Role of HIV Gp41 mediated fusion/hemifusion in bystander apoptosis

Mechanisms of HIV-mediated CD4+ T cell loss leading to immunodeficiency are amongst the most extensively studied yet unanswered questions in HIV biology. The level of CD4+ T cell depletion in HIV infected patients far exceeds the number of infected T cells, suggesting an indirect mechanism of HIV pathogenesis termed bystander cell death. Evidence is accumulating that the HIV envelope glycoprotein (Env) is a major determinant of HIV pathogenesis and plays a critical role in bystander cell death. The complex structure and function of HIV Env makes the determination of the mechanism of Envmediated apoptosis more complex than previously thought. This review will examine the complex relationship between HIV Env phenotype, coreceptor expression and immune activation in determining HIV pathogenesis. We review data here corresponding to the role of HIV Env hemifusion activity in HIV pathogenesis and how it interplays with other AIDS associated factors such as chemokine receptor expression and immune activation. Received 21 March 2008; received after revision 29 April 2008; accepted 30 April 2008     

The implications of viral reservoirs on the elite control of HIV-1 infection

The mechanisms by which a small percentage of HIV-1 infected individuals known as elite suppressors or controllers are able to control viral replication are not fully understood. Early cases of viremic control were attributed to infection with defective virus, but subsequent work has demonstrated that infection with a defective virus is not the exclusive cause of control. Replication-competent virus has been isolated from patients who control viral replication, and studies have demonstrated that evolution occurs in plasma virus but not in virus isolates from the latent reservoir. Additionally, transmission pair studies have demonstrated that patients infected with similar viruses can have dramatically different outcomes of infection. An increased understanding of the viral factors associated with control is important to understand the interplay between viral replication and host control, and has implications for the design of an effective therapeutic vaccine that can lead to a functional cure of HIV-1 infection.     

Novel AIDS therapies based on gene editing

HIV/AIDS remains a major public health issue. In 2014, it was estimated that 36.9 million people are living with HIV worldwide, including 2.6 million children. Since the advent of combination antiretroviral therapy (cART), in the 1990s, treatment has been so successful that in many parts of the world, HIV has become a chronic condition in which progression to AIDS has become increasingly rare. However, while people with HIV can expect to live a normal life span with cART, lifelong medication is required and cardiovascular, renal, liver, and neurologic diseases are still possible, which continues to prompt research for a cure for HIV. Infected reservoir cells, such as CD4+?T cells and myeloid cells, allow persistence of HIV as an integrated DNA provirus and serve as a potential source for the re-emergence of virus. Attempts to eradicate HIV from these cells have focused mainly on the so-called “shock and kill” approach, where cellular reactivation is induced so as to trigger the purging of virus-producing cells by cytolysis or immune attack. This approach has several limitations and its usefulness in clinical applications remains to be assessed. Recent advances in gene-editing technology have allowed the use of this approach for inactivating integrated proviral DNA in the genome of latently infected cells or knocking out HIV receptors. Here, we review this strategy and its potential to eliminate the latent HIV reservoir resulting in a sterile cure of AIDS.     

Signalling in viral entry

Viral infections are serious battles between pathogens and hosts. They can result in cell death, elimination of the virus or latent infection keeping both cells and pathogens alive. The outcome of an infection is often determined by cell signalling. Viruses deliver genomes and proteins with signalling potential into target cells and thereby alter the metabolism of the host. Virus interactions with cell surface receptors can elicit two types of signals, conformational changes of viral particles, and intracellular signals triggering specific cellular reactions. Responses by cells include stimulation of innate and adaptive immunity, growth, proliferation, survival and apoptosis. In addition, virus-activated cell signalling boosts viral entry and gene delivery, as recently shown for adenoviruses and adeno-associated viruses. This review illustrates that multiple activation of host cells during viral entry profoundly impacts the elaborate relationship between hosts and viral pathogens. Received 13 September 2001; received after revision 23 October 2001; accepted 16 November 2001     

Control of HIV infection by IFN-α: implications for latency and a cure

Viral infections, including HIV, trigger the production of type I interferons (IFNs), which in turn, activate a signalling cascade that ultimately culminates with the expression of anti-viral proteins. Mounting evidence suggests that type I IFNs, in particular IFN-α, play a pivotal role in limiting acute HIV infection. Highly active anti-retroviral treatment reduces viral load and increases life expectancy in HIV positive patients; however, it fails to fully eliminate latent HIV reservoirs. To revisit HIV as a curable disease, this article reviews a body of literature that highlights type I IFNs as mediators in the control of HIV infection, with particular focus on the anti-HIV restriction factors induced and/or activated by IFN-α. In addition, we discuss the relevance of type I IFN treatment in the context of HIV latency reversal, novel therapeutic intervention strategies and the potential for full HIV clearance.     

