Phenotypic characterization of CD8+ T cell populations in HIV disease and in anti-HIV immunity

A monoclonal antibody against lymphocyte function-associated antigen-1 decreases HIV-1 replication by inducing the secretion of an antiviral soluble factor

Background

Lymphocyte Function-Associated Antigen-1 (LFA-1) likely plays a role in the pathogenesis of against HIV-1 and is known to facilitate cell-to-cell transmission of the virus. A monoclonal antibody specific for LFA-1 (Cytolin®) was evaluated as a potential therapeutic in pilot studies performed in the mid-1990s. These uncontrolled human studies suggested that administration of this anti-LFA-1 antibody to HIV-1 infected individuals could provide a modest benefit by decreasing circulating HIV-1 RNA and increasing CD4+ T cell counts. At the time, it was proposed that when bound to cytolytic T cells, the antibody inhibited lysis of activated CD4+ T cells. Given the renewed interest in monoclonal antibody therapy for HIV-1 infected individuals, we investigated possible mechanisms of action of this antibody in vitro.

Methods

To assess whether this anti-LFA-1 antibody binds to HIV-1, a virus capture assay was performed. Binding of the antibody to cells was assessed using flow cytometry. Inhibition of HIV-1 replication was determined in culture by measuring the amount of p24 produced by ELISA. After co-culture of the antibody with peripheral blood mononuclear cells, supernatants were assayed for cytokines and chemokines using various immunoassays.

Results

Our experiments demonstrate that anti-LFA-1 antibody binds to CCR5 and CXCR4 utilizing strains of HIV-1. It also binds to CD8+ T cells and dendritic cells. When bound to virus prior to infection, there is no decrease in HIV-1 replication, suggesting it does not directly inhibit viral replication via virus binding. When bound to cells, it does not inhibit lysis of CD4+ T cells, as was originally hypothesized. Binding to cells does appear to induce the production of a soluble factor that inhibits HIV-1 replication. We determined that this soluble factor was not any of the cytokines or chemokines with known anti-HIV-1 activity. Further, the antibody does not appear to induce any common immune modulating cytokines or chemokines.

Conclusions

These results suggest that one possible mechanism of action of this anti-LFA-1 antibody is to inhibit HIV-1 replication via the production of a soluble antiviral factor that is induced upon binding to cells.

Lung CD4 Lymphocytes Predict Survival in Asymptomatic HIV Infection

BACKGROUND

Plasma viral load and blood CD4 counts are accepted indicators of severity of illness in patients with HIV-1. Lung CD4 counts have not been evaluated in asymptomatic HIV-1 patients as indicators of disease severity.

OBJECTIVE

To determine if lung lymphocyte counts in asymptomatic subjects with HIV compare with plasma viral loads and blood CD4 counts in predicting survival.

DESIGN

Retrospective, cross-sectional analysis.

SETTING

Midwestern urban community, December 1996 to August 1998.

PARTICIPANTS

HIV-seropositive subjects (n = 95) without AIDS-related pulmonary complications.

MEASUREMENTS

Plasma viral load, blood hemoglobin and blood lymphocyte subtypes, lung lymphocyte subtypes from BAL, body mass index, and mortality.

RESULTS

Eight of the 95 subjects (8.4%) had died at the 4-year follow-up. Lung CD4 counts were significantly related to mortality by univariable analysis (2.5 x 10(3)/mL vs 0.9 x 10(3)/mL, median values for survivors vs nonsurvivors, respectively, p = 0.010). Modeling using exact methods further showed lung CD4 counts to be a significant predictor of survival after individually adjusting for potential confounders, including plasma viral load and blood CD4 count.

CONCLUSIONS

Lung CD4 counts in patients with HIV-1 infection may provide an independent predictor of survival.

Expression of granzyme B mRNA is altered in human immunodeficiency virus infected patients

CD8-positive cytotoxic T lymphocytes and natural killer cells are the major cytotoxic components of the antiviral immune response. The major pathway used by these cells in response to viral-infected cells involves granzymes, cytotoxic granule serine proteases involved in the pathway leading to target cell DNA fragmentation and apoptosis. The levels of granzyme B mRNA in peripheral blood cells of human immunodeficiency virus (HIV) type-1 infected patients in comparison to noninfected individuals were assessed by quantitative competitive reverse transcriptase polymerase chain reaction. Expression of granzyme B mRNA is altered in HIV-1 infected patients. Significantly fewer HIV patients had detectable granzyme B mRNA levels than controls. The one HIV-infected patient with detectable granzyme B mRNA displayed a much higher level of this mRNA than all healthy controls. Cell-mediated cytotoxicity during HIV-1 infection may be impaired due to a deficient quantity of active cytotoxic granules or to their abnormal regulation.

