Chemokine receptors as HIV-1 coreceptors: roles in viral entry, tropism, and disease

Characterization of a CXCR4 antagonist TIQ-15 with dual tropic HIV entry inhibition properties

The chemokine co-receptors CXCR4 and CCR5 mediate HIV entry and signal transduction necessary for viral infection. However, to date only the CCR5 antagonist maraviroc is approved for treating HIV-1 infection. Given that approximately 50% of late-stage HIV patients also develop CXCR4-tropic virus, clinical anti-HIV CXCR4 antagonists are needed. Here, we describe a novel allosteric CXCR4 antagonist TIQ-15 which inhibits CXCR4-tropic HIV-1 infection of primary and transformed CD4 T cells. TIQ-15 blocks HIV entry with an IC50 of 13 nM. TIQ-15 also inhibits SDF-1α/CXCR4-mediated cAMP production, cofilin activation, and chemotactic signaling. In addition, TIQ-15 induces CXCR4 receptor internalization without affecting the levels of the CD4 receptor, suggesting that TIQ-15 may act through a novel allosteric site on CXCR4 for blocking HIV entry. Furthermore, TIQ-15 did not inhibit VSV-G pseudotyped HIV-1 infection, demonstrating its specificity in blocking CXCR4-tropic virus entry, but not CXCR4-independent endocytosis or post-entry steps. When tested against a panel of clinical isolates, TIQ-15 showed potent inhibition against CXCR4-tropic and dual-tropic viruses, and moderate inhibition against CCR5-tropic isolates. This observation was followed by a co-dosing study with maraviroc, and TIQ-15 demonstrated synergistic activity. In summary, here we describe a novel HIV-1 entry inhibitor, TIQ-15, which potently inhibits CXCR4-tropic viruses while possessing low-level synergistic activities against CCR5-tropic viruses. TIQ-15 could potentially be co-dosed with the CCR5 inhibitor maraviroc to block viruses of mixed tropisms.

G protein-coupled receptor (GPCR) pharmacogenomics

The field of pharmacogenetics, the investigation of the influence of one or more sequence variants on drug response phenotypes, is a special case of pharmacogenomics, a discipline that takes a genome-wide approach. Massively parallel, next generation sequencing (NGS), has allowed pharmacogenetics to be subsumed by pharmacogenomics with respect to the identification of variants associated with responders and non-responders, optimal drug response, and adverse drug reactions. A plethora of rare and common naturally-occurring GPCR variants must be considered in the context of signals from across the genome. Many fundamentals of pharmacogenetics were established for G protein-coupled receptor (GPCR) genes because they are primary targets for a large number of therapeutic drugs. Functional studies, demonstrating likely-pathogenic and pathogenic GPCR variants, have been integral to establishing models used for in silico analysis. Variants in GPCR genes include both coding and non-coding single nucleotide variants and insertion or deletions (indels) that affect cell surface expression (trafficking, dimerization, and desensitization/downregulation), ligand binding and G protein coupling, and variants that result in alternate splicing encoding isoforms/variable expression. As the breadth of data on the GPCR genome increases, we may expect an increase in the use of drug labels that note variants that significantly impact the clinical use of GPCR-targeting agents. We discuss the implications of GPCR pharmacogenomic data derived from the genomes available from individuals who have been well-phenotyped for receptor structure and function and receptor-ligand interactions, and the potential benefits to patients of optimized drug selection. Examples discussed include the renin-angiotensin system in SARS-CoV-2 (COVID-19) infection, the probable role of chemokine receptors in the cytokine storm, and potential protease activating receptor (PAR) interventions. Resources dedicated to GPCRs, including publicly available computational tools, are also discussed.

Unraveling clinical outcomes of long-term cART treatment in HIV-1 patients with or without the Brazilian GWGR motif in the V3 loop

The presence of genetic mutations in HIV poses a significant challenge, potentially leading to antiretroviral resistance and hampering therapeutic development. The Brazilian population has presented variations in the HIV envelope V3 loop gene, especially the GWGR motif. This motif has been linked to reduced transmission potential and slower CD4+ T cell decline. This study aimed to assess clinical outcomes in patients with HIV-1 infected with strains containing the GWGR motif compared with those without it during long-term cART. A cohort of 295 patients with HIV was examined for the GWGR motif presence in the V3 loop. A total of 58 samples showed the GWGR signature, while 237 had other signatures. Multifactorial analyses showed no significant differences in demographic characteristics, CD4+ cell count, AIDS progression, or mortality between GWGR carriers and others. However, the mean interval between the first positive HIV test and the initial AIDS-defining event was more than two times longer for women carrying the GWGR signature (p = 0.0231). We emphasize the positive impact of cART on HIV/AIDS treatment, including viral suppression, CD4+ cell preservation, and immune function maintenance. Although no significant differences were found during cART, residual outcomes reflecting adherence challenges were observed between diagnosis and the first AIDS-defining event. The previously described outcomes, highlighting statistically significant differences between individuals carrying the GPGR motif compared with those with the Brazilian GWGR motif, may be directly linked to the natural progression of infection before advancements in cART. Presently, these physicochemical aspects may no longer hold the same relevance.

