Low T-cell responses to CD3 plus CD28 monoclonal antibodies are predictive of development of AIDS

Production of anti-CD3/28 expanded CD4⁺ T lymphocytes from HIV-infected patients with different degrees of disease progression

AIMS

CD4+ T lymphocytes from HIV-infected patients with different degrees of disease progression based on CD4 count were expanded in vitro using anti-CD3/28-coated beads.

MATERIALS & METHODS

Purified CD4+ T lymphocytes from healthy subjects and patients were expanded for 3 weeks. Moreover, the improvement of cell expansion by IL-2 supplementation was also determined.

RESULTS

Expanded CD4+ T lymphocytes from patients had lower fold expansion when compared with healthy subjects. Furthermore, patients with high CD4 counts had higher fold expansion than patients with low CD4 count, and IL-2 supplementation further increased cell expansion.

CONCLUSIONS

Anti-CD3/28 activation failed to potently induce expansion of CD4+ T lymphocytes from patients. However, the cell expansion could be improved by IL-2 supplementation.

In vitro naïve T cell proliferation failure predicts poor post-immunization responses to neoantigen, but not recall antigens, in HIV-infection

Immune reconstitution after HAART is incomplete, but no widely accepted method to quantify subclinical immune deficiency is available. We immunized 9 HIV-negative subjects and 29 HIV-infected patients with CD4>/=450 cells/microL and undetectable HIV RNA levels with 2 doses of diphtheria/tetanus toxoid (TT) and KLH, a presumed neoantigen. We quantified the response by lymphoproliferative assay, delayed-type hypersensitivity (DTH), and antibody titers up to 59days after enrollment. We assessed T cell proliferative capacity using anti-Vbeta3 and anti-Vbeta5 antibody stimulation, which we herein show induced predominant proliferation of naïve T cells. Subjects with detectable responses to KLH tended to exhibit greater proliferative responses to anti-Vbeta3/Vbeta5 stimulation; no such pattern was seen with response to TT. Several measures of in vitro T cell proliferative capacity correlated significantly with DTH and antibody responses to KLH, but not with TT responses; this association was independent of naïve T cell numbers. Our results indicate that naïve T cell proliferation predicts response to neo-, but not recall antigens, and suggest that it may be a meaningful reflection of in vivo immune competence in HIV-infected persons.

HIV-induced changes in T cell signaling pathways

Infection with HIV usually results in chronic activation of the immune system, with profound quantitative and qualitative changes in the T cell compartment. To better understand the mechanistic basis for T cell dysfunction and to discern whether such mechanisms are reversed after effective antiviral treatment, we analyzed changes in signaling pathways of human CD4(+) and CD8(+) T cells from 57 HIV-infected subjects in varying stages of disease progression and treatment, including long-term nonprogressors, progressors, and chronically infected subjects provided effective antiretroviral therapy (responders). A previously described PhosFlow method was adapted and optimized so that protein phosphorylation could be visualized in phenotypically defined subpopulations of CD4(+) and CD8(+) T cells (naive, memory, and effector) by flow cytometry. T cell signaling induced by TCR cross-linking, IL-2, or PMA/ionomycin was found to be blunted within all T cell subpopulations in those with progressive HIV disease compared with long-term nonprogressors and responders. Although alterations in cellular signaling correlated with levels of basal phosphorylation, viral load, and/or expression of programmed death-1, it was the level of basal phosphorylation that appeared to be the factor most dominantly associated with impaired signaling. Notably, provision of effective antiretroviral therapy was associated with a normalization of both basal phosphorylation levels and T cell signaling. These data, in aggregate, suggest that generalized dysfunction of the T cell compartment during progressive HIV disease may be in part dependent upon an increased basal level of phosphorylation, which itself may be due to the heightened state of immune activation found in advanced disease.

Chimpanzee CD4+ T cells are relatively insensitive to HIV-1 envelope-mediated inhibition of CD154 up-regulation

CD40-CD154 interaction forms a key event in regulation of crosstalk between dendritic cells and CD4 T cells. In human immunodeficiency virus (HIV)-1 infected patients CD154 expression is impaired, and the resulting loss of immune responsiveness by CD4+ T cells contributes to a progressive state of immunodeficiency in humans. Although chimpanzees are susceptible to chronic HIV-1/SIVcpz infection, they are relatively resistant to the onset of AIDS. This relative resistance is characterized by maintenance of CD4+ T cell populations and function, which is highly compromised in human patients. In our cohort of chronically HIV-1- and SIVcpz-infected chimpanzees, we demonstrated the capacity to produce IL-2, following CD3/CD28 stimulation, as well as preserved CD154 up-regulation. Cross-linking of CD4 with mAb was found to inhibit CD3/CD28-induced up-regulation of CD154 equally in chimpanzees and humans. However, specific cross-linking with trimeric recombinant HIV-1 gp140 revealed reduced sensitivity for inhibition of CD154 up-regulation in chimpanzees, requiring fourfold higher concentrations of viral protein. Chimpanzee CD4+ T cells are thus less sensitive to the immune-suppressive effect of low-dose HIV-1 envelope protein than human CD4+ T cells.

Persistent humoral immune defect in highly active antiretroviral therapy-treated children with HIV-1 infection: loss of specific antibodies against attenuated vaccine strains and natural viral infection

OBJECTIVE

In the pre-highly active antiretroviral therapy era, a loss of specific antibodies was seen. Our objective with this study was to describe the loss of specific antibodies during treatment with highly active antiretroviral therapy.