Naïve to memory T-cell differentiation during homeostasis-driven proliferation

During homeostasis-driven T-cell proliferation, naïve T cells stably acquire the cell surface markers and functional properties of antigen-induced memory T cells. Thus, in T-cell-deficient individuals, homeostasis-driven T-cell proliferation appears to restore only the memory T-cell compartment, whereas the reconstitution of the naïve T-cell compartment depends on de novo T-cell development in the thymus.

In vitro HIV-specific CTL activity from HIV-seropositive individuals is augmented by interleukin-12 (IL-12)

IL-12 production is reduced in HIV infection, and recombinant human IL-12 (rhIL-12) augments in vitro HIV-specific proliferative responses in PBMC from HIV-seropositive individuals. To determine whether rhIL12 could also augment HIV-specific CTL responses we studied 41 HIV-seropositive individuals. Recombinant hIL-12 increased the detectable in vitro HIV-specific CD8 CTL activity of PBMC taken from HIV-seropositive individuals with CD4 counts >500 cells/microl and from some individuals with lower CD4 counts. IL-12 increased cell recovery in cultures of PBMC from HIV-seropositive individuals with CD4 counts >500 cells/microl and also increased the precursor CTL frequency. However, the increase in HIV-specific CTL activity was not due to IL-2 or IFN-gamma production or an increase in the number of cells with surface markers characteristic of CTL effector cells. This study demonstrates that rhIL-12 augments in vitro HIV-specific CTL activity and provides evidence to justify further investigation within clinical trials of this cytokine in HIV infection.

BAL and serum IgG levels in healthy asymptomatic HIV-infected patients

OBJECTIVES

To determine if the increased susceptibility to bacterial infection in asymptomatic HIV-infected patients is associated with decreased total IgG or IgG2 levels in lung epithelial lining fluid.

BACKGROUND

A decrease in lung IgG levels or subtypes has been proposed as contributing to the increased risk of bacterial lung infections in HIV-infected patients. Previous studies measuring lung lavage IgG concentrations have been inconsistent.

METHODS

Twenty-three HIV patients and 25 control subjects underwent BAL. Both patient groups were of similar age, and had similar pulmonary function studies and body mass index. Smokers were equally represented in both groups, and the majority of subjects in both groups were male. Total IgG and IgG2 levels in lavage fluid were assayed in both cohorts and compared using a two-tailed Student's t test.

RESULTS

The lung lining fluid IgG level in HIV-infected patients was 0.19 +/- 0.13 microg/microg of protein (mean +/- SD) vs 0.11 +/- 0.09 microg/microg of protein in control subjects (p < 0.05). The IgG(2) level in HIV patients was 0.034 +/- 0.038 microg/microg of protein and 0.014 +/- 0.01 microg/microg of protein in control subjects (p = 0.054). Lavage IgG levels reflected serum IgG values (correlation coefficient, 0.56; p < 0.001) but did not correlate with lung immunoglobulin-producing cells.

CONCLUSIONS

The increased susceptibility to bacterial pneumonia in asymptomatic HIV-infected individuals is neither explained by depressed total IgG levels nor a deficiency in IgG(2) levels in the lungs. The strong correlation between serum and lavage IgG levels suggests that lavage IgG derives from serum.

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.

C1.7 Antigen Expression on CD8+ T Cells Is Activation Dependent: Increased Proportion of C1.7+CD8+ T Cells in HIV-1-Infected Patients with Progressing Disease

