HIV Viral Load Response to Antiretroviral Therapy According to the Baseline CD4 Cell Count and Viral Load

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Abstract
For many patients with chronic, asymptomatic, human immunodeficiency virus (HIV) infection who have not received antiretroviral therapy (ART), it is unclear whether such therapy should be initiated immediately or deferred until the CD4 cell count is lower, and/or the plasma viral load is higher. Viral load levels tend to change only moderately over time in untreated individuals, with at most approximately a 0.1 log copies/mL increase per year, although this rate of increase varies across individuals.1-4 In untreated HIV infection, the risk of acquired immunodeficiency syndrome (AIDS) diseases is known to be small before the CD4 cell count has reached 200 × 106/L5,6 or the viral load has reached 10 000 copies/mL.4 Early therapy brings immediate intervention against a virus known to be causing immune damage, provides the potential for preservation of HIV-specific CD4 cells and the microarchitecture of lymphoid organs, and lowers the viral load to reduce infectivity and prevent AIDS diseases with high case-fatality rates, such as lymphoma, which can occasionally occur at high CD4 cell counts and are refractory to therapy. Delaying therapy, on the other hand, means avoiding the risk of drug toxic effects, selection for drug resistance, and the inconvenience of adhering to a complex regimen for an extended period. It also may mean that when therapy is finally initiated, it is with a more potent and/or more tolerable regimen developed in the intervening period. Furthermore, relatively complete immune reconstitution can be achieved with virologically suppressive therapy, even when initiated in people with very low CD4 counts.7-9 There is no direct evidence from trials of when the optimum time is to initiate therapy in the highly active ART era. The lack of firm data on this issue is illustrated by the differences between various expert recommendations.10-12

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