METHODS

In a prospective, single-center, cohort study of 59 children with HIV-1 infection, we investigated the long-term effect of highly active antiretroviral therapy on the titers and course of specific antibodies against measles, mumps, and rubella vaccine strains compared with wild-type varicella zoster virus, cytomegalovirus, and Epstein-Barr virus.

RESULTS

During highly active antiretroviral therapy, age-adjusted CD4+ T cells and B cells increased, whereas total immunoglobulin levels declined. Although these children were preimmunized before the start of highly active antiretroviral therapy, only 24 (43%) had antibodies against all 3 measles, mumps, and rubella. Antibodies against measles, mumps, and rubella were lost in 14 (40%), 11 (38%), and 5 (11%) children who were seropositive at baseline. We also observed loss of varicella zoster virus immunoglobulin G in 7 (21%) of 34, cytomegalovirus immunoglobulin G in 3 (7%) of 45, but none of 53 Epstein-Barr virus-seropositive children. During highly active antiretroviral therapy, primary vaccination in 3 patients and 15 revaccinations in those with negative serology demonstrated incomplete seroconversion.

CONCLUSIONS

Humoral reactivity in children with HIV-1 infection remains abnormal during highly active antiretroviral therapy. Despite immune reconstitution, antibodies against live-attenuated vaccine and wild-type natural virus strains disappear over time in up to 40% of children with HIV-1 infection.

Short communication: No detrimental immunological effects of mycophenolate mofetil and HAART in treatment-naive acute and chronic HIV-1-infected patients

Mycophenolate mofetil has been proposed for HIV-1 therapy because of its guanine-depleting effect, which is expected to interfere with HIV-1 replication directly by hampering reverse transcription and indirectly via inhibition of CD4+ T cell proliferation. However, treatment with mycophenolate mofetil might also compromise lymphocyte reconstitution and HIV-specific immunity. Therefore we longitudinally studied the effects of mycophenolate mofetil in combination with HAART on T cell proliferation, lymphocyte reconstitution, and HIV-specific CD4+ and CD8+ T cell responses in six therapy-naive, acute or chronic HIV-1-infected patients, as compared to eight patients treated with HAART alone. T cell proliferation in whole blood cultures of patients treated with mycophenolate mofetil was inhibited. Strikingly, ex vivo Ki67 expression within T cells was not influenced by treatment with mycophenolate mofetil. In vitro studies showed that Ki67 expression occurs at an early step of the cell cycle and was not inhibited by guanine depletion. When treatment with mycophenolate mofetil was stopped a transient increase in apoptosis and Ki67-expressing T cells was detected. This observation together with near complete inhibition of T cell proliferation in whole blood cultures during treatment with mycophenolate mofetil indicated that T cell proliferation was inhibited in patients treated with mycophenolate mofetil. Still, there was no evidence for detrimental effects of treatment with mycophenolate mofetil in addition to HAART on CD4+ T cell reconstitution or HIV-specific immunity.

Sustained Viral Suppression and Immune Recovery in HIV Type 1--Infected Children after 4 Years of Highly Active Antiretroviral Therapy

We report the data from a long-term study of 31 human immunodeficiency virus type 1 (HIV-1)-infected children who were treated with highly active antiretroviral therapy. A high proportion of the children had undetectable HIV-1 RNA levels. CD4+ T cell counts recovered and remained stable. Adverse events were observed frequently but were mostly mild.

Effect of mycophenolate mofetil on the pharmacokinetics of antiretroviral drugs and on intracellular nucleoside triphosphate pools

OBJECTIVE

To study the effect of mycophenolate mofetil therapy on the pharmacokinetic parameters of a number of antiretroviral drugs, on intracellular pools of deoxycytidine triphosphate (dCTP) and deoxyguanosine triphosphate (dGTP), and on intracellular concentrations of the triphosphate of lamivudine (3TCTP).

DESIGN

Randomised pharmacokinetic study.

PARTICIPANTS

Nineteen HIV-1-infected patients.

METHODS

Antiretroviral-naive men starting treatment with didanosine 400 mg once daily, lamivudine 150 mg twice daily, abacavir 300 mg twice daily, indinavir 800 mg twice daily, ritonavir 100 mg twice daily and nevirapine 200 mg twice daily were randomised to a group with or without mycophenolate mofetil 500 mg twice daily. After 8 weeks of therapy, the plasma pharmacokinetic profiles of mycophenolic acid (the active metabolite of mycophenolate mofetil), abacavir, indinavir and nevirapine, and triphosphate concentrations (dCTP, dGTP and 3TCTP) in peripheral blood mononuclear cells, were determined.

RESULTS

Nine of the 19 patients received mycophenolate mofetil. There was no difference in plasma clearance of indinavir or abacavir between the two groups. The clearance of nevirapine was higher in patients using mycophenolate mofetil (p = 0.04). In 12 patients, of whom five also received mycophenolate mofetil, intracellular triphosphates were measured. There was no significant difference in intracellular dCTP, dGTP or 3TCTP concentrations between the two groups.

CONCLUSION

In this small cohort of patients, mycophenolate mofetil therapy reduced the plasma concentration of nevirapine but had no effect on plasma concentrations of indinavir and abacavir. There were no consistent effects of mycophenolic acid on the intracellular concentrations of dCTP, dGTP or 3TCTP.

