Immunotherapy of prostate cancer in a murine model using a novel GnRH based vaccine candidate. Vaccine. 2007;25:8460-8468. [PMID: 18022737 DOI: 10.1016/j.vaccine.2007.09.033]

Evaluation of novel single-dose vaccine candidates against gonadotropin-releasing hormone (GnRH) in mice

Immunocontraceptive vaccines targeting gonadotropin-releasing hormone (GnRH) are in high demand for controlling population growth and managing the temperament of both wild and domesticated animals. Achieving adequate efficacy, especially with a single-dose immunization, requires potent vaccines and adjuvants. However, commercial vaccines face challenges: some, like Gonacon®, have regulatory issues with veterinary authorities, while others, like Bopriva®, lack potency and require multiple booster doses. Thus, there is a critical need for highly effective vaccines with robust adjuvants suitable for easy, less invasive single-dose administration. Recent studies have shown that peptide vaccines adjuvanted with 15-mer polyleucine (L15) or poly(methyl acrylate) (PMA) demonstrate potent immunogenicity, comparable to complete Freund's adjuvant (CFA), after a single dose against Streptococcus pyogenes. Our research aims to evaluate the performance of these promising vaccine adjuvant as single-dose contraceptive vaccines in mice, compared to well-established commercial and experimental adjuvants, such as AddaVax®, Incomplete Freunds Adjuvant (IFA), and CFA. To develop a vaccine with sufficient HLA coverage for cattle immunocontraception, we evaluated a peptide vaccine incorporating three cattle-compatible helper T cell epitopes. We evaluated the immunogenicity of constructs in mice to that of a construct with the universal mouse-compatible PADRE (P) helper T cell epitope. Various vaccines were prepared to investigate: (A) the impact of incorporating cattle-compatible helper T cells on immunogenicity, and (B) the effectiveness of different adjuvant systems compared to CFA. The vaccines were administered subcutaneously to C57BL/6 mice, and serological assays revealed that the L15/Quil A-based vaccine system was highly immunogenic, with performance comparable to CFA without the need for reactogenic mycobacterial components. Our vaccines significantly reduced serum progesterone levels in mice, making the L15/Quil A system a strong candidate for single-dose anti-fertility application, followed by PMA, and AddaVax® adjuvanted GnRH.

Diphtheria Toxoid-Derived T-Helper Epitope and α-galactosylceramide Synergistically Enhance the Immunogenicity of Glycopeptide Antigen

The tumor-associated antigen MUC1 is an attractive target for immunotherapy, however, its weak immunogenicity limits the induction of antitumor immune responses. To overcome this limitation, in this study, MUC1 glycopeptide was covalently linked with a diphtheria toxin-derived T-helper epitope (DT331-345). Subsequently, the resulting DT-MUC1 glycopeptide was physically mixed with natural killer T cell agonist αGalCer to explore their immunomodulatory synergy. Biological results demonstrated that compared to MUC1+αGalCer and DT-MUC1 groups, the specific IgG antibody titer of DT-MUC1+αGalCer group increased by 189- and 3-fold, respectively, indicating that the diphtheria toxin-derived T-helper epitope synergistically enhanced MUC1 immunogenicity with αGalCer. Moreover, the DT-MUC1+αGalCer vaccine induced potent cellular immune responses and significantly inhibited the growth of B16-MUC1 tumors in vivo. Furthermore, it was found that the anti-MUC1 IgG antibody titer induced by DT-MUC1+αGalCer was equivalent to that induced by palmitoylated DT-MUC1+αGalCer (P1-DT-MUC1+αGalCer) and significantly higher than that induced by doubly palmitoylated DT-MUC1+αGalCer (P2-DT-MUC1+αGalCer), suggesting that the easily synthesized DT-MUC1 may not require lipid chain modification and already possess good amphiphilicity. This is the first time that a diphtheria toxin-derived helper T-helper epitope was covalently linked to a glycopeptide antigen to enhance its immunogenicity, and this study may provide an effective vaccine design strategy for MUC1-targeted antitumor vaccines and offer novel insights into the design of fully synthetic peptide vaccines.

Palmitic acid-modified GnRH-Th epitope peptide immunocastration vaccine (W/O/W adjuvant) can effectively ensure the castration and reduce the smelly smell in boars

Introduction

Recent studies have demonstrated the effectiveness of Gonadotropin-releasing hormone (GnRH) in inhibiting testicular growth and development in male animals to achieve castration while improving the meat quality of various livestock species, including cattle, sheep, goats, and pigs.

Methods

In this research, a GnRH-Th vaccine was synthesized using the Fmoc solid-phase synthesis technique, and the T helper (Th) antigen was modified with palmitic acid to improve its efficacy. The vaccine was then coated with a water-in-oil-in-water adjuvant to improve stability and safety. After passing safety and stability tests, the vaccine was administered to 13-week-old boars.

