G.P. Talwar

The HSD-hCG vaccine prevents pregnancy in women: feasibility study of a reversible safe contraceptive vaccine

PROBLEM: To develop a vaccine for reversible control of fertility in women.

Important Role of the Carrier in the Induction of Antibody Response Without Freund's Complete Adjuvant Against a “Self” Peptide Luteinizing Hormone-Releasing Hormone (LHRH)*

ABSTRACT: Antibody response to the decapeptide luteinizing hormone‐releasing hormone (LHRH) was induced in mice without use of Freunds complete adjuvant. The conventionally employed conjugates of LHRH with bovine serum albumin were poor immunogens and required potent adjuvants. In contrast, LHRH linked covalently to tetanus toxoid or keyhole limpet hemocyanin‐generated antibodies with alum as adjuvant. Methods are described for preparation of LHRH conjugates with these carrier proteins with defined molar composition.

Bioneutralization Capacity of the Antibodies Generated in Women by the Beta Subunit of Human Chorionic Gonadotropin (βhCG) and βhCG Associated with the Alpha Subunit of Ovine Luteinizing Hormone Linked to Carriers

ABSTRACT: Data is presented on the bioneutralization capacity per unit immunoactivity of 30 serum samples of women immunized with the β‐sub‐unit of human chorionic gonadotropin (β‐hCG) or βhCG associated noncovalently with the α‐sub‐unit of ovine luteinizing hormone (α‐oLH), to form a heterospecies dimer (HSD), which were linked to carriers. The bioassays utilized were inhibition of radioiodinated hCG binding to rat testicular receptors in vitro and the inhibition of hCG induced testosterone production in mice. In both assays, antisera of women immunized with the HSD had a bioactivity to immunoactivity ratio that was about 25% higher, on an average, than antisera of women immunized with β‐hCG, suggesting a better bioneutralization capacity of sera raised by the HSD in women.

Formulation of a transdermal system for biphasic delivery of testosterone

Films cast from an isopropanol solution containing testosterone (T1) and different amounts of a blend of poly(vinyl pyrrolidone) and poly(vinyl alcohol) show differences in morphology as well as the rate of release of T1. Based on these observations, a formulation was standardized for transdermal administration of T1. The formulation was designed to deposit a film having sufficient tack to adhere to the skin surface, as well as to entrap a part of the T1 content. Physical properties, drug content and stability of such films were evaluated. In vitro skin permeation of T1 after applying the formulation was studied in depilated, excised rat skin using a flow-through cell. Large amounts of T1 were found to diffuse through the skin immediately after application and at slower rates after the burst release was resolved. Such a formulation may be expected to provide two distinct peaks of the hormone after application. Formulation variables and their effect on in vitro drug release are discussed.

Recent developments in immunocontraception

The possibility of controlling fertility by antibodies inactivating key reproductive hormones has been amply demonstrated by active and passive immunization in primates. Four birth control vaccines directed against human chorionic gonadotropin are currently in early clinical trials. The nature of these vaccines and the underlying principles are described, as are the available results from clinical studies. The alpha- and beta-subunits of human chorionic gonadotropin and the ovine gonadotropins have been cloned by recombinant deoxyribonucleic acid methods. A new breed of vaccines that combines the genes of gonadotropins linked to hepatitis B surface protein has been developed. The next generation of birth control vaccines is likely to be polyvalent and to have the ability to intercept fertility at more than one point. A number of monoclonal antibodies against human sperm have shown the presence of tissue-specific antigens and the possibility of preventing the fertilization of the egg. Inclusion of more than one carrier in the vaccine increases the percentage of high responders and accords immunoprophylactic benefits against more than one disease. Conjugates have also been developed to obtain high titers of antibodies against gonadotropin-releasing hormone with permissible adjuvants. This vaccine may have therapeutic applications in hormone-dependent cancers and precocious puberty.

Birth Control Vaccines Inducing Antibodies Against Chorionic Gonadotropin

The possibility of inducing antibodies against reproductive tract antigens by deliberate immunization was indicated as early as 1899 by the pioneering work of Landsteiner (14) and Metchinikoff (15). These leaders of immunology did obtain antisera toxic to sperm. However, the practical utility of this lead for control of fertility could not materialize owing to several factors. Crude tissue extracts induced antibodies reactive to unwanted tissues with potential toxicity hazards. Not enough was known of the immune processes and the manner in which these could be modulated to advantage. Furthermore, for antigens localized on sperm, it would be necessary to ensure the right type of immune reactions in the genital tract for preventing fertilization; antibodies in systemic circulation alone may not suffice.

Efficacy of a Recombinant Chimeric Anti‐hCG Antibody to Prevent Human Cytotrophoblasts Fusion and Block Progesterone Synthesis

A recombinant chimeric antibody against hCG (cPIPP) has been engineered and expressed at high yield in plants. The purpose of this work was to enquire whether this antibody is competent to neutralize the bioactivity of hCG on human trophoblasts.

IMPROVED IMMUNOGENIC FORMULATIONS FOR ANTIGONADOTROPIN RESPONSE

Effective control of fertility by immunization with beta-hCG has been demonstrated in non-human primates (Stevens, 1974;Hearn, 1976; Tandon et al., 1981, 1984) and rats (Hulme et al., 1980). A vaccine consisting of beta subunit of hCG conjugated with tetanus toxoid (TT) was proposed earlier (Talwar et al., 1974, 1976). This vaccine induced antibodies to both hCG and TT and thus provided additional immunoprophylactic benefit against tetanus. After initial animal experiments and toxicology studies, Phase I clinical trials were conducted with this vaccine in 63 women of reproductive age in six centres located in five countries. AntihCG antibodies were formed in 61 out of 63 recepients without any significant side effects and disturbances (Kumar et al., 1976, Hingorani and Kumar, 1979; Shahani et al., 1979, 1982;Nash et al., 1980). The response was reversible with a duration of 300 to 500 days in good responders. The main limitation of this vaccine was the variability of the antibody response from individual to individual and those with inadequate titres were not protected from pregnancy. This presentation will describe an improved formulation which can generate higher antibody titres in a larger percentage of the recepients.

Characterization of Antibodies to a Placenta‐Specific Antigen Cross‐Reacting With a Choriocarcinoma Cell Line

ABSTRACT: Antibodies were raised in rabbits to purified human term placental villous plasma membrane. These were cytotoxic to human peripheral blood lymphocytes and manifested cross‐reactivity to kidney and liver. After absorption with these tissues, reactivity was retained with placental villous plasma membrane. The placental‐specific antiserum was fully reactive with BeWo choriocarcinoma cells, but was devoid of reaction with a human myeloma tumor cell line (GM2132). The antibodies were cytotoxic to BeWo in the presence of complement, as determined by trypan blue uptake, 51Cr release, and inhibition of uptake of 3H‐thymidine.