Figure 2: Post-challenge viraemia and CD4+ T-cell counts.

For CD4+ cell counts, total lymphocyte numbers were multiplied by the per cent CD3+ CD4+ lymphocyte staining based on flow cytometry and reported as the number of cells per microlitre of whole blood. Plasma viral levels were determined by a branched DNA-amplification assay with a detection limit of 500 viral RNA copies per ml (Bayer Diagnostics).