Acutely dysregulated, chronically disabled by the enemy within: T-cell responses to HIV-1 infection

Hepatocellular cancer therapy in patients with HIV infection: Disparities in cancer care, trials enrolment, and cancer-related research

In the highly active antiretroviral therapy (HAART) era, hepatocellular carcinoma (HCC) is arising as a common late complication of human immunodeficiency virus (HIV) infection, with a great impact on morbidity and mortality. Though HIV infection alone may not be sufficient to promote hepatocarcinogenesis, the complex interaction of HIV with hepatitis is a main aspect influencing HCC morbidity and mortality.

Data about sorafenib effectiveness and safety in HIV-infected patients are limited, particularly for patients who are on HAART. However, in properly selected subgroups, outcomes may be comparable to those of HIV-uninfected patients. Scarce data are available for those other systemic treatments, either tyrosine kinase inhibitors, as well as immune checkpoint inhibitors (ICIs), which have been added to our therapeutic armamentarium. This review examines the influence of HIV infection on HCC development and natural history, summarizes main data on systemic therapies, offers some insight into possible mechanisms of T cell exhaustion and reversal of HIV latency with ICIs and issues about clinical trials enrollment. Nowadays, routine exclusion of HIV-infected patients from clinical trial participation is totally inappropriate, since it leaves a number of patients deprived of life-prolonging therapies.

Mathematical Analysis of Viral Replication Dynamics and Antiviral Treatment Strategies: From Basic Models to Age-Based Multi-Scale Modeling

Viral infectious diseases are a global health concern, as is evident by recent outbreaks of the middle east respiratory syndrome, Ebola virus disease, and re-emerging zika, dengue, and chikungunya fevers. Viral epidemics are a socio-economic burden that causes short- and long-term costs for disease diagnosis and treatment as well as a loss in productivity by absenteeism. These outbreaks and their socio-economic costs underline the necessity for a precise analysis of virus-host interactions, which would help to understand disease mechanisms and to develop therapeutic interventions. The combination of quantitative measurements and dynamic mathematical modeling has increased our understanding of the within-host infection dynamics and has led to important insights into viral pathogenesis, transmission, and disease progression. Furthermore, virus-host models helped to identify drug targets, to predict the treatment duration to achieve cure, and to reduce treatment costs. In this article, we review important achievements made by mathematical modeling of viral kinetics on the extracellular, intracellular, and multi-scale level for Human Immunodeficiency Virus, Hepatitis C Virus, Influenza A Virus, Ebola Virus, Dengue Virus, and Zika Virus. Herein, we focus on basic mathematical models on the population scale (so-called target cell-limited models), detailed models regarding the most important steps in the viral life cycle, and the combination of both. For this purpose, we review how mathematical modeling of viral dynamics helped to understand the virus-host interactions and disease progression or clearance. Additionally, we review different types and effects of therapeutic strategies and how mathematical modeling has been used to predict new treatment regimens.

Elevated inflammatory cytokines in aqueous cytokine profile in HIV-1 infected patients with cataracts in Uganda

BACKGROUND

Cataracts occur earlier among HIV-infected adults and this is attributed to various intraocular inflammatory processes that result in early degeneration. In this study we purposed to investigate whether HIV infected individuals with cataracts develop heightened intraocular inflammatory processes compared to their HIV negative counterparts by determining the concentration of 8 cytokines in the aqueous humour of HIV-positive adults with cataracts and their HIV-negative counterparts.

METHODS

A cross-sectional study was conducted among consecutive adults with cataracts that were operated in an ophthalmology surgical camp in western Uganda. We determined levels of Granulocyte macrophage stimulating factor (GM-CSF), interleukin 6 (IL-6), interleukin 8 (IL-8), tumour necrotic factor alpha (TNF-a), interferon gamma (IFN-g), interleukin 4 (IL-4), interleukin 2 (IL-2), and interleukin (IL-10) in the aqueous fluid using a multiplexed cytokine analysis. Data was entered in the SPSS version 10 and analyzed using STATA statistical software version 7.0. Categorical and continuous variables were compared using the χ2 test, Fisher's exact test and the Student's t-test. Bonferroni correction was used to cater for multiple comparison of p values for the various cytokines.

RESULTS

The 50 adults that underwent cataract surgery were outdoor peasants with similar exposure hours to UV radiation. The HIV-positive patients were younger {median age 43 years (SD 11.741)} compared to the HIV -negative patients {median age 66.5 years (SD 21.4)}. The mean CD4+ T cell count of the HIV-positive patients was 161 cells /mm3, and 12(48%) had started anti-retroviral therapy (ART). Pro inflammatory cytokines, GM-CSF, IL-8 and IL-10 were significantly higher among HIV-positive individuals (p = 0.001, 0.030, < 0.001 respectively). HIV-positive individuals on ART also showed significantly higher levels of GM-CSF, IL-8 and IL - 10 (p = 0.002, 0.021, < 0.001 respectively). TNF-a and IL-4 were significantly higher among those with a CD4+ T cell count greater than 200cells/mm3 compared to those with CD4+ T cell count less than 200 cells/mm3 (p = 0.022, 0.032 respectively).