The complex nature of CXCR4 mutations in WHIM syndrome

Heterozygous autosomal dominant mutations in the CXCR4 gene cause WHIM syndrome, a severe combined immunodeficiency disorder. The mutations primarily affect the C-terminal region of the CXCR4 chemokine receptor, specifically several potential phosphorylation sites critical for agonist (CXCL12)-mediated receptor internalization and desensitization. Mutant receptors have a prolonged residence time on the cell surface, leading to hyperactive signaling that is responsible for some of the symptoms of WHIM syndrome. Recent studies have shown that the situation is more complex than originally thought, as mutant WHIM receptors and CXCR4 exhibit different dynamics at the cell membrane, which also influences their respective cellular functions. This review examines the functional mechanisms of CXCR4 and the impact of WHIM mutations in both physiological and pathological conditions.

Development of Anti-HIV Therapeutics: From Conventional Drug Discovery to Cutting-Edge Technology

The efforts to discover HIV therapeutics have continued since the first human immunodeficiency virus (HIV) infected patient was confirmed in the 1980s. Ten years later, the first HIV drug, zidovudine (AZT), targeting HIV reverse transcriptase, was developed. Meanwhile, scientists were enlightened to discover new drugs that target different HIV genes, like integrase, protease, and host receptors. Combination antiretroviral therapy (cART) is the most feasible medical intervention to suppress the virus in people with HIV (PWH) and control the epidemic. ART treatment has made HIV a chronic infection rather than a fatal disease, but ART does not eliminate latent reservoirs of HIV-1 from the host cells; strict and life-long adherence to ART is required for the therapy to be effective in patients. In this review, we first discussed the scientific history of conventional HIV drug discovery since scientists need to develop more and more drugs to solve drug-resistant issues and release the side effects. Then, we summarized the novel research technologies, like gene editing, applied to HIV treatment and their contributions to eliminating HIV as a complementary therapy.

Exploring the impact of osteoprotegerin on osteoclast and precursor fusion: Mechanisms and modulation by ATP

Osteoclast (OC) differentiation, vital for bone resorption, depends on osteoclast and precursor fusion. Osteoprotegerin (OPG) inhibits osteoclast differentiation. OPG's influence on fusion and mechanisms is unclear. Osteoclasts and precursors were treated with OPG alone or with ATP. OPG significantly reduced OC number, area and motility and ATP mitigated OPG's inhibition. However, OPG hardly affected the motility of precusors. OPG downregulated fusion-related molecules (CD44, CD47, DC-STAMP, ATP6V0D2) in osteoclasts, reducing only CD47 in precursors. OPG reduced Connexin43 phosphorylated forms (P1 and P2) in osteoclasts, affecting only P2 in precursors. OPG disrupted subcellular localization of CD44, CD47, DC-STAMP, ATP6V0D2, and Connexin43 in both cell types. Findings underscore OPG's multifaceted impact, inhibiting multinucleated osteoclast and mononuclear precursor fusion through distinct molecular mechanisms. Notably, ATP mitigates OPG's inhibitory effect, suggesting a potential regulatory role for the ATP signaling pathway. This study enhances understanding of intricate processes in osteoclast differentiation and fusion, offering insights into potential therapeutic targets for abnormal bone metabolism.

CXCR4: from B-cell development to B cell-mediated diseases

Chemokine receptors are members of the G protein-coupled receptor superfamily. The C-X-C chemokine receptor type 4 (CXCR4), one of the most studied chemokine receptors, is widely expressed in hematopoietic and immune cell populations. It is involved in leukocyte trafficking in lymphoid organs and inflammatory sites through its interaction with its natural ligand CXCL12. CXCR4 assumes a pivotal role in B-cell development, ranging from early progenitors to the differentiation of antibody-secreting cells. This review emphasizes the significance of CXCR4 across the various stages of B-cell development, including central tolerance, and delves into the association between CXCR4 and B cell-mediated disorders, from immunodeficiencies such as WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome to autoimmune diseases such as systemic lupus erythematosus. The potential of CXCR4 as a therapeutic target is discussed, especially through the identification of novel molecules capable of modulating specific pockets of the CXCR4 molecule. These insights provide a basis for innovative therapeutic approaches in the field.

HIV-1 Structural Proteins or Cell-Signaling Factors? That Is the Question!

The biological activity of structural HIV-1 proteins is not limited to ensuring a productive viral infection but also interferes with cellular homeostasis through intra- and extracellular signaling activation. This interference induces genomic instability, increases the lifespan of the infected cell by inhibiting apoptosis, and subverts cell senescence, resulting in unrestricted cell proliferation. HIV structural proteins are present in a soluble form in the lymphoid tissues and blood of infected individuals, even without active viral replication. The HIV matrix protein p17, the envelope glycoprotein gp120, the transenvelope protein gp41, and the capsid protein p24 interact with immune cells and deregulate the biological activity of the immune system. The biological activity of HIV structural proteins is also demonstrated in endothelial cells and some tumor cell lines, confirming the ability of viral proteins to promote cell proliferation and cancer progression, even in the absence of active viral replication. This review corroborates the hypothesis that HIV structural proteins, by interacting with different cell types, contribute to creating a microenvironment that is favorable to the evolution of cancerous pathologies not classically related to AIDS.

Defining the Effects of PKC Modulator HIV Latency-Reversing Agents on Natural Killer Cells

Background

Latency reversing agents (LRAs) such as protein kinase C (PKC) modulators can reduce rebound-competent HIV reservoirs in small animal models. Furthermore, administration of natural killer (NK) cells following LRA treatment improves this reservoir reduction. It is currently unknown why the combination of a PKC modulator and NK cells is so potent and whether exposure to PKC modulators may augment NK cell function in some way.

