AIDS/HIV
Abstract
Autophagy is a process by which cells recycle cytoplasm and defective organelles during stress situations such as nutrient starvation. It can also be used by host cells as an immune defense mechanism to eliminate infectious pathogens. Here we describe the use of autophagy as a survival mechanism and virulence-associated trait by the human fungal pathogen Cryptococcus neoformans. We report that a mutant form of C. neoformans lacking the Vps34 PI3K (vps34Δ), which is known to be involved in autophagy in ascomycete yeast, was defective in the formation of autophagy-related 8–labeled (Atg8-labeled) vesicles and showed a dramatic attenuation in virulence in mouse models of infection. In addition, autophagic vesicles were observed in WT but not vps34Δ cells after phagocytosis by a murine macrophage cell line, and Atg8 expression was exhibited in WT C. neoformans during human infection of brain. To dissect the contribution of defective autophagy in vps34Δ C. neoformans during pathogenesis, a strain of C. neoformans in which Atg8 expression was knocked down by RNA interference was constructed and these fungi also demonstrated markedly attenuated virulence in a mouse model of infection. These results demonstrated PI3K signaling and autophagy as a virulence-associated trait and survival mechanism during infection with a fungal pathogen. Moreover, the data show that molecular dissection of such pathogen stress-response pathways may identify new approaches for chemotherapeutic interventions.
Authors
Guowu Hu, Moshe Hacham, Scott R. Waterman, John Panepinto, Soowan Shin, Xiaoguang Liu, Jack Gibbons, Tibor Valyi-Nagy, Keisuke Obara, H. Ari Jaffe, Yoshinori Ohsumi, Peter R. Williamson
Abstract
HIV-1 envelope glycoproteins (Env), expressed at the cell surface, induce apoptosis of uninfected CD4+ T cells, contributing to the development of AIDS. Here we demonstrate that, independently of HIV replication, transfected or HIV-infected cells that express Env induced autophagy and accumulation of Beclin 1 in uninfected CD4+ T lymphocytes via CXCR4. The same phenomena occurred in a T cell line and in transfected HEK.293 cells that expressed both wild-type CXCR4 and a truncated form of CD4 that is unable to bind the lymphocyte-specific protein kinase Lck. Env-mediated autophagy is required to trigger CD4+ T cell apoptosis since blockade of autophagy at different steps, by either drugs (3-methyladenine and bafilomycin A1) or siRNAs specific for Beclin 1/Atg6 and Atg7 genes, totally inhibited the apoptotic process. Furthermore, CD4+ T cells still underwent Env-mediated cell death with autophagic features when apoptosis was inhibited. These results suggest that HIV-infected cells can induce autophagy in bystander CD4+ T lymphocytes through contact of Env with CXCR4, leading to apoptotic cell death, a mechanism most likely contributing to immunodeficiency.
Authors
Lucile Espert, Mélanie Denizot, Marina Grimaldi, Véronique Robert-Hebmann, Bernard Gay, Mihayl Varbanov, Patrice Codogno, Martine Biard-Piechaczyk
Abstract
The persistence of latently infected, resting CD4+ T cells is considered to be a major obstacle in preventing the eradication of HIV-1 even in patients who have received effective antiviral therapy for an average duration of 5 years. Although previous studies have suggested that the latent HIV reservoir in the resting CD4+ T cell compartment is virologically quiescent in the absence of activating stimuli, evidence has been mounting to suggest that low levels of ongoing viral replication persist and in turn, prolong the overall half-life of HIV in patients receiving antiviral therapy. Here, we demonstrate the persistence of replication-competent virus in CD4+ T cells in a cohort of patients who had received uninterrupted antiviral therapy for up to 9.1 years that rendered them consistently aviremic throughout that time. Surprisingly, substantially higher levels of HIV proviral DNA were found in activated CD4+ T cells when compared with resting CD4+ T cells in the majority of patients we studied. Phylogenetic analyses revealed evidence for cross infection between the resting and activated CD4+ T cell compartments, suggesting that ongoing reactivation of latently infected, resting CD4+ T cells and spread of virus by activated CD4+ T cells may occur in these patients. Such events may allow continual replenishment of the CD4+ T cell reservoir and resetting of the half-life of the latently infected, resting CD4+ T cells despite prolonged periods of aviremia.
