The effect of excess iron infectivity in vitro.

Many severe clinical conditions encountered in Africa involve the effects of iron overload on diseases (AIDS, TB etc) and vital organs (e.g., liver). To intervene successfully in the HIV pandemic, knowledge of AIDS pathogenesis and factors that stimulate or inhibit viral replication are crucial. Iron overload is believed to cause serious damage during HIV infection. Indeed, it is believed that the metal is required by infected cells to synthesize viral particles. The consequences of excess iron in vivo include the stimulation of microorganism growth, an increase in oxidative stress and an impairment of immune system function. Iron chelation have been reported to modulate some of these effects. In a project designed to assess the effect of in vitro iron overload (also synonymously referred to as iron loading) on HIV infection, cells (HIV-infected and controls) were directly loaded with iron and desferrioxamine (DFO, an iron chelator) respectively or combined. We then performed experiments to investigate the effects of these chemicals on host cell defenses and viral replication. Effective iron loading of all cell lines used was confirmed by emission spectroscopy. Through viability assays using tetrazolium salts, flow cytometric analysis of apoptosis and necrosis using Annexin-V, and specialised ELISAS; the effect of iron loading on host cell viability, survival or death and cytokine production was studied. The effect of iron loading on virus infectivity was also investigated by looking at core protein (p24) levels and reverse transcriptase (RT) activity. Prior to the start of the bioassays, several dyes were compared during identical procedures to find an effective and consistently functional dye assay for the assessment of cell growth/viability or proliferation. Viability assays provided a qualitative picture of events while flow cytometric analysis allowed us to compare viability with specific types of cell death (apoptosis/necrosis). Excess iron in the form of 500ƒÝM FeSO4-7H2O in addition to serum iron was found to be non-toxic to cells alone but detrimental to HIV-infected cells. Equimolar amounts of DFO inhibited cell growth, cytokine production and viral replication. Our results indicate that Fe loading stimulates viral replication. Iron chelation on the other hand decreased HIV replication suggesting a possible area for further therapy research using iron chelators in situations of iron loading in the presence of HIV/AIDS.Dr. Debra Meye