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The Role of Glycosphingolipids in HIV/AIDS


HIV-1 Latency and Eradication of Long-term Viral Reservoirs

Abstract: HIV-1 infection is characterized by a continuous viral replication throughout the illness that can be controlled to some extent by effective treatment. Early during primary infection, latent reservoirs where the virus remains hidden in metabolically inert cells are established. These reservoirs are responsible for a low-rate viral replication that can be observed even during effective treatment and are a major obstacle for the complete eradication of the infection. This low-rate viral replication also comes from anatomical sites where drug penetration is limited and only a suboptimal drug concentration can be achieved. Further understanding of the mechanisms underlying HIV-1 latency is of primary importance to develop new strategies that ensure the complete destruction of reservoirs and, therefore, the eradication of the infection. ... Read more

Interplay Between microRNAs, Toll-like Receptors, and HIV-1: Potential Implications in HIV-1 Replication and Chronic Immune Activation

Abstract: MicroRNAs (miRNAs) are important cellular, small non-coding RNAs that regulate host gene expression and have well-characterized roles in inflammation and infectious diseases. It has become apparent as well that cellular miRNAs can play crucial roles in controlling HIV-1 infection and replication. Whether HIV-1 encodes and is able to express viral miRNAs in infected cells remains controversial. HIV-1 can manipulate the biogenesis of miRNAs as well as the expression profiles of cellular miRNAs. Toll-Like receptors (TLRs) are important pathogen recognition receptors that sense invading pathogens orchestrating innate and adaptive immune responses. Innate immune recognition of HIV-1 infection leads to activation of TLR7/8. Recent evidence has shown that certain miRNAs can also be recognized by TLR7/8 leading to immune activation. However, the potential TLR7/8-mediated recognition of HIV-1 encoded miRNAs and/or cellular miRNAs modulated in HIV-1 infected cells has not been experimentally explored. In this review, we summarize the current literature on HIV-1 infection and miRNAs. Furthermore, we underscore the need for future research on potential miRNA-induced activation of TLR7/8, which might contribute to the chronic immune activation observed in HIV-1 infected patients. ... Read more

A Feedback Regulatory Pathway Between LDL and Alpha 1 Proteinase Inhibitor in Chronic Inflammation and Infection

Abstract: Dietary lipids are transported via lymph to the liver and transformed to lipoproteins which bind to members of the low density lipoprotein receptor family (LDL-RFMs). Certain LDL-RFMs, e.g., very low density lipoprotein receptor (VLDLR), are also bound by inactivated proteinase inhibitors, the most abundant being α1proteinase inhibitor (α1PI, α1antitrypsin). Inflammation/infection, including HIV-1 infection, is accompanied by low levels of CD4+ T cells and active α1PI and high levels of inactivated α1PI. By inducing LDL-RFMs-mediated cellular locomotion, active α1PI regulates the number of CD4+ T cells. We sought to investigate whether CD4+ T cells and α1PI directly impact lipoprotein levels. At the cellular level, we show that active α1PI is required for VLDLR-mediated uptake of receptor-associated cargo, specifically CD4-bound HIV-1. We show that active α1PI levels linearly correlate with LDL levels in HIV-1 infected individuals (P<0.001) and that therapeutic, weekly infusions of active α1PI elevate the number of CD4+ T cells and HDL levels while lowering LDL levels in patients on antiretroviral therapy with controlled HIV-1. Based on the unusual combination of lipodystrophy and low levels of α1PI and CD4+ T cells in HIV-1 disease, we reveal that LDL and α1PI participate in a feedback regulatory pathway. We demonstrate integral roles for sequentially acting active and inactive α1PI in the uptake and recycling of receptors and cargo aggregated with VLDLR including CD4 and chemokine receptors. Evidence supports a role for α1PI as a primary sentinel to deploy the immune system as a consequence of its role in lipoprotein transport. ... Read more

Optimizing siRNA Delivery to the Genital Mucosa

Abstract: RNA interference (RNAi) describes a highly conserved pathway, present in eukaryotic cells, for regulating gene expression. Small stretches of double-stranded RNA, termed small interfering RNAs (siRNAs), utilize this pathway to bind homologous mRNA, resulting in site-specific mRNA cleavage and subsequent protein degradation. The ubiquitous presence of the RNAi machinery, combined with its specificity and efficacy, makes it an attractive mechanism for reducing aberrant gene expression in therapeutic settings. However, a major obstacle to utilizing RNAi in the clinic is siRNA delivery. Administered siRNAs must make contact with the appropriate cell types and, following internalization, gain access to the cytosol where the RNAi machinery resides. This must be achieved so that silencing is maximized, whilst minimizing any undesirable off-target effects. Recently, the utility of siRNAs as a microbicide, usually applied to the genital mucosa for preventing transmission of sexually transmitted diseases including HIV-1 and HSV-2, has been investigated. In this review we will describe these studies and discuss potential strategies for improving gene silencing. ... Read more

Some Unmet Challenges in the Immunology of Viral Infections

Abstract: Viral immunology is a rapidly evolving field. Major strides have been made in our understanding of innate and adaptive immune responses to viruses, largely based on highly reductionistic animal infection models, but more recently in humans, with validation that fundamental immunological concepts do in fact translate into clinical science well. From these studies there has emerged an appreciation of the enormous complexity of the immune response to viral infections as well as the diverse array of strategies developed by viruses to deal with immune detection. In this review, we highlight some of the major challenges we face in unraveling this complexity and summarize current efforts under way to improve the efficacy of viral vaccines. ... Read more

