T cell activation and disease severity in HIV infection

Impact of actin polymerization and filopodia formation on herpes simplex virus entry in epithelial, neuronal, and T lymphocyte cells

Herpes simplex virus type 1 (HSV-1) has been known as a common viral pathogen that can infect several parts of the body, leading to various clinical manifestations. According to this diverse manifestation, HSV-1 infection in many cell types was demonstrated. Besides the HSV-1 cell tropism, e.g., fibroblast, epithelial, mucosal cells, and neurons, HSV-1 infections can occur in human T lymphocyte cells, especially in activated T cells. In addition, several studies found that actin polymerization and filopodia formation support HSV-1 infection in diverse cell types. Hence, the goal of this review is to explore the mechanism of HSV-1 infection in various types of cells involving filopodia formation and highlight potential future directions for HSV-1 entry-related research. Moreover, this review covers several strategies for possible anti-HSV drugs focused on the entry step, offering insights into potential therapeutic interventions.

Human Pegivirus Type 1: A Common Human Virus That Is Beneficial in Immune-Mediated Disease?

Two groups identified a novel human flavivirus in the mid-1990s. One group named the virus hepatitis G virus (HGV) and the other named it GB Virus type C (GBV-C). Sequence analyses found these two isolates to be the same virus, and subsequent studies found that the virus does not cause hepatitis despite sharing genome organization with hepatitis C virus. Although HGV/GBV-C infection is common and may cause persistent infection in humans, the virus does not appear to directly cause any other known disease state. Thus, the virus was renamed “human pegivirus 1” (HPgV-1) for “persistent G” virus. HPgV-1 is found primarily in lymphocytes and not hepatocytes, and several studies found HPgV-1 infection associated with prolonged survival in people living with HIV. Co-infection of human lymphocytes with HPgV-1 and HIV inhibits HIV replication. Although three viral proteins directly inhibit HIV replication in vitro, the major effects of HPgV-1 leading to reduced HIV-related mortality appear to result from a global reduction in immune activation. HPgV-1 specifically interferes with T cell receptor signaling (TCR) by reducing proximal activation of the lymphocyte specific Src kinase LCK. Although TCR signaling is reduced, T cell activation is not abolished and with sufficient stimulus, T cell functions are enabled. Consequently, HPgV-1 is not associated with immune suppression. The HPgV-1 immunomodulatory effects are associated with beneficial outcomes in other diseases including Ebola virus infection and possibly graft-versus-host-disease following stem cell transplantation. Better understanding of HPgV-1 immune escape and mechanisms of inflammation may identify novel therapies for immune-based diseases.

Actin Polymerization Is Required for Filopodia Formation Supporting HSV-1 Entry into Activated T Cells

Enhanced HSV-1 production is found in activated T-lymphocytes, but the mechanism is still unknown. In this paper, the HSV-1 entry step in CD3⁺CD4^-CD8^-Jurkat T lymphocytes was investigated. Observation under electron microscopy revealed the level of filopodia formation on the surface of activated Jurkat cells was significantly higher than that of non-activated Jurkat cells especially after adding HSV-1 for 15 min. A significant increase of actin protein was demonstrated in HSV-1 infected, activated Jurkat cells compared to HSV-1 infected, non-activated Jurkat cells. After the cells were treated with 2.5 and 5 µg/mL cytochalasin D, an inhibitor of actin polymerization that causes depolymerization of actin's filamentous form, the actin protein was decreased significantly, resulting in an absence of filopodia formation. In summary, this is the first study revealing that HSV-1 induced filopodia formation through actin polymerization in activated T cells similar to epithelial, mucosal and neuronal cells. This phenomenon supported the virus entry resulting to increased yield of HSV-1 production.

Circulating (1→3)-β-D-glucan Is Associated With Immune Activation During Human Immunodeficiency Virus Infection

BACKGROUND

Microbial translocation from the gut to systemic circulation contributes to immune activation during human immunodeficiency virus (HIV) infection and is usually assessed by measuring plasma levels of bacterial lipopolysaccharide (LPS). Fungal colonization in the gut increases during HIV-infection and people living with HIV (PLWH) have increased plasma levels of fungal polysaccharide (1→3)-β-D-Glucan (βDG). We assessed the contribution of circulating DG to systemic immune activation in PLWH.

METHODS

Cross-sectional and longitudinal assessments of plasma βDG levels were conducted along with markers of HIV disease progression, epithelial gut damage, bacterial translocation, proinflammatory cytokines, and βDG-specific receptor expression on monocytes and natural killer (NK) cells.

RESULTS

Plasma βDG levels were elevated during early and chronic HIV infection and persisted despite long-term antiretroviral therapy (ART). βDG increased over 24 months without ART but remained unchanged after 24 months of treatment. βDG correlated negatively with CD4 T-cell count and positively with time to ART initiation, viral load, intestinal fatty acid-binding protein, LPS, and soluble LPS receptor soluble CD14 (sCD14). Elevated βDG correlated positively with indoleamine-2,3-dioxygenase-1 enzyme activity, regulatory T-cell frequency, activated CD38+Human Leukocyte Antigen - DR isotype (HLA-DR)+ CD4 and CD8 T cells and negatively with Dectin-1 and NKp30 expression on monocytes and NK cells, respectively.

CONCLUSIONS

PLWH have elevated plasma βDG in correlation with markers of disease progression, gut damage, bacterial translocation, and inflammation. Early ART initiation prevents further βDG increase. This fungal antigen contributes to immune activation and represents a potential therapeutic target to prevent non-acquired immunodeficiency syndrome events.

Lymphocyte subsets in haematological patients with COVID-19: Multicentre prospective study

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Patients with haematological malignancies and COVID-19 are characterized by T lymphopenia and reduction in NK cell numbers.

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T lymphopenia in haematological patients with COVID-19 include reduction in CD4+ T cells numbers and lowered CD4/CD8 ratio.

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Increase in activated T cells with low CD4/CD8 ratio are crucial for the early stages of COVID-19 in haematological patients.

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Low levels of both TCRγ/δ and CD3+CD25+ T cells may indicate impaired cellular response to COVID-19 in haematological patients.

The role of immune dysregulation in the course and prognosis of COVID-19 is not clearly established. In particular, immune status in specific populations such as haematological patients, who have an impaired immunological system, has not been described so far. Here, we performed a comprehensive analysis of peripheral blood lymphocyte subsets in 27 SARS-CoV-2-infected patients, including 16 patients with haematological malignancies. We identified T cell subpopulations, B cells, NK cells and TCR α/ß and ɣ/ƍ-expressing T cells during COVID-19 infection, with significant changes observed in immune profiles during the course of disease, especially in haematological patients. We observed an increase in activated T lymphocytes (CD3+HLA-DR+ and CD3+CD8+HLA-DR+) in the early stages of SARS-CoV-2 infection with a concomitant decrease in the CD4/CD8 ratio in haematological patients compared to non-haematological patients affected by COVID-19. We also found a decrease in ɣ/ƍ T cells in both studied groups of patients, with lower numbers of CD25+ T cells and CD16+CD56+ NK cells in haematological patients compared to non-haematological patients with COVID-19. Our findings demonstrate, for the first time, impaired adaptive immunity in patients with haematological malignancies infected with COVID-19, resulting in impaired cellular immune responses to SARS-CoV-2. This warrants further investigation of this disease group in COVID-19 patient cohorts

Longitudinal imaging of HIV-1 spread in humanized mice with parallel 3D immunofluorescence and electron tomography

Dissemination of HIV-1 throughout lymphoid tissues leads to systemic virus spread following infection. We combined tissue clearing, 3D-immunofluorescence, and electron tomography (ET) to longitudinally assess early HIV-1 spread in lymphoid tissues in humanized mice. Immunofluorescence revealed peak infection density in gut at 10–12 days post-infection when blood viral loads were low. Human CD4+ T-cells and HIV-1–infected cells localized predominantly to crypts and the lower third of intestinal villi. Free virions and infected cells were not readily detectable by ET at 5-days post-infection, whereas HIV-1–infected cells surrounded by pools of free virions were present in ~10% of intestinal crypts by 10–12 days. ET of spleen revealed thousands of virions released by individual cells and discreet cytoplasmic densities near sites of prolific virus production. These studies highlight the importance of multiscale imaging of HIV-1–infected tissues and are adaptable to other animal models and human patient samples.

