Elizabeth Sinclair

T Cell Activation Is Associated with Lower CD4+ T Cell Gains in Human Immunodeficiency Virus-Infected Patients with Sustained Viral Suppression during Antiretroviral Therapy

Although T cell activation is associated with disease progression in untreated human immunodeficiency virus type 1 (HIV-1) infection, its significance in antiretroviral-treated patients is unknown. Activated (CD38(+)HLA-DR(+)) T cell counts were measured in 99 HIV-infected adults who had maintained a plasma HIV RNA level <or=1000 copies/mL for a median of 21 months while receiving antiretroviral therapy. Patients with sustained viral suppression had lower levels of T cell activation than untreated patients but higher levels than HIV-uninfected control subjects. Persistent T cell activation was associated with decreased CD4(+) T cell gains during therapy. For every 5% increase in the proportion of activated CD8(+) T cells, 35 fewer CD4(+) T cells/mm(3) were gained. Increased T cell activation was associated with shorter duration of viral suppression, hepatitis C virus coinfection, frequent low-level viremia, and lower nadir CD4(+) T cell counts. Interventions that directly target T cell activation or the determinants of activation may prove to be useful adjuvants to antiretroviral therapy.

Relationship between T Cell Activation and CD4+ T Cell Count in HIV-Seropositive Individuals with Undetectable Plasma HIV RNA Levels in the Absence of Therapy

BACKGROUND Although untreated human immunodeficiency virus (HIV)-infected patients maintaining undetectable plasma HIV RNA levels (elite controllers) have high HIV-specific immune responses, it is unclear whether they experience abnormal levels of T cell activation, potentially contributing to immunodeficiency. METHODS We compared percentages of activated (CD38(+)HLA-DR(+)) T cells between 30 elite controllers, 47 HIV-uninfected individuals, 187 HIV-infected individuals with undetectable viremia receiving antiretroviral therapy (antiretroviral therapy suppressed), and 66 untreated HIV-infected individuals with detectable viremia. Because mucosal translocation of bacterial products may contribute to T cell activation in HIV infection, we also measured plasma lipopolysaccharide (LPS) levels. RESULTS Although the median CD4(+) cell count in controllers was 727 cells/mm(3), 3 (10%) had CD4(+) cell counts <350 cells/mm(3) and 2 (7%) had acquired immunodeficiency syndrome. Controllers had higher CD4(+) and CD8(+) cell activation levels (P < .001 for both) than HIV-negative subjects and higher CD8(+) cell activation levels than the antiretroviral therapy suppressed (P = .048). In controllers, higher CD4(+) and CD8(+) T cell activation was associated with lower CD4(+) cell counts (P = .009 and P = .047). Controllers had higher LPS levels than HIV-negative subjects (P < .001), and in controllers higher LPS level was associated with higher CD8(+) T cell activation (P = .039). CONCLUSION HIV controllers have abnormally high T cell activation levels, which may contribute to progressive CD4(+) T cell loss even without measurable viremia.

Plasma Levels of Bacterial DNA Correlate with Immune Activation and the Magnitude of Immune Restoration in Persons with Antiretroviral-Treated HIV Infection

The significance of elevated plasma levels of bacterial lipopolysaccharide (LPS) in persons with chronic HIV infection remains undefined. We measured LPS levels by use of limulus lysate assay, and DNA sequences encoding bacterial ribosomal 16S RNA (16S rDNA) were assessed by quantitative polymerase chain reactions in plasma samples obtained from 242 donors. Plasma levels of 16S rDNA were significantly higher in human immunodeficiency virus (HIV)-infected subjects than in uninfected subjects, and they correlated with LPS levels. Higher levels of 16S rDNA were associated with higher levels of T cell activation and with lower levels of CD4 T cell restoration during antiretroviral therapy. Antiretroviral therapy reduces but does not fully normalize plasma levels of bacterial 16S rDNA, an index of microbial translocation from the gastrointestinal tract. High levels of 16S rDNA during therapy are strongly associated with reduced increases in the CD4(+) T lymphocyte count, irrespective of plasma HIV RNA levels. These findings are consistent with the importance of microbial translocation in immunodeficiency and T cell homeostasis in chronic HIV infection.