The C1.7 Ag is a surface marker previously shown to be expressed on all NK cells and on a subset of CD8+ T cells. We report in this study that C1.7 Ag expression on peripheral blood-derived CD8+ T cells overlaps with activation markers S6F1high and CD29high and is reciprocally expressed with CD62L. C1.7 Ag expression can be induced in vitro on CD8+ T cells by anti-CD3 cross-linking, suggesting that C1.7 Ag is activation dependent. In contrast to NK cells, C1.7 Ag does not signal on CD8+ T cells, nor does it induce redirected lysis upon ligation. The proportion of C1.7 Ag+CD8+ T cells is increased in HIV-infected patients compared with healthy donors. In 69 HIV-infected patients, we observed a significant inverse correlation between the percentage of C1.7 Ag-expressing CD8+ T cells and the absolute CD4+ T cell count. Two-year clinical follow-up of patients with initial CD4+ T cell count of &gt;400 cells/mm3 and a normal proportion of C1.7 Ag+CD8+ T cells revealed that these patients were clinically stable with minimal HIV-associated symptoms. In contrast, 10 of 12 patients with CD4+ T cell counts of &gt;400 cells/mm3 and an elevated proportion of C1.7 Ag+CD8+ T cells were symptomatic. ANOVA analysis of patients indicates that C1.7 Ag is a better predictor of disease progression than CD4 count. Overall, our findings indicate that C1.7 Ag is the first described marker for activated/memory CD8+ T cells and a useful parameter for evaluating the level of CD8+ T cell activation in vivo.

Expansion of CD57 and CD62L-CD45RA+ CD8 T lymphocytes correlates with reduced viral plasma RNA after primary HIV infection

OBJECTIVE

CD8 T cells, expressing cell surface molecules distinct from those on resting and naive T cells, are increased in HIV infection. The association of increased CD38 and human leukocyte antigen DR (HLA-DR) CD8 T cells with poor prognosis has suggested that activated CD8 T cells may aggravate HIV infection. We examined whether other immunological parameters might influence the viral setpoint.

DESIGN

Peripheral T cells from nine untreated patients, obtained after primary HIV infection when plasma HIV had stabilized, were examined for proteins expressed in activated versus resting, memory versus naive, and cytolytic versus non-cytolytic T cells.

METHODS

The proportion of CD8 T cells that stain for CD38 and HLA-DR, CD28 and CD57 was compared with plasma viraemia and CD4 cell count. These parameters were also compared with the proportion of CD4 and CD8 T cells that express CD62L and CD45RA, present on naive cells and down-modulated in memory cells. Internal staining for the cytotoxic protein granzyme A was also examined.

RESULTS

An increase in CD38 and CD38 HLA-DR CD8 T cells correlated with increased plasma viral RNA (P < 0.00002, P < 0.03, respectively). An increase in CD8 T cells expressing granzyme A was associated with lower CD4 cell counts (P < 0.04). However, the expansion of CD57 and CD62L CD45RA+ CD8 T cells was associated with a lower viral setpoint (P < 0.01, P < 0.02, respectively).

CONCLUSION

Phenotypically defined activated CD8 T cells may have different functions in HIV infection. Activated CD8 T cells that are CD57 or CD62L(-)CD45RA+ may be beneficial, because their expansion in untreated patients correlates with a reduced viral setpoint after primary infection.

CD8+ lymphocytes in pregnancy and HIV infection: characterization of CD8+ subpopulations and CD8+ noncytotoxic antiviral activity

The distribution and function of lymphocytes vary in different clinical states. The object of this study was to characterize the CD8+ lymphocyte subpopulations and CD8+ anti-HIV suppressor activity in HIV-infected and uninfected pregnant and nonpregnant women. The total percentage of CD8+ lymphocytes was not altered by pregnancy but the percentage of activated CD8+ T cells increased during pregnancy and decreased postpartum. HIV infection in pregnant women resulted in both an increased percentage of CD8+ lymphocytes and a marked increase in activated and memory CD8+ lymphocyte subsets, which did not change in the postpartum period. Most HIV-infected women had CD8+-mediated noncytotoxic antiviral activity. However, the activity was not correlated with alterations in CD8+ lymphocyte subsets. This study provides baseline information on changes in CD8 immunologic parameters during pregnancy and HIV infection for further studies that employ antiretroviral therapeutic regimens capable of impacting the immune response.

