Plasma levels of A-SAA are increased prior to and during detection of viremia in AHI A-SAA was shown previously to be elevated in patients with AIDS [16] , and is commonly used as a general marker for inflammation [17, 18] . A recent study demonstrated that A-SAA has anti-viral activity in vitro [19] . We therefore examined a larger set of plasma donor panels (19) by ELISA to test whether elevation of A-SAA levels may be a general feature associated with acute HIV-1 infection, and how its induction is related to the increase in plasma viral RNA titers. As a control and to establish a baseline for use in statistical analysis of the data, we also measured A-SAA levels in plasma panels from five control plasma donors who did not become infected with HIV (Fig. S2A) . Baseline levels of A-SAA (calculated as described in the methods section) varied between individuals and were generally between 600-3800ng/ml. Analysis of A-SAA levels in the plasma panels from HIV-infected donors confirmed that A-SAA was elevated relative to baseline prior to and/or concurrent within the earliest detection of viremia. Importantly, significant A-SAA elevations (i.e. falling above a 90% prediction interval) were observed prior to T 0 (viral RNA .100 copies ml 21 ) in 15 out of 19 subjects (Fig. 3A) . In the subject group as a whole, A-SAA levels were thus elevated significantly prior to T 0 , the time of first detection of plasma viremia (p = 0.02, as determined using a Binomial test).