Perturbation of CD4+ and CD8+ T-cell repertoires during progression to AIDS and regulation of the CD4+ repertoire during antiviral therapy

Clonal evolution of CD8+ T-cell expansions in HIV-infected patients on long-term HAART

HIV-1 continually replicates in spite of long-term highly active anti-retroviral therapy (HAART) and therefore, it is conceivable that the low level, persistent viral activity could continue to stimulate the hosts immune system despite remaining below the detection limit of the current assays. In this study, we performed a longitudinal analysis of the CD8+ T-cell receptor Vbeta repertoire in HAART-treated and untreated HIV patients. HAART-mediated control of viremia, for up to 18 months, did not prevent similar perturbations within the CD8+ Vbeta repertoire in both study groups as defined by CDR3 spectratyping. Oligoclonal Vbeta expansions, with new dominant CDR3 lengths, were observed throughout the study period. Our findings are compatible with antigen-driven CD8+ immune responses to bursts of replication from a continuously changing viral reservoir, regardless of HAART-mediated suppression of HIV-1 viremia.

Comparative analysis of human cytomegalovirus-specific CD4(+) T-cell frequency and lymphoproliferative response in human immunodeficiency virus-positive patients

Evaluation of human cytomegalovirus (HCMV)-specific T-helper immunity could contribute in optimizing anti-HCMV therapy in human immunodeficiency virus (HIV)-infected patients. Testin the lymphoproliferative response (LPR) is the standard technique used to evaluate T-helper response, but its use in the routine diagnostic laboratory setting can be problematic. The most promising new alternative technique is the determination of HCMV-specific CD4(+) T-cell frequency by flow cytometry detection of intracellular cytokine production after short-term antigen-specific activation of peripheral blood mononuclear cells. HCMV-specific LPR and CD4(+) T-cell frequency were compared in a group of 78 blood samples from 65 HIV-infected patients. The results showed concordance in 80.7% of samples. In addition, comparative analysis of sequential blood samples from 13 HIV-infected patients showed that while in about half of patients the T-helper HCMV-specific immune response remained stable during highly active antiretroviral therapy (HAART), in the other half declining levels of the HCMV-specific CD4(+)-mediated immune response were determined by either one or both assays. In conclusion, our data suggest that the determination of HCMV-specific CD4(+) T-cell frequency can be considered a valuable alternative to the LPR test for the detection of HCMV-specific T-helper response in HIV-infected patients. It could facilitate wider screening of anti-HCMV T-helper activity in HIV-infected patients, with potential benefits for clinicians in deciding strategies of discontinuation or maintenance of anti-HCMV therapy.

Genetically modified immunocompetent cells in HIV infection

Even in the era of highly active antiretroviral therapy (HAART), gene therapy (GT) can remain a promising approach for suppressing HIV infection, especially if complemented with other forms of pharmacological and immunological intervention. A large number of vectors and targets have been studied. Here we discuss the potential of genetically treated, antigen-specific immunocompetent cells for adoptive autologous immunotherapy of HIV infection. Cellular therapies with gene-modified CD8 and CD4 lymphocytes are aimed at reconstituting the antigen-specific repertoires that may be deranged as a consequence of HIV infection. Even if complete eradication of HIV from the reservoirs cannot be achieved, reconstitution of cellular immunity specific for opportunistic pathogens and for HIV itself is a desirable option to control progression of HIV infection and AIDS pathogenesis better.

TCR usage in naive and committed alloreactive cells: implications for the understanding of TCR biases in transplantation

The direct pathway of allorecognition is involved in acute allograft rejection and is characterised by TCR-mediated recognition of the MHC framework; this is thought to occur in a peptide-dependent but not peptide-specific manner. In contrast, the indirect pathway is restricted to the recipient's own MHC molecules and prevails in chronic rejection. In this pathway, the peptide has a major influence on the TCR recognition and selects alloreactive T cells with altered TCR Vbeta usage. However, qualitative analysis of Vbeta usage alone might limit our understanding of alloreactivity. The advantages of a combined quantitative assessment of Vbeta mRNA usage are discussed.

Immune reconstitution in human immunodeficiency virus-infected children receiving highly active antiretroviral therapy: a cohort study

BACKGROUND

Highly active antiretroviral therapy (HAART) has brought about rapid declines in HIV-1 RNA concentrations and an increase in CD4+ counts in HIV-1-infected children. These changes are often accompanied by clinical improvement; however, the extent to which immune reconstitution occurs is not known.

DESIGN

We compared two cohorts (n = 35) of HIV-1-infected children to evaluate the effects of HAART on immune recovery. Cohort 1 (C1) included clinically well children receiving HAART with a CD4 >22% at study initiation. Before HAART all children had moderately to severely suppressed immune function by CDC criteria (CD4 <25%) or CDC Category B or C disease. Cohort 2 (C2) included children with no current or past evidence of immunosuppression based on CDC criteria (CD4 >25%) and no evidence of clinical disease. Children in C2 were receiving a non-HAART regimen.

METHODS

Immunophenotyping was performed to characterize CD4+ and CD8+ subsets with regard to maturation and activation. T cell rearrangement excision circles (TRECs) were measured to quantify recent thymic emigrants.

RESULTS

No difference was found in percent CD4+ or percent CD8+ T cells or maturation markers between C1 and C2. There was significantly less expression of activation markers in both CD4+ and CD8+ cells in C1. There was no difference in TREC production between C1 and C2.

CONCLUSION

Moderately to severely suppressed HIV-1-infected children receiving HAART are able to reconstitute their immune systems to a degree that is indistinguishable from that of stable, CDC Class A1 HIV-1-infected children with regard to CD4+ and CD8+ T cell subsets, expression of cellular maturation markers and TREC production.

Severe perturbations of the blood T cell repertoire in polymyositis, but not dermatomyositis patients

Polymyositis and dermatomyositis are diseases characterized by muscle weakness and muscle inflammatory infiltrates. Their pathogenesis remains unclear. A central role for endomysial autoaggressive CD8(+) T cells is suspected in polymyositis and for perivascular B cells in dermatomyositis. We compared the T cell repertoire of 10 polymyositis and 10 dermatomyositis patients by immunoscope, a method providing a global assessment of the T cell repertoire and a sensitive detection of clonal T cell expansions. Samples were analyzed qualitatively and quantitatively in the blood (unsorted cells and CD4(+) and CD8(+) cells) and in muscle infiltrates. Dramatic perturbations of the T cell repertoire were observed in the blood of polymyositis but not dermatomyositis patients (p < 0.0005), the latter being undistinguishable from controls. These perturbations were due to oligoclonal expansions of CD8(+) T cells and most blood clonal expansions were also found in muscle. These results indicate that the pathogenesis of polymyositis and dermatomyositis is different and reinforce the view that polymyositis but not dermatomyositis is an autoimmune CD8(+) T cell-mediated disease. Moreover, this method may be helpful for the differential diagnosis of polymyositis and dermatomyositis and for noninvasive follow-up of polymyositis patients.

