Apoptosis of uninfected cells induced by HIV envelope glycoproteins

Humanized mice for studying HIV latency and potentially its eradication

PURPOSE OF THE REVIEW

The quest for an HIV cure faces a formidable challenge: the persistent presence of latent viral infections within the cells and tissues of infected individuals. This review provides a thorough examination of discussions surrounding HIV latency, the use of humanized mouse models, and strategies aimed at eliminating the latent HIV reservoir. It explores the hurdles and advancements in understanding HIV pathogenesis, mainly focusing on establishing latent reservoirs in CD4 + T cells and macrophages. Introducing the concepts of functional and sterile cures, the review underscores the indispensable role of humanized mouse models in HIV research, offering crucial insights into the efficacy of cART and the ongoing pursuit of an HIV cure.

RECENT FINDINGS

Here, we highlight studies investigating molecular mechanisms and pathogenesis related to HIV latency in humanized mice and discuss novel strategies for eradicating latent HIV. Emphasizing the importance of analytical cART interruption in humanized mouse studies to gauge its impact on the latent reservoir accurately, the review underlines the ongoing progress and challenges in harnessing humanized mouse models for HIV research.

SUMMARY

This review suggests that humanized mice models provide valuable insights into HIV latency and potential eradication strategies, contributing significantly to the quest for an HIV cure.

Inflammation: the driver of poor outcomes among children with severe acute malnutrition?

Severe acute malnutrition (SAM) is the most life-threatening form of undernutrition and underlies at least 10% of all deaths among children younger than 5 years in low-income countries. SAM is a complex, multisystem disease, with physiological perturbations observed in conjunction with the loss of lean mass, including structural and functional changes in many organ systems. Despite the high mortality burden, predominantly due to infections, the underlying pathogenic pathways remain poorly understood. Intestinal and systemic inflammation is heightened in children with SAM. Chronic inflammation and its consequent immunomodulation may explain the increased morbidity and mortality from infections in children with SAM, both during hospitalization and in the longer term after discharge. Recognition of the role of inflammation in SAM is critical in considering new therapeutic targets in this disease, which has not seen a transformational approach to treatment for several decades. This review highlights the central role of inflammation in the wide-ranging pathophysiology of SAM, as well as identifying potential interventions that have biological plausibility based on evidence from other inflammatory syndromes.

HIV-1 virological synapse formation enhances infection spread by dysregulating Aurora Kinase B

HIV-1 spreads efficiently through direct cell-to-cell transmission at virological synapses (VSs) formed by interactions between HIV-1 envelope proteins (Env) on the surface of infected cells and CD4 receptors on uninfected target cells. Env-CD4 interactions bring the infected and uninfected cellular membranes into close proximity and induce transport of viral and cellular factors to the VS for efficient virion assembly and HIV-1 transmission. Using novel, cell-specific stable isotope labeling and quantitative mass spectrometric proteomics, we identified extensive changes in the levels and phosphorylation states of proteins in HIV-1 infected producer cells upon mixing with CD4+ target cells under conditions inducing VS formation. These coculture-induced alterations involved multiple cellular pathways including transcription, TCR signaling and, unexpectedly, cell cycle regulation, and were dominated by Env-dependent responses. We confirmed the proteomic results using inhibitors targeting regulatory kinases and phosphatases in selected pathways identified by our proteomic analysis. Strikingly, inhibiting the key mitotic regulator Aurora kinase B (AURKB) in HIV-1 infected cells significantly increased HIV activity in cell-to-cell fusion and transmission but had little effect on cell-free infection. Consistent with this, we found that AURKB regulates the fusogenic activity of HIV-1 Env. In the Jurkat T cell line and primary T cells, HIV-1 Env:CD4 interaction also dramatically induced cell cycle-independent AURKB relocalization to the centromere, and this signaling required the long (150 aa) cytoplasmic C-terminal domain (CTD) of Env. These results imply that cytoplasmic/plasma membrane AURKB restricts HIV-1 envelope fusion, and that this restriction is overcome by Env CTD-induced AURKB relocalization. Taken together, our data reveal a new signaling pathway regulating HIV-1 cell-to-cell transmission and potential new avenues for therapeutic intervention through targeting the Env CTD and AURKB activity.

Temsavir blocks the immunomodulatory activities of HIV-1 soluble gp120

While HIV-1-mediated CD4 downregulation protects infected cells from antibody-dependent cellular cytotoxicity (ADCC), shed gp120 binds to CD4 on uninfected bystander CD4+ T cells, sensitizing them to ADCC mediated by HIV+ plasma. Soluble gp120-CD4 interaction on multiple immune cells also triggers a cytokine burst. The small molecule temsavir acts as an HIV-1 attachment inhibitor by preventing envelope glycoprotein (Env)-CD4 interaction and alters the overall antigenicity of Env by affecting its processing and glycosylation. Here we show that temsavir also blocks the immunomodulatory activities of shed gp120. Temsavir prevents shed gp120 from interacting with uninfected bystander CD4+ cells, protecting them from ADCC responses and preventing a cytokine burst. Mechanistically, this depends on temsavir's capacity to prevent soluble gp120-CD4 interaction, to reduce gp120 shedding, and to alter gp120 antigenicity. This suggests that the clinical benefits provided by temsavir could extend beyond blocking viral entry.

Molecular Mimicry of the Viral Spike in the SARS-CoV-2 Vaccine Possibly Triggers Transient Dysregulation of ACE2, Leading to Vascular and Coagulation Dysfunction Similar to SARS-CoV-2 Infection

The benefits of SARS-CoV-2 spike mRNA vaccines are well known, including a significant decline in COVID-19 morbidity and a decrease in the mortality rate of SARS-CoV-2 infected persons. However, pharmacovigilance studies have revealed the existence of rare cases of cardiovascular complications after mass vaccination using such formulations. Cases of high blood pressure have also been reported but were rarely documented under perfectly controlled medical supervision. The press release of these warning signals triggered a huge debate over COVID-19 vaccines' safety. Thereby, our attention was quickly focused on issues involving the risk of myocarditis, acute coronary syndrome, hypertension and thrombosis. Rare cases of undesirable post-vaccine pathophysiological phenomena should question us, especially when they occur in young subjects. They are more likely to occur with inappropriate use of mRNA vaccine (e.g., at the time when the immune response is already very active during a low-noise infection in the process of healing), leading to angiotensin II (Ang II) induced inflammation triggering tissue damage. Such harmful effects observed after the COVID-19 vaccine evoke a possible molecular mimicry of the viral spike transiently dysregulating angiotensin converting enzyme 2 (ACE2) function. Although the benefit/risk ratio of SARS-CoV-2 spike mRNA vaccine is very favorable, it seems reasonable to suggest medical surveillance to patients with a history of cardiovascular diseases who receive the COVID-19 vaccine.

Function-based classification of hazardous biological sequences: Demonstration of a new paradigm for biohazard assessments

Bioengineering applies analytical and engineering principles to identify functional biological building blocks for biotechnology applications. While these building blocks are leveraged to improve the human condition, the lack of simplistic, machine-readable definition of biohazards at the function level is creating a gap for biosafety practices. More specifically, traditional safety practices focus on the biohazards of known pathogens at the organism-level and may not accurately consider novel biodesigns with engineered functionalities at the genetic component-level. This gap is motivating the need for a paradigm shift from organism-centric procedures to function-centric biohazard identification and classification practices. To address this challenge, we present a novel methodology for classifying biohazards at the individual sequence level, which we then compiled to distinguish the biohazardous property of pathogenicity at the whole genome level. Our methodology is rooted in compilation of hazardous functions, defined as a set of sequences and associated metadata that describe coarse-level functions associated with pathogens (e.g., adherence, immune subversion). We demonstrate that the resulting database can be used to develop hazardous “fingerprints” based on the functional metadata categories. We verified that these hazardous functions are found at higher levels in pathogens compared to non-pathogens, and hierarchical clustering of the fingerprints can distinguish between these two groups. The methodology presented here defines the hazardous functions associated with bioengineering functional building blocks at the sequence level, which provide a foundational framework for classifying biological hazards at the organism level, thus leading to the improvement and standardization of current biosecurity and biosafety practices.