Cigarette smoking in HIV infection induces a suppressive inflammatory environment in the lung

Lung lymphocyte numbers are frequently increased in human immunodeficiency virus (HIV)-infected individuals in the absence of lung infection, and may play a critical role in viral surveillance and protection against new infections. In this context, cigarette smoking by HIV-infected individuals has been associated with a relative increase in the peripheral blood CD4(+) T-lymphocyte count as compared with that of nonsmokers. Because lung defense is local, the aim of the present study was to determine whether cigarette smoking had a significant impact on local lung defenses in HIV-infected individuals. The numbers and subtypes of bronchoalveolar lymphocytes and the ability of lung lavage cells to produce proinflammatory cytokines were compared in 58 smokers and 34 nonsmokers. In contrast to a trend toward an increase in peripheral blood CD4(+) cell counts among nonsmokers, smokers had significant depressions in both the percentage and absolute numbers of CD4(+) and CD8(+) cells in their bronchoalveolar lavage fluid (BALF). A decrease in CD4(+)/CD8(+) cell ratios was also seen with smoking. In addition, production of both interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) was suppressed with cigarette smoking. These observations show that cigarette smoking is associated with suppression in localized lung defenses, and suggest that smoking cessation may have a positive impact on lung defenses in HIV-infected smokers.

In vitro enhancement of T-cell receptor-targeted lysis after IL-2 treatment of PBL from HIV-seropositive individuals

Individuals with advanced HIV infection have a greater proportion of T-cells that are activated when compared to uninfected individuals. These activated cells are not able to lyse specific targets. The reason for this dysfunction is not well known. In this study we demonstrate that there are CD8+ T-cells from HIV-seropositive individuals that can be targeted to lyse targets with OKT3 (anti-CD3 antibody) but are unable to lyse targets with WT31 (anti-alphabeta antibody). Treatment of peripheral blood lymphocytes with IL-2 results in an enhancement of WT31-targeted lysis in 9 of 13 individuals evaluated. These findings demonstrate a differential response, in vitro, of CD8+ T-cells to IL-2 treatment. Future work evaluating clinical responses after IL-2 therapy with recovery of targeted lysis in vitro could provide information on screening of individuals for therapeutic intervention.

Quantitative alterations of the functionally distinct subsets of CD4 and CD8 T lymphocytes in asymptomatic HIV infection: changes in the expression of CD45RO, CD45RA, CD11b, CD38, HLA-DR, and CD25 antigens

We determined the representation in asymptomatic human immunodeficiency virus (HIV) infection of the CD45RO+ and CD45RO- CD45RA+ subsets of CD4+ and CD8+ T lymphocytes, CD11b+ and CD11b- subsets of CD8+ T cells, and activated populations of these subsets. Three-color flow cytometry was used to quantitate the different CD4+ and CD8+ T cell populations in 116 asymptomatic HIV+ individuals. In asymptomatic HIV+ infection there was a significant relative increase in the CD4+ CD45RO+ and CD8+ CD45RO+ T cell subsets, which express CD38 and DR antigens, that correlated strongly with the decline in total CD4+ T cells. In addition, we found a loss of CD4+ CD45RO- and CD8+ CD45RO- T cells associated with progression of HIV infection (as measured by the decline in total CD4+ T cells). Studies presented here also indicate that, with the progression of asymptomatic HIV infection, CD8+ CD11b- T lymphocytes showed a significant decrease, whereas CD8+ CD11b+ T cells were significantly increased. This study demonstrates that the progression of HIV infection in asymptomatic patients involves the increase in CD45RO+ subsets of CD4+ and CD8+ T cells, the increase in CD8+ CD11b+ T cells, the decrease in CD45RO- CD45RA+ subsets of CD4 and CD8 T cells, and the decline in CD8+ CD11b- T cells.

Immunodeficiency in non-tuberculous mycobacterial disease

T-cell immunity was investigated in eight patients with non-tuberculous mycobacterial disease, to see whether impaired immune function might be the explanation for their infection. Cellular immune function was evaluated in vitro by measuring the proliferation of peripheral blood mononuclear cells in response to both non-specific mitogens (phytohaemagglutinin and pokeweed mitogen) and specific recall antigens (streptokinase-streptodornase and purified protein derivative from Mycobacterium tuberculosis), and in vivo, by measuring the skin test response to a panel of recall antigens. Functionally relevant T-lymphocyte sub-populations (CD4, CD8, activated CD3 and gamma/delta T-cells) were enumerated by two-colour flow cytometry. The results were compared with those for a group of patients with pulmonary tuberculosis, with groups of controls matched for age and smoking habit, and with a patient group receiving steroid treatment. The patients with non-tuberculous mycobacterial disease had poor or absent skin test responses; in vitro, their response to recall antigens was depressed, although their response to mitogens was normal. The patients had significantly raised levels of CD8 lymphocytes and activated T-cells, but lacked any circulating gamma/delta T-cells. There were also differences between the various control groups. In conclusion, this study demonstrates a deficiency in the cellular immune system of these patients, which is most readily detectable by skin testing, or by measuring lymphocyte proliferative responses to recall antigens. However, the study also shows changes in cellular immune responses in controls matched for age and smoking and in patients on steroid treatment, and underscores the need for matched controls. Further work needs to be done to ascertain whether the cellular immune deficiency is a cause of, or is caused by, the mycobacterial infections, and also to investigate the pathological significance of the alterations in T-cell sub-populations.