DOI:http://dx.doi.org/10.7554/eLife.23282.001

Role of T-Cell Dysfunction, Inflammation, and Coagulation in Microvascular Disease in HIV

BACKGROUND

Compared to uninfected adults, HIV-infected adults on antiretroviral therapy are at increased risk of cardiovascular disease. Given the increase in T-cell dysfunction, inflammation, and coagulation in HIV infection, microvascular dysfunction is thought to contribute to this excess cardiovascular risk. However, the relationships between these variables remain undefined.

METHODS AND RESULTS

This was a cross-sectional study of 358 HIV-infected adults from the SCOPE cohort. Macrovascular endothelial function was assessed using flow-mediated dilation of the brachial artery and microvascular function by reactive hyperemia. T-cell phenotype was determined by flow cytometry. Plasma markers of inflammation (tumor necrosis factor-α, interleukin-6, high-sensitivity C-reactive protein, sCD14) and coagulation (fibrinogen, D-dimer) were also measured. In all HIV+ subjects, markers of inflammation (tumor necrosis factor-α, high-sensitivity C-reactive protein), coagulation (D-dimer) and T-cell activation (CD8+PD1+, CD4+interferon+cytomegalovirus-specific) were associated with worse reactive hyperemia after adjusting for traditional cardiovascular risk factors and co-infections. In treated and suppressed subjects, tumor necrosis factor-α and CD8+PD1+ cells remained associated with worse reactive hyperemia after adjustment. Compared to the untreated subjects, CD8+PD1+ cells were increased in the virally suppressed group. Reactive hyperemia was predictive of flow-mediated dilation.

CONCLUSIONS

CD8+PD1+ cells and tumor necrosis factor-α were associated with microvascular dysfunction in all HIV+ subjects and the treated and suppressed group. Additionally, D-dimer, high-sensitivity C-reactive protein, sCD-14, and interleukin-6 were associated with microvascular dysfunction in all HIV+ subjects. Although T-cell dysfunction, inflammation, and microvascular dysfunction are thought to play a role in cardiovascular disease in HIV, this study is the first to look at which T-cell and inflammatory markers are associated with microvascular dysfunction in HIV-infected individuals.

Increased cell-free mitochondrial DNA is a marker of ongoing inflammation and better neurocognitive function in virologically suppressed HIV-infected individuals

Cell-free mitochondrial DNA (mtDNA) is a highly immunogenic molecule that is associated with several inflammatory conditions and with neurocognitive impairment during untreated HIV infection. Here, we investigate how cell-free mtDNA in cerebrospinal fluid (CSF) is associated with inflammation, neuronal damage, and neurocognitive functioning in the context of long-term suppressive antiretroviral therapy (ART). We quantified the levels of cell-free mtDNA in the CSF from 41 HIV-infected individuals with completely suppressed HIV RNA levels in blood plasma (<50 copies/mL) by droplet digital PCR. We measured soluble CD14, soluble CD163, interferon γ-induced protein 10 (IP-10), monocyte chemoattractant protein-1 (MCP-1), interleukin 6 (IL-6), interleukin 8 (IL-8), tumor necrosis factor-α (TNF-α), neopterin, and neurofilament light chain (NFL) by immunoassays in CSF supernatant or blood plasma. Higher levels of mtDNA in CSF were associated with higher levels of MCP-1 (r = 0.56, p < 0.01) in CSF and TNF-α (r = 0.43, p < 0.01) and IL-8 (r = 0.44, p < 0.01) in blood plasma. Subjects with a previous diagnosis of AIDS showed significantly higher levels of mtDNA (p < 0.01) than subjects without AIDS. The associations between mtDNA and MCP-1 in CSF and TNF-α in blood remained significant after adjusting for previous diagnosis of AIDS (p < 0.01). Additionally, higher levels of mtDNA were associated with a lower CD4 nadir (r = -0.41, p < 0.01) and lower current CD4% (r = -0.34, p = 0.03). Paradoxically, higher levels of mtDNA in CSF were significantly associated with better neurocognitive performance (r = 0.43, p = 0.02) and with less neuronal damage (i.e. lower NFL). Higher cell-free mtDNA is associated with inflammation during treated HIV infection, but the impact on neurocognitive functioning and neuronal damage remains unclear and may differ in the setting of suppressive ART.

Simian Immunodeficiency Virus Infection of Chimpanzees (Pan troglodytes) Shares Features of Both Pathogenic and Non-pathogenic Lentiviral Infections

The virus-host relationship in simian immunodeficiency virus (SIV) infected chimpanzees is thought to be different from that found in other SIV infected African primates. However, studies of captive SIVcpz infected chimpanzees are limited. Previously, the natural SIVcpz infection of one chimpanzee, and the experimental infection of six chimpanzees was reported, with limited follow-up. Here, we present a long-term study of these seven animals, with a retrospective re-examination of the early stages of infection. The only clinical signs consistent with AIDS or AIDS associated disease was thrombocytopenia in two cases, associated with the development of anti-platelet antibodies. However, compared to uninfected and HIV-1 infected animals, SIVcpz infected animals had significantly lower levels of peripheral blood CD4+ T-cells. Despite this, levels of T-cell activation in chronic infection were not significantly elevated. In addition, while plasma levels of β2 microglobulin, neopterin and soluble TNF-related apoptosis inducing ligand (sTRAIL) were elevated in acute infection, these markers returned to near-normal levels in chronic infection, reminiscent of immune activation patterns in ‘natural host’ species. Furthermore, plasma soluble CD14 was not elevated in chronic infection. However, examination of the secondary lymphoid environment revealed persistent changes to the lymphoid structure, including follicular hyperplasia in SIVcpz infected animals. In addition, both SIV and HIV-1 infected chimpanzees showed increased levels of deposition of collagen and increased levels of Mx1 expression in the T-cell zones of the lymph node. The outcome of SIVcpz infection of captive chimpanzees therefore shares features of both non-pathogenic and pathogenic lentivirus infections.

The HIV-1/AIDS pandemic is the result of cross-species transmission of simian immunodeficiency virus (SIVcpz) from chimpanzees to humans. Many African primates are infected with SIV, but those studied in captivity generally do not develop disease. However, wild chimpanzees infected with SIVcpz are at increased risk of death and may develop an AIDS-like disease. It has therefore been suggested that the viral features which SIVcpz and HIV-1 share, that differentiate them from other species’ SIV, may be critical in the development of disease in both humans and chimpanzees. Here, we present a long-term follow-up of 7 SIVcpz infected chimpanzees, housed in primate centres in the US and Europe, under similar conditions to other studied models. These animals did not develop an AIDS-like disease, after up to 25 years of infection, and showed features similar to other species where disease rarely develops, such as limited immune activation in the blood. However, they also had significantly reduced CD4+ T-cells and disruption to the secondary lymphoid tissues, normally associated with pathogenic primate lentiviral infections. Thus, while SIVcpz infection of chimpanzees shares features of both pathogenic and non-pathogenic infections, disease has not developed in captivity.

Immune activation and viral replication after vaccination with an influenza A H1N1 2009 vaccine in HIV-infected children receiving antiretroviral therapy

Immunization with a pandemic influenza A H1N1 2009 was recommended for HIV-infected patients. However, there is limited information concerning the impact of immunization with this vaccine on immune activation and HIV viral replication. In this study, 45 HIV-infected children and adolescents receiving antiretroviral therapy were immunized with a 2-dose series of nonadjuvated monovalent influenza A H1N1 2009 vaccine upon enrollment and approximately 1 month later. Immunogenicity was determined by haemagglutination inhibition assay. The level of immune activation was determined by identification of CD38 and HLA-DR on CD8+ T cells. Patients were divided into 2 groups which include patients who had an undetectable HIV viral load (HIV detectable group) and patients who show virological failure (HIV nondetectable group). The results showed seroconversion rate of 55.2% in HIV nondetectable group, whereas 31.3% was found in HIV detectable group. Both groups of patients showed no major increase in immune activation after immunization. Interestingly, a decrease in the frequency of CD8+ T cells that coexpressed CD38 and HLA-DR was observed after immunization in both groups of patients. We suggested that immunization with influenza A H1N1 2009 vaccine can induce immune response to the pandemic virus without major impact on HIV viral replication and immune activation.

