Interleukin-2 and human immunodeficiency virus infection: pathogenic mechanisms and potential for immunologic enhancement

Testes de contato e HIV: avaliação comparativa quanto à confiabilidade dos resultados

FUNDAMENTOS: A ocorrência da dermatite de contato alérgica em pacientes soropositivos para o HIV foi pouco estudada até o momento (apenas relatos de caso). Os testes de contato são considerados o exame complementar padrão para a investigação diagnóstica desse tipo de reação alérgica e não foram avaliados cientificamente nesse grupo de pacientes. OBJETIVO: Avaliar a aplicabilidade dos testes de contato em pacientes soropositivos para o HIV. MÉTODO: Estudo transversal, descritivo, com controles. Um grupo com 16 pacientes soropositivos para o HIV foi comparado a um grupo com 32 pacientes com sorologia desconhecida para o HIV com relação à positividade aos testes. Foi realizada análise estatística bivariada com nível de significância p < 0,05. RESULTADOS: Entre o grupo de pacientes soropositivos para o HIV, sete (43,75%) tiveram testes positivos, e, entre o grupo de pacientes que rotineiramente realizaram testes de contato (e com sorologia desconhecida ao HIV), 18 (56,25%) tiveram testes positivos. CONCLUSÕES: Os achados deste trabalho sugerem que, apesar da imunodeficiência, a memória imunológica específica e a capacidade de responder positivamente aos testes podem permanecer. Dessa forma, esse recurso diagnóstico importante para as alergias dermatológicas não perderia validade ao ser aplicado no conjunto de pacientes que convivem com o HIV.

Host factors influencing susceptibility to HIV infection and AIDS progression

Transmission of HIV first results in an acute infection, followed by an apparently asymptomatic period that averages ten years. In the absence of antiretroviral treatment, most patients progress into a generalized immune dysfunction that culminates in death. The length of the asymptomatic period varies, and in rare cases infected individuals never progress to AIDS. Other individuals whose behavioral traits put them at high-risk of HIV transmission, surprisingly appear resistant and never succumb to infection. These unique cases highlight the fact that susceptibility to HIV infection and progression to disease are complex traits modulated by environmental and genetic factors. Recent evidence has indicated that natural variations in host genes can influence the outcome of HIV infection and its transmission. In this review we summarize the available literature on the roles of cellular factors and their genetic variation in modulating HIV infection and disease progression.

HIV-1 Nef impairs the dynamic of DC/NK crosstalk: different outcome of CD56(dim) and CD56(bright) NK cell subsets

Dendritic cells (DCs) and natural killer (NK) cells are essential components of the innate immunity and play a critical role in the first phase of host defense against infection. Interactions between DCs and NK cells have been demonstrated in a variety of settings, with evidence emerging of complex bidirectional crosstalk between the two cell types. The accessory HIV-1 Nef protein is a crucial determinant for viral replication and pathogenesis. We previously demonstrated that Nef, hijacking DC functional activity, subverts the DC arm of immune response to escape the adaptive immune attack. Here, we monitor the effect of Nef on the outcome of the innate immune response, focusing on the impact of Nef on DC/NK crosstalk. We demonstrate that Nef up-regulates the ability of DCs to stimulate the immunoregulatory NK cells (CD56(bright)) as assessed by the activated phenotype, up-regulation of their proliferative response and INF-gamma release. On the other hand, Nef-pulsed DCs inhibit cytotoxic NK cells (CD56(dim)), as assessed by the reduced HLA-DR surface expression, reduced proliferation and cytotoxic activity. Moreover, in the presence of Nef-pulsed DCs, we found a significant up-regulation of TNF-alpha secretion and a significant reduction of IL-10, GM-CSF, MIP-1alpha and RANTES secretion. Our findings suggest that the Nef-induced dysregulation in the DC/NK cell crosstalk may represent a potential mechanism through which HIV escapes innate immune surveillance.

Manifestations of SIV-induced ocular pathology in macaque monkeys

Simian immunodeficiency virus has been shown to cause acquired immunodeficiency syndrome in macaque monkeys. Data gathered from clinical examination and fundus photography have shown that the lentivirus is capable of the induction of choroidal lesions and retinal hemorrhages in the macaque. These findings demonstrate the potential value of the macaque monkey eye as a model of the retinal pathology routinely seen in human AIDS patients.