Increased expression of CD80, CD86 and CD70 on T cells from HIV-infected individuals upon activation in vitro: regulation by CD4+ T cells

T cells express CD28 and CD27 which transduce co-stimulatory signals after interaction with their ligands on antigen-presenting cells (APC). These ligands, CD80, CD86 and CD70, are also expressed to some extent on activated T cells. Here, we show that in human immunodeficiency virus (HIV)-infected individuals, CD28 and CD27 expression is decreased on CD8+ T cells. On the other hand, T cell stimulation in vitro induced high CD80, CD86 and CD70 expression on T cells from HIV-infected individuals. It appeared that an inverted CD4:CD8 T cell ratio could explain this enhanced expression of co-stimulatory ligands. Indeed, high expression levels of CD80, CD86 and CD70 were found on activated CD8+ T cells from HIV- individuals cultured in the absence of CD4+ T cells. Addition of CD4+ T cells prevented this up-regulation. However, in HIV-infected individuals, addition of excess autologous or healthy control CD4+ T cells did not completely counteract up-regulation of co-stimulatory ligand expression on CD8+ T cells. Thus, to some extent, CD8+ T cells in HIV-infected individuals appeared to be refractory to CD4+ T cell-mediated regulation of ligand expression in vitro. Activated T cells from HIV-infected individuals and activated CD8+ T cells from healthy controls were able to act as accessory cells in CD3-induced T cell proliferation, which was dependent on cell-cell contact. Thus, we showed that T cells from HIV-infected individuals express enhanced levels of co-stimulatory ligands upon activation, which provides them with accessory cell properties. Enhanced stimulatory potential of these nonprofessional APC may contribute to persistently high levels of immune activation in HIV infection related to disease progression.

CD8+ lymphocyte decrease in HIV disease: association with anti-CD4+ but not with anti-CD8+ lymphocyte autoantibodies

HIV+ patients form autoantibodies against CD4+ and CD8+ lymphocytes. It was shown that anti-CD4+ lymphocyte autoantibodies are associated with the depletion of CD4+ cells. In the present study we analyzed the relationship of anti-CD4+ and anti-CD8+ autoantibodies with the CD8+ lymphocyte decrease commonly observed during HIV disease. IgM and IgG antibodies as well as complement fragments were determined on the surface of CD4+ and CD8+ lymphocytes using double fluorescence flow cytometry. Anti-CD8+ lymphocyte autoantibodies were found more often in HIV + hemophilia patients (75/105 = 71%) than HIV- hemophilia patients (13/37 = 35%; p < 0.0001), patients with pharyngeal carcinoma (20/44 = 45%; P = 0.002), habitual abortions (3/13 = 23%; p = 0.0009) or healthy individuals (93-223 = 42%; p < 0.0001). Anti-CD8+ antibodies, mostly of the IgM type, occurred significantly more frequently than anti-CD4+ antibodies in healthy controls (p < 0.0001), patients with pharyngeal carcinoma (p = 0.0001), or HIV- patients (p = 0.01). In HIV+ patients, however, anti-CD4+ autoantibodies were found more often than anti-CD8+ antibodies (85 vs 71%; p = 0.02). 70 of 104 (67%) HIV+ patients had autoantibodies on both CD4+ and CD8+ lymphocytes and the IgG/IgM/C3d autoantibody pattern was identical in 31 (44%) of the patients. Interestingly, peripheral blood CD8+ cell counts were significantly associated with anti-CD4+ (p = 0.01) but not with anti-CD8+ lymphocyte autoantibodies. It is hypothesized that the inhibition and depletion of CD4+ cells by anti-CD4+ autoantibodies is associated with a loss of regulatory functions that leads to a depletion of antiviral cytotoxic CD8+ lymphocytes.

