Changes in blood CD8+ lymphocyte activation status and plasma HIV RNA levels during antiretroviral therapy

Correlation between CD4/CD8 ratio and neurocognitive performance during early HIV infection

INTRODUCTION

CD4/CD8 ratio is a marker of immune activation in HIV infection and has been associated with neurocognitive performance during chronic infection, but little is known about the early phases. The aim of this study was to examine the relationship between blood CD4/CD8 ratio and central nervous system endpoints in primary HIV infection (PHI) before and after antiretroviral treatment (ART).

METHODS

This was a retrospective analysis of the Primary Infection Stage CNS Events Study (PISCES) cohort. We longitudinally assessed blood and cerebrospinal fluid (CSF) markers of inflammation, immune activation and neuronal injury, and neuropsychological testing performance (NPZ4, an average of three motor and one processing speed tests, and a summarized total score, NPZ11, including also executive function, learning and memory) in ART-naïve participants enrolled during PHI. Spearman correlation and linear mixed models assessed the relationships between the trajectory of CD4/CD8 ratio over time and neurocognitive performance, blood and CSF markers of immune activation and neuronal injury.

RESULTS

In all, 109 PHI participants were enrolled. The mean CD4/CD8 ratio decreased with longer time from infection to starting treatment (p < 0.001). Every unit increase in NPZ4 score was independently associated with a 0.15 increase in CD4/CD8 ratio (95% CI: 0.002-0.29; p = 0.047), whereas no correlation was found between CD4/CD8 ratio and NPZ11. Among the cognitive domains, only a change in processing speed was correlated with CD4/CD8 ratio over time (p = 0.03). The trajectory of the CD4/CD8 ratio was negatively correlated with change in CSF neurofilament light chain (p = 0.04).

CONCLUSIONS

The trajectory of CD4/CD8 ratio was independently associated with motor/psychomotor speed performance, suggesting that immune activation is involved in brain injury during the early stages of the infection.

Peripheral neuropathy in primary HIV infection associates with systemic and central nervous system immune activation

BACKGROUND

Peripheral neuropathy (PN) is a frequent complication of chronic HIV infection. We prospectively studied individuals with primary HIV infection (<1 year after transmission) to assess the presence of and laboratory associations with PN in this early stage.

METHODS

Standardized examination and analysis of blood and cerebrospinal fluid (CSF) was performed in participants with laboratory-confirmed primary HIV infection. PN was defined as ≥1 of the following unilateral or bilateral signs: decreased distal limb position, vibration, or temperature sense or hyporeflexia; symptomatic PN (SPN) was defined as the presence of these signs with symptoms. Analysis used nonparametric statistics.

RESULTS

Overall, 20 (35%) of 58 antiretroviral-naive male subjects without diabetes evaluated at a median of 107 days post HIV transmission met criteria for PN. Thirteen (65%) of 20 PN subjects met criteria for SPN; 6 (30%) of 20 had bilateral findings. PN subjects and no PN subjects (NPN) did not differ in median age, days post HIV transmission, blood CD4 or CD8 counts, CSF or plasma HIV RNA levels, CSF white blood cell counts, or CSF to blood albumin ratio. PN and SPN subjects had elevated CSF neopterin (P = 0.003 and P = 0.0005), CSF monocyte chemoattractant protein-1 (P = 0.006 and P = 0.01), and blood neopterin (P = 0.006 and P = 0.009) compared with NPN subjects. PN subjects had a higher percentage of activated phenotype CSF CD8 T lymphocytes than NPN subjects (P = 0.009).

CONCLUSIONS

Signs of PN were detected by detailed neurologic examination in 35% of men enrolled in a neurological study at a median of 3.5 months after HIV transmission. PN during this early period may be mediated by systemic and nervous system immune responses to HIV.

Predictors of CD4:CD8 ratio normalization and its effect on health outcomes in the era of combination antiretroviral therapy

Background

HIV leads to CD4:CD8 ratio inversion as immune dysregulation progresses. We examined the predictors of CD4:CD8 normalization after combination antiretroviral therapy (cART) and determined whether normalization is associated with reduced progression to AIDS-defining illnesses (ADI) and death.

Methods

A Canadian cohort of HIV-positive adults with CD4:CD8<1.2 prior to starting cART from 2000–2010 were analyzed. Predictors of (1) reaching a CD4:CD8 ≥1.2 on two separate follow-up visits >30 days apart, and (2) ADI and death from all causes were assessed using adjusted proportional hazards models.

Results

4206 patients were studied for a median of 2.77 years and 306 (7.2%) normalized their CD4:CD8 ratio. Factors associated with achieving a normal CD4:CD8 ratio were: baseline CD4+ T-cells >350 cells/mm³, baseline CD8+ T-cells <500 cells/mm³, time-updated HIV RNA suppression, and not reporting sex with other men as a risk factor. There were 213 ADIs and 214 deaths in 13476 person-years of follow-up. Achieving a normal CD4:CD8 ratio was not associated with time to ADI/death.

Conclusions

In our study, few individuals normalized their CD4:CD8 ratios within the first few years of initiating modern cART. This large study showed no additional short-term predictive value of the CD4:CD8 ratio for clinical outcomes after accounting for other risk factors including age and HIV RNA.

Central memory CD4 cells are an early indicator of immune reconstitution in HIV/AIDS patients with anti-retroviral treatment

The number of central memory cells among the CD4+ T cells and the of activation of CD8+ T cells is believed to be a better indicator of immune restoration in patients on antiretroviral therapy (ART) than the absolute numbers of CD4(+) and CD8+ T cells alone. In the current study, we investigated the changes in the CD4(+) T cell subsets and their association with immune reconstitution and immune activation at early stages of ART. A prospective study was performed in 21 asymptomatic treatment-naive HIV-infected patients with CD4(+) T cells less than 350 cells/μl. Blood samples were evaluated at base line, and at 2, 4, 8 and 12 weeks' post antiretroviral therapy (ART). A biphasic increase of CD4(+) T cells, central memory CD4 cells (CD4 CM) and CD4 naïve cells were observed after ART, with a rapid increase before week 4. Change in CD4 CM at week 4 positively correlated with the change in CD4(+) T cells at weeks 12 post ART, and negatively correlated with the change in CD8(+)CD38(+) T cells at weeks 12 post ART. We conclude that CD4 CM cells are a major contributor to early immune reconstitution in treatment-naive HIV-infected patients with delayed ART, and might be an early indicator for immune reconstitution.

Characteristics of CD8+ T cell subsets in Chinese patients with chronic HIV infection during initial ART

BACKGROUND

CD8+ T cells may play an important role in protecting against HIV. However, the changes of CD8+ T cell subsets during early period of ART have not been fully studied.

METHODS

Twenty-one asymptomatic treatment-naive HIV-infected patients with CD4 T+ cells less than 350 cells/μl were enrolled in the study. Naïve, central memory(CM), effective memory(EM) and terminally differentiated effector (EMRA) CD8+ cell subsets and their activation and proliferation subsets were evaluated in blood samples collected at base line, and week 2, 4, 8 and 12 of ART.

RESULTS

The total CD8+ T cells declined and the Naïve and CM subsets had a tendency of increase. Activation levels of all CD8+ T cell subsets except EMRA subset decreased after ART. However, proliferation levels of total CD8+ T cells, EMRA, EM and CM subsets increased at the first 4 weeks of ART, then decreased. Proliferation level of the naïve cells decreased after ART.

CONCLUSION

The changes of CD8+ T cell subsets during initial ART are complex. Our results display a complete phenotypical picture of CD8+ cell subsets during initial ART and provide insights for understanding of immune status during ART.

