Extended Data Figure 1: Extensive caspase 1 activation in dying lymphoid CD4 T cells infected with either NL4-3 or a primary HIV-1 isolate.

a, Dying CD4 T cells activate caspase 1. HLACs were infected with NL4-3 or with a primary HIV-1 isolate 89.6 obtained from a mixed PBMC culture from an AIDS patient. The 89.6 viral isolate replicates to high titres in primary human cells such as macrophages and lymphocytes. It is highly cytopathic and utilizes both CCR5 and CXCR4 as co-receptors (dual-tropic)^18,54. Infected cells were treated either with no drugs or with AMD3100 (250 nM) entry inhibitor, as indicated. Caspase 1 activity was determined by flow cytometry using FLICA 12 h after treatment with nigericin (10 μM) or 3 days after infection with HIV. Notably, equivalent levels of caspase 1 activation were observed in CD4 T cells infected with NL4-3 or 89.6 HIV-1 isolate. AMD3100 prevented caspase 1 activity with both viruses, indicating the abundant presence of CXCR4-expressing target CD4 T cells in these cultures. b, Low levels of caspase 3 activity in dying CD4 T cells. The same cultures as in (a) were tested for caspase 3 activity using FLICA. Compared to caspase 1, infections with NL4-3 and 89.6 HIV-1 isolate induced low levels of caspase 3 activation in dying CD4 T cells. No caspase 3 activation was observed in cells treated with nigericin, which signals the NLRP3 inflammasome to activate caspase 1 (ref. 19), indicating a specific recognition of caspase 1 and caspase 3 activity by the FLICA probes. These data are the representative results of four independent experiments performed in tonsil cells isolated from four different donors.