The prognostic significance in HIV infection of immune activation represented by cell surface antigen and plasma activation marker changes

Genetic variations in the host dependency factors ALCAM and TPST2 impact HIV-1 disease progression

OBJECTIVES

Recently, the activated leukocyte cell adhesion molecule (ALCAM) and tyrosylprotein sulfotransferase 2 (TPST2) have been identified as important host dependency factors (HDFs) for in-vitro HIV-1 replication. To determine whether these genes play a role in HIV-1 pathogenesis, we analysed whether naturally occurring genetic variations were associated with the clinical course of infection.

DESIGN/METHODS

Single nucleotide polymorphisms (SNPs) in ALCAM and TPST2 were analysed in a cohort of 304 HIV-1-infected men who have sex with men and survival analysis was used to determine their effect on the outcome of untreated HIV-1 infection. Flowcytometry was used to determine the effect of SNPs on CD4 T-cell activation prior to HIV-1 infection and 1 and 5 years after infection. In-vitro HIV-1 infections were performed to analyse the effect of the SNPs on HIV-1 replication.

RESULTS

We observed that the minor allele of rs1344861 in ALCAM was associated with accelerated disease progression, whereas the minor allele of rs9613199 in TPST2 was associated with delayed disease progression. In-vitro infection assays did not demonstrate any differences in HIV-1 replication associated with rs9613199. However, the increase in CD4 T-cell immune activation levels during HIV-1 infection was less pronounced in infected individuals homozygous for rs9613199, which is in agreement with delayed disease progression.

CONCLUSION

Our data demonstrate that ALCAM and TPST2 play a role in HIV-1 pathogenesis. SNPs in these genes, without known functional implications, had a major effect on disease progression, and therefore, these HDFs may be attractive and effective targets for new treatment strategies.

Neopterin and Soluble CD14 Levels as Indicators of Immune Activation in Cases with Indeterminate Pattern and True Positive HIV-1 Infection

Background

We aimed to evaluate the roles of the plasma immune activation biomarkers neopterin and soluble CD14 (sCD14) in the indirect assessment of the immune activation status of patients with the indeterminate HIV-1 (IHIV-1) pattern and a true HIV-1-positive infection (PCG).

Methods

This cross-sectional and descriptive study included eighty-eight patients with the IHIV-1 pattern, 100 patients in the PCG, and 100 people in a healthy control group (HCG). Neopterin and sCD14 levels were determined by competitive and sandwich ELISA methods, respectively.

Results

Mean neopterin and sCD14 levels among those with the IHIV-1 pattern were significantly lower than among the PCG (p < 0.001 and p = 0.001, respectively), but they were similiar to those in the HCG (p = 0.57 and p = 0.66, respectively. Mean neopterin and sCD14 levels among the PCG were found to be significantly higher than among those with the IHIV-1 pattern (p < 0.001 and p = 0.001, respectively) and among those in the HCG (p = 0.001, p < 0.001, respectively). Neopterin did not have adequate predictive value for identifying those in the PCG (area under the curve [AUC] = 0.534; 95% CI, 0.463–0.605; p = 0.4256); sCD14 also had poor predictive value but high specificity (100%) for identifying those in the PCG (AUC = 0.627; 95% CI, 0.556–0.694; p = 0.0036).

Conclusions

While low levels of these two biomarkers were detected among those with the IHIV-1 pattern, they were found in high levels among those in the PCG. These two markers obviously cannot be used as a sceening test because they have low sensitivies. Taken together, we suggest that neopterin and sCD14 may be helpful because they both have high specificity (92%-100%) as indirect non-specific markers for predicting the immune activation status of individuals, whether or not they have true positive HIV-1.

Neopterin in Diagnosis and Monitoring of Infectious Diseases

Neopterin is produced by activated monocytes, macrophages, and dendritic cells upon stimulation by interferon gamma produced by T-lymphocytes. Quantification of neopterin in body fluids has been achieved by standard high-performance liquid chromatography, radioimmunoassays, and enzyme-linked immunosorbent assays. Neopterin levels predict HIV-related mortality more efficiently than clinical manifestations. Successful highly active antiretroviral therapy is associated with a decrease in neopterin levels. Elevated neopterin levels were associated with hepatitis by hepatitis A, B, and C viruses. Serum neopterin levels were found to be a predictor of response to treatment of chronic HCV infection with pegylated interferon combined with ribavirin. Neopterin levels of patients with pulmonary tuberculosis were found to be higher in patients with more extensive radiological changes. Elimination of blood donors with elevated neopterin levels to reduce risk of transmission of infections with known and unknown viral pathogens has been undertaken. Neopterin measurement is hereby more cost effective but less sensitive than screening using polymerase chain reaction based assays. In conclusion neopterin is a nonspecific marker of activated T-helper cell 1 dominated immune response. It may be a useful marker for monitoring of infectious disease activity during treatment and for more accurate estimation of extent of disease and prognosis.

Cortisol patterns are associated with T cell activation in HIV

Objective

The level of T cell activation in untreated HIV disease is strongly and independently associated with risk of immunologic and clinical progression. The factors that influence the level of activation, however, are not fully defined. Since endogenous glucocorticoids are important in regulating inflammation, we sought to determine whether less optimal diurnal cortisol patterns are associated with greater T cell activation.

Methods

We studied 128 HIV-infected adults who were not on treatment and had a CD4⁺ T cell count above 250 cells/µl. We assessed T cell activation by CD38 expression using flow cytometry, and diurnal cortisol was assessed with salivary measurements.

Results

Lower waking cortisol levels correlated with greater T cell immune activation, measured by CD38 mean fluorescent intensity, on CD4⁺ T cells (r = −0.26, p = 0.006). Participants with lower waking cortisol also showed a trend toward greater activation on CD8⁺ T cells (r = −0.17, p = 0.08). A greater diurnal decline in cortisol, usually considered a healthy pattern, correlated with less CD4⁺ (r = 0.24, p = 0.018) and CD8⁺ (r = 0.24, p = 0.017) activation.