Use of overlapping peptide mixtures as antigens for cytokine flow cytometry

Intracellular cytokine staining and flow cytometry can be used to measure T-cell responses to defined antigens. Although CD8+ T-cell responses to soluble proteins are inefficiently detected by this approach, peptides can be used as antigens. Using overlapping peptides spanning an entire protein sequence, CD8+ T-cell responses can be detected to multiple epitopes, regardless of HLA type. In this study, overlapping peptide mixes of various lengths were compared and 15 amino acid peptides with 11 amino acid overlaps were found to stimulate both CD4+ and CD8+ T-cell responses. Such peptide mixes stimulated CD4+ T-cell responses equivalent to those observed with whole recombinant protein, while simultaneously stimulating CD8+ T-cell responses much higher than those observed with whole protein. Although 8-12 amino acid peptides produced the highest level of CD8+ T-cell responses, 15 amino acid peptides were still very effective. Peptides that were 20 amino acids in length, however, did not stimulate strong CD8+ T-cell responses at the same peptide dose. The cytokine responses to individual epitopes added up approximately to the response to the entire mix, demonstrating that large mixes can detect responses in a quantitative fashion. Unlike whole protein antigens, peptide mixes were effective at stimulating responses in both cryopreserved PBMC and blood stored for 24 h at room temperature. Thus, overlapping 15 amino acid peptide mixes may facilitate the analysis of antigen-specific CD4+ and CD8+ T-cell responses by cytokine flow cytometry, using clinical specimens that include shipped blood or cryopreserved PBMC.

Analyses and comparisons of telomerase activity and telomere length in human T and B cells: Insights for epidemiology of telomere maintenance

Telomeres are the DNA-protein complexes that protect the ends of eukaryotic chromosomes. The cellular enzyme telomerase counteracts telomere shortening by adding telomeric DNA. A growing body of literature links shorter telomere length and lower telomerase activity with various age-related diseases and earlier mortality. Thus, leukocyte telomere length (LTL) and telomerase activity are emerging both as biomarkers and contributing factors for age-related diseases. However, no clinical study has directly examined telomerase activity and telomere length in different lymphocyte subtypes isolated from the same donors, which could offer insight into the summary measure of leukocyte telomere maintenance. We report the first quantitative data in humans examining both levels of telomerase activity and telomere length in four lymphocyte subpopulations from the same donors-CD4+, CD8+CD28+ and CD8+CD28- T cells and B cells, as well as total PBMCs-in a cohort of healthy women. We found that B cells had the highest telomerase activity and longest telomere length; CD4+ T cells had slightly higher telomerase activity than CD8+CD28+ T cells, and similar telomere length. Consistent with earlier reports that CD8+CD28- T cells are replicatively senescent cells, they had the lowest telomerase activity and shortest telomere length. In addition, a higher percentage of CD8+CD28- T cells correlated with shorter total PBMC TL (r=-0.26, p=0.05). Interestingly, telomerase activities of CD4+ and CD8+CD28+ T cells from the same individual were strongly correlated (r=0.55, r<0.001), indicating possible common mechanisms for telomerase activity regulation in these two cell subtypes. These data will facilitate the understanding of leukocyte aging and its relationship to human health.

Increased carotid intima-media thickness in HIV patients is associated with increased cytomegalovirus-specific T-cell responses.