CONCLUSION

Cataracts among HIV-positive adults were associated with higher intraocular inflammation relative to the healthy elderly individuals with cataracts. There is need to explore the potential role of intra-ocular anti-inflammatory agents in the management of cataracts among HIV positive patients.

The Immune Interaction between HIV-1 Infection and Mycobacterium tuberculosis

The modulation of tuberculosis (TB)-induced immunopathology caused by human immunodeficiency virus (HIV)-1 coinfection remains incompletely understood but underlies the change seen in the natural history, presentation, and prognosis of TB in such patients. The deleterious combination of these two pathogens has been dubbed a "deadly syndemic," with each favoring the replication of the other and thereby contributing to accelerated disease morbidity and mortality. HIV-1 is the best-recognized risk factor for the development of active TB and accounts for 13% of cases globally. The advent of combination antiretroviral therapy (ART) has considerably mitigated this risk. Rapid roll-out of ART globally and the recent recommendation by the World Health Organization (WHO) to initiate ART for everyone living with HIV at any CD4 cell count should lead to further reductions in HIV-1-associated TB incidence because susceptibility to TB is inversely proportional to CD4 count. However, it is important to note that even after successful ART, patients with HIV-1 are still at increased risk for TB. Indeed, in settings of high TB incidence, the occurrence of TB often remains the first presentation of, and thereby the entry into, HIV care. As advantageous as ART-induced immune recovery is, it may also give rise to immunopathology, especially in the lower-CD4-count strata in the form of the immune reconstitution inflammatory syndrome. TB-immune reconstitution inflammatory syndrome will continue to impact the HIV-TB syndemic.

CD127 Expression in Naive and Memory T Cells in HIV Patients Who Have Undergone Long-Term HAART

OBJECTIVE

To evaluate cluster of differentiation (CD)127 expression in T cells of patients with HIV-1 and the relationship of CD127 expression with disease progression.

METHODS

We divided 139 patients infected with human immunodeficiency virus type 1 (HIV-1) who had undergone highly active antiretroviral therapy (HAART) into 3 groups: patients with poor recovery (CD4⁺T < 350/μ;L, patients with general recovery (CD4⁺T =  350 - ∼600/μL) and patients with good recovery (CD4⁺T > 600/μL). Counts and percentages of naïve (CD45RA⁺) and memory (CD45RO⁺) T cells and CD127 expression were determined using flow cytometry.

RESULTS

CD4⁺CD45RO⁺, CD4⁺CD45RA⁺, CD4⁺ CD45RO⁺ CD127⁺, and CD4⁺CD45RA⁺CD127⁺T-cell counts in patients with good recovery were higher than in patients with poor recovery and those with general recovery patients (P <.05). Percentages of CD45RO⁺ were increased, and percentages of CD45RA⁺ and CD127 in T cells were decreased in patients with poor and general recovery (P <.05). CD127 values were positively correlated with CD4⁺T-cell counts and percentages of CD45RA⁺ subsets (P <.05).

CONCLUSION

CD127 expression in T cells is decreased in patients with HIV-1 and is related to recovery of CD4⁺T-cell counts and to naïve subsets.

Overview of Infections in the Immunocompromised Host

Understanding the components of the immune system that contribute to host defense against infection is key to recognizing infections that are more likely to occur in an immunocompromised patient. In this review, we discuss the integrated system of physical barriers and of innate and adaptive immunity that contributes to host defense. Specific defects in the components of this system that predispose to particular infections are presented. This is followed by a review of primary immunodeficiency diseases and secondary immunodeficiencies, the latter of which develop because of a specific illness or condition or are treatment-related. The effects of treatment for neoplasia, autoimmune diseases, solid organ and stem cell transplants on host defenses are reviewed and associated with susceptibility to particular infections. In conclusion, an approach to laboratory screening for a suspected immunodeficiency is presented. Knowledge of which host defects predispose to specific infections allows clinicians to prevent, diagnose, and manage infections in their immunocompromised patients most effectively.

Comparison of the specificities of IgG, IgG-subclass, IgA and IgM reactivities in African and European HIV-infected individuals with an HIV-1 clade C proteome-based array

