HIV infection perturbs DNA content of lymphoid cells: partial correction after 'suppression' of virus replication

Cell cycle distribution of CD4+ lymphocytes in HIV-1-infected subjects

BACKGROUND

Apoptosis is one of the possible explanations for the progressive loss of CD4(+) T lymphocytes in infection with the human immunodeficiency virus (HIV), which may interfere with cell cycle distribution. This study evaluated the cell cycle of CD4(+) and CD8(+) lymphocytes in HIV-infected subjects and controls.

METHODS

Two methods to identify lymphocytes for cell cycle analysis were evaluated, magnetic beads and concurrent staining, and both were followed by propidium iodide DNA labeling. The chosen method was used to evaluate the cell cycle of lymphocytes in HIV-1-infected subjects and controls.

RESULTS

There was no significant difference between the two methods, although a higher variability was observed with the magnetic bead cell separation method. A higher proportion of cells in the S phase was observed in HIV-1 patients (2.69% vs. 1.19%, P = 0.016), coupled with a decrease in G(1) (96.11% vs. 98.10%, P = 0.005) in CD4(+) lymphocytes, a phenomenon not observed in CD8(+) lymphocytes. No correlation was detected between the different cell cycle phases and T-lymphocyte counts or viral load.

CONCLUSIONS

The present work developed a new approach to evaluate lymphocyte cell cycle distribution, applied in the setting of HIV-1 infection. It may contribute to the understanding of the CD4(+) T-lymphocytes depletion seen in these patients.

Correlates of immune activation marker changes in human immunodeficiency virus (HIV)-seropositive and high-risk HIV-seronegative women who use illicit drugs

The majority of natural history studies of human immunodeficiency virus (HIV) infection have immune and viral parameters in men. Data demonstrating that women have lower HIV-1 RNA levels than men at the same CD4 cell counts have raised the question of immunologic differences in HIV-seropositive women. This study describes levels and changes in phenotypic markers of immune maturity, function, and activation in the CD4 and CD8 cell subsets in HIV-seropositive and high-risk HIV-seronegative women. Our primary hypothesis was that activation levels would be significantly higher among illicit drug users. However, results showed that HIV-1 RNA level was the strongest predictor of marker level and that both HIV-1 RNA level and CD4 cell count were independently associated with CD4 activation, but illicit drug use was not. In summary, this study demonstrated that immune activation was a significant pathogenic feature in women and that activation was driven by HIV infection and not illicit drug use.

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.

Multiple CD4+ cell kinetic patterns and their relationships with baseline factors and virological responses in HIV type 1 patients receiving highly active antiretroviral therapy

This exploratory analyses characterizes patterns of lymphocyte recovery in HIV-1-infected patients treated with highly active antiretroviral therapy (HAART) and investigates their relationship with baseline indices and virologic responses. We modeled kinetics of total CD4+ lymphocytes, as well as naive (CD45RA+ CD62L+), and memory (CD45RA- CD45RO+) subsets in 48 patients treated with AZT/3TC/Ritonavir for 48 weeks in ACTG protocol 315. Cell kinetic indices were estimated by nonlinear regression methods and were correlated with baseline factors and virologic responses. Five different kinetic patterns were identified, including biphasic growth, growth-plateau, growth-depletion, decay-recovery, and biphasic decay. Although overall mean lymphocyte responses showed a biphasic increase in cell number, a careful investigation reveals that only one-third of patients actually followed the biphasic growth pattern in CD4+ cell response, while 44% of 48 patients from this study followed the growth-depletion pattern. CD4+ cell recovery during the first phase and the 48-week study period were negatively correlated with baseline CD4+ cell counts, and positively correlated with baseline viral load. Memory CD4+ cell recovery during the first phase was also negatively correlated with baseline memory CD4+ and total CD4+ cell number, but the recovery rate of memory CD4+ cells during the second phase was positively correlated with baseline CD4+ cell number. Patients with a decay in CD4+ cell count during treatment were more likely to have experienced virological rebound (58%) than patients with nondecay patterns (24%). The rate and magnitude of the absolute increase in total CD4+ and memory CD4+ cell number (but not naive CD4+ cells) during the second phase were lower in patients with viral rebound compared with patients with persistent viral suppression. These results show that the kinetics of lymphocyte reconstitution in response to potent antiretroviral therapy in individual patients vary considerably from the "classic" biphasic increase that characterizes the mean or median response pattern. Pattern analysis of lymphocyte kinetics may be useful for testing relationships among factors that modulate the response to treatment.