HIV-infected children with moderate/severe immune-suppression: changes in the immune system after highly active antiretroviral therapy

The objective of this study was to monitor the changes in the immune system of HIV-infected children with moderate or severe immunodeficiency after highly active antiretroviral therapy (HAART), comprising a follow-up study in 14 HIV-infected children on HAART at two time points separated approximately by 11.8 +/- 0.4 (9.9; 15.4) months. HIV-infected children had significantly lower TREC levels than the control group, but 1 year after HAART the levels increased significantly (P < 0.05). In contrast, viral load (VL) did not change significantly. A positive correlation between T cell receptor excision circle (TREC) levels and both CD4(+) T cell absolute counts (r = 0.558; P = 0.05) and percentages (r = 0.625; P = 0.030) was found. During follow-up on HAART, the percentages and absolute counts of naive CD4(+) and CD8(+) T cell subsets were increased significantly (P < 0.05). CD4(+) CD45RA(hi+) CD62L(+), CD4(+) CD45RA(+) and CD4(+) CD38(+) percentages, and the CD8(+) CD45RA(hi+) CD62L(+) counts reached similar values to the control group. Also, CD8(+) CD45RO(+) CD38(+) and CD8(+) CD45RO(+) percentages, and CD8(+) CD45RO(+) CD38(+) absolute counts (P < 0.05) decreased with respect to the baseline. Lymphoproliferative responses to pokeweed mitogen (PWM) before HAART were lower in HIV-infected children than the control group, but they recovered to normal levels after a year on HAART. Tumour necrosis factor (TNF)-alpha and interferon (IFN)-gamma production by PHA-activated peripheral blood mononuclear cells (PBMC) was lower before HAART (P < 0.001), but reached similar levels to the control group 1 year after HAART. In HIV-infected children IgG, IgG(1) and IgG(3) plasma levels decreased significantly after HAART. The immune system reconstitution induced by HAART in HIV-infected children seems to be the consequence of decreased immune system activation and naive T cell reconstitution, mainly of thymic origin.

Efficient lentiviral vector-mediated control of HIV-1 replication in CD4 lymphocytes from diverse HIV+ infected patients grouped according to CD4 count and viral load

We present preclinical studies that demonstrate in vitro the feasibility and efficacy of lentivirus-based vector antisense gene therapy for control of HIV replication in primary T lymphocytes isolated from HIV-infected patients discordant for clinical status. VRX496 is a VSV-G-pseudotyped HIV-based vector that encodes an antisense payload against the HIV envelope gene. The antisense payload is under the control of the native LTR promoter, which is highly transactivated by tat upon HIV infection in the cell. Transfer of autologous CD4(+) T lymphocytes genetically modified with VRX496 (VRX496T) into HIV-infected patients is intended to provide a reservoir of cells capable of controlling HIV, potentially delaying AIDS onset. To determine the patient population likely to respond to VRX496 for optimal efficacy, we examined the ability of our research vector, VRX494, to modify and suppress HIV in vitro in lymphocytes isolated from 20 study subjects discordant for CD4 count and viral load. VRX494 is analogous to the clinical vector VRX496, except that it contains GFP as a marker gene instead of the 186-tag marker in the clinical vector. To transfer VRX494 to target cells we developed a novel scalable two-step transduction procedure that has been translated to the clinic in an ongoing clinical trial. This procedure achieved unprecedented transduction efficiencies of 94 +/- 5% in HIV(+) study subject cells. In addition the vector inhibited HIV replication >/=93% in culture regardless of the viral load or CD4 count of the subject or tropism of the virus strain with which they were infected. These findings demonstrate that VRX496T therapy is expected to be beneficial to patients that differ in their status in term of CD4 count and viral load. The methods described represent significant technical advances facilitating execution of lentivirus vector-mediated gene therapy for treatment of HIV and are currently being employed in the first trial evaluating lentivirus vector safety in humans.

CD4+ T cells from CD4C/HIVNef transgenic mice show enhanced activation in vivo with impaired proliferation in vitro but are dispensable for the development of a severe AIDS-like organ disease

The cellular and molecular mechanisms of dysfunction and depletion of CD4+ T lymphocytes over the course of human immunodeficiency virus type 1 (HIV-1) infection are still incompletely understood, but chronic immune activation is thought to play an important role in disease progression. We studied CD4+ T-cell biology in CD4C/HIV transgenic (Tg) mice, in which Nef expression is sufficient to induce a severe AIDS-like disease including a preferential decrease of CD4+ T cells. We show here that Nef-expressing Tg CD4+ T cells exhibit an activated/memory-like phenotype which appears to be independent of antigenic stimulation, as documented in experiments involving breeding with AD10 TcR Tg mice. In addition, in vivo bromodeoxyuridine incorporation showed that a larger proportion of Tg than non-Tg CD4+ T cells entered the S phase. However, in vitro, Tg CD4+ T cells were found to have a very limited capacity to divide in response to stimulation with anti-CD3 and anti-CD28 or in allogeneic mixed leukocyte reactions. Interestingly, despite these observations, the deletion of Tg CD4+ T cells had little impact on the development of other AIDS-like organ phenotypes. Thus, the Nef-induced chronic activation of CD4+ T cells may exhaust the T-cell pool and may contribute to the thymic atrophy and the low number of CD4+ T cells observed in these Tg mice.

Lymphocyte Numbers and Function in Relation to Periodontitis and Smoking

BACKGROUND

T and B lymphocytes play important roles in periodontitis. Smoking is considered a risk factor for periodontitis and may exert its negative effects through leukocytes. Taking smoking into consideration, the aim of this study was to analyze numbers of circulating T (CD3+) cells and their CD4+ and CD8+ subpopulations, B (CD19+) cells, and T-cell proliferative capacity in periodontitis.