Bystander CD4 T-cell death is inhibited by broadly neutralizing anti-HIV antibodies only at levels blocking cell-to-cell viral transmission

The progressive loss of CD4+ T cells during HIV infection of lymphoid tissues involves both the apoptotic death of activated and productively infected CD4 T cells and the pyroptotic death of large numbers of resting and abortively infected bystander CD4 T cells. HIV spreads both through cellular release of virions and cell-to-cell transmission involving the formation of virological synapses. Cell-to-cell transmission results in high-level transfer of large quantities of virions to the target cell exceeding that achieved with cell-free virions. Broadly neutralizing anti-HIV antibodies (bNAbs) binding to HIV envelope protein capably block cell-free virus spread, and when added at higher concentrations can also interdict cell-to-cell transmission. Exploiting these distinct dose–response differences, we now show that four different bNAbs block the pyroptotic death of bystander cells, but only when added at concentrations sufficient to block cell-to-cell transmission. These findings further support the conclusion that HIV killing of abortively infected bystander CD4 T cells requires cell-to-cell transfer of virions. As bNAbs attract more interest as potential therapeutics, it will be important to consider the higher concentrations of these antibodies required to block the inflammatory death of bystander CD4 T cells.

Identification of novel genes involved in apoptosis of HIV-infected macrophages using unbiased genome-wide screening

Background

Macrophages, besides resting latently infected CD4+ T cells, constitute the predominant stable, major non-T cell HIV reservoirs. Therefore, it is essential to eliminate both latently infected CD4+ T cells and tissue macrophages to completely eradicate HIV in patients. Until now, most of the research focus is directed towards eliminating latently infected CD4+ T cells. However, few approaches have been directed at killing of HIV-infected macrophages either in vitro or in vivo. HIV infection dysregulates the expression of many host genes essential for the survival of infected cells. We postulated that exploiting this alteration may yield novel targets for the selective killing of infected macrophages.

Methods

We applied a pooled shRNA-based genome-wide approach by employing a lentivirus-based library of shRNAs to screen novel gene targets whose inhibition should selectively induce apoptosis in HIV-infected macrophages. Primary human MDMs were infected with HIV-eGFP and HIV-HSA viruses. Infected MDMs were transfected with siRNAs specific for the promising genes followed by analysis of apoptosis by flow cytometry using labelled Annexin-V in HIV-infected, HIV-exposed but uninfected bystander MDMs and uninfected MDMs. The results were analyzed using student’s t-test from at least four independent experiments.

Results

We validated 28 top hits in two independent HIV infection models. This culminated in the identification of four target genes, Cox7a2, Znf484, Cstf2t, and Cdk2, whose loss-of-function induced apoptosis preferentially in HIV-infected macrophages. Silencing these single genes killed significantly higher number of HIV-HSA-infected MDMs compared to the HIV-HSA-exposed, uninfected bystander macrophages, indicating the specificity in the killing of HIV-infected macrophages. The mechanism governing Cox7a2-mediated apoptosis of HIV-infected macrophages revealed that targeting respiratory chain complex II and IV genes also selectively induced apoptosis of HIV-infected macrophages possibly through enhanced ROS production.

Conclusions

We have identified above-mentioned novel genes and specifically the respiratory chain complex II and IV genes whose silencing may cause selective elimination of HIV-infected macrophages and eventually the HIV-macrophage reservoirs. The results highlight the potential of the identified genes as targets for eliminating HIV-infected macrophages in physiological environment as part of an HIV cure strategy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06346-7.

Apoptosis of Hepatocytes: Relevance for HIV-Infected Patients under Treatment

Due to medical advances over the past few decades, human immunodeficiency virus (HIV) infection, once a devastatingly mortal pandemic, has become a manageable chronic condition. However, available antiretroviral treatments (cART) cannot fully restore immune health and, consequently, a number of inflammation-associated and/or immunodeficiency complications have manifested themselves in treated HIV-infected patients. Among these chronic, non-AIDS (acquired immune deficiency syndrome)-related conditions, liver disease is one of the deadliest, proving to be fatal for 15–17% of these individuals. Aside from the presence of liver-related comorbidities, including metabolic disturbances and co-infections, HIV itself and the adverse effects of cART are the main factors that contribute to hepatic cell injury, inflammation, and fibrosis. Among the molecular mechanisms that are activated in the liver during HIV infection, apoptotic cell death of hepatocytes stands out as a key pathogenic player. In this review, we will discuss the evidence and potential mechanisms involved in the apoptosis of hepatocytes induced by HIV, HIV-encoded proteins, or cART. Some antiretroviral drugs, especially the older generation, can induce apoptosis of hepatic cells, which occurs through a variety of mechanisms, such as mitochondrial dysfunction, increased production of reactive oxygen species (ROS), and induction of endoplasmic reticulum (ER) stress and unfolded protein response (UPR), all of which ultimately lead to caspase activation and cell death.

Differential Apoptotic Responses of Hemocyte Subpopulations to White Spot Syndrome Virus Infection in Fenneropenaeus chinensis

The apoptosis of hemocytes plays an essential function in shrimp immune defense against pathogen invasions. In order to further elucidate the differential apoptotic responses of the granulocytes and the hyalinocytes in Fenneropenaeus chinensis post WSSV infection, the characteristics of apoptotic dynamics and viral proliferation in total hemocytes and hemocyte subpopulations were respectively investigated in the present work. The results showed that the apoptotic rate of hemocytes changed significantly, and the apoptosis-related genes also showed significantly differential expression responses during WSSV infection. Interestingly, we found that the apoptotic rate of virus-negative hemocytes was significantly higher than that of virus-positive hemocytes in the early stage of WSSV infection, while it was significantly lower than that of virus-positive cells in the middle and late infection stages. The difference of apoptosis between virus-positive and virus-negative hemocytes seems to be an important way for the WSSV to destroy the host’s immune system and facilitate the virus spread at different infection stages. It was further found that the apoptosis rate of granulocytes was always significantly higher than that of hyalinocytes during WSSV infection, indicating that granulocytes have a stronger apoptotic response to WSSV infection. Moreover, a higher viral load was detected in granulocytes, and the density of granulocytes decreased more rapidly post WSSV infection, indicating that the granulocytes are more susceptible and vulnerable to WSSV infection compared with the hyalinocytes. These results collectively demonstrated that the apoptotic response in shrimp hemocytes was significantly influenced by the WSSV infection, and the differential apoptotic response of granulocytes and hyalinocytes to WSSV indicated the differences of antiviral mechanisms between the two hemocyte subpopulations.

The roles of apoptosis, autophagy and unfolded protein response in arbovirus, influenza virus, and HIV infections

Virus infection induces different cellular responses in infected cells. These include cellular stress responses like autophagy and unfolded protein response (UPR). Both autophagy and UPR are connected to programed cell death I (apoptosis) in chronic stress conditions to regulate cellular homeostasis via Bcl2 family proteins, CHOP and Beclin-1. In this review article we first briefly discuss arboviruses, influenza virus, and HIV and then describe the concepts of apoptosis, autophagy, and UPR. Finally, we focus upon how apoptosis, autophagy, and UPR are involved in the regulation of cellular responses to arboviruses, influenza virus and HIV infections. Abbreviation: AIDS: Acquired Immunodeficiency Syndrome; ATF6: Activating Transcription Factor 6; ATG6: Autophagy-specific Gene 6; BAG3: BCL Associated Athanogene 3; Bak: BCL-2-Anatagonist/Killer1; Bax; BCL-2: Associated X protein; Bcl-2: B cell Lymphoma 2x; BiP: Chaperon immunoglobulin heavy chain binding Protein; CARD: Caspase Recruitment Domain; cART: combination Antiretroviral Therapy; CCR5: C-C Chemokine Receptor type 5; CD4: Cluster of Differentiation 4; CHOP: C/EBP homologous protein; CXCR4: C-X-C Chemokine Receptor Type 4; Cyto c: Cytochrome C; DCs: Dendritic Cells; EDEM1: ER-degradation enhancing-a-mannosidase-like protein 1; ENV: Envelope; ER: Endoplasmic Reticulum; FasR: Fas Receptor;G2: Gap 2; G2/M: Gap2/Mitosis; GFAP: Glial Fibrillary Acidic Protein; GP120: Glycoprotein120; GP41: Glycoprotein41; HAND: HIV Associated Neurodegenerative Disease; HEK: Human Embryonic Kidney; HeLa: Human Cervical Epithelial Carcinoma; HIV: Human Immunodeficiency Virus; IPS-1: IFN-β promoter stimulator 1; IRE-1: Inositol Requiring Enzyme 1; IRGM: Immunity Related GTPase Family M protein; LAMP2A: Lysosome Associated Membrane Protein 2A; LC3: Microtubule Associated Light Chain 3; MDA5: Melanoma Differentiation Associated gene 5; MEF: Mouse Embryonic Fibroblast; MMP: Mitochondrial Membrane Permeabilization; Nef: Negative Regulatory Factor; OASIS: Old Astrocyte Specifically Induced Substrate; PAMP: Pathogen-Associated Molecular Pattern; PERK: Pancreatic Endoplasmic Reticulum Kinase; PRR: Pattern Recognition Receptor; Puma: P53 Upregulated Modulator of Apoptosis; RIG-I: Retinoic acid-Inducible Gene-I; Tat: Transactivator Protein of HIV; TLR: Toll-like receptor; ULK1: Unc51 Like Autophagy Activating Kinase 1; UPR: Unfolded Protein Response; Vpr: Viral Protein Regulatory; XBP1: X-Box Binding Protein 1.