Conclusions

These data suggest that the hypothalamic-pituitary-adrenal (HPA) axis contributes to the regulation of T cell activation in HIV. This may represent an important pathway through which psychological states and the HPA axis influence progression of HIV.

Dissociation of CD154 and cytokine expression patterns in CD38+ CD4+ memory T cells in chronic HIV-1 infection

Expression of the activation antigen CD38 on T cells is a strong predictor of the risk of HIV disease progression, but it is not known whether CD38 is a marker or mediator of dysfunction. We examined the relationship between CD38 expression and responses to T-cell receptor stimulation in central memory and effector memory CD4 T cells in HIV-infected persons and in healthy controls. Basal CD38 expression was preserved by blocking golgi transport with brefeldin A. Intracellular expression of interleukin 2, interferon γ, and CD154 was measured after stimulating peripheral blood mononuclear cells with the superantigen staphylococcal enterotoxin B with or without anti-CD28 costimulation. Interferon-γ responses were comparable or increased in stimulated CD38 memory cells, and the interleukin 2 responses of costimulated CD38 central memory cells were decreased in HIV infection. In CD38 cells and especially in CD38 cells of HIV-infected persons, stimulated memory cells more often failed to express CD154 (CD40 ligand) when induced to express cytokine. A dissociated cytokine and CD154 expression by memory CD4 T cells may impair interactions between T cells and antigen-presenting cells, contribute to impaired immunity and help explain the relationship between CD38 expression and disease progression in chronic HIV infection.

Differences in HIV burden and immune activation within the gut of HIV-positive patients receiving suppressive antiretroviral therapy

BACKGROUND

The gut is a major reservoir for human immunodeficiency virus (HIV) in patients receiving antiretroviral therapy (ART). We hypothesized that distinct immune environments within the gut may support varying levels of HIV.

METHODS

In 8 HIV-1-positive adults who were receiving ART and had CD4(+) T cell counts of >200 cells/μL and plasma viral loads of <40 copies/mL, levels of HIV and T cell activation were measured in blood samples and endoscopic biopsy specimens from the duodenum, ileum, ascending colon, and rectum.

RESULTS

HIV DNA and RNA levels per CD4(+) T cell were higher in all 4 gut sites compared with those in the blood. HIV DNA levels increased from the duodenum to the rectum, whereas the median HIV RNA level peaked in the ileum. HIV DNA levels correlated positively with T cell activation markers in peripheral blood mononuclear cells (PBMCs) but negatively with T cell activation markers in the gut. Multiply spliced RNA was infrequently detected in gut, and ratios of unspliced RNA to DNA were lower in the colon and rectum than in PBMCs, which reflects paradoxically low HIV transcription, given the higher level of T cell activation in the gut.

CONCLUSIONS

HIV DNA and RNA are both concentrated in the gut, but the inverse relationship between HIV DNA levels and T cell activation in the gut and the paradoxically low levels of HIV expression in the large bowel suggest that different processes drive HIV persistence in the blood and gut.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00884793 (PLUS1).

Early changes in T-cell activation predict antiretroviral success in salvage therapy of HIV infection

OBJECTIVE

Because effective antiretroviral therapy (ART) reduces immune activation, we hypothesize that early changes in immune activation are associated with subsequent virologic response to therapy.

DESIGN

Observational cohort study.

SETTING

Institutional HIV clinic.

SUBJECTS

Thirty-four adult HIV patients with virologic failure on their current antiretroviral regimen.

INTERVENTION

Change to salvage regimen selected by patient's physician.

MAIN OUTCOME MEASURES

Measures of immune activation at baseline and at 2, 4, 8, and 24 weeks after enrollment. Data were analyzed by proportional hazards (PH) models.

RESULTS

PH models showed that reductions between baseline and week 2 in expression of CD38 (P = 0.02) or CD95 (P = 0.02) on CD4 T cells were associated with increased likelihood of achieving virologic suppression. Kaplan-Meier analysis demonstrated that patients who had reductions within the first 2 weeks of therapy in CD4 T-cell expression of CD38 (P = 0.003) or CD95 (P = 0.08) were more likely to achieve viral suppression than those who did not.

CONCLUSIONS

Reduced CD4 T-cell expression of CD38 and CD95 occurring within 2 weeks of salvage therapy is associated with subsequent viral suppression. Monitoring CD38 and CD95 may allow earlier assessment of the response to ART.

Slow disease progression and robust therapy-mediated CD4+ T-cell recovery are associated with efficient thymopoiesis during HIV-1 infection

In chronic HIV infection, most untreated patients lose naive CD4+ and CD8+ T cells, whereas a minority preserve them despite persistent high viremia. Although antiretroviral therapy (ART)–mediated viral suppression generally results in a rise of naive and total CD4+ T cells, certain patients experience very little or no T-cell reconstitution. High peripheral T-cell activation has been linked to poor clinical outcomes, interfering with previous evaluations of thymic function in disease progression and therapy-mediated T-cell recovery. To circumvent this, we used the sj/βTREC ratio, a robust index of thymopoiesis that is independent of peripheral T-cell proliferation, to evaluate the thymic contribution to the preservation and restoration of naive CD4+ T cells. We show that the loss of naive and total CD4+ T cells is the result of or is exacerbated by a sustained thymic defect, whereas efficient thymopoiesis supports naive and total CD4+ T-cell maintenance in slow progressor patients. In ART-treated patients, CD4+ T-cell recovery was associated with the normalization of thymopoiesis, whereas the thymic defect persisted in aviremic patients who failed to recover CD4+ T-cell counts. Overall, we demonstrate that efficient thymopoiesis is key in the natural maintenance and in therapy-mediated recovery of naive and total CD4+ T cells.