Methods

Primary human NK cells were treated with PKC modulators (bryostatin-1, prostratin, or the designed, synthetic bryostatin-1 analog SUW133), and evaluated by examining expression of activation markers by flow cytometry, analyzing transcriptomic profiles by RNA sequencing, measuring cytotoxicity by co-culturing with K562 cells, assessing cytokine production by Luminex assay, and examining the ability of cytokines and secreted factors to independently reverse HIV latency by co-culturing with Jurkat-Latency (J-Lat) cells.

Results

PKC modulators increased expression of proteins involved in NK cell activation. Transcriptomic profiles from PKC-treated NK cells displayed signatures of cellular activation and enrichment of genes associated with the NFκB pathway. NK cell cytotoxicity was unaffected by prostratin but significantly decreased by bryostatin-1 and SUW133. Cytokines from PKC-stimulated NK cells did not induce latency reversal in J-Lat cell lines.

Conclusions

Although PKC modulators have some significant effects on NK cells, their contribution in "kick and kill" strategies is likely due to upregulating HIV expression in CD4+ T cells, not directly enhancing the effector functions of NK cells. This suggests that PKC modulators are primarily augmenting the "kick" rather than the "kill" arm of this HIV cure approach.

Modeling HIV-1 infection and NeuroHIV in hiPSCs-derived cerebral organoid cultures

The human immunodeficiency virus (HIV) epidemic is an ongoing global health problem affecting 38 million people worldwide with nearly 1.6 million new infections every year. Despite the advent of combined antiretroviral therapy (cART), a large percentage of people with HIV (PWH) still develop neurological deficits, grouped into the term of HIV-associated neurocognitive disorders (HAND). Investigating the neuropathology of HIV is important for understanding mechanisms associated with cognitive impairment seen in PWH. The major obstacle for studying neuroHIV is the lack of suitable in vitro human culture models that could shed light into the HIV-CNS interactions. Recent advances in induced pluripotent stem cell (iPSC) culture and 3D brain organoid systems have allowed the generation of 2D and 3D culture methods that possess a potential to serve as a model of neurotropic viral diseases, including HIV. In this study, we first generated and characterized several hiPSC lines from healthy human donor skin fibroblast cells. hiPSCs were then used for the generation of microglia-containing human cerebral organoids (hCOs). Once fully characterized, hCOs were infected with HIV-1 in the presence and absence of cART regimens and viral infection was studied by cellular, molecular/biochemical, and virological assays. Our results revealed that hCOs were productively infected with HIV-1 as evident by viral p24-ELISA in culture media, RT-qPCR and RNAscope analysis of viral RNA, as well as ddPCR analysis of proviral HIV-1 in genomic DNA samples. More interestingly, replication and gene expression of HIV-1 were also greatly suppressed by cART in hCOs as early as 7 days post-infections. Our results suggest that hCOs derived from hiPSCs support HIV-1 replication and gene expression and may serve as a unique platform to better understand neuropathology of HIV infection in the brain.

CCR5 and inflammatory storm

Chemokines and their corresponding receptors play crucial roles in orchestrating inflammatory and immune responses, particularly in the context of pathological conditions disrupting the internal environment. Among these receptors, CCR5 has garnered considerable attention due to its significant involvement in the inflammatory cascade, serving as a pivotal mediator of neuroinflammation and other inflammatory pathways associated with various diseases. However, a notable gap persists in comprehending the intricate mechanisms governing the interplay between CCR5 and its ligands across diverse and intricate inflammatory pathologies. Further exploration is warranted, especially concerning the inflammatory cascade instigated by immune cell infiltration and the precise binding sites within signaling pathways. This study aims to illuminate the regulatory axes modulating signaling pathways in inflammatory cells by providing a comprehensive overview of the pathogenic processes associated with CCR5 and its ligands across various disorders. The primary focus lies on investigating the pathomechanisms associated with CCR5 in disorders related to neuroinflammation, alongside the potential impact of aging on these processes and therapeutic interventions. The discourse culminates in addressing current challenges and envisaging potential future applications, advocating for innovative research endeavors to advance our comprehension of this realm.

An in vitro study to elucidate the effects of product Nkabinde on immune response in peripheral blood mononuclear cells of healthy donors

Introduction: A significant number of the South African population still rely on traditional medicines (TM) as their primary healthcare due to their belief in their holistic healing and immune-boosting properties. However, little to no scientific data is available on the effects of most TM products on cytokine and cellular biomarkers of the immune response. Here, we evaluated the impact of traditional medicine [Product Nkabinde (PN)] in inducing cellular and cytokine biomarkers of inflammation in peripheral blood mononuclear cells (PBMCs) from eight healthy volunteers. Methods: PN was supplied by a local Traditional Health Practitioner (THP). The IC50 (half maximum concentration) of the standardized extract on isolated PBMCs was established using the cell viability assay over 24 h of incubation. Luminex and flow cytometry assays were used to measure cytokine and cellular levels in PBMCs stimulated with PN and/or PHA over 24, 48, and 72 h, respectively. Results: The IC50 concentration of PN in treated PBMCs was established at 325.3 μg/mL. In the cellular activation assay, the percentages of CD38-HLA-DR + on total CD4+ T cells were significantly increased in PBMCs stimulated with PN compared to unstimulated controls after 24 h (p = 0.008). PN significantly induced the production of anti-inflammatory IL-10 (p = 0.041); proinflammatory cytokines IL-1α (p = 0.003), TNF-α (p < 0.0001); and chemokine MIP-1β (p = 0.046) compared to the unstimulated control after 24 h. At 48 h incubation, the production of proinflammatory cytokines IL-1α (p = 0.034) and TNF-α (p = 0.011) were significantly induced following treatment with PN. Conclusion: We conclude that the PN possesses in vitro immunomodulatory properties that may influence immune and inflammatory responses. More studies using PN are needed to further understand key parameters mediating induction, expression, and regulation of the immune response in the context of pathogen-associated infections.