High T-cell immune activation and immune exhaustion among individuals with suboptimal CD4 recovery after 4 years of antiretroviral therapy in an African cohort

BACKGROUND

Antiretroviral therapy (ART) partially corrects immune dysfunction associated with HIV infection. The levels of T-cell immune activation and exhaustion after long-term, suppressive ART and their correlation with CD4 T-cell count reconstitution among ART-treated patients in African cohorts have not been extensively evaluated.

METHODS

T-cell activation (CD38+HLA-DR+) and immune exhaustion (PD-1+) were measured in a prospective cohort of patients initiated on ART; 128 patient samples were evaluated and subcategorized by CD4 reconstitution after long-term suppressive treatment: Suboptimal [median CD4 count increase 129 (-43-199) cells/μl], N = 34 ], optimal [282 (200-415) cells/μl, N = 64] and super-optimal [528 (416-878) cells/μl, N = 30].

RESULTS

Both CD4+ and CD8 T-cell activation was significantly higher among suboptimal CD4 T-cell responders compared to super-optimal responders. In a multivariate model, CD4+CD38+HLADR+ T-cells were associated with suboptimal CD4 reconstitution [AOR, 5.7 (95% CI, 1.4-23, P = 0.014)]. T-cell exhaustion (CD4+PD1+ and CD8+PD1+) was higher among suboptimal relative to optimal (P < 0.001) and super-optimal responders (P < 0.001). T-cell exhaustion was significantly associated with suboptimal responders [AOR, 1.5 (95%CI, 1.1-2.1), P = 0.022].

CONCLUSION

T-cell activation and exhaustion persist among HIV-infected patients despite long-term, sustained HIV-RNA viral suppression. These immune abnormalities were associated with suboptimal CD4 reconstitution and their regulation may modify immune recovery among suboptimal responders to ART.

Dynamic correlation between CTL response and viral load in primary human immunodeficiency virus-1 infected Koreans

Background

HIV-1 specific cytotoxic T lymphocytes (CTLs) have an important role as antiviral effector cells for controlling HIV-1 infection.

Methods

To investigate CTL response during the early stage of HIV infection, we measured immunity-related factors including CD4⁺ T cell counts, CD8⁺ T cell counts, HIV-1 RNA viral loads and IFN-γ secretion according to CTL response in 78 selected primary HIV-1-infected Koreans.

Results

The CTL response was strongly induced by HIV-1 specific Gag and Nef peptides (p = 0.016) compared with induction by Tat or Env peptides. These results suggest that the major antiviral factors inducing strong HIV-specific CTL responses are associated with the Gag and Nef viral regions in primary HIV-1 infected Koreans. The relationship between viral load and CTL response showed varying correlations with time following HIV infection. CTL response was inversely correlated with viral loads at preseroconversion stage I (r = -0.224 to -0.33) and changed to a positive correlation at the preseroconversion stage II (r = 0.132 to 0.854). Finally, it changed to an inverse correlation again after seroconversion until a viral set point was established on serological profiling (r = -0.195 to -0.407).

Conclusions

These findings demonstrate a dynamic correlation between viral load and subsequent CTL responses during early HIV infection.

Immune activation and antibody responses in non-progressing elite controller individuals infected with HIV-1

An extremely rare subset of patients infected with HIV-1 designated as "non-progressing elite controllers" appears to be able to maintain stable CD4(+) T-cell counts and a median plasma viremia below the detection limit of current ultrasensitive assays (<50-80 copies/ml of plasma) for >10 years in the absence of antiretroviral therapy. Lymphocyte subsets (CD4(+), CD8(+)), immune activation markers (HLA-DR(+), CD38(+), Beta-2-microglobulin), and HIV-specific antibody responses were longitudinally examined in four non-progressing elite controllers over more than 5 years. Two control groups of seronegative healthy individuals and untreated patients infected with HIV-1 presenting detectable viremia were also included. None of the non-progressing elite controllers displayed the high T-cell activation levels generally seen in the seropositive individuals, keeping them within the normal range. Three non-progressing elite controllers showed no significant immune system abnormalities when compared to seronegative individuals, displaying a low proportion of HIV-1-specific binding antibodies and low avidity index, similar to those observed for individuals infected recently with HIV-1. One non-progressing elite controller exhibited CD8(+) T-cell counts and beta2-M levels above normal ranges and developed a low but "mature" (high-avidity) HIV-1-specific antibody response. Thus, the non-progressing elite controllers are able to maintain normal T-cell activation levels, which may contribute to prevent, or greatly reduce, the damage of the immune system typically induced by the HIV-1 over time. They are, however, immunologically heterogeneous and very low levels of antigen exposure seem to occur in these patients, sufficient for sustaining a low, but detectable, HIV-1-specific immunity.

Longitudinal microarray analysis of cell surface antigens on peripheral blood mononuclear cells from HIV+ individuals on highly active antiretroviral therapy

Background

The efficacy of highly active antiretroviral therapy (HAART) determined by simultaneous monitoring over 100 cell-surface antigens overtime has not been attempted. We used an antibody microarray to analyze changes in the expression of 135 different cell-surface antigens overtime on PBMC from HIV+ patients on HAART. Two groups were chosen, one (n = 6) achieved sustainable response by maintaining below detectable plasma viremia and the other (n = 6) responded intermittently. Blood samples were collected over an average of 3 years and 5–8 time points were selected for microarray assay and statistical analysis.

Results

Significant trends over time were observed for the expression of 7 cell surface antigens (CD2, CD3epsilon, CD5, CD95, CD36, CD27 and CD28) for combined patient groups. Between groups, expression levels of 10 cell surface antigens (CD11a, CD29, CD38, CD45RO, CD52, CD56, CD57, CD62E, CD64 and CD33) were found to be differential. Expression levels of CD9, CD11a, CD27, CD28 and CD52, CD44, CD49d, CD49e, CD11c strongly correlated with CD4+ and CD8+ T cell counts, respectively.

Conclusion

Our findings not only detected markers that may have potential prognostic/diagnostic values in evaluating HAART efficacy, but also showed how density of cell surface antigens could be efficiently exploited in an array-like manner in relation to HAART and HIV-infection. The antigens identified in this study should be further investigated by other methods such as flow cytometry for confirmation as biological analysis of these antigens may help further clarify their role during HAART and HIV infection.

Antibody microarray analysis of cell surface antigens on CD4+ and CD8+ T cells from HIV+ individuals correlates with disease stages

Background

Expression levels of cell surface antigens such as CD38 and HLA-DR are related to HIV disease stages. To date, the immunophenotyping of cell surface antigens relies on flow cytometry, allowing estimation of 3–6 markers at a time. The recently described DotScan antibody microarray technology enables the simultaneous analysis of a large number of cell surface antigens. This new technology provides new opportunities to identify novel differential markers expressed or co-expressed on CD4+ and CD8+ T cells, which could aid in defining the stage of evolution of HIV infection and the immune status of the patient.

Results

Using this new technology, we compared cell surface antigen expression on purified CD4+ and CD8+ T cells between 3 HIV disease groups (long-term non-progressors controlling viremia naturally; HIV+ patients on highly active antiretroviral therapy (HAART) with HIV plasma viral loads <50 copies/ml; and HIV+ patients with viremia during HAART) and uninfected controls. Pairwise comparisons identified 17 statistically differential cell surface antigens including 5 novel ones (CD212b1, CD218a, CD183, CD3 epsilon and CD9), not previously reported. Notably, changes in activation marker expression were more pronounced in CD8+ T cells, whereas changes in the expression of cell membrane receptors for cytokines and chemokines were more pronounced in CD4+ T cells.

