Figure 5

Plasma viral load (A) and SIV antibody response (B) in naïve and PEP-macaques inoculated intravenously with 10 AID₅₀ chimeric SIV/HIV-1 called SHIV_89.6P. PEP, post exposure prophylaxis. Macaques 95020 and M94312 were persistently virus-negative and weakly SIV-antibody positive (V^-Ab^±) after the first SIV_mne infection/PMPA PEP regimen (1^st PEP) [15]. Four years later, macaque M94312 received a second PEP regimen (2^nd PEP) involving one treatment interruption plus SIV_mne challenge at week 1 of a 5-week PMPA treatment. Thereafter, this macaque became persistently virus-negative and strongly-SIV antibody positive (V^-Ab⁺). Macaque 95020 was not given a second PEP and remained persistently virus-negative and weakly-antibody positive (V^-Ab^±). Both macaques were then challenged with SHIV_89.6P at the same time at 2.5 years after the 2^nd PEP (i.e. 6.5 years after the 1^st PEP). Two naïve macaques (99111 and 99107) served as infection controls. Plasma viremia was quantified by a branched DNA (bDNA) signal amplification assay for SIV by Bayer Diagnostics (Berkeley, CA). The target probes for the assay are designed to hybridize with the pol region of SIVmac strains of virus. This assay has a lower limit of detection of125 RNA copies/mL. Titers of SIV antibodies are expressed as the reciprocal of the highest dilution of plasma that was positive by HIV-2 EIA (Sanofi-Pasteur, Redmond, WA). The lowest plasma dilution used was 1:20.