Prevention of mammary tumors with a chimeric HER-2 B-cell epitope peptide vaccine.

Synthetic peptide vaccines targeting B-cell epitopes of the extracellular domain of the HER-2 oncoprotein were evaluated for their capacity to elicit HER-2-specific antibodies with antiproliferative activity. Several HER-2 B-cell epitopes were identified by computer-aided analysis of protein antigenicity, and selected B-cell epitopes were synthesized colinearly with a promiscuous T-helper epitope (208-302) derived from the measles virus fusion protein at either the NH2 or COOH terminus linked via a four-residue turn sequence (GPSL). In addition, one epitope sequence, 628-647, was mutated to optimize disulfide pairing to mimic the native HER-2 receptor. All of the four selected epitopes elicited high-titered antibodies in outbred rabbits with exceptionally high titers for MVF-HER-2(628-647). These antibodies were cross-reactive with the native HER-2 receptor. Antibodies elicited by MVF HER-2(628-647) inhibited proliferation of human HER-2-overexpressing breast cancer cells in vitro and caused their antibody-dependent cell-mediated cytotoxicity. Furthermore, immunization with MVF-HER-2(628-647) prevented the spontaneous development of HER-2/neu-overexpressing mammary tumors in 83% of transgenic mice. The engineered, chimeric peptide B-cell immunogen MVF-HER-2(628-647) may have applications in the prevention of HER-2-overexpressing cancers.

Human chorionic gonadotropin as a target for cancer vaccines.

Human chorionic gonadotropin (hCG) is expressed by common cancers and may play a role in cell transformation as well as angiogenic, metastatic, and immune escape phenomena that are central to cancer progression. Clinical trials with a vaccine targeting the carboxy-terminal peptide of -hCG have indicated that tolerance to this oncofetal antigen can be broken. Humoral responses that may modulate the biologic activity of tumor-associated hCG as well as cellular responses to hCG have been generated. Studies are in progress to further define the biologic significance of hCG in cancer and to develop a vaccine approach that will best target this expression.

The role of carboxy-terminal portion of beta subunit of human chorionic gonadotropin in human immunodeficiency virus infection.

Human chorionic gonadotropin (hCG) and the beta subunit of this dimer glycoprotein hormone (beta hCG) have been reported by us to inhibit HIV replication. In order to identify the active site responsible for the antiviral activity, twelve overlapping peptides spanning across beta hCG were examined for their effect against HIV-caused cell death. Although the NH2-terminus of beta hCG appeared to contribute to activity, the core region was biologically inert. The most potent activity was observed with the fragment representing the carboxy-terminus of beta hCG. The dose response curve to serial dilutions of the peptide, containing amino acid residues 106-145, had a bell-shaped appearance - characteristic of hCG and beta hCG. The peak of activity corresponded to 100 ng/ml - the dose at which two thirds of virus-exposed MT-4 T lymphocytes survived. None of the tested peptides were toxic to MT-4. While the mechanism of action remains unclear, the results suggest that the COOH-terminal portion, unique to beta hCG, confers anti-HIV activity.

Effects of a beta-human chorionic gonadotropin subunit immunogen administered in aqueous solution with a novel nonionic block copolymer adjuvant in patients with advanced cancer.

The clinical and immunological effects of a vaccine consisting of CTP37, a synthetic peptide corresponding to the COOH-terminal peptide (CTP) of beta-human chorionic gonadotropin (beta-hCG) conjugated to diphtheria toxoid, combined with CRL 1005, a novel synthetic nonionic block copolymer adjuvant, were examined. Twenty-one patients with metastatic, nontrophoblastic cancers received up to four immunizations by i.m. injection of a fixed dose of CTP37 and escalating doses of CRL 1005. Doses of CRL 1005 adjuvant as high as 75 mg were administered with 1 mg of CTP37 without evidence of significant local or systemic toxicity. Immunizations resulted in the production of IgG antibody to beta-hCG. CRL 1005 doses of 3-25 mg appeared to be optimal for antibody induction. Immunizations also resulted in increases in the cellular response of peripheral blood mononuclear cells (PBMCs) to the unconjugated CTP, hCG, and diphtheria toxoid. Responding PBMCs specifically secreted the TH1-associated cytokines IFN-gamma and interleukin (IL)-2 as well as the TH2-associated IL-5 and IL-10. Increased expression of IFN gamma and IL-5 mRNAs by PBMCs 4 h after immunization was also observed. CRL 1005 administered with CTP37 in aqueous solution is well tolerated. The CTP37-CRL 1005 subunit vaccine has the capacity to stimulate potentially beneficial humoral and cellular immune responses in patients with advanced cancer.