A comprehensive set of recombinant proteins and peptides of the proteome of HIV-1 clade C was prepared and purified and used to measure IgG, IgG-subclass, IgA and IgM responses in HIV-infected patients from Sub-Saharan Africa, where clade C is predominant. As a comparison group, HIV-infected patients from Europe were tested. African and European patients showed an almost identical antibody reactivity profile in terms of epitope specificity and involvement of IgG, IgG subclass, IgA and IgM responses. A V3-peptide of gp120 was identified as major epitope recognized by IgG₁>IgG₂ = IgG₄>IgG₃, IgA>IgM antibodies and a C-terminal peptide represented another major peptide epitope for the four IgG subclasses. By contrast, gp41-derived-peptides were mainly recognized by IgG₁ but not by the other IgG subclasses, IgA or IgM. Among the non-surface proteins, protease, reverse transcriptase+RNAseH, integrase, as well as the capsid and matrix proteins were the most frequently and strongly recognized antigens which showed broad IgG subclass and IgA reactivity. Specificities and magnitudes of antibody responses in African patients were stable during disease and antiretroviral treatment, and persisted despite severe T cell loss. Using a comprehensive panel of gp120, gp41 peptides and recombinant non-surface proteins of HIV-1 clade C we found an almost identical antibody recognition profile in African and European patients regarding epitopes and involved IgG-sublass, IgA- and IgM-responses. Immune recognition of gp120 peptides and non-surface proteins involved all four IgG subclasses and was indicative of a mixed Th1/Th2 immune response. The HIV-1 clade C proteome-based test allowed diagnosis and monitoring of antibody responses in the course of HIV-infections and assessment of isotype and subclass responses.

Programmed death-1 is a marker for abnormal distribution of naive/memory T cell subsets in HIV-1 infection

Chronic activation of T cells is a hallmark of HIV-1 infection and plays an important role in disease progression. We previously showed that the engagement of the inhibitory receptor programmed death (PD)-1 on HIV-1-specific CD4(+) and CD8(+) T cells leads to their functional exhaustion in vitro. However, little is known about the impact of PD-1 expression on the turnover and maturation status of T cells during the course of the disease. In this study, we show that PD-1 is upregulated on all T cell subsets, including naive, central memory, and transitional memory T cells in HIV-1-infected subjects. PD-1 is expressed at similar levels on most CD4(+) T cells during the acute and the chronic phase of disease and identifies cells that have recently entered the cell cycle. In contrast, PD-1 expression is dramatically increased in CD8(+) T cells during the transition from acute to chronic infection, and this is associated with reduced levels of cell proliferation. The failure to downregulate expression of PD-1 in most T cells during chronic HIV-1 infection is associated with persistent alterations in the distribution of T cell subsets and is associated with impaired responses to IL-7. Our findings identify PD-1 as a marker for aberrant distribution of T cell subsets in HIV-1 infection.

Arginase activity in the blood of patients with visceral leishmaniasis and HIV infection

Background

Visceral leishmaniasis is a parasitic disease associated with high mortality. The most important foci of visceral leishmaniasis in Ethiopia are in the Northwest and are predominantly associated with high rates of HIV co-infection. Co-infection of visceral leishmaniasis patients with HIV results in higher mortality, treatment failure and relapse. We have previously shown that arginase, an enzyme associated with immunosuppression, was increased in patients with visceral leishmaniasis and in HIV seropositive patients; further our results showed that high arginase activity is a marker of disease severity. Here, we tested the hypothesis that increased arginase activities associated with visceral leishmaniasis and HIV infections synergize in patients co-infected with both pathogens.

Methodology/Principal Findings

We recruited a cohort of patients with visceral leishmaniasis and a cohort of patients with visceral leishmaniasis and HIV infection from Gondar, Northwest Ethiopia, and recorded and compared their clinical data. Further, we measured the levels of arginase activity in the blood of these patients and identified the phenotype of arginase-expressing cells. Our results show that CD4⁺ T cell counts were significantly lower and the parasite load in the spleen was significantly higher in co-infected patients. Moreover, our results demonstrate that arginase activity was significantly higher in peripheral blood mononuclear cells and plasma of co-infected patients. Finally, we identified the cells-expressing arginase in the PBMCs as low-density granulocytes.

Conclusion

Our results suggest that increased arginase might contribute to the poor disease outcome characteristic of patients with visceral leishmaniasis and HIV co-infection.

Visceral leishmaniasis (VL) in Ethiopia is caused by the parasite Leishmania donovani. This disease has one of the highest mortality rates: if left untreated, it is almost always fatal. VL belongs to the most neglected tropical diseases, affecting the poorest populations, for whom access to diagnosis and effective treatment are often not available. VL is worsened when the patients are co-infected with HIV. We have recently shown that patients with visceral leishmaniasis (VL patients) and HIV seropositive patients (HIV+ patients) have increased levels of an enzyme, arginase, in their blood. This enzyme has been shown to prevent cells of the immune system from mounting an efficient response and controlling the replication of the virus in HIV+ patients or the parasites in VL patients. In this study, we show that arginase is considerably higher in the blood of VL/HIV co-infected patients as compared to VL patients. Our results suggest that this abnormally high arginase might contribute to the poor prognosis associated to VL/HIV patients.