Immunological and virological markers of HIV-disease progression

This review, based upon scientific literature, evaluates a number of immunological and virological markers for their usefulness as prognostic indicators for progression of HIV disease. The most widely studied marker, the CD4 positive T lymphocyte count, is perhaps the best single indicator of stage of illness. Serum factors such as neopterin and beta-2 microglobulin, alone and in combination with CD4 cell counts, have been shown to have good predictive value. Measurement of viral burden by quantification of viral RNA levels in plasma and immune cells also holds promise for following disease progression. It is recommended that a combination of these factors be monitored in evaluating stage of illness and responses to therapy in HIV-infected persons.

Depression in caregivers of demented patients is associated with altered immunity: impaired proliferative capacity, increased CD8+, and a decline in lymphocytes with surface signal transduction molecules (CD38+) and a cytotoxicity marker (CD56+ CD8+)

Changes in relevant immune parameters, including function, were found to be associated with depression in elderly caregiver wives of demented patients. We studied the relationship between immune cell phenotype and T cell proliferative capacity of such caregivers to levels of stress and depression over the course of a support group intervention. The data indicate the strongest association between depression (of all stress parameters) and impaired T cell proliferative capacity. Depression was also most strongly (of stress parameters) associated with a shift in T cell populations with an increase in CD8+ T cells, and a reduced percentage of CD38+ cells in both CD8+ and CD4+ T cell populations. Since CD38 is a signal transduction factor, it was interesting that a decreased percentage of CD38+ cells correlated with impaired T cell function (proliferation). Another significant difference was the reduction in natural killer (NK) cells as well as the percentage of the CD56+ component of the CD8+ population. This latter subset is important in MHC-unrestricted cytotoxicity, and has been found expanded in healthy centenarians. This study shows that both chronic stress, and depression in particular, and age have deleterious effects on T cells, and together could significantly contribute to the higher risk of disease and mortality associated with being a caregiver of a demented individual.

Presence of CD3+CD8+Bcl-2(low) lymphocytes undergoing apoptosis and activated macrophages in lymph nodes of HIV-1+ patients

Infection with human immunodeficiency virus 1 causes profound changes in the lymph nodes of infected patients. In particular, large numbers of CD8+CD45RO+ T cells infiltrate both the paracortex and the germinal centers. These cells contained the cytotoxic granule-associated protein TIA-1 but showed no detectable levels of perforin and shared the same characteristics of the expanded, activated, short-lived CD8+ population found during acute viral infections. These cells expressed low levels of Bcl-2 and are likely to be short-lived in vivo as evidenced by the direct observation of CD8+ apoptotic cells in the paracortical areas of the infected nodes. Changes in the paracortical nonlymphoid populations were also seen. There were reactive changes in the blood vessels, and the macrophage population was expanded and activated. Furthermore, apoptotic bodies were seen in the cytoplasm of the activated CD68+RFD-7+RFD-1+ macrophages pointing to the phagocytic capacity of these cells and their role in the clearance of the apoptotic cells from the tissues. These observations suggest that the persistance of CD8+ population in human immunodeficiency virus 1 infection is not a result of the presence of an abnormal CD8+ population but rather a result of an inappropriate over-stimulation of the CD8+ cells.

Programmed cell death induced by HIV type 1 antigen stimulation is associated with a decrease in cytotoxic T lymphocyte activity in advanced HIV type 1 infection

The immune competence of peripheral blood mononuclear cells (PBMCs) from human immunodeficiency virus-seropositive (HIV+) patients was studied by assessing cytotoxic T lymphocyte (CTL) activity following recall HIV antigen stimulation. Target cells were HLA-A-matched EBV-transformed B cells expressing HIV-1 antigen. In the presence of recombinant IL-2 (rIL-2, 2 or 10 U/ml), about 50% of PBMCs from HIV+ asymptomatic patients responded to HIV-1 antigen stimulation in vitro with increased cytotoxic activity. In contrast, PBMCs from patients with overt AIDS, cultured in medium containing rIL-2 (2 U/ml) and HIV-1 antigen, showed no increase in cytotoxic activity; in the presence of rIL-2 (10 U/ml) and HIV-1 antigen, an inhibitory effect on CTL activity was observed. This inhibitory effect was associated with programmed cell death (apoptosis) of CD8+ lymphocytes and cells of both gamma/delta TcR-positive and -negative phenotypes. However, prior to the apoptosis, different TcR phenotypes of T lymphocyte reacted differently to HIV-1 antigen stimulation. The HIV-1 antigen initially appeared to cause gamma/delta TcR-positive T lymphocytes to proliferate and/or differentiate and later induced cell death. Whereas, prior to the apoptosis, no proliferation of gamma/delta TcR-negative T lymphocytes induced by HIV-1 antigen was observed.