Broad-spectrum antiviral strategy: Host-targeting antivirals against emerging and re-emerging viruses

Viral infections are amongst the most prevalent diseases that pose a significant threat to human health. Targeting viral proteins or host factors represents two primary strategies for the development of antiviral drugs. In contrast to virus-targeting antivirals (VTAs), host-targeting antivirals (HTAs) offer advantages in terms of overcoming drug resistance and effectively combating a wide range of viruses, including newly emerging ones. Therefore, targeting host factors emerges as an extremely promising strategy with the potential to address critical challenges faced by VTAs. In recent years, extensive research has been conducted on the discovery and development of HTAs, leading to the approval of maraviroc, a chemokine receptor type 5 (CCR5) antagonist used for the treatment of HIV-1 infected individuals, with several other potential treatments in various stages of development for different viral infections. This review systematically summarizes advancements made in medicinal chemistry regarding various host targets and classifies them into four distinct catagories based on their involvement in the viral life cycle: virus attachment and entry, biosynthesis, nuclear import and export, and viral release.

An emerging paradigm of CXCL12 involvement in the metastatic cascade

The chemokine CXCL12, also known as stromal cell-derived factor 1 (SDF1), has emerged as a pivotal regulator in the intricate molecular networks driving cancer progression. As an influential factor in the tumor microenvironment, CXCL12 plays a multifaceted role that spans beyond its traditional role as a chemokine inducing invasion and metastasis. Indeed, CXCL12 has been assigned functions related to epithelial-to-mesenchymal transition, cancer cell stemness, angiogenesis, and immunosuppression, all of which are currently viewed as specialized biological programs contributing to the "metastatic cascade" among other cancer hallmarks. Its interaction with its cognate receptor, CXCR4, initiates a cascade of events that not only shapes the metastatic potential of tumor cells but also defines the niches within the secondary organs that support metastatic colonization. Given the profound implications of CXCL12 in the metastatic cascade, understanding its mechanistic underpinnings is of paramount importance for the targeted elimination of rate-limiting steps in the metastatic process. This review aims to provide a comprehensive overview of the current knowledge surrounding the role of CXCL12 in cancer metastasis, especially its molecular interactions rationalizing its potential as a therapeutic target.

Arylsulfatases and neuraminidases modulate engagement of CCR5 by chemokines by removing key electrostatic interactions

The chemokine receptor CCR5 is known to exist in cell surface subpopulations that differ in their capacity to engage ligands. One proposed explanation for this phenomenon is the presence of CCR5 species with different levels of post-translational modifications (PTMs). Tyrosine sulfation and O-glycan sialylation are PTMs that add negative charges to the extracellular domain of CCR5 and make strong contributions to chemokine binding but it is not known whether cellular mechanisms to control their levels exist. In this study we used a combination of sulfation-sensitive and sulfation-insensitive CCR5 ligands to show that the rate of turnover of CCR5 tyrosine sulfation is more rapid than the rate of turnover of the receptor itself. This suggests that the steady state level of CCR5 sulfation is maintained through the combination of tyrosine protein sulfotransferase (TPST), the trans-Golgi network (TGN)-resident 'source enzyme, and a 'sink' activity that removes tyrosine sulfation from CCR5. By measuring the effects on ligand binding of knockdown and overexpression experiments, we provided evidence that non-lysosomal cellular arylsulfatases, particularly ARSG, ARSI and ARSJ, are CCR5 sulfation 'sink' enzymes. We also used targeted knockdown and sialylation-sensitive and insensitive chemokines to identify the sialidase NEU3 as a candidate 'sink' enzyme for CCR5 O-glycan sialylation. This study provides the first experimental evidence of activity of sulfatase and sialidase 'sink' enzymes on CCR5, providing a potential mechanism for cells to control steady-state levels of these PTMs and thereby exert dynamic control over receptor-ligand interactions at the cell surface and during receptor desensitization.

HIV-1 Induced Cell-to-Cell Fusion or Syncytium Formation

HIV-1 cell-free infection has been thoroughly investigated; however, its relevance and importance in vitro are questionable. Cell-cell transmission is now thought to be the dominant mode of transmission within the host; however precise molecular details remain elusive. The considerable potency of cell-cell transmission hinges upon its ability to hijack and manipulate host immunological function to target uninfected cells, along with overcoming restriction factors and increasing the speed of latent pool formation. Another question of relevance is virus induced cell-cell fusion and how this process is regulated. How often HIV-1 induces the formation of syncytia? Is cell-cell function a potential process for HIV-1 transmission? These questions are discussed and reviewed together with a description of the most common ways of HIV-1 entry and transinfection.

