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

CD8 TCR β chain repertoire expansions and deletions are related with immunologic markers in HIV-1-infected patients during treatment interruption

BACKGROUND

HIV-1-infected individuals progressively loss CD4(+) T cells leading to immunosuppression and raising the risk of opportunistic infections. CD8(+) T-cells play an important role in the immune response against virus infections through their TCR.

OBJECTIVE

To evaluate the CD8-TCR repertoire and immunologic markers in HIV-1-infected patients.

STUDY DESIGN

Ten chronic HIV-1-infected individuals on prolonged effective antiretroviral treatment (ART) were analyzed at baseline (before treatment interruption), after at least one year of treatment interruption (TI) and after at least one year from ART resume (TR). Twenty-four TCR-Vβ gene families were analyzed by a modified CDR3 spectratyping method in isolated CD8(+) T-cells. Immune activation, exhaustion and subpopulation markers were analyzed by flow cytometry.

RESULTS

Expansion of Vβ10, Vβ14 and Vβ15 families, associated with low cell activation and stable exhaustion markers, were found at TI. Moreover, an increment of effector memory cells was found. Besides, depletion of Vβ20, Vβ28, and Vβ29 families, associated with an increase in cell activation and exhaustion markers, at TI were also found. These alterations seemed to be more pronounced in patients who had longer time from diagnosis. ART seemed to restore altered CD8(+) T-cell repertoire and most of the immunologic markers.

CONCLUSIONS

During TI (that was more pronounced in patients with longer HIV-1 infection) it was observed the expansion of Vβ families correlated with decreased cell activation, while Vβ families correlated with cell activation and exhaustion were depleted. These specific repertoire alterations reverted after ART resume.

Impact of gamma-chain cytokines on T cell homeostasis in HIV-1 infection: therapeutic implications

CD4(+) T cell lymphocytes are a major target for human immunodeficiency virus type-1 (HIV-1) infection. During this chronic infection, CD4(+) T cell loss (induced through direct viral replication), generalized immune activation and increased susceptibility to apoptosis result in impaired T cell homeostasis with subsequent development of opportunistic infections and cancers. Highly active antiretroviral therapy (HAART) has a well-defined, beneficial effect on HIV-1-related clinical outcome; however, it does not lead to normalization of immune dysregulation. In order to boost both CD4(+) T cell restoration and HIV-1 specific immunity, immunotherapy with gamma-chain cytokines has been used in HIV-1-infected patients during concomitant HAART. In this review, we summarize the role of gamma-chain cytokines, especially interleukin (IL)-2 and IL-7, in influencing T cell homeostasis and proliferation, and discuss how immunotherapy with these cytokines may be beneficial to reconstitute the T cell compartment in the context of HIV-1 infection. The intriguing results of two large trials evaluating the efficacy of IL-2 in restoring immune function during HIV-1 infection are also discussed. In addition, we consider the promises and caveats of the first phase I/II clinical trials with IL-7 in HIV-1-infected patients and the knowledge that is still lacking in the field of T cell reconstitution through gamma-chain cytokines.

Broad TCR usage in functional HIV-1-specific CD8+ T cell expansions driven by vaccination during highly active antiretroviral therapy

During chronic HIV-1 infection, continuing viral replication is associated with impaired proliferative capacity of virus-specific CD8+ T cells and with the expansion and persistence of oligoclonal T cell populations. TCR usage may significantly influence CD8+ T cell-mediated control of AIDS viruses; however, the potential to modulate the repertoire of functional virus-specific T cells by immunotherapy has not been explored. To investigate this, we analyzed the TCR Vbeta usage of CD8+ T cells populations which were expanded following vaccination with modified vaccinia virus Ankara expressing a HIV-1 gag/multiepitope immunogen (MVA.HIVA) in HIV-1-infected patients receiving highly active antiretroviral therapy. Vaccinations induced the re-expansion of HIV-1-specific CD8+ T cells and these showed broad TCR Vbeta usage which was maintained for at least 1 year in some individuals. By contrast, virus-specific CD8+ T cell populations in the same donors which failed to expand after vaccination and in unvaccinated controls were oligoclonal. Simultaneously, we observed that CD8+ T cells recognizing vaccine-derived HIV-1 epitopes displayed enhanced capacity to proliferate and to inhibit HIV-1 replication in vitro, following MVA.HIVA immunizations. Taken together, these data indicate that an attenuated viral-vectored vaccine can modulate adaptive CD8+ T cell responses to HIV-1 and improve their antiviral functional capacity. The potential therapeutic benefit of this vaccination approach warrants further investigation.

