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Clinical and Experimental Immunology. 1978 Aug; 33(2):360-375.Since guidelines for safety evaluation of antifertility vaccines do not exist, this WHO report attempts to define the parameters to be examined and the methodology which might be used for such a safety assessment. In principle, antifertility vaccines may: 1) prevent sperm transport and/or fertilization; 2) prevent or disrupt implantation; and 3) prevent blastocyst development. Potential advantages of this immunological approach to fertility regulation include: 1) possibility of infrequent administration, possibly by paramedicals; 2) use of antigens or antigen frangments that are not pharmacologically active; and 3) the possibility of large-scale synthesis and manufacture of vaccine at relatively low cost in the case of antigens of known chemical structure. To evaluate the efficacy and safety of placental antigen vaccines, placental antigens used should not possess significant immunological similarity with tissue other than placenta. Carriers or haptens may require structural remodifications of placental molecules to overcome natural immunological tolerance. Adjuvants may be needed to enhance the immune response required. Quality-control procedures for vaccine component production include tests for: 1) purity; 2) toxicity; 3) sterility; and 4) shelf-life. Acute, subacute, and chronic toxicity testing in animals is described for it must be performed separately for the haptenated antigen or conjugate and adjuvant. Such tests would include hematological parameters, blood chemistry, urinanaylsis, gross pathological and organ weight analysis, and ophthalmological tests. Animal models are suggested. Means of monitoring the immune reponse and potential hazards of immunization (e.g., allergy or autoimmune disease) are discussed. The rationale and protocol for safety and efficacy studies of human chorionic gonadotropin-peptide vaccine receive similar attention, with emphasis on tests to be performed before human clinical trials can start.
Geneva, Switzerland, WHO, 1965. 19 p. (WHO Technical Report Series No. 304)This WHO technical report focuses on the 1) psychosomatic factors in human reproduction; 2) hypothalamo-hypophyseal system; 3) mechanism of sexual rhythm; 4) nervous influences on the hypothalamus; 5) hormonal influences on the hypothalamus; 6) neuroendocrine aspects of sexual behavior; and 7) effects of drugs on reproduction. After summarizing current research status on the above-mentioned topics, the following research needs are suggested: 1) assays of individual human endogenous gonadotropins, suitable for clinical application; 2) autoradiography, fluorescent-antibody, spectrophometric interference and histochemical and biochemical techniques for studying cells that supply axons to the primary capillary plexus of the hypophyseal portal system and for studying effects of different hormonal status on hypothalmic structure and function; 3) computer techniques for evaluating electrophysiological data; 4) improved lesioning techniques; 5) comparative studies of reproductive activity patterns, exteroceptive factors, neuroendocrine factors in sexual and related social behavior, and long-term or delayed effects of drugs administered during gestation on subsequent sexual development; 6) studies of synaptic connections of hypothalamic neurones; 7) studies of endogenous gonadal and gonadotropin production in prepuberal animals; 8) functional significance of regional distribution of hypophyseal portal system; 9) mechanisms involved in selective uptake of labeled hormones; 10) hypothalamic lesions in species with spontaneous ovulation and active luteal function; 11) direct effect of gonadal hormones on single hypothalamic neurones studied with combination of microinjection and unit recording devices; 12) studies of the possibility of a direct feedback of gonadotropic hormones on the hypothalamus; 13) studies of the receptor mechanisms involved in neuroendocrine reflexes; 14) wider exploration of brain structures, with regard to feedback action of gonadal hormones; 15) studies of pineal function; 16) further investigation of a possible role of the peripheral autonomic pathways in reproductive processes; and 17) research on the application of tissue culture techniques for studying problems of the origin and metabolic effects of neurohormonal mediators and the biochemcial and morphological changes induced by sex hormones.
NETWORK. 1992 Aug; 13(1):20-3.Researchers are pursuing 2 approaches to developing a male contraceptive drug. 1 approach centers around suppression of sperm production the other around blocking conception. Researchers are looking at introducing hormonal contraceptives into men's bodies via injections or implants to stop sperm production. Both forms of these possible male contraceptives will not be available for many years, however. A WHO study on testosterone enanthate of men in 7 countries reveals total suppression of sperm production occurred in almost all the Asian men, but only about 60% suppression occurred in other ethnic groups. A current WHO study is examining whether a hormonal contraceptive which is not 100% effective can be useful if it would be more effective than barrier methods. The Population Council is conducting research on 2 capsule implants with 1 capsule releasing luteinizing hormone releasing hormone 13 to halt sperm production while the other releases an androgen to maintain sex drive. Animal tests indicate complete contraception with no side effects. The other possible means of suppressing sperm production is administration of a cottonseed oil extract called gossypol which appears to stop sperm production thereby eliminating the need for concurrent androgen administration. Yet it does cause potassium depletion in some men which can result in arrhythmias. An antifertility vaccine comprises the 2nd approach. Several US researchers are exploring an antifertility vaccine to produce antibodies only to the specialized sperm surface needed to attach to the egg. The 1st antifertility vaccine would probably be in pill form and a woman's contraceptive since it is earlier to target the smaller number of sperm in the oviduct than in the testes.
CONTRACEPTION. 1992 Aug; 46(2):103-4.WHO formed its Task Force on Methods for the Regulation of Male Fertility in 1972. Its charge is developing safe, effective, reversible, and affordable contraceptive methods for developing countries. The research focus is on suppression of sperm production. The research strategy consists of 3 parts: suppression of secretion of the pituitary gonadotropin hormones, recouping circulating androgen to physiological levels without prompting spermatogenesis, and determining the functional ability of residual sperm if treatment does not bring about azoospermia in all cases. A task Force study reveals that men of various ethnic groups respond to testosterone contraceptives differently. Other clinical research involved an androgen with a progestogen such as DMPA. Since steroids are basically inexpensive to produce they may prove to be beneficial and affordable to national family planning programs in developing countries. Gonadotropin releasing hormone (GnRH) antagonists proved to be relatively effective in suppressing gonadotropins and sperm production in animals. Scientists working on developing GnRH antagonists should strive to formulate a reversible contraceptive with no side effects which requires limited injections. The Task Force carried out a study in bonnet monkeys with the GnRH agonist buserelin in which buserelin suppressed spermatogenesis for 3 years and, after treatment, testicular function was entirely restored. Subsequent mating trials indicated they were fertile. The Task Force planned to follow the study with a GnRH antagonist. The 1st international gathering on GnRH analogues in China served to bring together scientists the world over to meet and to collaborate in developing new drugs for contraceptive use.