Differential Pathogenicity of SHIV KB9 and 89.6 Env Correlates with Bystander Apoptosis Induction in CD4+ T cells

SHIV variants KB9 and 89.6 show differential pathogenesis in primate models with KB9 causing rapid CD4 decline while 89.6 failing to induce disease. We attempted to determine whether the differential pathogenicity of KB9 versus 89.6 was a result of differential bystander apoptosis inducing potential (AIP) of the Env glycoproteins from these viruses. We find that the KB9 Env was highly potent at inducing bystander apoptosis in CD4+ target cells compared to 89.6 Env. Cell death induction by KB9 showed classical signs of apoptosis including mitochondrial depolarization, caspase activation and PARP cleavage. Inhibiting Env mediated fusion by T20 peptide inhibited KB9 mediated bystander apoptosis. KB9 and 89.6 differed in terms of co-receptor usage with 89.6 preferring CXCR4 while KB9 using both CXCR4 and CCR5 with equal efficiency. Our study suggests that higher bystander AIP of KB9 Env compared to 89.6 may be the basis for the differential pathogenesis of these viruses.

Different Patterns of HIV-1 Replication in MACROPHAGES is Led by Co-Receptor Usage

Background and objectives: To enter the target cell, HIV-1 binds not only CD4 but also a co-receptor β-chemokine receptor 5 (CCR5) or α chemokine receptor 4 (CXCR4). Limited information is available on the impact of co-receptor usage on HIV-1 replication in monocyte-derived macrophages (MDM) and on the homeostasis of this important cellular reservoir. Materials and Methods: Replication (measured by p24 production) of the CCR5-tropic 81A strain increased up to 10 days post-infection and then reached a plateau. Conversely, the replication of the CXCR4-tropic NL4.3 strain (after an initial increase up to day 7) underwent a drastic decrease becoming almost undetectable after 10 days post-infection. The ability of CCR5-tropic and CXCR4-tropic strains to induce cell death in MDM was then evaluated. While for CCR5-tropic 81A the rate of apoptosis in MDM was comparable to uninfected MDM, the infection of CXCR4-tropic NL4.3 in MDM was associated with a rate of 14.3% of apoptotic cells at day 6 reaching a peak of 43.5% at day 10 post-infection. Results: This suggests that the decrease in CXCR4-tropic strain replication in MDM can be due to their ability to induce cell death in MDM. The increase in apoptosis was paralleled with a 2-fold increase in the phosphorylated form of p38 compared to WT. Furthermore, microarray analysis showed modulation of proapoptotic and cancer-related genes induced by CXCR4-tropic strains starting from 24 h after infection, whereas CCR5 viruses modulated the expression of genes not correlated with apoptotic-pathways. Conclusions: In conclusion, CXCR4-tropic strains can induce a remarkable depletion of MDM. Conversely, MDM can represent an important cellular reservoir for CCR5-tropic strains supporting the role of CCR5-usage in HIV-1 pathogenesis and as a pharmacological target to contribute to an HIV-1 cure.

Genetic Strategies for HIV Treatment and Prevention

Conventional HIV gene therapy approaches are based on engineering HIV target cells that are non-permissive to viral replication. However, expansion of gene-modified HIV target cells has been limited in patients. Alternative genetic strategies focus on generating gene-modified producer cells that secrete antiviral proteins (AVPs). The secreted AVPs interfere with HIV entry, and, therefore, they extend the protection against infection to unmodified HIV target cells. Since any cell type can potentially secrete AVPs, hematopoietic and non-hematopoietic cell lineages can function as producer cells. Secretion of AVPs from non-hematopoietic cells opens the possibility of using a genetic approach for HIV prevention. Another strategy aims at modifying cytotoxic T cells to selectively target and eliminate infected cells. This review provides an overview of the different genetic approaches for HIV treatment and prevention.

Mechanisms for Cell-to-Cell Transmission of HIV-1

While HIV-1 infection of target cells with cell-free viral particles has been largely documented, intercellular transmission through direct cell-to-cell contact may be a predominant mode of propagation in host. To spread, HIV-1 infects cells of the immune system and takes advantage of their specific particularities and functions. Subversion of intercellular communication allows to improve HIV-1 replication through a multiplicity of intercellular structures and membrane protrusions, like tunneling nanotubes, filopodia, or lamellipodia-like structures involved in the formation of the virological synapse. Other features of immune cells, like the immunological synapse or the phagocytosis of infected cells are hijacked by HIV-1 and used as gateways to infect target cells. Finally, HIV-1 reuses its fusogenic capacity to provoke fusion between infected donor cells and target cells, and to form infected syncytia with high capacity of viral production and improved capacities of motility or survival. All these modes of cell-to-cell transfer are now considered as viral mechanisms to escape immune system and antiretroviral therapies, and could be involved in the establishment of persistent virus reservoirs in different host tissues.

HIV-1 envelope glycoprotein stimulates viral transcription and increases the infectivity of the progeny virus through the manipulation of cellular machinery

During HIV infection, large amounts of progeny viral particles, including infectious virus and a large proportion of defective viral particles, are produced. Despite of the critical role of the infectious viruses in infection and pathogenesis in vivo, whether and how those defective viral particles, especially the virus-associated envelope glycoprotein (vEnv), would impact viral infection remains elusive. In this study, we investigated the effect of vEnv on HIV-infected T cells and demonstrated that the vEnv was able to stimulate HIV transcription in HIV-infected cells, including peripheral blood mononuclear cells (PBMCs) isolated from HIV patients. This vEnv-mediated HIV transcription activation is mediated primarily through the interaction between vEnv and CD4/coreceptors (CCR5 or CXCR4). Through transcriptome analysis, we found that numerous cellular gene products involved in various signaling pathways were modulated by vEnv. Among them, we have further identified a cellular microRNA miR181A2, which is downregulated upon vEnv treatment, resulting in increased HIV LTR histone H3 acetylation and HIV transcription. Furthermore, we also found a vEnv-modulated cellular histone deacetylase, HDAC10, whose downregulation is associated with the increased infectivity of progeny viruses. Altogether, these findings provide evidence of the important role vEnv plays in modulating cellular environments and facilitating HIV expression and infection.

Host and Viral Factors in HIV-Mediated Bystander Apoptosis

Human immunodeficiency virus (HIV) infections lead to a progressive loss of CD4 T cells primarily via the process of apoptosis. With a limited number of infected cells and vastly disproportionate apoptosis in HIV infected patients, it is believed that apoptosis of uninfected bystander cells plays a significant role in this process. Disease progression in HIV infected individuals is highly variable suggesting that both host and viral factors may influence HIV mediated apoptosis. Amongst the viral factors, the role of Envelope (Env) glycoprotein in bystander apoptosis is well documented. Recent evidence on the variability in apoptosis induction by primary patient derived Envs underscores the role of Env glycoprotein in HIV disease. Amongst the host factors, the role of C-C Chemokine Receptor type 5 (CCR5), a coreceptor for HIV Env, is also becoming increasingly evident. Polymorphisms in the CCR5 gene and promoter affect CCR5 cell surface expression and correlate with both apoptosis and CD4 loss. Finally, chronic immune activation in HIV infections induces multiple defects in the immune system and has recently been shown to accelerate HIV Env mediated CD4 apoptosis. Consequently, those factors that affect CCR5 expression and/or immune activation in turn indirectly regulate HIV mediated apoptosis making this phenomenon both complex and multifactorial. This review explores the complex role of various host and viral factors in determining HIV mediated bystander apoptosis.