Results

The results showed that it was stable, safe, and effective for up to 15 months. Moreover, the vaccine did not negatively affect the growth rate and body weight of the pigs. The palmitic acid-modified "GnRH-Th epitope peptide immunocastration vaccine (Water-in-Oil-in-Water (W/O/W)) effectively reduced the testosterone concentration and achieved castration. The concentration of androstenone and skatole hormones significantly decreased, leading to improved meat quality in the boars. The boars were then slaughtered at 33 weeks of age, and the results showed that the meat quality of the vaccinated boars was superior to that of the non-vaccinated control group (p < 0.05).

Discussion

This study demonstrated that GnRH can safely and effectively achieve immune castration in boars after coupling T cell epitopes, palmitic acid modification and W-O-W coating. Provide a better method for the further development of GnRH and the realization of animal welfare.

A dual kisspeptin-GnRH immunogen for reproductive immunosterilization

GnRH immunogens have been extensively employed in immunocontraception of animals. While they are effective, they are not 100% efficacious and of limited duration. GnRH secretion is dependent on upstream stimulation by kisspeptin. We therefore hypothesised that a dual immunogen combining GnRH and kisspeptin may be more efficacious through targeting two levels of the axis. We have previously shown GnRH immunogen elicits permanent sterilisation when sheep are vaccinated neonatally suggesting that the efficacy of GnRH immunisation may be dependent on the stage of reproductive development. We have now studied over 300 days the efficacy of immunisation with a dual immunogen comprising GnRH linked to kisspeptin via a hepatitis B T helper peptide sequence (GKT) administered to male and female rats prepubertally, pubertally and as adults. At all stages of development all immunised animals produced antibodies to GnRH, kisspeptin and GKT but differentially in titre with respect to sex and stage of development. In immunised adult, prepubertal and pubertal males testosterone and testes length was markedly reduced by 60 days and remained at low levels until day 150. Thereafter, testosterone recovered to pre immunisation levels and testes length increased to a maximum of about 40% of controls. 80% of males were infertile in three matings over 250 days. In prepubertal and pubertal female rats a single immunisation at day 0 reduced estradiol to low levels by day 60 which remained low until termination of the experiment on day 300. In matings of these females with fertile males on days 90, 120 and 250, 74% of prepubertal females were infertile and impressively, 100% (10/10) of pubertal females were infertile after a single immunisation on day 0. These findings set the scene for exploration of immunosterilisation of wild and domestic animals after a single immunisation.

Effects of a Recombinant Gonadotropin-Releasing Hormone Vaccine on Reproductive Function in Adult Male ICR Mice

Gonadotropin-releasing hormone (GnRH) regulates the reproductive endocrine system in mammals. The GnRH immunocontraception vaccine can aid animal population control and management. We evaluated a recombinant GnRH fusion protein with the adjuvant MONTANIDE ISA 206 VG as a GnRH vaccine in adult male ICR mice by evaluating anti-GnRH antibodies; concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone; testis size and histomorphology; and semen quality. Response was assessed after intramuscular administration of the vaccine to mice in weeks 0, 4, and 8. The vaccine induced specific antibody response by week 5, with peak of antibody levels observed by week 13 and a declining level thereafter until the end of the study at week 24. Furthermore, it reduced serum FSH, LH, and testosterone concentrations. The vaccinated mice exhibited testicular atrophy and reduced sperm quality, concentration, morphology, and viability compared to control males. The outcomes of pairings of treated males with untreated females revealed reduced mating, pregnancy rates and number of litters compared to control pairings. Assessment of this GnRH vaccine in different species could assist its development for future applications.

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.

Combination immunotherapy with Survivin and luteinizing hormone-releasing hormone fusion protein in murine breast cancer model

AIM

To investigate the therapeutic potential of two recombinant proteins, Survivin and luteinizing hormone-releasing hormone (LHRH) fusion protein [LHRH(6leu)-LTB] for immunotherapy of breast cancer.

METHODS

Murine 4T-1 breast cancer model was used to evaluate the efficacy of recombinant proteins in vivo. Twenty four Balb/c mice were divided into 4 groups of 6 mice each. Recombinant Survivin and LHRH fusion protein, alone or in combination, were administered along with immunomodulator Mycobacterium indicus pranii (MIP) in Balb/c mice. Unimmunized or control group mice were administered with phosphate buffer saline. Each group was then challenged with syngeneic 4T-1 cells to induce the growth of breast tumor. Tumor growth was monitored to evaluate the efficacy of immune-response in preventing the growth of cancer cells.