METHODS

Lymphocyte immunophenotyping for T cells, their CD4+ and CD8+ subsets, and B cells was performed on peripheral blood from 76 periodontitis patients and 36 controls. Proliferative capacity of T cells was determined in whole-blood lymphocyte culture assays after mitogenic stimulation.

RESULTS

Total T cells, CD4+ and CD8+ subpopulations, and responsiveness to specific T-cell stimuli did not differ between patients and controls; in addition, B cells were not significantly elevated in periodontitis patients. However, more periodontal breakdown in smoking patients was associated with higher numbers of CD3+ T cells, as well as with CD4+ and CD8+ T-cell subsets, and increased T-cell proliferation. Numbers of B cells were not affected by smoking.

CONCLUSIONS

The increased numbers of T-cells and elevated T-cell responsiveness in patients who smoke may be one of several explanations why smoking is a risk factor for periodontitis. The mechanism of how T-cell function contributes to increase the severity of periodontal breakdown in smoking periodontitis patients needs to be investigated further.

T cell costimulatory molecule function determines susceptibility to infection with Pneumocystis carinii in mice

Loss of T cell number and function during HIV infection or secondary to pharmacologic immunosuppression renders individuals susceptible to opportunistic infections, including Pneumocystis carinii pneumonia. Because costimulatory receptors are critical for optimal T cell function, we hypothesized that these proteins would regulate susceptibility to opportunistic infections. We found that despite normal T cell numbers, mice deficient in the costimulatory molecules CD2 and CD28 spontaneously developed P. carinii pneumonia. In experiments using intratracheal injection of P. carinii organisms to induce infection, the loss of CD28 alone was sufficient to render mice susceptible to acute infection; however, the organism was eventually cleared. Examination of inflammatory responses to P. carinii revealed that mice deficient in both CD2 and CD28 accumulated CD8(+) T cells in their lungs in response to infection and demonstrated markedly reduced specific Ab titers. Analysis of cytokine profiles suggested that regulation of IL-10 and IL-15 may be important elements of the response to this pathogen. Thus, costimulatory molecule function is critical in determining the initial susceptibility to infection with P. carinii. Analysis of immunologic responses in these mice may provide important insights into the defects that render individuals susceptible to opportunistic infection, and provide opportunities for novel immunologically based therapies.

Preserved immune system in long-term asymptomatic vertically HIV-1 infected children

The objective of this study was to study immune system status in long-term asymptomatic (LTA) HIV-1-infected children. A cross-sectional study was used, involving HIV-1-infected children over 7 years of age who were rated into two groups according to their clinical and immunological classification: (a) LTA: 7 asymptomatic HIV-1-infected children in A1; (b) Rapid progressor (RP): 14 age-matched C3 HIV-1-infected children. The control group consisted of 17 age-matched uninfected children. The characterization of CD4+ T-cell subsets was determined by three-colour flow cytometry. The proliferative response and cytokine production by activated peripheral blood T-cells were also measured. IL-7 levels were measured in serum. Thymic production of T-cells was quantified by TCR rearrangement excision circles (TRECs). The LTA children showed similar proliferative responses to PHA, PWM and anti-CD3+ anti-CD28, but lower responses to tetanus toxoid and streptokinase, in comparison with the controls but always higher responses in comparison with the RP group. The production of TNF-alpha and IFN-gamma was similar in the LTA and control groups, and both were higher than the levels in the RP group. The LTA group showed a lower percentage of memory CD4+ T-cells (CD4+ CD45RO+, CD4+ CD45RA-CD62L+) than the control and RP groups. The LTA group also showed lower percentages of CD4+ CD7- cells than the controls. As for naïve CD4+ T-cells (CD4+ CD45RA+ CD62L+), CD4+ CD45RA+ and CD4+ CD62L+ cells, the LTA group showed higher values than the control and RP groups. The LTA group showed higher percentages of CD4+ HLA-DR+ CD38+ than the controls, but lower values than the RP group. In contrast, the LTA group had percentages of CD4+ HLA-DR-CD38+ T-cells higher than both the control and RP groups, whereas CD4+ CD38+ levels were only higher in the LTA group in comparison with the controls. CD4+ HLA-DR+ CD38- and CD4+ HLA-DR+ cell numbers were lower in the LTA group in comparison with the RP group. We found almost normal values of TRECs and IL-7 in the LTA group, but lower values in the RP group. Moreover, we found an inverse relation between TREC levels and IL-7 in plasma from HIV-infected children. Asymptomatic HIV-1 infected children have a well preserved immune system similar to that of control uninfected children in spite of HIV-infection for more than 7 years. Moreover, our results identified new markers of HIV disease, such as TRECs and IL-7, that could be used to monitor disease.

