Contribution of immune activation to the pathogenesis and transmission of human immunodeficiency virus type 1 infection

Predominant infection of CD150+ lymphocytes and dendritic cells during measles virus infection of macaques

Measles virus (MV) is hypothesized to enter the host by infecting epithelial cells of the respiratory tract, followed by viremia mediated by infected monocytes. However, neither of these cell types express signaling lymphocyte activation molecule (CD150), which has been identified as the receptor for wild-type MV. We have infected rhesus and cynomolgus macaques with a recombinant MV strain expressing enhanced green fluorescent protein (EGFP); thus bringing together the optimal animal model for measles and a virus that can be detected with unprecedented sensitivity. Blood samples and broncho-alveolar lavages were collected every 3 d, and necropsies were performed upon euthanasia 9 or 15 d after infection. EGFP production by MV-infected cells was visualized macroscopically, in both living and sacrificed animals, and microscopically by confocal microscopy and FACS analysis. At the peak of viremia, EGFP fluorescence was detected in skin, respiratory and digestive tract, but most intensely in all lymphoid tissues. B- and T-lymphocytes expressing CD150 were the major target cells for MV infection. Highest percentages (up to 30%) of infected lymphocytes were detected in lymphoid tissues, and the virus preferentially targeted cells with a memory phenotype. Unexpectedly, circulating monocytes did not sustain productive MV infection. In peripheral tissues, large numbers of MV-infected CD11c+ MHC class-II+ myeloid dendritic cells were detected in conjunction with infected T-lymphocytes, suggesting transmission of MV between these cell types. Fluorescent imaging of MV infection in non-human primates demonstrated a crucial role for lymphocytes and dendritic cells in the pathogenesis of measles and measles-associated immunosuppression.

Cytopathic mechanisms of HIV-1

The human immunodeficiency virus type 1 (HIV-1) has been intensely investigated since its discovery in 1983 as the cause of acquired immune deficiency syndrome (AIDS). With relatively few proteins made by the virus, it is able to accomplish many tasks, with each protein serving multiple functions. The Envelope glycoprotein, composed of the two noncovalently linked subunits, SU (surface glycoprotein) and TM (transmembrane glycoprotein) is largely responsible for host cell recognition and entry respectively. While the roles of the N-terminal residues of TM is well established as a fusion pore and anchor for Env into cell membranes, the role of the C-terminus of the protein is not well understood and is fiercely debated. This review gathers information on TM in an attempt to shed some light on the functional regions of this protein.

Effects of immunosuppressive drugs on HIV infection: implications for solid-organ transplantation

With the advent of highly active antiretroviral therapy (HAART), HIV infection has become a chronic disease. Various end-stage organ failures have now become common co-morbidities and are primary causes of mortality in HIV-infected patients. Solid-organ transplantation therefore has been proposed to these patients, as HIV infection is not anymore considered an absolute contraindication. The initial results of organ transplantation in HIV-infected patients are encouraging with no differences in patient and graft survival compared with non-HIV-infected patients. The use of immunosuppressive drug therapy in HIV-infected patients has so far not shown major detrimental effects, and some drugs in combination with HAART have even demonstrated possible beneficial effects for specific HIV settings. Nevertheless, organ transplantation in HIV-infected patients remains a complex intervention, and more studies will be required to clarify open questions such as long-term effects of drug interactions between antiretroviral and immunosuppressive drugs, outcome of recurrent HCV infection in HIV-infected patients, incidence of graft rejection, or long-term graft and patient survival. In this article, we first review the immunological pathogenesis of HIV infection and the rationale for using immunosuppression combined with HAART. We then discuss the most recent results of solid-organ transplantation in HIV-infected patients.

Plasma levels of soluble urokinase-type plasminogen activator receptor (suPAR) and early mortality risk among patients enrolling for antiretroviral treatment in South Africa

Background

Serum concentrations of soluble urokinase-type plasminogen activator receptor (suPAR) have a strong independent association with HIV-1-related mortality. The practical utility of plasma suPAR in assessing short-term all-cause mortality risk was evaluated in patients with advanced immunodeficiency enrolling in an antiretroviral treatment (ART) programme in South Africa.

Methods

An enzyme-linked immunosorbent assay (ELISA) was used to measure plasma concentrations of suPAR in patients at the time of enrolment to the ART programme. The association between plasma suPAR concentrations, baseline patient characteristics and cohort outcomes after 4 months of ART were determined.

Results

Patients (n = 293, 70% female) had a median age of 33 years and were followed up for a median of 5 months from enrolment. The median CD4 cell count was 47 cells/μl (IQR = 22–72) and 38% of patients had WHO stage 4 disease. 218 (74%) patients remained alive after 4 months of ART; 39 (13%) died and 36 (12%) were lost to the programme for other reasons. Patients who died had significantly higher plasma suPAR concentrations compared to those who either survived (P < 0.01) or left the programme for other reasons (P < 0.043). In multivariate analysis, higher log₁₀ suPAR concentrations were significantly associated with lower CD4 cell counts, WHO clinical stage 4 disease and male sex. In multivariate analysis to identify factors associated with death, log₁₀ suPAR concentration was the most strongly associated variable (P < 0.001). However, examination of sensitivity and specificity characteristics using receiver operating characteristic (ROC) analysis revealed that results from this assay did not have a discriminatory cut-point to provide clinically useful information.

Conclusion

Plasma suPAR concentration was the strongest independent predictor of short-term mortality risk among patients with advanced immunodeficiency enrolling in this ART programme. However, lack of a discriminatory threshold did not permit this marker to be used to triage patients according to short-term mortality risk.

Suppression of HIV-specific T cell activity by lymph node CD25+ regulatory T cells from HIV-infected individuals

CD25(+) CD4(+) FoxP3(+) regulatory T (Treg) cells isolated from the peripheral blood of asymptomatic HIV-infected individuals have been demonstrated to significantly suppress HIV-specific immune responses in vitro. CD25(+) Treg cell suppressor activity in the peripheral blood seems to diminish with progression of HIV disease, and it has been suggested that loss of Treg cells contributes to aberrant immune activation and disease progression. However, phenotypic studies suggest that Treg cells may migrate to, and be maintained or even expanded in, tissue sites of HIV replication. Currently, it is not known whether tissue-associated Treg cells maintain suppressive activity in the context of HIV infection, particularly in individuals with advanced disease. The present study demonstrates that CD25(+) Treg cells isolated from lymph nodes and peripheral blood of HIV(+) subjects, even those with high viral loads and/or low CD4(+) T cell counts, maintain potent suppressive activity against HIV-specific cytolytic T cell function. This activity was better in lymph node as compared with peripheral blood, particularly in patients with high levels of plasma viremia. In addition, the expression of certain CD25(+) Treg-associated markers on CD4(+) T cells isolated from lymph nodes differed significantly from those on CD4(+) T cell subsets isolated from the peripheral blood. These data suggest that CD25(+) Treg cell-mediated suppression of HIV-specific responses continues throughout the course of HIV disease and, because of their particularly potent suppression of HIV-specific CTL activity in lymphoid tissue, may considerably impact the ability to control HIV replication in vivo.