Cytopenias among ART-naive patients with advanced HIV disease on enrolment to care and treatment services at a tertiary hospital in Tanzania: A cross-sectional study

BACKGROUND

HIV/AIDS causes high morbidity and mortality through both immunosuppression and complications not directly related to immunosuppression. Haematological abnormalities, including various cytopenias, occur commonly in HIV through immune and non-immune pathways. Though these complications could potentially cause serious clinical implications, published literature on the magnitude of this problem and its associated factors in Tanzania is scarce. This study aimed at determining the prevalence and risk factors of HIV-associated cytopenias among ART-naive patients enrolling for care and treatment services at Bugando Care and Treatment Centre (CTC) in Mwanza, Tanzania.

METHODS

This was a cross-sectional clinic-based study done between March 2015 and February 2016, involving all antiretroviral therapy (ART)-naive adult HIV-positive patients enrolling for care and treatment services at Bugando CTC. Patients younger than 18 years and those with missing data were excluded. Data were analysed using Stata version 11 to determine the prevalence and risk factors of cytopenias.

RESULTS

A total of 1205 ART-naive patients were included. Median age was 41 years (interquartile range [IQR] 32 to 48). Most participants were female (n = 789; 65.6%), with a female-to-male ratio of 2:1. The median baseline CD4 count was 200 cells/µL (IQR 113 to 439). About half (49%) of the study participants had baseline CD4 counts less than 200 cells/µL. Anaemia, leucopenia, and thrombocytopenia were found in 704 (58.4%), 285 (23.6%), and 174 (14.4%) participants, respectively, and these were strongly associated with advanced HIV infection.

CONCLUSIONS

The magnitude of cytopenias is high among ART-naive HIV-positive adults, and cytopenias are more marked with advanced HIV infection. Early diagnosis of HIV and timely initiation of ART could potentially reduce the number of people living with advanced HIV disease and its associated complications, including the cytopenias investigated in this study. Patients with cytopenias should undergo thorough screening for tuberculosis, which is an important and treatable correlate of cytopenia, in addition to close follow-up for any potential negative outcomes.

HIV Maintains an Evolving and Dispersed Population in Multiple Tissues during Suppressive Combined Antiretroviral Therapy in Individuals with Cancer

While combined antiretroviral therapy (cART) can result in undetectable plasma viral loads, it does not eradicate HIV infection. Furthermore, HIV-infected individuals while on cART remain at an increased risk of developing serious comorbidities, such as cancer, neurological disease, and atherosclerosis, suggesting that during cART, tissue-based HIV may contribute to such pathologies. We obtained DNA and RNA env, nef, and pol sequences using single-genome sequencing from postmortem tissues of three HIV(+) cART-treated (cART(+)) individuals with undetectable viral load and metastatic cancer at death and performed time-scaled Bayesian evolutionary analyses. We used a sensitive in situ hybridization technique to visualize HIV gag-pol mRNA transcripts in cerebellum and lymph node tissues from one patient. Tissue-associated virus evolved at similar rates in cART(+) and cART-naive (cART(-)) patients. Phylogenetic trees were characterized by two distinct features: (i) branching patterns consistent with constant viral evolution and dispersal among tissues and (ii) very recently derived clades containing both DNA and RNA sequences from multiple tissues. Rapid expansion of virus near death corresponded to wide-spread metastasis. HIV RNA(+) cells clustered in cerebellum tissue but were dispersed in lymph node tissue, mirroring the evolutionary patterns observed for that patient. Activated, infiltrating macrophages were associated with HIV RNA. Our data provide evidence that tissues serve as a sanctuary for wild-type HIV during cART and suggest the importance of macrophages as an alternative reservoir and mechanism of virus spread.

IMPORTANCE

Combined antiretroviral therapy (cART) reduces plasma HIV to undetectable levels; however, removal of cART results in plasma HIV rebound, thus highlighting its inability to entirely rid the body of infection. Additionally, HIV-infected individuals on cART remain at high risk of serious diseases, which suggests a contribution from residual HIV. In this study, we isolated and sequenced HIV from postmortem tissues from three HIV(+) cART(+) individuals who died with metastatic cancer and had no detectable plasma viral load. Using high-resolution evolutionary analyses, we found that tissue-based HIV continues to replicate, evolve, and migrate among tissues during cART. Furthermore, cancer onset and metastasis coincided with increased HIV expansion, suggesting a linked mechanism. HIV-expressing cells were associated with tissue macrophages, a target of HIV infection. Our results suggest the importance of tissues, and macrophages in particular, as a target for novel anti-HIV therapies.

IL-1β and IL-18 inhibition of HIV-1 replication in Jurkat cells and PBMCs

HIV-1 infection-induced apoptosis is able to ensure viral replication. The death of some CD4+ T cells residing in lymphoid tissues can be induced by HIV-1 infection through caspase-1 driven pyroptosis with release of cytokine of IL-1β and IL-18. It is not well known whether IL-1β and IL-18 affect HIV-1 replication in lymphocytic cells. Using susceptible lymphocytic cell line, Jurkat cells, and primary peripheral blood mononuclear cells (PBMCs), we studied the effects of IL-1β and IL-18 on HIV-1 replication. We found that treatment with exogenous IL-1β protein (rIL-1β) and IL-18 protein (rIL-18), or expression of IL-1β and IL-18 significantly reduced HIV-1 replication. HIV-1 infection enhanced caspase-3 expression and its activation, and had no effects on caspase-1 activity. Treatment with rIL-1β and rIL-18 dramatically lowered caspase-3 activity. IL-1β and IL-18 also played roles in diminishing reactivation of viral replication from latency in J1.1 cells. These results indicate that IL-1β and IL-18 are able to inhibit HIV-1 replication, and their effects may be due to signaling through apoptosis involved in inactivation of caspase-3 activity.

CCR5 interaction with HIV-1 Env contributes to Env-induced depletion of CD4 T cells in vitro and in vivo

BACKGROUND

CD4 T cell depletion during HIV-1 infection is associated with AIDS disease progression, and the HIV-1 Env protein plays an important role in the process. Together with CXCR4, CCR5 is one of the two co-receptors that interact with Env during virus entry, but the role of CCR5 in Env-induced pathogenesis is not clearly defined. We have investigated CD4 T cell depletion mechanisms caused by the Env of a highly pathogenic CXCR4/CCR5 dual-tropic HIV-1 isolate R3A.

RESULTS

We report here that R3A infection induced depletion of both infected and uninfected "bystander" CD4 T cells, and treatment with CCR5 antagonist TAK-779 inhibited R3A-induced bystander CD4 T cell depletion without affecting virus replication. To further define the role of Env-CCR5 interaction, we utilized an Env-mutant of R3A, termed R3A-5/6AA, which has lost CCR5 binding capability. Importantly, R3A-5/6AA replicated to the same level as wild type R3A by using CXCR4 for viral infection. We found the loss of CCR5 interaction resulted in a significant reduction of bystander CD4 T cells death during R3A-5/6AA infection, whereas stimulation of CCR5 with MIP1-β increased bystander pathogenesis induced by R3A-5/6AA. We confirmed our findings using a humanized mouse model, where we observed similarly reduced pathogenicity of the mutant R3A-5/6AA in various lymphoid organs in vivo.

CONCLUSION

We provide the first evidence that shows CCR5 interaction with a dual-tropic HIV-1 Env played a significant role in Env-induced depletion of CD4 T cells.

HIV-1 Env Glycoprotein Phenotype along with Immune Activation Determines CD4 T Cell Loss in HIV Patients

The mechanism behind the selective depletion of CD4(+) cells in HIV infections remains undetermined. Although HIV selectively infects CD4(+) cells, the relatively few infected cells in vivo cannot account for the extent of CD4(+) T cell depletion, suggesting indirect or bystander mechanisms. The role of virus replication, Env glycoprotein phenotype, and immune activation (IA) in this bystander phenomenon remains controversial. Using samples derived from HIV-infected patients, we demonstrate that, although IA in both CD4(+) and CD8(+) subsets correlates with CD4 decline, apoptosis in CD4(+) and not CD8(+) cells is associated with disease progression. Because HIV-1 Env glycoprotein has been implicated in bystander apoptosis, we cloned full-length Envs from plasma of viremic patients and tested their apoptosis-inducing potential (AIP). Interestingly, AIP of HIV-1 Env glycoproteins were found to correlate inversely with CD4:CD8 ratios, suggesting a role of Env phenotype in disease progression. In vitro mitogenic stimulation of PBMCs resulted in upregulation of IA markers but failed to alter the CD4:CD8 ratio. However, coculture of normal PBMCs with Env-expressing cells resulted in selective CD4 loss that was significantly enhanced by IA. Our study demonstrates that AIP of HIV-1 Env and IA collectively determine CD4 loss in HIV infection.