Direct recognition of foreign MHC determinants by naive T cells mobilizes specific Vbeta families without skewing of the complementarity-determining region 3 length distribution

The capacity of T cells to interact with nonself-APC, also referred to as direct allorecognition, is an essential feature of the cellular response involved in graft rejection. However, there is no study on TCR repertoire biases associated with direct restricted T cell activation. In this paper, we have addressed the impact of direct recognition on the whole naive T cell repertoire, using a new approach that provides, for the first time, an integrated depiction of the quantitative and qualitative alterations in the TCR Vbeta transcriptome. This method can differentiate resting patterns from polyclonally activated ones, as evidenced by superantigen usage. According to this new readout, we show that direct recognition of nonself-MHC molecules triggers mRNA accumulation of several TCR Vbeta families, specific to the combination studied. Moreover, in marked contrast to the situation that prevails in indirect allorecognition, T cell activation through the direct presentation pathway was not associated with skewing of the complementarity determining region (CDR) 3 length distribution. Altogether, these data argue for the significance of TCR contacts with the MHC framework in direct allorecognition. In addition, the TCR diversity mobilized by this interaction and the massive TCRbeta mRNA accumulation observed after a few days of culture suggest that a significant proportion of naive T cells receive a signal leading to TCRbeta transcriptional activation even though only a few of them engage in mitosis.

Human immunodeficiency virus pathogenesis: insights from studies of lymphoid cells and tissues

Although plasma virus load is invaluable for monitoring human immunodeficiency virus (HIV) infection, key pathogenesis events and most viral replication take place in lymphoid tissues. Decreases in virus load associated with therapy occur in plasma and tissues, but persistent latent infection and ongoing viral replication are evident. Many unanswered questions remain regarding mechanisms of HIV-associated lymphocyte depletion, but partial CD4(+) cell reconstitution after therapy likely reflects retrafficking from inflamed tissues, increased thymic or peripheral production, and decreased destruction. Rapid establishment of latent infection and the follicular dendritic cell-associated viral pool within lymphoid tissues suggest that only early intervention could substantially alter the natural history of HIV. If therapy is started prior to seroconversion, some individuals retain potent HIV-specific cellular immune responsiveness that is suggestive of delayed progression. Although complete virus eradication appears out of reach at present, more attention is being directed toward the prospect of boosting HIV-specific immune responses to effect another type of "clinical cure": immune-mediated virus suppression in the absence of therapy.

T-cell re-population in HIV-infected children on highly active anti-retroviral therapy (HAART)

In this pilot study, we address the nature of the re-population of the T-cell compartment in HIV-1+ (Human Immunodeficiency Virus 1), vertically infected children placed on successful regimens of HAART (highly active anti-retroviral therapy) incorporating 2 NRTI and a protease inhibitor. The clonality of the T-cell compartment and the abundance of RTEs (Recent Thymic Emigrants) were determined 2 weeks before and 20 weeks after initiation of HAART in a subgroup of children taking part in the PENTA (Paediatric European Network for the Treatment of AIDS) 5 trial. Analysis of the clonality of the circulating T-cell compartment was assessed using CDR3 spectratyping and analysed using the Kolmogorov-Smirnov two sample test. This revealed that a high degree of T-cell clonal restriction still exists 5 months into therapy, despite the appearance of previously undetectable T-cell clones within the periphery. We detected no increase in RTE abundance in this 5 month period, as determined by PCR detection of TRECs (T-Cell Receptor Excision Circles). We conclude that the observed re-population of T cells within the periphery of treated children is heavily reliant upon the maintenance/expansion of pre-existing cells during the 5 month period immediately following the initiation of therapy.

Antiapoptotic mechanism of HIV protease inhibitors: preventing mitochondrial transmembrane potential loss

Treatment of cells with the HIV drugs ritonavir, saquinavir, or nelfinavir (Nfv) inhibits apoptosis induced by a variety of stimuli. Because these drugs are protease inhibitors, they have been postulated to inhibit apoptosis by blocking caspase activity. This study shows that Nfv has no effect on caspase activity or on the transcription or synthesis of a variety of apoptosis regulatory molecules. Instead, Nfv inhibits mitochondrial transmembrane potential loss (Delta psi(m)) and the subsequent release of apoptotic mediators. Consequently, the antiapoptotic effects of Nfv are restricted to apoptotic pathways that involve Delta psi(m). (Blood. 2001;98:1078-1085)

Reconstitution of CD4+ T lymphocytes in HIV-infected individuals following antiretroviral therapy

Immune reconstitution during antiretroviral therapy has recently been shown to depend upon multiple factors at work in T cell homeostasis, amongst which the reduction of thymus dysfunction and of immune hyperactivation are instrumental. The optimism that has been raised by the restoration of hosts' defenses against opportunistic pathogens is, however, balanced by the poor immunity restored against HIV; thus, innovative immune interventions are required.

Selective increases in HIV-specific neutralizing antibody and partial reconstitution of cellular immune responses during prolonged, successful drug therapy of HIV infection

Because the immune response to HIV depends on viral gene expression, we examined the HIV-specific immune responses in persons whose viral load after highly active antiretroviral therapy (HAART) was <400 on at least 3 occasions over a 12-month interval. Eleven patients were identified. While there was little change in mean HIV-binding antibody (Ab) titers in this group, two persons mounted increases in HIV envelope-specific binding antibody. Neutralizing antibody (NAb) titers against a panel of HIV-1 primary isolates (BZ167, US1, and CM237) increased post-HAART (80% neutralization titer against US1, p = 0.06; against CM237, p = 0.04). The two persons with large increases in binding antibody also had increases in primary isolate NAb. Roughly half of HAART recipients had significant increases in neutralizing antibody to the primary isolates US1 and CM237. Compared with CD4-matched, non-HAART controls, there were significant increases in NAb against the subtype B primary isolate US1 (p < 0.0009); no increases were seen against more easily neutralized primary isolate BZ167. There were no differences after HAART in antibody-directed cellular cytotoxicity (ADCC). HAART resulted in a partial restoration of lymphoproliferative responses to recall antigens (tetanus and diphtheria). New responses developed to HIV Gag p24. No patient responded to HIV Env gp160 or gp120 either before or after HAART. The data underscore the lack of functional reconstitution of HIV-specific, CD4-mediated responses despite durable suppression of viral replication. In the setting of stable anti-HIV Ab levels, the development of increased NAb in certain individuals suggests that control of the virus by HAART may assist in immune control of HIV.

CMVR diagnoses and progression of CD4 cell counts and HIV viral load measurements in HIV patients on HAART

AIM

To assess the impact of highly active antiretroviral therapy (HAART) on the prevalence and progression of CMV retinitis (CMVR) among AIDS patients with baseline CD4 cell counts <100 cells x 10(6)/l.

METHODS

A longitudinal cohort study of 1292 patients. CD4 cell counts and HIV viral load measurements were obtained before commencing therapy, at 3 months, 1 year, 2 years, and at last follow up. The CMVR prevalence rate was measured for the subgroup with baseline CD4 cell counts <100 cells x 10(6)/l. CMVR adverse event (AE) rates per 100 person days at risk were calculated for the subgroup with CMVR and baseline CD4 cell counts <100 cells x 10(6)/l.