Synonymous substitution rates predict HIV disease progression as a result of underlying replication dynamics

Upon HIV transmission, some patients develop AIDS in only a few months, while others remain disease free for 20 or more years. This variation in the rate of disease progression is poorly understood and has been attributed to host genetics, host immune responses, co-infection, viral genetics, and adaptation. Here, we develop a new “relaxed-clock” phylogenetic method to estimate absolute rates of synonymous and nonsynonymous substitution through time. We identify an unexpected association between the synonymous substitution rate of HIV and disease progression parameters. Since immune activation is the major determinant of HIV disease progression, we propose that this process can also determine viral generation times, by creating favourable conditions for HIV replication. These conclusions may apply more generally to HIV evolution, since we also observed an overall low synonymous substitution rate for HIV-2, which is known to be less pathogenic than HIV-1 and capable of tempering the detrimental effects of immune activation. Humoral immune responses, on the other hand, are the major determinant of nonsynonymous rate changes through time in the envelope gene, and our relaxed-clock estimates support a decrease in selective pressure as a consequence of immune system collapse.

During the clinical course of HIV infection, an asymptomatic phase always precedes the acquired immunodeficiency syndrome (AIDS). The duration of this asymptomatic phase is highly variable among patients and reflects the rate at which the immune system gradually deteriorates. Although humoral and cell-mediated immune responses are mounted against HIV, continuous replication and adaptation allows the virus to escape host immune responses. To gain a better understanding of the role of viral evolution in disease progression, we developed a new computational technique that can estimate changes in the absolute rates of synonymous and nonsynonymous divergence through time from molecular sequences. Using this type of evolutionary inference, we have identified a previously unknown association between the “silent” evolutionary rate of HIV and the rate of disease progression in infected individuals. This finding demonstrates that cellular immune processes, which are already known to determine HIV pathogenesis, also determine viral replication rates and therefore impose important constraints on HIV evolution.

CD4 T-cell count and HIV-1 infection in adults with uncomplicated malaria

BACKGROUND

HIV-1-negative children with malaria have reversible lymphocyte and CD4 count decreases. We assessed the impact of malaria parasitemia on the absolute CD4 count in both HIV-1-infected and non-HIV-infected adults.

METHODS

In Ndola, Zambia, at the health-center level, we treated 327 nonpregnant adults for confirmed, uncomplicated, clinical malaria. We assessed HIV-1 status, CD4 count, and HIV-1 viral load (if HIV-1-infected) at enrollment and at 28 and 45 days after treatment.

RESULTS

After successful antimalarial treatment, the median CD4 count at day 28 of follow-up increased from 468 to 811 cells/microL in HIV-1-negative and from 297 to 447 cells/microL in HIV-1-positive patients (paired t test, P < 0.001 for both). CD4 count increment was inversely correlated with CD4 count at day 0 in both HIV-1-negative (P < 0.001) and HIV-1-positive patients (P = 0.03). After successful treatment, the proportion of patients with CD4 count <200/microL at day 45 decreased from 9.6% to 0% in HIV-1-negative and from 28.7% to 13.2% in HIV-1-positive malaria patients (P < 0.001 for both). In patients with detectable but mostly asymptomatic parasitemia, CD4 count and, if HIV-1-infected, viral load at day 45 of follow-up were similar to those observed at enrollment.

CONCLUSION

Interpretation of absolute CD4 count might be biased during or just after a clinical malaria episode. Therefore, in malaria-endemic areas, before taking any decision on the management of HIV-1-positive individuals, their malaria status should be assessed.

Interactions between schistosomiasis and infection with HIV-1

In many regions of the world, both schistosomiasis and HIV/AIDS are endemic, resulting in patients harbouring co-infections. Because interaction with host CD4(+) T cells is a characteristic of schistosome as well as HIV-1 infections, bi-directional disease effects may be sufficiently different from sequelae caused by either infectious agent alone to warrant alteration of public health approaches in areas of co-endemnicity. Studies published over the past decade provide useful insights into interactions between schistosomiasis and infection with HIV-1, and overall support the hypothesis that special emphasis on treatment of schistosomiasis in populations with elevated prevalence or risk of HIV-1 infection is justified.

HIV and helminth co-infection: is deworming necessary?

We have previously suggested that helminth infections play a major role in the pathogenesis of HIV-1 infection in Africa and other developing areas, due to their profound effects on the host immune system, which make those infected more susceptible to HIV-1 infection and less able to cope with it. Chronic immune activation with a dominant Th2 profile, and anergy, are the hallmarks of chronic helminth infection, and may therefore account for most of these effects. In the present review, we summarize the studies that have addressed these issues and argue that despite some conflicting results, the cumulative immunological and epidemiological evidence is in favour of deworming as a preventive and possible therapeutic measure vis-à-vis HIV-1 infection. We suggest that it should be at least tested on a wider and larger scale than has been done until now, because of its immense potential impact on the still raging AIDS epidemic in developing countries.

Human immunodeficiency virus persistence and production in T-cell development

Human immunodeficiency virus type 1 (HIV-1) replication depends on CD4 and coreceptor expression as well as host factors associated with the activation state of the cell. To determine the impact of the activation stage of thymocytes on the HIV-1 life cycle, we investigated R5 and X4 HIV-1 entry, reverse transcription, and expression in discrete thymocyte subsets at different stages of T-cell development. Early after infection, preferential entry and replication of R5 HIV-1 were predominantly detected in mature CD3(+/hi) CD27(+) thymocytes. Thus, R5 HIV-1 targets the stage of development where thymocytes acquire functional responsiveness, which has important implications for HIV pathogenesis. In contrast, X4 HIV-1 expression and replication were primarily found in immature CD3(-/+/low) CD27(-) CD69(-) thymocytes. HIV-1 proviral burden and virus expression in thymocyte subsets correlated with the expression of the highest levels of the respective coreceptor. R5 and X4 HIV-1 entered and completed reverse transcription in all subsets tested, indicating that the activation state of thymocytes and coreceptor expression are sufficient to support full reverse transcription throughout development. Although R5 HIV-1 is expressed mainly in mature CD3(+/hi) CD27(+) thymocytes, 5.3% of HIV-1-infected immature thymocytes express R5 HIV-1, indicating that potentially latent viral DNA can be established early in T-cell development.

