Analysis of the antibody repertoire of astrocytoma patients against antigens expressed by gliomas

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Abstract
The molecular characterization of antigens preferentially or exclusively expressed by astrocytomas and recognized by the autologous immune system are a prerequisite for the development of specific vaccines. To identify such antigens, we screened 5 cDNA expression libraries derived from astrocytomas and other gliomas for reactivity with high‐titered IgG antibodies in the sera of astrocytoma patients using SEREX, the serologic identification of antigens by recombinant cDNA expression cloning. Autologous and allogeneic SEREX analysis of >5 × 106 clones with the sera of 18 astrocytoma patients revealed 10 antigens: the differentiation antigen glial fibrillary acidic protein (GFAP), Bax‐inhibitor 1 (which was overexpressed in all glioma samples tested), 3 other molecules involved in the regulation of gene expression and proliferation (the nm23‐H2‐encoded nucleoside diphosphate kinase B, the Ran binding protein‐2 and a DNA binding protein encoded by the son gene), SP40,40 (a complement inhibitory molecule), the chaperonin TCP‐1, calnexin and 2 new gene products. No immune responses were detected against the “shared tumor” or “cancer testis antigens” that are regularly expressed in gliomas. Antibody responses in astrocytoma patients against antigens expressed by gliomas were rare and, with the exception of Bax‐inhibitor 1 and the product of the son gene, were also found in apparently healthy controls. We conclude that although astrocytomas express a broad spectrum of antigens, they elicit antibody responses only rarely, most likely because of their intrinsic immunosuppressive effects.