Cardiac isoform of alpha 2 macroglobulin, an early diagnostic marker for cardiac manifestations in AIDS patients

This study investigated the possible role of the cardiac isoform of alpha 2-macroglobulin (CA2M) as an early diagnostic marker for HIV-associated cardiovascular manifestations. A total of 349 samples were analysed by Western blot and quantified by sandwich enzyme-linked immunosorbent assay. The levels of CA2M present in sera of HIV-associated cardiac diseases were significantly higher than those of HIV without cardiac involvement and healthy sera. CA2M may act as a novel diagnostic marker to identify cardiac manifestations in HIV/AIDS patients.

Persistent anti-gag, -Nef, and -Rev IgM levels as markers of the impaired functions of CD4+ T-helper lymphocytes during SIVmac251 infection of cynomolgus macaques

This study analyzed the antigen-specific (Gag, Nef, Rev, and Tat) IgM, IgG, and IgA humoral responses during the first 200 days of SIVmac251 infection in cynomolgus macaques. These responses were tested for correlation with the CD4(+) T-cell-related hematologic parameters and viral load throughout the course of the study (acute and chronic infection, during and after antiretroviral therapy). Strong inverse correlations were observed between the percentage of CD4(+) T cells at almost every timepoint of the study and the levels of IgM (but not IgG and IgA) against Gag, Nef, and Rev (but not Tat) measured after, but not during, the primary peak of IgM response. Significant levels of persistent antigen-specific IgMs may reflect the prevalence of mature plasma cells that have not undergone immunoglobulin class switching, possibly due to defects in helper T-cell function. Strong correlations were observed between the preinfection CD4(+) T-cell count or CD4/CD8 ratio and the same parameters measured throughout the study, suggesting the importance of preinfection immune status as a determinant of disease progression. The negative correlations between the post-acute-phase IgM levels and the percentage of CD4(+) T cells at later times during the study suggest the potential prognostic value of this measurement.

Serum Neopterin, an Immune Activation Marker, Independently Predicts Disease Progression in Advanced HIV-1 Infection

BACKGROUND

CD4+ T lymphocyte (CD4) counts and plasma human immunodeficiency virus (HIV) type 1 RNA concentrations predict clinical outcome in HIV-1 infection. Our objective was to assess the independent prognostic value for disease progression of soluble markers of immune system activation.

METHODS

This retrospective marker-validation study utilized previously obtained clinical and laboratory data, including CD4+ cell counts, and made use of stored frozen serum samples to assay for levels of beta2-microglobulin, neopterin, endogenous interferon, triglycerides, interleukin-6, soluble tumor necrosis factor- alpha receptor II, and HIV-1 RNA, and to determine HIV genotypic reverse-transcriptase inhibitor resistance. The 152 patients who participated in this study represented a subsample of participants in AIDS Clinical Trials Group (ACTG) 116B/117, a randomized trial that demonstrated the clinical benefit of didanosine over zidovudine monotherapy in persons with advanced HIV-1 infection. Marker data were analyzed in relation to protocol-defined clinical disease progression, using Cox proportional hazards models.

RESULTS

The median duration of follow-up was 344 days. Elevated baseline values for neopterin (P=.0009), endogenous interferon (P=.00039) and interleukin-6 (P=.0007) were each associated with greater subsequent risk of clinical disease progression. In a head-to-head comparison that was adjusted for CD4+ cell count (P=.0165) and HIV-1 RNA level (P=.1220), we found that elevated values for neopterin (P=.0002) and, to a lesser extent, endogenous interferon (P=.0053) were the strongest predictors of increased risk of clinical disease progression 6 months later.

CONCLUSIONS

Soluble markers of immune activation add prognostic information to CD4 counts and viral load for risk of disease progression in advanced HIV-1 infection. The robust performance of neopterin, an inexpensive and reliably measured serum marker, supports its potential suitability for patient monitoring, particularly in resource-limited settings.

Isolation of peripheral blood CD4(+) T cells using RosetteSep and MACS for studies of DNA turnover by deuterium labeling

Tracking deuterium ((2)H) incorporation into cellular DNA, after administration of (2)H(2)O or (2)H(2)-glucose, is a recently developed, broadly applicable method for measuring in vivo cell proliferation and turnover that can be used safely in humans. This approach has been used to evaluate the turnover of T-cell subpopulations purified from the peripheral blood of HIV-1-infected patients using fluorescence-activated cell sorting (FACS). A requirement for widespread adoption of this approach for medical decision-making and for use in larger clinical trials is a simple, reproducible, high-throughput method for isolation of highly purified CD4(+) T cells from peripheral blood. Here, we present a simple method, which does not require FACS, for isolating these cells in sufficient purity and yield for analysis of (2)H incorporation into DNA. When blood from HIV-1-infected patients was used, neither the depletion of unwanted cell lineages by erythrocyte crosslinking (RosetteSep) nor the enrichment of CD4(+) cells by immunomagnetic beads (MACS) individually resulted in sufficient purity. The successive application of the two techniques, however, permitted isolation of >95% pure CD4(+) T cells in adequate yield (>10(6) cells/10 ml blood) from healthy donors and HIV-1-infected patients with CD4 counts between 300 and 700 cells/microl. Moreover, (2)H incorporation into cellular DNA after administration of (2)H(2)O to HIV-1-infected patients was indistinguishable between CD4(+) T cells isolated by RosetteSep/MACS and FACS. Thus, both FACS and the new method isolate a similar mixture of long- and short-lived CD4(+) T cells. In practice, the RosetteSep/MACS method is simple, rapid, robust and capable of high throughput.

Persistent immune activation in HIV-1 infection is associated with progression to AIDS

BACKGROUND

HIV-1 infection is characterized by chronic generalized CD8 and CD4 T cell hyperactivation, the biological effect of which is not understood.

OBJECTIVE

To study the relation between chronic immune activation and CD4 T cell depletion in HIV-1 infection.

DESIGN

Prospective cohort study among participants of the Amsterdam Cohort Studies on HIV-1 infection and AIDS who have a known seroconversion date (n = 102).

