Abstract
HIV is able to elude both cellular and humoral arms of the immune system; thereby making viral control difficult. Extra corporeal photochemotherapy (ECP) or photopheresis is an immunomodulatory therapy in which lymphocytes are reinfused into the host after exposure to a photoactive compound and ultraviolet A light. It is an effective therapeutic approach to several disorders of the immune system including acute and chronic graft-versus-host disease, scleroderma, and cutaneous T-cell lymphoma. This process may offer a novel approach to viral control with minimal or no toxicity. We initiated an ex vivo and subsequently a clinical pilot trial utilizing Benzoporphyrin Derivative as the photosensitive compound. Ex vivo dosing studies identified the minimum energy levels of light exposure and concentrations of BPD that eradicated both cell-free and cell-associated HIV-1 infectivity without destroying the virus particles or infected leukocytes. Leukocytes so treated remained viable. They did demonstrate altered cytokine and chemokine expression with apoptosis induced in a minority of CD4 but not CD8 positive cells. A pilot in vivo, 24 week clinical trial in seven HIV-1 infected patients (all were required, upon entry, to have viral loads of > 10,000) using the photopheresis parameters established above demonstrated that the treatment was well tolerated and beneficial. Three individuals who had rapidly rising viral loads prior to initiating therapy stabilized once treatment began. Two of which had a (sustained) greater than.5 log decrement and 5 had stable plasma viral loads (less than a.5 log increment or decrement) with varied effects on absolute CD4 and CD8 positive lymphocytes counts. One subject achieved a greater than 1 log decrement in HIV-1 plasma viral load also developed undetectable in vivo cell-free and cell-associated HIV-1 infectivity while demonstrating an increased in vitro lymphocyte mitogen stimulation index. Subsequently, under amended protocol 3 additional 12 month courses were administered to one additional patient and two of the previous enrollees. The area under the curve for viral load (viral load x # of weeks) for these ten courses of therapy showed a significant decrease from pre to post therapy (p 0.007). There were no significant changes in CD4 or CD8 numbers area under the curve (CD4 number # of weeks and CD8 number x # of weeks). None of the subjects developed an AIDS defining illness during the course of therapy nor were there any treatment associated toxicities. These studies suggest that ECP augments activity of various arms of the immune system without any significant toxicity and may be effective in controlling HIV replication. We have now instituted a Phase II study utilizing long-term photopheresis (twice monthly for 48 weeks) to further determine efficacy and mechanism of activity.
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