Structure-Based Stabilization of HIV-1 gp120 Enhances Humoral Immune Responses to the Induced Co-Receptor Binding Site

The human immunodeficiency virus type 1 (HIV-1) exterior envelope glycoprotein, gp120, possesses conserved binding sites for interaction with the primary virus receptor, CD4, and also for the co-receptor, generally CCR5. Although gp120 is a major target for virus-specific neutralizing antibodies, the gp120 variable elements and its malleable nature contribute to evasion of effective host-neutralizing antibodies. To understand the conformational character and immunogenicity of the gp120 receptor binding sites as potential vaccine targets, we introduced structure-based modifications to stabilize gp120 core proteins (deleted of the gp120 major variable regions) into the conformation recognized by both receptors. Thermodynamic analysis of the re-engineered core with selected ligands revealed significant stabilization of the receptor-binding regions. Stabilization of the co-receptor-binding region was associated with a marked increase in on-rate of ligand binding to this site as determined by surface plasmon resonance. Rabbit immunization studies showed that the conformational stabilization of core proteins, along with increased ligand affinity, was associated with strikingly enhanced humoral immune responses against the co-receptor-binding site. These results demonstrate that structure-based approaches can be exploited to stabilize a conformational site in a large functional protein to enhance immunogenic responses specific for that region

Lipoprotein Lipase Activity in Patients with Diabetes Mellitus, with and without Hyperlipemia

No detectable abnormalities or changes in the post heparin plasma lipoprotein lipase (LPL) activity were found in fifteen “insulin independent” (stable) or sixteen “insulin dependent” (labile) diabetics, with or without hyperlipemia, in four patients with ketoacidosis and hyperlipemia both during the acute phase and after recovery, in two subjects with insulin induced hypoglycemia, and in two patients with gross hyperlipemia and diabetes during marked fluctuations in lipid levels in one, and during correction of the hyperlipemia in the other. Abnormalities in the LPL system, as reflected in the post heparin plasma LPL activity, appear to play a minor role, if any, in the pathogenesis of diabetic hyperlipemia in man.</jats:p