Conclusion

Our study not only confirmed cell surface antigens previously reported to be related to HIV disease stages, but also identified 5 novel ones. Of these five, three markers point to major changes in responsiveness to certain cytokines, which are involved in Th1 responses. For the first time our study shows how density of cell surface antigens could be efficiently exploited in an array manner in relation to HIV disease stages. This new platform of identifying disease markers can be further extended to study other diseases.

Evaluation of HIV-1 p24 Antigenemia and Level of CD8+CD38+ T cells as Surrogate Markers of HIV-1 RNA Viral Load in HIV-1-Infected Patients in Dakar, Senegal

Alternative, affordable, and simple assays to monitor antiretroviral therapy (ART) in resource-poor settings are needed. We have evaluated and compared a heat-denatured (HD) HIV p24 amplified enzyme-linked immunosorbent assay from Perkin-Elmer and CD38CD8 T-cell levels, determined by flow cytometry, for their capacity to predict viral load (VL) in HIV-1-infected patients from Senegal. Median fluorescence intensity (MFI) of CD38 expression on memory (CD45RO) CD8 T cells correlated better with RNA VL than HD p24 antigenemia (R = 0.576, P < 0.0001 vs R = 0.548, P < 0.0001). MFI of CD38 expression on memory CD8 T cells could predict detectable RNA VL (VL = 2.6 log10) with a sensitivity of 87% and a specificity of 74%. A comparable sensitivity (89%) could be reached for HD p24 assay, but only to predict RNA VL of more than 5 logs, which might lead to unacceptable delays in clinical decision making. The clinical use of the HD p24 assay to monitor ART in Senegal would require more comparative data about the kinetics of p24 antigen and HIV RNA in peripheral blood as well as further evaluation regarding its sensitivity toward subtype A and CRF02. MFI of CD38 expression on memory CD8 T cells appeared to be a better alternative to monitor ART in HIV-infected patients from Senegal.

Differential Upregulation of CD38 on Different T-Cell Subsets May Influence the Ability to Reconstitute CD4+ T Cells Under Successful Highly Active Antiretroviral Therapy

BACKGROUND

Immune activation is an independent surrogate marker of CD4 T-cell depletion in HIV-infected patients. Highly active antiretroviral therapy (HAART) reduces disease progression as a direct consequence of suppressing HIV replication. Immune function does not normalize completely in most subjects on HAART, however, perhaps reflecting residual HIV replication. So far, it is unclear to what extent immune activation may influence the evolution of CD4 T-cell counts in patients on HAART.

PATIENTS AND METHODS

The expression of CD38 on naive and memory subsets of CD4+ and CD8+ T cells was measured quantitatively by flow cytometry in 62 drug-naive HIV-positive and 30 HIV-uninfected controls. In addition, the evolution of this marker as well as that of some virologic parameters (plasma viremia and proviral load) and CD4 counts were assessed in 25 HIV-infected individuals who initiated HAART and were followed for 12 months.

RESULTS

The mean level of CD38 on memory CD4+ and CD8+ T cells as well as in naive CD8+ cells was significantly higher in drug-naive HIV-positive subjects than in HIV-negative controls. Moreover, it was highly correlated with viral load titers. In patients on successful HAART, immune activation declined in all T-cell subsets, particularly among memory CD8+ cells. It remained elevated with respect to HIV-negative controls, however, even after 12 months of HAART. There was a significant correlation between the CD8+ T-cell activation decay and the increase of CD4+ T cells on HAART. Patients with the highest decline in CD8 activation were those showing the highest CD4 T-cell gains after 12 months of therapy.

CONCLUSIONS

The level of CD38 expression on different T-cell subsets is differentially upregulated in drug-naive HIV-infected patients. After successful HAART, immune activation decreases in all T-cell subsets, although it still remains elevated in most cases after 12 months of HAART. The extent of immune deactivation under successful HAART correlates with the ability to reconstitute CD4 counts.

Flow Cytometry Evaluation of the T-Cell ReceptorVβ Repertoire Among HIV-1 Infected Individuals Before and After Antiretroviral Therapy

HIV-1 infection leads to serious impairment of the immune system and perturbations in the T cell receptor Vbeta repertoire are also described. Immune reconstitution can be potentially achieved in response to HAART. In the present study 10 patients were investigated for the Vbeta pattern expression before and after six months of HAART. TCR were analyzed for T CD4+ and CD8+ subsets, separately, by flow cytometry, using a monoclonal antibody set of 24 different Vbeta chains. Compared to eight Brazilian healthy controls, no differences in Vbeta pattern of expression was observed for patients before or on antiretroviral therapy. Some chains such as Vbeta 3, 14, 16, 20 and 21.3 were over utilized by both T subsets, independently of HIV infection and/or antiretroviral treatment, differing from the ones described for individuals of other nationalities. However, when each patient was taken individually, particular alterations were detected for the Vbeta gene usage, compared to controls, for all individuals. After treatment, significant Vbeta usage changes were observed for seven patients. One or more chains on both T subsets were engaged in this process, defining a preferential oligoclonal profile for TCR repertoire distribution, after HAART. Although no pattern of specific Vbeta changes was detected in the circulating T cells, we cannot exclude that differential immune responses to HIV or other important antigens are being focused by these cells.

CD38 expression on CD8 T lymphocytes as a marker of residual virus replication in chronically HIV-infected patients receiving antiretroviral therapy

The level of CD8+ CD38+ T lymphocytes in blood correlates with disease progression in HIV-infected individuals, independently of the CD4 count. Effective antiretroviral therapy reduces this lymphocyte subset in parallel with plasma viremia, although CD38 expression on CD8+ cells does not normalize completely in most subjects, and might reflect residual HIV replication. The expression of CD38 on CD8+ cells (as number of CD38 molecules per CD8+ cell) was measured quantitatively by flow cytometry in 200 individuals, of whom 170 were HIV positive and 30 were HIV-uninfected controls. Forty-six HIV-infected subjects were on antiretroviral therapy and had undetectable viral load. The remaining 124 HIV-positive persons were not on therapy and had detectable plasma viremia. The mean level of CD38 on CD8+ cells was higher in HIV-positive, untreated patients than in subjects on antiviral therapy and controls (5023, 2029, and 1978 molecules per CD8+ cell, respectively, p < 0.01). In HIV-positive, untreated subjects, the higher CD38 expression mainly occurred on CD45RO+ CD8+ cells. The level of CD38 strongly correlated with plasma HIV-RNA (r = 0.63, p < 0.001). The levels of CD38 on CD8+ cells declined steadily in HIV-positive subjects after beginning antiretroviral therapy. A few individuals presented viral blips whereas being on antiviral treatment, levels of CD38 on CD8+ cells increased transiently in parallel with episodes of viral replication. Levels of CD38 on CD8+ cells are increased in chronic HIV infection, and strongly correlate with plasma viremia. The slow decline of CD38 expression on CD8+ cells over time in subjects with undetectable plasma viremia while being on antiretroviral therapy suggests that CD38 expression on CD8+ cells could be used as a marker of residual virus replication.

