Repeated and spontaneous switching of the chemokine co-receptors used by HIV-1 is rare in vivo

Optimisation of the Degree of Sulfation of a Polymer Based Construct to Block the Entry of HIV-1 into Cells

Blocking the entry of HIV-1 into CD4+ cells is an important new therapeutic target for the development of novel vaginal microbicides. In this study, sulfated derivatives of the linear polysaccharide dextrin were synthesised whose percentage sulphation increased incrementally from 7.4 to 48.3%. Their anti-HIV-1 activity in C8166 cells was first seen when percentage sulfation reached 33.2%, but it was only seen in peripheral blood mononuclear cells when it reached 36.3%. It did not increase further when sulfation reached 40.2%. Primary viruses with a V3 loop charge of greater than +5 were blocked by 80 microg/ml of dextrin 2 sulfate but primary viruses with a V3 loop charge of less than +3 required 1,600 microg/ml to block viral entry effectively. Our results identify the relative contribution of the percentage sulfation of a polymer based construct for optimising its anti-HIV-1 activity whilst minimising its toxicity. A better understanding of these structure-function relationships will inform the design and development of novel vaginal microbicides to effectively block the sexual transmission of all primary viral isolates of HIV-1.

Surrogacy in antiviral drug development

The coming of age of molecular biology has resulted in an explosion in our understanding of the pathogenesis of virus related diseases. New pathogens have been identified and characterized as being responsible for old diseases. Empirical clinical evaluation of morbidity and mortality as outcome measures after a therapeutic intervention have started to give way to the use of an increasing number of surrogate markers. Using a combination of these markers, it is now possible to measure and monitor the pathogen as well as the host's response. Nowhere is this better exemplified in virology than in the field of AIDS. We have utilized the advances in pathogenesis and new antiretroviral drug development to: * develop a new class of drugs which block the entry of HIV-1 into cells. * develop a new approach for effectively delivering these drugs to those tissues in which most viral replication takes place. Over the last 10 years, our work has progressed from concept to clinical trial. Our laboratory based evaluation of the new molecules developed as well as our clinical evaluation of their safety and efficacy have had to respond and adapt to the rapid changes taking place in AIDS research. This paper discusses the problems encountered and the lessons learnt.