Characterizing immune reconstitution after long-term highly active antiretroviral therapy in pediatric AIDS

In this study, we sought to characterize the T lymphocyte recovery in vertically HIV-1-infected children who respond to long-term highly active antiretroviral therapy (HAART). A 3-year longitudinal retrospective study was used to perform a cross-sectional study of 32 children rated according to the time course of CD4(+) T cell percentages in response to antiretroviral therapy and CDC clinical classification: (1) long-term asymptomatic (LTA group): 8 children in A1 during the whole follow-up period; (2) responsive to HAART (Rec group): 13 children in C3 before HAART who achieved CD4(+) T cell counts of > 500 cells/mm(3) after 3 years of HAART; and (3) nonresponsive to HAART (Non-Rec group): 11 children in C3 during the whole follow-up period despite 3 years of HAART. We also studied 17 healthy age-matched uninfected children as controls. Lymphoproliferative responses (LPRs) were evaluated by incorporation of [(3)H]thymidine, identification of T cell subsets by three-color flow cytometry, and determination of thymic production of T cells by quantification of T cell receptor rearrangement excision circles (TRECs). Interestingly, the Rec group showed an increase in percentage of CD4(+) T cells and a decrease in viral load, and recovered LPRs to mitogens and recall antigens, with values similar to those of the LTA group. Moreover, the Rec group produced similar percentages and absolute counts of naive (CD45RA(+)CD62L(+)) CD4(+) and CD8(+) T cells, and TRECs similar to those of the LTA group. In particular, the Rec group produced similar percentages of CD8(+)CD28(-)CD57(+) and CD8(+)CD28(-)CD57(-) T cell subsets compared with controls. Our data indicate that among children who have already progressed to AIDS and severe immunodeficiency but who respond to HAART, the immune system can recover and resemble those of nonprogressors or even uninfected children, in quantitative as well as in functional terms.

Baseline T cell reactivity in multiple sclerosis is correlated to efficacy of interferon-beta

BACKGROUND

Measuring proliferative responses of T lymphocytes is a simple, reproducible and widely used assay of immune competence. Evidence suggests a role of T cell reactivity in autoimmune diseases. Interferon (IFN)-beta blocks in vitro proliferation of human T cells.

OBJECTIVES

To assess (i) the relation between T cell proliferation and disease characteristics of MS patients, (ii) differences in T cell proliferation between subgroups and HC, and (iii) the predictive value of T cell proliferation for efficacy of IFN-beta.

METHODS

Proliferative responses were measured in phytohaemagglutinin (PHA), anti-CD2/CD28 and anti-CD3 stimulated whole blood of 189 MS patients and 249 healthy controls (HC). Forty-eight patients started treatment with IFN-beta. Based on EDSS progression, number of relapses and steroid interventions, patients were classified as either clinical responder or nonresponder to IFN-beta.

RESULTS

Significant differences between MS subgroups and HC were found in T cell responses upon both PHA stimulation (RR>HC: p=0.001 and SP>HC: p=0.001) and CD2/CD28 stimulation (RR>HC, SP>HC and PP>HC: all p values <0.001). No significant differences were found between the MS subgroups. A probability of 88% (95% CI, 71-95%) for a favorable response to IFN-beta was found with increased baseline proliferative T cell responses to PHA; a probability of only 16% (95% CI, 7-33%) with decreased values.

CONCLUSION

Our results suggest that the level of T cell proliferation in whole blood predicts efficacy of IFN-beta in MS.

Effective antiretroviral therapy reduces degradation of tryptophan in patients with HIV-1 infection

Antiretroviral therapy (ART) has a significant impact on HIV-1 RNA levels, the CD4 cell count, and immune activation. We examined whether these changes are associated with a change in the rate of tryptophan degradation (expressed as the kynurenine to tryptophan ratio, kyn/trp) as an estimate for the activity of interferon-gamma inducible enzyme indoleamine (, )-dioxygenase (IDO). Plasma levels of tryptophan, kynurenine, and neopterin were measured pretherapy and 6 months postinitiation of therapy in 45 patients with HIV-1 RNA levels of less than 1000 copies/ml 6 months after initiation of ART. Before ART, the patients had decreased tryptophan and increased kynurenine concentrations compared to healthy controls. During ART, average tryptophan levels increased; in the same time kynurenine and kyn/trp decreased (P < 0.001), although not to normal levels. Since pretherapy tryptophan concentrations correlated inversely with neopterin, and kynurenine correlated with viral load and neopterin but not with CD4 cell count, the data support the view that HIV production may induce immune activation and consequently tryptophan is degraded at a higher rate. In agreement, kyn/trp positively correlated with neopterin (r(s) = 0.60, P < 0.001), with virus load (r(s) = 0.37, P = 0.013), and very weakly with CD4(+) cells counts (r(s) = 0.30, P = 0.049). The change in the kyn/trp ratio during ART correlated more strongly with the change in neopterin levels (r(s) = 0.49, P = 0.001) than with the change in HIV RNA levels and weakly with the CD4 cell count. The data underscore the fact that both neopterin production and tryptophan degradation are triggered by immune activation. Tryptophan degradation is increased in HIV infection and partially reversed under ART. The data agree with the concept that immune activation is the common background of IDO activation which may be an important factor underlying T-cell hyporesponsiveness.

[Different immune profiles according to the immunological and clinical progression in vertically HIV-infected children]

BACKGROUND

Our goal was to evaluate immunologic profile differences of HIV-infected children on antiretroviral treatment (ART). PATIENTS AND METHODDS: We studied 23 HIV-vertically infected children: a) N-A1 group: 10 HIV-infected children in A1 category; b) N-B2 group: 6 HIV-infected children in B2 category, and c) N-C3 group: 7 HIV-infected children in C3 category. We also studied 13 healthy age-matched HIV-negative children as controls. Cell proliferation was evaluated by incorporation of [3H]-Thymidine. The cytokine production in culture was quantified using commercially available specific ELISA assays. T-cell subsets were determined by flow cytometry.