Some reproductive studies in the baboon.

A captive colony of baboons has been used for three decades for various reproductive studies where application of findings to human therapeutics was desired. The characteristics of the menstrual cycle in baboons are very similar to those of women, except that of the baboon is slightly longer and there is a lower luteal phase concentration of oestradiol. The duration of pregnancy in baboons is about two-thirds that of humans but patterns of oestrogen and progesterone secretion are virtually identical. The principal oestrogen produced by the pregnant baboon is oestrone, while oestriol is the most abundant in human pregnancies. Chorionic gonadotrophin (CG) is elevated significantly only in the first trimester of a baboon pregnancy, while human pregnancy concentrations of this hormone are about one-third of the first trimester level in the second and third trimesters. Breeding success of baboons in captivity depends on care being taken to cull infertile animals from the colony prior to commencing matings. Under optimal conditions, fertility rates can reach nearly 80%. Female baboons have been successfully used to gain insights into antifertility effects of contraceptive vaccines directed against CG, spermatozoa and ovum antigens. Extensive use of the colony for developing a human chorionic gonadotrophin (HCG) antifertility vaccine has been invaluable for progress in this field. Other pharmaceuticals and devices have been successfully tested in baboons, but costs and mandated regulations for the management of these nonhuman primates have made their current use in meaningful studies extremely difficult.

Immune recognition of genetically diverse simian T-cell lymphotropic virus type I isolates.

Nucleotide sequence analysis of selected regions of the gag, pol, env and pX genes of simian T-cell lymphotropic virus type I (STLV-I) strains indicated that African isolates were more closely related to human T-cell lymphotropic virus type I (HTLV-I) than Asian isolates. Despite these recent comparative studies on nucleotide sequence homology between HTLV-I and STLV-I isolates, only limited information is available regarding the influence of genetic differences on antigen-antibody recognition of distinct STLV-I strains. In this study, we demonstrated that sera from STLV-I-infected yellow baboons (Papio cynocephalus) reacted strongly with env gp62/68 from HTLV-I-infected cell lines MT-2 and C10/MJ. In contrast, sera from Japanese macaques (Macaca fuscata) naturally infected with Asian STLV-I had weak reactivity to env gp62/68 of these prototypic HTLV-I strains. Pst-1 restriction enzyme analysis of proviral DNA indicated that the baboon virus isolates were more closely related to HTLV-I than the Japanese isolates. These results indicate that nucleotide sequence diversity, correlates with variations in proviral restriction enzyme sites and antibody recognition of viral envelope proteins. These differences in immunoreactivity may have important implications for serologic diagnosis, as well as epidemiological and vaccine studies of STLV-I infection.

Sexual transmission of simian T-lymphotropic virus type I: a model of human T-lymphotropic virus type I infection.

Simian T-lymphotropic virus type-I (STLV-I) seronegative females placed together with seropositive males for breeding purposes were followed from 1984-1990 to determined seroconversion rates by enzyme immunoassay and western immunoblot analysis. Two of 26 females and 1 of 4 males previously negative for antibodies to STLV-I seroconverted during the study period. Statistical analysis of sexual encounters indicated that the probability of a seronegative female testing positive for STLV-I after a sexual encounter with a seropositive male is less than 4%. These data indicate that even though sexual contact is important in the transmission of STLV-I, it may not be an efficient mode of viral infection. These data also suggest that female-to-male transmission of STLV-I occurs, as recently reported for human T-lymphotropic virus type-I (HTLV-I) infection. These results are important because HTLV-I and STLV-I share many features in common including routes of viral transmission. In addition, the difficulty of clearly quantitating the risk of sexual transmission in humans makes the primate animal model a valuable alternative to study the human infection.

Birth control vaccines and immunological approaches to the therapy of noninfectious diseases.