Increased cardiovascular disease risk in the HIV-positive population on ART: potential role of HIV-Nef and Tat

With effective antiretroviral therapy (ART), many HIV-infected people die of diseases other than acquired immune deficiency syndrome (AIDS). In particular, coronary artery disease has emerged as one of most critical complications of HIV infection and a major cause of morbidity and mortality. Although reportedly antiretroviral combination therapy itself may accelerate atherosclerosis by enhancing dyslipidemia, most recent epidemiological studies support the notion that HIV infection itself contributes to cardiovascular disease. However, it is still a mystery how the virus can contribute to cardiovascular disease development even while suppressed by ARTs. This review discusses the current understanding of interactions between HIV infection and cardiovascular diseases in both clinical and experimental studies with special focus on those viral proteins that are still produced by HIV. This will help infectious disease/vascular biology experts to gain insights into the pathophysiological mechanisms of HIV-associated cardiovascular disease and new trends to treat and prevent cardiovascular disease in the HIV-infected population.

Syncytial apoptosis signaling network induced by the HIV-1 envelope glycoprotein complex: an overview

Infection by human immunodeficiency virus-1 (HIV-1) is associated with a progressive decrease in CD4 T-cell numbers and the consequent collapse of host immune defenses. The major pathogenic mechanism of AIDS is the massive apoptotic destruction of the immunocompetent cells, including uninfected cells. The latter process, also known as by-stander killing, operates by various mechanisms one of which involves the formation of syncytia which undergo cell death by following a complex pathway. We present here a detailed and curated map of the syncytial apoptosis signaling network, aimed at simplifying the whole mechanism that we have characterized at the molecular level in the last 15 years. The map was created using Systems Biology Graphical Notation language with the help of CellDesigner software and encompasses 36 components (proteins/genes) and 54 interactions. The simplification of this complex network paves the way for the development of novel therapeutic strategies to eradicate HIV-1 infection. Agents that induce the selective death of HIV-1-elicited syncytia might lead to the elimination of viral reservoirs and hence constitute an important complement to current antiretroviral therapies.

Organelle-specific initiation of cell death

In a majority of pathophysiological settings, cell death is not accidental - it is controlled by a complex molecular apparatus. Such a system operates like a computer: it receives several inputs that inform on the current state of the cell and the extracellular microenvironment, integrates them and generates an output. Thus, depending on a network of signals generated at specific subcellular sites, cells can respond to stress by attemptinwg to recover homeostasis or by activating molecular cascades that lead to cell death by apoptosis or necrosis. Here, we discuss the mechanisms whereby cellular compartments - including the nucleus, mitochondria, plasma membrane, endoplasmic reticulum, Golgi apparatus, lysosomes, cytoskeleton and cytosol - sense homeostatic perturbations and translate them into a cell-death-initiating signal.

Mathematical Modeling of HIV Dynamics After Antiretroviral Therapy Initiation: A Review

This review shows the potential ground-breaking impact that mathematical tools may have in the analysis and the understanding of the HIV dynamics. In the first part, early diagnosis of immunological failure is inferred from the estimation of certain parameters of a mathematical model of the HIV infection dynamics. This method is supported by clinical research results from an original clinical trial: data just after 1 month following therapy initiation are used to carry out the model identification. The diagnosis is shown to be consistent with results from monitoring of the patients after 6 months. In the second part of this review, prospective research results are given for the design of individual anti-HIV treatments optimizing the recovery of the immune system and minimizing side effects. In this respect, two methods are discussed. The first one combines HIV population dynamics with pharmacokinetics and pharmacodynamics models to generate drug treatments using impulsive control systems. The second one is based on optimal control theory and uses a recently published differential equation to model the side effects produced by highly active antiretroviral therapy therapies. The main advantage of these revisited methods is that the drug treatment is computed directly in amounts of drugs, which is easier to interpret by physicians and patients.

CD4(+) T Cells Modified by the Endoribonuclease MazF Are Safe and Can Persist in SHIV-infected Rhesus Macaques

MazF, an endoribonuclease encoded by Escherichia coli, specifically cleaves the ACA (adenine–cytosine–adenine) sequence of single-stranded RNAs. Conditional expression of MazF under the control of the HIV-1 LTR promoter rendered CD4⁺ T cells resistant to HIV-1 replication without affecting cell growth. To investigate the safety, persistence and efficacy of MazF-modified CD4⁺ T cells in a nonhuman primate model in vivo, rhesus macaques were infected with a pathogenic simian/human immunodeficiency virus (SHIV) and transplanted with autologous MazF-modified CD4⁺ T cells. MazF-modified CD4⁺ T cells were clearly detected throughout the experimental period of more than 6 months. The CD4⁺ T cell count values increased in all four rhesus macaques. Moreover, the transplantation of the MazF-modified CD4⁺ T cells was not immunogenic, and did not elicit cellular or humoral immune responses. These data suggest that the autologous transplantation of MazF-modified CD4⁺ T cells in the presence of SHIV is effective, safe and not immunogenic, indicating that this is an attractive strategy for HIV-1 gene therapy.

Late-emerging strains of HIV induce T-cell homeostasis failure by promoting bystander cell death and immune exhaustion in naïve CD4 and all CD8 T-cells

The mechanisms involved in the decline of CD4 and CD8 T-cells that lead to HIV-induced immune dysregulation are not clearly understood. We hypothesize that late-emerging strains of HIV, such as CXCR4-tropic (X4) virions, induce T-cell homeostasis failure by promoting significantly more bystander cell death, and immune exhaustion in naïve CD4 and all CD8 T-cells, when compared to strain of HIV, such as CCR5-tropic (R5) virions, found early during the course of infection. In the reported study, inactivated X4 virions induced greater bystander cell death in sort-purified naïve CD4 T-cells compared to R5 virions, which was significant (p=0.013), and in memory CD8 T-cells, though the latter was not significant. A clearer understanding of the mechanisms involved in HIV-induced depletion of T-cell numbers and function could lead to therapies that prevent T-cell death and restore immune function. These therapies could improve current anti-retroviral and cure-related treatments by boosting the immune system's own ability to combat the virus.

Cocaine enhances HIV-1-induced CD4(+) T-cell apoptosis: implications in disease progression in cocaine-abusing HIV-1 patients

Substance abuse is a major barrier in eradication of the HIV epidemic because it serves as a powerful cofactor for viral transmission, disease progression, and AIDS-related mortality. Cocaine, one of the commonly abused drugs among HIV-1 patients, has been suggested to accelerate HIV disease progression. However, the underlying mechanism remains largely unknown. Therefore, we tested whether cocaine augments HIV-1-associated CD4(+) T-cell decline, a predictor of HIV disease progression. We examined apoptosis of resting CD4(+) T cells from HIV-1-negative and HIV-1-positive donors in our study, because decline of uninfected cells plays a major role in HIV-1 disease progression. Treatment of resting CD4(+) T cells with cocaine (up to 100 μmol/L concentrations) did not induce apoptosis, but 200 to 1000 μmol/L cocaine induced apoptosis in a dose-dependent manner. Notably, treatment of CD4(+) T cells isolated from healthy donors with both HIV-1 virions and cocaine significantly increased apoptosis compared with the apoptosis induced by cocaine or virions alone. Most important, our biochemical data suggest that cocaine induces CD4(+) T-cell apoptosis by increasing intracellular reactive oxygen species levels and inducing mitochondrial depolarization. Collectively, our results provide evidence of a synergy between cocaine and HIV-1 on CD4(+) T-cell apoptosis that may, in part, explain the accelerated disease observed in HIV-1-infected drug abusers.