RESULTS

Stimulation indexes of PHA, PWM, and anti-CD3+ anti-CD28 in N-A1 group were higher than in N-C3 group. In unstimulated PBMC, TNF-alpha production of HIV-infected children was higher than the control group (p < 0.05). However, in stimulated PBMC, TNF-alpha production in N-B2 and N-C3 groups was lower than the control group (p < 0.05). In HIV-infected children, CD8+ CD45RA+ CD62L+ T-cells were significantly lower (p < 0.01) and CD8+ CD45RO+ T-cells were higher (p < 0.05) than the control group. Moreover, in NA-1 group, CD4+ CD45RA+ CD62L+ T-cells were higher, and CD4+ CD45RO+ and CD8+ CD45RO+ T-cells were lower, than in N-B2 and N-C3 groups (p < 0.05). On the other hand, CD45RO+, CD45RO+ CD38+, HLA-DR+, CD38+ HLA-DR+ and CD38+ CD4+ and CD8+ T-cells were higher in N-C3 group than the N-A1 and control groups, except for CD4+ CD38+ T-cells. Activated CD8+ T-cells in N-A1 group were higher than in control group (p < 0.01).

CONCLUSION

Our data demonstrate that in spite of ART, there still remain important differences in the immunologic status of HIV-infected children depending on the HIV-infection stage.

The CD28/HLA-DR expressions on CD4+T but not CD8+T cells are significant predictors for progression to AIDS

To investigate the changes of CD28 and HLA-DR molecules on CD4+ and CD8+ T cells during HIV infection, we classified 130 HIV-infected Koreans into four groups by the CD4 level as follows: group I (> or = 500 cells/mm3), group II (201-499 cells/mm3), group III (51-200 cells/mm3), and group IV (< or = 50 cells/mm3). In CD4+ T cells, the proportion of CD28 expression decreased significantly with the CD4 level while the proportion of HLA-DR expression increased gradually. In particular, the changes of HLA-DR expressions on CD4+ T cells were parallel to the loss of CD28 molecules from stage III to IV. However, the CD28 expression on CD8+ T cells decreased dramatically in the early stage of HIV infection, and the sum and pattern of CD28 and HLA-DR expressions on CD8+ T cells was stable after the first stage. Even though CD28 down-regulation on CD8+ T cells was very severe from the early stage of HIV infection, it might not influence the survival time of HIV-infected Koreans. The sum of the CD28+ subsets and HLA-DR subsets in each T cell was stable in all stages of disease progression. The sums of the CD28+ subsets and HLA-DR+ subsets in CD4+ T and CD8+ T cells were constant as approximately 100% and 55-60% of each T cell. These results suggested that the changes of CD28/HLA-DR expressions on CD4+ T cells were more predictable than those on CD8+ T cells in the evaluation of the disease progression during HIV-infected periods. However, we need further studies to understand why the sum of two molecules in each T cell are constant.

Therapeutic immune reconstitution in HIV-1-infected children is independent of their age and pretreatment immune status

OBJECTIVE

To evaluate long-term immune reconstitution of children treated with highly active antiretroviral therapy (HAART).

METHODS

The long-term immunological response to HAART was studied in 71 HIV-1-infected children (aged 1 month to 18 years) in two prospective, open, uncontrolled national multicentre studies. Blood samples were taken before and after HAART was initiated, with a follow-up of 96 weeks, and peripheral CD4 and CD8 T cells plus naive and memory subsets were identified in whole blood samples. Relative cell counts were calculated in relation to the median of the age-specific reference.

RESULTS

The absolute CD4 cell count and percentage and the CD4 cell count as a percentage of normal increased significantly (P < 0.001) to medians of 939 x 106 cells/l (range, 10-3520), 32% (range, 1-50) and 84% (range, 1-161), respectively, after 48 weeks. This increase was predominantly owing to naive CD4 T cells. There was a correlation between the increase of absolute naive CD4 T cell counts and age. However, when CD4 T cell restoration was studied as percentage of normal values, the inverse correlation between the increase of naive CD4 T cell count and age was not observed. In addition, no difference in immunological reconstitution was observed at any time point between virological responders and non-responders.

CONCLUSIONS

Normalization of the CD4 cell counts in children treated with HAART is independent of age, indicating that children of all age groups can meet their CD4 T cell production demands. In general, it appears that children restore their CD4 T cell counts better and more rapidly than adults, even in a late stage of HIV-1 infection.

Exogenous interleukin-2 administration corrects the cell cycle perturbation of lymphocytes from human immunodeficiency virus-infected individuals

Human immunodeficiency virus (HIV)-induced immunodeficiency is characterized by progressive loss of CD4(+) T cells associated with functional abnormalities of the surviving lymphocytes. Increased susceptibility to apoptosis and loss of proper cell cycle control can be observed in lymphocytes from HIV-infected individuals and may contribute to the lymphocyte dysfunction of AIDS patients. To better understand the relation between T-cell activation, apoptosis, and cell cycle perturbation, we studied the effect of exogenous interleukin-2 (IL-2) administration on the intracellular turnover of phase-dependent proteins. Circulating T cells from HIV-infected patients display a marked discrepancy between a metabolic profile typical of G(0) and a pattern of expression of phase-dependent proteins that indicates a more-advanced position within the cell cycle. This discrepancy is enhanced by in vitro activation with ConA and ultimately results in a marked increase of apoptotic events. Conversely, treatment of lymphocytes with IL-2 alone restores the phase-specific pattern of expression of cell cycle-dependent proteins and is associated with low levels of apoptosis. Interestingly, exogenous IL-2 administration normalizes the overall intracellular protein turnover, as measured by protein synthesis, half-life of newly synthesised proteins, and total protein ubiquitination, thus providing a possible explanation for the effect of IL-2 on the intracellular kinetics of cell cycle-dependent proteins. The beneficial effect of IL-2 administration is consistent with the possibility of defective IL-2 function in vivo, which is confirmed by the observation that lymphocytes from HIV-infected patients show abnormal endogenous IL-2 paracrine/autocrine function upon in vitro mitogen stimulation. Overall these results confirm that perturbation of cell cycle control contributes to HIV-related lymphocyte dysfunction and, by showing that IL-2 administration can revert this perturbation, suggest a new mechanism of action of IL-2 therapy in HIV-infected patients.