An immunological comparison of third companion in advanced drug-naive HIV-infected patients

An immunological comparison of three different third companions (abacavir [ABC], efavirenz [EFV], ritonavir-boosted indinavir [IDVr]) on a backbone of either zidovudine plus didanosine (AZT/ddI) or zidovudine plus lamivudine (AZT/3TC) was performed in 76 HIV-infected, advanced-naive patients. Baseline median CD4 count and viremia were 217/microL and 238,301 copies/mL, respectively. Immunologic parameters were measured at baseline and after months of therapy. By the end of the study, 36 patients (mostly in the protease inhibitor [PI]-containing arms) had dropped out of the study; 22/36 cases of drop out were due to tolerability issues. All regimens resulted in increases in CD4 counts, with the most solid changes seen in patients using ABC as a third companion. Median HIV plasma viremia at month 12 was <50 copies/mL, and viremia was undetectable in 26/38 patients (68%). At the end of the study period, HIV antigen- and mitogen-stimulated proliferation overall was better in patients using either of the PI-boosted third companions. In these patients, the strongest down-modulation of activation marker-bearing cells was also observed. Finally, CD8+/28-/CD45RA+ lymphocytes (effector cells) were increased in all groups of patients with the exception of individuals receiving PI-boosted therapies. Results of this pilot study, although very preliminary, suggest that different combinations of antivirals result in a range of effects on immune cell functions. The clinical implications of these results need to be further analyzed in follow-up studies and in larger cohorts of patients.

Immunomodulants for the treatment of HIV infection: the search goes on

The natural history of HIV infection has been greatly modified by the introduction of powerful antiretroviral agents that act on multiple steps of HIV replication. Thus, antiretroviral therapy (ART) has prolonged the life of HIV-infected individuals, significantly impacting on the progression to AIDS. It was assumed that ART-induced suppression of HIV would have resulted in a degree of immune recovery sufficient enough to allow immune control over HIV replication independently of the use of drugs. Unfortunately, interruption of therapy, even after long periods of full suppression of viral replication, is almost inevitably associated with a prompt rebound of HIV viraemia. The outcome of this observation is that ART has to be considered as a lifelong therapy, with the associated resulting problems of the emergence of multi-drug resistant viral strains, toxic effects, costs and compliance. The use of immunomodulants in association with ART could achieve the goal of boosting the immune response to a threshold, permitting the immune response to indefinitely suppress HIV replication.

Fluctuations of functionally distinct CD8+ T-cell clonotypes demonstrate flexibility of the HIV-specific TCR repertoire

T-cell receptor (TCR) diversity of virus-specific CD8+ T cells likely helps prevent escape mutations in chronic viral infections. To understand the dynamics of the virus-specific T cells in more detail, we followed the evolution of the TCR repertoire specific for a dominant HLA-B*08-restricted epitope in Nef (FLKEKGGL) in a cohort of subjects infected with HIV. Epitope-specific CD8+ T cells used structurally diverse TCR repertoires, with different TCRbeta variable regions and with high amino acid diversity within antigen recognition sites. In a longitudinal study, distinct Vbeta populations within the HIV-specific TCR repertoire expanded simultaneously with changes in plasma viremia, whereas other Vbeta populations remained stable or even decreased. Despite antigenic variation in some subjects, all subjects had the consensus sequence present during the study period. Functional analysis of distinct Vbeta populations revealed differences in HIV-specific IFN-gamma secretion ex vivo as well as differences in tetramer binding, indicating functional heterogeneity among these populations. This contrasts with findings in a subject on antiretroviral therapy with suppression of viremia to less than 50 copies/mL, where we observed long-term persistence of a single clonotype. Our findings illustrate the flexibility of a heterogeneous HIV-1-specific CD8+ TCR repertoire in subjects with partial control of viremia.

The immune paradox of sarcoidosis and regulatory T cells

Sarcoidosis is characterized by extensive local inflammation (granuloma, cytokine secretion) associated with anergy (poor response to antigens in vitro and in vivo). We postulated that this paradoxical situation would correspond to a disequilibrium between effector and regulatory T lymphocytes (T reg cells). We show that CD4⁺CD25^brightFoxP3⁺ cells accumulate at the periphery of sarcoid granulomas, in bronchoalveolar lavage fluid, and in peripheral blood of patients with active disease. These cells exhibited powerful antiproliferative activity, yet did not completely inhibit TNF-α production. Sarcoidosis is therefore associated with a global T reg cell subset amplification whose activity would be insufficient to control local inflammation. At the same time, peripheral T reg cells exert powerful antiproliferative activity that may account for the state of anergy. Altogether, these findings advance our conceptual understanding of immune regulation in a way that resolves the immune paradox of sarcoidosis and permit us to envisage a profound clinical impact of T reg cell manipulation on immunity.

