Jeffrey N. Siegel

Measurement of CD69 induction in the assessment of immune function in asymptomatic HIV-infected individuals

Peripheral blood mononuclear cells from many asymptomatic HIV-infected patients exhibit defects in cytokine production and impaired proliferative responses in vitro but the mechanisms underlying this subclinical immune deficiency are controversial. To determine whether abnormalities in the earliest events following receptor engagement may help to explain the in vitro immune dysfunction, we measured the inducibility of the early activation marker CD69 in T cells from asymptomatic HIV-infected individuals in response to stimulation with anti-CD2 or anti-CD3 mAb. In a whole blood assay, we found that induction of CD69 was markedly impaired in CD4+ T cells from later-stage HIV-infected patients (CD4 counts 200-400/mm3) compared to uninfected controls. Among early stage patients (CD4 > 400/mm3), a subset (29%) had impaired CD69 induction. CD69 responses were equally depressed after stimulation through the CD3 or CD2 receptor pathways. Survey of a panel of immunophenotypic markers and propensity for apoptosis demonstrated a significant association between depressed induction of CD69 and decreased percentages of CD4+CD26+ and CD4+CD95+ cells but no association with the level of apoptosis. These data indicate that defects in T lymphocyte activation through CD3 and CD2 can be measured within hours of receptor stimulation in asymptomatic HIV-infected individuals and might be useful to monitor as an indicator of immune function in these patients.

Synthesis and Biological Evaluation of a New Series of 1,2,4-triazolo[1,5-a]-1,3,5-triazines as Human A2A Adenosine Receptor Antagonists with Improved Water Solubility

The structure-activity relationship (SAR) of 1,2,4-triazolo[1,5-a]-1,3,5-triazine derivatives related to ZM241385 as antagonists of the A(2A) adenosine receptor (AR) was explored through the synthesis of analogues substituted at the 5 position. The A(2A) AR X-ray structure was used to propose a structural basis for the activity and selectivity of the analogues and to direct the synthetic design strategy to provide access to solvent-exposed regions. Thus, we have identified a point of substitution for the attachment of solubilizing groups to enhance both aqueous solubility and physicochemical properties, maintaining potent interactions with the A(2A) AR and, in some cases, receptor subtype selectivity. Among the most potent and selective novel compounds were a long-chain ether-containing amine congener 20 (K(i) 11.5 nM) and its urethane-protected derivative 14 (K(i) 17.8 nM). Compounds 20 and 31 (K(i) 11.5 and 16.9 nM, respectively) were readily water-soluble up to 10 mM. The analogues were docked in the crystallographic structure of the hA(2A) AR and in a homology model of the hA(3) AR, and the per residue electrostatic and hydrophobic contributions to the binding were assessed and stabilizing factors were proposed.

Impaired Induction of the Apoptosis-Protective Protein Bcl-xL in Activated PBMC from Asymptomatic HIV-Infected Individuals

Progression to AIDS in asymptomatic HIV-infected individuals is characterized by a gradual but progressive loss of CD4+ T cells. While the mechanisms underlying this decline are currently unknown, recent evidence suggests that these cells are abnormally sensitive to apoptosis in response to activation signals. Recent work has implicated downregulation of Bcl-2 with the increased spontaneous apoptosis in lymphocytes from HIV-infected patients. We have evaluated the roles of the apoptosis-protective proteins Bcl-2 and Bcl-x in stimulated PBMC from asymptomatic HIV-infected and HIV-uninfected individuals. We found that Bcl-2 was constitutively expressed in PBMC from both HIV-infected and uninfected samples. However, Bcl-x induction was delayed and responses were decreased in stimulated HIV-infected samples. Additionally, single-cell intracellular staining of Bcl-x revealed a significant inverse correlation between PWM-induced Bcl-x expression and apoptosis (r = −0.695, P = 0.005). This was confirmed at the single-cell level in direct experiments when stimulated cells were sorted based on Bcl-x induction and then measured for apoptosis. Furthermore, low Bcl-x expression was not due to reduced lymphocyte activation following PWM stimulation. Our data indicate that the induction of Bcl-x is markedly impaired in asymptomatic HIV-infected patients and that stimuli which induce inadequate expression of Bcl-x are associated with increased levels of apoptosis in these cells.

The T cell antigen receptor: biochemical aspects of signal transduction.

Abstract : As of 1984 there had been many examples of ligand-induced receptor phosphorylation. For example, serine phosphorylation of the beta-adrenergic receptor induced by ligand had been demonstrated and related to receptor desensitization. Tyrosine phosphorylation of the epidermal growth factor (EGF) receptor and insulin receptors had been shown to be correlated with ligand binding and receptor kinase activation. In view of these studies pointing to the central role of protein kinase activation in receptor-induced signal transduction, we asked whether the T cell antigen receptor was phosphorylated upon antireceptor engagement. To summarize several studies we demonstrated that upon the addition of antigen, antireceptor antibody, or stimulatory anti-Thy-l antibody, the antigen receptor is rapidly phosphorylated on two subunits. The CD3 gamma chain is phosphorylated on serine residues. While the T cell receptor zeta chain is phosphorylated on tyrosine residues. The antigen-induced serine phosphorylation can be mimicked by addition of phorbol ester and is dependent on the presence of protein kinase C