Authors
Tae-Wook Chun, David C. Nickle, J. Shawn Justement, Danielle Large, Alice Semerjian, Marcel E. Curlin, M. Angeline O’Shea, Claire W. Hallahan, Marybeth Daucher, Douglas J. Ward, Susan Moir, James I. Mullins, Colin Kovacs, Anthony S. Fauci
Abstract
DC-specific ICAM3-grabbing non-integrin (DC-SIGN), which is expressed on DCs, can interact with a variety of pathogens such as HIV-1, hepatitis C, Ebola, cytomegalovirus, Dengue virus, Mycobacterium, Leishmania, and Candida albicans. We demonstrate that human milk can inhibit the DC-SIGN–mediated transfer of HIV-1 to CD4+ T lymphocytes as well as viral transfer by both immature and mature DCs. The inhibitory factor directly interacted with DC-SIGN and prevented the HIV-1 gp120 envelope protein from binding to the receptor. The human milk proteins lactoferrin, α-lactalbumin, lysozyme, β-casein, and secretory leukocyte protease inhibitor did not bind DC-SIGN or demonstrate inhibition of viral transfer. The inhibitory effect could be fully alleviated with an Ab recognizing the Lewis X (LeX) sugar epitope, commonly found in human milk. LeX in polymeric form or conjugated to protein could mimic the inhibitory activity, whereas free LeX sugar epitopes could not. We reveal that a LeX motif present in human milk can bind to DC-SIGN and thereby prevent the capture and subsequent transfer of HIV-1 to CD4+ T lymphocytes. The presence of such a DC-SIGN–binding molecule in human milk may both influence antigenic presentation and interfere with pathogen transfer in breastfed infants.
Authors
Marloes A. Naarding, Irene S. Ludwig, Fedde Groot, Ben Berkhout, Teunis B.H. Geijtenbeek, Georgios Pollakis, William A. Paxton
Abstract
HIV-1 directly activates human plasmacytoid DCs (pDCs) by upregulating the expression of costimulatory and MHC molecules and maturation markers, increasing T cell stimulatory activity, and inducing the production of type I interferons and TNF-α. A consequence of this activation is the bystander maturation of myeloid DCs and overall enhancement of antigen-presenting function. However, little is known about the mechanism(s) of pDC activation by HIV-1. Here we demonstrate by in vitro studies that IFN-α production by pDC in response to HIV-1 requires at least 2 interactions between the cell and virus. Initially, envelope-CD4 interactions mediate endocytosis of HIV-1, as demonstrated through the use of inhibitors of binding, fusion, endocytosis, and endosomal acidification. Subsequently, endosomally delivered viral nucleic acids, particularly RNA, stimulate pDCs through TLRs, as activation is reproduced with purified genomic RNA but not viral RNA packaging–deficient HIV-1 and blocked with different inhibitory TLR ligands. Finally, by using genetic complementation, we show that TLR7 is the likely primary target. Viral RNA rather than DNA in early retrotranscripts appears to be the active factor in HIV-1 that induces IFN-α secretion by pDCs. Since the decline in pDCs in chronic HIV-1 infection is associated with high viral loads and opportunistic infections, exploiting this natural adjuvant activity of HIV-1 RNA might be useful in the development of vaccines for the prevention of AIDS.
Authors
Anne-Sophie Beignon, Kelli McKenna, Mojca Skoberne, Olivier Manches, Ida DaSilva, Daniel G. Kavanagh, Marie Larsson, Robert J. Gorelick, Jeffrey D. Lifson, Nina Bhardwaj
Abstract
HIV infection leads to decreases in the number of CD4+ T lymphocytes and an increased risk for opportunistic infections and neoplasms. The administration of intermittent cycles of IL-2 to HIV-infected patients can lead to profound increases (often greater than 100%) in CD4 cell number and percentage. Using in vivo labeling with 2H-glucose and BrdU, we have been able to demonstrate that, although therapy with IL-2 leads to high levels of proliferation of CD4 as well as CD8 lymphocytes, it is a remarkable preferential increase in survival of CD4 cells (with half-lives that can exceed 3 years) that is critical to the sustained expansion of these cells. This increased survival was time-dependent: the median half-life, as determined by semiempirical modeling, of labeled CD4 cells in 6 patients increased from 1.7 weeks following an early IL-2 cycle to 28.7 weeks following a later cycle, while CD8 cells showed no change in the median half-life. Examination of lymphocyte subsets demonstrated that phenotypically naive (CD27+CD45RO–) as well as central memory (CD27+CD45RO+) CD4 cells were preferentially expanded, suggesting that IL-2 can help maintain cells important for host defense against new antigens as well as for long-term memory to opportunistic pathogens.
Authors
Joseph A. Kovacs, Richard A. Lempicki, Igor A. Sidorov, Joseph W. Adelsberger, Irini Sereti, William Sachau, Grace Kelly, Julia A. Metcalf, Richard T. Davey Jr., Judith Falloon, Michael A. Polis, Jorge Tavel, Randy Stevens, Laurie Lambert, Douglas A. Hosack, Marjorie Bosche, Haleem J. Issaq, Stephen D. Fox, Susan Leitman, Michael W. Baseler, Henry Masur, Michele Di Mascio, Dimiter S. Dimitrov, H. Clifford Lane
Abstract
The fusion peptide (FP) in the N terminus of the HIV envelope glycoprotein, gp41, functions together with other gp41 domains to fuse the virion with the host cell membrane. We now report that FP colocalizes with CD4 and TCR molecules, coprecipitates with the TCR, and inhibits antigen-specific T cell proliferation and proinflammatory cytokine secretion in vitro. These effects are specific: T cell activation by PMA/ionomycin or mitogenic antibodies is not affected by FPs, and FPs do not interfere with antigen-presenting cell function. In vivo, FPs inhibit the activation of arthritogenic T cells in the autoimmune disease model of adjuvant arthritis and reduce the disease-associated IFN-γ response. Hence, FPs might play 2 roles in HIV infection: mediating membrane fusion while downregulating T cell responses to itself that could block infection. Disassociated from HIV, however, the FP molecule provides a novel reagent for downregulating undesirable immune responses, exemplified here by adjuvant arthritis.