Differential Expression of Perforin in Cytotoxic Lymphocyte in HIV/AIDS Patients of China

Cytotoxic lymphocytes are critical in the control of HIV replication, it has been shown that perforin is the key effector of killing machinery for CTLs and NK cells, so we investigated the circulating levels of perforin in CD8+ T cells and NK cells by flow cytometry intracellular stain in Chinese HIV infected individuals, its association with disease progression was analyzed. Our results showed that NK cells express perforin more efficiently than CD8+ T cells, CD8+ T cells expressed perforin higher than that of healthy controls, but NK cells expressed lower perforin than that of healthy controls, both were not correlated with disease progression. but significantly associated with their numbers, anti-retrovirus therapy had no evident effects on peforin expression in CD8+ T cells, but enhanced perfrin expression in NK cells, perforin expression in CD8+ T cells and CD16+ NK cells correlate with CD4+ T cell counts significantly in HAART-treated group. Therefore, different mechanisms may be involved in regulating peripheral perforin expression in different cell types.

Loss of the CD56hiCD16- NK cell subset and NK cell interferon-gamma production during antiretroviral therapy for HIV-1: partial recovery by human growth hormone

Previous studies have shown that human natural killer (NK) cells are lost from the periphery and are functionally suppressed during HIV-1 infection, and that the administration of highly active antiretroviral therapy (HAART) results in a recovery of NK cell numbers in HIV-1-infected individuals. However, despite this recovery, interleukin (IL)-2 + IL-12-driven interferon (IFN)-gamma production by NK cells has been shown to remain suppressed after HAART. Here we show that the innate immune factor IL-15 in combination with IL-12 is also unable to recover NK cell IFN-gamma production in HAART-treated individuals. Furthermore, we also demonstrate an imbalance in the distribution of CD56loCD16hi and CD56hiCD16- NK subsets after successful HAART, CD56hiCD16- cells being reduced substantially in HIV-1 patients on HAART. Treatment of patients with combined human growth hormone and antiretroviral therapy resulted in further enhancement in the absolute numbers and the proportion of NK cells in some individuals in the absence of parallel effects on CD4+ T cells. Furthermore, in these individuals HAART with growth hormone resulted in an enhancement of cytokine-driven NK cell activation and IFN-gamma production compared to the HAART-only baseline.

Interferon-alpha restores HIV-induced alteration of natural killer cell perforin expression in vivo

OBJECTIVE

The percentage and the activity of natural killer (NK) cells are known to be decreased in HIV-infected patients. However, the mechanisms responsible for this NK deficiency are poorly understood. Because of the role of NK cells in the host defence against microbial infections, this defect contributes to the virus-induced immune deficiency. The aim of the present study was to better understand this defect in order to be able to restore NK function in HIV infection.

DESIGN AND METHODS

The expression of the cytolytic mediators perforin and granzyme A was analysed by flow cytometry, the lytic activity of peripheral blood NK cells of HIV-infected patients was analysed by cytotoxic assay, and the expression of perforin was followed during administration of interferon (IFN)alpha attached to polyethylene glycol (PEG)-IFNalpha.

RESULTS

The lytic activity and the expression of perforin and granzyme A was low in NK cells of infected individuals in comparison with normal control volunteers. In both groups NK cytotoxic capacity was linked to perforin expression. The low perforin expression in HIV-infected subjects negatively correlated with HIV RNA plasma level. administration of PEG-IFNalpha restored perforin expression even in patients whose viral load was not reduced by this treatment.

CONCLUSIONS

These results suggest that HIV-induced NK deficiency could be partly mediated by a defect in perforin and granzyme A expression, and that PEG-IFNalpha could be used in infected subjects to directly improve their natural immunity in addition to eventually reducing their viraemia.

Antisense cyclic adenosine 5'-monophosphate response element modulator up-regulates IL-2 in T cells from patients with systemic lupus erythematosus

The cAMP response element modulator (CREM) has been shown to bind specifically to the -180 site of the IL-2 promoter in vitro. CREM protein is increased in T cells of patients with systemic lupus erythematosus (SLE), and it has been considered responsible for the decreased production of IL-2. In this work we show that transcriptional up-regulation is responsible for the increased CREM protein levels and that CREM binds to the IL-2 promoter in live SLE T cells. Suppression of the expression of CREM mRNA and protein by an antisense CREM plasmid, which was force expressed in SLE T cells by electroporation, resulted in decreased CREM protein binding to the IL-2 promoter and increased expression of IL-2 mRNA and protein. Our data demonstrate that antisense constructs can be used to effectively eliminate the expression of a transcriptional repressor. This approach can be used therapeutically in conditions where increased production of IL-2 is desired.