METHODS

CD4 and CD8 T cell activation marker expression was analysed by FACScan before and after seroconversion (1 and 5 years after seroconversion); T cell proliferation and T cell numbers were also measured. Cox proportional hazard analyses were used to study the predictive value of these parameters for progression to AIDS.

RESULTS

Preseroconversion low CD4 T cell numbers or elevated levels of CD4 T cell activation were associated with increased risk for development of AIDS after HIV-1 seroconversion. Progression to AIDS was associated with loss of both CD4 and CD8 naive T cells. The predictive value of CD8 T cell activation was confirmed and, in addition, in the course of infection low CD4 T cell counts and increasing proportions of dividing CD4 T cells, dividing CD8 T cells or elevated CD4 T cell activation marker expression became independent predictors of progression to AIDS.

CONCLUSIONS

Increased T cell activation has predictive value for HIV-1 disease progression even before seroconversion. These data support the hypothesis that persistent hyperactivation of the immune system may lead to erosion of the naive T cell pool and CD4 T cell depletion.

Can immune markers predict subsequent discordance between immunologic and virologic responses to antiretroviral therapy? Adult AIDS Clinical Trials Group

It is unclear why discordant immunologic and virologic responses occur during therapy for human immunodeficiency virus (HIV) infection. This study examined whether markers of immune activation and naive/memory lymphocyte subsets at study baseline could predict discordance between HIV type 1 (HIV-1) RNA and CD4+ lymphocyte responses at week 24 of antiretroviral therapy. Ten diverse, prospective antiretroviral studies with 1007 evaluable subjects were included. Subsets of subjects at increased risk for discordance were identified by recursive partitioning. The strongest predictor of more-favorable immunologic than virologic responses was a lower baseline CD4+ lymphocyte count. Weaker predictors in small subsets of subjects were fewer activated CD4+ lymphocytes and fewer CD8+ lymphocytes. Conversely, the strongest predictors of more-favorable virologic than immunologic responses were higher baseline CD4+ lymphocyte count and percentage. Additional predictors in some analyses were higher CD8+ lymphocyte count or percentage and lower HIV-1 RNA concentrations. Baseline markers of immune activation and naive/memory lymphocyte subsets had limited ability to predict subsequent discordance.

Effects of an exercise intervention on immunologic parameters in frail elderly nursing home residents

BACKGROUND

Aging is associated with decline in both cell-mediated and humoral immunity and may contribute to increased incidence and severity of infections in frail elderly. Exercise, depending on intensity, has significant effects on the immune system. We conducted a randomized, controlled clinical trial of a 32-week functionally oriented exercise program in frail elderly living in nursing homes and determined whether the exercise intervention was associated with a change in immune parameters in this frail elderly nursing home population.

METHODS

Nursing home residents were randomly assigned to an intervention (n = 94) and control group (n = 96). The intervention consisted of a functionally oriented endurance and resistance exercise training that was provided every 2 hours from 8:00 AM to 4:00 PM for 5 days a week for 8 months. Lymphocyte subpopulations, including activation markers (CD28, CD25, HLA-DR), in vitro proliferation, and soluble products of cytokine activity (neopterin and sTNF-RII) in serum were measured by taking blood samples at baseline and after 8 weeks and 32 weeks of the intervention.

RESULTS

Exercise training did not induce changes in lymphocyte subpopulations, activation markers (CD28, CD25, HLA-DR), in vitro proliferation, and soluble products of cytokine activity (neopterin and sTNF-RII) in serum.

CONCLUSIONS

A 32-week exercise intervention did not bring about beneficial or detrimental effects on immune parameters in the frail elderly nursing home population and may explain why the intervention was not associated with a change in the incidence of infections in the intervention group compared with the control group.

Deleterious effect of HIV-1 plasma viremia on B cell costimulatory function

HIV infection leads to numerous immunologic defects, including impaired B cell function. An effective humoral response requires bidirectional interactions between B cells and CD4(+) T cells, critical of which are interactions between CD80/CD86 expressed on activated B cells and CD28 expressed on responder CD4(+) T cells. In the present study, we examined the effect of active HIV replication on B cell costimulatory function. Induction of CD80/CD86 on B cells following B cell receptor and CD40 triggering and responsiveness of CD4(+) T cells to activated B cells were investigated in a system where B cells of HIV-infected patients were compared concurrently to B cells of HIV-negative donors. In contrast to HIV-aviremic patients, B cells of HIV-viremic patients were ineffective at stimulating CD4(+) T cells, as measured by the induction of activation markers and proliferation. The importance of interactions of CD80/CD86 and CD28 in activating CD4(+) T cells was clear; the ablation of a normal response following the addition of neutralizing anti-CD86/CD80 Abs mirrored the response of CD4(+) T cells to B cells of HIV-viremic patients, while the addition of exogenous CD28 ligands partially restored the poor CD4(+) T cell response to the B cells of HIV-viremic patients. Ineffective B cell costimulatory function in HIV-viremic patients was associated with low induction of CD80/CD86 expression on B cells. Our findings further delineate the scope of defects associated with cognate B cell-CD4(+) T cell interactions in HIV infection and suggest that therapeutic interventions designed to enhance CD28-dependent costimulatory pathways may help restore immune functions.

Perturbations in B cell responsiveness to CD4+ T cell help in HIV-infected individuals

HIV infection induces a wide array of B cell dysfunctions. We have characterized the effect of plasma viremia on the responsiveness of B cells to CD4(+) T cell help in HIV-infected patients. In HIV-negative donors, B cell proliferation correlated with CD154 expression on activated CD4(+) T cells and with the availability of IL-2, whereas in HIV-infected viremic patients, reduced B cell proliferation was observed despite normal CD154 expression on activated CD4(+) T cells. Reduced triggering of B cells by activated CD4(+) T cells was clearly observed in HIV-infected viremic patients compared with aviremic patients with comparable CD4(+) T cell counts, and a dramatic improvement in B cell function was observed in patients whose plasma viremia was controlled by effective antiretroviral therapy. The degree of B cell dysfunction in viremic patients correlated strongly with the inability of B cells to express CD25 in response to activated CD4(+) T cells, resulting in an inability to mount a normal proliferative response to IL-2. Similar defects in responsiveness to IL-2 were observed in the B cells of HIV-infected viremic patients in the context of B cell receptor stimulation. These data provide new insight into the mechanisms associated with ineffective humoral responses in HIV disease.