The cardiovascular risk marker asymmetric dimethylarginine is elevated in asymptomatic, untreated HIV-1 infection and correlates with markers of immune activation and disease progression

BACKGROUND

As lifespan in HIV infection increases, cardiovascular disease has emerged as a cause of morbidity and mortality. Asymmetric dimethylarginine is an established marker of endothelial dysfunction and predicts cardiovascular events. The role of asymmetric dimethylarginine in HIV-related cardiovascular disease has not been established. Our aim was to determine whether asymmetric dimethylarginine concentrations were elevated in treatment naïve, HIV-infected subjects and to correlate these with markers of immune activation and disease progression.

METHODS

Serum samples were collected from HIV-positive and -negative subjects attending a primary health care clinic over a 12-month period. Asymmetric dimethylarginine concentrations were measured and correlated with CD4 count, viral load, hsCRP, IL-6, IgG, adenosine deaminase and CD8/38 T lymphocytes.

RESULTS

Sixty HIV-positive participants (mean age 32.0 years) and 20 HIV-negative controls (mean age 32.4 years) were studied. All were of black ethnicity. The mean asymmetric dimethylarginine concentration in the infected group measured 0.67 µmol/L (95% CI 0.62-0.72 µmol/L) which was significantly higher than in the control group of 0.48 µmol/L (95% CI 0.40-0.56 µmol/L). Asymmetric dimethylarginine correlated inversely with CD4 counts and positively with IgG, adenosine deaminase and CD8/38 T lymphocytes. No significant correlation was found with hsCRP, IL-6, or viral load.

CONCLUSION

We demonstrated that asymmetric dimethylarginine is elevated in HIV infection, in patients with relatively well-preserved CD4 counts not yet on anti-retroviral treatment. We showed significant correlations of asymmetric dimethylarginine with CD8/38 T lymphocytes, IgG and adenosine deaminase, suggesting that T-cell activation and the adaptive immune response underlie asymmetric dimethylarginine elevation in this population.

Expression of inhibitory markers is increased on effector memory T cells during hepatitis C virus/HIV coinfection as compared to hepatitis C virus or HIV monoinfection

OBJECTIVE

Hepatitis C virus (HCV)/HIV coinfection is associated with rapid progression of hepatic fibrosis and liver disease. T-cell response has been implicated in the pathophysiological outcome of the disease.

DESIGN

This study sought to evaluate the role of memory T-cell exhaustion in enhancing immune dysfunction during coinfection.

METHODS

Sixty-four patients were included in the study; HCV monoinfected (n = 21), HIV monoinfected (n = 23), HCV/HIV coinfected (n = 20), and healthy controls (n = 20). Peripheral blood mononuclear cells (PBMCs) were isolated; immunophenotyped and functional assays were performed.

RESULTS

A significant increase in the naive T cells and central memory T cells and a marked reduction in effector memory T cells (TEM) were observed with coinfection as compared to monoinfection. Inhibitory markers programmed death 1 (PD-1) and T-cell immunoglobulin and mucin domain containing molecule 3 (TIM3) were highly upregulated on TEM in coinfection and functionally, these TEM cells displayed lowered proliferation. Increased expression of PD-1 and TIM3 correlated with decreased levels of CD8+CD107a+ TEM cells in coinfection. Pro-inflammatory cytokines interferon-γ and interleukin-2 (IL-2) secretion by TEM cells were also reduced during chronic viral infection. Secretion of IL-10, a human cytokine synthesis inhibitory factor, was significantly upregulated in CD4 TEM with HCV/HIV coinfection in comparison to HCV monoinfection.

CONCLUSION

TEM cells play an important role during viral infection and enhanced expression of inhibitory markers is associated with decreased proliferation and cytotoxicity and increased IL-10 production, which was pronounced in HCV/HIV coinfection. Thus, decreased TEM functionality contributes to diminished host immune responses during HCV/HIV coinfection as compared to HCV or HIV monoinfection.

VS411 reduced immune activation and HIV-1 RNA levels in 28 days: randomized proof-of-concept study for antiviral-hyperactivation limiting therapeutics

Background

A new class of antiretrovirals, AntiViral-HyperActivation Limiting Therapeutics (AV-HALTs), has been proposed as a disease-modifying therapy to both reduce Human Immunodeficiency Virus Type 1 (HIV-1) RNA levels and the excessive immune activation now recognized as the major driver of not only the continual loss of CD4⁺ T cells and progression to Acquired Immunodeficiency Syndrome (AIDS), but also of the emergence of both AIDS-defining and non-AIDS events that negatively impact upon morbidity and mortality despite successful (ie, fully suppressive) therapy. VS411, the first-in-class AV-HALT, combined low-dose, slow-release didanosine with low-dose hydroxycarbamide to accomplish both objectives with a favorable toxicity profile during short-term administration. Five dose combinations were administered as VS411 to test the AV-HALT Proof-of-Concept in HIV-1-infected subjects.

Methods

Multinational, double-blind, 28-day Phase 2a dose-ranging Proof-of-Concept study of antiviral activity, immunological parameters, safety, and genotypic resistance in 58 evaluable antiretroviral-naïve HIV-1-infected adults. Randomization and allocation to study arms were carried out by a central computer system. Results were analyzed by ANOVA, Kruskal-Wallis, ANCOVA, and two-tailed paired t tests.

Results

VS411 was well-tolerated, produced significant reductions of HIV-1 RNA levels, increased CD4⁺ T cell counts, and led to significant, rapid, unprecedented reductions of immune activation markers after 28 days despite incomplete viral suppression and without inhibiting HIV-1-specific immune responses. The didanosine 200 mg/HC 900 mg once-daily formulation demonstrated the greatest antiviral efficacy (HIV-1 RNA: −1.47 log₁₀ copies/mL; CD4⁺ T cell count: +135 cells/mm³) and fewest adverse events.

Conclusions

VS411 successfully established the Proof-of-Concept that AV-HALTs can combine antiviral efficacy with rapid, potentially beneficial reductions in the excessive immune system activation associated with HIV-1 disease. Rapid reductions in markers of immune system hyperactivation and cellular proliferation were obtained despite the fact that VS411 did not attain maximal suppression of HIV RNA, suggesting this effect was due to the HALT component.

Trial Registration

ITEudraCT 2007-002460-98

The role of cytokines in the pathogenesis and treatment of HIV infection

HIV immune activation plays an important role in the immunopathogenesis of the disease. The mechanisms driving this immune activation are partially defined and likely are the result of multiple factors. The introduction of combination antiretroviral therapy (cART) has improved the life expectancy of HIV infected individuals, however there is evidence that in the setting of "undetectable" HIV-RNA plasma levels, there is some level of persistent immune activation in these patients. A better understanding of the immune activation pathways should be of value in developing complementary therapies to restore the immune systems of patients with HIV infection. This review discusses the cytokine mediated pathways of immune activation of the CD4 and CD8 T cell pools during HIV infection.