RESULTS

Preventive immunization with 20 µg recombinant Survivin and MIP was effective in suppressing growth of 4T-1 mouse model of breast cancer (P = 0.04) but 50 µg dose was ineffective in suppressing tumor growth. However, combination of Survivin and LHRH fusion protein was more effective in suppressing tumor growth (P = 0.02) as well as metastasis in vivo in comparison to LHRH fusion protein as vaccine antigen alone.

CONCLUSION

Recombinant Survivin and MIP suppress tumor growth significantly. Combining LHRH fusion protein with Survivin and MIP enhances tumor suppressive effects marginally which provides evidence for recombinant Survivin and LHRH fusion protein as candidates for translating the combination cancer immunotherapy approaches.

Prophylactic herpes simplex virus type 2 vaccine adjuvanted with a universal CD4 T cell helper peptide induces long-term protective immunity against lethal challenge in mice

Induction of robust and long-term immune responses at the portal of entry remains a big challenge for HSV-2 vaccine development. The adoption of a CD4 T cell helper peptide in the vaccine is thought to be beneficial for the enhancement of immune responses, however, its effect on HSV-2 vaccines has not yet been studied. In this study, we designed a DNA vaccine (gD-TpD) simultaneously expressing HSV-2 gD ectodomain and a universal CD4 T cell helper peptide (TpD), and tested its efficacy on a murine model. Mice were immunized 3 times with gD-TpD or control DNA formulations, and then were rested until Day 150 when they were vaginally challenged with lethal doses of HSV-2. Our data showed that gD-TpD significantly increased gD-specific IgG and IgA in both sera and vaginal washes. Furthermore, the increased antibody responses showed enhanced neutralization activity in vitro. In addition, gD-TpD induced balanced Th1/2 cellular responses and CD8⁺ T cell-dependent CTL activity. Although immune responses dropped over time after the final immunization, robust and rapid antibody and T cell responses were induced upon virus challenge in gD-TpD group. Moreover, gD-TpD provided full protection against lethal viral challenge in immunized mice. Together, our findings indicate that the inclusion of the CD4 T cell helper peptide TpD in HSV-2 gD subunit vaccine could induce long-term protective immunity, providing information for a rational design of vaccines against HSV-2 or even other viruses.

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.

Gradual reduction of testosterone using a gonadotropin-releasing hormone vaccination delays castration resistance in a prostate cancer model

In a previous study aimed to design a novel prostate cancer vaccine, the authors of the present study demonstrated the advantage of combining the adjuvants Montanide ISA 51 with very small size proteoliposomes (VSSP) to promote a significant humoral immune response to gonadotropin-releasing hormone (GnRH) in healthy animals. The present study compared the efficacy of this vaccine formulation versus the standard treatment currently available in terms of preventing the development of tumors in DD/S mice injected with Shionogi carcinoma (SC) 115 cells. The results demonstrated that 5 non-vaccinated control mice exhibited a fast tumor growth, and succumbed to the disease within 19-31 days. Mice immunized with the GnRH/Montanide ISA 51/VSSP vaccine exhibited a moderate decline in testosterone levels that was associated with a decrease in anti-GnRH antibody titers, which lead to a sustained tumor growth inhibition. In total, 2 mice in the immunized group exhibited complete remission of the tumor for the duration of the present study. In addition, castrated mice, which were used as a control for standard hormonal therapy, exhibited an accelerated decrease in tumor size. However, tumor relapse was observed between days 50 and 54, and between days 65 and 85, following the injection of SC 155 cells. Therefore, these mice were sacrificed at day 90. The present study concludes that the slow and moderate reduction of testosterone levels observed using the GnRH-based vaccine may delay the appearance of castration resistance in a Shionogi prostate cancer model. These findings suggest that this vaccine may be used to delay castration resistance in patients with prostate cancer.

Parenteral administration of GnRH constructs and adjuvants: immune responses and effects on reproductive tissues of male mice

Two gonadotrophin releasing hormone (GnRH) constructs prepared by either chemical conjugation to keyhole limpet hemocyanin (GnRH-KLH) or as an expressed recombinant fusion protein (Multimer) were evaluated with or without adjuvants (immunostimulating complexes, ISCOMs, or cytosine-phosphate-guanosine oligodeoxynucleotides, CpG ODNs). After subcutaneous administration to Balb/c male mice at Weeks 0, 2 and 4, these preparations were assessed for induction of immune responses and effects on reproductive organs. GnRH-KLH plus ISCOMs formulation induced strong IgG immune responses from Week 4 through Week 12 resulting in consistent reproductive organ atrophy by Week 12 after subcutaneous administration. GnRH-KLH plus CpG ODNs generated immune responses but no atrophy of reproductive tissues by Week 12. Multimer plus ISCOMs induced poor immune responses and no effects on reproductive tissues by Week 12. In the absence of additional adjuvant, none of the GnRH constructs induced reproductive organ atrophy. GnRH-KLH induced stronger immune responses when formulated with ISCOMs or CpG ODN compared to Multimer. GnRH-KLH with ISCOMs could be an effective colloidal alternative for emulsion GnRH vaccine formulations.