CD38 expression in CD8+ T cells predicts virological failure in HIV type 1-infected children receiving antiretroviral therapy

An observational study of children vertically infected with human immunodeficiency virus type 1 (HIV-1) was performed to determine the role of CD38 expression in CD8(+) T cells as prognostic marker of virological failure in children receiving HAART. We studied 42 children who were receiving antiretroviral therapy and who had an undetectable virus load (uVL), and we found a negative correlation between CD38 expression in CD8(+) T cells and the duration of uVL. We selected 17 HIV-1-infected children with CD38 values close to the baseline level (i.e., the first uVL achieved), and we distributed the children into 2 groups on the basis of median CD38 value in CD8(+) T cells. Children with CD38 values in CD8(+) T cells that were higher than the median had a higher incidence and relative risk of virological failure than did those with values lower than the median. In conclusion, we demonstrate for the first time that CD8(+)CD38(+) T cell count is a good prognostic marker of therapeutic failure in HIV-1-infected children.

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.

Recovery of T-cell subsets after antiretroviral therapy in HIV-infected children

BACKGROUND

Variation of percentageCD4+ T cells may accurately reflects the kinetics of a comprehensive immune recovery independently of the antiretroviral (ART) regimen. To test this we have investigated the relationship among peripheral blood T-cell subsets with the variation of percentageCD4+ T cells during follow up in 49 HIV-infected children.

METHODS

Children were divided into two groups according to the sign of slope percentageCD4+ T cell during follow up: Ps-group (positive slope) and Ns-group (negative percentageCD4 slope) indicative of immunological recovery or not, respectively. CD4+ and CD8+ T-cell subset percentages were examined by three-colour flow cytometry.

RESULTS

We found higher memory CD4+ and CD8+ T-cell percentages in the Ns-group than in the Ps-group, and inversely, higher naive CD4+ and CD8+ T cells in the Ps-group than in the Ns-group. CD4+ and CD8+ subsets in the Ps-group expressed higher levels of CD38+ and lower levels of HLA-DR+ compared with the Ns-group. We found a very strong positive correlation among the slope of percentageCD4+, CD4+ CD38+, whereas a negative correlation among the slope of percentageCD4+, the CD8+ CD28+ CD57+ and CD8+ CD57+ T-cell subsets.

CONCLUSION

Recovery of the CD4+ T-cell percentage induced by ART reflects a reduction in the chronic immune activation and a measurable reconstitution of the immune system and depends on naive CD4+ T cells.

HIV, 'an evolving species'. Roles of cellular activation and co-infections

Each small variation of the genome of a species can be preserved if it is useful for the survival of the species in a given environment. Within this framework, the finality of the biological cycle of HIV consists in a search for harmony (biological coherence) with man, which is to say a stable condition. Cellular activation appears to be the strategy developed by HIV in order to achieve this coherence. The price of this strategy is the AIDS. The first contact between HIV and immune system appears to determine the subsequent clinical outcome and the future of HIV. Lymphocytic activation varies during the course of the vital cycle of HIV. For each individual, this lymphocytic activation depends on both the HLA repertoire acquired during thymic ontogenesis and the antigenic experience before and after HIV infection. Thus intercurrent infections alter the immune condition of the organism and influence the outcome of HIV. We described a synthetic analysis of the effects of HIV on the surface protein expression and the cellular activation pathways which should provide insights in the evolutionary relationship between HIV and man and should permit to do a more physiological therapeutic approach.

Changes in levels of immune activation and reconstitution markers among HIV-1-infected Africans receiving antiretroviral therapy

OBJECTIVE

To describe changes in immune activation and reconstitution markers among HIV-1-infected patients receiving antiretroviral therapy (ART) in Abidjan, Côte d'Ivoire.

METHODS

Between November 1998 and February 2001, we analyzed changes in immune activation and reconstitution markers among 52 patients. Good virologic responders (n = 26) were defined as those who had suppressed and maintained plasma viral load (VL) below the detection limit of the assay for at least 12 months. Poor virologic responders (n = 26) were defined as those with a detectable VL at 6 and 12 months after beginning ART.

RESULTS

Of the 26 good virologic responders, 20 (77%) were on highly active antiretroviral therapy (HAART) compared with one (4%) of the poor responders. Among the 26 good responders, baseline median levels of CD38+CD8+ T cells were elevated, but had decreased significantly at 6 months (P < 0.001) and at 12 months of therapy (P < 0.001). Median levels of HLA-DR+CD8+ T cells also decreased from baseline at 6 months (P < 0.001) and at 12 months of therapy (P < 0.001). Levels of CD62L+CD4+ T cells increased steadily during the 6 and 12 months of therapy and reached levels observed among HIV-negative blood donors (P = 0.07). Among the 26 poor responders, median levels of CD38+CD8+ T cells decreased significantly at 12 months of therapy (P = 0.006), but were higher than levels in blood donors (P = 0.005). Levels of HLA-DR+CD8+ T cells decreased significantly at 12 months of therapy (P < 0.001). Levels of CD62L+CD4+ decreased over time.

CONCLUSION

Our results suggest that HAART can be successfully used in African populations with elevated baseline immune activation markers.

HIV-1 therapeutic vaccines

In this review, we address recent advances in the understanding of the pathogenesis of human immunodeficiency type 1 virus infection, which have provided the rationale for present trials of therapeutic vaccines. We shall relate this work to lessons of the past few years both in the use of highly active antiretroviral therapy to attempt eradication of the HIV virus, and in the study of treatment interruptions.

Parallel decline of CD8+/CD38++ T cells and viraemia in response to quadruple highly active antiretroviral therapy in primary HIV infection

OBJECTIVES

To monitor changes in the numbers of CD8 lymphocytes expressing the activated CD38++ phenotype in peripheral blood samples from patients with primary HIV infection (PHI) treated with highly active antiretroviral therapy (HAART).

METHODS

Zidovudine, lamivudine, abacavir and amprenavir were initiated during PHI as part of the Quest study. Absolute numbers of CD8+/CD38++ T cells were determined using three-colour flow cytometry, and plasma viral load (VL) was measured using the Roche Amplicor method.

RESULTS

The median, pre-therapy CD8+/CD38++ T cell count was 461/mm(3)(interquartile range 216, 974) in 131 patients compared with normal control values of less than 20 cells/mm(3). Levels fell markedly in parallel with VL within the first 2 weeks of HAART initiation, to a median of 47 cells/mm(3) at 28 weeks (median 436 cell decline; P < 0.001). At that time, 80% of patients had a VL less than 50 copies/ml, and 16.3% of all patients had less than 20 CD8+/CD38++ T cells/mm(3). A continued decrease in CD8+/CD38++ T cell count occurred in 67.2% of patients whose VL was maintained below 50 copies/ml (median change from first to last value -18 cells/mm(3); P < 0.001).

CONCLUSION

After the initiation of HAART in PHI, CD8+/CD38++ lymphocytes declined rapidly in parallel with VL, and allowed for a normalization of CD8+/CD38++ T cell numbers in a subset of patients at week 28. Cell numbers continued to decline in patients who maintained VL below 50 copies/ml, indicating that the CD8+/CD38++ T cell count may represent a marker of residual viral replication when VL falls below detectable levels after HAART intervention.

Evidence of immune reconstitution in antiretroviral drug-experienced patients with advanced HIV disease

Highly active antiretroviral therapy (HAART) of HIV disease is associated with effective virologic control, immune reconstitution, and clinical improvements. This study addresses the potential for improvements in lymphocyte phenotype and virologic responses of HIV-infected persons with extensive experience with dual nucleoside reverse transcriptase (NRTI) treatment and advanced HIV disease after a change to a potent antiretroviral therapy (NRTI + protease inhibitor). The majority of participants achieved virologic success. There was a median rise in CD4+ lymphocytes of 99 cells/mm(3) by 48 weeks, because of an increase in memory CD4+ cells at 4 and 16 weeks, followed by a later increase in naive CD4+ cells between weeks 16 and 48. The proportion of activated, DR+ CD38+ CD8+ lymphocytes decreased during the 48 weeks of follow-up. The immunologic findings (increased memory and naive T cells and reduced activation levels) were significantly improved in participants with persistent suppression of viral replication over the 48 weeks of the study. Baseline HIV RNA copy number was lower (median, 14,784 copies/ml) in persons who responded virologically than in those not suppressing viral replication (median, 49,454 copies/ml). CD4+ cell counts above the median (125/mm(3)) at time 0 for the participants, was the only baseline immunologic marker significantly associated with viral suppression at week 48. Participants older than 40 years of age demonstrated less immunologic recovery. The results of the study show that patients with extensive experience with NRTIs respond both virologically and immunologically during the first 48 weeks of therapy with a potent antiretroviral regimen.

