Polyvalent vaccines and therapeutics against viral pathogens

Abstract

Viral infections caused by HIV or influenza viruses have killed millions of people worldwide. Currently available drugs against such viruses do combat the infections to some extent but are not the best long-term solutions; drug toxicity, drug resistance and viral persistence are just some of the issues that are yet to be overcome. In this work, the concept of polyvalency was used to design viral inhibitors and vaccines. For the first part of my thesis, a universal vaccine has been developed by controlling the antigen (hemagglutinin) presentation to the immune system to enhance the accessibility of the conserved epitopes in the stalk. In preliminary in-vivo challenge experiments with a chimeric H5/1N1 virus, the hemagglutinin (head biotin)-nanotube conjugates (proposed vaccine) showed better protection than controls. We have subsequently expressed biotinylated hemagglutinin using baculoviral infection of insect cells and have optimized the purification scheme by adding a size exclusion chromatography step after the affinity chromatography step. For the second part of my thesis, polyvalent influenza therapeutics have been designed based on ‘hemagglutinin binding’ proteins that bind to conserved epitopes. We demonstrated that the dimers of both the HB proteins studied were more effective at inhibiting the binding of stalk-binding antibodies to hemagglutinin than the corresponding HB monomers. For the third part of my thesis, we designed polyvalent molecules that bind to multiple sites on HIV co-receptor, CCR5 (C-C chemokine receptor, type 5). We synthesized homodimeric, heterodimeric and multimeric versions of Leukotoxin E (LukE) (a CCR5-binding protein) and characterized their ability to inhibit the binding of a gp120-CD4 fusion protein (called FLSC) to CCR5+ 293T cells as compared to that of Leukotoxin E alone.