Comparison of CD8(+) T-cell subsets in HIV-infected rapid progressor children versus non--rapid progressor children

BACKGROUND

CD8(+) T-cell subsets have not been adequately described in HIV-infected (HIV(+)) children classified with respect to disease progression as rapid-progressors (RPs) and non-rapid progressors (non-RPs).

OBJECTIVE

The purpose of this investigation was to determine the distribution of CD8(+) T-cell subsets in HIV(+) children and correlate the findings with degree of immunosuppression and HIV viral burden.

METHODS

By means of 3-color flow cytometry, percentages of CD38(+)DR(+), CD28(+), and CD57(+) CD8(+) T-cell subsets were examined in RP (n = 15) and non-RP (n = 36) HIV(+) children and in HIV-exposed but uninfected (n = 11) and HIVunexposed (n = 8) children. The CD8(+) T-cell subsets were correlated with mean CD4(+) T-cell percentages and HIV RNA levels. Analysis of covariance was used for group comparisons for the control of the covariate of age.

RESULTS

The HIV-exposed and HIV-unexposed controls were not different from each other in CD8(+) T-cell subset percentages, except that the DR(-)CD38(+)CD8(+) T-cell percentages were higher in the exposed controls than in the unexposed controls. RPs had a higher mean percentage of DR(+)CD38(+)CD8(+) T cells than non-RPs and both control groups, and RPs had higher viremia than non-RPs. CD38(+)CD8(+) T-cell percentages did not correlate with viral burden as it has been seen to do in HIV(+) adults. Percentages of CD28(+)CD8(+) T cells were lower in HIV-infected children than in controls. There was a positive correlation of percentage of CD28(+)CD57(-)CD8(+) T cells with CD4(+) T-cell percentages in each HIV-infected group.

CONCLUSION

CD8(+) T cells become activated (dual expression of DR and CD38) and lose CD28, some acquiring CD57, in relation to rapidity of disease progression in pediatric HIV infection.

Immunological benefits of antiretroviral therapy in very early stages of asymptomatic chronic HIV-1 infection

OBJECTIVES

To assess whether an almost complete restoration of immune system can be achieved when antiretroviral therapy is initiated at very early stages of asymptomatic chronic HIV-1 infection.

DESIGN

T cell subsets and cell-mediated responses were analysed at baseline and after 12 months of either a double or a triple antiretroviral therapy in 26 asymptomatic HIV-1-infected patients with CD4 T cell counts > 500 x 10(6) cells/l and a baseline plasma viral load > 10000 copies/ml.

RESULTS

Triple therapy was significantly more effective in reducing plasma HIV RNA to undetectable levels, in returning CD4:CD8 ratio to nearly normal levels, in reducing activated cells (CD38) and in increasing naive (CD45RA+CD45RO-) and memory (CD45RA-CD45RO+) CD4 cells. Both double and triple therapies caused a clear decrease in memory (CD45RA-CD45RO+) CD8 cells as well as a significant increase in the CD28 subset of CD8 cells. At baseline, there was an important increase in cells producing interferon-gamma (IFNgamma) with no significant abnormalities in T lymphocytes producing interleukin 2 (IL-2), tumour necrosis factor alpha and interleukin 4. Both types of therapy reduced IFNgamma- and IL2-producing CD4 T lymphocytes while IFNgamma-producing CD8 cells remained increased. Even before therapy, these HIV-1-positive patients lacked significant abnormalities in the T cell responsiveness to polyclonal stimuli as well as in the secretion of CCR5 chemokines by peripheral blood mononuclear cells.

CONCLUSIONS

Initiating highly active antiretroviral therapy at very early stages of chronic HIV-1 infection allows rapid and almost complete normalization of T cell subsets and preservation of T cell functions. These early-treated patients could be excellent candidates for receiving additional HIV-specific immune-based therapies, which might be essential for the control of HIV infection.

Spontaneous and anti-Fas-induced apoptosis in lymphocytes from HIV-infected patients undergoing highly active anti-retroviral therapy

OBJECTIVE

The aim of this study was to investigate susceptibility to spontaneous or anti-Fas-induced apoptosis in peripheral blood mononuclear cells (PBMC) from HIV-positive patients before and during highly active anti-retroviral therapy (HAART).

DESIGN

A longitudinal study was performed on 12 evaluable patients on HAART. This cohort was analysed prior to and at week 2, 4, 8, 16 and 24 after beginning HAART. Variations in CD4 and CD8 cells, viral load, susceptibility to spontaneous or anti-Fas-induced apoptosis in the presence of IL-2, IL-4 or IL-12 were studied. Expression of Fas and Bcl-2 were also assessed.

METHODS

Levels of HIV RNA were determined by a quantitative reverse transcription-PCR assay. Apoptosis was evaluated by staining isolated nuclei with propidium iodide followed by multiparameter flow cytometry analysis.