How chemokines organize the tumour microenvironment

For our immune system to contain or eliminate malignant solid tumours, both myeloid and lymphoid haematopoietic cells must not only extravasate from the bloodstream into the tumour tissue but also further migrate to various specialized niches of the tumour microenvironment to functionally interact with each other, with non-haematopoietic stromal cells and, ultimately, with cancer cells. These interactions regulate local immune cell survival, proliferative expansion, differentiation and their execution of pro-tumour or antitumour effector functions, which collectively determine the outcome of spontaneous or therapeutically induced antitumour immune responses. None of these interactions occur randomly but are orchestrated and critically depend on migratory guidance cues provided by chemokines, a large family of chemotactic cytokines, and their receptors. Understanding the functional organization of the tumour immune microenvironment inevitably requires knowledge of the multifaceted roles of chemokines in the recruitment and positioning of its cellular constituents. Gaining such knowledge will not only generate new insights into the mechanisms underlying antitumour immunity or immune tolerance but also inform the development of biomarkers (or 'biopatterns') based on spatial tumour tissue analyses, as well as novel strategies to therapeutically engineer immune responses in patients with cancer. Here we will discuss recent observations on the role of chemokines in the tumour microenvironment in the context of our knowledge of their physiological functions in development, homeostasis and antimicrobial responses.

The regulatory network of the chemokine CCL5 in colorectal cancer

The chemokine CCL5 plays a potential role in the occurrence and development of colorectal cancer (CRC). Previous studies have shown that CCL5 directly acts on tumor cells to change tumor metastatic rates. In addition, CCL5 recruits immune cells and immunosuppressive cells into the tumor microenvironment (TME) and reshapes the TME to adapt to tumor growth or increase antitumor immune efficacy, depending on the type of secretory cells releasing CCL5, the cellular function of CCL5 recruitment, and the underlying mechanisms. However, at present, research on the role played by CCL5 in the occurrence and development of CRC is still limited, and whether CCL5 promotes the occurrence and development of CRC and its role remain controversial. This paper discusses the cells recruited by CCL5 in patients with CRC and the specific mechanism of this recruitment, as well as recent clinical studies of CCL5 in patients with CRC.Key MessagesCCL5 plays dual roles in colorectal cancer progression.CCL5 remodels the tumor microenvironment to adapt to colorectal cancer tumor growth by recruiting immunosuppressive cells or by direct action.CCL5 inhibits colorectal cancer tumor growth by recruiting immune cells or by direct action.

Sulfoconjugation of protein peptides and glycoproteins in physiology and diseases

Protein sulfoconjugation, or sulfation, represents a critical post-translational modification (PTM) process that involves the attachment of sulfate groups to various positions of substrates within the protein peptides or glycoproteins. This process plays a dynamic and complex role in many physiological and pathological processes. Here, we summarize the importance of sulfation in the fields of oncology, virology, drug-induced liver injury (DILI), inflammatory bowel disease (IBD), and atherosclerosis. In oncology, sulfation is involved in tumor initiation, progression, and migration. In virology, sulfation influences viral entry, replication, and host immune response. In DILI, sulfation is associated with the incidence of DILI, where altered sulfation affects drug metabolism and toxicity. In IBD, dysregulation of sulfation compromises mucosal barrier and immune response. In atherosclerosis, sulfation influences the development of atherosclerosis by modulating the accumulation of lipoprotein, and the inflammation, proliferation, and migration of smooth muscle cells. The current review underscores the importance of further research to unravel the underlying mechanisms and therapeutic potential of targeting sulfoconjugation in various diseases. A better understanding of sulfation could facilitate the emergence of innovative diagnostic or therapeutic strategies.

A bibliometric analysis: Ca2+ fluxes and inflammatory phenotyping by flow cytometry in peripheral blood mononuclear cells

Background

The immune system, composed of organs, tissues, cells, and proteins, is the key to protecting the body from external biological attacks and inflammation. The latter occurs in several pathologies, such as cancers, type 1 diabetes, and human immunodeficiency virus infection. Immunophenotyping by flow cytometry is the method of choice for diagnosing these pathologies. Under inflammatory conditions, the peripheral blood mononuclear cells (PBMCs) are partially activated and generate intracellular pathways involving Ca2+-dependent signaling cascades leading to transcription factor expression. Ca2+ signaling is typically studied by microscopy in cell lines but can present some limitations to explore human PBMCs, where flow cytometry can be a good alternative.

Objective

In this review, we dived into the research field of inflammation and Ca2+ signaling in PBMCs. We aimed to investigate the structure and evolution of this field in a physio-pathological context, and then we focused our review on flow cytometry analysis of Ca2+ fluxes in PBMCs.

Methods

From 1984 to 2022, 3865 articles on inflammation and Ca2+ signaling in PBMCs were published, according to The Clarivate Web of Science (WOS) database used in this review. A bibliometric study was designed for this collection and consisted of a co-citation and bibliographic coupling analysis.

Results

The co-citation analysis was performed on 133 articles: 4 clusters highlighted the global context of Ca2+ homeostasis, including chemical probe development, identification of the leading players in Ca2+ signaling, and the link with chemokine production in immune cell function. Next, the bibliographic coupling analysis combined 998 articles in 8 clusters. This analysis outlined the mechanisms of PBMC activation, from signal integration to cellular response. Further explorations of the bibliographic coupling network, focusing on flow cytometry, revealed 21 articles measuring cytosolic Ca2+ in PBMCs, with only 5 since 2016. This final query showed that Ca2+ signaling analysis in human PBMCs using flow cytometry is still underdeveloped and investigates mainly the cytosolic Ca2+ compartment.

