The human non-lineage antigen CD46 (HuLy-m5) and primate retroviral gp70 molecules share protein-defined antigenic determinants.
The CD46 lymphocyte surface antigen of man (until recently called HuLy-m5), and defined by the E4.3 monoclonal antibody (MoAb), shares cross-reactive antigenic epitopes with the envelope gp70 glycoproteins of gibbon ape leukaemia virus (GaLV) and Mason Pfizer monkey virus (MPMV) primate retroviruses. It is now shown that the cross-reactive antigenic epitope shared by these three molecules is determined solely by the protein portion of these glycoproteins, and that the N-linked and O-linked carbohydrate moieties of these glycoproteins do not directly or sterically contribute to the antigenic cross-reactivity. When CD46 molecules (mol.wt = 66 and 56 kDa) from human thymocytes were stripped of sialic acid with neuraminidase, or stripped of N-linked carbohydrate with endoglycosidase F, the E4.3 MoAb was still able to bind and immunoprecipitate the protein core of CD46 (mol.wt = 56 and 44 kDa). Similarly, polyclonal antisera to GaLV and MPMV precipitated deglycosylated CD46, although at a reduced efficiency. The cross-reacting E4.3 MoAb, anti-GaLV and anti-MPMV antisera also immunoprecipitated HuLy-m5 primary translation protein lacking N- or O-linked carbohydrate from the in vitro translation products of human thymocyte mRNA. Thus, the antigenic cross-reactivity of CD46 molecules with GaLV gp70 and MPMV gp70 is both specific and due to protein structure rather than to carbohydrate; the findings suggest that retroviruses may have acquired a functional epitope from human CD46 or that an endogenous retroviral sequence of human may partially or completely encode the CD46 antigen.
Purcell
D F
DF
Department of Pathology, University of Melbourne, Parkville, Vic., Australia.
Deacon
N J
NJ
McKenzie
I F
IF
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000276:immunology*; D000943:Antigens, Differentiation / Q000276:immunology*; D000956:Antigens, Viral / Q000276:immunology*; D002852:Chromatography, Ion Exchange; D003429:Cross Reactions; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000276:immunology*; D006026:Glycoside Hydrolases; D006801:Humans; D037102:Lectins; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins; D051379:Mice; D009439:Neuraminidase; D037121:Plant Lectins; D011061:Poly A / Q000378:metabolism; D011233:Precipitin Tests; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D015682:Retroviridae Proteins, Oncogenic / Q000276:immunology*; D015302:Simian Immunodeficiency Virus / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology; D014759:Viral Envelope Proteins / Q000276:immunology*
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000943:Antigens, Differentiation; D000956:Antigens, Viral; C497857:CD46 protein, human; D000939:Epitopes; D037102:Lectins; C497859:Mcp protein, mouse; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins; D037121:Plant Lectins; D012333:RNA, Messenger; D015682:Retroviridae Proteins, Oncogenic; D014759:Viral Envelope Proteins; C033619:lentil lectin; D011061:Poly A; D006026:Glycoside Hydrolases; D009439:Neuraminidase