Decrease in immune activation in HIV-infected patients treated with highly active antiretroviral therapy correlates with the function of hematopoietic progenitor cells and the number of naive CD4+ cells

This study was conducted to determine the impact of immune activation, cytokine production and apoptosis on the naive CD4+ cell count and the function of hematopoietic progenitor cells during the initial phase of highly active antiretroviral therapy (HAART). Blood samples from 11 HIV-infected patients were collected prior to HAART and after 4 and 12 weeks of therapy. Flow cytometry was used to determine the naive CD4+ count and activated T cells. The cloning efficiency of progenitor cells was determined using a colony-forming cells assay. Finally, apoptosis and cytokine production were determined. During the study period, the naive CD4+ count and the cloning efficiency increased significantly. Immune activation was found in HIV-infected patients and decreased during HAART. The level of immune activation correlated negatively with both the naive CD4+ count and the function of progenitor cells. A negative correlation was found between apoptosis and the naive CD4+ count. Alterations in cytokine production during HAART or correlation between cytokine production and the naive CD4+ count or the cloning efficiency of progenitor cells were not detected. In conclusion, immune activation in HIV-infected patients treated with HAART is inversely correlated with the function of progenitor cells and the naive CD4+ count.

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.

Antiretroviral treatment simplification with nevirapine in protease inhibitor-experienced patients with hiv-associated lipodystrophy: 1-year prospective follow-up of a multicenter, randomized, controlled study

BACKGROUND

Simpler and less toxic antiretroviral strategies are needed to maximize treatment compliance without sacrificing potency, at least for drug-experienced HIV-infected patients currently on regimens containing protease inhibitors (PIs). Small nonrandomized studies have suggested a beneficial role of PI-sparing regimens on lipodystrophy.

OBJECTIVES

To assess the virologic, immunologic, and clinical benefit of switching the PI to nevirapine in patients with HIV-associated lipodystrophy and sustained viral suppression before entry in the study.

DESIGN

Open-labeled, prospective, randomized, multicenter study.

SETTING

Seven reference inpatient centers for HIV/AIDS in Spain.

PATIENTS

One hundred six HIV-infected adults with clinically evident lipodystrophy who sustained HIV-RNA suppression for at least 6 months with PI-containing antiretroviral combinations.

INTERVENTION

Replacement of the PI with nevirapine during 48 weeks (Group A) versus continuing the prior PI (Group B).

MEASUREMENTS

Several virologic and immunologic analyses, standard and specific biochemical tests, and anthropometric and dual X-ray absorptiometry measurements.

RESULTS

At week 48, an HIV-1 RNA level <400 copies/ml was maintained in 79% and 77% of patients in Groups A and B, respectively, whereas 74% and 72% of patients had viral load levels <50 copies/ml. Absolute CD4+ counts significantly increased in both groups compared with baseline values, and a significant decrease in CD38+CD8+ cells was observed in Group A (p <.01) but not in group B. Overall, no significant changes in anthropometric or body shape measurements were found after 48 weeks. Fasting total cholesterol and triglyceride levels decreased in Group A (but not in Group B) compared with baseline values (p <.05), although no significant differences were seen between groups at the end of the study. Subjects in Group A reported a better quality of life (QOL) index than controls (p <.001), with the main reason reported being the greater simplicity of the new drug regimen.

CONCLUSIONS

Protease inhibitor-sparing regimens, including nevirapine, seem to be an effective alternative for PI-experienced patients. Nevirapine-based triple therapies allow maintained control of HIV-1 RNA levels and improve the immunologic response at 48 weeks of follow-up in patients with prior sustained virologic suppression. The switch to nevirapine significantly improved the lipidic profile in Group A, although there were no differences between groups at the end of the study. Additionally, no significant changes were seen in terms of lipodystrophy-related body shape changes 1 year after the PI substitution. Finally, nevirapine-containing regimens have a simpler dosing schedule, and this facilitates high adherence and improves QOL.

Long-term evaluation of T-cell subset changes after effective combination antiretroviral therapy during asymptomatic HIV-infection

Demonstration of long-lived HIV-reservoirs resistant to the effects of combination antiretroviral therapy raises concern over the ability of treatment to maintain long-term beneficial alterations in T-cell subset composition. To address this issue, we have examined the effect of antiretroviral therapy on T-cell subset change during early HIV-infection in a 2-year prospective open-label trial composed of treatment-naive asymptomatic HIV-infected patients with CD4+ T-cell counts > or =400 cells/microl. Therapy consisted of double (zidovudine and lamivudine) or triple (zidovudine, lamivudine, and ritonavir) combination antiretroviral therapy. Retrospective analysis based on magnitude of viral suppression was used to characterize responder and nonresponder groups. Among responders, long-term antiretroviral therapy maintained a significant increase in numbers of total CD4+, naive CD4+/CD45RA+, and memory CD4+/CD45RO+ T cells. A concomitant significant decrease in numbers of memory CD8+/CD45RO+ and both activated CD8+/HLA-DR+ and CD8+/CD38+ T cells was also maintained. In contrast, long-term antiretroviral therapy among nonresponders led only to a significant increase in the numbers of CD4+ T cells and a significant reduction in numbers of activated CD8+/HLA-DR+ T cells. The long-term ability of antiretroviral therapy during early asymptomatic HIV-infection to maintain reversal of disease-induced T-cell activation and maturation abnormalities continues to support the concept that immunologic advantage is gained by commencing early aggressive antiretroviral therapy. Nevertheless, continued management of T-cell subset recovery is significantly more effective in the presence of completely suppressed viral replication.

T cell expansions in lymph nodes and peripheral blood in HIV-1-infected individuals: effect of antiretroviral therapy

OBJECTIVE

To evaluate dynamics in CD8 T cell expansions during highly active antiretroviral therapy (HAART).

DESIGN

Various T cell subsets were isolated from blood and lymph nodes and analysed for T cell receptor (TCR) diversity.

METHODS

TCR complementarity determining region 3 (CDR3) spectratyping and single-strand conformation polymorphism (SSCP) analyses were performed in combination with sequencing to assess clonality of the subsets.

RESULTS

Strongly skewed CDR3 patterns in total CD8 cells and the CD8 subsets CD45RO+CD27+ and CD45RO-CD27+ showed substantial dynamics in dominant CDR3 sizes, resulting in relative improvement of CDR3 size diversity in the first months of therapy. During sustained treatment, TCR diversity changed only moderately. SSCP profiles confirmed oligoclonality of TCR CDR3 perturbations. Various dominant CDR3 sizes for CD4 and CD8 T cells present in lymph nodes, but not in peripheral blood mononuclear cells, before the start of therapy emerged in peripheral blood early during therapy.