Apoptosis in virus infection dynamics models

In this paper, on the basis of the simplified two-dimensional virus infection dynamics model, we propose two extended models that aim at incorporating the influence of activation-induced apoptosis which directly affects the population of uninfected cells. The theoretical analysis shows that increasing apoptosis plays a positive role in control of virus infection. However, after being included the third population of cytotoxic T lymphocytes immune response in HIV-infected patients, it shows that depending on intensity of the apoptosis of healthy cells, the apoptosis can either promote or comfort the long-term evolution of HIV infection. Further, the discrete-time delay of apoptosis is incorporated into the pervious model. Stability switching occurs as the time delay in apoptosis increases. Numerical simulations are performed to illustrate the theoretical results and display the different impacts of a delay in apoptosis.

Genetic signatures of HIV-1 envelope-mediated bystander apoptosis

The envelope (Env) glycoprotein of HIV is an important determinant of viral pathogenesis. Several lines of evidence support the role of HIV-1 Env in inducing bystander apoptosis that may be a contributing factor in CD4(+) T cell loss. However, most of the studies testing this phenomenon have been conducted with laboratory-adapted HIV-1 isolates. This raises the question of whether primary Envs derived from HIV-infected patients are capable of inducing bystander apoptosis and whether specific Env signatures are associated with this phenomenon. We developed a high throughput assay to determine the bystander apoptosis inducing activity of a panel of primary Envs. We tested 38 different Envs for bystander apoptosis, virion infectivity, neutralizing antibody sensitivity, and putative N-linked glycosylation sites along with a comprehensive sequence analysis to determine if specific sequence signatures within the viral Env are associated with bystander apoptosis. Our studies show that primary Envs vary considerably in their bystander apoptosis-inducing potential, a phenomenon that correlates inversely with putative N-linked glycosylation sites and positively with virion infectivity. By use of a novel phylogenetic analysis that avoids subtype bias coupled with structural considerations, we found specific residues like Arg-476 and Asn-425 that were associated with differences in bystander apoptosis induction. A specific role of these residues was also confirmed experimentally. These data demonstrate for the first time the potential of primary R5 Envs to mediate bystander apoptosis in CD4(+) T cells. Furthermore, we identify specific genetic signatures within the Env that may be associated with the bystander apoptosis-inducing phenotype.

Critical roles for Akt kinase in controlling HIV envelope-mediated depletion of CD4 T cells

BACKGROUND

The cell surface receptors CD4 and CCR5 bind CCR5-tropic HIV Envelope (Env) glycoprotein during virus attachment. These same receptors have signaling activities related to normal immune cell functions. We also know that Env binds to CCR5 present at high levels on CD4-negative γδ T cells where it signals through p38 MAP kinase to activate caspases and Fas-independent cell death. Here, we asked whether Env signaling through cellular receptors is responsible for death among uninfected CD4+/CCR5+ T cells and what are the effects of Env on CD4+/CCR5-negative cells that might impact HIV infection. The outcomes of Env binding are analyzed in terms of signal transduction and the effects on cell activation or cell death pathways.

RESULTS

Env binding to CD4 signals through Erk and Akt kinases. Activation of Erk/Akt suppresses p38 due to CCR5 binding, and allows cell survival. When CD4 signaling was blocked by soluble CD4 or protein kinase inhibitors, p38 activation and Fas-independent cell death were increased among uninfected CD4+ CCR5+ T cells. We also noted specific effects of CD4 signaling on CCR5-negative CD4 T cells in tonsil lymphocyte cultures. Exposure to CCR5-tropic HIV Env (BaL strain) increased expression of CXCR5, PD-1, Fas and FasL. Among CD4+/CCR5- T cells expressing high levels of CXCR5 and PD-1, there were substantial amounts of Fas-dependent cell death. Increased CXCR5 and PD-1 expression was blocked by soluble CD4 or specific inhibitors of the Akt kinase, showing a direct relationship between CD4 signaling, T cell activation and Fas-dependent cell death.

CONCLUSIONS

Specific inhibition of Akt activation increased Env-dependent cell death of CCR5+ CD4 T cells. The same inhibitor, antibodies blocking the CD4 binding site on gp120, or soluble CD4 also prevented the increase in expression of CXCR5 or PD-1, and reduced the levels of Fas-dependent cell death. The Akt kinase and related signaling events, are key to cell survival that is needed for productive infection, and may be targets for the development of antivirals. Specific inhibitors of Akt would decrease productive infection, by favoring cell death during virus attachment to CD4+ CCR5+ target cells, and reduce immune activation to prevent Fas-dependent death of uninfected CXCR5+ PD-1+ CD4 T cells including T follicular helper cells that share this phenotype.

A hunter virus that targets both infected cells and HIV free virions: implications for therapy

The design of ‘hunter’ viruses aimed at destroying human immunodeficiency virus (HIV) infected cells is an active area of research that has produced promising results in vitro. Hunters are designed to target exposed viral envelope proteins in the membranes of infected cells, but there is evidence that the hunter may also target envelope proteins of free HIV, inducing virus-virus fusion. In order to predict the effects of this fusion on therapy outcomes and determine whether fusion ability is advantageous for hunter virus design, we have constructed a model to account for the possibility of hunter-HIV fusion. The study was based on a target cell-limited model of HIV infection and it examined the hunter therapeutic effect on recovering the HIV main target cells, the activated CD4⁺ T lymphocytes. These cells assist in setting up an immune response to opportunistic infections. The study analyzed the hunter dual mechanisms to control infection and because of diverse estimates for viral production and clearance of HIV, simulations were examined at rates spanning an order of magnitude. Results indicate that without hunter-HIV fusion ability, hunters that kill HIV-infected cells lead to a substantial recovery of healthy cell population at both low and high HIV turnover rates. When hunter-HIV fusion is included, cell recovery was particularly enhanced at lower HIV turnover rates. This study shows that the fusion ability, in addition to hunter infection ability, could be a favorable attribute for improving the efficacy of hunter-viral therapy. These results provide support for the potential use of engineered viruses to control HIV and other viral infections.

HIV-1 induced bystander apoptosis

Apoptosis of uninfected bystander cells is a key element of HIV pathogenesis and believed to be the driving force behind the selective depletion of CD4+ T cells leading to immunodeficiency. While several viral proteins have been implicated in this process the complex interaction between Env glycoprotein expressed on the surface of infected cells and the receptor and co-receptor expressing bystander cells has been proposed as a major mechanism. HIV-1 utilizes CD4 as the primary receptor for entry into cells; however, it is the viral co-receptor usage that greatly influences CD4 decline and progression to AIDS. This phenomenon is relatively simple for X4 viruses, which arise later during the course of the disease, are considered to be highly fusogenic, and cause a rapid CD4+ T cell decline. However, in contrast, R5 viruses in general have a greater transmissibility, are encountered early during the disease and have a lesser pathogenic potential than the former. The above generalization gets complicated in numerous situations where R5 viruses persist throughout the disease and are capable of causing a rigorous CD4+ T cell decline. This review will discuss the multiple factors that are reported to influence HIV induced bystander apoptosis and pathogenesis including Env glycoprotein phenotype, virus tropism, disease stage, co-receptor expression on CD4+ T cells, immune activation and therapies targeting the viral envelope.

The intensity of immune activation is linked to the level of CCR5 expression in human immunodeficiency virus type 1-infected persons

Immune activation is a main driver of AIDS- and non-AIDS-linked morbidities in the course of HIV-1 infection. As CCR5, the main HIV-1 co-receptor, is not only a chemokine receptor but also a co-activation molecule expressed at the surface of T cells, it could be directly involved in this immune activation. To test this hypothesis, we measured by flow cytometry the mean number of CCR5 molecules at the surface of non-activated CD4(+) T cells (CCR5 density), which determines the intensity of CCR5 signalling, and the percentage of CD8(+) T cells over-expressing CD38 (CD38 expression), a major marker of immune activation, in the blood of 67 HIV-1-infected, non-treated individuals. CCR5 density was correlated with CD38 expression independently of viral load (P=0.016). CCR5 density remained unchanged after highly active anti-retroviral therapy (HAART) introduction or cessation, whereas CD38 expression decreased and increased, respectively. Moreover, pre-therapeutic CCR5 density was highly predictive (r=0.736, P<10(-4) ) of residual CD38 over-expression after 9 months of HAART. Hence, CCR5 might play an immunological role in HIV-1 infection as a driver of immune activation. This could explain why CCR5 antagonists may have an inhibitory effect on immune activation.