Management of HIV-infected Patients with Multidrug-resistant Virus

Heavily pretreated HIV-infected patients with multidrug-resistant virus remain a clinical challenge to the treating physician. While the goal of therapy in such patients is still controversial, sustained immunologic and clinical benefit have only been demonstrated with complete suppression of plasma viral load below detectable levels. Expert use of resistance testing may help in the selection of the salvage regimen, and monitoring of plasma drug levels may help optimize the potency and tolerability, especially of complex, multiple drug regimens where adherence remains a critical determinant of treatment outcome. The potential roles of newer agents, adjuvants, treatment interruptions, and immune-based therapies remain under investigation.

T cell signaling mechanisms that regulate HIV-1 infection

The ability of human immunodeficiency virus type-1 (HIV-1) to establish a persistent infection is critically dependent on the cellular signals that regulate HIV-1 replication within target cells. The balance between numerous host factors that either enhance or suppress viral infection determines the clinical outcome. Perturbation of the steady-state level of viral replication can significantly influence the course and the speed at which the infection develops into clinical disease. Activation signals delivered to T cells by cytokines and antigen-presenting cells (APC), are key modulators of viral replication. Our laboratory seeks to decipher how HIV-1 exploits T cell signaling mechanisms and host factors that regulate viral replication. Elucidation of the molecular mechanisms by which cellular signals regulate the HIV-1 life cycle within target cells will significantly advance our understanding of host-virus interactions.

An IL-2/Ig fusion protein influences CD4+ T lymphocytes in naive and simian immunodeficiency virus-infected Rhesus monkeys

The T cell-stimulatory cytokine interleukin 2 (IL-2) is being evaluated as a therapeutic in the clinical settings of HIV infection and cancer. However, the clinical utility of IL-2 may be mitigated by its short in vivo half-life, toxic effects, and high production costs. We show here that an IL-2/Ig fusion protein possesses IL-2 immunostimulatory activity in vitro and a long in vivo half-life. IL-2/Ig treatment of healthy rhesus monkeys induced significant increases in CD4(+) T lymphocyte counts and expression of CD25 by these cells. Short courses of IL-2/Ig treatment of simian immunodeficiency virus (SIV)-infected rhesus monkeys in conjunction with antiretroviral drugs resulted in increased CD25 expression on T lymphocytes, and transient increases in CD4(+) T lymphocyte counts. Plasma viremia did not increase in these treated animals. Treatment of healthy or SIV-infected rhesus monkeys with a plasmid encoding the IL-2/Ig protein did not affect CD4(+) T lymphocytes. These results demonstrate that IL-2/Ig has potential utility as an immunostimulatory therapeutic.

Cytokines and HIV-1: interactions and clinical implications

Cytokines play an important role in controlling the homoeostasis of the immune system. Infection with HIV results in dysregulation of the cytokine profile in vivo and in vitro. During the course of HIV-1 infection secretion of T-helper type 1 (Th1) cytokines, such as interleukin (IL)-2, and antiviral interferon (IFN)-gamma, is generally decreased, whereas production of T helper type 2 (Th2) cytokines, IL-4, IL-10, proinflammatory cytokines (IL-1, IL-6, IL-8) and tumour necrosis factor (TNF)-alpha, is increased. Such abnormal cytokine production contributes to the pathogenesis of the disease by impairing cell-mediated immunity. A number of cytokines have been shown to modulate in vitro HIV-1 infection and replication in both CD4 T lymphocytes and cells of macrophage lineage. HIV-inductive cytokines include: TNF-alpha, TNF-beta, IL-1 and IL-6, which stimulate HIV-1 replication in T cells and monocyte-derived macrophages (MDM), IL-2, IL-7 and IL-15, which upregulate HIV-1 in T cells, and macrophage-colony stimulating factor, which stimulates HIV-1 in MDM. HIV-suppressive cytokines include: IFN-alpha, IFN-beta and IL-16, which inhibit HIV-1 replication in T cells and MDM, and IL-10 and IL-13, which inhibit HIV-1 in MDM. Bifunctional cytokines such as IFN-gamma, IL-4 and granulocyte-macrophage colony-stimulating factor have been shown to have both inhibitory and stimulatory effects on HIV-1. The beta-chemokines, macrophage-inflammatory protein (MIP)-1alpha, MIP-1beta and RANTES are important inhibitors of macrophage-tropic strains of HIV-1, whereas the alpha-chemokine stromal-derived factor-1 suppresses infection of T-tropic strains of HIV-1. This review outlines the interactions between cytokines and HIV-1, and presents clinical applications of cytokine therapy combined with highly active antiretroviral therapy or vaccines.

