbits the anti-GnRH Spiegelmer was shown to have a very low, possibly negligible immunogenic potential. These studies suggest that Spiegelmers could be of substantial interest in the development of new pharmaceutical approaches against GnRH and other targets.