HIV/AIDS: modified stem cells in the spotlight

Since HIV/AIDS was first recognized in 1981, an urgent need has existed for the development of novel therapeutic strategies to treat the disease. Due to the current antiretroviral therapy not being curative, human stem cell-based therapeutic intervention has emerged as an approach for its treatment. Genetically modified hematopoietic stem cells (HSCs) possess the potential to self-renew, reconstitute the immune system with HIV-resistant cells, and thus control, or even eliminate, viral replication. However, HSCs may be difficult to isolate in sufficient number from HIV-infected individuals for transplantation and/or re-infusion of autologous HSCs preparations would also include some contaminating HIV-infected cells. Furthermore, since genetic modification of HSCs is not completely efficient, the risk of providing unprotected immune cells to become new targets for HIV to infect could contribute to continued immune system failure. Therefore, induced pluripotent stem cells (iPSCs) should be considered a new potential source of cells to be engineered for HIV resistance and subsequently differentiated into clonal anti-HIV HSCs or hematopoietic progeny for transplant. In this article, we provide an overview of the current possible cellular therapies for treating HIV/AIDS.     

Integrase, LEDGF/p75 and HIV replication

HIV integrates a DNA copy of its genome into a host cell chromosome in each replication cycle. The essential DNA cleaving and joining chemistry of integration is known, but there is less understanding of the process as it occurs in a cell, where two complex and dynamic macromolecular entities are joined: the viral pre-integration complex and chromatin. Among implicated cellular factors, much recent attention has coalesced around LEDGF/p75, a nuclear protein that may act as a chromatin docking factor or receptor for lentiviral pre-integration complexes. LEDGF/p75 tethers HIV integrase to chromatin, protects it from degradation, and strongly influences the genome-wide pattern of HIV integration. Depleting the protein from cells and/or over-expressing its integrase-binding domain blocks viral replication. Current goals are to establish the underlying mechanisms and to determine whether this knowledge can be exploited for antiviral therapy or for targeting lentiviral vector integration in human gene therapy. Received 25 November 2007; received after revision 7 January 2008; accepted 10 January 2008     

Functional mechanisms of the cellular prion protein (PrPC) associated anti-HIV-1 properties

The cellular prion protein PrP(C)/CD230 is a GPI-anchor protein highly expressed in cells from the nervous and immune systems and well conserved among vertebrates. In the last decade, several studies suggested that PrP(C) displays antiviral properties by restricting the replication of different viruses, and in particular retroviruses such as murine leukemia virus (MuLV) and the human immunodeficiency virus type 1 (HIV-1). In this context, we previously showed that PrP(C) displays important similarities with the HIV-1 nucleocapsid protein and found that PrP(C) expression in a human cell line strongly reduced HIV-1 expression and virus production. Using different PrP(C) mutants, we report here that the anti-HIV-1 properties are mostly associated with the amino-terminal 24-KRPKP-28 basic domain. In agreement with its reported RNA chaperone activity, we found that PrP(C) binds to the viral genomic RNA of HIV-1 and negatively affects its translation. Using a combination of biochemical and cell imaging strategies, we found that PrP(C) colocalizes with the virus assembly machinery at the plasma membrane and at the virological synapse in infected T cells. Depletion of PrP(C) in infected T cells and microglial cells favors HIV-1 replication, confirming its negative impact on the HIV-1 life cycle.     

Presence of autocomplementary RNA with viral specificity in cells infected with herpes virus]

RNA from cells infected with Herpes simplex virus contain a higher percentage of double-stranded RNA than non-infected cells. This percentage increases three-fold upon self-annealing. The complementary RNA sequences were shown to be virus-specific by the following criteria: (1) high melting temperature than double-stranded RNA from non infected cells; (2) higher density in caesium sulphate; (3) specific hybridization with viral DNA.     

Effect of human interferon on viral production in a cell line chronically infected by a type D retrovirus (Mason-Pfizer virus)]

Human interferon specifically inhibits the viral multiplication in a human cell line infected by a type D retrovirus, the Mason-Pfizer virus (MPV). This inhibition is less important than for type C viruses.     

Early SIV and HIV infection promotes the LILRB2/MHC-I inhibitory axis in cDCs

Classical dendritic cells (cDCs) play a pivotal role in the early events that tip the immune response toward persistence or viral control. In vitro studies indicate that HIV infection induces the dysregulation of cDCs through binding of the LILRB2 inhibitory receptor to its MHC-I ligands and the strength of this interaction was proposed to drive disease progression. However, the dynamics of the LILRB2/MHC-I inhibitory axis in cDCs during early immune responses against HIV are yet unknown. Here, we show that early HIV-1 infection induces a strong and simultaneous increase of LILRB2 and MHC-I expression on the surface of blood cDCs. We further characterized the early dynamics of LILRB2 and MHC-I expression by showing that SIVmac251 infection of macaques promotes coordinated up-regulation of LILRB2 and MHC-I on cDCs and monocytes/macrophages, from blood and lymph nodes. Orientation towards the LILRB2/MHC-I inhibitory axis starts from the first days of infection and is transiently induced in the entire cDC population in acute phase. Analysis of the factors involved indicates that HIV-1 replication, TLR7/8 triggering, and treatment by IL-10 or type I IFNs increase LILRB2 expression. Finally, enhancement of the LILRB2/MHC-I inhibitory axis is specific to HIV-1 and SIVmac251 infections, as expression of LILRB2 on cDCs decreased in naturally controlled chikungunya virus infection of macaques. Altogether, our data reveal a unique up-regulation of LILRB2 and its MHC-I ligands on cDCs in the early phase of SIV/HIV infection, which may account for immune dysregulation at a critical stage of the anti-viral response.     