Expression of interleukin-15 and interleukin-15Rα in monocytes of HIV type 1-infected patients with different courses of disease progression

Interleukin-15 (IL-15) enhances the effector mechanisms of anti-HIV immune responses and thus is considered a potential adjuvant of HIV-1 vaccine. However, there are a lack of data concerning the relationships between IL-15 expression and regulation in HIV-1-infected patients and the course of disease progression. We found that IL-15, but not IL-15Rα, is expressed at significantly higher levels in the CD14(+) monocytes [stimulated or not with interferon (IFN)-γ] of long-term nonprogressors (LTNP) than in those of HIV-1 progressors or healthy controls. There was no between-group difference in the amounts of soluble IL-15 released from the cells. We also found that like the healthy controls, the LTNP expressed the IL-15 and IL-15Rα genes in a more coordinated manner than the progressors. Our findings show that there are significant differences in IL-15 expression between patients with different courses of HIV infection, and that the coordinated expression of the IL-15 and IL-15Rα genes is dysregulated in patients with progressive disease. They also provide important information concerning the mechanisms of infection and the potential use of IL-15 as a therapeutic agent.

Loss of CD127 & increased immunosenescence of T cell subsets in HIV infected individuals

Background & objectives:

HIV infection is characterized by a perturbation in T cell homeostasis, leading to alteration in T cell subsets. In addition to alteration in differentiation, HIV infection also leads to change in T cell survival and regenerative capacity, as suggested by differential expression of CD127 and CD57. We evaluated the expression patterns of CD127 and CD57 on CD4 and CD8 effector, memory and naïve T cell subsets in HIV-infected and uninfected individuals.

Methods:

We characterized T cell subsets based on expression of these markers, and compared their expression pattern in HIV infected subjects and uninfected controls. We further assessed therapy generated changes in these subsets and expression of CD127 and CD57 on them.

Results:

There was a generalized decrease in naïve CD4 and CD8 T cells in HIV infected subjects. These changes in T cell subset distribution were related to antigen load. CD127 expression was significantly reduced in T cells from HIV infected subject. In association to this, HIV infected subjects had higher percentage of T cell subsets expressing CD57. Increased CD57 and reduced CD127 expression correlated with plasma viraemia and CD8 T cell activation state. Incomplete restoration of T cell subset proportions was observed, despite suppression of viral replication and increase in CD4 T cell counts. Further, the improvement was more pronounced in CD127 expression.

Interpretation & conclusions:

HIV infected subjects have reduced T cell regenerative capacity along with increased senescence, highlighting decreased proliferation and effector activities.

Responsiveness of HIV-specific CD4 T cells to PD-1 blockade

Defining the T helper functions impaired by programmed death-1 (PD-1) is crucial for understanding its role in defective HIV control and determining the therapeutic potential of targeting this inhibitory pathway. We describe here the relationships among disease stage, levels of PD-1 expression, and reversibility of CD4 T-cell impairment. PD-L1 blockade in vitro enhanced HIV-specific production of Th0 (IL-2), Th1 (IFN-γ), Th2 (IL-13), and TFH (IL-21) cytokines by CD4 T cells. PD-L1 blockade caused an early increase in cytokine transcription and translation that preceded cell proliferation. Although the impact of PD-L1 blockade on cytokine expression and, to a lesser extent, cell proliferation was associated with markers of disease progression, restoration of cytokine secretion was also observed in most subjects with undetectable viremia. PD-L1 blockade restored cytokine secretion in both PD-1intermediate and PD-1high sorted CD4 T-cell subsets. Compared with PD-1high HIV-specific CD8 T cells, PD-1high HIV-specific CD4 T cells showed lower expression of the inhibitory molecules CD160 and 2B4, demonstrating marked differences in expression of inhibitory receptors between T-cell subsets. These data show that PD-1 impairs HIV-specific T helper responses both by limiting expansion of these cells and by inhibiting effector functions of multiple differentiated CD4 T-cell subsets.

R5-SHIV induces multiple defects in T cell function during early infection of rhesus macaques including accumulation of T reg cells in lymph nodes

Background

HIV-1 is a pathogen that T cell responses fail to control. HIV-1gp120 is the surface viral envelope glycoprotein that interacts with CD4 T cells and mediates entry. HIV-1gp120 has been implicated in immune dysregulatory functions that may limit anti-HIV antigen-specific T cell responses. We hypothesized that in the context of early SHIV infection, immune dysregulation of antigen-specific T-effector cell and regulatory functions would be detectable and that these would be associated or correlated with measurable concentrations of HIV-1gp120 in lymphoid tissues.

Methods

Rhesus macaques were intravaginally inoculated with a Clade C CCR5-tropic simian-human immunodeficiency virus, SHIV-1157ipd3N4. HIV-1gp120 levels, antigen-specificity, levels of apoptosis/anergy and frequency and function of Tregs were examined in lymph node and blood derived T cells at 5 and 12 weeks post inoculation.

Results/Conclusions

We observed reduced responses to Gag in CD4 and gp120 in CD8 lymph node-derived T cells compared to the peripheral blood at 5 weeks post-inoculation. Reduced antigen-specific responses were associated with higher levels of PD-1 on lymph node-derived CD4 T cells as compared to peripheral blood and uninfected lymph node-derived CD4 T cells. Lymph nodes contained increased numbers of Tregs as compared to peripheral blood, which positively correlated with gp120 levels; T regulatory cell depletion restored CD8 T cell responses to Gag but not to gp120. HIV gp120 was also able to induce T regulatory cell chemotaxis in a dose-dependent, CCR5-mediated manner. These studies contribute to our broader understanding of the ways in which HIV-1 dysregulates T cell function and localization during early infection.

