Genetically associated CD16(+)56(-) natural killer cell interferon (IFN)-αR expression regulates signaling and is implicated in IFN-α-induced hepatitis C virus decline.

Background: Natural killer (NK) cells likely contribute to outcome of acute hepatitis C virus (HCV) infection and interferon (IFN)-induced control of chronic HCV infection. We previously observed IFN-αR and NKp30 expression associated with IFN-α-dependent NK cell activity.

Methods: Here, we examined CD16(+)56(-), CD16(+)56(+), and CD16(-)56(+) NK cell subset IFN-αR and NKp30 expression in relation to magnitude of HCV genotype 1 decrease during pegylated IFN-α plus ribavirin therapy.

Dissecting the T Cell Response: Proliferation Assays vs. Cytokine Signatures by ELISPOT.

Chronic allograft rejection is in part mediated by host T cells that recognize allogeneic antigens on transplanted tissue. One factor that determines the outcome of a T cell response is clonal size, while another is the effector quality. Studies of alloimmune predictors of transplant graft survival have most commonly focused on only one measure of the alloimmune response.

Systemic immune activation in HIV infection is associated with decreased MDC responsiveness to TLR ligand and inability to activate naive CD4 T-cells.

Background: HIV infection is characterized by ineffective anti-viral T-cell responses and impaired dendritic cell (DC) functions, including response to Toll-Like Receptor (TLR) ligands. Because TLR responsiveness may affect a host's response to virus, we examined TLR ligand induced Myeloid and Plasmacytoid DC (MDC and PDC) activation of naïve T-cells in HIV+ subjects.

Methods: Freshly purified MDC and PDC obtained from HIV+ subjects and healthy controls were cultured in the presence and absence of TLR ligands (poly I∶C or R-848).

Reduced naive CD4 T cell numbers and impaired induction of CD27 in response to T cell receptor stimulation reflect a state of immune activation in chronic hepatitis C virus infection.

Background: Chronic hepatitis C virus (HCV) infection is characterized by reduced numbers of functional HCV-specific T cells. In addition, chronically HCV-infected individuals have reduced response to vaccine. Alterations in naive CD4 T cell phenotype or function may contribute to these immune impairments.

Impaired plasmacytoid dendritic cell (PDC)-NK cell activity in viremic human immunodeficiency virus infection attributable to impairments in both PDC and NK cell function.

Human immunodeficiency virus (HIV) and hepatitis C virus (HCV) infections impair plasmacytoid dendritic cell (PDC) and natural killer (NK) cell subset numbers and functions, though little is known about PDC-NK cell interactions during these infections. We evaluated PDC-dependent NK cell killing and gamma interferon (IFN-gamma) and granzyme B production, using peripheral blood mononuclear cell (PBMC)-based and purified cell assays of samples from HCV- and HIV-infected subjects. CpG-enhanced PBMC killing and IFN-gamma and granzyme B activity (dependent on PDC and NK cells) were impaired in viremic HIV infection.

Differential effects of hepatitis C virus JFH1 on human myeloid and plasmacytoid dendritic cells.

Dendritic cells (DCs) are reported to be functionally deficient during chronic hepatitis C virus (HCV) infection. Differing results have been reported on direct effects of intact replicative-form HCV on DC function. To better understand the effect of HCV on DC function, we treated freshly purified human myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) with HCV JFH1.

Accessory cell dependent NK cell mediated PBMC IFN-gamma production is defective in HIV infection.

HCV and HIV infections impair dendritic cell function. We evaluated the impact of HCV, HIV, and HCV-HIV infection on MDC-NK interactions by analyzing CD3 depleted PBMC for NK cell IFN-gamma in response to IL-12 or poly (I:C). Purified MDC and NK cells were analyzed for TLR ligand-dependent, MDC-dependent NK activity.

TLR ligand-dependent activation of naive CD4 T cells by plasmacytoid dendritic cells is impaired in hepatitis C virus infection.

Chronic hepatitis C virus (HCV) infection is characterized by diminished numbers and function of HCV-reactive T cells and impaired responses to immunization. Because host response to viral infection likely involves TLR signaling, we examined whether chronic HCV infection impairs APC response to TLR ligand and contributes to the origin of dysfunctional T cells. Freshly purified myeloid dendritic cells (MDC) and plasmacytoid DC (PDC) obtained from subjects with chronic HCV infection and healthy controls were exposed to TLR ligands (poly(I:C), R-848, or CpG), in the presence or absence of cytokine (TNF-alpha or IL-3), and examined for indices of maturation and for their ability to activate allogeneic naive CD4 T cells to proliferate and secrete IFN-gamma.

HIV coinfection impairs CD28-mediated costimulation of hepatitis C virus-specific CD8 cells.

Background: During human immunodeficiency virus (HIV) infection, reduced proportions of CD8 cells express CD28, the key costimulatory molecule for lymphocyte activation. However, it is unclear whether reduced CD28 expression affects immune responses to non-HIV antigens, potentially contributing to susceptibility to opportunistic infection.

Methods: We measured CD4- and CD8-specific interferon- gamma responses to hepatitis C virus (HCV) peptide pools in subjects with chronic HCV monoinfection (n=14), in subjects with chronic HCV/HIV coinfection (n=15), and in healthy control subjects (n=10) by enzyme-linked immunospot assay in the presence and absence of CD28 costimulation.

Phenotypic and functional analysis of EBV-specific memory CD8 cells in SLE.

T cell dysfunction has been described in systemic lupus erythematosus (SLE). However, the specific phenotype and function of antigen-specific CD8 cells is less clear. Here we determined phenotype and function of Epstein-Barr virus (EBV)-specific CD8 cells at the single-cell level in SLE.

Selective impairments in dendritic cell-associated function distinguish hepatitis C virus and HIV infection.

Impaired APC functions may play important roles in chronicity of hepatitis C virus (HCV) and HIV infections. To investigate the separate and combined effects of HCV and HIV infection on immature dendritic cells (DCs), we evaluated myeloid-derived DC (MDC) and plasmacytoid-derived DC (PDC) frequencies and functions, measured by Toll-like receptor ligand-induced IFN-alpha and IL-12, in healthy controls and subjects with chronic HCV, HIV, and HCV-HIV infection. To evaluate the relation between innate and adaptive immunity, we measured HCV-specific IFN-gamma-producing T cell frequency.

CD28 costimulation enhances the sensitivity of the ELISPOT assay for detection of antigen-specific memory effector CD4 and CD8 cell populations in human diseases.

The frequencies of antigen-specific memory cells are often low in chronic disease states related to infection and autoimmunity, making detection of such populations difficult, even with high sensitivity assays such as the cytokine enzyme-linked immunospot (ELISPOT). The spectrum and function of antigen presenting cells (APC) in the peripheral compartment can differ considerably from the inflamed target organ. In order to approximate the costimulatory environment of the target organ, we measured T cell responses with and without the addition of agonistic anti-CD28 antibody in the ELISPOT assay.