RESULTS

1292 patients were started on HAART. 8% of patients had CD4 counts <50 cells x 10(6)/l and 40% had detectable HIV viral load at last follow up. The prevalence of CMVR for the subgroup with baseline CD4 <100 cells x 10(6)/l was 10%. For those with baseline CD4 <100 cells x 10(6)/l, the mean CMVR AE rate was greatest during the first 6 months of follow up after HAART commencement (p <0.003). The mean AE rate per 100 person days at risk was 0.36 (95% CI 0.167 to 0.551) before starting HAART, and 0.14 (95% CI 0.085 to 0.199) after starting HAART (p = 0.03).

CONCLUSIONS

HAART significantly prolongs the disease-free intervals in patients with pre-existing disease but recurrences persist within the first 6 months of starting therapy. AE were absent beyond 18 months of follow up in all patients including those with persistently low CD4 counts and detectable HIV viral load indicating clinical immunorestoration. New methods for monitoring the response to therapy are needed to identify those at risk.

Improvement of HIV-specific immunity in HIV-infected twins treated with highly active antiretroviral therapy, interleukin 2, and syngeneic adoptively transferred cells

Five HIV-seropositive twins were treated with HAART and given cycles of treatment consisting of adoptive cellular therapy from their HIV-seronegative identical twins followed by a 5-day course of intravenous IL-2. Changes in absolute and percent CD4(+) and CD8(+) cell count were monitored and compared with changes in these parameters occurring in seven age-, sex-, and disease stage-matched HIV-infected patients treated with HAART alone. Increase in the magnitude and breadth of HIV-specific immune responses was monitored in three twin subjects who received multiple treatment cycles. Absolute and percent CD4(+) cell counts rose dramatically and to significantly higher levels in the recipient twins than in control subjects treated with HAART only. The subjects who received multiple cycles of treatment developed new and increased levels of HIV-specific activated and memory cytotoxic T lymphocyte responses, and interferon gamma-secreting effector cells. Treatment consisting of HAART, adoptive cellular therapy, and IL-2 was superior to treatment with HAART alone for improving absolute and percent CD4(+) cell counts and inducing new, or increasing the magnitude of, HIV-specific immune responses in HIV infected patients.

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

OBJECTIVE

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

DESIGN

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

T cell responses to highly active antiretroviral therapy defined by chemokine receptors expression, cytokine production, T cell receptor repertoire and anti-HIV T-lymphocyte activity

The immunological correlates of highly active antiretroviral therapy (HAART)-induced suppression of human immunodeficiency virus type 1 (HIV-1) replication have been investigated. 20 HIV-1-infected patients with mean CD4+ T cell count of 298/microl, plasma viral load of 4.7 log10 copies/ml and naive for protease inhibitors (PI) were studied during12 months of HAART. An increased number of both CD4+ and CD8+ naive T cells and a normalization of the frequency of CCR5- and CXCR4-expressing CD4+ T cells were readily observed after starting therapy. Single cell analysis of cytokine production after 12 months of HAART showed an increased number of interleukin (IL)-2-, but not IL-4- and (IFN)-gamma-, producing T cells and a decreased percentage of CD8+ IFN-gamma + cells. A correlation between the frequency of IFN-gamma-producing T cells and that of memory, CCR5+ and CD95+ T cells was demonstrated in both CD4+ and CD8+ subsets. The diversity of T cell receptor (TCR) variable beta (BV) chain repertoire significantly increased after 12 months of HAART within the CD4+ but not the CD8+ T cell subset. However, the level of perturbation of the third complementarity-determining region (CDR3), was not significantly modified by effective therapy. The number of anti-HIV Gag and Pol cytotoxic T lymphocytes precursors (CTLp) decreased during HAART and highly correlated with the CD8 IFN-gamma response. Ameliorated clinical conditions were observed in all patients in absence of any opportunistic infections during all the study period. These observations indicate that a better restoration of immunity may be obtained in patients starting HAART at less advanced stages of the disease.

Immune Reconstitution Strategies in HIV

Although potent antiretroviral therapy can dramatically decrease HIV replication and improve some aspects of host immunity, incomplete immune reconstitution persists even after several years of fully suppressive therapy. In addition, long-term toxicities of antiretroviral medications and the probability of developing multidrug-resistant virus with long-term use indicate that alternate means of controlling viral replication are needed for more durable suppression of HIV. Immune-based therapies may help potentiate the host's own defenses against HIV and other pathogens, and may ultimately result in more durable viral suppression and lower incidence of antiretroviral therapy-related side effects and toxicities.

Severe and long-lasting disruption of T-cell receptor diversity in human myeloma after high-dose chemotherapy and autologous peripheral blood progenitor cell infusion

Vaccine-based strategies are currently under investigation as a means of inducing tumour-specific immune responses and improving the clinical outcome of multiple myeloma (MM) patients in remission after high-dose chemotherapy and peripheral blood progenitor cell (PBPC) infusion. The immune competence of these patients was investigated by determining the overall diversity of the T-cell receptor (TCR) repertoire in the peripheral blood (PB) and bone marrow (BM). The average time after transplantation was 13 months. The clonality and reciprocal usage of BV gene segments (TCRBV repertoire) was estimated at the cDNA level and membrane protein expression. The TCRBV repertoire of MM was severely disrupted compared with age-matched normal donors. On average, one-third of the total repertoire in both the PB and the BM consisted of T cells expressing oligoclonal TCRbeta transcripts. Flow cytometry showed an increased frequency of abnormally expanded BV subfamilies at both sites. BV expansions were predominantly CD8+ and had the phenotype of antigen-experienced memory T cells as well as T cells with the naive phenotype. Oligoclonality was not restricted to phenotypically expanded BV subfamilies, but also involved normally represented BV subfamilies. The TCR repertoire of MM in remission was then compared with monoclonal gammopathy of undetermined significance (MGUS) and MM patients at diagnosis. The degree of TCR diversity was similar in age-matched normal donors and MGUS, but progressively decreased from MGUS to MM at diagnosis and then to MM in remission. These data indicate that: (1) there is a long-lasting and severe disruption of TCR diversity after high-dose chemotherapy and PBPC infusion, and (2) the extent of TCR disruption may affect the clinical outcome of vaccine-based strategies delivered at the stage of minimal residual disease.

Successful prophylaxis against Pneumocystis carinii pneumonia in HIV-infected children using smaller than recommended dosages of trimethoprim-sulfamethoxazole

Prophylaxis against Pneumocystis carinii pneumonia (PCP) is an essential part of the management of children with human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS). No dose-ranging studies were ever performed; therefore, the amount of trimethoprim-sulfamethoxazole (TMP-SMX) needed to suppress PCP in children with HIV/AIDS is not known. The dose recommended by the Centers for Disease Control (CDC) has been thought to be just above the threshold needed for prevention, based on anecdotal breakthrough PCP in cancer patients who were improperly dosed. We have been giving prophylaxis based on body weight rather than surface area, and this, combined with growth of our children, has led to a large experience with dosages lower than the currently recommended 150 mg/m2. The medical records of children with HIV who met CDC guidelines for institution of PCP prophylaxis were reviewed. To ascertain the per square meter (m2) dosage each child was receiving, body surface area was calculated from height and weight measurements. Dosages were recalculated every 6 months and at each dosage change. Data regarding PCP infection, bacterial infections, and side effects of TMP-SMX were extracted. Data were compiled from 1,719.5 child-months of TMP-SMX prophylaxis, including 1,532.5 child-months below the currently recommended dose. Sixty-seven percent of our child-months were at or below two-thirds the CDC recommended dose. There were no cases of proven or suspected PCP. Incidence of other serious bacterial infections was low. Bacteremia and sepsis with Streptococcus pneumoniae was the most common proven bacterial infection, at a rate of 5.5 episodes per 100 child-years. The incidence of bacterial infection did not vary by the dose of TMP-SMX. TMP-SMX prophylaxis was well tolerated; most reactions were mild and self-limited and did not recur with re-institution of the drug. Only 6.1% of this cohort had TMP-SMX prophylaxis discontinued due to perceived toxicity. These data show that the currently recommended dose of TMP-SMX (150 mg/m2) may not be required to prevent PCP in children with HIV/AIDS. The drug is well tolerated at all dosage levels. The incidence of serious bacterial infection in this cohort of patients did not depend upon the amount of TMP-SMX prescribed. A prospective, controlled clinical trial of low-dose TMP-SMX for children with HIV infection is warranted.