Chronically HIV-1 Infected Patients Exhibit Low Frequencies of CD25+ Regulatory T Cells

The characterization of regulatory T cells (Treg) during HIV infection has become of particular interest considering their potential role in the pathogenesis of the acquired immunodeficiency syndrome. Different reports on Tregs in HIV-infected patients vary greatly, depending on the state of disease progression, anatomical compartment, and the phenotypic markers used to define this cell subpopulation. To determine the frequency of Tregs we included paired samples from peripheral blood and rectal biopsies from controls and chronic HIV patients with or without detectable viral load. Tregs were determined by flow cytometry using three different protocols: CD4⁺Foxp3⁺; CD4⁺Foxp3⁺CD127^Low/-, and CD4⁺CD25⁺CD127^Low/-. In addition, and with the purpose to compare the different protocols we also characterized Tregs in peripheral blood of HIV negative individuals with influenza like symptoms. Here, we report that Treg characterization in HIV-infected patients as CD4⁺Foxp3⁺ and CD4⁺Foxp3⁺CD127^Low/- cells was similar, indicating that both protocols represent a suitable method to determine the frequency of Tregs in peripheral blood mononuclear cells (PBMC) and gut associated lymphoid tissue (GALT). In contrast, in HIV but not in flu-like patients, detection of Tregs as CD4⁺CD25⁺CD127^Low/- cells resulted in a significantly lower percentage of these cells. In both, HIV patients and controls the frequency of Treg was significantly higher in GALT compared to PBMC. The frequency of Tregs in PBMC and GALT using CD4⁺Foxp3⁺ and CD4⁺Foxp3⁺CD127^Low/- was higher in HIV patients than in controls. Similarly, the frequency of Treg using any protocol was higher in flu-like patients compared to controls. The results suggest that relying on the expression of CD25 could be unsuitable to characterize Tregs in PBMC and GALT samples from a chronic infection such as HIV.

Systemic dendritic cell mobilization associated with administration of FLT3 ligand to SIV- and SHIV-infected macaques

Reports indicate that myeloid and plasmacytoid dendritic cells (mDCs and pDCs), which are key effector cells in host innate immune responses, can be infected with HIV-1 and are reduced in number and function during the chronic phase of HIV disease. Furthermore, it was recently demonstrated that a sustained loss of mDCs and pDCs occurs in SIV-infected macaques. Since loss of functional DC populations might impair innate immune responses to opportunistic microorganisms and neoplastic cells, we explored whether inoculation of naive and SIV- or SHIV-infected pigtailed macaques with the hematopoietic cytokine FLT3-ligand (FLT3-L) would expand the number of mDCs and pDCs in vivo. After the macaques received supraphysiologic doses of FLT3-L, mDCs, pDCs, and monocytes increased up to 45-fold in blood, lymph nodes, and bone marrow (BM), with DC expansion in the BM preceding mobilization in blood and lymphoid tissues. FLT3-L also increased serum levels of IL-12, at least transiently, and elicited higher surface expression of HLA-DR and the activation markers CD25 and CD69 on NK and T cells. During and after treatment of infected animals, APCs increased in number and were activated; however, CD4(+) T cell numbers, virion RNA, and anti-SIV/SHIV antibody titers remained relatively stable, suggesting that FLT3-L might be a safe modality to expand DC populations and provide therapeutic benefit during chronic lentivirus infections.

A universal anti-HIV-1 Tat epitope vaccine that is fully synthetic and self-adjuvanting

Circulating HIV-1 Tat protein is essential for maintenance of the chronic HIV replication that predicates both HIV transmission and clinical progression to AIDS/death. A synthetic anti-Tat epitope vaccine (TUTI-16) was designed to induce neutralizing antibodies to Tat and, hopefully, provide immunological control of HIV replication. TUTI-16 is composed of (1) a conserved Tat B cell epitope (Tat 4-12), rendered universal by introducing known variant amino acids at variable positions 7, 9 and 12 during solid phase synthesis, (2) a promiscuous T helper sequence and (3) a lipopeptide toll-like receptor 2 (TLR2) agonist. TUTI-16 induced high titer antibodies against all 8 known variants of the Tat epitope.

Effect of Immunomodulating Adjuvant Dzherelo (Immunoxel) in HIV Infected Patients Receiving Standard Antiretroviral Therapy

Open-label, matched-case, comparative trial was conducted in 40 HIV-infected patients to evaluate the adjunct effect of Dzherelo (Immunoxel) on immune and viral parameters. Arm A (n=20) received anti-retroviral therapy (ART) consisting of zidovudine, lamivudine, and efavirenz and arm B (n=20) received ART with Dzherelo. After 2 months total T-lymphocytes increased in ART recipients from 664 to 819 cells/μl (P=0.06), whereas in Dzherelo recipients they rose from 595 to 785(P=0.03). The CD4 T-cells expanded by 57.3% (218 to 343; P=0.002) in the ART arm and by 93.5% (184 to 356; P=0.004) in the Dzherelo arm. The accrual in absolute and relative number of CD8+ lymphocytes in ART and in the Dzherelo recipients was 43.2% (2.7%) and 50.4% (-0.5%) respectively. The CD4/CD8 ratio in Dzherelo recipients increased from 1.495 to 1.940 (P=0.03) but insignificant in the control: 1.418 to 1.613 (P=0.14). Activated CD3+ HLADR+ T-cells increased from 209 to 264 (P=0.02) and from 161 to 348 (P=0.0007) in ART and Dzherelo recipients respectively. No changes in CD20+ B-lymphocytes were seen in the control, but in Dzherelo patients they declined from 509 to 333 (P=0.00008). The proportion of CD3- CD16+CD56+ NK cells was not affected by ART but addition of Dzherelo raised NK cells from 11.2% to 17.1% (P=0.0001). About three-quarters (14/19) of patients on ART displayed decrease in viral load (1718 to 1419 copies/ml; P=0.008), while 95% of patients on Dzherelo had a decrease (1793 to 1368; P=0.001). Dzherelo has a favorable effect on the immune status and viral burden when given as an immunomodulating adjunct to ART.

HIV-1 binding to CD4 on CD4+CD25+ regulatory T cells enhances their suppressive function and induces them to home to, and accumulate in, peripheral and mucosal lymphoid tissues: an additional mechanism of immunosuppression

The establishment and persistence of many chronic infections have been demonstrated to depend on restraint of the vigor of the anti-microbial immune responses by CD4+CD25+ regulatory T (Treg) cells. In HIV-infected individuals, Treg cells suppress both HIV-specific and general CD4+ and CD8+ T cell responses. Increases of CD4+CD25+ Treg cell function during viral infections might be mediated by host-derived pro-inflammatory molecules or directly by viral infection or binding. We examined the effect HIV has upon binding to CD4+CD25+ Treg cells by exposing human purified CD4+CD25+ T cells from healthy donors to HIV-1 in vitro and assessing their Treg-associated functional marker profile and suppressive activities. We found that HIV-1 binding increased their suppressor activities by 2- to 5-fold, which was accompanied by enhanced expression of Treg-associated functional markers sCTLA-4, glucocorticoid-induced tumor necrosis factor receptor and FoxP3. Moreover, HIV-1 binding extended the survival of CD4+CD25+ Treg cells and up-regulated the expression of homing receptors CD62L and integrin alpha4beta7, which in turn would result in Treg cells migrating more rapidly to the peripheral lymph nodes and mucosal lymphoid tissues where anti-HIV immune responses are occurring. Importantly, CD4+CD25+ Treg cells exposed to HIV were not susceptible to homing-induced apoptosis like are other resting CD4+ cells following HIV-1 binding. We show that CD4+CD25+ Treg cells respond directly to HIV-1 itself through HIV gp120 interactions with CD4 molecules. Collectively, our findings explain a mechanism that contributes to the abnormal accumulation of intensified Treg cells in lymphoid and mucosal tissues in HIV patients, resulting in impairment of immune responses which would greatly help HIV persistence.