Antiviral T cell responses: phalanx or multipronged attack?

Around 700 BCE, a new military formation called the phalanx was established in ancient Greece: a tight column of heavy infantry carrying long spears, or pikes, used in a single prong of attack. Later, in the battle of Marathon described by Herodotus, the Greeks learned the advantages of multipronged attacks, a strategy still used in modern warfare. Is the immune system similar in its approach to combating pathogens or tumors?

Significance of senescence for virus-specific memory T cell responses: rapid ageing during chronic stimulation of the immune system

There is a generalized age-related decline in immune responses which leads to increased susceptibility of elderly to infection and, possibly, to autoimmune disease and cancer. This is associated with phenotypic changes of CD8+ T lymphocytes that include the loss of costimulatory molecules CD28 and CD27, which are important for proliferation and cell survival of CD8+ T cells. Loss of these molecules is associated with less ability to respond to recurrent infection. Functional changes within T cells during ageing include a reduction in the number of naive T cells and a progressively limited T cell repertoire. Furthermore, persistent life-long antigenic stress upon the memory pool leads to telomere erosion and concomittant loss of proliferative capacity, a phenomenon known as replicative senesence. In this review, we discuss that replicative senescence, or clonal exhaustion, may also occur in relatively young individuals, as evidenced from HIV-infected individuals and healthy Ethiopians. We discuss data suggesting that T cell defects may arise in individuals because of chronic antigen activation leading to rapid ageing of the memory CD8+ T cell pool.

Granule-dependent mechanisms of lysis are defective in CD8 T cells of HIV-infected, antiretroviral therapy-treated individuals

BACKGROUND

HIV-specific cytotoxic T-cell (CTL) responses are defective in HIV-infected patients undergoing antiretroviral therapy (ART). This defect has been attributed to the decreased antigenic burden secondary to ART-associated suppression of HIV-replication, and is responsible for the rebounds of viraemia that occur when patients interrupt therapy. CTL are stimulated by type 1 cytokines and can kill targets via granule-dependent (perforin and granzymes) and -independent (tumour necrosis factor-alpha, CD95) mechanisms.

METHODS

Granule-dependent and granule-independent mechanisms of CTL killing, as well as type 1 cytokine production by CD4 T cells, were analysed in 57 chronically HIV-infected ART-treated or ART-untreated individuals.

RESULTS

The results can be summarized as follows: the frequency of gp160 (env)-specific interferon-gamma-secreting CD8 T lymphocytes correlates positively with HIV viraemia in ART-treated and -untreated patients; Env-specific perforin- and granzymes-expressing CD8 T lymphocytes, and Env-stimulated perforin and granzymes mRNA, are reduced in ART-treated patients independently of HIV viral load and of type 1 cytokine production; tumour necrosis factor-alpha production is increased in ART-treated individuals; and Env-specific immature CD8+28+27+ cells are only marginally augmented in ART-treated patients, Similar results are observed in cytomegalovirus-specific CD8 T cells and peripheral blood mononuclear cells.

CONCLUSIONS

A defect of CTL function that selectively affects the granule-dependent mechanisms of lysis is observed in ART-treated individuals. Because interferon-gamma production is higher in these patients, this could be a defect primarily involving CTL. These data suggest an independence of CD8 T-cell numbers and their lytic ability in HIV-infected, ART-receiving patients. Immunomodulants are needed to successfully treat HIV infection.

Distinct clonal repertoire of brain CD8+ cells in simian immunodeficiency virus infection

OBJECTIVE

Infection with simian immunodeficiency virus (SIV), like HIV, can lead to central nervous system (CNS) abnormalities. One of the alterations observed in the brain is the accumulation of highly activated CD8 lymphocytes that, while fighting the infection, may cause tissue damage. In order to determine whether these CD8 cells in the brain comprise a distinct clonal population the expression of T-cell receptor (TCR) genes of two SIV-infected monkeys with CNS abnormalities were analyzed, comparing brain to periphery.

METHODS

RNA from magnetically sorted CD8+ cells obtained from the brain, blood, lymph nodes, and spleen was analyzed for the distribution of 24 Vbeta family genes by reverse transcriptase-polymerase chain reaction followed by Southern blot. The CDR3 region of the most enriched family in each brain was sequenced in all the sites for comparison.