Excitability in the host-pathogen interactions of HIV infection and emergence of viral load blips

HIV viral blips are characterized by intermittent episodes of detectable low-level viraemia which return spontaneously to an undetectable level in patients with full suppression of viraemia (<50 copies/ml). The precise mechanisms responsible for viraemia blips and their clinical significance are not known. In this work, we analyze HIV blips using a mathematical model describing basic host-pathogen interactions, in particular regulatory processes involving CD4+, CD8+ T-cells and the virus. We show that under adequate conditions, this interaction system can be excitable and small perturbations of the system by external stimuli can generate robust viral load (VL) blips of regular or irregular frequency and peak amplitudes. Importantly, our analysis showed that direct perturbations of the viral load (by latent reservoirs or opportunistic diseases for example) more efficiently trigger VL blips on contrary to direct perturbations of the immune system, in particular the levels of uninfected CD4+ and cytotoxic CD8+ T-cells. This feature is shown to rely on specific stability properties in this interaction system. Our analysis moreover suggests that blips should be of low clinical significance since any other VL or immune system perturbations could trigger transient viraemia under adequate excitability conditions.

May viral (antigen) load be the real crucial tool leading to anergy in a "micro-evolutionary" model of host/virus interaction?

HYPOTHESIS

The hypothesis in the present work is that in host/virus/tumor (antigens) interactions, leading to anergy of the immune system, the Viral (antigen) load plays a crucial and central role, which all interactions turn around.

BACKGROUND

Notwithstanding apparent strong favorable evidences, the still prevailing concept of "active virus strategies to escape" may be misleading, since it might hide the cited pivotal role in a wide number of researches. This concept could be easily substituted by a microevolutionary model explaining many unresolved questions and allowing to emerge the role of antigen load conditioned reactions of the host's immune system as motivated choices. EVIDENCES: An anergy induced condition can be detected not only in HCV, but also in the course of persistent viral (e.g. HBV, HIV) and non viral parasitic infections (e.g. Leishmania and Helminths) which share the same host's reactions leading to anergy, independently on the infecting agents. The starting point of those reactions is always time elapsing from the primary infection after a short early (often undetected) period of high viral(antigen) load in the lack of clearance. This latter seems then the only conceivable link between such so different infections determining, as far as HBV and HCV are concerned, also Hepatocarcinoma under indirect facilitating conditions. In a wide majority of studies it seems clearly evident that viral load exerts a main role which contributes to determine host chosen reactions aimed at avoiding dangerous outcomes while controlling viral load. Strong clinical (i.e. both HIV infected patients treated with HAART, and helminths infected people with deworming drugs acting directly on viral and parasitic loads) and experimental studies (i.e. chimpanzees (the only animal model of HCV infection) infected with HBV inocula of different size) are here reported or cited to highlight the crucial role of antigen load also on HIV infection transmission, seroconversion, disease progression, treatment initiation and efficacy.

CONCLUDING SUGGESTIONS

The new era for antiviral drugs like protease and polymerase inhibitors that seem to be more efficacious and less toxic than Ribavirin, may open the possibility to verify, when administered during the early phase of HCV infection (eventually helped by an immune-stimulant cytokine as IL-2), whether a precocious significant reduction of viral load (threshold) may allow the host to sustain his strong reactions and clear the virus within the due time, confirming the hypothesis about the crucial role of this tool which may be extended to all the cited infections.

Macroautophagy Regulation during HIV-1 Infection of CD4+ T Cells and Macrophages

Autophagy is an intracellular mechanism whereby pathogens, particularly viruses, are destroyed in autolysosomes after their entry into targets cells. Therefore, to survive and replicate in host cells, viruses have developed multiple strategies to either counteract or exploit this process. The aim of this review is to outline the known relationships between HIV-1 and autophagy in CD4+ T lymphocytes and macrophages, two main HIV-1 cell targets. The differential regulation of autophagy in these two cell-types is highlighted and its potential consequences in terms of viral replication and physiopathology discussed.

The HR2 polymorphism N140I in the HIV-1 gp41 combined with the HR1 V38A mutation is associated with a less cytopathic phenotype

Background

Resistance to the fusion inhibitor enfuvirtide (ENF) is achieved by changes in the gp41 subunit of the HIV envelope glycoprotein (Env). Specific ENF-associated mutational pathways correlate with immunological recovery, even after virological failure, suggesting that the acquisition of ENF resistance alters gp41 pathogenicity. To test this hypothesis, we have characterized the expression, fusion capability, induction of CD4⁺ T cell loss and single CD4⁺ T cell death of 48 gp41 proteins derived from three patients displaying different amino acids (N, T or I) at position 140 that developed a V38A mutation after ENF-based treatment.

Results

In all cases, intra-patient comparison of Env isolated pre- or post-treatment showed comparable values of expression and fusogenic capacity. Furthermore, Env with either N or T at position 140 induced comparable losses of CD4⁺ T-cells, irrespective of the residue present at position 38. Conversely, Env acquiring the V38A mutation in a 140I background induced a significantly reduced loss of CD4⁺ T cells and lower single-cell death than did their baseline controls. No altered ability to induce single-cell death was observed in the other clones.

Conclusions

Overall, primary gp41 proteins with both V38A and N140I changes showed a reduced ability to induce single cell death and deplete CD4⁺ T cells, despite maintaining fusion activity. The specificity of this phenotype highlights the relevance of the genetic context to the cytopathic capacity of Env and the role of ENF-resistance mutations in modulating viral pathogenicity in vivo, further supporting the hypothesis that gp41 is a critical mediator of HIV pathogenesis.

HIV ENV glycoprotein-mediated bystander apoptosis depends on expression of the CCR5 co-receptor at the cell surface and ENV fusogenic activity

HIV-1 infections lead to a progressive depletion of CD4 cells culminating in AIDS. The coreceptor usage by HIV varies from CCR5 (R5) tropic early in infection to CXCR4 (X4) tropic in later infections. Although the coreceptor switch from R5 to X4 tropic HIV is well associated with progression to AIDS, the role of CCR5 in disease progression especially in patients infected exclusively with R5 isolates throughout the disease remains enigmatic. To better understand the role of CCR5 and R5 tropic HIV envelope in AIDS pathogenesis, we asked whether the levels of CCR5 and/or HIV Env-mediated fusion determine apoptosis of bystander cells. We generated CD4(+) T cell lines expressing varying levels of CCR5 on the cell surface to show that CCR5 expression levels correlate with bystander apoptosis induction. The mechanism of apoptosis involved caspase-3 activation and mitochondrial depolarization and was dependent on gp41 fusion activity as confirmed by fusion-restricted gp41 point mutants and use of the fusion inhibitor T20. Interestingly, lower levels of CCR5 were able to support virus replication in the absence of bystander apoptosis. Our findings suggest that R5 HIV-1-mediated bystander apoptosis is dependent on both CCR5 expression levels as well as fusogenic activity of the Env glycoprotein.

CD4+ T cell depletion in human immunodeficiency virus (HIV) infection: role of apoptosis

Human immunodeficiency virus (HIV) infection is principally a mucosal disease and the gastrointestinal (GI) tract is the major site of HIV replication. Loss of CD4+ T cells and systemic immune hyperactivation are the hallmarks of HIV infection. The end of acute infection is associated with the emergence of specific CD4+ and CD8+ T cell responses and the establishment of a chronic phase of infection. Abnormal levels of immune activation and inflammation persist despite a low steady state level of viremia. Although the causes of persistent immune hyperactivation remain incompletely characterized, physiological alterations of gastrointestinal tract probably play a major role. Failure to restore Th17 cells in gut-associated lymphoid tissues (GALT) might impair the recovery of the gut mucosal barrier. This review discusses recent advances on understanding the contribution of CD4+ T cell depletion to HIV pathogenesis.

Single amino acid change in gp41 region of HIV-1 alters bystander apoptosis and CD4 decline in humanized mice

Background

The mechanism by which HIV infection leads to a selective depletion of CD4 cells leading to immunodeficiency remains highly debated. Whether the loss of CD4 cells is a direct consequence of virus infection or bystander apoptosis of uninfected cells is also uncertain.

Results

We have addressed this issue in the humanized mouse model of HIV infection using a HIV variant with a point mutation in the gp41 region of the Env glycoprotein that alters its fusogenic activity. We demonstrate here that a single amino acid change (V38E) altering the cell-to-cell fusion activity of the Env minimizes CD4 loss in humanized mice without altering viral replication. This differential pathogenesis was associated with a lack of bystander apoptosis induction by V38E virus even in the presence of similar levels of infected cells. Interestingly, immune activation was observed with both WT and V38E infection suggesting that the two phenomena are likely not interdependent in the mouse model.