Age-related ranges of memory, activation, and cytotoxic markers on CD4 and CD8 cells in children

The expression of markers defining functional subpopulations on the surface of CD4 and CD8 cells changes with disease. To monitor these changes in children, it is important to establish the age-related normal changes in marker expression due to maturation of the immune system. We have studied the expression of several functionally important molecules on both CD4 and CD8 cells in 168 children (aged 0-122 months) using monoclonal antibodies and flow cytometry. Our results show that the percentage of CD4 cells decreases with age, while the CD8 percentage increases, resulting in a decrease in the CD4/CD8 ratio. The expression of CD45RO and CD29 increases with age, while CD45RA expression decreases, both on CD4 and CD8 cells. The expression of HLA-DR on both CD4 and CD8 cells, and of CD11a and CD57 on CD8 cells, is less clearly age dependent. The relationships between the marker percentages and age were not straightforward; the standard deviations and the skewness, as well as their mean values, varied as a function of age. The changes were modeled for each marker and age-specific centiles are presented.

Clinical and immunologic evaluation of HIV-infected patients treated with dinitrochlorobenzene

BACKGROUND

Promotion of cell-mediated immunity appears to be an important goal in the control of HIV infection. Topical dinitrochlorobenzene (DNCB) stimulates systemic cell-mediated immunity via the induction of cutaneous delayed-type hypersensitivity.

OBJECTIVE

Our goal was to evaluate the clinical and immunologic effects of chronic DNCB application in a group of 24 HIV-infected patients.

METHODS

We observed the patients for a mean of 28 months (range, 14 to 44 months). Of the 24 patients, 13 continued weekly DNCB application throughout the study (the compliant group), and 11 discontinued DNCB use after a mean of 10.9 months (the noncompliant group).

RESULTS

Two of the 13 compliant patients progressed to AIDS; none of these patients died. In contrast, AIDS developed in 5 of the 11 noncompliant patients and four of these patients died. Analysis of lymphocyte subsets revealed significant increases in natural killer cells and activated/cytotoxic CD8 T-cell subsets in the compliant group. In contrast, these cellular immune-related lymphocyte subsets decreased in the noncompliant subjects. Although CD4 T-cell levels decreased in both groups, there was a significantly greater drop in the noncompliant patients. CD8+CD38+ T cells increased significantly in both groups.

CONCLUSION

Chronic DNCB application appears to have a beneficial clinical and immunomodulatory effect in HIV-infected patients.

Cytotoxic T lymphocyte activity and CD8 subpopulations in children at risk of HIV infection

HIV-specific cytotoxic T lymphocytes (CTL) are thought to play a major role in viral control in HIV-infected adults. Changes in the relative proportions of CD8 lymphocyte subpopulations are also thought to be associated with disease progression. Less is known about the relative effectiveness of CTL against different HIV targets, or about the relationship, if any, between CTL activity and CD8 subpopulations. We have measured CTL activity against four HIV gene products (gag, tat, pol and env) and expression of CD45RO, CD45RA, HLA-DR, CD29, S6F1, and CD57 surface markers on CD8 cells from nine HIV-infected and 11 HIV-uninfected children. Of nine HIV-infected children, six showed antigen-specific CTL activity on at least one occasion: 4/6 directed against tat, 6/6 against pol, 1/6 against env, and 1/6 against gag. However, the specificity of the CTL activity varied between children and within individual children with time. Furthermore, two uninfected children showed CTL activity, one to HIV-gag, -pol and -tat, and the other to HIV-pol. All the HIV-infected and two uninfected children had abnormal proportions of CD8 subpopulations in whole blood compared with age-matched controls. There was no correlation between CTL activity and CD8 subsets in whole blood. Five children changed from CTL-positive to CTL-negative (or vice versa) during the study. In these, the occasions when CTL activity was detected coincided with an increase in CD8 cells, an expansion of HLA-DR+ CD8 cells and a loss of CD45RA+ CD8 cells.