[Immunophenotype of progression to AIDS: deficiency, activation and dysfunction of CD4 and CD8 T-cells]

INTRODUCTION

One key piece of information required when deciding whether to initiate antiretroviral therapy is the risk of AIDS. The aim of this study was to better characterize the baseline immunophenotypic profile of patients with progression to AIDS.

MATERIAL AND METHODS

A cross-sectional analysis of the distribution of functional subpopulations of CD4+ and CD8+ T-lymphocytes in 85 intravenous drug addicts with HIV infection. The values observed on patient enrolment in a prospective study were analyzed. Those patients who progressed and did not progress were compared to the HIV-negative controls. Lymphocyte subpopulations were studied by flow cytometry, including the markers: CD3, CD4, CD7, CD8, CD45RO, CD38, HLA-DR and CD25.

RESULTS

The immunophenotypic profile that precedes progression to AIDS was mainly characterized by an increase in memory (CD45RO) activated cells and total activated CD4+ and CD8+ cells, and by an increase of T CD4+ cells that have loss expression of markers as receptor or the differentiation marker CD7 (CD7-). Patients not meeting laboratory criteria to initiate antiretroviral therapy (> 350 CD4+ T-cells and < 30,000 HIV-ARN-copies/ml) also showed increased levels of CD4+ and CD8+ activation subsets (CD4+CD38+DR+, CD8+CD38+).

DISCUSSION

The fact that immunological activation may contribute to immunological and clinical deterioration of HIV-positive patients might be an additional factor which should be taken into account when deciding whether to initiate antiretroviral therapy.

HIV-1 Matrix Protein p17 Modulatesin VivoPreactivated Murine T-Cell Response and Enhances the Induction of Systemic and Mucosal Immunity Against Intranasally Co-administered Antigens

HIV-1 p17 is a viral cytokine that acts on preactivated, but not on resting, human T cells promoting proliferation, proinflammatory cytokines release and HIV-1 replication, after binding to a cellular receptor (p17R). Here, we demonstrate that p17Rs are expressed on activated murine T cells, which respond to p17 stimulation similarly to their human counterpart. We developed a mouse model of abortive HSV-1 infection to induce T cell activation in vivo. Preactivated cells expressed p17Rs and were highly susceptible to p17 stimulation, which triggered proinflammatory cytokines release and promoted CD4+ T cell survival and expansion. Coculture of in vivo activated splenocytes with macrophages in the presence of p17 further increased their ability to produce IFN-gamma. The presence of macrophages and activated T cells at mucosal sites prompted us to investigate the immunomodulatory activities of p17 in vivo. Intranasal coadministration of p17 with beta-galactosidase (beta-gal) resulted in improved beta-gal specific cellular and humoral immune responses at systemic and mucosal levels. It is well established that HIV-1 replication is driven in an autocrine/paracrine manner by endogenously produced proinflammatory cytokines. Our results highlight the role of p17 in sustaining cellular activation and inflammation, thereby promoting a permissive microenvironment for HIV-1 replication. In addition, p17 is a promising candidate antigen, exhibiting immunomodulatory/adjuvant properties, that need to be exploited in the development of HIV/AIDS vaccines.

Interactions between HIV infection and leprosy: a paradox

Early in the HIV epidemic it was feared that the disease would undermine leprosy control, as has occurred with tuberculosis. It was predicted that patients with leprosy and HIV coinfection would have an increased risk of lepromatous disease and a faster clinical evolution, and that the leprosy would be more difficult to treat. None of these concerns have materialised and the interaction between HIV and Mycobacterium leprae seems to be far more subtle than that between HIV and tuberculosis. We review the epidemiological, clinical, and pathological data relating to leprosy/HIV coinfection. The published epidemiological data are limited in quality but show neither an increased HIV prevalence among leprosy cases nor an alteration in clinical spectrum of leprosy among coinfected patients. Some data suggest that immune-mediated reactions that complicate leprosy occur at a higher frequency in coinfected patients. Leprosy has now been reported presenting as immune reconstitution disease among patients commencing highly active antiretroviral treatment. Histopathological observations reveal a normal spectrum of appearances in biopsies of leprosy lesions from coinfected patients, even among those with advanced immunodeficiency. These observations suggest that cell-mediated immune responses to M leprae are preserved at the site of disease despite evidence that these responses are abrogated systemically, by contrast with tuberculosis, in which the host granulomatous response is impaired by HIV coinfection. We speculate that this paradox may relate to differences between the activation state and rates of cell turnover within leprosy and tuberculosis granulomas that differentially affect the susceptibility of the granulomas to HIV. The interactions between leprosy and HIV have been little studied and further research on the clinical, pathological, and management aspects of this coinfection is warranted.

Pathogenesis of HIV infection: what the virus spares is as important as what it destroys

Upon transmission to a new host, HIV targets CCR5+ CD4+ effector memory T cells, resulting in acute, massive depletion of these cells from mucosal effector sites. This depletion does not initially compromise the regenerative capacity of the immune system because naive and most central memory T cells are spared. Here, we discuss evidence suggesting that frequent activation of these spared cells during the chronic phase of HIV infection supplies mucosal tissues with short-lived CCR5+ CD4+ effector cells that prevent life-threatening infections. This immune activation also facilitates continued viral replication, but infection and killing of target T cells by HIV are selective and the impact on effector-cell lifespan is limited. We propose, however, that persistent activation progressively disrupts the functional organization of the immune system, reducing its regenerative capacity and facilitating viral evolution that leads to loss of the exquisite target cell-sparing selectivity of viral replication, ultimately resulting in AIDS.

Increased TGF-beta, Cbl-b and CTLA-4 levels and immunosuppression in association with chronic immune activation

In this study we investigated the mechanisms mediating T-cell hyporesponsiveness in chronically immune-activated individuals. We analyzed in healthy and persistently helminth-infected individuals the relationship between immune activation and general T-cell hyporesponsiveness, Th3/regulatory T-cell expression, transforming growth factor-beta (TGF-beta) secretion, CTL-associated antigen 4 (CTLA-4) levels, Casitas B-cell lymphoma-b (Cbl-b) (a negative regulator of T-cell activation) levels and phosphorylation of mitogen-activated protein kinases/extracellular signal-regulated kinase (ERK)-1 and -2. We found a very significant increase in plasma levels of TGF-beta and intracellular pools of CTLA-4 and Cbl-b in association with immune activation, which correlates with decreased T-cell responses to anti-CD3 stimulation. We demonstrate that the impaired activity of ERK of peripheral T cells in highly immune-activated individuals is associated with increased levels of CTLA-4 and Cbl-b. Interestingly, in some, but not in all, of these immune-activated individuals, induction of Cbl-b intracellular pools occurs by TGF-beta or CTLA-4 stimulation. We suggest that the higher levels of CTLA-4 and TGF-beta, both involved in the induction of Cbl-b, point at potential mechanisms underlying general and antigen-specific immune hyporesponsiveness in chronically infected individuals.