Elevated serum levels of soluble immune activation markers are associated with increased risk for death in HAART-naive HIV-1-infected patients

The aim of this study was to determine the serum levels of soluble markers reflecting different aspects of immune activation in HIV-1-infected patients, and assess their prognostic significance for occurrence of AIDS-related death before the advent of the highly active antiretroviral treatment (HAART). Serum concentrations of the soluble forms of interleukin-2 receptors (sIL-2R), intercellular adhesion molecule-1 (sICAM-1), and E-selectin (sEs) have been determined in a cohort of 64 HIV-1-infected patients, between 1990-1993. The patients were followed prospectively with regular visits at the outpatient department. Follow-up time was censored at January 1, 1997, the date after which HAART was introduced. The median follow-up time was 46 months (range, 2-78 months). By the end of follow-up, 34 subjects had died. Baseline levels of all three soluble markers were significantly lower in subjects who remained alive during the follow-up compared to subjects who died. Univariate analysis showed that individual sIL-2R and sICAM-1, but not sEs measurements, were significantly associated with time to death (p = 0.008 and 0.003, respectively). Even after adjustment for age and CD4+ T-cell counts sIL-2R measurements remained significantly prognostic. Sensitivity analysis using follow-up time to year 2000 confirmed these results. Our data suggest that assessment of the immune activation status using the easily measured levels of circulating markers may provide additional information about the risk of AIDS-related death. Further studies are needed to assess the effect of HAART on the levels of immune activation markers and their prognostic value.

Immune activation in patients infected with HIV type 1 and maintaining suppression of viral replication by highly active antiretroviral therapy

Immune activation associated with HIV infection declines after highly active antiretroviral therapy (HAART), but may persist or recur in some patients. It is not clear whether this reflects a resurgence of HIV replication or another cause of immune activation, such as inflammatory reactions to opportunistic pathogens (immune restoration disease [IRD]). Here, we studied plasma and cellular immune activation markers in adult HIV-1 patients who had received HAART for >12 months and maintained plasma HIV RNA levels of <400 copies/ml for >6 months. Plasma interleukin 1 receptor antagonist and tumor necrosis factor receptor I levels were similar in patients and HIV-negative control subjects, but the highest levels occurred mainly in patients with a history of IRD. In contrast, expression of HLA-DR and CD38 on monocytes and of HLA-DR on CD8(+) T cells was higher in patients than in control subjects. Thus, cellular markers of immune activation are abnormal in some patients with a good virological response to HAART, and abnormalities of plasma immune activation markers correlate with a history of IRD.

Tumor necrosis factor alpha, interleukin 2, and soluble interleukin 2 receptor levels in human immunodeficiency virus type 1-infected individuals receiving intermittent cycles of interleukin 2

HIV-infected individuals with 200-500 CD4(+) T cell/microl were enrolled in a controlled study of three interleukin 2 (IL-2) plus antiretroviral therapy (ART) regimens: (1) continuous intravenous administration of 12 million international units (MIU) of IL-2 followed by subcutaneous high-dose IL-2 (7.5 MIU, twice daily) for 5 days every 8 weeks; (2) high-dose subcutaneous IL-2 for 5 days every 8 weeks; (3) low-dose (3 MIU, twice daily) subcutaneous IL-2 for 5 days every 4 weeks; and (4) ART alone. Serum concentrations of IL-2, soluble IL-2 receptor (sIL-2R), tumor necrosis factor alpha (TNF-alpha), and IL-6 were determined. A progressive decrease over time of the circulating levels of IL-2 was observed in individuals receiving the highest doses of IL-2, but not in those belonging to the low-dose arm. Conversely, increased levels of sIL-2R were observed in all cytokine-treated individuals. The levels of TNF-alpha increased in the high-dose IL-2 regimens, but decreased in individuals receiving low-dose IL-2. IL-2-related toxicity was significantly correlated to the peak IL-2 serum levels, and was substantially lower in those individuals receiving low-dose IL-2. In conclusion, intermittent IL-2 administration causes the elevation of peripheral CD4(+) T cells, but also a profound cytokine response and systemic toxicity. The latter was correlated to the peak serum level of IL-2, but not to those of TNF-alpha and IL-6.

Chronic immune activation and inflammation in the pathogenesis of AIDS and cancer