Telomerase and primary T cells: biology and immortalization for adoptive immunotherapy

Telomeres are specialized repeats, present at the end of chromosomes, whose loss during cell division is followed by growth arrest, a central mechanism of replicative senescence in human cells. Telomere length in stem cells is maintained by telomerase, a specialized reverse transcriptase, whose function is to restore shortening telomeres. Unlike most somatic cell types, human T lymphocytes are capable of briefly reactivating telomerase expression at the time of stimulation. Telomerase expression in T lymphocytes is modulated by a variety of external stimuli and by viral infections. However, telomerase reactivation in stimulated, proliferating human T lymphocytes is limited and cannot prevent the ultimate onset of senescence. Ectopic telomerase expression can rescue human and macaque antigen-specific T cells from senescence. Primary T cells have been engineered with telomerase to have substantially extended replicative lifespans without the loss of primary cell functions or malignant transformation. 'Immortal' antigen-specific T-cell lines and clones overexpressing telomerase are an invaluable source of well-characterized quasi-primary T cells for research of T-cell biology and are potentially useful for immunotherapy of cancer and AIDS.

T cell-, interleukin-12-, and gamma interferon-driven viral clearance in measles virus-infected brain tissue

Genetic studies with immunocompetent mice show the importance of both T cells and gamma interferon (IFN-γ) for survival of a measles virus (MV) challenge; however, the direct role of T cells and IFN-γ within the MV-infected brain has not been addressed. Organotypic brain explants represent a successful ex vivo system to define central nervous system (CNS)-specific mechanisms of leukocyte migration, activation, and MV clearance. Within the heterogeneous, brain-derived, primed leukocyte population which reduced MV RNA levels in brain explants by 60%, CD3 T cells are the active antiviral cells, as purified CD3-positive cells are highly antiviral and CD3-negative leukocytes are unable to reduce the viral load. Neutralization of CCL5 and CXCL10 decreases leukocyte migration to areas of infection by 70%. However, despite chemokines directing the migration of T cells to infected neurons, chemokine neutralization revealed that migration is not required for viral clearance, suggesting a cytokine-mediated antiviral mechanism. In accordance with our hypothesis, the ability of leukocytes to clear the virus is abrogated when explants are treated with anti-IFN-γ neutralizing antibodies. IFN-γ applied to infected slices in the absence of primed leukocytes reduces the viral load by more than 80%; therefore, in brain tissue, IFN-γ is both necessary and sufficient to clear MV. Secretion of IFN-γ is stimulated by interleukin-12 (IL-12) in the brain, as neutralization of IL-12 results in loss of antiviral activity and stimulation of leukocytes with IL-12/IL-18 enhances their immune effector function of viral clearance. MV-primed leukocytes can reduce both West Nile and mouse hepatitis viral RNAs, indicating that cytokine-mediated viral clearance occurs in an antigen-independent manner. The IFN-γ signal is transduced within the brain explant by the Jak/STAT signaling pathway, as inhibition of Jak kinases results in a loss of antiviral activity driven by either brain-derived leukocytes or recombinant IFN-γ. These results reveal that primed T cells directly act to clear MV infection of the brain by using a noncytolytic IL-12- and IFN-γ-dependent mechanism in the CNS and that this mechanism relies upon Jak/STAT signaling.

T lymphocytes apoptosis and mitochondrial membrane potential in Down's syndrome

The increased susceptibility to infection, malignancies, and autoimmune disease, suggest that immunodeficiency is an integral part of Down's syndrome (DS). Little is known about the mitochondrial damage and tendency to apoptosis in peripheral T lymphocyte cells in DS. We studied 30 children with DS and 30 normal children, 15 of each group having no evidence of acute infection and 15 with acute infection. Potential apoptosis and membrane mitochondrial potential (MMP) were measured by flow cytometry. T lymphocytes in peripheral blood from DS patients do not display an increased tendency to undergo apoptosis, although a significant loss of MMP was found.