Placebo-controlled trial of prednisone in advanced HIV-1 infection

OBJECTIVE

To examine the safety and the immunologic and virologic consequences of corticosteroid use in HIV-1 infection.

METHODS

A randomized, double-blinded, placebo-controlled trial of corticosteroid administration in 41 patients with advanced HIV-1 infection. Patients had a baseline median CD4 cell count of 131 x 10(6) cells/l at enrollment and 85% had a history of opportunistic infection. All but one of the patients had been taking stable antiretroviral regimen, including a protease inhibitor in 36, for a median duration of 158 days. Patients were randomized to 8 weeks of prednisone 0.5 mg/kg daily or placebo.

RESULTS

No AIDS-defining events occurred; two patients in each group developed oral candidiasis, and two patients on prednisone developed mild herpes simplex flares. None who developed oral candidiasis or herpes simplex was receiving prophylaxis and each responded promptly to therapy. In the prednisone group, two patients developed hyperglycemia and one diabetic increased insulin requirements. CD4 cell counts and plasma HIV-1 RNA levels did not change, but plasma tumor necrosis factor alpha levels and CD38+ CD8+ cells decreased significantly in those taking prednisone.

CONCLUSION

Short-term prednisone administration is well tolerated and reasonably safe in advanced HIV-1 disease and decreases immune activation without effects on HIV-1 RNA levels or CD4 cell counts. These results suggest that, in stable HIV-1 disease, these immune activation markers are more likely consequences of but not inducers of HIV-1 replication.

Immune restoration and CD4+ T-cell function with antiretroviral therapies

OBJECTIVES

To review the current understanding of the details and mechanisms of immune restoration that follows administration of suppressive antiretroviral therapies to persons with chronic HIV-1 infection.

SUMMARY

A first-phase cellular increase often includes increases in multiple circulating lymphocyte populations and is largely attributable to rapid redistribution of cells from lymphoid tissue. A second slower phase is largely comprised of naïve cell increases that may reflect cells newly produced in the thymus. Improvement in CD4+ cell function is demonstrable but functional restoration is incomplete. Immunization can enhance the restoration of CD4+ cell-dependent responses, and the magnitude of restoration is related in part to the degree to which HIV-1 replication and immune activation are controlled. Despite the incomplete nature of immune restoration seen after suppression of HIV-1 replication in chronic infection, clinical benefits of these responses are reflected in decreased HIV-1-related opportunistic infections and mortality. The effects of these therapies on the occurrence of non-Hodgkins lymphoma are less apparent.

CONCLUSIONS

Suppression of HIV-1 replication results in both laboratory and clinical evidence of immune restoration. Although incomplete, this immune restoration provides 'breathing room' to develop better-tolerated antiviral therapies and therapies designed to enhance immune function.

Preferential S phase entry and apoptosis of CD4(+) T lymphocytes of HIV-1-infected patients after in vitro cultivation

