Objective: To evaluate the presence of IgA directed to the CD4-binding domain of gp120 and to a conserved region of gp41 (the Kennedy epitope) in serum and parotid saliva of HIV-1-seropositive patients.
Methods: IgA were separated from IgG by anion-exchange chromatography and protein G treatment. The reactivity of IgA was tested against peptides and fusion proteins of the maltose-binding protein (MBP) and the CD4-binding site (MBP24) and MBP and the Kennedy epitope (MBP42). The capacity of serum and saliva IgA to interfere with the gp120–soluble CD4 (sCD4) interaction was examined. IgA were also purified by affinity chromatography using the MBP proteins adsorbed to a resin.
Results: Peptides representing the CD4-binding domain and the Kennedy epitope were recognized by serum and saliva IgA of HIV-1-seropositive patients. Of the sera and saliva samples tested, 6/26 serum IgA and 5/25 saliva IgA inhibited the gp120–sCD4 interaction by approximately 50%. The gp120–sCD4 interaction was inhibited by MBP24 affinity-purified IgA but not by MBP42 affinity-purified IgA.
Conclusion: Immunogens capable of eliciting IgA antibodies that inhibit gp120–CD4 binding might be efficiently used in vaccine to prevent mucosal transmission of HIV-1.
From the aGroupe Immunité des Muqueuses et Agents Pathogènes, University of Saint-Etienne, Saint-Etienne and the bLaboratoire de Radio et Immuno-analyses, Fédération de Biochimie, Hôpital Edouard Herriot, Lyon, France.
Correspondence to Nadine Vincent, Groupe Immunité des Muqueuses et Agents Pathogènes, University of Saint-Etienne, 15 rue Ambroise Paré, 42023, Saint-Etienne Cedex 02, France and Etienne Malvoisin: Laboratoire de Radio et Immuno-analyses, Fédération de Biochimie, Hôpital Edouard Herriot, Place d'Arsonval, 69437 Lyon Cedex 03, France.
Received: 25 September 2002; revised: 30 May 2003; accepted: 23 June 2003.