The dynamics of CD4+ T-cell depletion in HIV disease

The size and composition of the CD4+ T-cell population is regulated by balanced proliferation of progenitor cells and death of mature progeny. After infection with the human immunodeficiency virus, this homeostasis is often disturbed and CD4+ T cells are instead depleted. Such depletion cannot result simply from accelerated destruction of mature CD4+ T cells - sources of T-cell production must also fail. Ironically, this failure may be precipitated by physiological mechanisms designed to maintain homeostasis in the face of accelerated T-cell loss.

Response to highly active antiretroviral therapy according to duration of HIV infection

OBJECTIVE

To evaluate whether duration of HIV-1 infection influences the response to highly active antiretroviral therapy (HAART).

DESIGN

Prospective study of individuals (Italian Seroconversion Study cohort) with well-estimated dates of HIV-1 seroconversion.

METHODS

This analysis included 277 participants who began HAART (defined as three antiretroviral drugs used in combination). Cox regression models were used to evaluate the association between duration of infection (as categorical variable [</=3, 3-7.5, >7.5 years from seroconversion] or continuous variable) and an immunologic (rise in CD4 count >100 cells/mm3) and a virologic (decline in plasma HIV-RNA to unquantifiable levels) outcome. All analyses were stratified by center of recruitment and adjustment, when used, was for gender, age at inception of HAART, injection drug use, previous antiretroviral therapy, lag-time between positive and negative HIV test result, year of starting HAART, clinical stage, CD4 count, and HIV-RNA at time of HAART.

RESULTS

HAART was initiated a median of 6.4 years after seroconversion. There was a median follow-up of 1.6 years after starting HAART to the calendar cut-off (November 1999). One-hundred-eighty-one (65.3%) patients experienced a decline in viral load to below quantifiable levels and 184 (66.4%) experienced a rise in CD4 >100 cells/mm3. In the Cox models, by 1-year increase in duration of infection, we estimated a lower crude hazard of achieving a CD4 count increase >100 cells (relative hazard [RH], 0.96; 95% confidence interval [CI], 0.92-1.01; p =.09), and a lower hazard of reaching an unquantifiable level of plasma HIV-RNA (RH, 0.97; 95%CI, 0.93-1.02; p =.20). After adjustment, these values became 0.99 (95%CI, 0.93-1.04; p =.62) and 0.98 (95%CI, 0.93-1.04; p =.48), respectively. When duration of HIV infection was considered as a categorical variable, the results were consistent with those already described.

CONCLUSIONS

These results suggest that the duration of HIV infection does not seem to play an important independent role in determining the virologic and immunologic responses to HAART.

Timing of antiretroviral therapy. Use of Markov modeling and decision analysis to evaluate the long-term implications of therapy

BACKGROUND

The timing of initiation of antiretroviral therapy is controversial. Current guidelines are heavily based on the principle of 'hit early, hit hard', although the long-term implications of this approach are unknown.

METHODS

Using Markov modeling and decision analysis we modeled the virologic outcomes over 10 years in a hypothetical population of 10 000 HIV-infected patients in which therapy (with the possibility of three sequential regimens before the development of multidrug-resistant virus) is started immediately versus starting progressively at rates of 5, 10, 15, 20 or 30% of the original population each year. The model used inputs from available clinical trial data: virologic success rate and durability of the response of the first and subsequent regimens. We performed one-way and two-way sensitivity analysis to evaluate changes in the input variables.

RESULTS

If therapy is started immediately in all patients, by 10 years 57% would be undetectable, but 38% would have detectable multidrug-resistant virus. In contrast, the population as a whole would have had better virologic outcomes if one waited before starting treatment at any progression rate; for example, initiating therapy in 10% of the subjects per year results in 64% of patients being undetectable and 24% with multidrug-resistant virus. Two-way sensitivity analysis demonstrates that immediate initiation should be at least 15 to 20% better than delayed antiretroviral therapy to justify immediate initiation of therapy over a wide range of success rates of the delayed start.

CONCLUSION

Our analysis, utilizing optimistic outcomes based on short-term clinical trials, provides a theoretical basis for questioning the current aggressive early use of therapy and should help prompt studies that look at when and how to start antiretroviral therapy.

Down-regulation of CD8+ T-cell expansions in patients with human immunodeficiency virus infection receiving highly active combination therapy

Analysis of T-cell receptor (TCR) repertoire usage made by peripheral T lymphocytes during the chronic phase of HIV-1 infection has revealed the presence of clonal expansions of CD8 T cells that are also shown to be largely HIV-specific. Yet, it remains unclear whether the global repertoire perturbation observed during the chronic phase of the infection is also HIV-related and reversible in the long term with the application of highly active antiretroviral therapy. Furthermore, the diversity and the stability of repertoire usage after a relapse of viral replication were never examined. Eight patients were observed longitudinally up to 31 months under triple-association therapy. When viral replication was steadily suppressed, CD8 repertoires were significantly stabilized. Conversely, in situations of incomplete or only transient viral suppression, persistence or rebound in repertoire perturbation was observed. Finally, a T-cell response remarkably different from baseline, as reflected by a repertoire switch, was generated after the discontinuation of highly active therapy. In conclusion, a sustained control of HIV replication correlated with profound modifications of the CD8 repertoire usage. These data also suggested that autovaccination by the withdrawal of antiviral drugs would result in the selection and expansion of T-cell clones that were not necessarily dominant before the onset of treatment.

Recurrences of cytomegalovirus retinitis in a human immunodeficiency virus-infected patient, despite potent antiretroviral therapy and apparent immune reconstitution

We describe a 42-year-old man with human immunodeficiency virus infection who developed multiple recurrences of cytomegalovirus (CMV) retinitis despite receiving highly active antiretroviral therapy and having apparent immune reconstitution as evidenced by CD4(+) T lymphocyte counts of > 200 cells/mm(3). Laboratory investigation during one recurrence of retinitis confirmed that there was active CMV replication in the plasma and vitreous fluid. In addition, lymphoproliferative responses to CMV antigens were absent despite evidence of reactivity to Candida antigen and pokeweed mitogen. The clinical significance of this case and of other recently reported cases is discussed.