Detection of antibodies against customized epitope: use of a coating antigen employing VEGF as fusion partner

Diagnosis of many infectious, autoimmune diseases and cancers depends on the detection of specific antibodies against peptide epitope by enzyme-linked immunosorbent assay (ELISA). However, small peptides are difficult to be coated on the plate surfaces. In this study, we selected GnRH as a model hapten to evaluate whether VEGF121 would be suitable as an irrelevant hapten-carrier to develop a universal platform for specific antibodies detection. Firstly, GnRH was fused to the C terminus of VEGF121 and the resultant fusion protein VEGF-GnRH expressed effectively as inclusion bodies in Escherichia coli. Thereafter, VEGF-GnRH was easily purified to near homogeneity with a yield of about 235 mg from 2.1 L induced culture. At last, VEGF-GnRH was used to perform ELISA and western blot, and our results suggested that VEGF-GnRH was capable of detecting anti-GnRH antibodies in sera both qualitatively and quantitatively. Indeed, previous studies of our laboratory had demonstrated that other fusion proteins such as VEGF-Aβ10, VEGF-GRP, VEGF-CETPC, and VEGF-βhCGCTP37 were able to detect their corresponding antibodies specifically. Therefore, VEGF121 may be a suitable irrelevant fusion partner of important diagnostic peptide markers. Our works would shed some light on the development of a universal platform for detection of specific antibodies.

Generation of a universal CD4 memory T cell recall peptide effective in humans, mice and non-human primates

CD4T cells play a key role in humoral immunity by providing help to B cells, enabling effective antibody class switching and affinity maturation. Some vaccines may generate a poor response due to a lack of effective MHC class II epitopes, resulting in ineffective helper T cell activation and recall and consequently poor humoral immunity. It may be beneficial to provide a CD4T cell helper peptide with a vaccine particularly in the case of a poorly immunogenic antigen. Such a T cell helper peptide must be promiscuous in its ability to bind a broad range of MHC class II alleles due to broad allelic variation in the human population. We designed a chimeric MHC class II peptide (TpD) with epitopes from tetanus toxoid and diphtheria toxoid, separated by an internal cathepsin cleavage site. TpD was capable of inducing a memory recall response in peripheral blood mononuclear cells from 20/20 human donors. T cells responding to TpD showed a central memory phenotype. Immunization of mice with a synthetic nicotine nanoparticle vaccine containing TpD showed that the peptide was required for robust antibody production and resulted in a long term CD4 memory T cell recall response. As a pre-clinical model two non-human primate species, rhesus macaques and cynomolgus monkeys, were immunized with a nicotine nanoparticle vaccine and evaluated for an anti-nicotine antibody response and TpD specific memory T cells. We found that 4/4 rhesus monkeys had both sustained antibody production and TpD memory T cells for the duration of the experiment (119 days). In addition 30/30 cynomolgus monkeys dosed with nicotine vaccine nanoparticles showed dose-dependent antibody generation and T cell recall response compared to saline injected controls. In summary we have developed a potent universal memory T cell helper peptide (TpD) that is active in vitro in human PBMCs and in vivo in mice and non-human primates.

Dendritic cell-directed vaccination with a lentivector encoding PSCA for prostate cancer in mice

Many studies have demonstrated that prostate stem cell antigen (PSCA) is an attractive target for immunotherapy based on its overexpression in prostate tumor tissue, especially in some metastatic tissues. In this study, we evaluated dendritic cell (DC)-directed lentiviral vector (DCLV) encoding murine PSCA (DCLV-PSCA) as a novel tumor vaccine for prostate cancer in mouse models. We showed that DCLV-PSCA could preferentially deliver the PSCA antigen gene to DC-SIGN-expressing 293T cells and bone marrow-derived DCs (BMDCs). Direct immunization with the DCLV-PSCA in male C57BL/6 mice elicited robust PSCA-responsive CD8⁺ and CD4⁺ T cells in vivo. In a transgenic adenocarcinoma mouse prostate cell line (TRAMP-C1) synergetic tumor model, we further demonstrated that DCLV-PSCA-vaccinated mice could be protected from lethal tumor challenge in a prophylactic model, whereas slower tumor growth was observed in a therapeutic model. This DCLV-PSCA vaccine also showed efficacy in inhibiting tumor metastases using a PSCA-expressing B16-F10 model. Taken together, these data suggest that DCLV is a potent vaccine carrier for PSCA in delivering anti-prostate cancer immunity.

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.