RESULTS

Spontaneous apoptosis of PBMC was promptly inhibited after the start of treatment. Similarly, anti-Fas-induced apoptosis diminished greatly during treatment. Expression of Fas decreased significantly, while that of Bcl-2 remained statistically unchanged during the first 24 weeks of therapy. Levels of apoptosis correlated inversely to CD4 cell counts and directly to viral load in a highly significant way. Expression of Fas was directly correlated to apoptosis. Interleukin (IL)-2, but not IL-4 or IL-12, protected PBMC of HIV-positive individuals from spontaneous or anti-Fas-induced apoptosis before and during HAART.

CONCLUSION

These results suggest that regulation of apoptosis and of Fas expression are involved in immunoreconstitution during HAART.

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.

CD28 costimulation and CD28 expression in T lymphocyte subsets in HIV-1 infection with and without progression to AIDS

In a prospective study of 152 HIV-1 patients (with and without progression to AIDS) we examined CD28 MoAb costimulation and CD3 MoAb response using whole blood culture at baseline and up to either the time of AIDS diagnosis or the end of the observation period. CD28 antigen expression on both CD4+ and CD8+ T lymphocytes was also studied in both groups of patients. In patients who progressed to AIDS, CD28 MoAb costimulation was found to be decreased. Univariate time-dependent analysis showed that decreases in (i) absolute numbers of either CD4+, CD4+CD28+, CD8+CD28+ T cells, (ii) CD28 MoAb costimulation, and (iii) CD3 MoAb response, and an increase in CD8+CD28- %, are significant predictors for progression to AIDS. In addition, multivariate time-dependent analysis demonstrated that a decrease in CD28 MoAb costimulation (but not a decrease in CD3 MoAb response) was predictive for progression to AIDS, as were decreases in the percentage of CD4+ T cells and the absolute number of CD4+CD28+ T cells. Thus, CD28 MoAb costimulation can be considered a useful assay for monitoring HIV-1 infection. Furthermore, apart from the early increase in the percentage of CD8+CD28- T cells and an increase in the percentage of CD28- on CD8+ T cells in both groups of patients at baseline compared with normal controls, a negative correlation was found to exist between the percentages of CD4+ or CD4+CD28+ T cells and the percentage of CD8+CD28- T cells; this suggests that these cells are probably mutually regulated.

Stress and coping: the psychoneuroimmunology of HIV/AIDS

A considerable body of evidence, reviewed in this chapter, suggests that psychosocial factors play an important role in progression of HIV infection, its morbidity and mortality. Psychosocial influences relating to faster disease progression include life-event stress, sustained depression, denial/avoidance coping, concealment of gay identity (unless one is rejection-sensitive), and negative expectancies. Conversely, protective psychosocial factors include active coping, finding new meaning, and stress management. In studying long survivors of HIV/AIDS, our group has found protective effects on health of life involvement, collaborative relationship with doctor, emotional expression, depression (conversely), and perceived stress (conversely). Reviewed and discussed are psychoneuroimmunological pathways by which immune and neuroendocrine mechanisms might link psychosocial factors with health and long survival. Finally, biological factors are also a major determinant of disease progression and include genetics and age of the host, viral strain and virulence, medication and several immune response factors on which psychosocial influences could impact.

Immune restoration does not invariably occur following long-term HIV-1 suppression during antiretroviral therapy. INCAS Study Group

BACKGROUND

Current antiretroviral treatment can induce significant and sustained virological and immunological responses in HIV-1-infected persons over at least the short- to mid-term.

OBJECTIVES

In this study, long-term immune reconstitution was investigated during highly active antiretroviral therapy.

METHODS

Patients enrolled in the INCAS study in The Netherlands were treated for 102 weeks (range 52-144 weeks) with nevirapine (NVP) + zidovudine (ZDV) (n = 9), didanosine (ddl) + ZDV (n = 10), or NVP + ddl + ZDV (n = 10). Memory and naïve CD4+ and CD8+ T cells were measured using CD45RA and CD27 monoclonal antibodies (mAb), T-cell function was assayed by CD3 + CD28 mAb stimulation, and plasma HIV-1 RNA load was measured by ultra-direct assay (cut-off < 20 copies/ml).

RESULTS

Compared to both double combination regimens the triple combination regimen resulted in the most sustained increase in CD4+ T cells (change in CD4+, + 253 x 10(6) cells/l; standard error, 79 x 10(6) cells/l) and reduction of plasma HIV-1 RNA. In nine patients (31%) (ddl + ZDV, n = 2; NVP + ddl + ZDV, n = 7) plasma HIV-1 RNA levels remained below cut-off for at least 2 years. On average, these long-term virological responders demonstrated a significantly higher increase of naïve and memory CD4+ T cells (P = 0.01 and 0.02, respectively) as compared with patients with a virological failure, and showed improved T-cell function and normalization of the naïve; memory CD8+ T-cell ratio. However, individual virological success or failure did not predict the degree of immunological response. T-cell patterns were independent of baseline CD4+ T-cell count, T-cell function, HIV-1 RNA load or age. Low numbers of naïve CD4+ T cells at baseline resulted in modest long-term naïve T-cell recovery.

CONCLUSIONS

Patients with prolonged undetectable plasma HIV-1 RNA levels during antiretroviral therapy do not invariably show immune restoration. Naïve T-cell recovery in the setting of complete viral suppression is a gradual process, similar to that reported for immune recovery in adults after chemotherapy and bone marrow transplantation.