Authors
Francisco J. Quintana, Doron Gerber, Sally C. Kent, Irun R. Cohen, Yechiel Shai
Abstract
Authors
Christopher Kornfeld, Mickaël J.-Y. Ploquin, Ivona Pandrea, Abdourahmane Faye, Richard Onanga, Cristian Apetrei, Virginie Poaty-Mavoungou, Pierre Rouquet, Jérôme Estaquier, Lorenzo Mortara, Jean-François Desoutter, Cécile Butor, Roger Le Grand, Pierre Roques, François Simon, Françoise Barré-Sinoussi, Ousmane M. Diop, Michaela C. Müller-Trutwin
Abstract
T cell activation levels in HIV infection are predictive of AIDS progression. We searched for the immunological correlates of protection against disease progression by studying the early stages of nonpathogenic SIV infection in African green monkeys (SIVagm). The African green monkeys (AGMs) displayed high peak viremias and a transient decline in levels of blood CD4+ and CD8+ T cells between days 5 and 17 after infection. A concomitant increase in levels of CD4+DR+, CD8+DR+, and CD8+CD28– cells was detected. After the third week, T cell activation returned to baseline levels, which suggested a protective downregulation of T cell activation. A very early (24 hours after infection) and strong induction of TGF-β1 and FoxP3 expression was detected and correlated with increases in levels of CD4+CD25+ and CD8+CD25+ T cells. This was followed by a significant increase in levels of IL-10, whereas IFN-γ gene upregulation was more transient, and levels of TNF-α and MIP-1α/β transcripts did not increase in either blood or tissues. The profiles were significantly different during primary SIV infection in macaques (SIVmac); that is, there was a delayed increase in IL-10 levels accompanied by moderate and persistent increases in TGF-β levels. Together, our data show that SIVagm infection is associated with an immediate antiinflammatory environment and suggest that TGF-β may participate in the generation of Tregs, which may prevent an aberrant chronic T cell hyperactivation.
Authors
Christopher Kornfeld, Mickaël J.-Y. Ploquin, Ivona Pandrea, Abdourahmane Faye, Richard Onanga, Cristian Apetrei, Virginie Poaty-Mavoungou, Pierre Rouquet, Jérôme Estaquier, Lorenzo Mortara, Jean-François Desoutter, Cécile Butor, Roger Le Grand, Pierre Roques, François Simon, Françoise Barré-Sinoussi, Ousmane M. Diop, Michaela C. Müller-Trutwin
Abstract
α-Defensins are abundant antimicrobial peptides in polymorphonuclear leukocytes and play an important role in innate immunity. We have previously shown that α-defensin-1 can inhibit HIV-1 replication following viral entry. Here we examined the molecular mechanism(s) of α-defensin-1–mediated HIV-1 inhibition. α-Defensin-1 had a direct effect on HIV-1 virions at a low MOI in the absence of serum. The direct effect on HIV-1 virions was abolished by the presence of serum or an increase in virus particles. Studying the kinetics of the HIV life cycle revealed that α-defensin-1 inhibited steps following reverse transcription and integration. Analysis of PKC phosphorylation in primary CD4+ T cells in response to α-defensin-1 indicated that α-defensin-1 inhibited PKC activity. Pretreatment of infected CD4+ T cells with a PKC activator, bryostatin 1, partially reversed α-defensin-1–mediated HIV inhibition. Like α-defensin-1, the PKC isoform–selective inhibitor Go6976 blocked HIV-1 infection in a dose-dependent manner. Furthermore, kinetic studies and analysis of HIV-1 products indicated that α-defensin-1 and Go6976 blocked HIV-1 infection at similar stages in its life cycle, including nuclear import and transcription. Taken together, our studies demonstrate that, in the absence of serum, α-defensin-1 may act directly on the virus, but, in the presence of serum, its effects are on the cell, where it inhibits HIV-1 replication. At least 1 of the cellular effects associated with HIV inhibition is interference with PKC signaling in primary CD4+ T cells. Studying the complex function of α-defensin-1 in innate immunity against HIV has implications for prevention as well as therapeutics.
Authors
Theresa L. Chang, Jesus Vargas Jr., Armando DelPortillo, Mary E. Klotman
Copyright © 2026 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)