Vaccination usually means the immunization of persons or animals against foreign infectious organisms for disease prevention. However, it has now been demonstrated that immunization against certain self substances to which tolerance normally exists can elicit beneficial effects to humans and other animals without inducing autoimmune disease. Clinical trials in women have been conducted with vaccines against reproductive antigens for the prevention of pregnancy and research is under way to develop more advanced formulations. Other self antigens have been described that might be used for developing methods of immunological therapy for such diseases as cancer, ulcers, and complications of diabetes. Emphasis is placed on the need for careful studies in appropriate animal models before any clinical application of such procedures is suggested.

PIP: By deliberately upsetting the body's recognition of self, and inducing an immune response against specific self antigens, birth control vaccines and disease therapies may be possible. The vaccine must be highly specific, the antigen must be present in small amounts or at limited times, and the benefit-to-risk ratio must be thoroughly evaluated. Target antigens being considered for birth control vaccines include sperm antigens or enzymes, zona pellucida of the ova and the pituitary hormone hCG. Anti-sperm immunity has been observed naturally occurring, and induced experimentally. Anti-ovum vaccines have the drawback of possibly reacting with ovarian tissue. The gonadotropin hormone receiving the most attention is hCG, or specifically its carboxy-terminal subunit. The rest of the peptide is too similar to hLH. Anti-hCG could act by preventing the luteotrophic effect of the hormone, or by attacking the hCG-producing cells of the blastocyst. Vaccines based on hCG with a tetanus toxoid carrier and a synthetic hCG peptide vaccine have been tested successfully in Phase 1 clinical trials. Other therapies based on immunization against self antigens include anticancer therapy, excess growth hormone and the Zollinger- Ellison syndrome of gastric ulcer disease. All of these approaches need to be monitored carefully to ensure that no damage is done to the host from circulating immune complexes.

Use of a synthetic peptide adjuvant for the immunization of baboons with denatured and deglycosylated pig zona pellucida glycoproteins.

Baboons were immunized using a synthetic peptide adjuvant with two purified pig zona pellucida glycoproteins. The major zona pellucida glycoprotein (ZPI) was purified by preparative isoelectric focusing, and the 80 K deglycosylated zona pellucida protein (ZPIII) was purified by preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis. The immunogenicity as well as the antigenicity of these proteins were evaluated by characterizing antibodies using the enzyme-linked immunoassay and by immunoblotting of zona pellucida proteins separated by high-resolution two-dimensional polyacrylamide gel electrophoresis. Both groups of animals developed antibodies that recognize the major zona pellucida glycoprotein, (ZPI) and immunoblotting procedures provide evidence that two of the major porcine zona pellucida glycoprotein families (ZPI and ZPIII) contain shared antigenic determinants. The animals immunized with ZPI showed decreased levels of estrogen throughout their menstrual cycles, and two of the animals ceased ovulation. All animals in the group immunized with ZPIII had a significant reduction in the numbers of antral follicles as compared with control animals. Although ovarian cyclicity was not altered significantly within a few months after immunization, two of the five animals in this group became amenorrheic by 8 months. Histologic analysis of ovarian tissue shows that follicles were absent or frequently abnormal in animals of both groups following long-term immunization. These studies demonstrate that the synthetic adjuvant is effective in inducing antibodies (to purified zona pellucida glycoproteins) that recognize antigenic determinants to either denatured or deglycosylated zona pellucida glycoproteins, and that some of these antibodies may interfere with normal ovarian function.

Phase I clinical trial of a World Health Organisation birth control vaccine.

A birth control vaccine incorporating a synthetic peptide antigen representing the aminoacid sequence 109-145 of the C-terminal region of the beta subunit of human chorionic gonadotropin (hCG-beta) was submitted to a phase 1 clinical trial. Thirty surgically sterilised female volunteers, divided into five equal groups for different vaccine doses, received two intramuscular injections six weeks apart. Over a six-month follow-up there were no important adverse reactions, and potentially contraceptive levels of antibodies to hCG developed in all subjects. In the highest vaccine dose group, the results gave promise of a contraceptive effect of six months' duration.

