Analysis of a Human Sperm CD52 Glycoform in Primates: Identification of an Animal Model for Immunocontraceptive Vaccine Development1

Abstract

Sperm agglutination antigen-1 (SAGA-1) is a human male reproductive tract glycoform of CD52. Unique modification of CD52 N-linked oligosaccharide chains in the epididymis and vas deferens results in the appearance of a carbohydrate epitope that is localized over the entire surface of human spermatozoa. SAGA-1 was characterized by the sperm-inhibitory murine monoclonal antibody (mAb) S19, and it is the target antigen of a human mAb (H6-3C4) associated with antibody-mediated infertility. Collectively, sperm surface localization, antibody inhibition of sperm function, and potential reproductive-tissue specificity identify SAGA-1 as an attractive candidate contraceptive immunogen. To establish an animal model for the study of SAGA-1 in immunologic infertility and immunocontraceptive development, we investigated the appearance of the S19 carbohydrate epitope in nonhuman primates. The S19 mAb demonstrated little to no immunoreactivity by Western blot analysis with protein extracts of spermatozoa from the baboon, marmoset, bonnet, cynomolgus, and pigtailed macaques. Immunohistochemical analysis identified CD52 in the bonnet monkey epididymis; however, the N-linked carbohydrate moiety recognized by the S19 mAb, and unique to SAGA-1, was absent. In contrast, the S19 carbohydrate epitope was identified in chimpanzee sperm extracts by Western blot analysis and in chimpanzee epididymal tissue sections by immunohistochemical analysis, indicating that it is conserved in this close relative of the human. Chimpanzee testis, seminal vesicle, and prostate do not express the S19 epitope. Although anti-CD52 immunoreactivity was identified in the spleen, the carbohydrate moiety recognized by the S19 mAb was absent, corroborating data in the human that demonstrated tissue-specific glycosylation of sperm CD52. Immunofluorescent analysis indicated that the chimpanzee homologue of sperm CD52 was present over the entire spermatozoon. In addition, the S19 mAb agglutinated chimpanzee spermatozoa in a manner similar to the effect observed on human spermatozoa. These data indicate that the distinctive carbohydrate moiety of human sperm CD52 is present in the chimpanzee, and they identify the chimpanzee as the most appropriate primate model to study the potential of this unique CD52 glycoform as a contraceptive immunogen.

Systematic review of chimpanzee use in monoclonal antibody research and drug development: 1981-2010

“…Bone marrow is the source of blood cells (hematopoiesis) and, due to advances in biochemical techniques, may provide ever-increasing amounts of information about the physical and chemical characteristics of blood cells and related molecules. While a less frequent occurrence, researchers in a 2002 reproductive study obtained samples of the chimpanzee spleen, external and internal reproductive tract, and sperm from a contractor housing primates (McCauley et al, 2002). In a 1982 study, spleens were removed entirely from 19 chimpanzees before they were infected with malaria in order to observe the immune response in the absence of this important lymphoid organ (Nardin et al, 1982).…”

“…Only a few articles gave information on age, sex, weight, and possible prior exposure to infectious disease(s) (Crowe et al, 1994;ten Cate et al, 1993). Since the early 1990's, many articles -approximately 25% -contained a statement that the procedures observed in the study complied with the applicable institutional animal care guidelines (Chen et al, 2006a;McCauley et al, 2002).…”

Post-translational modifications in glycosylation status during epididymal passage and significance in fertility of a 33 kDa glycoprotein (MEF3) of rhesus monkey (Macaca mulatta)

“…Similar proteins common to macaque and human spermatozoa have been reported by other investigators. These include ESC42 (Liu et al 2001), HE1/NPC2 (Kirchhoff 1999), FLB1 (Boue et al 1995), sperm agglutination antigen-1 (SAGA-1), and CD52 (Diekman et al 1997, McCauley et al 2002. However, the epididymal-specific expression of HE1/NPC2, ESC42, ESP13.2, SAGA-1, and CD52 as identified and sequenced by subtractive epididymal cDNA library screening greatly contrasts with the expression of the 33 kDa glycoprotein of rhesus epididymis, which is first expressed at the testicular level on the surface of spermatocytes, spermatids, and testicular spermatozoa.…”

Glycomics and Proteomics Analyses of Mouse Uterine Luminal Fluid Revealed a Predominance of Lewis Y and X Epitopes on Specific Protein Carriers

“…Adsorption or interactions with various glycotopes presented by these secretory glycoproteins may have profound effect in modulating the characteristics of sperm glycocalyx (7,8) and, through that, its fertilizing potential. The observation that glycotopes are often involved in eliciting antisperm immune responses (9) and the many reported incidences of their dynamic modulation in association with sperm fertility underscore the importance of precise structural and functional knowledge in efforts directed toward developing them as targets for immunocontraceptive vaccines (10).…”