CONCLUSIONS

HAART induces substantial changes in CD8 TCR diversity, eventually resulting in improvement of the repertoire. Clonal expansions observed in lymph nodes before therapy were observed in peripheral blood after therapy, suggesting that recirculation of CD4 and CD8 T cells from lymph nodes contributes to the early T cell repopulation. Decreased immune activation and possibly naive T cell regeneration subsequently decreased clonal expansions and perturbations in the CD8 TCR repertoire.

Immunophenotyping

Immunophenotyping of leukocytes for nonmalignant conditions uses the power of multiparameter flow cytometry to count specific lymphocyte populations and evaluate the presence or absence of particular cell surface markers. Its main clinical indications, and the focus of this chapter, are enumeration of CD4 T-cell counts and activation markers on T cells in human immunodeficiency virus (HIV) infection, immunophenotypic characterization of primary immunodeficiency disorders and immune-mediated diseases, and the study of immune reconstitution following stem cell transplantation (SCT). Immunophenotyping has advanced our understanding of many immunologic disorders, which in turn have stimulated new developments in the field of flow cytometry, such as quantitative flow cytometry and single-platform technology. Semin Hematol 38:100-110. This is a US government work. There are no restrictions on its use.

Immune interventions

A better understanding of the immune response to HIV and the deleterious effect that HIV infection may have on the immune system in general, allows us to consider how best to restore protective immune responses to HIV and other opportunistic pathogens in the immunocompromised host. In this chapter, we summarise areas of current innovation and provide an update of the current state of knowledge concerning interventions which could result in the immunocompromised state being reversed. We describe the kinds of immune responses, which are thought to be useful in combating both the human immunodeficiency virus and other pathogenic organisms, and methods which are being considered to stimulate such responses. Lessons which may be learned from other disease states, which lead to immunodeficiency and methods for measuring successful outcome of treatment will be described.

Therapeutic targeting of human immunodeficiency virus type-1 latency: current clinical realities and future scientific possibilities

Factors affecting HIV-1 latency present formidable obstacles for therapeutic intervention. As these obstacles have become a clinical reality, even with the use of potent anti-retroviral regimens, the need for novel therapeutic strategies specifically targeting HIV-1 latency is evident. However, therapeutic targeting of HIV-1 latency requires an understanding of the mechanisms regulating viral quiescence and activation. These mechanisms have been partially delineated using chronically infected cell models and, clearly, HIV-1 activation from latency involves several key viral and cellular components. Among these distinctive therapeutic targets, cellular factors involved in HIV-1 transcription especially warrant further consideration for rational drug design. Exploring the scientific possibilities of new therapies targeting HIV-1 latency may hold new promise of eventual HIV-1 eradication.

Frequency of cytokine-producing T cells in HIV-infected patients treated with stavudine, didanosine, and ritonavir

To assess prospectively the influence of the control of viral replication on the frequency of cytokine-producing T cells, and to correlate these changes with immune activation, we conducted a 15-month follow-up study of IFN-gamma- and IL-2-producing CD4+ and CD8+ T cells at a single-cell level in 12 previously untreated patients receiving highly active antiretroviral therapy (HAART). At baseline we observed a strikingly high proportion of IFN-gamma-producing CD8+ T cells. The treatment-induced decrease in the proportion of IFN-gamma-producing CD8+ T cells ran parallel to the decrease in HLA-DR+ and CD38+CD8+ T cell subsets and was associated with the reduction in HIV RNA level. IL-2-producing cells were mainly CD4+. As a consequence of CD4+ T cell loss, the number of IL-2-producing CD4+ T cells was lower in patients than in control subjects (52 vs. 171 cells/microl), but the proportion of these cells was unchanged (22.4 vs. 19.3). During therapy the proportion of CD4+ IL-2-producing cells was initially stable and then fell markedly at month 5, followed by a gradual return to previous values. The reduction in viral load was associated with the fall in the proportion of CD4+ activated subsets. Intracellular cytokine assays are a new approach to the assessment of T cell function in HIV infection. Our results suggest that the functional capacity of CD4+ T cells is probably less severely altered than previously thought on the basis of conventional assays. CD8+ T cells exhibit an increased capacity to produce IFN-gamma that is associated with an increase in activation marker expression. These alterations decrease partially and in parallel under treatment.

The dominant source of CD4+ and CD8+ T-cell activation in HIV infection is antigenic stimulation

To distinguish between antigenic stimulation and CD4+ T-cell homeostasis as the cause of T-cell hyperactivation in HIV infection, we studied T-cell activation in 47 patients before and during highly active antiretroviral therapy (HAART). We show that expression of human leukocyte antigen (HLA)-DR, CD38, and Ki67 on T cells decreased during HAART but remained elevated over normal values until week 48 of therapy. We confirm previous reports that T-cell activation correlates positively with plasma HIV RNA levels (suggesting antigenic stimulation), and negatively with CD4 count (suggesting CD4+ T-cell homeostasis). However, these correlations may be spurious, because misleading, due to the well-established negative correlation between CD4 count and plasma HIV RNA levels. To resolve this conflict, we computed partial correlation coefficients. Correcting for CD4 counts, we show that plasma HIV RNA levels contributed to T-cell hyperactivation. Correcting for plasma HIV RNA levels, we show that CD4+ T-cell depletion contributed to T-cell activation. Correcting for both, activation of CD4+ and CD8+ T cells remained positively correlated. Because this suggests that CD4+ and CD8+ T-cell activation is caused by a common additional factor, we conclude that antigenic stimulation by HIV or other (opportunistic) infections is the most parsimonious explanation for T-cell activation in HIV infection. Persistence of HIV antigens may explain why T-cell activation fails to revert to levels found in healthy individuals after 48 weeks of therapy.

Human immunodeficiency virus type 1 induces apoptosis in CD4(+) but not in CD8(+) T cells in ex vivo-infected human lymphoid tissue

Progression of human immunodeficiency virus (HIV) disease is associated with massive death of CD4(+) T cells along with death and/or dysfunction of CD8(+) T cells. In vivo, both HIV infection per se and host factors may contribute to the death and/or dysfunction of CD4(+) and CD8(+) T cells. Progression of HIV disease is often characterized by a switch from R5 to X4 HIV type 1 (HIV-1) variants. In human lymphoid tissues ex vivo, it was shown that HIV infection is sufficient for CD4(+) T-cell depletion. Here we address the question of whether infection of human lymphoid tissue ex vivo with prototypic R5 or X4 HIV variants also depletes or impairs CD8(+) T cells. We report that whereas productive infection of lymphoid tissue ex vivo with R5 and X4 HIV-1 isolates induced apoptosis in CD4(+) T cells, neither viral isolate induced apoptosis in CD8(+) T cells. Moreover, in both infected and control tissues we found similar numbers of CD8(+) T cells and similar production of cytokines by these cells in response to phorbol myristate acetate or anti-CD3-anti-CD28 stimulation. Thus, whereas HIV-1 infection per se in human lymphoid tissue is sufficient to trigger apoptosis in CD4(+) T cells, the death of CD8(+) T cells apparently requires additional factors.

Immunological evaluation of human immunodeficiency virus infected individuals by flow cytometry

Human immunodeficiency virus (HIV) infection heavily compromises the immune system. The decrease of the T cell CD4+ subset along the evolution to acquired immunodeficiency syndrome has been considered as a hallmark of HIV infection. In this paper we review some aspects of the immunopathology of HIV infection and discuss the importance of the flow cytometry for the evaluation of the T lymphocyte subsets in the follow-up of HIV infected children and adults, and for the monitoring of the immune reconstitution upon antiretroviral therapy.