HIV infection-associated immune activation occurs by two distinct pathways that differentially affect CD4 and CD8 T cells

HIV infection is characterized by a brisk immune activation that plays an important role in the CD4 depletion and immune dysfunction of patients with AIDS. The mechanism underlying this activation is poorly understood. In the current study, we tested the hypothesis that this activation is the net product of two distinct pathways: the inflammatory response to HIV infection and the homeostatic response to CD4 T cell depletion. Using ex vivo BrdU incorporation of PBMCs from 284 patients with different stages of HIV infection, we found that CD4 proliferation was better predicted by the combination of CD4 depletion and HIV viral load (R(2) = 0.375, P < 0.001) than by either parameter alone (CD4 T cell counts, R(2) = 0.202, P < 0.001; HIV viremia, R(2) = 0.302, P < 0.001). Interestingly, CD8 T cell proliferation could be predicted by HIV RNA levels alone (R(2) = 0.334, P < 0.001) and this predictive value increased only slightly (R(2) = 0.346, P < 0.001) when CD4 T cell depletion was taken into account. Consistent with the hypothesis that CD4 T cell proliferation is driven by IL-7 as a homeostatic response to CD4 T cell depletion, levels of phosphorylated STAT-5 were found to be elevated in naive subsets of CD4 and CD8 T cells from patients with HIV infection and in the central memory subset of CD4 T cells. Taken together these data demonstrate that at least two different pathways lead to immune activation of T cells in patients with HIV infection and these pathways differentially influence CD4 and CD8 T cell subsets.

HIV immunopathogenesis and strategies for intervention

Therapeutic options aimed at tackling the HIV pandemic face many obstacles. The lack of readily accessible and affordable therapies means that most of those affected go untreated. The array of escape mechanisms used by HIV has undermined the efficiency of many antiviral products and continually represents a barrier to the development of an effective vaccine. Recent developments have seen a shift away from a cytopathic viral model of HIV pathogenesis towards the crucial role of immunopathogenic features--notably generalised immune activation--in the development of AIDS. As conventional vaccine strategies have sought to promote viral neutralisation and suppressive cellular responses, novel strategies that aim to address HIV immunopathogenesis should be sought. We review current opinion on HIV-induced pathogenic immune activation and strategies aimed at eliminating HIV, including a potential role for non-neutralising antibodies as part of a therapeutic vaccine option.

Increased interleukin-17 production both in helper T cell subset Th17 and CD4-negative T cells in human immunodeficiency virus infection

Interleukin (IL)-17 is produced mainly by activated CD4(+) T cells, currently known as Th17. Human immunodeficiency virus (HIV) pathogenesis leads to CD4(+) T cell depletion. This is the first report of IL-17 in HIV infection. We assessed IL-17 expression in the CD4(+) T cells (Th17) of 40 asymptomatic HIV-infected treatment-naive patients compared with 40 HIV-seronegative volunteers. Peripheral blood mononuclear cells (PBMCs), with/without phorbol myristate acetate (PMA)/ionomycin stimulation, were stained with CD3, CD4, IL-17, and interferon (IFN)-gamma antibodies and analyzed by four-color flow cytometry. Both groups had comparable baseline data, except for age (mean+/-SD): 36 +/- 9 versus 30 +/- 9 yr (p= 0.001), CD4(+) T cell counts (median): 218 versus 623 cells/microL (p < 0.0001), CD8(+) T cell counts (median): 875.5 versus 382.5 cells/microL ((p) < 0.0001), and CD4(+)/CD8(+) cell ratios (median): 0.225 versus 1.45 (p< 0.0001). Without stimulation, the percentages of IL-17(+) CD3(+) CD4() and IL-17(+) CD3(+) CD4() cells among HIV-seropositive and -seronegative volunteers (median) were as follows: 0.68 versus 0.12% (p< 0.0001) and 0.92 versus 0.09% (p< 0.0001), respectively. With PMA/ionomycin stimulation, the percent IL-17 expression in CD4(+) cells (median) was 1.45 versus 0.65 (p< 0.0001) and in CD4() T cells it was 1.0 versus 0.12 (p< 0.0001). In conclusion, HIV infection is associated with a significant increase in IL-17 production in both CD4(+) and CD4() T cells in peripheral blood. IL-17 expression was further inducible by PMA/ionomycin stimulation in vitro only in CD4(+) T cells. The roles of IL-17 and Th17 in HIV viral replication and immunopathogenesis are under further investigation.

The role of virus-induced regulatory T cells in immunopathology

In recent years, regulatory T cells have received increased attention for their role in immune responses to microbial infections. The list of microbial pathogens associated with regulatory T cell responses is growing rapidly and includes bacteria, viruses, parasites, and fungi. As the biology of regulatory T cells is revealed, we are discovering that their induction during infection is a normal aspect of immunity, necessary to limit collateral damage from inflammatory responses and aggressive immunological effectors. Thus, these cells play a critical role in maintaining the delicate balance between preventing immunopathology and allowing the immune response to clear infections. While generally successful, there are notable exceptions where regulatory T cell-mediated suppression appears to be responsible for allowing certain viruses to establish and maintain a persistent state. In this review, we will discuss our current understanding of what virus-induced regulatory T cells are, how they are induced, and what mechanisms they use to suppress immunity. The complex role of Tregs in regulating immunity to viral infections, and the consequences their activity has on disease is illustrated by a review of specific viral infections including hepatitis C virus and human immunodeficiency virus.

Interferon-alpha differentially rescues CD4 and CD8 T cells from apoptosis in HIV infection

OBJECTIVE

To examine the effects of interferon-alpha (IFN-alpha) on T cell survival and activation in HIV infection.

DESIGN

The effects of IFN-alpha on spontaneous apoptosis and CD38 expression among T cell subsets were determined in vitro and studied in relation to CD4 cell counts, plasma HIV RNA levels and the age of the subjects.

METHODS

Peripheral blood mononuclear cells from 48 HIV-infected persons and 17 healthy donors were incubated in vitro overnight with or without the addition of IFN-alpha. Percentages of apoptotic cells (positive for annexin V) and CD38 cells were determined among T cell subsets.

RESULTS

IFN-alpha inhibited spontaneous apoptosis of CD4 and CD8 T lymphocytes. This protective activity was impaired in CD4 T cells from HIV-infected persons. The reduced protection of IFN-alpha among CD4 cells from HIV-infected persons was not related to the percentages of activated (CD38 or CD45RO+CD38+) cells. Surprisingly, IFN-alpha induced CD38 expression among CD8 T cells from HIV-infected persons, and the magnitude of this effect was directly related to circulating CD4 T cell count. The CD8 T cell subset that expressed CD38 in response to IFN-alpha was defined as CD28 negative, CD62 ligand (CD62L) intermediate/negative.

CONCLUSIONS

Heightened expression of IFN-alpha in HIV infection may contribute to the phenotypic activation state that characterizes chronic infection while a diminished responsiveness of CD4 T cells to the protective effect of this cytokine may contribute to differential survival of CD4 and CD8 T cells in HIV disease.

FOXP3 mRNA levels are decreased in peripheral blood CD4+ lymphocytes from HIV-positive patients

The impact of HIV infection on regulatory CD4(+)CD25(high) (Treg) lymphocyte subpopulations was evaluated by FOXP3 quantitative reverse transcriptase polymerase chain reaction and by flow cytometry. FOXP3 mRNA was quantified in peripheral blood mononuclear cells or purified CD4(+) lymphocytes from HIV(+) lymphopenic patients. Patients were distributed among clinical stages A, B, and C and received highly active antiretroviral therapy. The frequency of CD4(+)CD25(high) lymphocytes, measured by flow cytometry, was decreased in HIV patients (n = 38) compared with the group of uninfected subjects (n = 39). FOXP3 mRNA levels were found decreased in HIV patients (n = 25) compared with controls (n = 17) when expression of CD3gamma or beta-actin but not that of TATA box binding protein 1 was used for data normalization. Our results are compatible with a decrease of the Treg lymphocytes during HIV infection. The consequences of a Treg decrease are discussed in the context of immunologic anomalies observed during HIV infection.