Structured intermittent interruption of chronic HIV infection treatment with highly active antiretroviral therapy: effects on leptin and TNF-alpha

The changes in nutritional parameters and adipocytokines after structured intermittent interruption of highly active antiretroviral treatment of patients with chronic HIV infection are analyzed. Twenty-seven patients with chronic HIV infection (median CD4+ T cell count/microl: nadir, 394; at the beginning of structured interruptions, 1041; HIV viral load: nadir, 41,521 copies/ml; at the beginning of structured interruptions <50 copies/ml; median time of previous treatment: 60 months) were evaluated during three cycles of intermittent interruptions of therapy (8 weeks on/4 weeks off). CD4+ T cell count, HIV viral load, anthropometric measures, and serum concentrations of triglycerides, cholesterol, leptin, and tumor necrosis factor and its soluble receptors I and II were determined. After the three cycles of intermittent interruptions of therapy, no significant differences in CD4+ T cell count/microl, viral load, or serum concentrations of cholesterol or triglycerides with reference to baseline values were found. A near-significant higher fatty mass (skinfold thicknesses, at the end, 121 mm, at the beginning, 100 mm, p = 0.100), combined with a significant increase of concentration of leptin (1.5 vs. 4.7 ng/ml, p = 0,044), as well as a decrease in serum concentrations of soluble receptors of tumor necrosis factor (TNFRI, 104 vs. 73 pg/ml, p = 0.022; TNFRII 253 vs. 195 pg/ml, p = 0.098) were detected. Structured intermittent interruption of highly active antiretroviral treatment of patients with chronic HIV infection induces a valuable positive modification in markers of lipid turnover and adipose tissue mass.

The role of FAS to ezrin association in FAS-mediated apoptosis

The acquisition of a cell polarity is a crucial requirement for a number of cellular functions, including apoptosis. Cell polarization is an actin cytoskeleton-driven process, through a connection between actin and an increasing number of membrane proteins. The major actors in this connection are ezrin, radixin and moesin, a family of proteins with a high level of homology. Their structure includes an epitope that links to membrane proteins and the other that binds to the actin molecule. In this review we discuss recent data showing that the Fas linkage to the actin cytoskeleton is ezrin mediated and it is an essential requirement for susceptibility to the Fas-mediated apoptosis. The ezrin region responsible of Fas binding consists of 18 aminoacids mapped on the median lobe of the ezrin FERM domain. This binding is specific and of key importance in the control of cell homeostasis. Moreover, Fas-ezrin co-localization, ezrin phosphorylation and early acquisition of susceptibility to Fas-mediated apoptosis, may have a role in some human diseases in which programmed cell death seems to be a central pathogenetic mechanism, such as AIDS.

HIV replication elicits little cytopathic effects in vivo: Analysis of surrogate markers for virus production, cytotoxic T cell response and infected cell death

Several potential mechanisms for viral destruction of HIV-infected cells have been described. The hypothesis was examined that if HIV were cytopathic, a positive relation between the in vivo virus production or CTL activity and infected cell death should be observed. In a regression analysis no significant relation was found between surrogate markers for in vivo virus production or the virus-specific CTL response and death rates of productively infected cells. In a subgroup of patients the hypothesis is rejected that HIV replication elicits a large (R(2) > 0.25) cytopathic effect (P < 0.05, N = 36). It is concluded that HIV replication elicits little cytopathic effect in productively infected cells and that CD4(+) T lymphocytes are eroded by other mechanisms.

Musculoskeletal and autoimmune manifestations of HIV, syphilis and tuberculosis

PURPOSE OF REVIEW

The HIV pandemic continues to increase at an alarming rate, and is the leading cause of death worldwide from a single pathogen. The number of HIV-1-infected individuals currently exceeds 40 million, the majority of whom live in the developing countries of Asia, sub-Saharan Africa and south America. In the past 5 years, there has concurrently been an increase in the reported cases of tuberculosis and primary and secondary syphilis. This review addresses the musculoskeletal and autoimmune manifestations associated with HIV, syphilis and tuberculosis infections or their treatments.

RECENT FINDINGS

During HIV infection the immune system becomes dysfunctional because of the coexistence of immunodeficiency and immune hyperactivity, and a disregulated production or activity of cytokines. Some of these mechanisms explain the development of rheumatic manifestations associated with HIV infection. Highly active antiretroviral therapy changes the course of HIV infection and the spectrum of the HIV-associated rheumatic manifestations. New syndromes such as the immune reconstitution inflammatory syndrome have emerged. HIV, tuberculosis and syphilis infections offer special epidemiological, clinical, and therapeutic challenges.

SUMMARY

These observations highlight the complexity and multiplicity of the interactions between the pathogen and host that could result in the development of rheumatic manifestations.

Bangkok: the end of broken promises? XV International AIDS Conference, 2004

The global community has again failed to significantly confront the AIDS crisis. In the context of a worsening HIV pandemic, the conference highlighted the shortfall in funding, the soaring infection rate in Asia, the need to integrate prevention and treatment and the difficulties in coordinating a global response. To overcome AIDS, the global community must put aside ideology and honour its commitments.

Stage-specific effects of Plasmodium falciparum-derived hemozoin on blood mononuclear cell TNF-alpha regulation and viral replication

BACKGROUND

The molecular immunological interactions between HIV and malaria are largely undefined. Since tumor necrosis factor (TNF)-alpha is elevated during acute malaria and increases with HIV-1 disease progression, TNF-alpha production may be an important mediator for interactions between malaria and HIV-1.

METHODS

To examine the stage-specific immunological interactions between HIV and malaria, peripheral blood mononuclear cells (PBMC) and CD14 cells were isolated and cultured from rhesus macaques at different stages of SIV infection. Cultures were stimulated with lipopolysaccharide (LPS) and interferon (IFN)-gamma in the presence of Plasmodium falciparum-derived hemozoin (Hz) or synthetic Hz (sHz). TNF-alpha transcripts and soluble protein were examined by real time reverse transcription-PCR and ELISA, respectively. The effects of Hz on viral replication were determined by measurement of p27 antigen with varying concentrations of TNF-alpha neutralizing antibodies.

RESULTS

Hz and sHz significantly increased LPS- and IFN-gamma-induced TNF-alpha protein and transcripts in PBMC from animals with late stage SIV infection (i.e., AIDS). Hz and sHz also induced high levels of sustained TNF-alpha transcripts in PBMC from the AIDS group. During the late stage of disease, CD14 cells were the primary source of TNF-alpha production. Stimulation of PBMC with Hz and sHz significantly increased viral replication that was dose-dependently reduced by the addition of TNF-alpha neutralizing antibodies.

