Figure 1. Nonsuppressible viremia can result from large clones of infected cells.

(A) Plasma virus levels before and following initiation of antiretroviral therapy (ART). ART, represented as 3 gray bars to show a combination therapy regimen, generally blocks new infection of susceptible cells and reduces viremia to below the limit of detection of clinical assays (dotted black line). However, low-level viremia persists (dashed red line), representing virus release from cells in the latent reservoir that have become activated. (B) CD4⁺ T cells comprise the latent reservoir, with colors representing different clonal lineages. The size and composition of the reservoir are generally such that the level of virus released from reservoir cells is below the limit of detection of clinical assays (dotted line). However, in some individuals, clones can expand to a very large size (yellow and blue cells) and release a sufficient amount of virus to produce detectable viremia. This viremia cannot be suppressed by ART, which continues to block new infection of susceptible cells but not virus release from previously infected cells.