Conclusion

Our review uncovers remaining knowledge gaps of intracellular players involved in Ca2+ signaling in PBMCs, such as reticulum and mitochondria, and presents flow cytometry as a solid option to supplement gold-standard microscopy studies.

Progress in Pathological and Therapeutic Research of HIV-Related Neuropathic Pain

HIV-related neuropathic pain (HRNP) is a neurodegeneration that gradually develops during the long-term course of acquired immune deficiency syndrome (AIDS) and manifests as abnormal sock/sleeve-like symmetrical pain and nociceptive hyperalgesia in the extremities, which seriously reduces patient quality of life. To date, the pathogenesis of HRNP is not completely clear. There is a lack of effective clinical treatment for HRNP and it is becoming a challenge and hot spot for medical research. In this study, we conducted a systematic review of the progress of HRNP research in recent years including (1) the etiology, classification and clinical symptoms of HRNP, (2) the establishment of HRNP pathological models, (3) the pathological mechanisms underlying HRNP from three aspects: molecules, signaling pathways and cells, (4) the therapeutic strategies for HRNP, and (5) the limitations of recent HRNP research and the future research directions and prospects of HRNP. This detailed review provides new and systematic insight into the pathological mechanism of HRNP, which establishes a theoretical basis for the future exploitation of novel target drugs. HIV infection, antiretroviral therapy and opioid abuse contribute to the etiology of HRNP with symmetrical pain in both hands and feet, allodynia and hyperalgesia. The pathogenesis involves changes in cytokine expression, activation of signaling pathways and neuronal cell states. The therapy for HRNP should be patient-centered, integrating pharmacologic and nonpharmacologic treatments into multimodal intervention.

Peptide Bispecifics Inhibiting HIV-1 Infection by an Orthogonal Chemical and Supramolecular Strategy

Viral infections pose a significant threat to human health, and effective antiviral strategies are urgently needed. Antiviral peptides have emerged as a promising class of therapeutic agents due to their unique properties and mechanisms of action. While effective on their own, combining antiviral peptides may allow us to enhance their potency and to prevent viral resistance. Here, we developed an orthogonal chemical strategy to prepare a heterodimeric peptide conjugate assembled on a protein-based nanoplatform. Specifically, we combined the optimized version of two peptides inhibiting HIV-1 by distinct mechanisms. Virus-inhibitory peptide (VIRIP) is a 20 amino acid fragment of α1-antitrypsin that inhibits HIV-1 by targeting the gp41 fusion peptide. Endogenous peptide inhibitor of CXCR4 (EPI-X4) is a 16-residue fragment of human serum albumin that prevents HIV-1 entry by binding to the viral CXCR4 co-receptor. Optimized forms of both peptides are assembled on supramolecular nanoplatforms through the streptavidin-biotin interaction. We show that the construct consisting of the two different peptides (SAv-VIR-102C9-EPI-X4 JM#173-C) shows increased activity against CCR5- and CXCR4-tropic HIV-1 variants. Our results are a proof of concept that peptides with different modes of action can be assembled on nanoplatforms to enhance their antiviral activity.

The Chemical Inhibitors of Endocytosis: From Mechanisms to Potential Clinical Applications

Endocytosis is one of the major ways cells communicate with their environment. This process is frequently hijacked by pathogens. Endocytosis also participates in the oncogenic transformation. Here, we review the approaches to inhibit endocytosis, discuss chemical inhibitors of this process, and discuss potential clinical applications of the endocytosis inhibitors.

Prevalence of R5 and X4-Tropic strains in HIV-1 Infected bangladeshi population

PURPOSE

HIV uses CD4 as main receptor to infect a cell. Also, it uses coreceptor (CCR5 or CXCR4) as a surrogate marker. In Bangladesh, nearly 50% of the identified strains are subtype C. In this study, we have examined viral genotypic co-receptor tropism in Bangladesh People Living with HIV (PLHIV).

METHODS

We identified a co-receptor on V3 sequences of the HIV env gene. The online Geno2pheno tools was used. The threshold limit of a 10% false-positive rate was used. Samples from HIV-infected individuals aged 5-50 years were taken from which we obtained a good quality of 55 sequences. The viral tropism frequency in different circulating Bangladeshi HIV subtypes was analyzed using SPSS.

RESULTS

Above two third of the samples, (61.8%; 34 of 55) were HIV-1 subtype C. We identified 83.6% (46 of 55) of the samples were R5tropic, 16.4% (9 of 55) as X4 tropic, HIV-1 strains. The R5 tropic strains among key population infected with different HIV-1 subtype in the Bangladeshi population is common.

CONCLUSIONS

This finding can help with suitable drug selection in reverse-transcriptase (RT) or protease (PR) drug-resistance strains.

Structural dynamics of chemokine receptors

Membrane proteins such as G protein-coupled receptors (GPCRs) are involved in awide range of physiological and pathological cellular processes. Binding of extracellular signals to GPCRs, including hormones, neurotransmitters, peptides and proteins, can activate intracellular signaling cascades via G protein interaction. Chemokine receptors are key GPCRs implicated in cancers, immune responses, cell migration and inflammation. Specifically, the CCR5 and CXCR4 chemokine receptors serve as important therapeutic targets against Human Immunodeficiency virus (HIV) entry into human cells. Maraviroc and Vicriviroc, two clinically used HIV entry inhibitors, are antagonists of the CCR5 receptor. These drugs block HIV entry, but ultimately resistance develops, due to emergence of viruses that can utilize the CXCR4 co-receptor. Unfortunately, development of chemokine receptor antagonists as selective drugs of HIV infection has been greatly hindered as their target orthosteric site is conserved among different receptor subtypes. Accordingly, it is important to understand the structural dynamics of these receptors to develop more effective therapeutics. In this chapter, we describe the latest advances in studies of these two key chemokine receptors with respect to their structures, dynamics and function.