CONCLUSIONS

Hz promotes high levels of TNF-alpha production from PBMC during AIDS and increases viral replication in SIV-infected animals.

Influence of RANTES, SDF-1 and TGF-beta levels on the value of interleukin-7 as a predictor of virological response in HIV-1-infected patients receiving double boosted protease inhibitor-based therapy

OBJECTIVES

Interleukin-7 (IL-7), RANTES (regulated on activation, normal T cell expressed and secreted), stromal cell-derived factor-1 (SDF-1) and transforming growth factor-beta (TGF-beta) appear to share certain biological properties in vitro and all are involved in HIV-1 disease progression. Our earlier observations indicated that IL-7 levels decrease upon CD4 T-cell recovery and represent a new, independent predictor of virological response. Here, we examine associations among circulating levels of IL-7, RANTES, SDF-1 and TGF-beta in hopes of gaining insight into their contribution to the predictive value of IL-7.

METHODS

Levels of IL-7, RANTES, SDF-1 and TGF-beta, and immune and viral parameters were assessed in HIV-1-infected patients.

RESULTS

Cross-sectional (n=148) and longitudinal (n=36) analyses showed that levels of IL-7, but not RANTES, SDF-1 or TGF-beta, were increased in HIV-1-infected adults compared with those of healthy controls. In the cross-sectional study, levels of IL-7 were correlated with RANTES (r=0.31, P=0.002) and TGF-beta (r=0.53, P<0.001) but not with SDF-1 (r=0.12, P=0.22), and these associations were more pronounced in patients with CD4 T-cell counts >200 cells/microL. In contrast to IL-7, levels of RANTES, SDF-1 and TGF-beta were not correlated with CD4 T-cell counts. Longitudinal analysis revealed a marked decline in IL-7 levels accompanied by an increase in CD4 T-cell count following antiretroviral therapy (ART), but no changes in RANTES, SDF-1 or TGF-beta levels. Multivariate regression analysis showed no influence of baseline RANTES, SDF-1 or TGF-beta levels on the value of IL-7 as a predictor of virological response at 48 weeks.

CONCLUSIONS

Collectively, these results indicate that changes in IL-7 levels did not induce changes in RANTES, SDF-1 or TGF-beta. Furthermore, they indicate that RANTES, SDF-1 or TGF-beta levels do not explain the predictor value of IL-7 in patients receiving ART.

Serum Neopterin, an Immune Activation Marker, Independently Predicts Disease Progression in Advanced HIV-1 Infection

BACKGROUND

CD4+ T lymphocyte (CD4) counts and plasma human immunodeficiency virus (HIV) type 1 RNA concentrations predict clinical outcome in HIV-1 infection. Our objective was to assess the independent prognostic value for disease progression of soluble markers of immune system activation.

METHODS

This retrospective marker-validation study utilized previously obtained clinical and laboratory data, including CD4+ cell counts, and made use of stored frozen serum samples to assay for levels of beta2-microglobulin, neopterin, endogenous interferon, triglycerides, interleukin-6, soluble tumor necrosis factor- alpha receptor II, and HIV-1 RNA, and to determine HIV genotypic reverse-transcriptase inhibitor resistance. The 152 patients who participated in this study represented a subsample of participants in AIDS Clinical Trials Group (ACTG) 116B/117, a randomized trial that demonstrated the clinical benefit of didanosine over zidovudine monotherapy in persons with advanced HIV-1 infection. Marker data were analyzed in relation to protocol-defined clinical disease progression, using Cox proportional hazards models.

RESULTS

The median duration of follow-up was 344 days. Elevated baseline values for neopterin (P=.0009), endogenous interferon (P=.00039) and interleukin-6 (P=.0007) were each associated with greater subsequent risk of clinical disease progression. In a head-to-head comparison that was adjusted for CD4+ cell count (P=.0165) and HIV-1 RNA level (P=.1220), we found that elevated values for neopterin (P=.0002) and, to a lesser extent, endogenous interferon (P=.0053) were the strongest predictors of increased risk of clinical disease progression 6 months later.

CONCLUSIONS

Soluble markers of immune activation add prognostic information to CD4 counts and viral load for risk of disease progression in advanced HIV-1 infection. The robust performance of neopterin, an inexpensive and reliably measured serum marker, supports its potential suitability for patient monitoring, particularly in resource-limited settings.

Predictive value of anti-cell and anti-human immunodeficiency virus (HIV) humoral responses in HIV-1-exposed seronegative cohorts of European and Asian origin

Unconventional immune responses have been demonstrated in individuals who, despite repeated exposure to human immunodeficiency virus (HIV) infection, remain seronegative. As environmental exposure to pathogens and genetic background may modulate immune responses differentially, one Italian and two Asian populations of HIV-1-exposed seronegative individuals were studied. In serum samples from each group, IgG to CCR5, IgG to CD4 and IgA to gp41 were measured, which were previously described as markers of unconventional immunity in HIV-exposed seronegative Caucasians. Given the importance of conformational epitopes in virus-cell interactions, IgG to CD4-gp120 complex was also measured. It was found that markers of HIV exposure were present in all populations studied. HIV-specific humoral responses (IgA to gp41 and IgG to CD4-gp120 complex) were extremely significant predictors of HIV exposure (P<0.0001 in both cases), whereas the predictive values of anti-cell antibodies (anti-CCR5 and anti-CD4) varied between populations. Evidence is provided for the correlation of these differences with route of exposure to HIV and level of natural antibodies to cross-reactive microbial antigens. In conclusion, exposed seronegative individuals of ethnically different origins display similar signs of HIV-dependent unconventional immunity. A specific relevance must be attributed to different innate and acquired factors.

Chronic immune activation associated with chronic helminthic and human immunodeficiency virus infections: role of hyporesponsiveness and anergy

Chronic immune activation is one of the hallmarks of human immunodeficiency virus (HIV) infection. It is present also, with very similar characteristics, in very large human populations infested with helminthic infections. We have tried to review the studies addressing the changes in the immune profiles and responses of hosts infected with either one of these two chronic infections. Not surprisingly, several of the immune derangements and impairments seen in HIV infection, and considered by many to be the "specific" effects of HIV, can be found in helminth-infected but HIV-noninfected individuals and can thus be accounted for by the chronic immune activation itself. A less appreciated element in chronic immune activation is the immune suppression and anergy which it may generate. Both HIV and helminth infections represent this aspect in a very wide and illustrative way. Different degrees of anergy and immune hyporesponsiveness are present in these infections and probably have far-reaching effects on the ability of the host to cope with these and other infections. Furthermore, they may have important practical implications, especially with regard to protective vaccinations against AIDS, for populations chronically infected with helminths and therefore widely anergic. The current knowledge of the mechanisms responsible for the generation of anergy by chronic immune activation is thoroughly reviewed.