We have studied the relationship between spontaneous apoptosis and cell cycle perturbations in circulating peripheral blood lymphocytes of HIV-1-infected patients and healthy controls. PBMC obtained from HIV-1-infected patients and healthy controls were incubated in culture medium for 48 h. Cells were separated into CD4(+) and CD8(+) populations using immunomagnetic beads. Apoptosis and cell cycle phases were measured by propidium iodide staining and bromodeoxyuridine (BrdU) incorporation followed by flow cytometric analyses. In experiments using cells obtained from HIV-1-infected patients, spontaneous apoptosis was more frequent in CD4(+) T lymphocytes than in CD8(+) T lymphocytes (17.6% vs 9.5%, P < 0.005). Among healthy controls, spontaneous apoptosis in CD4(+) and CD8(+) T lymphocytes was comparable (4.5% vs 5.1%). Lymphocytes obtained from patients were more frequently in S phase than healthy controls' cells (2.2 +/- 0.9% vs 0.5 +/- 0.2%, P < 0.002) and patients' CD4(+) cells tended to enter S phase more frequently than controls' CD4(+) cells (4.2% +/- 3.5% vs 1.8% +/- 0.5% P < 0.04), whereas the frequency of S phase CD8(+) T cells was not different among patients (2.8% +/- 2.9%) and controls (1.8% +/- 0.5%) (P > 0.4). Kinetic analyses using BrdU and PI staining revealed that S phase cells were more likely to become apoptotic than resting (G(0)-G(1)) cells (28.4% +/- 10.3% vs 11.3% +/- 9.9% in patients, P < 0.04, and 15.3% +/- 2.8% vs 1.8% +/- 0.5% in controls, P < 0.003). Lymphocytes obtained from HIV-1-infected persons are activated in vivo to enter S phase and to undergo spontaneous apoptosis after brief in vitro cultivation. The present studies indicate that most apoptotic cells in this system are CD4(+) and kinetic analyses reveal that S phase cells are more likely to undergo spontaneous apoptosis than G(0)-G(1) cells. Accelerated cell death in HIV-1 disease may contribute to the failure of lymphocyte responsiveness to appropriate T cell receptor stimulation.

Cellular restoration in HIV infected persons treated with abacavir and a protease inhibitor: age inversely predicts naive CD4 cell count increase

OBJECTIVE

To characterize early and later indices of cellular restoration among HIV-1 infected persons treated with abacavir and one protease inhibitor and to identify predictors of CD4 cell increases.

METHODS

Flow-cytometric analyses of lymphocyte phenotypes among 71 antiretroviral treatment naive adults in a 48 week treatment trial.

RESULTS

During the first 4 weeks of therapy, increases in naive and memory CD4 cells and in B cells were seen; naive CD8 cells increased while CD8 cells remained stable as memory CD8 cells decreased. During the second phase total CD4 and naive CD4 and CD8 cells increased while total CD8 and memory CD8 cells decreased. The numbers of CD4 cells that expressed CD28 increased from a median of 308 x 10(6)/l at baseline to 477 x 10(6)/l at week 48. Higher baseline plasma HIV-1 RNA levels predicted the magnitude of early CD4 (r = 0.35; P = 0.01), memory CD4 (r = 0.38; P = 0.001) and CD28 CD4 cell (r = 0.29; P = 0.01) restoration but was not related to second phase changes. Younger age predicted a greater second phase (but not first phase) increase in naive CD4 cells (r = -0.31; P = 0.03).

CONCLUSIONS

Higher baseline levels of HIV-1 replication determine the magnitude of first phase CD4 cell increases after suppression of HIV-1 replication. Second phase (primarily naive) CD4 cell increases are not related to HIV-1 replication but are inversely relate to age suggesting that thymic potential is a major determinant of long term cellular restoration in HIV-1 infected persons receiving antiretroviral therapy.

Apoptosis and apoptosis-associated perturbations of peripheral blood lymphocytes during HIV infection: comparison between AIDS patients and asymptomatic long-term non-progressors

This study was designed to compare the degree of lymphocyte apoptosis and Fas-Fas ligand (FasL) expression in AIDS patients and long-term non-progressors (LTNPs) and correlate these parameters with apoptosis-associated perturbations in lymphocyte function. LTNPs had a lower frequency of apoptotic CD4+ and CD8+ T cells compared with subjects with AIDS. This correlated with a lower frequency of cells expressing Fas and FasL. The frequency of selected lymphocyte populations exhibiting a disrupted mitochondrial transmembrane potential (DeltaPsim) and increased superoxide generation was lower in LTNPs than in patients with AIDS; these abnormalities were associated with lower levels of caspase-1 activation in LTNPs. The results indicate a significantly reduced level of apoptosis and apoptosis-associated parameters in LTNPs than in patients developing AIDS. Based on these findings, a crucial role for mitochondria can be predicted in the process of lymphocyte apoptosis during the evolution of AIDS.