Metamodulation of presynaptic NMDA receptors: New perspectives for pharmacological interventions

Metamodulation shifted the scenario of the central neuromodulation from a simplified unimodal model to a multimodal one. It involves different receptors/membrane proteins physically associated or merely colocalized that act in concert to control the neuronal functions influencing each other. Defects or maladaptation of metamodulation would subserve neuropsychiatric disorders or even synaptic adaptations relevant to drug dependence. Therefore, this "vulnerability" represents a main issue to be deeply analyzed to predict its aetiopathogenesis, but also to propose targeted pharmaceutical interventions. The review focusses on presynaptic release-regulating NMDA receptors and on some of the mechanisms of their metamodulation described in the literature. Attention is paid to the interactors, including both ionotropic and metabotropic receptors, transporters and intracellular proteins, which metamodulate their responsiveness in physiological conditions but also undergo adaptation that are relevant to neurological dysfunctions. All these structures are attracting more and more the interest as promising druggable targets for the treatment of NMDAR-related central diseases: these substances would not exert on-off control of the colocalized NMDA receptors (as usually observed with NMDAR full agonists/antagonists), but rather modulate their functions, with the promise of limiting side effects that would favor their translation from preclinic to clinic.

Cell-to-Cell Transmission of HIV-1 and HIV-2 from Infected Macrophages and Dendritic Cells to CD4+ T Lymphocytes

Macrophages (Mø) and dendritic cells (DCs) are key players in human immunodeficiency virus (HIV) infection and pathogenesis. They are essential for the spread of HIV to CD4+ T lymphocytes (TCD4+) during acute infection. In addition, they constitute a persistently infected reservoir in which viral production is maintained for long periods of time during chronic infection. Defining how HIV interacts with these cells remains a critical area of research to elucidate the pathogenic mechanisms of acute spread and sustained chronic infection and transmission. To address this issue, we analyzed a panel of phenotypically distinct HIV-1 and HIV-2 primary isolates for the efficiency with which they are transferred from infected DCs or Mø to TCD4+. Our results show that infected Mø and DCs spread the virus to TCD4+ via cell-free viral particles in addition to other alternative pathways. We demonstrate that the production of infectious viral particles is induced by the co-culture of different cell populations, indicating that the contribution of cell signaling driven by cell-to-cell contact is a trigger for viral replication. The results obtained do not correlate with the phenotypic characteristics of the HIV isolates, namely their co-receptor usage, nor do we find significant differences between HIV-1 and HIV-2 in terms of cis- or trans-infection. The data presented here may help to further elucidate the cell-to-cell spread of HIV and its importance in HIV pathogenesis. Ultimately, this knowledge is critical for new therapeutic and vaccine approaches.

A 16-color full spectrum flow cytometric analysis for comprehensive evaluation of T-cell reconstitution in SIV-infected rhesus macaques

T-cell reconstitution is central in human immunodeficiency virus (HIV) infection/disease progression. Simian immunodeficiency virus (SIV)-infected rhesus macaques (Macaca mulatta) have been the most widely used animal model for HIV research so far. An effective flow cytometry panel is crucial for monitoring the T cell reconstitution in SIV infection progression. We developed this sixteen-color flow cytometry-based panel for a T cell subsets analysis by manual gating and, once successfully gated, to characterize T cells function in-depth in rhesus macaques. This panel included markers to characterize CD4+ T cells and CD8+ T cells, T regulatory cells (Tregs), and T cell differentiation status (CD45RA and CCR7). Additionally, we included antibodies that measure T cell activation and proliferation molecules (CD69, HLA-DR, CD38 and Ki67), antibodies that examine the expressions of key PD-1 pathway molecule (PD-1), SIV potential target (CD32) and the primary SIV co-receptor CCR5 (CD195). High-dimensional single cell analysis was also performed to identify CD3+ T cells immunophenotypes of SIV-infected rhesus macaques. We designed this panel to evaluate the responses of different T cell subsets to SIV in whole blood from SIV-infected rhesus macaques.

A SERS based clinical study on HIV-1 viral load quantification and determination of disease prognosis

In resource limited settings, a cost-effective point-of-care diagnostic testing possessing the characteristics of detecting the minimum viral load of a malady like human immunodeficiency virus (HIV) acquired immune deficiency syndrome (AIDS) is a pressing priority. The present work describes a novel, rapid and field-deployable method using surface enhanced Raman spectroscopy (SERS) for detection and prognosis of HIV positive clinical samples, in seven different viral load ranges varying between 200 and 1 million copies/ml. A relationship between the increasing and decreasing intensity peaks of HIV-1 was also established for quantitation efficacy of the handheld tool. Three different types of SERS substrates: single arm Ag nanorods, double arm Ag nanorods and Au sputtered single arm Ag nanorods were used and the obtained data was compared for the three substrates. It was demonstrated that maximum enhancement was obtained for Au sputtered Ag nanorods. Rigorous coupled wave analysis (RCWA) simulations were performed to study the 'hotspots' in three different SERS substrates. Further, to explore the utility of our platform and to differentiate between the clade specific X4 and R5 tropism, their corresponding SERS spectra were studied using HIV-1 strains belonging to four different HIV-1 subtypes (A, B, C and D) which showed a clear distinction, implying the usefulness of the platform in understanding the disease prognosis. Statistical analysis of the obtained SERS spectra using principal component analysis (PCA) showed good agreement with the experimental results, confirming the ability of SERS platform to quantitate HIV-1 viral load and distinguish HIV-1 strains on the basis of their SERS spectra.

