Next-Generation mRNA Sequencing Reveals Pyroptosis-Induced CD4 ⁺ T Cell Death in Early Simian Immunodeficiency Virus-Infected Lymphoid Tissues

Abstract

Lymphoid tissues (LTs) are the principal sites where human immunodeficiency virus type 1 (HIV-1) replicates and virus-host interactions take place, resulting in immunopathology in the form of inflammation, immune activation, and CD4؉ T cell death. The HIV-1 pathogenesis in LTs has been extensively studied; however, our understanding of the virus-host interactions in the very early stages of infection remains incomplete. We investigated virus-host interactions in the rectal draining lymph nodes (dLNs) of rhesus macaques at different times after intrarectal inoculation (days postinoculation [dpi]) with simian immunodeficiency virus (SIV). At 3 dpi, 103 differentially expressed genes (DEGs) were detected using next-generation mRNA sequencing (RNA-seq). At 6 and 10 dpi, concomitant with increased SIV replication, 366 and 1,350 DEGs were detected, respectively, including upregulation of genes encoding proteins that play a role in innate antiviral immune responses, inflammation, and immune activation. Notably, genes (IFI16, caspase-1, and interleukin 1␤ [IL-1␤]) in the canonical pyroptosis pathway were significantly upregulated in expression. We further validated increased pyroptosis using flow cytometry and found that the number of CD4 Secondary lymphoid tissues (LTs) are the principal sites where human immunodeficiency virus type 1 (HIV-1) replicates and host-virus interactions take place, resulting in immune activation, inflammation, CD4 ϩ T cell death, and ultimately immune deficiency (1-3). However, the mechanisms underlying immunopathogenesis in LTs during very early infection, especially CD4 ϩ T cell death, remain incompletely understood. CD4 ϩ T cell death is a hallmark of disease progression in HIV-1 infection. To date, several mechanisms have been proposed to explain CD4 ϩ T cell death during HIV-1 infection in LTs. First, CD4ϩ T cell death results directly from HIV-1 productive infection via viral cytopathic effect. However, only a small fraction of total CD4 ϩ T cells in LTs are productively infected by HIV-1 (4, 5); therefore, pathogenic effect alone is not sufficient to account for the overall CD4 ϩ T cell death in vivo. Another proposed mechanism is apoptosis in HIV-1 uninfected bystander CD4 ϩ T cells mediated through Fas and TRAIL (tumor necrosis factor [TNF]-related apoptosis-inducing ligand) signaling (6-8). It was also demonstrated that HIV-1 Gp120 protein, expressed on the mem-

Rapid Loss of CD4 T Cells by Pyroptosis during Acute SIV Infection in Rhesus Macaques

“…Our results confirm and extend a previous study showing upregulation of genes involved in pyroptosis pathway in draining LNs during early SIV infection by bulk RNA-seq ( 28 ). We investigated immunologic and transcriptomic profiles of systemic CD4 T cells from GALT and lymphoid tissues during acute SIV infection and assessed the contributions from all potential programmed cell death mechanisms to CD4 T cell death.…”

Rapid Loss of CD4 T Cells by Pyroptosis During Acute SIV Infection in Rhesus Macaques

“…Our results confirm and extend a previous study showing upregulation of genes involved in pyroptosis pathway in draining LNs during early SIV infection by bulk RNA-seq (27). We investigated immunologic and transcriptomic profiles of systemic CD4 T cells from GALT and lymphoid tissues during acute SIV infection and assessed the contributions from all potential programmed cell death mechanisms to CD4 T cell death.…”

The anti-caspase 1 inhibitor VX-765 reduces immune activation, CD4+T cell depletion, viral load and total HIV-1 DNA in HIV-1 infected humanized mice

“…In the lymp nodes, the induction of an early inflammasome from day 1 and day 3 p.i. on, was evident from the upregulation of the NOD-like receptors NLRP1, NLRP3, AIM2, CASP-1 and IL-1 β, indicating an early host response to HIV-1 infection in humanized mice, in agreement with results obtained from the SIV model (43,44). After the initial burst we observed a second phase of transcriptomic changes dominated by IFI16 and AIM2 in bone marrow, lymph nodes and spleen.…”