TIGIT Marks Exhausted T Cells, Correlates with Disease Progression, and Serves as a Target for Immune Restoration in HIV and SIV Infection.

HIV infection induces phenotypic and functional changes to CD8+ T cells defined by the coordinated upregulation of a series of negative checkpoint receptors that eventually result in T cell exhaustion and failure to control viral replication. We report that effector CD8+ T cells during HIV infection in blood and SIV infection in lymphoid tissue exhibit higher levels of the negative checkpoint receptor TIGIT. Increased frequencies of TIGIT+ and TIGIT+ PD-1+ CD8+ T cells correlated with parameters of HIV and SIV disease progression. TIGIT remained elevated despite viral suppression in those with either pharmacological antiretroviral control or immunologically in elite controllers. HIV and SIV-specific CD8+ T cells were dysfunctional and expressed high levels of TIGIT and PD-1. Ex-vivo single or combinational antibody blockade of TIGIT and/or PD-L1 restored viral-specific CD8+ T cell effector responses. The frequency of TIGIT+ CD4+ T cells correlated with the CD4+ T cell total HIV DNA. These findings identify TIGIT as a novel marker of dysfunctional HIV-specific T cells and suggest TIGIT along with other checkpoint receptors may be novel curative HIV targets to reverse T cell exhaustion

CEACAM1 regulates TIM-3-mediated tolerance and exhaustion

T-cell immunoglobulin domain and mucin domain-3 (TIM-3, also known as HAVCR2) is an activation-induced inhibitory molecule involved in tolerance and shown to induce T-cell exhaustion in chronic viral infection and cancers[superscript 1, 2, 3, 4, 5]. Under some conditions, TIM-3 expression has also been shown to be stimulatory. Considering that TIM-3, like cytotoxic T lymphocyte antigen 4 (CTLA-4) and programmed death 1 (PD-1), is being targeted for cancer immunotherapy, it is important to identify the circumstances under which TIM-3 can inhibit and activate T-cell responses. Here we show that TIM-3 is co-expressed and forms a heterodimer with carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1), another well-known molecule expressed on activated T cells and involved in T-cell inhibition[superscript 6, 7, 8, 9, 10]. Biochemical, biophysical and X-ray crystallography studies show that the membrane-distal immunoglobulin-variable (IgV)-like amino-terminal domain of each is crucial to these interactions. The presence of CEACAM1 endows TIM-3 with inhibitory function. CEACAM1 facilitates the maturation and cell surface expression of TIM-3 by forming a heterodimeric interaction in cis through the highly related membrane-distal N-terminal domains of each molecule. CEACAM1 and TIM-3 also bind in trans through their N-terminal domains. Both cis and trans interactions between CEACAM1 and TIM-3 determine the tolerance-inducing function of TIM-3. In a mouse adoptive transfer colitis model, CEACAM1-deficient T cells are hyper-inflammatory with reduced cell surface expression of TIM-3 and regulatory cytokines, and this is restored by T-cell-specific CEACAM1 expression. During chronic viral infection and in a tumour environment, CEACAM1 and TIM-3 mark exhausted T cells. Co-blockade of CEACAM1 and TIM-3 leads to enhancement of anti-tumour immune responses with improved elimination of tumours in mouse colorectal cancer models. Thus, CEACAM1 serves as a heterophilic ligand for TIM-3 that is required for its ability to mediate T-cell inhibition, and this interaction has a crucial role in regulating autoimmunity and anti-tumour immunity.American Association for Cancer Research. Pancreatic Cancer Action Networ

Elucidating Tim-3 Function and Regulation in Human CD8+ T cells

Chronic HIV infection results in a loss of HIV-specific CD8+ T cell effector function, termed "exhaustion", which contributes to loss of viral control and progression to AIDS. This exhaustion is driven, in part, by membrane co-inhibitory receptors, including PD-1 and Tim-3, which act to dampen T cell effector function. These receptors are active targets for therapeutic blockade to rescue T cell responses in the context of HIV and cancer. Unlike PD-1, the mechanisms responsible for Tim-3-mediated inhibition of T cell responses are poorly defined, and evidence suggests that Tim-3 can act as a co-stimulatory molecule. My thesis work evaluated the role of Tim-3 at the immunological synapse, confirmed binding to the proximal signaling molecule Lck, and receptor phosphatase CD45 via the Tim-3 ligand, galectin-9. The nature of CD45-mediated regulation of Lck function suggests differential association with CD45 as a possible mechanism to explain Tim-3's opposing functions. Indeed, despite Tim-3 expression on CD45RA+ and CD45RA- T cells, Tim-3 expression on functional T cells was exclusive to the CD45RA- subset. Further, engaging Tim-3 on CD45RA- T cells resulted in co-stimulation. Finally, Tim-3 is shed from the surface of antigen-responsive T cells by matrix metalloproteinase, ADAM10, and shedding is associated with the functional capacity of T cells after TCR engagement. These results suggest that Tim-3 function is dependent on T cell phenotype, and that CD45 isoforms may differentially regulate Tim-3 function via Lck. Further, the fact that functional T cells shed Tim-3 suggests that Tim-3 does not block proximal TCR signaling. I propose that during states of chronic antigenic stimulation Tim-3 may prevent exhaustion by acting as a co-stimulator on activated CD45RA- virus-specific CD8+ T cells, however, during late differentiation, Tim-3 may enhance the negative effects of CD45RA on TCR signaling and contribute to the exhausted phenotype.Ph.D.2018-03-22 00:00:0

The Genomic and Morphological Effects of Bisphenol A on Arabidopsis thaliana.

The environmental toxin bisphenol A (BPA) is a known mammalian hormone disrupter but its effects on plants have not been well established. The effect of BPA on gene expression in Arabidopsis thaliana was determined using microarray analysis and quantitative gene PCR. Many hormone responsive genes showed changes in expression after BPA treatment. BPA disrupted flowering by a mechanism that may involve disruption of auxin signaling. The results presented here indicate that BPA is a plant hormone disrupter

Changes in <i>ACS11</i> gene expression were dependent on BPA concentration.

<p>Higher concentrations of BPA showed stronger depression of <i>ACS11</i> expression. Each bar represents pooled data from 20 pots treated with BPA daily for 28 days. Average is from 8 technical replicates (7 for the 10nM data). Error bars show standard error. * indicates p-values <0.05 when compared to 0nM BPA plants.</p

Effect of BPA on gross plant morphology.

<p>BPA had no significant effect on the number of shoots produced (A) and had a slight effect on total plant weight per jar (B). Bars represent the average of four jars of plants grown on agar containing BPA at each concentration. Error bars represent standard error. * indicates p-value <0.05 when compared to 0nM BPA treatment.</p

The effect of BPA on plant flowering.

<p>BPA may disrupt flowering in <i>A</i>. <i>thaliana</i>. Bars represent the average of four jars of plants grown on agar containing BPA at each concentration. Error bars represent standard error. * indicates p-value <0.05 when compared to 0nM BPA treatment.</p