Antiviral activity of subcellular fractions isolated from CD8⁺ cells of HIV-infected subjects. Subcellular fractions, obtained during the purification of intracellular granules, were diluted in their respective fractionation buffer and added to acutely infected CD4⁺ cells in a standardized β-chemokine—insensitive virus assay for CAF activity. ▪ indicates cytoplasmic fraction; ▨, soluble components of granules fraction; and ▦, granule membrane. Percentage suppression of HIV replication ± SD was determined by dividing the amount of peak RT activity (day 7) in the culture fluids treated with the test sample by that treated with the respective buffer control, × 100. The amount of peak RT activity in the control infected CD4⁺ cell cultures was always greater than 200 000 cpm/0.1 mL. Some toxicity was noted in the least diluted granule membrane extract of subject A (*), which explains the reduction in RT activity observed. CD8⁺ cells from subjects A and B showed production of CAF in cell culture; those from subject C did not (Table 1). Negative values indicate enhancement of HIV replication.