Regeneration and tolerance factor prevents bystander T-cell death associated with human immunodeficiency virus infection

Human immunodeficiency virus (HIV) infection is characterized by a depletion of T cells. This depletion is caused both by the virus-induced death of infected T cells and by the death of uninfected cells (bystander depletion) by a mechanism which is largely uncharacterized. Regeneration and tolerance factor (RTF) is a subunit of the vacuolar ATPase and a protein that is involved with activation and apoptosis. Anti-RTF antibodies mediate apoptosis in T lymphocytes. When anti-RTF was added to lymphocytes from an HIV-positive individual, they underwent larger amounts of apoptosis than cells taken from healthy controls. When lymphocytes were examined by Western blotting, those from HIV-positive individuals exhibited increased levels of expression of the 50-kDa protein (P < 0.001). A 70-kDa protein was the predominant form of RTF in uninfected control lymphocytes, being expressed in 100% of individuals studied. The expression of the 50-kDa protein in HIV-positive individuals correlated with decreased absolute CD4 counts with a sensitivity of 92% and a positive predictive value of 86%. When uninfected lymphocytes were stimulated with anti-CD3 and anti-CD28, no RTF was detected during early stimulation but a 50-kDa protein was expressed during late stimulation. When the susceptibilities of the lymphocytes to anti-RTF-induced apoptosis were measured, they correlated with the size of the RTF protein expressed. The cells were not susceptible to apoptosis when the 70-kDa RTF was present but were susceptible when the 50-kDa RTF was present. We propose that the increase in the levels of the 50-kDa RTF on cells from HIV-positive individuals is important in preventing the cell from undergoing apoptosis.

Activation and Coreceptor Expression of T Lymphocytes in HIV/AIDS Patients of China

The objective of this paper was to investigate the activation and coreceptor CCR5, CXCR4 expression of T lymphocytes in HIV/AIDS patients of China, and to study their association with disease progression. Seventy-seven HIV/AIDS patients and thirteen normal controls were enrolled and three-color flow-cytometry was used to detect the activation marker HLA-DR, CD38 and the coreceptor CCR5, CXCR4 expression on T lymphocytes in whole blood samples taken from the patients and the controls. The HLA-DR, CD38 and CCR5 expression on CD4, CD8+ T cells in AIDS patients was higher than in asymptomatic HIV-1 infected patients and normal controls (p < 0.05); The activation and CCR5 expression on T lymphocytes significantly correlated with CD4+ T lymphocyte number and viral load. The activation on T lymphocytes and the expression of CCR5 on T lymphocytes in HIV/AIDS patients of China are significantly correlated with disease progression.

Hyper-responsiveness to stimulation of human immunodeficiency virus-infected CD4+ T cells requires Nef and Tat virus gene products and results from higher NFAT, NF-kappaB, and AP-1 induction

A chronic state of immune hyperactivation is a feature of human immunodeficiency virus type-1 (HIV-1) infection. Studies on the molecular mechanisms by which HIV-1 can modulate the activation state of T cells indicate that both Nef and Tat can alter T cell activation. However, the vast majority of data has been obtained from experiments performed with vectors encoding a single virus protein. We demonstrate that infection of human CD4(+) T lymphocytes with fully infectious HIV-1 leads to a hyper-responsiveness of the interleukin-2 promoter. Hypersensitivity in HIV-1-infected T cells was observed upon stimulation with various agents that are engaging different signal transduction pathways. Experiments performed with recombinant heat stable antigen-encoding HIV-1 indicated that the virus-infected cells are the cells with an enhanced response. Both Nef and Tat are involved in this virus-mediated enhancing effect on interleukin-2 promoter activity. Interestingly, whereas Nef seems to be acting mainly through hyperactivation of nuclear factor of activated T cells (NFAT), Tat acts in an NFAT-independent manner. Mobility shift experiments demonstrated that the HIV-1-associated priming of human T cells for stimulation results in a greater induction of transcription factors recognized as essential players in T cell activation, i.e. NFAT, NF-kappaB, and AP-1. A hyper-responsive state was also established upon HIV-1 infection of a more natural cellular reservoir, i.e. primary CD4(+) T lymphocytes. Considering that the HIV-1 life cycle is tightly regulated by the T cell signaling machinery, the priming for activation of a major viral reservoir represents a means by which this retrovirus can create an ideal cellular microenvironment for its propagation and maintenance.

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.

Simian immunodeficiency virus infection in neonatal macaques

Children with human immunodeficiency virus infection often have higher viral loads and progress to AIDS more rapidly than adults. Since the intestinal tract is a major site of early viral replication and CD4(+) T-cell depletion in adults, we examined the effects of simian immunodeficiency virus (SIV) on both peripheral and intestinal lymphocytes from 13 neonatal macaques infected with SIVmac239. Normal neonates had more CD4(+) T cells and fewer CD8(+) T cells in all tissues than adults. Surprisingly, neonates had substantial percentages of CD4(+) T cells with an activated, memory phenotype (effector CD4(+) T cells) in the lamina propria of the intestine compared to peripheral lymphoid tissues, even when examined on the day of birth. Moreover, profound and selective depletion of jejunum lamina propria CD4(+) T cells occurred in neonatal macaques within 21 days of infection, which was preceded by large numbers of SIV-infected cells in this compartment. Furthermore, neonates with less CD4(+) T-cell depletion in tissues tended to have higher viral loads. The persistence of intestinal lamina propria CD4(+) T cells in some neonates with high viral loads suggests that increased turnover and/or resistance to CD4(+) T-cell loss may contribute to the higher viral loads and increased severity of disease in neonatal hosts.

HIV, 'an evolving species'. Roles of cellular activation and co-infections

Each small variation of the genome of a species can be preserved if it is useful for the survival of the species in a given environment. Within this framework, the finality of the biological cycle of HIV consists in a search for harmony (biological coherence) with man, which is to say a stable condition. Cellular activation appears to be the strategy developed by HIV in order to achieve this coherence. The price of this strategy is the AIDS. The first contact between HIV and immune system appears to determine the subsequent clinical outcome and the future of HIV. Lymphocytic activation varies during the course of the vital cycle of HIV. For each individual, this lymphocytic activation depends on both the HLA repertoire acquired during thymic ontogenesis and the antigenic experience before and after HIV infection. Thus intercurrent infections alter the immune condition of the organism and influence the outcome of HIV. We described a synthetic analysis of the effects of HIV on the surface protein expression and the cellular activation pathways which should provide insights in the evolutionary relationship between HIV and man and should permit to do a more physiological therapeutic approach.

Immunomodulatory activity of TNF-alpha during acute liver injury induced by D-galactosamine and its protection by PGE1 in rats

Tumour necrosis factor-alpha (TNF-alpha) mediates hepatocyte cell death by D-galactosamine (D-GalN) and its protection by prostaglandin E(1) (PGE(1)). The activation of immune system plays an important role in the development of liver injury. TNF-alpha and PGE(1) regulate the activity and cytokine release of different inflammatory cells. The present study was undertaken to determine if the noxious or hepatic protective properties of TNF-alpha during D-GalN-induced liver injury was related to an alteration by PGE(1) of the immunoregulatory activity of TNF-alpha. The role of TNF-alpha was assessed by anti-TNF-alpha antibodies to D-GalN-treated rats in the presence or absence of PGE(1). D-GalN enhanced the percentage of monocytes and T lymphocytes in the total peripheral blood mononuclear cells (PBMCs). D-GalN enhanced the activation degree of monocytes, but reduced that of T lymphocytes. D-GalN also enhanced TNF-alpha, IL-1alpha, IL-6 and IFN-gamma concentrations in blood. Anti-TNF-alpha antibodies abolished all immunological changes and greatly reduced liver damage induced by D-GalN. The protection by PGE(1) against D-GalN liver injury was associated with an increase in TNF-alpha concentration and a reduction of IL-1alpha and IL-6. These changes were associated with a reduction of monocyte activation degree and a recovery of that of T lymphocytes. Although anti-TNF-alpha antibodies abolished the protection by PGE(1) against D-GalN-liver injury, they did not essentially counteract the effect of the prostanoid in all immunological parameters studied. The present study showed that the protection against D-GalN liver damage by PGE(1) or anti-TNF-alpha was associated with similar effects on the inflammatory parameters studied. Nevertheless, the abolishment of liver protection by PGE(1) with anti-TNF-alpha in D-GalN-treated rats in the presence of a protective cytokine profile suggests that the release of TNF-alpha induced by PGE(1) pre-administration was exerting a direct protective effect on hepatocytes against D-GalN injury. Consequently, the effect of PGE(1) on inflammatory parameters studied during liver injury was unrelated to TNF-alpha.

