Expression of alpha-gal epitopes on ovarian carcinoma membranes to be used as a novel autologous tumor vaccine.
OBJECTIVE
Poor presentation of tumor-associated antigens (TAA) to the immune system remains a major obstacle to effective anti-tumor vaccine therapy. The aim of this study is to demonstrate the feasibility of producing a novel autologous tumor vaccine from ovarian carcinoma that is expected to have increased immunogenicity. The strategy is based on the ability of the anti-Gal IgG antibody (a natural antibody comprising 1% of IgG in humans) to target tumor membranes expressing alpha-gal epitopes (Galalpha1-3Galbeta1-4GlcNAc-R) to antigen-presenting cells (APC).


METHODS
Freshly obtained ovarian carcinoma tumors are homogenized, washed, and incubated with a mixture of neuraminidase, recombinant alpha1,3 galactosyltransferase (ralpha1,3GT) and uridine diphosphate galactose (UDP-Gal) to synthesize alpha-gal epitopes on carbohydrate chains of glycoproteins of these membranes. Subsequently, the processed membranes are analyzed for expression of alpha-gal epitopes and for the binding of anti-Gal.


RESULTS
Incubation of 3 g of ovarian carcinoma membranes, from five different patients, at 100 mg/ml, mixed together with ralpha1,3GT (50 microg/ml), neuraminidase (1 mU/ml), and UDP-Gal (2 mM), resulted in the effective synthesis of alpha-gal epitopes to the extent of approximately 2 x 10(11) epitopes/mg of tumor membranes. As a result of this de novo expression of alpha-gal epitopes, the tumor membranes readily bound purified anti-Gal antibody, as well as anti-Gal in autologous serum.


CONCLUSIONS
The method described in this study is very effective in the synthesis of many alpha-gal epitopes on tumor membranes obtained from ovarian carcinoma. These novel epitopes readily bind the naturally occurring anti-Gal antibody. This technique of opsonization of alpha-gal-modified autologous tumor membranes carrying TAA is expected to increase effective uptake of the vaccine by APC, which is key to successful anti-tumor vaccination.
Galili
Uri
U
Department of Cardiovascular Thoracic Surgery, Rush University, Chicago, IL 60612, USA.
Chen
Zhao-chun
ZC
DeGeest
Koen
K
D000938:Antigen-Presenting Cells / Q000276:immunology; D019496:Cancer Vaccines / Q000276:immunology*; D002240:Carbohydrate Sequence; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000096:biosynthesis / Q000276:immunology; D005260:Female; D005700:Galactosyltransferases / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D008562:Membrane Glycoproteins / Q000276:immunology; D008969:Molecular Sequence Data; D009439:Neuraminidase / Q000378:metabolism / Q000494:pharmacology; D010051:Ovarian Neoplasms / Q000276:immunology* / Q000378:metabolism; D014312:Trisaccharides / Q000096:biosynthesis* / Q000276:immunology*; D014531:Uridine Diphosphate Galactose / Q000378:metabolism / Q000494:pharmacology
D019496:Cancer Vaccines; D000939:Epitopes; D007074:Immunoglobulin G; D008562:Membrane Glycoproteins; D014312:Trisaccharides; C076569:alpha-galactosyl epitope; D014531:Uridine Diphosphate Galactose; D005700:Galactosyltransferases; C047006:N-acetyllactosaminide alpha-1,3-galactosyltransferase; D009439:Neuraminidase