The potential role of interleukin-2 in HIV

Interleukin-2 (IL-2) is a secretory cytokine produced by activated T cells that stimulates T cells, B cells, and natural killer cells to proliferate and release cytokines. In addition, IL-2 slows apoptosis of HIV-infected cells. Clinical studies have demonstrated that exogenous human recombinant IL-2 can be safely administered concurrently with potent antiretroviral therapy to HIV-infected patients. It was further demonstrated that recombinant human IL-2 therapy produces sustained increases in CD4+ cell number and function in patients with both early and late HIV disease. Further evaluation of the clinical efficacy of IL-2 in HIV-infected patients is expected to provide important information on the utility of recombinant human IL-2 in HIV disease.

Increased endosomal sorting of ligand to recycling enhances potency of an interleukin-2 analog

An interleukin-2 (IL-2) variant containing adjacent point mutations (L18M/L19S, termed 2D1) displaying binding affinity to the heterotrimeric IL-2 receptor similar to that of wild-type IL-2 (WT) had been previously found to surprisingly exhibit increased bioactivity in a peripheral blood lymphocyte proliferation assay. In order to provide an explanatory mechanism for this unexpected potency enhancement, we hypothesize that altered endocytic trafficking of the 2D1 variant might be responsible by increasing the number of ligand-receptor complexes. We demonstrate here that the internalization kinetics of 2D1 via the high affinity IL-2 receptor are equivalent to those of WT but that a significantly increased fraction of internalized 2D1 is sorted to recycling instead of to lysosomal degradation. We further find a reduced pH sensitivity of binding to IL-2 receptor alpha relative to IL-2 receptor beta compared with WT, which could be responsible for the altered sorting behavior of 2D1 in the acidic endosomal compartment. Accordingly, the 2D1 variant displays a half-life 36 h longer than that of IL-2 in T-lymphocyte culture at concentrations equal to the K(D) of the IL-2 receptor. The extended half-life of intact 2D1 provides enhanced mitogenesis as compared with IL-2. In addition, 2D1 stimulates natural killer cells to a lesser degree than IL-2 at equal concentrations. We conclude that this IL-2 variant provides increased mitogenic stimulation that could not be easily predicted from its cell surface receptor binding affinity while minimizing undesired stimulation of natural killer cells. This concept of altering trafficking dynamics may offer a generalizable approach to generating improvements in the pharmacological efficacy of therapeutic cytokines.

Improvement of lymphocyte proliferation in human immunodeficiency virus infection after recombinant interleukin-2 treatment

In this study, the effect of recombinant interleukin-2 (rIL-2) on the function of peripheral blood mononuclear cells (PBMC) from human immunodeficiency virus (HIV)-infected patients was examined. Using polymerase chain reaction (PCR), an impaired ability of PBMC from 8 patients to respond upon mitogen stimulation with expression of IL-2 and IL-2 receptor (IL-2R) messenger ribonucleic acid (mRNA) was found compared with healthy donors (p = 0.02 and p = 0.05, respectively). Flow cytometry was used to determine the expression of p55 interleukin-2 alpha-receptor (CD25) after phytohaemagglutinin (PHA)-stimulation. Induced CD25 expression in response to stimulation was lower in patient cells than in donor cells (in CD4+ (p = 0.01) and in CD8+ (p = 0.03)). After rlL-2 treatment, the functionality of ex vivo expanded PBMC from patients was restored to the level found in donors. Finally, the induced gene expressions for IL-2 and IL-2R were positively correlated (p < 0.0001), suggesting that the activation of the IL-2 and IL-2R genes in humans may share a common activation pathway, as has been found in monkeys infected by simian immunodeficiency virus (SIV). These results indicate the existence of a reversible IL-2 and IL-2R defect at the pretranscriptional or transcriptional level in PBMC from patients. This may help explain the T-cell anergy found during HIV-infection.