Anticellular and immunosuppressive properties of ethanolic extract of Acorus calamus rhizome

Modulation of immune response to alleviate disease has been of interest since long. Plant extracts have been widely investigated for possible immunomodulatory properties. We have evaluated the anticellular and immunomodulatory properties of ethanolic extract of Acorus calamus rhizome. This extract inhibited proliferation of mitogen (phytohaemagglutinin; PHA) and antigen (purified protein derivative; PPD)-stimulated human peripheral blood mononuclear cells (PBMCs). In addition, A. calamus extract inhibited growth of several cell lines of mouse and human origin. It also inhibited production of nitric oxide (NO), interleukin-2 (IL-2) and tumor necrosis factor-alpha (TNF-alpha). Intracytoplasmic interferon-gamma (IFN-gamma) and expression of cell surface markers, CD16 and HLA-DR, on human PBMC, were not affected on treatment with A. calamus extract but CD25 expression was down regulated. Our study demonstrates the antiproliferative and immunosuppressive potential of ethanolic extract of A. calamus rhizome in vitro.

Immunomodulation by ethanolic extract of Boerhaavia diffusa roots

We have earlier reported that ethanolic extract of Boerhaavia diffusa, a plant used in Indian traditional system of medicine, significantly inhibits the cell proliferation. This led us to evaluate the immunomodulatory properties of this plant extract on various in vitro tests such as human natural killer (NK) cell cytotoxicity, production of nitric oxide (NO) in mouse macrophage cells, RAW 264.7, interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-alpha), intracytoplasmic interferon-gamma (IFN-gamma) and expression of various cell surface markers on human peripheral blood mononuclear cells (PBMCs). Ethanolic extracts of B. diffusa roots inhibited human NK cell cytotoxicity in vitro, production of NO in mouse macrophage cells, IL-2 and TNF-alpha in human PBMCs. Intracytoplasmic IFN-gamma and cell surface markers such as CD16, CD25, and HLA-DR did not get affected on treatment with B. diffusa extract. Our study demonstrates immunosuppressive potential of ethanolic extract of B. diffusa.

Resting CD4(+) T cells with CD38(+)CD62L(+) produce interleukin-4 which contributes to enhanced replication of T-tropic human immunodeficiency virus type 1

A significant increase in the CD38(+) population among T lymphocytes has been observed in human immunodeficiency virus type 1 (HIV-1)-infected carriers. We previously reported a higher replication rate of T-tropic HIV-1 in the CD4(+)CD38(+)CD62L(+) than CD38(-) subset under conditions of mitogen stimulation after infection. Here, we revealed a similarly high susceptibility in the CD38(+) subset on culture with conditioned medium containing Th2 cytokine, interleukin (IL)-4 that was produced endogenously from this subset on stimulation with mitogen or anti-CD3 antibody for 3 days. The contribution of IL-4 to the upregulated production of virus in the CD38(+) subset was confirmed by culture of this subset with recombinant human IL-4. In contrast, the rate of replication in the CD38(-) subset was not augmented in the conditioned medium from either subset or with IL-4. However, there were no differences in the surface expression of IL-4 receptor or HIV-1 receptors CD4 and CXCR4 between the two subsets. Thus, the CD4(+)CD38(+)CD62L(+) subset comprises a specific cell population secreting endogenous Th2 cytokine that contributes to the efficient production of T-tropic HIV-1 through upregulation at a certain stage of the viral life cycle, probably after the adsorption step.

Evidence of B cell clonal expansion in HIV type 1-infected patients

HIV-1 infection results in a gradual decrease in CD4(+) T cell counts and progressive immune deficiency. Increased T cell turnover in HIV-1-infected patients, which can be interpreted as T cell clonal expansion, has been thought to be relevant to its pathogenesis. To investigate whether B cell clonal expansion also occurs in HIV-1-infected patients, we examined the expressed V(H)DJ(H) gene sequences of peripheral B cells in HIV-1-infected patients with hypergammaglobulinemia. Identical V(H)DJ(H) gene rearrangements with additional nucleotide differences in V(H) genes were analyzed as a marker of clonally related B cells. From healthy individuals and HIV-1-uninfected patients with hypergammaglobulinemia, clonally related B cells were detected in none of 10 (0%) and 2 of 10 (20%), respectively. No clonally related B cells were detected in any of the nine HIV-1-infected patients with detectable viral loads and normal Ig levels (0%). In contrast, from 9 of 14 HIV-1-infected patients with hypergammaglobulinemia (64%), clonally related B cells were detected. In addition, no HIV-1-infected patients who exhibited normal Ig levels after antiretroviral therapy had clonally related B cells. These findings suggest that B cell clonal expansion is present in HIV-1-infected patients with hypergammaglobulinemia.

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

The life cycle of human immunodeficiency virus type 1 (HIV-1) is intricately related to the activation state of the host cells supporting viral replication. Although cellular activation is essential to mount an effective host immune response to invading pathogens, paradoxically the marked systemic immune activation that accompanies HIV-1 infection in vivo may play an important role in sustaining phenomenal rates of HIV-1 replication in infected persons. Moreover, by inducing CD4+ cell loss by apoptosis, immune activation may further be central to the increased rate of CD4+ cell turnover and eventual development of CD4+ lymphocytopenia. In addition to HIV-1-induced immune activation, exogenous immune stimuli such as opportunistic infections may further impact the rate of HIV-1 replication systemically or at localized anatomical sites. Such stimuli may also lead to genotypic and phenotypic changes in the virus pool. Together, these various immunological effects on the biology of HIV-1 may potentially enhance disease progression in HIV-infected persons and may ultimately outweigh the beneficial aspects of antiviral immune responses. This may be particularly important for those living in developing countries, where there is little or no access to antiretroviral drugs and where frequent exposure to pathogenic organisms sustains a chronically heightened state of immune activation. Moreover, immune activation associated with sexually transmitted diseases, chorioamnionitis, and mastitis may have important local effects on HIV-1 replication that may increase the risk of sexual or mother-to-child transmission of HIV-1. The aim of this paper is to provide a broad review of the interrelationship between immune activation and the immunopathogenesis, transmission, progression, and treatment of HIV-1 infection in vivo.

Lack of evidence for small intestinal mucosal T-cell activation as a pathogenic mechanism in African HIV-associated enteropathy

The role of mucosal T-cell activation in HIV-associated enteropathy is uncertain. Twenty Zambian patients with AIDS and chronic diarrhea were studied, as were nine controls. Distal duodenal biopsies were taken at endoscopy. Morphometric analysis and dual color immunofluorescence staining were performed. Villous height was reduced [177 (118-228) vs 305 (244-358) microm P = 0.002] and crypt depth increased [220 (164-202) vs 194 (164-202) microm P = 0.008] in AIDS patients compared to controls. CD3+CD4+ T cells were reduced in AIDS patients compared to controls [12.9 (5.7-25.2) vs 47.6 (33.4-65.5)% P = 0.04]. There was no significant difference in expression of CD8, CD25, CD69, HML-1, or HLA-DR on T cells between the AIDS patients and controls, with the exception of CD3+HML-1+ cells, which were increased in AIDS patients (P = 0.05). Small intestinal T-cell activation was similar between AIDS patients and controls. We conclude, therefore, that this mechanism is not likely to be important in the pathogenesis of HIV-associated enteropathy.