Psoriatic arthritis joint fluids are characterized by CD8 and CD4 T cell clonal expansions appear antigen driven

The CD8 alphabetaT cell receptor repertoire in joint fluid of individuals with active psoriatic arthritis contained an average of 32 major oligoclonal expansions in many variable genes of the TCR beta chain (BV) families, as shown by beta-chain CDR3 length analysis. Interestingly, a small number of oligoclonal expansions were shared between simultaneous samples of joint fluid and blood; however, most expansions found in joint fluid were not identifiable in blood emphasizing the immunologic specificity of the clonal events for the inflamed joint at a given point of time. The CD4 T cell joint fluid repertoire contained fewer and smaller oligoclonal expansions also largely restricted to the joint, suggesting that CD4 T cells participate perhaps by interacting cognitively to generate the CD8 clones. The inferred amino acid sequence of a single CD8 oligoclonal expansion revealed that they usually are composed of one or a few structurally related clones at the amino acid sequence level with beta-chains that encode identical or highly homologous CDR3 motifs. These were not shared among patients. Moreover, several clones that encoded the same amino acid sequence were found to be structurally distinct at the nucleotide level, strongly implying clonal selection and expansion is operating at the level of specific TCR-peptide interactions. The findings support a model of psoriatic arthritis inflammation involving extensive and selective Ag, likely autoantigen, driven intra-articular CD4, and CD8 T cell clonal expansions.

Modeling changes in CD4-positive T-lymphocyte counts after the start of highly active antiretroviral therapy and the relation with risk of opportunistic infections: the Aquitaine Cohort, 1996-1997

After initiation of a treatment for human immunodeficiency virus type 1 infection containing a protease inhibitor, immune restoration associated with increases in CD4-positive (CD4+) T lymphocyte count may be delayed. In a sample of patients who had been prescribed protease inhibitors for the first time, the authors tested to see whether there was a minimal duration of CD4+ cell count increase before the increase had an impact on the occurrence of opportunistic infections. The evolution (difference between time t and baseline) of CD4+ cell count was modeled using a mixed effects linear model. Changes in CD4+ count estimated by this model were then included as time-dependent covariates in a proportional hazards model. Finally, the authors tested for the existence of a CD4+ change x time interaction. The authors used a sample of 553 French patients first prescribed protease inhibitors in 1996 and followed for a median of 16 months. During the first 120 days, there was no association between CD4+ change and the rate of opportunistic infections. After 120 days, each 50-cell/mm3 increase in CD4+ count was associated with a 60% (95% confidence interval: 45, 72) reduction in the incidence of opportunistic infections. These results, based on modeling of CD4+ cell response, at least indirectly reinforce the concept of a delayed but possible immune recovery with the use of protease inhibitors. The findings support the potential for interruption of certain types of prophylaxis against opportunistic infections under reasonable conditions of duration of antiretroviral therapy and sustained CD4+ cell response.

Structured treatment interruptions to control HIV-1 and limit drug exposure

Although therapy-mediated suppression of HIV-1 is effective and results in a degree of immune reconstitution, the complications resulting from life-long treatment emphasize the need for alternatives. This review discusses the use of structured interruptions in antiviral therapy to induce drug-free periods of immune-mediated control of HIV-1. Such an approach has the ultimate objective of harnessing anti-viral immune responses, reducing drug exposure (toxicity and cost) and potentially extending the clinical benefits of a suppressive treatment regimen.

A randomized trial of the discontinuation of primary and secondary prophylaxis against Pneumocystis carinii pneumonia after highly active antiretroviral therapy in patients with HIV infection. Grupo de Estudio del SIDA 04/98

BACKGROUND

Prophylaxis against Pneumocystis carinii pneumonia is indicated in patients with human immunodeficiency virus (HIV) infection who have less than 200 CD4 cells per cubic millimeter and in those with a history of P. carinii pneumonia. However, it is not clear whether prophylaxis can be safely discontinued after CD4 cell counts increase in response to highly active antiretroviral therapy.

METHODS

We conducted a randomized trial of the discontinuation of primary or secondary prophylaxis against P. carinii pneumonia in HIV-infected patients with a sustained response to antiviral therapy, defined by a CD4 cell count of 200 or more per cubic millimeter and plasma HIV type 1 (HIV-1) RNA level of less than 5000 copies per milliliter for at least three months. Prophylactic treatment was restarted if the CD4 cell count declined to less than 200 per cubic millimeter.

RESULTS

The 474 patients receiving primary prophylaxis had a median CD4 cell count at entry of 342 per cubic millimeter, and 38 percent had detectable HIV-1 RNA. After a median follow-up period of 20 months (758 person-years), there had been no episodes of P. carinii pneumonia in the 240 patients who discontinued prophylaxis (95 percent confidence interval, 0 to 0.85 episode per 100 person-years). For the 113 patients receiving secondary prophylaxis, the median CD4 cell count at entry was 355 per cubic millimeter, and 24 percent had detectable HIV-1 RNA. After a median follow-up period of 12 months (123 person-years), there had been no episodes of P. carinii pneumonia in the 60 patients who discontinued prophylaxis (95 percent confidence interval, 0 to 4.5 episodes per 100 person-years).

CONCLUSIONS

In HIV-infected patients receiving highly active antiretroviral therapy, primary and secondary prophylaxis against P. carinii pneumonia can be safely discontinued after the CD4 cell count has increased to 200 or more per cubic millimeter for more than three months.

Longitudinal analysis of T-cell receptor gene use by CD8(+) T cells in early human immunodeficiency virus infection in patients receiving highly active antiretroviral therapy

The effects of early antiretroviral therapy on the peripheral CD8(+) T-cell population were assessed by sequentially determining the T-cell receptor (TCR) repertoire complexity in a cohort of 15 individuals recently diagnosed with human immunodeficiency virus infection. Analysis was based on quantitative TCR variable B gene (TCRBV) usage and complementary-determining region 3 length assessment. Repertories were assessed at baseline and at weeks 2, 4, 12, 24, and 72 after initiation of therapy. Early administration of highly active antiretroviral therapy has a positive effect on the preservation and homeostasis of the CD8(+) cell repertoire. Nevertheless, differences from average baseline and control TCR profiles and initial development of repertoire perturbations were observed. The findings suggest that additional therapeutic protocols will be required during primary infection to significantly prevent long-term erosion of the T-cell-mediated immune response.

Molecular correlates in AIDS patients following antiretroviral therapy: diversified T-cell receptor repertoires and in vivo control of cytomegalovirus replication

OBJECTIVES

To evaluate whether successful, long-term immune reconstitution in vivo can be achieved in end-stage AIDS patients following antiretroviral therapy (ART).

METHODS

A 1-year prospective study of changes of CD4+ and CD8+ T-cell surface phenotypes, T-cell receptor (TCR) repertoires and capacity to control in vivo replication of cytomegalovirus (CMV) was performed in five treatment-naive end-stage AIDS patients (median CD4+ T-cell counts of 19 cells/microL) following therapy. Proportions of CD45RA+, CD45RO+ and CD28+ cells within the CD4+ and CD8+ subsets, were determined by flow cytometry. Changes in TCR Vbeta repertoires within the CD4+ and CD8+ T-cell compartments were evaluated using CDR3 spectratyping. CMV replication was determined by a sensitive polymerase chain reaction (PCR) assay using whole blood.

