The overall objective of this project is to develop a novel type of gp120 vaccine that exploits the natural anti-Gal antibody (Ab) as a natural adjuvant effectively targeting gp120 to antigen presenting cells (APC). This vaccine is comprised of gp120 engineered to express multiple alpha-gal epitopes (Galphal/alpha1-3 Galbeta1-4GlcNAc-R) on the many N(asparagine)-linked carbohydrate chains of this glycoprotein. HIV vaccines have to be effectively targeted to APC in order to elicit a protective immune response. Changing carbohydrates on gp120 to alpha-gal epitopes will significantly increase uptake of antigen by APC by both eliminating the negative charge of gp120 and by targeting gp120 to APC Fcgamma receptors. We propose to convert the multiple sialic acid (SA) units on recombinant gp120 produced in CHO cells, into alpha-gal epitopes (referred to as gpl20(gal) by the use of recombinant alpha1,3 galactosyltransferase (alpha 1,3 GT) that we produce. Vaccination with gpl20/alpha/gal is likely to result in in situ formation of immune complexes with the natural anti-Gal Ab, the most abundant Ab in humans constituting 1% of circulating IgG. We hypothesize that the immune complexes formed between gpl20/alpha/gal and anti-Gal target the vaccinating molecules to APC, since the Fc portion of the complexed anti-Gal IgG binds to Fcgamma receptors on APC. This results in increased processing and presentation (including cross presentation) of gp120 peptides for effective activation of CD4+ and CD8+ T cells.
Our aim i s to obtain a proof of principle for the increased immunogenicity of gp120(gal in comparison with that of gp120 in an experimental animal model system of (l,3GT knockout mice which simulates pertinent immune parameters in humans. Specifically, we propose: 1. To process and purify large amounts of gp120/alpha/gal for use as vaccine. 2. To demonstrate the superiority of the gp120/alpha/gal vaccine for increasing humoral and cellular immune response in mice in comparison with gp120 vaccine. If we find, in this preliminary project, that gp120/alpha/gal vaccine is significantly more immunogenic than gp120, we will, in future studies, increase the range of antigenic targets by fusing gp120 with p18 or p24 of HIV. We will then also collaborate with a group studying immune responses in monkeys to determine the efficacy of this vaccine in a primate model.
| Macher, Bruce A; Galili, Uri (2008) The Galalpha1,3Galbeta1,4GlcNAc-R (alpha-Gal) epitope: a carbohydrate of unique evolution and clinical relevance. Biochim Biophys Acta 1780:75-88 |
| Abdel-Motal, Ussama; Wang, Shixia; Lu, Shan et al. (2006) Increased immunogenicity of human immunodeficiency virus gp120 engineered to express Galalpha1-3Galbeta1-4GlcNAc-R epitopes. J Virol 80:6943-51 |