New Paradigms for Generating Effective CD8+ T Cell Responses Against HIV-1/AIDS

Abstract: CD8+ CTL responses are critical for eliminating virus infected cells in acute infection and in controlling virus replication during chronic infection. Despite evidence of potent HIV-1-specific CD8+ CTL responses during the earliest stage of acute infection leading to replacement of founder virus sequence(s) and resolution of peak viral load, in the majority of infected individuals, these responses are inadequate to prevent the establishment or control of persistent infection. Protective CD8+ CTL responses have yet to be achieved by vaccine approaches for HIV-1 or other viruses causing persistent infections, Mycobacterium tuberculosis, malaria, and cancer. Understanding the limitations of CD8+ CTL responses to keep pace with the diversity of rapidly evolving virus in the case of HIV-1 and HCV and to overcome the diverse and complex mechanisms persistent pathogens employ to escape immune recognition should lead to more effective prophylactic and therapeutic approaches for these diseases. Recent technological advances including single genome amplification (SGA) of plasma viral RNA along with direct amplicon sequencing to identify virus quasispecies, bioinformatics, and statistical methods for the systematic identification of HLA-class I associated escape mutations, and mathematical models that better define the kinetics of virus replication and decay, have provided significant insight into mechanisms of viral transmission and sequence evolution, virus-host interactions, and HIV-1 pathogenesis. In this review we attempt to integrate recent findings from studies in HIV-1, persistent virus infections, and cancer that predict effective T cell responses and suggest approaches that could shift the balance of control in favor of the host immune response. Here, we highlight factors considered essential for effective HIV-1 vaccine CD8+ T cell responses: vaccine antigens, quality, magnitude and breadth, mucosal targeting, and formation of CD8+ T cell mucosal memory. ... Read more

Where Does HIV Hide?

Abstract: HIV can be suppressed but can rarely be eradicated from the infected host. Under certain circumstances, HIV becomes dormant or latent, hiding in certain cells. One strategy is to bait them out and kill them. ... Read more

All Eyes on the Next Generation of HIV Vaccines: Strategies for Inducing a Broadly Neutralizing Antibody Response

Abstract: HIV-1 broadly neutralizing antibodies (BNAbs) develop after several years of infection through a recursive process of memory B cell adaptation and maturation against co-evolving virus quasispecies. Advances in single-cell sorting and memory B cell antibody cloning methods have identified many new HIV BNAbs targeting conserved epitopes on the HIV envelope (env) protein. 3D crystal structures and biophysical analyses of BNAbs bound to invariant virus structures expressed on monomeric gp120, epitope scaffolds, core structures, and native trimers have helped us to visualize unique binding interactions and paratope orientations that have been instrumental in guiding vaccine design. A paradigm shift in the approach to structure-based design of HIV-1 envelope immunogens came recently after several laboratories discovered that native viral envelopes or "env-structures" reverse-engineered to bind with high affinity to a handful of broadly neutralizing antibodies did not in fact bind the predicted germline precursors of these broadly neutralizing antibodies. A major challenge for HIV-1 B cell vaccine development moving forward is the design of new envelope immunogens that can trigger the selection and expansion of germline precursor and intermediate memory B cells to recapitulate B cell ontogenies associated with the maturation of a broadly neutralizing antibody response. Equally important for vaccine development is the identification of delivery systems, prime-boost strategies, and synergistic adjuvant combinations that can induce the magnitude and quality of antigen-specific T follicular helper (TFH) cell responses needed to drive somatic hypermutation (SHM) and B cell maturation against heterologous primary virus envelopes. Finding the combination of multi-protein envelope immunogens and immunization strategies that can evolve a potent broadly neutralizing antibody response portends to require a complex vaccine regimen that might be difficult to implement on any scale. This perspective strives to integrate recent insights into mechanisms associated with the evolution of an HIV-1 broadly neutralizing antibody response with current immunogen design and proffers a novel immunization strategy for skewing TH17/TFH cell responses that can drive B cell adaptation and affinity maturation associated with a broadly neutralizing antibody response. ... Read more

Aging, Immunity, and Cancer

Abstract: Age is the most important risk factor for tumorigenesis. More than 60% of new cancers and more than 70% of cancer deaths occur in elderly subjects >65 years. The immune system plays an important role in the battle of the host against cancer development. Deleterious alterations occur to the immune response with aging, termed immunosenescence. It is tempting to speculate that this waning immune response contributes to the higher incidence of cancer, but robust data on this important topic are few and far between. This review is devoted to discussing state of the art knowledge on the relationship between immunosenescence and cancer. Emerging understanding of the aging process at the molecular level is viewed from the perspective of this increased tumorigenesis. We also consider some of the most recent means to intervene in the modulation of immunosenescence to increase the ability of the immune system to fight against tumors. Future research will unravel new aspects of the immune response against tumors which will be modulable to decrease the burden of cancer in elderly individuals. ... Read more

New Insight into Clinical Development of Nucleic Acid Aptamers

Abstract: Nucleic acid-based aptamers have been shown as high-affinity ligands and potential antagonists of disease-associated proteins. Aptamers, isolated from combinatorial libraries by an iterative in vitro selection process, discriminate between closely related targets and are characterized by high specificity and low toxicity thus representing a valid alternative to antibodies to target specific proteins of biomedical interest. Moreover, they are non-immunogenic and can be easily stabilized by chemical modifications thus expanding their therapeutic potential. Here, we will focus on the structural and functional features of aptamers that have entered the clinical development pipeline together with those aptamers holding great potential as therapeutics in preclinical studies. The future perspectives of aptamers as therapeutics will be discussed as well. ... Read more

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