RESULTS

Following ART, proportionate increases in 'naive' (CD45RA+) and 'memory' (CD45RO+) T cells were observed within both CD4+ and CD8+ T-cell subsets, while increased numbers of CD28+ T cells were mainly observed within the CD4+ subset. Diversification of CD4+ and CD8+ TCR repertoires was established concomitantly with renewed in vivo control of CMV replication.

CONCLUSIONS

An important degree of molecular and functional immune recovery is possible in end-stage AIDS patients introduced to therapy. Diversification of TCR repertoires and the in vivo restoration of immunocompetence to control opportunistic infections clearly show that an important degree of molecular immune reconstitution is established following the initiation of ART even in late-stage AIDS.

Immune-Based Therapies for the Management of HIV Infection: Highly Active Antiretroviral Therapy and Beyond

The widespread use of highly active antiretroviral therapy (HAART) has had a significant impact on reducing the incidence of opportunistic infections in patients with the Acquired Immunodeficiency Syndrome (AIDS) and reducing the overall morbidity and mortality associated with this disease. However, the use of HAART is often associated with adverse effects, significant drug interactions, high cost and the emergence of viral resistance in a significant percentage of treatment recipients. In addition, the clinical efficacy of HAART in terms of viral eradication appears to be limited due to the presence of reservoirs of latent virus within HAART-experienced patients. Because of these and other limitations associated with antiretroviral therapies, new therapeutic strategies are being developed to restore the normal function of the immune system and improve patient outcomes. The purpose of this article is to review some of the more promising investigational immune-based therapies and their potential role in the management of Human Immunodeficiency Virus infection.

Longitudinal changes in CD4+ T cell antigen receptor diversity and naive/memory cell phenotype during 9 to 26 months of antiretroviral therapy of HIV-infected patients

Although skewing of the CD4+ TCR repertoire in advanced HIV infection is well documented, increases in polyclonality during antiretroviral therapy have been less consistently observed. Ten patients, each with documented abnormalities within the CD4+ TCR repertoire, were studied by CDR3 spectratyping, semiquantitative PCR, and SSCP during 9-26 months of therapy. Naive and memory cell phenotypes were analyzed by flow cytometry. Six of 10 patients showed increased polyclonality of their TCR repertoires, 1 showed no change, and 3 showed increased TCR skewing, despite suppressed viral replication. Overall, there was no significant change in the percentage of abnormal BV subfamilies (from a mean of 25.5 to 17.1%) or the percentage of naive CD4+ T cells (from a mean of 18 to 25%). Further, progression of TCR repertoire disruptions was observed in some patients even with suppression of plasma viral RNA below 500 copies/ml. Although a spectrum of changes may be seen within the CD4+ TCR repertoire in the setting of antiretroviral therapy, increases in polyclonality are observed in some patients.

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

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

T-Cell receptor Vbeta repertoire CDR3 length diversity differs within CD45RA and CD45RO T-cell subsets in healthy and human immunodeficiency virus-infected children

The T-cell receptor (TCR) CDR3 length heterogeneity is formed during recombination of individual Vbeta gene families. We hypothesized that CDR3 length diversity could be used to assess the fundamental differences within the TCR repertoire of CD45RA and CD45RO T-cell subpopulations. By using PCR-based spectratyping, nested primers for all 24 human Vbeta families were developed to amplify CDR3 lengths in immunomagnetically selected CD45RA and CD45RO subsets within both CD4(+) and CD8(+) T-cell populations. Umbilical cord blood mononuclear cells or peripheral blood mononuclear cells obtained from healthy newborns, infants, and children, as well as human immunodeficiency virus (HIV)-infected children, were analyzed. All T-cell subsets from newborn and healthy children demonstrated a Gaussian distribution of CDR3 lengths in separated T-cell subsets. In contrast, HIV-infected children had a high proportion of predominant CDR3 lengths within both CD45RA and CD45RO T-cell subpopulations, most commonly in CD8(+) CD45RO T cells. Sharp differences in clonal dominance and size distributions were observed when cells were separated into CD45RA or CD45RO subpopulations. These differences were not apparent in unfractionated CD4(+) or CD8(+) T cells from HIV-infected subjects. Sequence analysis of predominant CDR3 lengths revealed oligoclonal expansion within individual Vbeta families. Analysis of the CDR3 length diversity within CD45RA and CD45RO T cells provides a more accurate measure of disturbances in the TCR repertoire than analysis of unfractionated CD4 and CD8 T cells.

Restoration of cellular immunity against tuberculosis in patients coinfected with HIV-1 and tuberculosis with effective antiretroviral therapy: assessment by determination of CD69 expression on T cells after tuberculin stimulation

Whether immunity against opportunistic pathogens can be fully restored by control of HIV-1 replication remains open to question. This longitudinal study was conducted to measure anti-tuberculosis (TB) cellular immunity in 13 HIV-1/TB-coinfected patients effectively treated by highly active antiretroviral therapy (HAART) in a period of 12 months. In this study, anti-TB cellular immunity was assessed by determining the frequencies of CD 69 expression on CD4+ and CD8+ T cells in response to purified protein derivative (PPD) stimulation (abbreviated as %CD4+CD69 to PPD and %CD8+CD69 to PPD). Here, we show that %CD4+CD69 to PPD correlated with the results of tuberculin skin tests and interferon-gamma (IFN-gamma) production from PPD-stimulated CD4+ T cells, and %CD8+CD69 to PPD also correlated with CD8+ T cell-mediated PPD-specific cytolysis. In overall analysis for these 13 patients, both %CD4+CD69 to PPD and %CD8+CD69 to PPD increased significantly during the 12 months (p =. 003 and p <.001, respectively). However, we found %CD4+CD69 to PPD or %CD8+CD69 to PPD failed to increase substantially in some patients (i.e., immunologic nonresponders). A significantly higher proportion of patients whose baseline CD4+ count was <50 cells/mm3 were considered to be CD4+ nonresponders compared with those whose baseline CD4+ count was >50 cells/mm3. Furthermore, baseline CD4+ cell count in nonresponders is significantly lower than that in responders, although the effectiveness of HAART did not differ between them. Our results indicate that PPD-specific frequencies of CD69 expression may be used as surrogate markers of anti-TB cellular immunity. By this method, we show that full reconstitution of anti-TB cellular immunity in HIV-1/TB coinfected patients may not necessarily be achieved by "successful" HAART and may be influenced by the baseline immune status when HAART is started. These data suggest that the decision to discontinue secondary prophylaxis for opportunistic infections should be cautiously made, even when the CD4+ cell count has significantly increased.

Patterns of CD8 T cell clonal dominance in response to change in antiretroviral therapy in HIV-infected children

OBJECTIVE

To examine the influence of change in antiretroviral therapy (ART) on patterns of CD8 T cell clonal dominance in HIV-infected children.

DESIGN

Seventeen HIV-infected children with plasma virus loads between 3.1 and 5.7 log10 were investigated before and after changes in ART.

METHODS

CDR3 spectratyping was performed in 22 T cell receptor (TCR) Vbeta subfamilies by multiplex polymerase chain reaction (PCR) in purified peripheral blood CD8 T cells in conjunction with CD4 cell counts, plasma HIV-RNA copies and lymphoproliferative assays (LPA).