Replication of M-tropic HIV-1 in Activated Human Intestinal Lamina Propria Lymphocytes Is the Main Reason for Increased Virus Load in the Intestinal Mucosa

The gastrointestinal tract is the site of early abundant HIV replication and associated marked CD4 T-cell depletion. The aim of this study was to characterize the basis for the increased HIV replication in this compartment. Isolated mononuclear cells of the peripheral blood (PBMCs), the intestinal lamina propria (LPMCs), and purified gut lamina propria CD4 T-cell subpopulations (LP T cells) were isolated, phenotypically characterized, and infected in vitro with 2 different HIV-1 strains. T-cell subpopulations were analyzed by fluorescence-activated cell sorter. HIV-1 core protein p24 was determined in supernatants after in vitro infection. Furthermore the effect of T-cell stimulation on the replication of M- and T-tropic HIV strains was studied. In vitro replication of HIV-1 was significantly increased in CD69 compared with CD69 CD4 LP T cells, while there was no difference between CD103 and CD103 CD4 LP T cells. Experimental stimulation of LPMCs, which mimics activation by intestinal pathogens frequently present in the bowel of HIV-infected patients, further dramatically enhances HIV replication (24.5-fold) compared with nonstimulated LPMCs. M-tropic HIV-1 showed a preferential replication in LPMCs, while T-tropic HIV-1 strain showed a preferential replication in PBMCs. Thus, the elevated activation state of target cells in the intestine and not the expression of the homing marker CD103 is directly linked to massive HIV production.

Stimulation of toll-like receptor 2 in mononuclear cells from HIV-infected patients induces chemokine responses: possible pathogenic consequences

Toll-like receptor 2 (TLR2) stimulation in monocytes may contribute to enhanced inflammation and viral replication in HIV infection. In the present study we examined if TLR2 stimulation could modulate chemokine responses in peripheral blood mononuclear cells (PBMC) from HIV-infected patients and healthy controls. Our main findings were, with similar qualitative patterns in both healthy controls and HIV-infected patients: (1) TLR2 stimulation induced up-regulation of several chemokines at the mRNA level as well as increased protein levels of macrophage inflammatory protein (MIP)-1alpha, interleukin (IL)-8 and regulated on activation, normal T cell expressed and secreted (RANTES); (2) TLR2 stimulation induced enhanced protein expression of CCR5 (a receptor for MIP-1alpha and RANTES) on monocytes; (3) In vitro stimulation with RANTES induced release of MIP-1alpha, MCP-1, IL-8 and interferon-gamma from PBMC. While increased levels of beta-chemokines possibly have antiviral effects, TLR2 stimulation may also promote a chemokine-driven inflammatory loop, potentially contributing to the immunopathogenesis of HIV infection.

Coevolution of RANTES sensitivity and mode of CCR5 receptor use by human immunodeficiency virus type 1 of the R5 phenotype

The evolution of human immunodeficiency virus type 1 (HIV-1) coreceptor use has been described as the acquisition of CXCR4 use linked to accelerated disease progression. However, CXCR4-using virus can be isolated only from approximately one-half of individuals with progressive HIV-1 disease. The other half continue to yield only CCR5-using viruses (R5 phenotype) throughout the course of disease. In the present work, the use of receptor chimeras between CCR5 and CXCR4 allowed us to study the evolution of HIV-1 with the R5 phenotype, which was not revealed by studies of wild-type coreceptor use. All together, 246 isolates (173 with the R5 phenotype) from 31 individuals were tested for their ability to infect cells through receptor chimeras. R5(narrow) virus was able to use only wild-type CCR5, whereas R5(broad(1)) to R5(broad(3)) viruses were able to use one to three chimeric receptors, respectively. Broad use of chimeric receptors was interpreted as an increased flexibility in the mode of receptor use. R5(broad) isolates showed higher infectivity in cells expressing wild-type CCR5 than R5(narrow) isolates. Also, the increased flexibility of R5(broad) isolates was concomitant with a lower sensitivity to inhibition by the CC chemokine RANTES. Our results indicate a close relationship between HIV-1 phenotypic changes and the pathogenic process, since the mode and efficiency of CCR5 use as well as the decrease in the RANTES sensitivities of isolated viruses are significantly correlated with CD4(+)-T-cell decline in a patient. One possible explanation is that ligand competition at the CCR5 receptor or changed CCR5 availability may shape the outcome of HIV-1 infection.

CD25(+)CD4(+) regulatory T cells from the peripheral blood of asymptomatic HIV-infected individuals regulate CD4(+) and CD8(+) HIV-specific T cell immune responses in vitro and are associated with favorable clinical markers of disease status

Human immunodeficiency virus (HIV) disease is associated with loss of CD4⁺ T cells, chronic immune activation, and progressive immune dysfunction. HIV-specific responses, particularly those of CD4⁺ T cells, become impaired early after infection, before the loss of responses directed against other antigens; the basis for this diminution has not been elucidated fully. The potential role of CD25⁺CD4⁺ regulatory T cells (T reg cells), previously shown to inhibit immune responses directed against numerous pathogens, as suppressors of HIV-specific T cell responses was investigated. In the majority of healthy HIV-infected individuals, CD25⁺CD4⁺ T cells significantly suppressed cellular proliferation and cytokine production by CD4⁺ and CD8⁺ T cells in response to HIV antigens/peptides in vitro; these effects were cell contact dependent and IL-10 and TGF-β independent. Individuals with strong HIV-specific CD25⁺ T reg cell function in vitro had significantly lower levels of plasma viremia and higher CD4⁺: CD8⁺ T cell ratios than did those individuals in whom this activity could not be detected. These in vitro data suggest that CD25⁺CD4⁺ T reg cells may contribute to the diminution of HIV-specific T cell immune responses in vivo in the early stages of HIV disease.

Increased Expression of Toll-Like Receptor 2 on Monocytes in HIV Infection: Possible Roles in Inflammation and Viral Replication

BACKGROUND

Toll-like receptors (TLRs) are key pattern-recognition receptors of the innate immune system, but their role in human immunodeficiency virus (HIV) infection is largely unknown.

METHODS

In the present study, we examined the expression of TLR2 and TLR4 on monocytes from 48 HIV-infected patients and 21 healthy control subjects by flow cytometry.

RESULTS

We found that freshly isolated monocytes from HIV-infected patients displayed enhanced expression of TLR2 but not TLR4, that TLR2 expression on the surface of monocytes was significantly increased upon stimulation of HIV type 1 envelope protein gp120, and that TLR2 stimulation in HIV-infected patients induced increased viral replication and TNF- alpha response.

