Characterization of antigens expressed in normal baboon trophoblast and cross-reactive with HIV/SIV antibodies.

Electron microscopic studies have revealed the presence of endogenous retroviral (ERV) particles in normal primate placental tissues. These particles have ultrastructural similarities to type C retroviral particles and are mainly associated with the trophoblast. In normal human placental tissues, they have antigenic similarity with exogenous retroviruses, such as the human immunodeficiency virus (HIV), and may have a role to play in the regulation of cellular gene expression, syncytiotrophoblast formation or pregnancy-related immunosuppression. In this study, a panel of antibodies (polyclonal and monoclonal antibodies) against viral proteins (anti-HIV and anti-SIV) and endogenous retroviral (ERV) proteins were assessed by immunohistochemistry and immunoblotting, for their cross-reactivity with ERV particles isolated from normal baboon placental tissues. The antibodies (anti-HERV-K RT, anti-ERV3 env, anti-HIV-1 p17, anti-HIV-2 gp120) reacted positively with the syncytiotrophoblast and each antibody recognized one or two proteins of molecular weights (MW) 38, 58 or 64 kDa present in the baboon placental villous tissues and SIV-infected molt-4 Cl8 cells, but not in uninfected cells. The results of this study confirm the specific expression of retroviral cross-reactive antigens in normal baboon placental tissues and suggest placental cellular proteins may have antigenic similarity with those recognized by anti-HIV/SIV antibodies. The role of these retroviral-related proteins expressed at the maternal-fetal interface remain unclear.

Ancistrobertsonine A and related naphthylisoquinoline alkaloids from Ancistrocladus robertsoniorum.

From the as yet unexplored East African Liana, Ancistrocladus robertsoniorum, several naphthylisoquinoline alkaloids have been isolated, based mainly on High Speed Countercurrent Chromatography (HSCCC). The structure of the new compound, ancistrobertsonine A, was elucidated by chemical and spectroscopic methods. Furthermore, the known alkaloids ancistrocladine, its atropo-diastereomer, hamatine, and its regioisomer, ancistrobrevine B, were isolated.

Retarded development of exoerythrocytic stages of the rodent malaria parasite Plasmodium berghei in human hepatoma cells by extracts from Dioncophyllaceae and Ancistrocladaceae species.

Retarded development of exoerythrocytic stages of the rodent malaria parasite Plasmodium berghei in human hepatoma cells by extracts from Dioncophyllaceae and Ancistrocladaceae species. International Journal for Parasitology 27: 29-32. Naphthylisoquinoline alkaloid-containing extracts (10 micrograms ml-1) of species belonging to the Dioncophyllaceae and the Ancistrocladaceae, 2 small tropical plant families, display pronounced in vitro activities against exoerythrocytic stages of Plasmodium berghei (Anka), developing in human hepatoma cells (Hep G2). The highest activities were obtained with CH2Cl2 root and bark extracts, and a CH2Cl2/NH3 leaf extract from Triphyophyllum peltatum, a CH2Cl2/NH3 root extract from Ancistrocladus abbreviatus, and a CH2Cl2 leaf extract from A. tectorius. The degrees of growth inhibition ranged within 27.7-70.0%. The commercially available drug primaquine diphosphate (25 micrograms ml-1) caused a comparable effect (62.1%) in the same test system.

Anti-sperm and anti-ovum vaccines: the selection of candidate antigens and the outcome of preclinical studies.

A clear conceptual basis for anti-sperm and other modes of immunological birth control exists in spite of the limited basic research done on surface antigens of sperm or egg. In the normal physiological condition, the immune system does not respond to sperm, egg or fetus. Compared with anti-egg or anti-fetus immunocontraception, an anti-sperm vaccine has two theoretical advantages. First it would work in both males and females; second, it would not raise problems of autoimmunity in the female if a sperm-specific protein is used. However, for the development of such contraceptive vaccines the following scientific questions need to be resolved: (1) what surface protein to use as an antigen; (2) what adjuvant to use in humans for an anti-fertility vaccine; (3) how to maintain a high titre; (4) how the contraceptive effect will be terminated; and (5) what are the potential side-effects.