Treatment of idiopathic CD4 T lymphocytopenia with IL-2

Idiopathic CD4 T lymphocytopenia (ICL) is an unusual immune defect in which there is an unexplained deficit of CD4 T cells, leading to fungal, parasitic or other serious opportunistic infections. Current treatment efforts are directed at eliminating infections. Here we describe the use of a novel treatment, subcutaneous polyethylene glycol (PEG)-IL-2 injections, in a woman with this disorder, who had chronic severe mycobacterial disease which led to repeated hospitalizations, and advancing respiratory insufficiency. For this patient, PEG-IL-2, 50 000 U/m2, has been given by weekly subcutaneous injections for 5.5 years. This treatment has resulted in marked (and still continuing) long-term immunological improvement with normalized T cell functions and increased CD4 cell numbers. She has had substantial clinical improvement with clearing of mycobacterial disease, reducing hospitalizations and improved lung functions. The improvement seen in this patient suggests that low-dose IL-2 is a safe and practical therapy, which might be useful in other subjects with this potentially serious immune defect.

B7 cosignal potentiates apoptosis of uninfected CD4+ T lymphocytic cell lines primed by HIV envelope proteins

In lymphoid organs, follicular dendritic cells (FDCs), monocytes, and macrophages are targets for HIV infection and reservoirs for infectious virus. Strikingly, the apoptotic cells in these sites are essentially uninfected CD4+ T lymphocytes, but lie in close proximity to infected cells or FDCs carrying trapped HIV virions. To decipher this apoptotic pathway, we have established a two-step experimental system that reproduces in vitro the HIV envelope protein-mediated apoptosis restricted to uninfected CD4+ T lymphocytic cell lines. In this assay, uninfected CD4+ T cell targets undergo apoptosis following an initial priming step on HeLa cells expressing functional HIV envelope proteins at their plasma membrane and a second and necessary stimulation step via the CD3-TCR complex. The CD4+ T lymphocytic cells susceptible to apoptosis are, in contrast, resistant to cell fusion mediated by HIV envelope protein and express SDF-1. FDCs and macrophages are known to be high B7 expressors. Thus in lymph nodes, the cells that have trapped HIV particles in immune complexes at the plasma membrane present both HIV envelope proteins and B7.1 at their surface. We mimicked this situation in vitro by priming CD4+ T lymphocytes on cells expressing the costimulatory molecule B7 in addition to HIV envelope proteins, and show that it resulted in an acceleration and a twofold increase in apoptosis. Finally, we characterized two enzymes, PI3Kinase and PI-PLC, which are both downstream effectors of the CD4 (HIV envelope protein receptor) and CD28 (B7 receptor) activation pathways, and that participated in the early steps of priming for apoptosis.

Do viral load and CD8 cell count at initiation of tritherapy influence the increase of CD4 T-cell count?

BACKGROUND

Tritherapies including protease inhibitors improve clinical status and usually increase CD4 T cell count. However, the dissociation between the marked decreases in viral load and the incomplete restoration of CD4 cell counts with a three-drug combination has been reported. We assessed this potential difference among our patients.

METHODS

Patients were enrolled when a protease inhibitor was prescribed to them for the first time. Using a computerized medical record (ADDIS), we retrospectively assessed a potential relationship between the increase in CD4 T cells (deltaCD4) at M3, M6 and variables including sex, age, CDC staging, protease inhibitor, prior antiviral therapy, CD8 and viral load at baseline. We used Epi-Info 6.4 and BMDP software.

RESULTS

Data were analyzed on 154 patients. The median CD4 T cell count was 157 at baseline, 215 at month 3 and 202 at month 6. The median viral load was 52000 copies at baseline, 530 at month 3 and 500 at month 6. In a univariate analysis, a significant relationship was found between deltaCD4 and CD8 at baseline. A statistically significant negative correlation appeared between the CD8 cell count at baseline and deltaCD4 at M6 (r=-0.28, Pearson). Moreover, we found that there also was a relationship between deltaCD4 and viral load at baseline. There was a correlation between deltaCD4 at M6 and the viral load at M0 (r=0.37, Pearson). In a multiple regression model, after CD8 count at baseline had been accounted for, we found a significant correlation between deltaCD4 and viral load at baseline (multiple r=0.33 at M3, and 0.40 at M6).