Susceptibility of chick neural retina to viral multiplication in vitro during embryonic development

Decrease in the susceptibility of embryonic chick neural retina cultures to the multiplication of various viruses was observed with increasing age of the embryo. In contrast the retinal cells supported the multiplication of Sindbis virus irrespective of the age when they were infected with the viral RNA. These results suggest that the restricted multiplication of the viruses observed is due to the modulated inability of the cell to process the adsorbed viruses for subsequent replication.     

Susceptibility of chick neural retina to viral multiplication in vitro during embryonic development

Summary Decrease in the susceptibility of embryonic chick neural retina cultures to the multiplication of various viruses was observed with increasing age of the embryo. In contrast the retinal cells supported the multiplication of Sindbis virus irrespective of the age when they were infected with the viral RNA. These results suggest that the restricted multiplication of the viruses observed is due to the modulated inability of the cell to process the adsorbed viruses for subsequent replication.     

Compared expression of murine plasmacytoma associated virus in tumor cells and in mouse embryo cells]

A DNA complementary to the viral genome of C-type particles produced by a Mouse myeloma derived cell line (MF2 cell line) was synthesized. This cDNA was used as a probe to study the viral genome expression among the total RNA and the poly (A)-rich RNA extracted from the MF2 and Balb/c embryonic cells. As evidenced by molecular hybridization experiments, the presence of at least one endogenous Balb/c virus in the MF2 virus stocks is suggested. In the productive cells, the viral RNA sequences are expressed in the poly (A)-rich RNA fraction.     

Change in the envelope of a murine retrovirus produced in the presence of toyocamycin]

Toyocamycin (TMC), an adenosine analog, impairs qualitatively and quantitatively virus production in a cellular system chronically infected by Friend Virus. Viral particles released by cell cultures treated with 0.2 microgram/ml of the drug have lost most of their glycoprotein (gp 70) content. This phenomenon is likely to modify the viral envelope and could explain the loss of infectivity of the virus.     

Adenylate cyclase activation and its effects on intracellular cAMP in infected KB cells during trypsin-induced infectious Senda? virus production (author's transl)]

KB cells infected by Senda? virus can produce infectious virus if they are trypsinated twice over 24 h. Adenylate cyclase activity in infected KB cells is higher and more strongly activated by trypsin than that of control cells, but intracellular concentration of cAMP is the same, except during a short time after trypsinations, especially after the second trypsination which causes infectious virus production. During this short time, intracellular cAMP is slightly higher in infected cells. This miseffect of adenylate cyclase activation on intracellular cAMP concentrations might be related to an increased cell permeability caused by trypsin.     

RNA干扰CD133基因对结肠癌干细胞生物学行为的影响

目的探讨CD133基因表达、活化被阻断后对结肠癌干细胞生物学行为的影响。方法从EpcAMhighCD44＋结肠癌干细胞中流式分选获得CD133＋细胞，感染LV-CD133shRNA载体慢病毒后观察CD133＋结肠癌干细胞在生长方式、成球能力、克隆形成率、成瘤能力以及ABCC2mRNA的变化；Westernblot分析CD133-细胞中CD133蛋白表达情况。结果EpcAMhighCD44＋结肠癌干细胞中CD133＋细胞比例为89．2％。实验组经过LV-CD133shRNA载体病毒感染后，在干细胞养液中细胞改悬浮生长的方式为贴壁生长，不能形成细胞球。MTT法测定发现细胞增殖减慢，克隆形成率明显下降。将感染细胞移植在Balb／C裸鼠体内，在观察期间，感染LV—CD133shRNA载体病毒的CD133＋细胞无肿瘤形成。ABCG2mRNA表达水平明显降低（P〈0．01）。从EpcAMhighCD44＋结肠癌干细胞中流式分选获得CD133-细胞，其中也有CD133蛋白的表达。结论CD133维持结肠癌干细胞生物学特性。     

Activation de l'adénylate cyclase et ses répercussions sur le taux intracellulaire d'AMP cyclique dans les cellules KB infectées produisant du virus Sendaï, infectieux sous l'influence de la trypsine

Summary KB cells infected by Sendaï virus can produce infectious virus if they are trypsinated twice over 24 h. Adenylate cyclase activity in infected KB cells is higher and more strongly activated by trypsin than that of control cells, but intracellular concentration of cAMP is the same, except during a short time after trypsinations, especially after the second trypsination which causes infectious virus production. During this short time, intracellular cAMP is slightly higher in infected cells. This miseffect of adenylate cyclase activation on intracellular cAMP concentrations might be related to an increased cell permeability caused by trypsin.