Low postseroconversion CD4 count and rapid decrease of CD4 density identify HIV+ fast progressors

CD4 expression in HIV replication is paradoxical: HIV entry requires high cell-surface CD4 densities, but replication requires CD4 down-modulation. However, is CD4 density in HIV+ patients affected over time? Do changes in CD4 density correlate with disease progression? Here, we examined the role of CD4 density for HIV disease progression by longitudinally quantifying CD4 densities on CD4+ T cells and monocytes of ART-naive HIV+ patients with different disease progression rates. This was a retrospective study. We defined three groups of HIV+ patients by their rate of CD4+ T cell loss, calculated by the time between infection and reaching a CD4 level of 200 cells/microl: fast (<7.5 years), intermediate (7.5-12 years), and slow progressors (>12 years). Mathematical modeling permitted us to determine the maximum CD4+ T cell count after HIV seroconversion (defined as "postseroconversion CD4 count") and longitudinal profiles of CD4 count and density. CD4 densities were quantified on CD4+ T cells and monocytes from these patients and from healthy individuals by flow cytometry. Fast progressors had significantly lower postseroconversion CD4 counts than other progressors. CD4 density on T cells was lower in HIV+ patients than in healthy individuals and decreased more rapidly in fast than in slow progressors. Antiretroviral therapy (ART) did not normalize CD4 density. Thus, postseroconversion CD4 counts define individual HIV disease progression rates that may help to identify patients who might benefit most from early ART. Early discrimination of slow and fast progressors suggests that critical events during primary infection define long-term outcome. A more rapid CD4 density decrease in fast progressors might contribute to progressive functional impairments of the immune response in advanced HIV infection. The lack of an effect of ART on CD4 density implies a persistent dysfunctional immune response by uncontrolled HIV infection.

Increased level of arginase activity correlates with disease severity in HIV-seropositive patients

Infection with human immunodeficiency virus (HIV) results in a chronic infection that progressively impairs the immune system. Although depletion of CD4(+) T cells is frequently used to explain immunosuppression, chronicity of infection and progressive loss of CD4(+) T cells are not sufficient to fully account for immune dysregulation. Arginase-induced l-arginine deprivation is emerging as a key mechanism for the down-regulation of immune responses. Here, we hypothesized that the level of arginase activity increases with disease severity in HIV-seropositive patients. We determined the levels of arginase activity in peripheral blood mononuclear cells from HIV-seropositive patients and uninfected control participants. Our results show that peripheral blood mononuclear cells from HIV-seropositive patients with low CD4(+) T cell counts expressed statistically significantly higher levels of arginase activity, compared with patients with high CD4(+) T cell counts or uninfected control participants. Furthermore, we found a statistically significant correlation between high level of arginase activity and high viral load in HIV-seropositive patients.

Polymyositis in African HIV-infected subjects

Polymyositis in HIV-infected subjects, clinically and pathologically resemble polymyositis in non-HIV-infected subjects. We report 14 consecutive HIV-associated polymyositis cases and compare specific features with 25 polymyositis cases seen over the same 6.5 year period. The HIV-polymyositis cases were all female and compared to the polymyositis cases were younger (median age 33 years, interquartile range (IQR) 29; 37 vs. 46 years, IQR 38; 52, p=0.002), and with 4-fold lower serum creatine kinase (CK) values (median 1158 vs. 5153IU/l; p=0.019). A definite clinical improvement on prednisone therapy was documented in eight HIV-polymyositis cases and one improved with anti-retroviral therapy alone. The recognition of HIV-polymyositis which is treatable, but may present with serum CK elevations less than twofolds above normal, is clinically relevant in sub-Saharan Africa where electromyography and muscle biopsies are not readily available.

APOBEC3G expression is dysregulated in primary HIV-1 infection and polymorphic variants influence CD4+ T-cell counts and plasma viral load

OBJECTIVES

In the absence of HIV-1 virion infectivity factor (Vif), cellular cytosine deaminases such as apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3G (APOBEC3G) inhibit the virus by inducing hypermutations on viral DNA, among other mechanisms of action. We investigated the association of APOBEC3G mRNA levels and genetic variants on HIV-1 susceptibility, and early disease pathogenesis using viral load and CD4 T-cell counts as outcomes.

METHODS

Study participants were 250 South African women at high risk for HIV-1 subtype C infection. We used real-time PCR to measure the expression of APOBEC3G in HIV-negative and HIV-positive primary infection samples. APOBEC3G variants were identified by DNA re-sequencing and TaqMan genotyping.

RESULTS

We found no correlation between APOBEC3G expression levels and plasma viral loads (r = 0.053, P = 0.596) or CD4 T-cell counts (r = 0.030, P = 0.762) in 32 seroconverters. APOBEC3G expression levels were higher in HIV-negative individuals as compared with HIV-positive individuals (P < 0.0001), including matched pre and postinfection samples from the same individuals (n = 13, P < 0.0001). Twenty-four single nucleotide polymorphisms, including eight novel, were identified within APOBEC3G by re-sequencing and genotyping. The H186R mutation, a codon-changing variant in exon 4, and a 3' extragenic mutation (rs35228531) were associated with high viral loads (P = 0.0097 and P < 0.0001) and decreased CD4 T-cell levels (P = 0.0081 and P < 0.0001), respectively.

CONCLUSION

These data suggest that APOBEC3G transcription is rapidly downregulated upon HIV-1 infection. During primary infection, APOBEC3G expression levels in peripheral blood mononuclear cells do not correlate with viral loads or CD4 T-cell counts. Genetic variation of APOBEC3G may significantly affect early HIV-1 pathogenesis, although the mechanism remains unclear and warrants further investigation.