CONCLUSIONS

Patients with a low viral load do not benefit from as great an increase in CD4 T cell count as others when they receive a tritherapy including protease inhibitors. These results suggest that another mechanism rather than direct viral pathogenicity leads to CD4 T cell destruction. This mechanism may not be efficiently stopped by antiviral therapy, especially protease inhibitors.

Ultra low dose interleukin-2 therapy promotes a type 1 cytokine profile in vivo in patients with AIDS and AIDS-associated malignancies

This study was undertaken to determine if prolonged daily subcutaneous administration of ultra low dose IL-2 could influence the constitutive endogenous production of a type 1 (IFN-gamma) cytokine in patients with AIDS or AIDS-associated malignancies. Using a quantitative reverse transcription PCR assay, we demonstrate that daily administration of one type 1 cytokine, IL-2, for 3 mo increases significantly the constitutive endogenous gene expression of another type 1 cytokine, IFN-gamma, in vivo. The predominant source of IFN-gamma appears to be IL-2-expanded natural killer cells and CD8(+) T cells. Moreover, PBMC obtained from these patients during IL-2 therapy showed normalization of a profound deficit in IFN-gamma protein production after stimulation with extracts from infectious agents in vitro. Our data suggest that prolonged exogenous administration of a type 1 cytokine in a nontoxic fashion to patients with AIDS and AIDS-associated malignancies can enhance significantly the endogenous type 1 cytokine profile in vivo. Consequently, ultra low dose IL-2 therapy has the potential to improve the immunodeficient hosts' immune response to infectious pathogens that require IFN-gamma for clearance.

Host factors in the pathogenesis of HIV disease

Host factors play an important role in determining rates of disease progression in human immunodeficiency virus (HIV)-infected individuals. HIV is able to subvert the host immune system by infecting CD4+ T cells that normally orchestrate immune responses and by inducing the secretion of proinflammatory cytokines that the virus can utilize to its own replicative advantage. The recognition that certain chemokine receptors serve as necessary co-factors for HIV entry into its target cells as well as the fact that ligands for these receptors can modulate the efficiency of HIV infection has expanded the number and scope of host factors that may impact the pathogenesis of HIV disease. This area of investigation will no doubt yield novel therapeutic strategies for intervention in HIV disease; however, caution is warranted in light of the enormous complexity of the pleiotropic cytokine and chemokine networks and the uncertainty inherent in manipulating these systems. HIV-infected long-term non-progressors represent an excellent model to study potential host factors involved in HIV disease pathogenesis. Genetic factors certainly have a major impact on the immune responses mounted by the host. In this regard, a polymorphism in the gene for the HIV co-receptor CC chemokine receptor 5 (CCR5), which serves as a co-receptor for macrophage (M)-tropic strains of HIV, affords a high degree of protection against HIV infection in individuals homozygous for the genetic defect and some degree of protection against disease progression in HIV-infected heterozygotes. HIV-specific immune responses, including cytotoxic T-lymphocyte (CTL) responses and neutralizing antibody responses, also appear to play salutary roles in protecting against disease progression.

Circulating CD8 T cells show increased interferon-gamma mRNA expression in HIV infection

IFN-gamma mRNA levels were measured in unstimulated PBMC and purified cell subpopulations, utilizing branched DNA assays, to characterize the cell type(s) that contribute to the in vivo increase in IFN-gamma gene expression seen in HIV infection. PBMC and CD8 T cells from HIV-seropositive subjects (HIV+) showed 2.5-fold increases in mean IFN-gamma mRNA levels compared to HIV-uninfected subjects (HIV-). Within individuals, CD8 T cells showed the highest IFN-gamma expression regardless of HIV status, which suggests that HIV infection enhances the IFN-gamma gene expression in CD8 T cells rather than inducing a shift to and/or increasing expression of IFN-gamma mRNA in other cell types. HIV+ subjects with increased PBMC IFN-gamma mRNA had elevated plasma levels of HIV RNA, neopterin, and beta 2-microglobulin. No differences in IFN-gamma mRNA levels were seen among HIV+ stratified by CD4 T cell number. Increased IFN-gamma may result from or be a contributing factor to increased viral load.