Treatment-resistant expansion of CD8+CD28-cells in pediatric HIV infection

There is a disease stage-dependent loss of CD28 expression on T cells in HIV-infected children. In this study, T cell recovery, in particular CD28 expression on T cells, was analyzed after initiation of highly active antiretroviral therapy in a group of eight mostly treatment-naive HIV-infected children. Plasma HIV-RNA levels were recorded, and numbers of CD4, CD8, CD4+CD28+, and CD8+CD28+ cells were determined by two-color flow cytometry. Values after 12 mo of therapy were compared with age-matched, seronegative control subjects. CD4 recovery to subnormal values was observed in all children. CD8+CD28+ cells recovered and were within the normal range after 12 mo of therapy (patients, 703 +/- 250 cells/microL; controls, 789 +/- 269 cells/microL), whereas CD8+CD28- cells (546 +/- 269 cells/microL) remained significantly expanded compared with age-matched controls (140 +/- 35 cells/microL). Expansions of CD8+CD28- cells persisted even in cases with long-term suppression of viral replication. Highly active antiretroviral therapy in HIV-infected children induces substantial but incomplete T cell recovery.

Functional subsets within clonally expanded CD8(+) memory T cells in elderly humans

With advancing age, healthy humans frequently demonstrate large clonal expansions of CD8(+) T cells in the peripheral blood, which persist for long periods of time and appear to be maintained as a population of memory cells. We studied nine large T cell clones in five elderly individuals. We noted that in most cases the expanded clones were dominated by cells that did not express CD28, a pivotal molecule in T cell activation, and these clones proliferated poorly in culture. However, nearly all of the clonal expansions had CD28(+) fractions and some of these cells appeared to lose CD28 gene expression with stimulation in culture. CD28(+) cells demonstrated greater proliferation in both bulk and limiting dilution cultures compared to CD28(-) cells bearing the same TCR, whereas CD28(-) cells showed increased perforin expression. Together, these data suggest that loss of CD28 expression marks functional differentiation to cytotoxic memory cells within these clonal expansions and likely within CD8(+) memory populations in general.

Activation of CD8 T cells normalizes and correlates with the level of infectious provirus in tonsils during highly active antiretroviral therapy in early HIV-1 infection

OBJECTIVES

To study the effects of antiretroviral therapy on T cell activation in blood and tonsils from HIV-1 infected individuals in relation to CD4 cell count, plasma viremia, and infectious HIV-1 provirus.

DESIGN

A 48-week study of viral load and T cell subsets in blood and tonsils from 12 HIV-1-positive individuals with a mean CD4 cell number of 400 x 10(6) cells/l treated with a combination of zidovudine, lamivudine, and indinavir.

METHODS

Tonsil biopsies and blood samples were collected at regular intervals. Lymphocytes were phenotyped and quantified by three-color flow cytometry; infectious provirus was quantified by a limiting dilution assay. HIV-1-negative individuals were included as controls.

RESULTS

The fraction of tonsillar CD8 T cells expressing CD69, CD38, or HLA-DR in the patients with suppressed virus replication declined to levels comparable with that in controls by 48 weeks and showed a strong positive correlation with tonsillar infectious provirus and plasma viremia. The level of CD4 T cell activation was within normal range in tonsils throughout the study. The fraction of HLA-DR+ cells within CD4 and CD8 T cells in blood declined rapidly in parallel with plasma viremia but remained slightly higher compared with that in uninfected individuals.

CONCLUSION

Antiretroviral therapy normalizes tonsillar CD8 T cell activation in HIV-1-positive individuals in parallel with suppression of viral replication, indicating reduced CD8 cell turnover. Normal tonsillar CD4 T cell activation suggests limited CD4 cell turnover in early HIV infection. Activated CD8 T cells in lymphoid tissue is superior to that in blood as an immunological marker for the virological response to antiretroviral therapy.

Effect of long-term infection with nef-defective attenuated HIV type 1 on CD4+ and CD8+ T lymphocytes: increased CD45RO+CD4+ T lymphocytes and limited activation of CD8+ T lymphocytes

Members of the Sydney Blood Bank Cohort (SBBC) have been infected with an attenuated strain of HIV-1 with a natural nef/LTR mutation and have maintained relatively stable CD4+ T lymphocyte counts for 14-18 years. Flow cytometric analysis was used to examine the phenotype of CD4+ and CD8+ T lymphocytes in these subjects, including the immunologically important naive (CD45RA+CD62L+), primed (CD45RO+), and activated (CD38+HLA-DR+ and CD28-) subsets. The median values were compared between the SBBC and control groups, comprising age-, sex-, and transfusion-matched HIV-1-uninfected subjects; transfusion-acquired HIV-1-positive LTNPs; and sexually acquired HIV-1-positive LTNPs. Members of the SBBC not only had normal levels of naive CD4+ and CD8+ T lymphocytes, but had primed CD45RO+ CD4+ T lymphocytes at or above normal levels. Furthermore, these primed cells expressed markers suggesting recent exposure to specific antigen. SBBC members exhibited variable activation of CD8+ T lymphocytes. In particular, SBBC members with undetectable plasma HIV-1 RNA had normal levels of activated CD8+ T lymphocytes. Therefore, the result of long-term infection with natural nef/LTR mutant HIV-1 in these subjects suggests a decreased cytopathic effect of attenuated HIV-1 on susceptible activated CD4+ T lymphocyte subsets in vivo, and minimal activation of CD8+ T lymphocytes.

Prospective study of CD8+ lymphocyte activation in relation to viral load in HIV-infected patients with > or = 400 CD4+ lymphocytes per microliter

To investigate the temporal relationship between CD8+ lymphocyte phenotypic alterations, the CD4+ T cell decline, and plasma HIV RNA levels during the natural history of HIV infection, 33 treatment-naive HIV-infected patients with > or =400 CD4+ cells/microl were studied prospectively for 3 years. During the study period, 20 patients remained untreated, and only 6 received more than 6 months of therapy. A significant relationship was found between changes in plasma HIV RNA and changes in the proportion of CD38+CD8+ cells. Conversely, the number of CD4+ T cells lost per year was strongly related to the increase in the proportion of CD28-CD8+ T cells. A strong relationship between mean yearly changes in CD4+ T cell numbers and changes in HIV RNA was also observed. CD4+ T cell changes were associated with changes in both viral load and CD8+ T cell activation. These results provide support for the use of both virologic and immunologic parameters for prognosis and management during HIV infection.

Immune reconstitution in HIV-1 infected subjects treated with potent antiretroviral therapy

The introduction of potent antiretroviral drug regimens contributed to a decline in HIV-1 associated morbidity and mortality. Clinical observations of spontaneous remission of previously untreatable opportunistic infections in subjects on highly active antiretroviral therapy (HAART) reflect the substantial degree of immune reconstitution which can be achieved by those therapies. A biphasic increase of CD4+ T lymphocytes has been reported including naive (CD45RA+) and memory (CD45RO+) cell subsets. Proliferative lymphocyte responses to recall antigens and mitogens are enhanced over time, while T lymphocyte activation is largely reduced and T cell receptor (TCR) repertoires are partly restored. Proliferative lymphocyte responses specific to HIV-1 antigens, in contrast, remain weak. A complete normalisation of HIV-1 associated immunological alterations has not been reported so far, but the observation period of subjects on potent antiretroviral therapies is still relatively short.