Detection of viral RNA in CD4(-)CD8(-) and CD4(-)CD8(+) lymphocytes in vivo in rhesus monkeys infected with simian immunodeficiency virus of macaques

A definition of the specific cell types that support HIV replication early in the course of infection will be important for understanding AIDS pathogenesis and designing strategies for preventing infection. Observations have indicated that the population of lymphocytes susceptible to productive infection extends beyond activated CD4(+) T cells. To explore this issue, we have employed laser scanning cytometry technology and the techniques of lymphocyte surface immunophenotyping followed by fluorescent in situ hybridization to detect simian immunodeficiency virus of macaques (SIVmac) RNA in phenotypically defined rhesus monkey lymphocytes. The immunophenotype of productively infected cells in either a rhesus monkey T cell line or in PBMCs infected in vitro with SIVmac was remarkably similar to that observed in productively infected PBMCs obtained from monkeys during primary infection. We observed low levels or no detectable expression of CD4 on cells infected in vitro or on PBMCs of infected monkeys. However, a substantial number of SIVmac-infected PBMCs both in cultured lymphocytes and sampled directly from infected monkeys expressed CD8 but not CD4. These observations are consistent with the possibility that the CD4 molecule may be modulated off the surface of CD4(+)CD8(-) or CD4(+)CD8(+) lymphocytes after infection or that infection occurred via a CD4-independent mechanism. Moreover, there was no preferential expression of CD25 on cells positive for SIVmac RNA, which might have been predicted if replication of the virus was occurring selectively in activated lymphocytes. These results broaden the range of lymphocytes that support productive SIVmac infection to include CD4(-)CD8(-) and CD4(-)CD8(+) subsets, and are consistent with virus replication occurring in nonactivated cells.

Effect of HIV-1 infection on lymphocyte proliferation in gut-associated lymphoid tissue

OBJECTIVE

To determine the change in the percentage of proliferative and activated lymphocytes in gut-associated lymphoid tissue (GALT) in HIV-1-infected subjects compared with that in uninfected controls.

METHODS

We measured the percentage of proliferative (Ki-67+) and activated (CD-69+, HLA-DR+, CD45RO+) lymphocytes from GALT and peripheral blood in chronically HIV-1-infected (12) and uninfected (9) individuals.

RESULTS

The percentage of proliferative GALT CD4+ T cells was increased in HIV-1-infected control subjects compared with that in uninfected controls (p <.007). Based on immunohistochemical staining, proliferative T cells were principally located in the parafollicular area surrounding lymphoid aggregates. The percentage of activated GALT lymphocytes, however, was not significantly different in HIV-1-infected individuals, whereas it was significantly increased in the peripheral blood of HIV-1-infected individuals. The percentage of peripheral blood lymphocytes trafficking to the intestine was also not significantly different in HIV-1-infected individuals compared with that in uninfected controls.

CONCLUSIONS

CD4+ T cell proliferation in GALT is increased in HIV-1 infection without a significant alteration in the percentage of peripheral blood T cells trafficking to the gastrointestinal mucosa.

V3 induces in human normal cell populations an accelerated macrophage-mediated proliferation--apoptosis phenomenon of effector T cells when they respond to their cognate antigen

The semi-conserved domain of V3 of HIV-1 was synthesised in a lipopeptide form to be presented on the surface of liposome particles. Composite liposomes were constructed with entrapped tetanus toxoid as a recall antigen (lipo-V3/TT liposomes) to study the influence of V3 on effector T cells of human normal peripheral lymphocyte populations. We demonstrated that lipo-V3/TT liposomes induce a V3-specific response characterised by an early, enhanced proliferation of effector CD4+ T cells, followed by a sharp apoptosis. The phenomenon required the presence of monocyte-derived macrophages and CD4+ T cells, but it was qualitatively and quantitatively distinct from the normal soluble antigen-mediated antigen presenting cell: T cell interaction. Presence of the beta-chemokine RANTES in the culture medium inhibited the phenomenon, suggesting that V3 plays a costimulatory role that involves the chemokine receptor CCR5 pathway during the process of antigen presentation to T cells. This observation may be very important if it occurs also in HIV-1 infection, as it may explain the selective and progressive depletion of non-infected effector CD4+ T cells.

Placebo-controlled trial of prednisone in advanced HIV-1 infection

OBJECTIVE

To examine the safety and the immunologic and virologic consequences of corticosteroid use in HIV-1 infection.

METHODS

A randomized, double-blinded, placebo-controlled trial of corticosteroid administration in 41 patients with advanced HIV-1 infection. Patients had a baseline median CD4 cell count of 131 x 10(6) cells/l at enrollment and 85% had a history of opportunistic infection. All but one of the patients had been taking stable antiretroviral regimen, including a protease inhibitor in 36, for a median duration of 158 days. Patients were randomized to 8 weeks of prednisone 0.5 mg/kg daily or placebo.

RESULTS

No AIDS-defining events occurred; two patients in each group developed oral candidiasis, and two patients on prednisone developed mild herpes simplex flares. None who developed oral candidiasis or herpes simplex was receiving prophylaxis and each responded promptly to therapy. In the prednisone group, two patients developed hyperglycemia and one diabetic increased insulin requirements. CD4 cell counts and plasma HIV-1 RNA levels did not change, but plasma tumor necrosis factor alpha levels and CD38+ CD8+ cells decreased significantly in those taking prednisone.

CONCLUSION

Short-term prednisone administration is well tolerated and reasonably safe in advanced HIV-1 disease and decreases immune activation without effects on HIV-1 RNA levels or CD4 cell counts. These results suggest that, in stable HIV-1 disease, these immune activation markers are more likely consequences of but not inducers of HIV-1 replication.

Differential susceptibility of resting CD4(+) T lymphocytes to a T-tropic and a macrophage (M)-tropic human immunodeficiency virus type 1 is associated with their surface expression of CD38 molecules

Recent evidence has accumulated which definitively shows that chemokine receptors CCR5 and CXCR4 play an essential role as coreceptors for human immunodeficiency virus type 1 (HIV-1) infection. Flow cytometric analysis permitted us to detect CD38, a surface marker of early differentiation, as well as activation of T cells, on about half of healthy donor-derived CD4(+) T cells. In this study, we focused on the susceptibility of CD38(+) and CD38(-) subsets of CD4(+) T cells to HIV-1 infection with different coreceptor tropisms. About 20% of peripheral blood mononuclear cell-derived resting CD4(+) T cells were recovered into the CD38(+) subset fraction by panning with a monoclonal antibody to CD38. Most of the cells in this CD38(high) fraction also expressed CD45RA and CD62L at higher intensities compared with those of CD38(low) fraction. CCR5(+) T cells predominated in the CD38(-) subset, although cell surface expression of CD4 and CXCR4 was almost similar between both subsets. This difference was consistent with a significantly higher susceptibility of the CD38(-) subset to a macrophage (M)-tropic HIV-1 strain. In contrast, it was shown that a T-tropic strain of HIV-1 could replicate more efficiently in the CD38(+) subset, although viral adsorption rates were similar between both subsets. Thus, the differential susceptibility of CD4(+) T cells to M(-) and T-tropic HIV-1 was associated with their surface expression of CD38.

Selective transmission of R5-tropic HIV type 1 from dendritic cells to resting CD4+ T cells

In an in vitro coculture model of monocyte-derived, cultured human dendritic cells (DC) with autologous CD4(+) resting T cells, CCR5 (R5)-tropic strains of HIV-1, but not CXCR4 (X4)-tropic strains, were transmitted to resting CD4+ T cells, leading to prolific viral output, although DC were susceptible to infection with either strain. Macrophages, which were also infectable with either R5- or X4-tropic strains, did not transmit infection to CD4+ cells. Highly productive HIV infection in this model appeared to be a consequence of heterokaryotic syncytium formation between infected DC and T cells since syncytia formation developed only in R5-infected DC/CD4+ cocultures. These results suggested that the unique microenvironment derived from the fusion between the infected DC and CD4+ cell was highly permissive and selective for replication of R5-tropic viruses. The apparent selectivity for R5-tropic strains in such syncytia was attributable neither to differential DC-mediated activation nor to selective modulation of induction of alpha- or beta-chemokines in the infected DC. This model of HIV replication may provide useful insights into in vitro correlates of HIV pathogenicity.