Response to immunization with recall and neoantigens after prolonged administration of an HIV-1 protease inhibitor-containing regimen. ACTG 375 team. AIDS Clinical Trials Group

OBJECTIVES

To ascertain if immunization results in the restoration of responses to recall antigens, in the development of responses to presumed neoantigens, and to identify the virologic and immunologic correlates of these responses in persons with HIV-1 infection.

DESIGN AND SETTING

Open-label study carried out at three university-affiliated AIDS Clinical Trials Units in the United States.

SUBJECTS AND METHODS

Thirty-one subjects participating in AIDS Clinical Trials Group Protocol 375 who had received zidovudine, lamivudine, and ritonavir for at least 48 weeks. Subjects were immunized with tetanus toxoid (TT) at entry and with inactivated hepatitis A vaccine (hep A) and keyhole limpet hemocyanin (KLH) at entry and 6 weeks. The development of antibody, lymphocyte proliferative assay (LPA), and delayed-type hypersensitivity (DTH) responses after immunization were monitored.

RESULTS

The LPA and DTH responses to TT improved in 57 and 68% of participants, respectively; 73 and 65% developed enhanced LPA and DTH responses to KLH. Forty-eight percent of patients developed a four-fold increase in antibody concentration to tetanus. Seventy-three percent of patients without detectable hepatitis A antibodies at baseline developed antibodies after immunization. Eighty-three percent of patients experienced at least a four-fold rise in KLH antibody concentration. Immune activation and viral load predicted poor recall responses and the number of memory CD4+ T-cells predicted good responses to recall antigens. Naïve CD4+ T-cell numbers, decrease in viral load, increases in CD4+ and CD28+ cells, and decreases in immune activation were associated with responses to presumed neoantigens.

CONCLUSIONS

Most HIV-infected patients treated with potent combination antiretrovirals develop responses to recall and presumed neoantigens after immunization. Functional immune restoration in response to immunization is related to control of viral replication, decreased immune activation as well as to both quantitative and qualitative restoration of circulating T- lymphocyte subpopulations.

Lymphocyte proliferation assays may underestimate antigen responsiveness in human immunodeficiency virus infection

The objective of this study was to examine the relationships among lymphocyte proliferation, interferon-gamma (IFN-gamma) production, and apoptosis in peripheral blood mononuclear cells (PBMC) of HIV-1-infected patients and controls. PBMC were prepared from 19 HIV-1-infected patients and 16 healthy controls. Using tetanus toxoid (TT) as a recall antigen, we assessed lymphocyte proliferation using [(3)H]thymidine incorporation after 2, 4, 6, and 7 days' culture and IFN-gamma production in 48-h culture supernatants by ELISA. Apoptosis was measured using TdT-mediated dUTP nick-end labeling. Median stimulation indices (SIs) in HIV-1-infected patients were 2.8 and 3.7 as opposed to 24.9 and 25.1 in healthy controls after 6 and 7 days' culture, respectively (P < 0. 001). Among the controls, peak proliferation was seen after 7 days in culture whereas in patients, SIs peaked at 4 days and fell progressively by days 6 and 7. At 2 and 4 days of stimulation with tetanus, patients' T cells showed increased apoptosis (19 and 25%) vs 12 and 15% apoptosis seen in controls' cells, P < 0.05. Interferon-gamma in 48-h supernatants of TT-stimulated PBMC was comparable among patients and controls. Whereas in our system, 6 and 7 day assays of lymphocyte proliferation provide increasing responses to TT among healthy controls, these durations of culture may underestimate antigen responsiveness in HIV-1 infection. Cell death due to apoptosis may account for this phenomenon. Whether shorter term or longer term assays of lymphocyte responsiveness more accurately reflect in vivo immune competence is unknown. Nonetheless, shorter duration assays may provide a more realistic estimate of the frequency of antigen-reactive cells in persons with HIV-1 infection.