CONCLUSION

Our findings suggest potential roles for TLR2 in chronic immune activation and viral replication in HIV infection.

Insertion of host-derived costimulatory molecules CD80 (B7.1) and CD86 (B7.2) into human immunodeficiency virus type 1 affects the virus life cycle

Human immunodeficiency virus type 1 (HIV-1) carries virus-encoded and host-derived proteins. Recent advances in the functional characterization of host molecules inserted into mature virus particles have revealed that HIV-1 biology is influenced by the acquisition of host cell membrane components. The CD28/B7 receptor/ligand system is considered one of the fundamental elements of the normal immune response. Two major cell types that harbor HIV-1 in vivo, i.e., monocytes/macrophages and CD4+ T cells, express the costimulatory molecules CD80 (B7.1) and CD86 (B7.2). We investigated whether CD80 and CD86 are efficiently acquired by HIV-1, and if so, whether these host-encoded molecules can contribute to the virus life cycle. Here we provide the first evidence that the insertion of CD80 and CD86 into HIV-1 increases virus infectivity by facilitating the attachment and entry process due to interactions with their two natural ligands, CD28 and CTLA-4. Moreover, we demonstrate that NF-kappaB is induced by CD80- and CD86-bearing virions when they are combined with the engagement of the T-cell receptor/CD3 complex, an event that is inhibited upon surface expression of CTLA-4. Finally, both CD80 and CD86 were found to be efficiently incorporated into R5- and X4-tropic field strains of HIV-1 expanded in cytokine-treated macrophages. Thus, besides direct interactions between the virus envelope glycoproteins and cell surface constituents, such as CD4 and some specific chemokine coreceptors, HIV-1 may attach to target cells via interactions between cell-derived molecules incorporated into virions and their natural ligands. These findings support the theory that HIV-1-associated host proteins alter virus-host dynamics.

Leishmania infantum promotes replication of HIV type 1 in human lymphoid tissue cultured ex vivo by inducing secretion of the proinflammatory cytokines TNF-alpha and IL-1 alpha

Parasitic infections such as leishmaniasis can modulate the life cycle of HIV-1 and disease progression. Coinfection with HIV-1 and Leishmania has emerged as a serious threat in countries where both pathogenic agents are widespread. Although there are numerous clinical reports illustrating the cofactor role played by Leishmania in HIV-1-infected patients, there is still no information on the contribution of Leishmania to the biology of HIV-1 in human lymphoid tissue that is considered a major in vivo site of virus production. In this study we explored the modulatory effect of Leishmania on the process of HIV-1 infection using ex vivo cultured human tonsillar tissue. We found that the protozoan parasite Leishmania enhances both HIV-1 transcription and virus production after infection of human tonsillar tissue infected ex vivo with viral strains bearing various coreceptor usage profiles. Studies conducted with pentoxifylline and neutralizing Abs revealed that the Leishmania-mediated increase in HIV-1 production was linked to a higher production of TNF-alpha and IL-1alpha. Our findings help to unravel the molecular mechanism(s) through which the two microorganisms interact and provide information that may be useful for the design of more effective therapeutic strategies aimed at controlling disease progression in persons dually infected with HIV-1 and Leishmania. This work also indicates that histocultures of human lymphoid tissue infected by both pathogens represent an ideal experimental cell system to dissect interactions occurring between HIV-1 and an opportunist pathogen in a human microenvironment that approximates conditions prevailing under physiological situations.

Inhibition of herpesvirus-induced HIV-1 replication by cyclopentenone prostaglandins: role of IkappaB kinase (IKK)

OBJECTIVES

Herpes simplex virus (HSV) infections have been associated with reactivation of HIV-1 replication and increases of HIV-1-load in plasma of co-infected individuals. The present authors have previously reported that in epithelial cells HSV-1 induces the IkappaB-kinase (IKK) causing persistent activation of NF-kappaB, a critical regulator of HIV-1 replication. The present study was performed to investigate whether HSV-1-infection could induce IKK-mediated NF-kappaB activation and enhance HIV-1 expression in human T cells, and to analyze the effect of the IKK-inhibitor prostaglandin A1 (PGA1) and other prostanoids on the NF-kappaB-mediated HSV-HIV interaction.

DESIGN AND METHODS

Induction of IKK and NF-kappaB activity was determined in lymphoblastoid Jurkat cells and HIV-1 chronically-infected H9 and ACH-2 cells by kinase assay and electrophoretic mobility shift assay, respectively. The effect of HSV-1 and different prostanoids on HIV-1 expression and replication was determined in Jurkat cells transfected with HIV-1-LTR-driven reporter genes, and in H9 and ACH-2 cells by p24-antigen level evaluation. The role of NF-kappaB in HSV-1-induced HIV-1 expression was investigated by using the IkappaBalpha dominant-negative IkappaBalpha-AA in co-transfection experiments.

RESULTS

In human T lymphoblastoid cells HSV-1 potently induces IKK activity, causing a persistent induction of NF-kappaB. HSV-1-induced IKK and NF-kappaB function results in transactivation of HIV-1-LTR-regulated genes and induction of HIV-1 replication in chronically-infected T cells. The cyclopentenone PGA1 inhibits HSV-1-induced IKK and NF-kappaB activities, blocking HIV-1-LTR-driven expression and preventing HSV-1-induced HIV-1 replication in co-infected cells.

CONCLUSIONS

The results indicate that IKK is a key factor in triggering HSV-1-induced HIV-1 transcription in chronically-infected cells and identify cyclopentenone prostanoids as potent inhibitors of HSV-1-induced HIV-1 reactivation.

Effects of potent antiretroviral therapy on the immune activation marker soluble CD27 in patients infected with HIV-1 subtypes A-D

HIV-1 genetic subtypes might have a different impact on disease progression and response to antiretroviral therapy (ART). Few data are available on the immune activation profile in patients with different HIV-1 subtypes. We have tested by ELISA the plasma levels of an immune activation marker, soluble CD27 (sCD27), in a cohort of 64 patients infected with HIV-1 subtypes A-D, at baseline and after 1 year of virologically successful ART. Plasma sCD27 was significantly higher in the whole HIV-1-infected population as compared to healthy subjects [522 U/ml (188-1,307) vs. 285 U/ml (174-397), P < 0.001]. Among the four different HIV-1 subtypes, patients with subtype C virus had significantly higher plasma sCD27 [684 U/ml, (188-1228)] as compared to patients with subtype A [428 U/ml (247-1307), P < 0.05] and B [454 (211-925), P < 0.05]. After 1 year of ART, plasma sCD27 significantly decreased in all groups but patients with subtype C viruses had the largest reduction of sCD27 from baseline. The data indicate that a similar immune activation profile is present in patients infected with HIV-1 subtypes A, B, and D and that in presence of successful ART these subtypes respond similarly in terms of immune activation. Intriguingly, subtype C infection seems to be associated with higher levels of plasma sCD27, suggesting that HIV-1 genetic subtype C may have a different impact on disease outcome and response to therapy.

