Structural modification of serum vitamin D3-binding protein and immunosuppression in AIDS patients

AIDS Res Hum Retroviruses. 1995 Nov;11(11):1373-8. doi: 10.1089/aid.1995.11.1373.


A serum glycoprotein, vitamin D3-binding protein (Gc protein), can be converted by beta-galactosidase of stimulated B lymphocytes and sialidase of T lymphocytes to a potent macrophage-activating factor (MAF), a protein with N-acetylgalactosamine as the remaining sugar moiety. Thus, Gc protein is a precursor for MAF. Treatment of purified Gc protein with immobilized beta-galactosidase and sialidase generates an extremely high-titered MAF (GcMAF). When peripheral blood monocytes/macrophages of 46 HIV-infected patients were treated with GcMAF (100 pg/ml), the monocytes/macrophages of all patients were efficiently activated. However, the MAF precursor activity of plasma Gc protein was low in 16 (35%) of of these patients. Loss of the MAF precursor activity appeared to be due to deglycosylation of plasma Gc protein by alpha-N-acetylgalactosaminidase found in the patient blood stream. Levels of plasma alpha-N-acetylgalactosaminidase activity in individual patients had an inverse correlation with the MAF precursor activity of their plasma Gc protein. Thus, precursor activity of Gc protein and alpha-N-acetylgalactosaminidase activity in patient blood can serve as diagnostic and prognostic indices.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acquired Immunodeficiency Syndrome / blood
  • Acquired Immunodeficiency Syndrome / enzymology
  • Acquired Immunodeficiency Syndrome / immunology*
  • Glycosylation
  • Hexosaminidases / blood*
  • Humans
  • Immunosuppression Therapy
  • Leukocytes, Mononuclear / immunology
  • Lymphocytes / immunology
  • Macrophage Activation
  • Macrophage-Activating Factors / blood*
  • Macrophages / immunology
  • Substrate Specificity
  • Vitamin D-Binding Protein / blood*
  • Vitamin D-Binding Protein / chemistry
  • alpha-N-Acetylgalactosaminidase


  • Macrophage-Activating Factors
  • Vitamin D-Binding Protein
  • Hexosaminidases
  • NAGA protein, human
  • alpha-N-Acetylgalactosaminidase