PIP: A Phase I clinical trial of the immunogenicity and safety of a vaccine against the C-terminal region of the beta subunit of human chorionic gonadotropin (hCG-B) demonstrated a dose-related immune response. The antigen was a synthetic peptide of the C 109-145 region of hCG-B, conjugated to diphtheria toxoid, and administered in a water-soluble synthetic adjuvant in a saline-oil emulsion. This vaccine had been previously tested for toxicity in laboratory animals and for immunogenicity, safety and contraceptive effectiveness in baboons. 30 previously sterilized women were given 2 injections 6 weeks apart, ranging from 50 to 1000 mcg of the antigen. Each woman tested free of HLA B27 antigen and reacted negative to the diphtheria toxoid skin test. Based on calculated contraceptive antibody binding level of 0.52 nmol/l, all subjects mounted an effective antibody response for at least 6 months. 2 subjects in the group given 1000 mcg who were followed for 9 and 10 months maintained this level of antibody. 12 women showed an anamnestic response to diphtheria toxoid, while 8 did not. The only adverse reactions were mild, transient pain at the injection site. Several women who received unstable adjuvant experienced more severe myalgia. Menstrual changes appeared in 5 subjects: early menopause in 1, spotting in 3 and menorrhagia in 1 woman. Only transient positive findings were seen in some sera screened for autoantibodies. This preliminary trial indicates that anti-hCG vaccine is a hopeful reversible contraceptive.

Desensitization of both luteal and pituitary function in baboons with nafarelin, a potent LH-RH agonist.

Acute responsiveness in vivo of the baboon corpus luteum to a course of twice daily injections of human chorionic gonadotropin (hCG) has been studied with and without concomitant injections of nafarelin, a potent luteinizing hormone-releasing hormone (LH-RH) agonist. HCG injection alone caused an acute (1 hour) rise in circulating levels of progesterone (P), confirmed to be a direct effect at the luteal level, since no change in circulating levels of endogenous LH was detected. When hCG was coadministered with a low dose of nafarelin (50 micrograms per injection), circulating levels of LH rose, but the rise in serum P levels was blunted. However, when hCG was coadministered with a high dose of nafarelin (250 micrograms per injection), serum LH levels rose only in response to the first injection and serum levels of P were not elevated, suggesting a desensitization of the pituitary to the LH-RH agonist and of the corpus luteum to the hCG. The profile of luteal P during the luteal phase in response to combined treatment with hCG and nafarelin also reflected these effects, being intermediate between vehicle controls and hCG treatment alone. This first demonstration of a luteal desensitization to gonadotropin by an LH-RH agonist in primates may account for previously noted successful interception of pregnancy in baboons treated with these agents.

Effects of immunization against human choriogonadotropin on the growth of transplanted Lewis lung carcinoma and spontaneous mammary adenocarcinoma in mice.

We studied the effects of preimmunization with a synthetic carboxy-terminal peptide of the beta-subunit of human choriogonadotropin (hCG) conjugated to diphtheria toxoid on the growth of two tumor models, the transplantable Lewis lung carcinoma in C57BL/6J mice and the spontaneous mammary carcinoma in C3H/OuJ mice. Immunization with the conjugate prior to Lewis lung tumor implantation significantly (P less than 0.05) retarded the growth of tumors as measured by tumor weight 18 days following transplantation. The weights of Lewis lung tumors in animals preimmunized with the hCG immunogen were inversely correlated (r = 0.61) with the levels of circulating antibodies against human chorionic gonadotropin, whereas no statistical correlation was found between tumor weights and the levels of antibodies reactive to diphtheria toxoid. The number of conjugate-treated C3H/OuJ mice that developed mammary tumors was significantly (P less than 0.05) reduced compared to their vehicle-treated cohorts. Pretreatment with the synthetic muramyl dipeptide analog utilized as an adjuvant with both immunogens did not show any effect on the tumor growth in either tumor system.

Humoral response of normal and athymic (nude) mice to human choriogonadotropin immunogens.