Infection with the human immunodeficiency virus (HIV) invariably leads to the development of acquired immunodeficiency syndrome (AIDS) in most infected humans, yet does so rarely, if at all, in HIV-infected chimpanzees. The differences between the two species are not due to differences in cellular receptors or an inability of the chimpanzee to be infected, but rather to the lack of pan-immune activation in the infected primate. This results in reduced apoptotic death in CD4+ T-helper lymphocytes and a lower viral load. In humans the degree of chronic immune activation correlates with virus load and clinical outcome with high immune activation leading to high viral loads and the more rapid progression to AIDS and death. The type of immune perturbation seen in HIV-associated AIDS is similar to that of chronic graft-versus-host disease (GVHD) where reduced cell-mediated immune (CMI) responses occur early in the course of the disease and where humoral responses (HI) predominate. A reduced CMI response occurs in a number of chronic infectious diseases, including tuberculosis and leishmaniasis. More recently, it has become increasingly apparent that the CMI response is suppressed in virtually all malignant diseases, including melanoma and colorectal and prostate cancer. This raises the possibility that, as the malignant process develops, the cancer cells evolve to subvert the CMI response. Moreover, the reduced CMI response seen in colorectal cancer (CRC) patients is completely reversed following curative surgery strongly supporting the hypothesis that CRC can suppress the systemic immune response. Wound healing, ovulation, embryo implantation, and fetal growth are all associated with suppressed CMI and neovascularization (the formation of new blood vessels) or angiogenesis (the formation of new blood vessels from an existing vasculature). If unresolved, wound healing results in chronic inflammation, which can give rise to the phenomenon of "scar cancers." Indeed all the chronic inflammatory conditions known to be associated with the subsequent development of malignant disease, including chronic obstructive airway disease (COPD), ulcerative colitis (UC), and asbestosis, give rise to similar proangiogenic, suppressed CMI, and HI-predominant environments. In keeping with this CMI-associated cytokines such as interleukin (IL)-2 and interferon (IFN)-gamma tend to be antiangiogenic, whereas HI cytokines such as IL-6 tend to be proangiogenic. Furthermore, chronic immune activation leads to the synthesis and release of factors such as macrophage inflammatory protein (MIP)-1 that inhibit apoptosis through suppression of p53 activity. The "Golden Triangle" of suppressed CMI, angiogenesis, and reduced apoptosis would provide the ideal environment for the serial mutations to occur that are required for the development of malignant disease. If the observed association is relevant to carcinogenesis, then treatments aimed at reducing the components of these inflammatory conditions may be useful both in the setting of chemoprevention and the therapeutic management of established disease.

Activated peripheral CD8 lymphocytes express CD4 in vivo and are targets for infection by human immunodeficiency virus type 1

There is increasing evidence that CD8 lymphocytes may represent targets for infection by human immunodeficiency virus type 1 (HIV-1) in vivo whose destruction may contribute to the loss of immune function underlying AIDS. HIV-1 may infect thymic precursor cells destined to become CD4 and CD8 lymphocytes and contribute to the numerical decline in both subsets on disease progression. There is also evidence for the induction of CD4 expression and susceptibility to infection by HIV-1 of CD8 lymphocytes activated in vitro. To investigate the relationship between CD8 activation and infection by HIV-1 in vivo, activated subsets of CD8 lymphocytes in peripheral blood mononuclear cells (PBMCs) of HIV-seropositive individuals were investigated for CD4 expression and HIV infection. Activated CD8 lymphocytes were identified by expression of CD69, CD71, and the human leukocyte antigen (HLA) class II, the beta-chain of CD8, and the RO isoform of CD45. CD4(+) and CD4(-) CD8 lymphocytes, CD4 lymphocytes, other T cells, and non-T cells were purified using paramagnetic beads, and proviral sequences were quantified by PCR using primers from the long terminal repeat region. Frequencies of activated CD8 lymphocytes were higher in HIV-infected study subjects than in seronegative controls, and they frequently coexpressed CD4 (mean frequencies on CD69(+), CD71(+), and HLA class II(+) cells of 23, 37, and 8%, respectively, compared with 1 to 2% for nonactivated CD8 lymphocytes). The level of CD4 expression of the double-positive population approached that of mature CD4 lymphocytes. That CD4 expression renders CD8 cell susceptible to infection was indicated by their high frequency of infection in vivo; infected CD4(+) CD8 lymphocytes accounted for between 3 and 72% of the total proviral load in PBMCs from five of the eight study subjects investigated, despite these cells representing a small component of the PBMC population (<3%). Combined, these findings provide evidence that antigenic stimulation of CD8 lymphocytes in vivo induces CD4 expression that renders them susceptible to HIV infection and destruction. The specific targeting of responding CD8 lymphocytes may provide a functional explanation for the previously observed impairment of cytotoxic T-lymphocyte (CTL) function disproportionate to their numerical decline in AIDS and for the deletion of specific clones of CTLs responding to HIV antigens.

Immunosuppression by CD4+ regulatory T cells induced by chronic retroviral infection

Normal levels of CD4(+) regulatory T cells are critical for the maintenance of immunological homeostasis and the prevention of autoimmune diseases. However, we now show that the expansion of CD4(+) regulatory T cells in response to a chronic viral infection can lead to immunosuppression. Mice persistently infected with Friend retrovirus develop approximately twice the normal percentage of splenic CD4(+) regulatory T cells and lose their ability to reject certain tumor transplants. The role of CD4(+) regulatory T cells was demonstrated by the transmission of immunosuppression to uninfected mice by adoptive transfers of CD4(+) T cells. CD4(+) T cells from chronically infected mice were also immunosuppressive in vitro, inhibiting the generation of cytolytic T lymphocytes in mixed lymphocyte cultures. Inhibition occurred at the level of blast-cell formation through a mechanism or mechanisms involving transforming growth factor-beta and the cell surface molecule CTLA-4 (CD152). These results suggest a possible explanation for HIV- and human T cell leukemia virus-I-induced immunosuppression in the absence of T cell depletion.

Plasma levels of viro-immunological markers in HIV-infected and non-infected Ethiopians: correlation with cell surface activation markers

Cross-sectional studies were conducted to measure soluble viral and immunological markers in plasma in order to determine the prognostic value of these markers for HIV disease progression in Ethiopians and to see their association with cell surface markers in HIV-1-infected and noninfected Ethiopians. Whole blood samples were collected from 52 HIV-1-negative Ethiopians, 32 HIV-1-positive Ethiopians with absolute CD4(+) T-cell count >200/microl whole blood and no AIDS defining conditions, and 39 HIV-positive Ethiopians with CD4(+) T-cell count <200/microl and/or AIDS defining conditions. Plasma levels of b(2)-microglobulin (b(2)m), soluble CD27 (sCD27), soluble tumor necrosis factor alpha receptor type II (sTNFR-II), IgG, IgA, IGE, and IL12 were elevated in HIV-1-infected individuals. The plasma levels of sTNFR-II, sCD27, b(2)m, IL12, and IgG were inversely correlated with numbers of CD4(+) T-cells, the proportion of naïve (CD45RA(+)CD27(+)) CD8(+) T-cells, and the proportion of CD8(+) T-cells expressing CD28 (CD8(+)CD28(+)) were positively correlated with the proportions of activated (HLA-DR(+)CD38(+)) CD4(+) T-cells, as well as activated (HLA-DR(+)CD38(+)) CD8(+) T-cells. A strong positive correlation was also observed when soluble immune markers were compared to each other. Multivariate regression analyses of soluble markers with numbers of CD4(+) T-cells showed that sCD27 is the best independent marker for CD4(+) T-cell decline in the HIV-1-infected Ethiopians. Our results indicate that measurement of soluble immune markers, which is relatively easy to perform, could be a good alternative to the quantification of T-cell subsets for monitoring HIV-1 disease progression in places where there is no facility for flow cytometric measurements.