RESULTS

The pattern of Vbeta distribution in the brain and the periphery was polyclonal, but an increase in certain Vbeta families was found in the brain, suggesting that regional mechanisms participate in the determination of the local clonal specificities. The sequence of the CDR3 domain of predominant Vbeta families in the brain revealed that approximately one-third of the CD8 cells were not identified in the periphery.

CONCLUSION

CD8 cells in the brain exhibit a distinct clonal repertoire. This distinction may have implications for regional immunity, regulation, or selection of site-specific viral mutants.

Age-related immune reconstitution during highly active antiretroviral therapy in human immunodeficiency virus type 1-infected children

OBJECTIVES

To evaluate the immune reconstitution in HIV-1-infected children in whom highly active antiretroviral therapy (HAART) controlled viral replication and to assess the existence of a relation between the magnitude of this restoration and age.

METHODS

All HIV-1-infected children in whom a new HAART decreased plasma viral load below 400 copies/ml after 3 months of therapy were prospectively enrolled in a study of their immune reconstitution. Viral load, lymphocyte phenotyping, determination of CD4+ and CD8+ T cell receptor repertoires and proliferative responses to mitogens and recall antigens were assessed every 3 months during 1 year.

RESULTS

Nineteen children were evaluated. Naive and memory CD4+ percentages were already significantly increased after 3 months of HAART. In contrast to memory CD4+ percentages, naive CD4+ percentages continued to rise until 12 months. Age at baseline was inversely correlated with the magnitude of the rise in naive CD4+ cells after 3, 6 and 9 months of therapy but not after 12 months. Although memory and activated CD8+ cells were already decreasing after 3 months, abnormalities of the CD8 T cell receptor repertoire and activation of CD8+ cells persisted at 1 year. HAART increased the response to mitogens as early as 3 months after starting therapy.

CONCLUSIONS

In children the recovery of naive CD4+ cells occurs more rapidly if treatment is started at a younger age, but after 1 year of viral replication control, patients of all ages have achieved the same level of restoration. Markers of chronic activation in CD8+ cells persist after 1 year of HAART.

Diagnostic role of tests for T cell receptor (TCR) genes

Rapid advances in molecular biological techniques have made it possible to study disease pathogenesis at a genomic level. T cell receptor (TCR) gene rearrangement is an important event in T cell ontogeny that enables T cells to recognise antigens specifically, and any dysregulation in this complex yet highly regulated process may result in disease. Using techniques such as Southern blot hybridisation, polymerase chain reaction, and flow cytometry it has been possible to characterise T cell proliferations in malignancy and in diseases where T cells have been implicated in the pathogenesis. The main aim of this article is to discuss briefly the process of TCR gene rearrangement and highlight the disorders in which expansions or clonal proliferations of T cells have been recognised. It will also describe various methods that are currently used to study T cell populations in body fluids and tissue, their diagnostic role, and current limitations of the methodology.

The functional CD8 T cell response to HIV becomes type-specific in progressive disease

High levels of HIV-specific CD8 T cells are demonstrable throughout HIV disease using laboratory assays that measure responses to consensus epitopes. In acute infection, the dynamics of the antiviral CD8 T cell response correlate well with the decline in viremia. However in chronic infection, although responses are detected against a broader spectrum of epitopes, virus-specific CD8 T cells are apparently unable to control viral replication. To investigate whether CD8 T cells responding to consensus epitopes may have lost their in vivo relevance in the chronic phase because of viral evolution driven by immune pressure, we compared the CD8 T cell response to CD4 T cell targets infected with either lab-adapted HIV(IIIB) or the patient's own virus. The magnitude of the IFN-gamma response declined with disease progression, especially to autologous virus. T cell receptor (TCR) clonotypes of HIV(IIIB) and autologous virus-responding cells were determined by sequencing TCR beta chain variable (TCRBV) genes. In two of three asymptomatic donors, the dominant clonotypes overlapped, whereas in five symptomatic patients, the TCR clonotypes responding to HIV(IIIB) virus were completely different from those responding to autologous virus. Moreover, in cytolytic assays, T cell lines derived from IFN-gamma(+) cells responding to lab-adapted or autologous virus cross-recognized target cells infected with either virus in asymptomatic subjects with shared TCR clonotypes but not in progressors with differing clonotypes. Therefore, in advanced-stage patients, viral-specific CD8 T cells recognizing consensus epitopes persist from an earlier response but no longer effectively recognize autologous virus.

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.