The production of antibodies against human choriogonadotropin (hCG) was studied in normal and athymic (nu/nu) mice of two strains (C57/BL and Balb/c), injected with native (whole) hCG or an immunogen consisting of a synthetic hCG beta COOH-terminal peptide, residues 109-145, conjugated to diphtheria toxoid and mixed with a synthetic muramyl dipeptide analog (nor-MDP) as adjuvant. Both the short-term effect of native hCG dissolved in saline and injected IM (primary response), and the long-term effect of the native hCG and of the hCG immunogen dissolved in saline, emulsified in squalene-Arlacel A, and injected SC as a depot injection (secondary or memory response), were considered. The results obtained indicate that native hCG may be classified as a T-cell independent antigen in the sense that it can elicit low levels of IgM antibodies on a short term basis in athymic mice that have either no or very low T-cell levels. In long-term studies using hCG and the hCG immunogen no antibodies could be detected in athymic mice 14 days after a booster inoculation given 28 days after primary immunization, a regimen that produced high levels of antibodies in normal mice. Because of their inability to sustain humoral responses to native hCG as well as to other hCG immunogens, athymic mice seem well suited for in vivo studies of some of the biological effects of hCG.

The identification of peptide sequences of human chorionic gonadotropin containing a conformational epitope.

A series of overlapping peptides were synthesized representing the entire amino acid sequence of the beta-subunit of human chorionic gonadotropin (hCG) and these were reacted with a monoclonal antibody shown to be specific for hCG. One linear peptide (residues 40-52 of the sequence) reacted significantly with the monoclonal antibody but a conjugate of this peptide to diphtheria toxoid (DT) failed to elicit significant levels of antibodies reactive to hCG in rabbits. The subsequent preparation of an extended peptide (residues 38-57) in which the two cysteines were oxidized to form a loop peptide yielded a highly immunogenic antigen when conjugated to DT. Antibody levels reactive with hCG from loop peptide immunizations of rabbits exceeded those found after immunization with a 37 residue peptide representing the carboxyl terminus of the beta-hCG subunit. The antisera did not react with pituitary glycoprotein hormones with similar sequences.

Use of synthetic peptides as immunogens for developing a vaccine against human chorionic gonadotropin.

Human chorionic gonadotropin (hCG) is a glycoprotein hormone produced by the placental trophoblast soon after conception and is essential for successful gestation in women. A vaccine against this hormone has been developed for the purposes of birth control and the treatment of hormone-related diseases. Synthetic peptides representing the native primary structure of the hCG beta subunit have been coupled to protein carriers to produce immunogens. Several peptides, representing varying lengths from the C-terminus of the beta subunit, were synthesized and their ability to elicit antibodies reactive to hCG and able to neutralize hCG activity in vivo was tested. A peptide representing the 37 amino acids of the C-terminal end of the beta subunit was selected as the vaccine antigen and diphtheria toxoid was selected as the carrier for the first prototype vaccine. Procedures for coupling a specified number of peptide molecules to each carrier molecule in a reproducible fashion were developed. The immunogen is mixed with an adjuvant compound and the mixture administered in an oil-in-water emulsion. Significant levels of antibodies to hCG have been elicited in several species and a marked reduction in the fertility of immunized baboons has been observed. Extensive evaluations of vaccine safety have been conducted and Phase I clinical trials have been proposed to test its utility for human birth control. Possible applications of the hCG vaccine to health problems other than birth control are being considered.

Differentiation and secretory activities of cultured human placental cytotrophoblast.

Ultrastructural, autoradiographic, immunofluorescent and biochemical techniques were used to characterize primary cultures of term placental cytotrophoblast in order to gain insight into the differentiation and secretory capacities of the cellular component of human trophoblast. Trypsin treatment of placental villi allowed isolation of a predominantly cytotrophoblast cell population that maintained viability up to 13 weeks in monolayer culture. Autoradiographic studies of tritiated thymidine incorporation identified a smaller diameter mononucleated cell population that was mitotically active and developed into larger diameter mononucleated cells and into multinucleated cells during culture. Ultrastructurally, cultured cells formed desmosomes, had an extensive network of cytoplasmic microfilaments and contained the organelles for hormone synthesis and secretion. These cells secreted steroid hormones, secreted Schwangerschafts protein I, actively incorporated tritiated glycoprotein precursors and expressed surface immunoreactivity for the beta-subunit of human chorionic gonadotrophin (hCG). However, medium concentrations of hCG and human placental lactogen dropped rapidly to undetectable levels after 14 days in primary culture. Cells grown beyond confluence differentiated into 1 to 2 mm structures with a villus-like histology. Our studies indicate that cytotrophoblast can secrete steroids, cytotrophoblast differentiation occurs in vitro in the absence of maternal tissues, hCG synthesis occurs in cultured cytotrophoblast and medium concentrations of placental protein hormones are not the best indicators of cell viability for cultures of cytotrophoblast.