Immunopathogenesis of immune reconstitution disease in HIV patients responding to antiretroviral therapy

PURPOSE OF REVIEW

The aim of this article is to review the most recent literature regarding the immunopathogenesis of pathogen-associated immune reconstitution disease and to discuss the role of immune activation and various effector molecules and cells such as macrophages, effector and regulatory T cells, and natural killer cells in immune reconstitution disease.

RECENT FINDINGS

Many HIV patients receiving antiretroviral treatment develop immune reconstitution disease, which is characterized by exaggerated inflammatory immune responses to replicating or dead pathogens. In the majority of these cases, immune reconstitution disease is associated with restoration of pathogen-specific cellular immune responses involving CD4 or CD8 effector T cells. The precise conditions that trigger immune reconstitution disease have not yet been identified. Immune reconstitution disease patients have overt immune activation, which may be due to poor homeostatic control after the fast initial immune recovery in patients receiving antiretroviral therapy. Poor homeostatic control in immune reconstitution disease patients may be linked to unbalanced restoration of effector and regulatory T cells.

SUMMARY

Although the precise mechanism of immune reconstitution disease is not well understood, it is probably related to rapid restoration of pathogen-specific immune responses and poor homeostatic control that promote exaggerated immunopathological responses, especially if viable pathogens or pathogen debris are present at high concentrations.

XVII International AIDS Conference: From Evidence to Action - Basic science

This article focuses on the sessions in which basic science research was presented at the XVII International AIDS Conference (AIDS 2008). It also provides an analysis of basic science issues which generated significant discussion and debate at the conference and are likely to have implications for future laboratory and clinical research. Data presented at AIDS 2008 confirmed the speed with which HIV establishes latent viral reservoirs following infection and the resulting challenges to viral eradication given how effectively HIV proviral RNA inserts itself into human DNA within these reservoirs. Studies also raised questions about the source of residual viremia and how these might be targeted by novel therapeutic approaches.

Emerging concepts in the immunopathogenesis of AIDS

There is an intense interplay between HIV and the immune system, and the literature is replete with studies describing various immunological phenomena associated with HIV infection. Many of these phenomena seem too broad in scope to be attributable either to HIV-infected cells or to the HIV-specific immune response. Recently, a more fundamental understanding of how HIV affects various T cells and T cell compartments has emerged. This review covers the role of immune activation in HIV immunopathogenesis, how that activation could be mediated directly by HIV replicating within and damaging the gut mucosal barrier, how HIV affects multiple T cell functions and phenotypes, and how chronic HIV replication induces immune modulatory pathways to negatively regulate certain functions in HIV-specific T cells.

Progressive CD127 down-regulation correlates with increased apoptosis of CD8 T cells during chronic HIV-1 infection

Chronic HIV-1 infection can induce a significant decrease in CD127 expression on CD8 T cells, but the underlying mechanisms and immunological consequences are unclear. In this study, we investigated CD127 expression on CD8 T cells from a total of 51 HIV-1-infected subjects and 16 healthy individuals and analyzed the association between CD127 expression and CD8 T-cell apoptosis in these HIV-1-infected subjects. We found that CD127 expression on total CD8 T cells was significantly down-regulated, which was correlated with the increased CD8 T-cell apoptosis and disease progression of chronic HIV-1 infection. The in vitro addition of IL-7 efficiently rescued the spontaneous apoptosis of CD8 T cells from HIV-1-infected individuals. IL-7 stimulation also transiently down-regulated CD127 expression, whereas some of the CD127(-) CD8 T cells regained CD127 expression soon after IL-7 was retracted from the incubation medium. Thus, IL-7 stimulation reduced apoptosis of both CD127(+) and CD127(-)CD8 T cells to some degree. These data indicate that CD127 loss might impair IL-7 signaling and increase CD8 T-cell apoptosis during HIV-1 infection. This study, therefore, will extend the notion that IL-7 could be a good candidate for immunotherapy in HIV-1-infected patients.

IL-10 is up-regulated in multiple cell types during viremic HIV infection and reversibly inhibits virus-specific T cells

Murine models indicate that interleukin-10 (IL-10) can suppress viral clearance, and interventional blockade of IL-10 activity has been proposed to enhance immunity in chronic viral infections. Increased IL-10 levels have been observed during HIV infection and IL-10 blockade has been shown to enhance T-cell function in some HIV-infected subjects. However, the categories of individuals in whom the IL-10 pathway is up-regulated are poorly defined, and the cellular sources of IL-10 in these subjects remain to be determined. Here we report that blockade of the IL-10 pathway augmented in vitro proliferative capacity of HIV-specific CD4 and CD8 T cells in individuals with ongoing viral replication. IL-10 blockade also increased cytokine secretion by HIV-specific CD4 T cells. Spontaneous IL-10 expression, measured as either plasma IL-10 protein or IL-10 mRNA in peripheral blood mononuclear cells (PBMCs), correlated positively with viral load and diminished after successful antiretroviral therapy. IL-10 mRNA levels were up-regulated in multiple PBMC subsets in HIV-infected subjects compared with HIV-negative controls, particularly in T, B, and natural killer (NK) cells, whereas monocytes were a major source of IL-10 mRNA in HIV-infected and -uninfected individuals. These data indicate that multiple cell types contribute to IL-10-mediated immune suppression in the presence of uncontrolled HIV viremia.

