CD40 Ligand Dysregulation in HIV Infection: HIV Glycoprotein 120 Inhibits Signaling Cascades Upstream of CD40 Ligand Transcription

Abstract

IL-12 production and up-regulation of CD40 ligand (CD40L) expression are impaired in the PBMC of HIV-infected donors, and exogenous CD40L rescues IL-12 production by such cells. In this study, we implicate dysregulation of CD40L expression in the IL-12 defect associated with HIV by demonstrating that induction of CD40L expression by anti-CD3/CD28 stimulation was directly correlated with the IL-12 productive capacity of PBMC. Further, we demonstrate marked decreases in the induction of CD40L protein and mRNA following anti-CD3/CD28 stimulation in HIV-infected donors compared with uninfected donors, with a tight association between these two levels. Inhibition of CD40L up-regulation was selective, as induction of CD69 or OX40 was not as severely affected. Increased instability of CD40L mRNA did not constitute a major mechanism in CD40L dysregulation, thus suggesting a potential defect in the signaling cascades upstream of transcription. The mechanisms by which HIV infection affects the induction of CD40L expression appear to involve HIV gp120-mediated engagement of CD4. Indeed, anti-CD4 mAb or inactivated HIV virions that harbor a conformationally intact gp120 significantly inhibited CD40L up-regulation at both the protein and mRNA levels. This inhibition was due to the native, virion-associated gp120, as coculture with soluble CD4 or heat treatment of inactivated HIV abolished their effect. These in vitro models mirror the CD40L defect seen in cells from HIV-infected donors and thus provide a suitable model to investigate HIV-induced CD40L dysregulation. Clear elucidation of mechanism(s) may well lead to the development of novel immunotherapeutic approaches to HIV infection.

CD8+ Lymphocyte-Mediated Injury of Dorsal Root Ganglion Neurons during Lentivirus Infection: CD154-Dependent Cell Contact Neurotoxicity

“…CD154 is the cognate ligand for CD40 and is principally expressed on activated T cells. FIV infection markedly increased CD154 expression on T cells both in vivo and in vitro, similar to that observed in HIV infection (Zhang et al, 2004), although PMA decreased the CD154 expression on uninfected T cells, including CD4ϩ and CD8ϩ T cells in vitro, which was correlated with the degree of neuronal injury. Functional blockage of CD154 expression on CD8 T cells significantly attenuated the neuronal injury induced by FIV-infected and uninfected CD8ϩ T cells in terms of neurite length and soma size, indicating that engagement of CD40 expressed on neurons by CD154 expressed by CD8ϩ T cells caused DRG neuronal injury.…”

Role of CD40-Dependent Down-Regulation of CD154 in Impaired Induction of CD154 in CD4+ T Cells from HIV-1-Infected Patients

“…The clinical relevance of CD154 as well as its central role as a regulator of cell-mediated and humoral immunity led to studies that examined whether induction of CD154 is defective in CD4 ϩ T cells from HIV-1 ϩ patients. Although there are reports that HIV-1 infection is accompanied by defective CD154 induction upon T cell activation (13)(14)(15)(16)(17)(18), other studies did not find evidence of this defect (19,20). A common feature of the studies that reported a normal induction of CD154 in CD4 ϩ T cells from HIV-1 ϩ patients is that T cell activation was induced in the absence of CD40 ϩ APC (19,20).…”

“…After treatment with DNase (Ambion), 0.5 g of RNA was used to generate cDNA using oligo(dT) [12][13][14][15][16][17][18] primers and Superscript III reverse transcriptase (Invitrogen Life Technologies). cDNA was subjected to RT-PCR using the LightCycler SYBR green fluorophore.…”

“…cDNA was subjected to RT-PCR using the LightCycler SYBR green fluorophore. Primer sequences for CD69 and CD154 were previously described (18,24). Expression of these genes was assessed by real-time quantitative RT-PCR using a DNA Engine Opticon System (MJ Research).…”

CD40, autophagy and Toxoplasma gondii

“…Impaired CD154 induction is particularly more pronounced in preterm babies (Kaur et al 2007), a finding relevant to toxoplasmosis in newborns since this is an infection acquired prior to birth. The CD40-dependent pathway of host protection is also relevant to HIV-1 + patients because these individuals exhibit a defect in CD154 induction in their CD4 + T cells (Subauste et al 2001, 2007b, Zhang et al 2004.…”