Objectives:HIV-infected subjects are at increased risk for myocardial infarction. The mechanism of this increased risk remains unclear. Since cytomegalovirus (CMV) infection has been associated with accelerated atherosclerosis in the transplant population and immune responses against CMV may be altered by HIV disease, we hypothesized that enhanced T-cell responses against CMV would be associated with increased atherosclerosis in subjects with HIV. Methods:We measured high-sensitivity C-reactive protein (hs-CRP), T-cell activation, CMV-specific T-cell responses, and carotid artery intima-media thickness (IMT) in 93 HIV-infected subjects and in 37 uninfected controls. Results:The mean age of the HIV-infected subjects was 48 years and 85 (91%) were male. The median carotid IMT was higher in the HIV-infected group compared to the uninfected group (0.95 mm versus 0.68 mm, P < 0.001). This difference remained significant after controlling for all traditional risk factors. Compared to HIV-negative controls, HIV-infected subjects had higher median levels of hs-CRP (P = 0.05), higher levels of CD4 and CD8 T-cell activation (P < 0.0001) and higher CMV-specific interferon-γ CD8 T-cell responses (P < 0.0001). CMV-specific T-cell responses, but not hs-CRP and T-cell activation, were independently associated with higher carotid IMT (P = 0.001). Conclusions:HIV-infected subjects had thicker carotid IMT compared to controls. While HIV patients also had higher T-cell activation, hs-CRP levels, and CMV-specific T-cell responses, only CMV-specific T-cell responses were independently associated with IMT. Accelerated atherosclerosis in HIV patients may be mediated by heightened CMV-induced immune responses.

Activation of HIV Transcription with Short-Course Vorinostat in HIV-Infected Patients on Suppressive Antiretroviral Therapy

Human immunodeficiency virus (HIV) persistence in latently infected resting memory CD4+ T-cells is the major barrier to HIV cure. Cellular histone deacetylases (HDACs) are important in maintaining HIV latency and histone deacetylase inhibitors (HDACi) may reverse latency by activating HIV transcription from latently infected CD4+ T-cells. We performed a single arm, open label, proof-of-concept study in which vorinostat, a pan-HDACi, was administered 400 mg orally once daily for 14 days to 20 HIV-infected individuals on suppressive antiretroviral therapy (ART). The primary endpoint was change in cell associated unspliced (CA-US) HIV RNA in total CD4+ T-cells from blood at day 14. The study is registered at ClinicalTrials.gov (NCT01365065). Vorinostat was safe and well tolerated and there were no dose modifications or study drug discontinuations. CA-US HIV RNA in blood increased significantly in 18/20 patients (90%) with a median fold change from baseline to peak value of 7.4 (IQR 3.4, 9.1). CA-US RNA was significantly elevated 8 hours post drug and remained elevated 70 days after last dose. Significant early changes in expression of genes associated with chromatin remodeling and activation of HIV transcription correlated with the magnitude of increased CA-US HIV RNA. There were no statistically significant changes in plasma HIV RNA, concentration of HIV DNA, integrated DNA, inducible virus in CD4+ T-cells or markers of T-cell activation. Vorinostat induced a significant and sustained increase in HIV transcription from latency in the majority of HIV-infected patients. However, additional interventions will be needed to efficiently induce virus production and ultimately eliminate latently infected cells. Trial Registration ClinicalTrials.gov NCT01365065

Phenotypic, Functional, and Kinetic Parameters Associated with Apparent T-Cell Control of Human Immunodeficiency Virus Replication in Individuals with and without Antiretroviral Treatment

ABSTRACT The human immunodeficiency virus (HIV)-mediated immune response may be beneficial or harmful, depending on the balance between expansion of HIV-specific T cells and the level of generalized immune activation. The current study utilizes multicolor cytokine flow cytometry to study HIV-specific T cells and T-cell activation in 179 chronically infected individuals at various stages of HIV disease, including those with low-level viremia in the absence of therapy (“controllers”), low-level drug-resistant viremia in the presence of therapy (partial controllers on antiretroviral therapy [PCAT]), and high-level viremia (“noncontrollers”). Compared to noncontrollers, controllers exhibited higher frequencies of HIV-specific interleukin-2-positive gamma interferon-positive (IL-2+ IFN-γ+) CD4+ T cells. The presence of HIV-specific CD4+ IL-2+ T cells was associated with low levels of proliferating T cells within the less-differentiated T-cell subpopulations (defined by CD45RA, CCR7, CD27, and CD28). Despite prior history of progressive disease, PCAT patients exhibited many immunologic characteristics seen in controllers, including high frequencies of IL-2+ IFN-γ+ CD4+ T cells. Measures of immune activation were lower in all CD8+ T-cell subsets in controllers and PCAT compared to noncontrollers. Thus, control of HIV replication is associated with high levels of HIV-specific IL-2+ and IFN-γ+ CD4+ T cells and low levels of T-cell activation. This immunologic state is one where the host responds to HIV by expanding but not exhausting HIV-specific T cells while maintaining a relatively quiescent immune system. Despite a history of advanced HIV disease, a subset of individuals with multidrug-resistant HIV exhibit an immunologic profile comparable to that of controllers, suggesting that functional immunity can be reconstituted with partially suppressive highly active antiretroviral therapy.