RESULTS

CD8 T cell clonal dominance in two or more Vbeta families was present in eight out of 17 children. After a change in therapy, 13 patients (76%) acquired new clones whereas three patients (17.6%) showed a loss in CD8 cell clones. An increase in the numbers of dominant clones correlated with an increase in percentage CD4 cell counts (P < 0.001) and with improved LPA responses to tetanus (P < 0.05) and alloantigens (P < 0.01). CD4 cell increase was associated with an initial mean gain of 3.1+/-2.1 CD8 cell clones, independent of a virological response. A loss of CD8 cell clones or failure to achieve CD4 T cell increase was associated with failure to achieve virological suppression.

CONCLUSION

Children with chronic HIV infection manifest CD8 T cell clonal dominance, which appears to be dependent upon the adequacy of the CD4 cells. With optimization of therapy, a gain in clonal dominance is the predominant response, except in situations of failure to contain viral replication.

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.

Differential dynamics of CD4(+) and CD8(+) T-lymphocyte proliferation and activation in acute simian immunodeficiency virus infection

Although lymphocyte turnover in chronic human immunodeficiency virus and simian immunodeficiency virus (SIV) infection has been extensively studied, there is little information on turnover in acute infection. We carried out a prospective kinetic analysis of lymphocyte proliferation in 13 rhesus macaques inoculated with pathogenic SIV. A short-lived dramatic increase in circulating Ki-67(+) lymphocytes observed at 1 to 4 weeks was temporally related to the onset of SIV replication. A 5- to 10-fold increase in Ki-67(+) CD8(+) T lymphocytes and a 2- to 3-fold increase in Ki-67(+) CD3(-) CD8(+) natural killer cells accounted for >85% of proliferating lymphocytes at peak proliferation. In contrast, there was little change in the percentage of Ki-67(+) CD4(+) T lymphocytes during acute infection, although transient increases in Ki-67(-) and Ki-67(+) CD4(+) T lymphocytes expressing CD69, Fas, and HLA-DR were observed. A two- to fourfold decline in CD4(+) T lymphocytes expressing CD25 and CD69 was seen later in SIV infection. The majority of Ki-67(+) CD8(+) T lymphocytes were phenotypically CD45RA(-) CD49d(hi) Fas(hi) CD25(-) CD69(-) CD28(-) HLA-DR(-) and persisted at levels twofold above baseline 6 months after SIV infection. Increased CD8(+) T-lymphocyte proliferation was associated with cell expansion, paralleled the onset of SIV-specific cytotoxic T-lymphocyte activity, and had an oligoclonal component. Thus, divergent patterns of proliferation and activation are exhibited by CD4(+) and CD8(+) T lymphocytes in early SIV infection and may determine how these cells are differentially affected in AIDS.

Prolonged dominance of clonally restricted CD4(+) T cells in macaques infected with simian immunodeficiency viruses

The repertoire of functional CD4(+) T lymphocytes in human immunodeficiency virus type 1-infected individuals remains poorly understood. To explore this issue, we have examined the clonality of CD4(+) T cells in simian immunodeficiency virus (SIV)-infected macaques by assessing T-cell receptor complementarity-determining region 3 (CDR3) profiles and sequences. A dominance of CD4(+) T cells expressing particular CDR3 sequences was identified within certain Vbeta-expressing peripheral blood lymphocyte subpopulations in the infected monkeys. Studies were then done to explore whether these dominant CD4(+) T cells represented expanded antigen-specific cell subpopulations or residual cells remaining in the course of virus-induced CD4(+) T-cell depletion. Sequence analysis revealed that these selected CDR3-bearing CD4(+) T-cell clones emerged soon after infection and dominated the CD4(+) T-cell repertoire for up to 14 months. Moreover, inoculation of chronically infected macaques with autologous SIV-infected cell lines to transiently increase plasma viral loads in the monkeys resulted in the dominance of these selected CDR3-bearing CD4(+) T cells. Both the temporal association of the detection of these clonal cell populations with infection and the dominance of these cell populations following superinfection with SIV suggest that these cells may be SIV specific. Finally, the inoculation of staphylococcal enterotoxin B superantigen into SIV-infected macaques uncovered a polyclonal background underlying the few dominant CDR3-bearing CD4(+) T cells, demonstrating that expandable polyclonal CD4(+) T-cell subpopulations persist in these animals. These results support the notions that a chronic AIDS virus infection can induce clonal expansion, in addition to depletion of CD4(+) T cells, and that some of these clones may be SIV specific.

Progressive reduction of CMV-specific CD4+ T cells in HIV-1 infected individuals during antiretroviral therapy

Visualization of antigen-specific T cells has become an important tool in studying immune responses. The aim of this study was to analyze CMV-specific CD4+ T cells in healthy and HIV-infected individuals. Peripheral blood mononuclear cells (PBMC) were examined for antigen-induced intracellular cytokine responses. We found significant numbers of CMV-specific CD4+ T cells detectable in most CMV-IgG+ HIV-1 infected individuals, whereas CMV-specific CD4+ T cells could not be demonstrated in CMV-IgG- patients. Median frequency of CMV-specific CD4+ T cells were lower in HIV-infected subjects who had been treated with highly active antiretroviral therapy (HAART) for more than 1 year than in untreated HIV-infected individuals. In patients under therapy for less than 1 year median CMV-specific CD4+ T cell responder frequency was higher than in subjects treated for more than 1 year but lower than in untreated subjects. HIV suppression with HAART might lead to a progressive reduction of CMV-specific CD4+ T cells indicating an efficient elimination of an opportunistic pathogen.

Flow cytometric analysis of the Vbeta repertoire in healthy controls

BACKGROUND

Analysis of the T-cell receptor (TCR)-Vbeta repertoire has been used for studying selective T-cell responses in autoimmune disease, alloreactivity in transplantation, and protective immunity against microbial and tumor antigens. For the interpretation of these studies, we need information about the Vbeta repertoire usage in healthy individuals.

METHODS

We analyzed blood T-lymphocyte (sub)populations of 36 healthy controls (age range: from neonates to 86 years) with a carefully selected most complete panel of 22 Vbeta monoclonal antibodies, which together recognized 70-75% of all blood TCRalphabeta(+) T lymphocytes. Subsequently, we developed a six-tube test kit with selected Vbeta antibody combinations for easy and rapid detection of single ("clonal") Vbeta domain usage in large T-cell expansions.

RESULTS

The mean values of the Vbeta repertoire usage were stable during aging in blood TCRalphabeta(+) T lymphocytes as well as in the CD4(+) and CD8(+) T-cell subsets, although the standard deviations increased in the elderly. The increased standard deviations were caused by the occurrence of oligoclonal T-cell expansions in the elderly, mainly consisting of CD8(+) T lymphocytes. The 15 detected T-cell expansions did not reach 40% of total TCRalphabeta(+) T lymphocytes and represented less than 0.4 x 10(9) cells per liter in our study. Vbeta usage of the CD4(+) and CD8(+) subsets was comparable for most tested Vbeta domains, but significant differences (P < 0.01) between the two subsets were found for Vbeta2, Vbeta5.1, Vbeta6.7, Vbeta9.1, and Vbeta22 (higher in CD4(+)), as well as for Vbeta1, Vbeta7.1, Vbeta14, and Vbeta23 (higher in CD8(+)). Finally, single Vbeta domain expression in large T-cell expansions can indeed be detected by the six-tube test kit.