Conclusions

We conclude that Env fusion activity is one of the determinants of HIV pathogenesis and it may be possible to attenuate HIV by targeting gp41.

HIV tropism and decreased risk of breast cancer

Background

During the first two decades of the U.S. AIDS epidemic, and unlike some malignancies, breast cancer risk was significantly lower for women with human immunodeficiency virus (HIV) infection compared to the general population. This deficit in HIV-associated breast cancer could not be attributed to differences in survival, immune deficiency, childbearing or other breast cancer risk factors. HIV infects mononuclear immune cells by binding to the CD4 molecule and to CCR5 or CXCR4 chemokine coreceptors. Neoplastic breast cells commonly express CXCR4 but not CCR5. In vitro, binding HIV envelope protein to CXCR4 has been shown to induce apoptosis of neoplastic breast cells. Based on these observations, we hypothesized that breast cancer risk would be lower among women with CXCR4-tropic HIV infection.

Methods and Findings

We conducted a breast cancer nested case-control study among women who participated in the WIHS and HERS HIV cohort studies with longitudinally collected risk factor data and plasma. Cases were HIV-infected women (mean age 46 years) who had stored plasma collected within 24 months of breast cancer diagnosis and an HIV viral load ≥500 copies/mL. Three HIV-infected control women, without breast cancer, were matched to each case based on age and plasma collection date. CXCR4-tropism was determined by a phenotypic tropism assay. Odds ratios (OR) and 95% confidence intervals (CI) for breast cancer were estimated by exact conditional logistic regression. Two (9%) of 23 breast cancer cases had CXCR4-tropic HIV, compared to 19 (28%) of 69 matched controls. Breast cancer risk was significantly and independently reduced with CXCR4 tropism (adjusted odds ratio, 0.10, 95% CI 0.002–0.84) and with menopause (adjusted odds ratio, 0.08, 95% CI 0.001–0.83). Adjustment for CD4⁺ cell count, HIV viral load, and use of antiretroviral therapy did not attenuate the association between infection with CXCR4-tropic HIV and breast cancer.

Conclusions

Low breast cancer risk with HIV is specifically linked to CXCR4-using variants of HIV. These variants are thought to exclusively bind to and signal through a receptor that is commonly expressed on hyperplastic and neoplastic breast duct cells. Additional studies are needed to confirm these observations and to understand how CXCR4 might reduce breast cancer risk.

Mechanisms of HIV envelope-induced T lymphocyte apoptosis

Infection by the human immunodeficiency virus (HIV) is characterized by a progressive depletion of CD4 T lymphocytes, which leads to dysfunction of the immune system. Although a variety of mechanisms may contribute to the gradual T cell decline that occurs in HIV-infected patients, abnormal apoptosis of infected or bystander T lymphocytes is an important event leading to immunodeficiency. The HIV envelope glycoprotein plays a crucial role in HIV associated apoptosis through both death receptor-mediated and mitochondria-dependent pathways. This review summarizes current knowledge of Env-mediated T lymphocyte apoptosis.

CD4 downregulation by the human immunodeficiency virus type 1 Nef protein is dispensable for optimal output and functionality of viral particles in primary T cells

Nef is a multifunctional protein of the human immunodeficiency virus type 1 (HIV-1) required for high viral replication and disease progression. Several findings indicate that the capacity of Nef to downregulate surface CD4 is essential for the protein's pathogenic activity, although the mechanisms that link the two functions are yet unclear. It is believed that, by reducing surface CD4 levels, Nef counteracts the receptor's negative effects on virion infectivity and release. Here, we show that, in 293T cells co-expressing CD4 and HIV-1, the capacity of Nef to enhance the virion incorporation of Env products and release of viral particles was mediated by retention-degradation of neo-synthesized CD4 rather than by accelerated receptor endocytosis. Different results were observed in primary CD4(+) T lymphocytes in which Nef-mediated CD4 downregulation occurs primarily by accelerated internalization. In HIV-infected T cell cultures, Nef was crucial for the removal of surface CD4 at the beginning of the infection, while later on maximal CD4 downregulation was achieved in a Nef-independent manner. Moreover, by means of in vivo selected Nef mutants, we observed that CD4 downregulation is not essential for Nef ability to enhance Env incorporation into virions and increase viral infectivity or replication in CD4(+) T lymphocytes. Notably, Nef expression itself was dispensable for efficient release of HIV-1 particles by T cells. In conclusion, we propose that the CD4 downregulation activity of Nef plays a role before the late productive phases of HIV-1 replication.

Effectiveness of a 'hunter' virus in controlling human immunodeficiency virus type 1 infection

Engineered therapeutic viruses provide an alternative method for treating infectious diseases, and mathematical models can clarify the system's dynamics underlying this type of therapy. In particular, this study developed models to evaluate the potential to contain human immunodeficiency virus type 1 (HIV-1) infection using a genetically engineered 'hunter' virus that kills HIV-1-infected cells. First, we constructed a novel model for understanding the progression of HIV infection that predicted the loss of the immune system's CD4(+) T cells across time. Subsequently, it determined the effects of introducing hunter viruses in restoring cell population. The model implemented direct and indirect mechanisms by which HIV-1 may cause cell depletion and an immune response. Results suggest that the slow progression of HIV infection may result from a slowly decaying CTL immune response, leading to a limited but constant removal of uninfected CD4 resting cells through apoptosis - and from resting cell proliferation that reduces the rate of cell depletion over time. Importantly, results show that the hunter virus does restrain HIV infection and has the potential to allow major cell recovery to 'functional' levels. Further, the hunter virus persisted at a reduced HIV load and was effective either early or late in the infection. This study indicates that hunter viruses may halt the progression of the HIV infection by restoring and sustaining high CD4(+) T-cell levels.

Prolonged depletion of circulating CD4+ T lymphocytes and acute monocytosis after pantropic canine coronavirus infection in dogs

A hypervirulent strain (CB/05) of canine coronavirus was employed to infect oronasally 11-week-old pups. Peripheral blood monocytes (CD14⁺), T lymphocytes (CD4⁺ and CD8⁺) and B lymphocytes (CD21⁺) were studied by flow cytometry within 5 days post-infection (p.i.) and at later time points. Infection with CB/05 resulted in a profound depletion of T cells and a slight loss of B cells in the first week p.i. In particular, while the CD8⁺ and the B lymphocytes returned to baseline levels by day 7 p.i., the CD4⁺ T cells remained significantly low until day 30 p.i. and recovered completely only at day 60 p.i. Monocytosis was also observed after CB/05 infection with a peak at day 5 p.i. The prolonged depletion of peripheral CD4⁺ T cells did not alter the levels of serum IgG or IgM. The impact of CB/05 infection on the immune performance of infected pups is discussed.

Differential modulation of mitochondrial OXPHOS system during HIV-1 induced T-cell apoptosis: up regulation of Complex-IV subunit COX-II and its possible implications

Human Immunodeficiency Virus-1 (HIV-1) infection leads to CD4+ T cell depletion primarily by apoptosis employing both intrinsic and extrinsic pathways. Although extensive literature exists about the role of mitochondrial proteins in HIV induced T cell apoptosis, there is little understanding about the role of different components of mitochondrial oxidative phosphorylation (OXPHOS) system in apoptosis. The OXPHOS system comprises of five enzyme complexes (Complex I, II, III, IV, V), subunits of which have been implicated in various functions in addition to their primary role in energy generating process. Here using differential gene expression analysis, we report that Cytochrome Oxidase-II (COX-II), a subunit of Complex-IV is induced in HIV infected apoptotic T-cells. We also observe a temporal up regulation of this subunit across different T-cell lines and in human PBMCs. Further analysis indicates increase in expression of majority of Complex-IV subunits with concomitant increase in Complex-IV activity in HIV infected T cells. Silencing of COX-II expression leads to reduced apoptosis in infected T-cells, indicating its importance in apoptosis. Furthermore, our results also show that the activities of enzyme complexes I, II and III are decreased while those of Complex IV and V are increased at the time of acute infection and apoptosis. This differential regulation in activities of OXPHOS system complexes indicate a complex modulation of host cell energy generating system during HIV infection that ultimately leads to T cell apoptosis.