Abnormalities in subset distribution, activation, and differentiation of T cells isolated from large intestine biopsies in HIV infection. The Berlin Diarrhoea/Wasting Syndrome Study Group

Intestinal T cells have a unique state of activation and differentiation which might specifically affect or be affected by HIV infection. Lymphocyte subsets in the peripheral blood are well characterized, but our knowledge about intestinal lymphocytes in HIV infection is incomplete. We therefore analysed lymphocytes isolated from large intestine biopsies of AIDS patients and controls by three-colour cytofluorometry. In the large intestine of HIV-infected patients CD4 T cells were reduced and CD8 T cells were increased compared with controls. Most of the CD8 T cells in the colorectal mucosa of AIDS patients were of the cytotoxic phenotype. Activated and resting CD4 T cells were similarly reduced, the expression of CD25 and HLA-DR of CD8 T cells was unaltered and increased, respectively. In intestinal CD4 T cells the expression of CD29 was decreased, but the expression of CD45RO and HML-1 was normal. CD8 T cells had a decreased expression of all these differentiation markers. Our findings demonstrate substantial alterations in subset distribution, activation, and differentiation of large intestine T cells, which may contribute to the secondary infections and malignancies commonly observed in the gut of AIDS patients.

Lack of correlation between phenotype activation markers of CD8 lymphocytes and cytotoxic T lymphocyte (CTL) function in HIV-1 infection: evidence for rescue with rIL-2

CTL activity against HIV-1 antigens expressed on HLA-A-matched EBV-transformed B target cells was detected in 33% (6/18) of freshly isolated PBMC (FPBMC) from patients in the early stages of HIV-1 infection (CDCII). No CTL activity was detected in FPMBC in patients with AIDS (CDCIV). However, the presence of CTL activity did not correlate with the expression of CTL activation markers. A dual-color flow cytometric examination revealed that the CD8+ lymphocytes bearing the memory (CD29) and activation (S6F1) surface molecules increased in number as the HIV-1 infection progressed. This functional and phenotypic discrepancy in memory CD8+ lymphocytes suggests that the memory CD8+ lymphocytes have lost cytotoxic function and become "paralyzed" as the HIV disease progresses. Incubation of PBMC of HIV(+) patients with rIL-2 reactivated predominantly HIV-specific CTL. However, rIL-2 stimulation also activated a "polyclonal or polyreactive" cytotoxic function. The reactivation of CTL function is rIL-2 dosage dependent and the amount of rIL-2 required for reactivation is associated with the severity of the disease. HIV antigen specific CTL in HIV(+) patients can be selectively expanded by HIV antigen stimulation in the presence of rIL-2. These results suggest that the in vivo IL-2 deficiency occurring in HIV-1 infection may be responsible in part for the "paralysis" of HIV specific CTL activity. Such activity can be rescued nonspecifically by exogenous rIL-2 stimulation and expanded specifically by HIV-1 antigen stimulation.

Soluble tumour necrosis factor receptors (sTNF-R) and HIV infection: correlation to CD8+ lymphocytes

The objective of this study was to determine sTNF-R, type I (p55) and type II (p75) in sera of HIV-infected male homosexuals and correlate them to T lymphocyte subpopulations and course of HIV infection. Serum samples were obtained from 39 HIV-1+ asymptomatic male homosexuals, 10 symptomatic (ARC and AIDS) male homosexuals and 44 HIV- non-homosexual healthy controls. sTNF-R levels were determined by ELISA with specific MoAbs and polyclonal antibodies to the sTNF-R proteins. sTNF-RI and II levels were significantly elevated in 72% and 74% respectively of HIV+ asymptomatic male homosexuals and in all of the symptomatic male homosexuals. In sequential studies a highly significant positive correlation was found between sTNF-RI and sTNF-RII (r = 0.8, P < 0.001) and between both sTNF-R and CD8+ lymphocyte counts (r = 0.6 and 0.92, respectively, P < 0.01-0.001) during the asymptomatic stage of the infection. All these correlations were lost, however, during the symptomatic phase of the disease. These results suggest that: (i) HIV infection is associated with elevation of sTNF-R serum levels; (ii) sTNF-R levels are strongly correlated to CD8+ lymphocytes during the asymptomatic stage of HIV infection.