Effective CD4+ T-cell restoration in gut-associated lymphoid tissue of HIV-infected patients is associated with enhanced Th17 cells and polyfunctional HIV-specific T-cell responses

Human immunodeficiency virus (HIV) infection leads to severe CD4+ T-cell depletion in gut-associated lymphoid tissue (GALT) that persists despite the initiation of highly active antiretroviral therapy (HAART). It is not known whether restoration of gut mucosal CD4+ T cells and their functions is feasible during therapy and how that relates to immune correlates and viral reservoirs. Intestinal biopsies and peripheral blood samples from HIV-infected patients who were either HAART naive or on long-term HAART were evaluated. Our data demonstrated that gut CD4+ T-cell restoration ranged from modest (<50%) to high (>50%), compared with uninfected controls. Despite persistent CD4+ T-cell proviral burden and residual immune activation in GALT during HAART, effective CD4+ T-cell restoration (>50%) was achieved, which was associated with enhanced Th17 CD4+ T-cell accumulation and polyfunctional anti-HIV cellular responses. Our findings suggest that a threshold of>50% CD4+ T-cell restoration may be sufficient for polyfunctional HIV-specific T cells with implications in the evaluation of vaccines and therapeutics.

Biomarkers of HIV Immune Reconstitution Inflammatory Syndrome

Dysregulation of the immune system drives HIV pathogenesis. As we develop new ways to treat HIV and AIDS, we encounter new clinical ramifications of our treatment on regulatory components of the immune system. HIV-associated Immune Reconstitution Inflammatory Syndrome (IRIS) occurs after initiation of anti-retroviral therapy (ART) with inappropriate and dysbalanced restoration of the immune system resulting in pathologic inflammatory reactions with significant morbidity. IRIS is most commonly associated with latent, occult, or past infections, including tuberculosis, Cryptococcus neoformans, and Mycobacterium avium-complex. We discuss common clinical presentations, new diagnostic modalities, current hypotheses of IRIS pathogenesis, and future directions of IRIS-related research, focusing on the identification of biomarkers that can be used to predict and diagnose IRIS.

Toll-like receptor expression and responsiveness are increased in viraemic HIV-1 infection

OBJECTIVES

Toll-like receptors (TLR) are important in pathogen recognition and may play a role in HIV disease. We evaluated the effect of chronic untreated and treated HIV-1 infection on systemic TLR expression and TLR signalling.

METHODS

Two hundred HIV-infected and uninfected women from a Kenya cohort participated in the studies. TLR1 to TLR10 messenger RNA expression was determined by quantitative reverse transcriptase polymerase chain reaction in peripheral blood mononuclear cells (PBMC). TLR ligand responsiveness was determined in or using ex-vivo PBMC by cytokine production in culture supernatants.

RESULTS

Chronic, untreated HIV-1 infection was significantly associated with increased mRNA expression of TLR6, TLR7, and TLR8 and when analysis was limited to those with advanced disease (CD4 cell count < 200 cells/ml) TLR2, TLR3, and TLR4 were additionally elevated. TLR expression correlated with the plasma HIV-RNA load, which was significant for TLR6 and TLR7. In vitro HIV single-stranded RNA alone could enhance TLR mRNA expression. PBMC of HIV-infected subjects also demonstrated profoundly increased proinflammatory responsiveness to TLR ligands, suggesting sensitization of TLR signalling in HIV. Finally, viral suppression by HAART was associated with a normalization of TLR levels.

CONCLUSION

Together, these data indicate that chronic viraemic HIV-1 is associated with increased TLR expression and responsiveness, which may perpetuate innate immune dysfunction and activation that underlies HIV pathogenesis, and thus reveal potential new targets for therapy.

Chronic innate immune activation as a cause of HIV-1 immunopathogenesis

Human immunodeficiency virus (HIV)-1 infection causes progressive impairment of the immune system in humans, characterized by depletion of CD4 T cells and loss of T cell function. Increased markers of T cell activation and lymphoid hyperplasia suggest that chronic T cell activation persists in immunocompromised hosts, and contributes to the exhaustion of immune functions. Here we propose a revision of this hypothesis, in which we suggest that chronic activation of innate immunity may negatively affect adaptive T cell-mediated responses. We hypothesize that constant exposure of the effector cells of innate immunity to HIV results in their chronic hyperactivation, with deleterious effects on T cells. In particular, plasmacytoid dendritic cells (pDC) may be highly susceptible to HIV-induced activation due to its interaction with the cellular receptor CD4, expressed by pDC. Subsequent production of type I interferon and indoleamine 2,3-dioxygenase may exert suppressive and cytotoxic effects on T cells.