PIP: Certain sperm antigens are auto- or isoimmunogenic, and naturally occurring sperm antibodies have been implicated in 10-15% of unexplained human infertility. Thus, efforts to develop an immunocontraceptive for human application have targeted sperm antigens. The World Health Organization Task Force on Contraceptive Vaccines designated the human sperm SP-10 as a primary vaccine candidate. The presence of SP-10 mRNA was demonstrated in baboons and macaques, and it is an ideal primate model for evaluating human efficacy. At a workshop on worldwide research on all monoclonal antibodies against sperm, HS-11 and HS-63 were selected for further evaluation because of their high specificity and significant anti-fertility effects. Isoenzyme LDH-C4 is a primary sperm antigen: it provokes antibodies that are absolutely cell specific and do not cross-react with somatic LDH isozymes. Immunization of both males and females with purified LDH-C4 results in an immune response and antibodies suppress fertility in female mice, rabbits and baboons. The PH-20 protein from guinea pigs has a required function in sperm-zona binding, and a 100% effective contraception is obtained when either male or female guinea pigs are immunized with purified PH-20. Regarding zona pellucida antigens (ZP), the porcine zona pellucida contains the major glycoprotein families identified as ZP1, ZP2 and ZP3. In a human in vitro fertilization system, only antibodies against ZP3 completely suppressed sperm-egg interaction. Passive administration of anti-zona pellucida antibodies results in long-term reversible contraception. The development of antigens capable of evoking an immune response, thereby preventing fertility without ovarian histopathology, is under way. A zona pellucida contraceptive vaccine containing 8-cell, but not T-cell, zona pellucida epitopes may prevent ovarian pathology.

Electron-microscopic localization of baboon acrosomal antigens using antisperm monoclonal antibody.

A sperm antigen corresponding to baboon sperm monoclonal antibody 1A9 was localized in the testis and ejaculated sperm in this animal, using the immunofluorescence technique and immunogold labelling. Immunohistochemical studies of the baboon testis showed that the antigenic determinant was localized in the late spermatid cells and spermatozoa close to the seminiferous tubules. Immunofluorescence studies indicate that the protein was localized on the acrosome region of ejaculated baboon sperm. At the electron-microscopic level, gold particles indicative of the presence of this determinant recognized by 1A9 monoclonal antibody were detected on the inner acrosomal region of ejaculated baboon sperm.

Stage-specific expression of a protein of the acrosome of baboon sperm during spermiogenesis detected with a monoclonal antibody.

A single monoclonal antibody, BSA4, raised against baboon epididymal sperm was used to study the ontogeny of the baboon sperm acrosome region during testicular spermiogenesis. This antibody is not species-specific but is restricted to the acrosome region in all other sperm examined (human, rat, and mouse). In the baboon, treatment of epididymal sperm with 0.05% Triton-X results in complete loss of anterior acrosome staining. Such treated sperm display a distinct equatorial staining. Antibody BSA4 reacts with a determinant (molecular weight, 43,000 d) that first appears in postmeiotic round spermatids during spermiogenesis. When tested for an effect on the fertilization process in vitro, the antibody BSA4 displayed significant inhibition, indicating a possible functional role for the determinant on mouse sperm. Using the avidin-biotin immunoperoxidase method, several stages of acrosome development were recognized: ie, cap, acrosome, and maturation stages of spermiogenesis. The antibody staining was restricted to the developing acrosome at all stages, indicating that the equatorial region is part of the acrosome and is expressed with temporal specificity during spermatogenesis in the baboon.

Monoclonal antibody localization of sperm surface antigen secreted by the epididymis of the baboon (Papio cynocephalus).

A monoclonal antibody (BSA6) was generated against an antigenic determinant secreted by the epididymis of the baboon and present on the acrosomal surface of the spermatozoa. This determinant was first secreted by the principal cells of the proximal corpus region, as determined by fluorescent microscopy performed on Bouin-fixed epididymal tissue sections. The secretory product subsequently bound on the lateral acrosomal surfaces in the distal corpus region, but became uniformly distributed over the acrosomal region in the cauda epididymidis. The antigenic determinant had a molecular weight of 82,000 (western blot technique). The testis, caput and other somatic tissues were devoid of the antigen, indicating the restriction of the antigen to spermatozoa and epithelial cells of the corpus epididymidis. Examination of similar tissue from immature baboons indicated that the secretion of this antigen was age-dependent, secretion beginning at about 4 years of age.

Characterization of baboon testicular antigens using monoclonal anti-sperm antibodies.

Sperm antigens that appear during spermatogenesis in the baboon were identified by using three monoclonal antibodies generated in culture from mice immunized with baboon caudal epididymal spermatozoa. Antibodies BSA1 and BSA2 recognize trypsin-sensitive 84,000 and 45,000 dalton determinants that are restricted to the tail and anterior acrosomal regions of the sperm, respectively, as determined by Western blot and immunofluorescence techniques. The tail antigen absent in 2- and 3-yr-old baboon testes first appears in spermatid cells at about 4 yr of age. In contrast, the acrosomal antigen recognized by BSA2 is present in 3-yr-old primitive testicular germ cells. In the mature testis, the 45,000 molecular weight determinant is predominantly localized in the nucleus of late pachytene spermatocytes and round spermatid cells as observed via the avidinbiotin immunoperoxidase method. Antibody BSA3 reacted only with sailidase-treated sections of adult testis. This trypsin-resistant determinant, not expressed on testicular sperm, is recognized by antibody BSA3 only on epididymal sperm, thus indicating a post-testicular sperm modification.