Increased levels of activated subsets of CD4 T cells add to the prognostic value of low CD4 T cell counts in a cohort of HIV-infected drug users

OBJECTIVE

To identify subsets of CD4 T lymphocytes that can predict the development of AIDS and to assess whether increased levels of these cellular markers could provide additional independent prognostic information to the CD4 T cell count and plasma HIV-1-RNA levels.

DESIGN AND METHODS

In a prospective study, a cohort of 85 HIV-positive intravenous drug users [clinical categories of the CDC classification A (n = 48) and B (n = 37)] were followed for a period of 37+/-13 months. Memory and activated CD4 and CD8 T cells were quantitated by three-colour flow cytometry at baseline and expressed as a percentage of total CD4 and CD8 lymphocytes. Clinical evaluations were performed at 6 month intervals. The relationships between these lymphocyte subsets and progression to AIDS were studied using Kaplan-Meier plots and proportional hazards regression models.

RESULTS

After adjustment for the level of CD4 T cells and plasma HIV-1-RNA levels, the elevation in the subset CD4+CD38+DR+ was the marker within the functionally distinct subsets of CD4 T lymphocytes with additional prognostic value in bivariate Cox regression models. In multivariate models, increased percentages of CD4+CD38+DR+ T cells provided the strongest independent prognostic information for progression to AIDS (relative hazard, 1.07; P < 0.0001).

CONCLUSION

Our results suggest that high levels of CD4+CD38+HLA-DR+ T cells reflect the increasing degree of CD4 T cell activation during the progression of HIV infection, and could be used together with the CD4 T cell and HIV-RNA levels to evaluate more accurately the progressive cellular immune impairment associated with the risk of progression to AIDS.

Regeneration and tolerance factor's potential role in T-cell activation and apoptosis

Regeneration and tolerance factor (RTF) is a novel membrane protein that has a diverse expression pattern and immunoregulatory properties. RTF is expressed in vivo on the surface of individuals with B cell chronic lymphocytic leukemia and on activated T lymphocytes of HIV infected individuals as determined by their coexpression with CD38 and HLA-DR. The unique expression patterns of this protein in vivo lead us to investigate its expression in vitro. The activation of human PBMCs through the TCR, using anti-CD3 antibody and PMA, upregulated cell surface expression of RTF from 2. 3% to 91.2% (mean channel fluorescence [MCF] increased threefold). The activation of Jurkat T cells through the TCR upregulated surface expression of RTF from 8.3% (MCF-1.3) to 58.7% (MCF-13.1). The Jurkat T-cell line was used as a model system to explore RTF's role in cellular activation. Using the Jurkat T-cell model, we found anti-RTF antibody induces apoptosis. The addition of anti-RTF antibody increased annexin V binding by threefold compared with the IgG1 kappa isotype control antibody (p < 0.00002) and activated caspase 3. These data indicate that RTF is expressed during T-cell activation and may be associated with apoptosis.

Highly active antiretroviral therapy (HAART) and circulating markers of immune activation: specific effect of HAART on neopterin

The circulating levels of immune activation markers, including neopterin, tumor necrosis factor receptor type II, and interleukin-2 receptors, are increased in human immunodeficiency virus-infected patients. We show here that highly active antiretroviral therapy significantly decreased neopterin levels. This effect is reversible, since neopterin levels increased after the arrest of treatment. Their determination may be useful in the evaluation of the efficacy of antiretroviral therapy.

Expression of MHC class II in T cells is associated with increased HIV-1 expression

HIV-1 replicates in activated T cells at significantly higher levels than in resting cells. Thus, certain molecules up-regulated during T cell activation appear to be important for HIV-1 replication. In this study, we present evidence suggesting that expression of MHC class II (class II) molecules on CD4+ T cells facilitate HIV-1 replication. T cells that expressed class II supported greater virus replication than T cells lacking class II. The class II+ cells, when either infected with HIV-1 or transfected with an env-minus HIV-1 provirus plasmid, produced 10-20-fold greater virus expression than class II- cells. Anti-class II antibody markedly inhibited virus expression in class II+ cells (but not class II- cells) and also decreased the nuclear binding activity of AP-1, an inducible transcription factor important in T cell activation and HIV-1 expression. Most importantly, the induction of class II expression by transfection of the MHC class II transactivator (CIITA) stimulated HIV-1 replication in Jurkat T cells. Taken together, these data suggest that expression of MHC class II molecules and/or CIITA in T cells enhances HIV-1 transcription.

