FIG. 2.

Characterization of soluble factor-mediated CD8⁺ lymphocyte antiviral activity. (A) Dose dependence of the suppression of SIVmac replication in vitro. Titrations of three supernatant fluids giving more than 80% suppression when tested at a dilution of 1:5 are shown. (B) Impact of CD8⁺ cell supernatants on the viability of activated CD4⁺ T cells, as measured by neutral red staining. Staining was performed after 3 days in culture, on 100,000 activated CD4⁺ T cells in the presence of a 1:5 dilution of CD8⁺ cell supernatant fluid. Mean absorbance values at 540 nm are shown for the neutral red staining of cultures incubated in the presence of a 1:5 dilution of supernatants displaying various degrees of inhibition and were collected from 7 to 35 days after infection. As a control, 50,000, 100,000, 200,000, or 300,000 cells were cultured without CD8⁺ cell supernatants. (C) Spearman's rank correlation analysis of the possible relationship between CD8 antiviral activity and MIP-1β concentration. (D) Spearman's rank correlation analysis of the possible relationship between CD8 antiviral activity and RANTES concentration. (E) The inhibition of HIV-1Lai and SIVmac251replication is compared for 5 CD8⁺ supernatants, with percent inhibition given for tests at a dilution of 1:5 against SIVmac251. HIV-1Lai replication was resistant to MIP-1α, MIP-β, or RANTES alone or in association.