Antibody reactivity against trophoblast and trophoblast products.

Sensitive immunoassays have been applied to WHO reference bank sera from fertile and infertile women in order to assess any naturally occurring antibody reactive with isolated human placental trophoblast membranes or two separate trophoblast protein products (hCG and SP1). A very low incidence of antibody reactive with solubilised trophoblast membrane was detected, and no significant antibody to either hCG or SP1 could be detected. Infertile states represented within this serum bank appear unlikely to involve adverse immune reactions to trophoblast.

Non-cross-reactive monoclonal antibodies to human chorionic gonadotropin generated after immunization with a synthetic peptide.

Noncross-reactive monoclonal antibodies specific for human chorionic gonadotropin (hCG) were obtained after pre-selection for submolecular specificity with a synthetic peptide immunogen. Mice were immunized with a synthetic peptide representing a segment unique to the beta-subunit of hCG (amino acid residues 109-145), conjugated to diphtheria toxoid. We then derived nine different hybridomas that secreted monoclonal antibodies reactive with both native hCG and isolated C-terminal peptide, after somatic cell hybridization of immune spleen cells with a nonsecretory myeloma cell line. None of the nine monoclonal antibodies, termed beta-hCG-CTPa1----a9, reacted with hLH, hFSH, or hTSH, although these pituitary hormones display extensive amino acid sequence homology with hCG. The noncross-reactive anti-beta-hCG monoclonal antibodies show apparent association constants on the order of 10(9) to 10(10) M-1. A sandwich-type enzyme-linked immunosorbent assay was set up with cut-off values of around 5 mIU/ml. These antibodies might have important implications for: a) improving the diagnosis and clinical management of pregnancy; b) monitoring the course of development of carcinomas which secrete the hormone, through in vitro assays or in vivo radioimmunodetection; c) evaluating the antibodies' therapeutic potential against such carcinomas; d) studying the biologic functions of the C-terminal segment of beta-hCG; and e) addressing the anti-fertility effect of antibodies raised against that segment.

Levels of adrenal and gonadal hormones in rhesus monkeys during chronic hypokinesia.

The purpose of this study was to evaluate the effect of chronic immobilization on the hypophysial-adrenal and hypophysial-gonadal axes of adult male rhesus monkeys and the effect such manipulation has on the ability of these axes to respond to exogenous corticotropin, gonadotropin, and GnRH administration. A comparison was also made of the effects of immobilization on testosterone secretion at periods of low (April) and high (November) gonadal activity in this animal. Adult male rhesus monkeys were immobilized in a horizontal position for periods of up to 20 days during March/April. The function of the hypophysial-adrenal and hypophysial-gonadal axes was studied by monitoring plasma levels of cortisol, 17-hydroxylated precursors, 11 deoxycortisol, and testosterone during the period of restraint. Groups of immobilized and control animals also received iv injections of ACTH, FSH, and LH or LHRH on day 18 of the experiment. An additional group of animals was immobilized for 20 days, but did not receive exogenous hormone treatment. This group was used for comparison of seasonal differences in testosterone secretion with another group of animals subjected to the same treatment in November. During the first 3 h of immobilization, levels of cortisol, 17-hydroxylated precursors, and 11-deoxycortisol increased markedly from initial levels. Cortisol levels remained elevated for 3 days, whereas levels of the other three adrenal hormones declined to near-initial levels within 24 h. Testosterone levels declined steadily during the first 6 h of immobilization in males studied at a time of high testicular activity (November), while an increase during the first hour of restraint followed by a decline during the next 3 days were observed in males studied during a period of low testicular activity (April). Animals injected with ACTH on day 18 of immobilization had cortisol levels similar to those of control animals, but other groups of animals restrained for a similar period exhibited a lower level of plasma testosterone than controls after the injection of FSH and LH or LHRH. These data suggest that adaptation to stress results in a reduced demand for corticosteroid production and that the adrenals of chronically stressed animals are capable of responding to exogenous corticotropin, or alternatively, the immobilization imposed was stressful for only a limited time, and after a few days, animals no longer reacted as in response to stress. Also, secretion of testosterone in male monkeys is markedly influenced by the functional state of the gonads at the time of stress initiation.