Nonradioactive techniques for measurement of in vitro T-cell proliferation: alternatives to the [(3)H]thymidine incorporation assay

T-cell proliferation is an important in vitro parameter of in vivo immune function and has been used as a prognostic marker of human immunodeficiency virus type 1 (HIV-1) disease progression. The proliferative capacity of T cells in response to various stimuli is commonly determined by a radioactive assay based on incorporation of [(3)H]thymidine ([(3)H]TdR) into newly generated DNA. In order to assess techniques for application in laboratories where radioactive facilities are not present, two alternative methods were tested and compared to the [(3)H]TdR assay as a "gold standard." As an alternative, T-cell proliferation was measured by flow cytometric assessment of CD38 expression on T cells and by an enzyme-linked immunosorbent assay (ELISA) based on bromo-2'-deoxyuridine (BrdU) incorporation. Peripheral blood mononuclear cells (PBMCs), either in whole blood or Ficoll-Isopaque separated, from a total of 26 HIV-1-positive and 18 HIV-1-negative Dutch individuals were stimulated with CD3 monoclonal antibody (MAb) alone, a combination of CD3 and CD28 MAbs, or phytohemagglutinin. BrdU incorporation after 3 days of stimulation with a combination of CD3 and CD28 MAbs correlated excellently with the [(3)H]TdR incorporation in both study groups (HIV-1 positives, r = 0.96; HIV-1 negatives, r = 0.83). A significant correlation of absolute numbers of T cells expressing CD38 with [(3)H]TdR incorporation, both in HIV-1-positive (r = 0.96) and HIV-1-negative (r = 0.84) individuals, was also observed under these conditions. The results of this study indicate that determination of both the number of CD38-positive T cells and BrdU incorporation can be used as alternative techniques to measure the in vitro T-cell proliferative capacity. The measurement of CD38 expression on T cells provides the additional possibility to further characterize the proliferating T-cell subsets for expression of other surface markers.

Distinct categories of immunologic changes in frail elderly

Immune changes and their relationships in a frail elderly population (N=116, age 70-103, median 86 years) were defined in comparison to a healthy younger group. Previous immune studies in the elderly have generally focused on one or few parameters without correlation analyses. Furthermore, the study populations have been active elderly in relatively small numbers. A total of 33 immune parameters representing many aspects of the immune system were quantified. Most changes in the frail elderly were parallel to those reported in active elderly. A classification tree analysis revealed that increased plasma activation markers (neopterin and sTNF-R) and increased CD28 expression on CD8 T cells and proliferative response separated the aged and control populations. Statistical procedures utilizing principal components analyses, partial correlations and exploratory factor analyses all indicated that immunologic parameters in frail elderly are grouped in three major clusters of immunologic results. These involved (a) increased plasma levels of neopterin and sTNF receptor indicating elevated IFNgamma and TNF cytokine activity; (b) increased proportion of mature (CD45RO) versus naïve (CD45RA) T cells; and (c) a diverse group of related changes including impaired proliferative response, reduced T cells, CD28 and CD25 expression, B cell percentage and lower CD4:CD8 ratios and increased HLA-DR expression. These findings emphasize that several different groups of immune parameters but not 33 independent immune changes, occurred in the aged population.

Regeneration and tolerance factor: a correlate of human immunodeficiency virus-associated T-cell activation

Human immunodeficiency virus (HIV) infection causes extensive phenotypic alterations in lymphocytes. Cellular markers that are normally absent or expressed at low levels on quiescent cells are upregulated throughout the disease course. The transmembrane form of regeneration and tolerance factor (RTF) is expressed at negligible levels on resting T cells but is quickly upregulated following in vitro stimulation and activation. Recently, we reported that expression of RTF was significantly higher in cells from HIV-seropositive (HIV(+)) individuals than in cells from HIV-seronegative (HIV(-)) individuals. Because T cells from HIV(+) individuals express markers reflecting chronic activation, we hypothesized that these in vivo-activated cells would coexpress RTF. Flow cytometry was used to assess RTF expression on activated (CD38(+) and HLA-DR(+)) CD4(+) and CD8(+) T cells. HIV(+) individuals had higher percentages of RTF(+) CD38(+) (P < 0.0001) or RTF(+) HLA-DR(+) (P = 0.0001) CD4(+) T cells than HIV(-) individuals. In HIV(+) individuals, increased percentages of CD4(+) T cells that were RTF(+), RTF(+) CD38(+), and RTF(+) HLA-DR(+) correlated inversely with the absolute number and percentage of CD4(+) T cells and correlated positively with plasma beta(2)-microglobulin concentrations. HIV(+) individuals had higher percentages of CD8(+) T cells that were RTF(+) CD38(+) (P = 0.0001) or RTF(+) HLA-DR(+) (P = 0.0010). In HIV(+) individuals, increased percentages of CD8(+) T cells that were RTF(+) HLA-DR(+) correlated inversely with the percentage of CD4(+) T cells, and high percentages of CD8(+) T cells that were RTF(+) CD38(+) correlated positively with plasma beta(2)-microglobulin levels. These findings strongly suggest that increased RTF expression is a correlate of HIV-associated immune system activation.

Levels of cytokines and immune activation markers in plasma in human immunodeficiency virus infection: quality control procedures

Procedures for quality control (QC) in a laboratory that concentrates on cytokine and soluble marker measurements in biological fluids are outlined. Intra-assay, interassay, and interlaboratory experiences are presented. Plasma and serum beta2-microglobulin (beta2M) and neopterin test data are presented in greatest detail, along with substantial tumor necrosis factor alpha (TNF-alpha), gamma interferon, soluble interleukin-2 receptor-alpha (sIL-2Ralpha), sTNF-RII, IL-4, and IL-6 data. Recommended QC procedures for cytokine and soluble-marker testing include replicate testing of two or more reference samples provided by the kit manufacturer, replicate testing of in-house frozen reference QC samples that represent normal and abnormal analyte contents, retesting 15 to 20% of randomly selected samples, and comparing normal reference ranges each year. Also, eight cytokines and soluble markers were evaluated in human immunodeficiency virus (HIV)-seronegative and HIV-seropositive individuals stratified on the basis of CD4 T-cell numbers. Levels of some but not all cytokines in serum increased in HIV infection. There was a tendency for cytokines to increase with more advanced disease, defined by reduced CD4 T-cell numbers. Cytokine changes did not relate closely to CD4 level, indicating that separate information was provided by the measurements of TNF-alpha, sTNF-RII, sIL-2Ralpha, beta2M, and neopterin. Serum IL-4 and TNF-alpha levels were not increased. The quality of laboratory data can impact on clinical relevance. Interlaboratory comparisons revealed substantial differences at some sites and documented the need for external proficiency-testing quality assurance programs.