AIDS in Africa: the impact of coinfections on the pathogenesis of HIV-1 infection

The intimate relationship between the HIV-1 life-cycle and the activation state of cells supporting viral replication results in a dynamic interaction between coinfections and HIV-1 replication in dually infected people. The immunologic impact of recurrent coinfections has the potential to increase viral replication, viral genotypic heterogeneity and CD4 T lymphocyte loss, leading to accelerated decline in immune function, reduced survival and increased HIV-1 transmission risk. These effects may play a particularly significant role in the HIV-1 epidemic in sub-Saharan Africa. The mechanisms underlying these effects on virus-host dynamics are reviewed and data describing the impact of tuberculosis, malaria, schistosomiasis and genital ulceration on HIV-1 infection are presented.

Necrotizing granulomatous vasculitis in advanced HIV infection

We describe the first case of granulomatous necrotizing vasculitis not restricted to the central nervous system in an HIV-infected patient. No mycobacteria or drugs potentially associated with granuloma formation were involved in this patient, suggesting that the cause of this vasculitis was probably autoimmune. The development of granulomatous vascular inflammation in this patient with less than 200 CD4 cells/microl might have been due to immune overactivation. After starting potent antiretroviral therapy a profound immune deactivation was observed and the vasculitis did not relapse.

Assessment of thymic activity in human immunodeficiency virus-negative and -positive adolescents by real-time PCR quantitation of T-cell receptor rearrangement excision circles

Circular DNA molecules known as T-cell receptor rearrangement excision circles (TREC) arise during T-cell development and are present in cells that have recently emigrated from the thymus. In cross-sectional studies, the number of peripheral blood lymphocytes bearing TREC decreases with age, consistent with an anatomically demonstrated loss of thymic epithelial tissue. TREC numbers increase following hematopoietic stem cell transplantation and during therapy for human immunodeficiency virus (HIV) infection. Quantitation of TREC has therefore been proposed as a parameter of thymic activity. In this study, we used real-time PCR to quantify TREC in peripheral blood samples obtained longitudinally from HIV-seronegative adolescents. TREC values in peripheral blood T cells were very stable throughout adolescence, once thought to be a time of rapid involution of the thymus. In addition, in a cross-sectional analysis, we examined TREC values in a cohort of HIV-positive adolescents and found evidence of ongoing thymopoiesis in perinatally infected individuals, despite lifelong infection. These data demonstrate the utility of TREC assessment in adolescents and that HIV infection does not uniformly result in accelerated thymic involution in childhood.

Modeling the effects of vaccination on chronically infected HIV-positive patients

T-cell activation plays a critical role in the initiation and propagation of HIV-1 infection and yet transient activation of the immune system is a normal response to immunization. While it is now considered wise to vaccinate HIV-1-positive patients, it is crucial to anticipate any lasting effects of vaccination on plasma HIV-1 RNA levels and on infected T-cell populations. We extend a simple dynamic model of HIV infection to include T-cell activation by vaccination. We show that the model can reproduce many but not all of the features of the post-tetanus immunization rise in viral load observed and reported on by Stanley et al. in 1966 ( 334:1222-1230). Amplitudes and approximate timing of postimmunization peak viral loads were matched in 10 of 12 cases; in patients with double postimmunization peaks of nearly equal amplitude the later peaks were matched. Furthermore, our simulations suggest that productively infected cell populations track postvaccination increases in plasma viral load, rising and falling in concert over a period of about 4 weeks, whereas chronically infected cells peak later and remain elevated over baseline levels for up to 6 weeks postvaccination.

Attenuated signaling associated with immune activation in HIV-1-infected individuals

Chronic immune activation is associated with impaired signal transduction. Since such activation is commonly found during HIV-1 infection, we studied cellular responses to non-specific T-cell receptor stimulation of PBMC obtained from 20 HIV-1 non-infected individuals and 23 highly or partially immune activated HIV-1 infected individuals. PBMC proliferation and ERK-1/2 phosphorylation following anti-CD3 stimulation, and constitutive levels of Cbl-b, were determined. Increased levels of Cbl-b, decreased proliferation, and lower ERK-1/2 phosphorylation were found in PBMC of highly immune activated HIV-1 infected individuals. The elevated expression of Cbl-b and impaired phosphorylation of ERK-1/2 associated with immune activation probably contribute to the attenuated proliferative and cellular responses characteristic of HIV-1 infection. Therefore, targeting immune negative modulators, such as Cbl-b, may serve as a novel approach for controlling HIV-1 disease progression.

Immune activation and induction of HIV-1 replication within CD14 macrophages during acute Plasmodium falciparum malaria coinfection

OBJECTIVES

To determine the impact of Plasmodium falciparum malaria coinfection and its treatment on cellular reservoirs of viral replication in HIV-1-infected persons and to relate this to changes in systemic immune activation.

METHODS

Plasma samples were obtained from HIV-1-infected individuals (n = 10) at diagnosis of acute malaria, 4 weeks after parasite clearance and from HIV-infected aparasitemic controls (n = 10). Immunomagnetic HIV-1 capture analysis was used to determine the cellular origin of cell-free virus particles present in all 30 plasma samples and indices of immune activation were measured using enzyme-linked immunosorbent assays.

RESULTS

Compared with controls, the detectable proportion of HIV-1 particles derived from CD14 macrophages and CD26 lymphocytes was increased in persons with acute malaria coinfection and correlated with markedly increased plasma concentrations of both proinflammatory cytokines and soluble markers of macrophage and lymphocyte activation. Parasite clearance following treatment with antimalarial drugs resulted in decreased detection of HIV-1 particles derived from the CD14 macrophage cell subset and correlated with a marked diminution in systemic immune activation.

CONCLUSIONS

Acute P. falciparum malaria coinfection impacts virus-host dynamics in HIV-1-infected persons at the cellular level, notably showing a reversible induction of HIV-1 replication in CD14 macrophages that is associated with changes in immune activation.

Tuberculosis unleashed: the impact of human immunodeficiency virus infection on the host granulomatous response to Mycobacterium tuberculosis

The granuloma plays a critical role in the host immune response to Mycobacterium tuberculosis, containing the organism and confining it in a latent state in most infected individuals. Indeed, approximately one-third of the world's population has latent M. tuberculosis infection. However, over the past decade, the human immunodeficiency virus type 1 (HIV-1) pandemic has profoundly affected the incidence and clinicopathological features of tuberculosis. This review examines the immunological mechanisms whereby HIV-1 impairs the establishment, maintenance and function of the tuberculous granuloma.