Phenotypic analysis of CD8+ T lymphocytes in a cohort of HIV type 1-infected patients treated with saquinavir, ritonavir, and two nucleoside analogs for 1 year, and association with plasma HIV type 1 RNA

The phenotype of circulating CD8+ T lymphocytes and its association with plasma HIV-1 RNA were analyzed in 34 HIV-1-infected subjects, who were treated with saquinavir, ritonavir, and two nucleoside analogs (HAART) for 1 year. Four-color flow cytometry was applied to measure the expression of cell surface antigens CD38, HLA-DR, CD45RA, CD28, and CD62L on CD8+ T lymphocytes. The results were compared with data on 35 HIV-1-seronegative subjects, 18 untreated asymptomatic HIV-1-seropositive individuals, and 24 HIV-1-infected subjects receiving reverse transcriptase inhibitors (RTIs). Subjects receiving HAART showed a significantly elevated number and percentage of CD38- and HLA-DR-positive and CD28-negative CD8+ T lymphocytes as well as a lower percentage of naive (CD45RA+62L+) CD8+ T lymphocytes compared with HIV-1-uninfected controls. Even subjects with undetectable plasma HIV-1 RNA showed a persistent elevation of activated CD8+ T lymphocytes. However, fewer activated CD8+ T lymphocytes were observed in subjects receiving HAART than in untreated individuals and subjects administered RTIs. In individuals receiving RTIs, CD8+ cell activation was not significantly reduced compared with untreated subjects. Of all evaluated activation markers, the percentage of CD8+ T lymphocytes expressing CD38 and the combination of CD38 and HLA-DR showed the best correlation with plasma HIV-1 RNA. The persistence of CD8+ T lymphocyte activation in subjects receiving HAART strongly suggests ongoing viral activity, even in subjects with undetectable plasma HIV-1 RNA. A complete normalization of immunologic changes of CD8+ T lymphocytes would therefore require a more potent drug regimen or a longer duration of therapy.

CD8 T-Cell Infiltration in Extravascular Tissues of Patients With Human Immunodeficiency Virus Infection. Interleukin-15 Upmodulates Costimulatory Pathways Involved in the Antigen-Presenting Cells–T-Cell Interaction

Interleukin (IL)-15 regulates the proliferative activity of the CD8+ T-cell pool in human immunodeficiency virus (HIV)-infected patients, thereby contributing to the maintenance of the CD8+ T-cell–mediated immune response against HIV in extravascular tissues, including the lung. However, the effects of IL-15 on antigen-presenting cells (APC) during HIV infection are still unclear. In this study, we evaluated whether IL-15 regulates the macrophage stimulatory pathways governing inflammatory events that take place in the lung of patients with HIV infection. As a first step we evaluated the in vitro effects of IL-15 on lung macrophages retrieved from the respiratory tract of eight normal subjects. Although macrophages from uninfected individuals expressed the IL-15 binding proteins (IL-15R and the common γc) at resting conditions, they did not express IL-15 messenger RNA (mRNA). However, a 24-hour stimulation with IL-15 induced the expression of interferon-γ (IFN-γ) and IL-15 itself, suggesting a role for this cytokine in the activation of the pulmonary macrophage pool during inflammation. As a confirmation of the role of IL-15 in this setting, at resting conditions, alveolar macrophages of patients with HIV infection and T-cell alveolitis expressed IL-15, IFN-γ, and IL-15 binding proteins; showed an upmodulation of costimulatory molecules, B7 and CD72, which are involved in the APC of macrophages; and behaved as effective accessory cells because they elicited a strong proliferation of T cells. The accessory effect was inhibited by pretreatment with anti-CD72, anti-B7 (CD80 and CD86), and anti–IL-15 monoclonal antibodies (MoAb). We then investigated the relationship between IL-15 and the expression of costimulatory molecules by macrophages. A 24-hour stimulation of IL-15R+/γc+ macrophages with IL-15 upregulated the expression of CD80 and CD86. The evidence that IL-15 upregulates the expression of coligands that favor the contact between T cells and APC, per se, triggers T-cell activation and proliferation and acts as a chemoattractant for T cells, suggests that IL-15 plays a key role in Tc1-mediated defense mechanisms taking place in extravascular tissues of patients with HIV disease.

CD8 T-Cell Infiltration in Extravascular Tissues of Patients With Human Immunodeficiency Virus Infection. Interleukin-15 Upmodulates Costimulatory Pathways Involved in the Antigen-Presenting Cells–T-Cell Interaction

Interleukin (IL)-15 regulates the proliferative activity of the CD8+ T-cell pool in human immunodeficiency virus (HIV)-infected patients, thereby contributing to the maintenance of the CD8+ T-cell–mediated immune response against HIV in extravascular tissues, including the lung. However, the effects of IL-15 on antigen-presenting cells (APC) during HIV infection are still unclear. In this study, we evaluated whether IL-15 regulates the macrophage stimulatory pathways governing inflammatory events that take place in the lung of patients with HIV infection. As a first step we evaluated the in vitro effects of IL-15 on lung macrophages retrieved from the respiratory tract of eight normal subjects. Although macrophages from uninfected individuals expressed the IL-15 binding proteins (IL-15R and the common γc) at resting conditions, they did not express IL-15 messenger RNA (mRNA). However, a 24-hour stimulation with IL-15 induced the expression of interferon-γ (IFN-γ) and IL-15 itself, suggesting a role for this cytokine in the activation of the pulmonary macrophage pool during inflammation. As a confirmation of the role of IL-15 in this setting, at resting conditions, alveolar macrophages of patients with HIV infection and T-cell alveolitis expressed IL-15, IFN-γ, and IL-15 binding proteins; showed an upmodulation of costimulatory molecules, B7 and CD72, which are involved in the APC of macrophages; and behaved as effective accessory cells because they elicited a strong proliferation of T cells. The accessory effect was inhibited by pretreatment with anti-CD72, anti-B7 (CD80 and CD86), and anti–IL-15 monoclonal antibodies (MoAb). We then investigated the relationship between IL-15 and the expression of costimulatory molecules by macrophages. A 24-hour stimulation of IL-15R+/γc+ macrophages with IL-15 upregulated the expression of CD80 and CD86. The evidence that IL-15 upregulates the expression of coligands that favor the contact between T cells and APC, per se, triggers T-cell activation and proliferation and acts as a chemoattractant for T cells, suggests that IL-15 plays a key role in Tc1-mediated defense mechanisms taking place in extravascular tissues of patients with HIV disease.

Altered ex vivo balance between CD28+ and CD28- cells within HIV-specific CD8+ T cells of HIV-seropositive patients

The CD8+CD28- cell population in the blood of HIV-infected individuals is considerably expanded. Yet the cause of this expansion is not clear. The recent demonstration of identical TCR-rearranged genes in CD8+CD28+ and CD8+CD28- expanded T cells of HIV-seropositive patients supports the hypothesis that these two subpopulations are phenotypic variants of the same lineage. To further elucidate the precise relationship between them, we measured the fraction of CD28+ and CD28- T cell subsets in IFN-gamma-producing CD8+ T cells by intracellular staining and cytofluorometry as a functional test for ex vivo recognition of epitopes derived from HIV-1, Epstein-Barr virus (EBV) and influenza virus. HIV-specific CD8+ T cells were predominantly CD28 in all the eight HIV-seropositive subjects tested. In contrast, the anti-EBV and anti-influenza CD8+ T cells were mainly CD28+ in these patients as well as in HIV-seronegative individuals. This supports the notion that the CD8 CD28 hyperlymphocytosis observed in HIV infection is due mainly to chronic activation and differentiation of HIV-specific memory CD8+CD28+ T cells into terminally differentiated CD8+CD28-lymphocytes, because of intense HIV-1 replication and without any important bystander activation. This clarification of the mechanisms underlying the CD8+CD28- expansion in HIV-induced pathogenesis may have important therapeutic implications.