Figure 1

Sequence of events during the eclipse and viral expansion phases of acute HIV-1 infection. Mucosal transmission of HIV is followed by an eclipse phase of ~ 10 days during which small foci of infection are established in the mucosa, local virus replication occurs and infection spreads to local lymphoid tissues where further virus amplification takes place. More widespread virus dissemination then ensues, with infection of lymph nodes throughout the body including the GALT where high levels of virus replication take place, associated with an exponential increase in plasma viral titres. The horizontal dotted line indicates the limit of detection of many of the assays conventionally used to evaluate plasma HIV titres (~100 viral RNA copies/ml): the time at which this is exceeded constitutes the end of the eclipse phase. As illustrated, there is a relatively short window of opportunity during which infection could potentially be blocked, eradicated or constrained before substantial CD4+ T cell depletion occurs and the stage is set for subsequent disease progression.