T Cell Activation and Senescence Predict Subclinical Carotid Artery Disease in HIV-Infected Women

Background. Individuals infected with human immunodeficiency virus (HIV) have increased risk of cardiovascular events. It is unknown whether T cell activation and senescence, 2 immunologic sequelae of HIV infection, are associated with vascular disease among HIV-infected adults. Methods. T cell phenotyping and carotid ultrasound were assessed among 115 HIV-infected women and 43 age- and race/ethnicity-matched HIV-uninfected controls participating in the Womens Interagency HIV Study. Multivariate analyses were used to assess the association of T cell activation (CD38+HLA-DR+) and senescence (CD28−CD57+) with subclinical carotid artery disease. Results. Compared with HIV-uninfected women, frequencies of CD4+CD38+HLA-DR+, CD8+CD38+HLA-DR+, and CD8+CD28−CD57+ T cells were higher among HIV-infected women, including those who achieved viral suppression while receiving antiretroviral treatment. Among HIV-infected women, adjusted for age, antiretroviral medications, and viral load, higher frequencies of activated CD4+ and CD8+ T cells and immunosenescent CD8+ T cells were associated with increased prevalence of carotid artery lesions (prevalence ratiolesions associated with activated CD4+ T cells, 1.6 per SD [95% confidence interval {CI}, 1.1–2.2]; P = .02; prevalence ratiolesions associated with activated CD8+ T cells, 2.0 per SD [95% CI, 1.2–3.3]; P < .01; prevalence ratiolesions associated with senescent CD8+ T cells, 1.9 per SD [95% CI, 1.1–3.1]; P = .01). Conclusions. HIV-associated T cell changes are associated with subclinical carotid artery abnormalities, which may be observed even among those patients achieving viral suppression with effective antiretroviral therapy.

Valganciclovir Reduces T Cell Activation in HIV-Infected Individuals With Incomplete CD4+ T Cell Recovery on Antiretroviral Therapy

BACKGROUND Elevated immune activation persists during treated human immunodeficiency virus (HIV) infection and is associated with blunted CD4 recovery and premature mortality, but its causes remain incompletely characterized. We hypothesized that asymptomatic cytomegalovirus (CMV) replication might contribute to immune activation in this setting. METHODS Thirty antiretroviral therapy-treated HIV-infected CMV-seropositive participants with CD4 counts <350 cells/mm(3) were randomized to receive valganciclovir 900 mg daily or placebo for 8 weeks, followed by an additional 4-week observation period. The primary outcome was the week 8 change in percentage of activated (CD38(+) HLA-DR(+)) CD8(+) T cells. RESULTS Fourteen participants were randomized to valganciclovir and 16 to placebo. Most participants (21 [70%] of 30) had plasma HIV RNA levels <75 copies/mL. The median CD4 count was 190 (IQR: 134-232) cells/mm(3), and 12 (40%) of 30 had detectable CMV DNA in saliva, plasma, or semen at baseline. CMV DNA continued to be detectable at weeks 4-12 in 7 (44%) of 16 placebo-treated participants, but in none of the valganciclovir-treated participants (P = .007). Valganciclovir-treated participants had significantly greater reductions in CD8 activation at weeks 8 (P = .03) and 12 (P = .02) than did placebo-treated participants. These trends were significant even among those with undetectable plasma HIV RNA levels. CONCLUSIONS CMV (and/or other herpesvirus) replication is a significant cause of immune activation in HIV-infected individuals with incomplete antiretroviral therapy-mediated CD4(+) T cell recovery. CLINICAL TRIALS REGISTRATION NCT00264290.