CONCLUSIONS

The results of our study can now be used as reference values in studies on distortions of the Vbeta repertoire in disease states. The six-tube test kit can be used for detection of single Vbeta domain expression in large T-cell expansions (>2.0 x 10(9)/l), which are clinically suspicious of T-cell leukemia.

The role of the thymus in immune reconstitution in aging, bone marrow transplantation, and HIV-1 infection

The human thymus is a complex chimeric organ comprised of central (thymic epithelial space) and peripheral (perivascular space) components that functions well into adult life to produce naive T lymphocytes. Recent advances in identifying thymic emigrants and development of safe methods to study thymic function in vivo in adults have provided new opportunities to understand the role that the human thymus plays in immune reconstitution in aging, in bone marrow transplantation, and in HIV-1 infection. The emerging concept is that there are age-dependent contributions of thymic emigrants and proliferation of postthymic T cells to maintain the peripheral T cell pool and to contribute to T cell regeneration, with the thymus contributing more at younger ages and peripheral T cell expansion contributing more in older subjects. New studies have revealed a dynamic interplay between postnatal thymus output and peripheral T cell pool proliferation, which play important roles in determining the nature of immune reconstitution in congenital immunodeficiency diseases, in bone marrow transplantation, and in HIV-1 infection. In this paper, we review recent data on human postnatal thymus function that, taken together, support the notion that the human thymus is functional well into the sixth decade and plays a role throughout life to optimize human immune system function.

Retrovirus-mediated gene transfer in primary T lymphocytes: influence of the transduction/selection process and of ex vivo expansion on the T cell receptor beta chain hypervariable region repertoire

We have initiated a phase I/II clinical trial, involving the use of herpes simplex thymidine kinase gene (HS-tk)-expressing donor primary T cells, in order to modulate the graft-versus-host disease (GvHD) occurring after allogeneic hematopoietic stem cell transplantation. The preparation of gene-modified T cells (TkTCs) required a 12-day ex vivo culture comprising an initial OKT3 and IL-2 stimulation, a retrovirus-mediated transduction, and a 7-day selection step in the presence of G418 and IL-2. The low transduction efficiency as well as the culture conditions may significantly alter the diversity of the T cell repertoire. We therefore examined the T cell repertoire of HS-tk-expressing T cell samples from 11 different donors by the Immunoscope method. This method analyzes the hypervariable region of the T cell receptor beta chain (TCRBV) by amplifying the complementarity-determining region 3 (CDR3) and determining size diversity. In all examined samples (four of which were infused into patients), all TCRBV subfamilies were represented with, however, a significant skewing within a minority of subfamilies. Kinetic studies demonstrated that this skewing appeared between day 7 and day 12, with dates of appearance variable from one subfamily to another. In addition, the repertoire analysis of two different culture products, harvested and produced at different times from the same donors, suggested that some repertoire abnormalities could be donor specific. Quantitative analysis revealed no major modifications in gene usage, even in skewed TCRBV subfamilies, with a few clonal expansions concerning a limited number of TCRBV subfamilies. Importantly, identical abnormalities were found in control cells grown in parallel under similar conditions but not transduced or selected, thus demonstrating that these abnormalities were not related to the transduction or the selection process, but rather to the ex vivo culture. The initial stimulus used for T cell activation is a major source of TCRBV perturbation, since replacing the OKT3 + IL-2 stimulus by CD3 + CD28 monoclonal antibody-coated beads prevented the occurrence of alterations. Overall, the HS-tk-expressing T cells used in our clinical trial exhibit limited TCR repertoire skewing that is not due to the transduction/selection procedure. However, future T cell gene transfer protocols for clinical trials should be designed to take into account or possibly prevent such T cell repertoire alterations.

In vitro and in vivo responses to interleukin 12 are maintained until the late SIV infection stage but lost during AIDS

The in vitro proliferative responses of macaque peripheral blood mononuclear cells (PBMCs) to IL-12 appeared similar before and early after SIV infection, whereas macaque PBMCs sampled during symptomatic stages of SIV infection showed markedly decreased responses. IL-12 was administered to SIVmac239-infected rhesus macaques either during the asymptomatic or the AIDS stage of infection in efforts to evaluate the effect of this cytokine on immune responses, viral loads, and hematopoietic functions in vivo. IFN-gamma secretion levels induced during the asymptomatic or early symptomatic phase were similar to preinfection induced levels, whereas in later AIDS stages this response was lost. The constitutive levels of other measured cytokines were not affected by IL-12 administration in vivo. The frequency and activity of circulating NK cells were markedly enhanced at early stages but not at symptomatic stages of SIV infection. pCTL frequencies were enhanced at early symptomatic stages but not at late AIDS stages. Despite its immunomodulatory effect, IL-12 did not seem to exacerbate or inhibit the replication of SIV in vivo, or the frequency of circulating infected lymphocytes. IL-12 administration was associated with a significant yet subclinical and transient decrease in hematocrit and hemoglobin levels without evidence of hemolysis, hemodilution, or reduction in the frequency of colony-forming unit potential of bone marrow CD34+ cells. This phenomenon may be explained by a functional inhibition of differentiation rather than an altered generation of bone marrow precursors. Thus, these results suggest that IL-12 may benefit HIV-1-infected patients only as long as their immune system retains its capability to respond to cytokine stimulation.

Alteration of tumor necrosis factor–α T-cell homeostasis following potent antiretroviral therapy: contribution to the development of human immunodeficiency virus–associated lipodystrophy syndrome

Highly-active antiretroviral therapy (HAART) has lead to a dramatic decrease in the morbidity of patients infected with the human immunodeficiency virus (HIV). However, metabolic side effects, including lipodystrophy-associated (LD-associated) dyslipidemia, have been reported in patients treated with antiretroviral therapy. This study was designed to determine whether successful HAART was responsible for a dysregulation in the homeostasis of tumor necrosis factor- (TNF-), a cytokine involved in lipid metabolism. Cytokine production was assessed at the single cell level by flow cytometry after a short-term stimulation of peripheral blood T cells from HIV-infected (HIV+) patients who were followed during 18 months of HAART. A dramatic polarization to TNF- synthesis of both CD4 and CD8 T cells was observed in all patients. Because it was previously shown that TNF- synthesis by T cells was highly controlled by apoptosis, concomitant synthesis of TNF- and priming for apoptosis were also analyzed. The accumulation of T cells primed for TNF- synthesis is related to their escape from activation-induced apoptosis, partly due to the cosynthesis of interleukin-2 (IL-2) and TNF-. Interestingly, we observed that LD is associated with a more dramatic TNF- dysregulation, and positive correlations were found between the absolute number of TNF- CD8 T-cell precursors and lipid parameters usually altered in LD including cholesterol, triglycerides, and the atherogenic ratio apolipoprotein B (apoB)/apoA1. Observations from the study indicate that HAART dysregulates homeostasis of TNF- synthesis and suggest that this proinflammatory response induced by efficient antiretroviral therapy is a risk factor of LD development in HIV+ patients.