Utilizing the codon adaptation index to evaluate the susceptibility to HIV-1 and SARS-CoV-2 related coronaviruses in possible target cells in humans

Comprehensive identification of possible target cells for viruses is crucial for understanding the pathological mechanism of virosis. The susceptibility of cells to viruses depends on many factors. Besides the existence of receptors at the cell surface, effective expression of viral genes is also pivotal for viral infection. The regulation of viral gene expression is a multilevel process including transcription, translational initiation and translational elongation. At the translational elongation level, the translational efficiency of viral mRNAs mainly depends on the match between their codon composition and cellular translational machinery (usually referred to as codon adaptation). Thus, codon adaptation for viral ORFs in different cell types may be related to their susceptibility to viruses. In this study, we selected the codon adaptation index (CAI) which is a common codon adaptation-based indicator for assessing the translational efficiency at the translational elongation level to evaluate the susceptibility to two-pandemic viruses (HIV-1 and SARS-CoV-2) of different human cell types. Compared with previous studies that evaluated the infectivity of viruses based on codon adaptation, the main advantage of our study is that our analysis is refined to the cell-type level. At first, we verified the positive correlation between CAI and translational efficiency and strengthened the rationality of our research method. Then we calculated CAI for ORFs of two viruses in various human cell types. We found that compared to high-expression endogenous genes, the CAIs of viral ORFs are relatively low. This phenomenon implied that two kinds of viruses have not been well adapted to translational regulatory machinery in human cells. Also, we indicated that presumptive susceptibility to viruses according to CAI is usually consistent with the results of experimental research. However, there are still some exceptions. Finally, we found that two viruses have different effects on cellular translational mechanisms. HIV-1 decouples CAI and translational efficiency of endogenous genes in host cells and SARS-CoV-2 exhibits increased CAI for its ORFs in infected cells. Our results implied that at least in cases of HIV-1 and SARS-CoV-2, CAI can be regarded as an auxiliary index to assess cells' susceptibility to viruses but cannot be used as the only evidence to identify viral target cells.

Tracking coreceptor switch of the transmitted/founder HIV-1 identifies co-evolution of HIV-1 antigenicity, coreceptor usage and CD4 subset targeting

The CCR5 (R5) to CXCR4 (X4) coreceptor switch in natural HIV-1 infection is associated with faster progression to AIDS, but the underlying mechanisms remain unclear. The difficulty in capturing the earliest moment of coreceptor switch in vivo limits our understanding of this phenomenon. Here, by tracking the evolution of the transmitted/founder (T/F) HIV-1 in a prospective cohort of individuals at risk for HIV-1 infection identified very early in acute infection, we investigated this process with high resolution. The earliest X4 variants evolved from the R5 tropic T/F strains. Strong X4 usage can be conferred by a single mutation. The mutations responsible for coreceptor switch can confer escape to neutralization and drive X4 variants to replicate mainly in the central memory and naïve CD4+ T cells. We propose a novel concept to explain the co-evolution of virus antigenicity and entry tropism termed "escape by shifting". This concept posits that for viruses with receptor or coreceptor flexibility, entry tropism alteration represents a mechanism of immune evasion in vivo .

Anatomical and physiological aspects of the HIV infection pathogenesis in animal models

Understanding the entire pathogenesis of HIV infection, from penetration at the gates of infection to the induction of severe immunodeficiency, is an essential tool for the development of new treatment methods. Less than 40 years of research into the mechanisms of HIV infection that lead to the development of acquired immunodeficiency syndrome have accumulated a huge amount of information, but HIV's own unique variability identifies new whitespaces. Despite the constant improvement of the protocols of antiretroviral therapy and the success of its use, it has not yet been possible to stop the spread of HIV infection. The development of new protocols and the testing of new groups of antiretroviral drugs is possible, first of all, due to the improvement of animal models of the HIV infection pathogenesis. Their relevance, undoubtedly increases, but still depends on specific research tasks, since none of the in vivo models can comprehensively simulate the mechanism of the infection pathology in humans which leads to multi-organ damage. The aim of the review was to provide up-to-date information on known animal models of HIV infection, focusing on the method of their infection and anatomical, physiological and pathological features.

Discovery of Chemokine CXCL12 Inhibitors by Tandem Application of Virtual Screening and NMR Spectrometry

The CXC chemokine ligand CXCL12 and its receptor CXCR4 play critical roles in stem-cell homing, infectious diseases, and cancer, which led the CXCL12/CXCR4 signaling axis to attract much attention in drug discovery. CXCR4 is regarded as the primary target while CXCL12 is considered too small to be a druggable target. In this paper, we employed virtual screening approaches and ligand-based NMR screening methods from a SPECS library and in-house natural products to discover new CXCR12 inhibitors. Four natural triterpene saponins were confirmed, and the triterpene sapogenin was identified as the main binding epitope by saturation transfer difference-nuclear magnetic resonance and molecular docking studies. The pentacyclic triterpene scaffold and its elucidated structure-activity relationships provide a new and valuable research direction for the development of novel CXCL12 inhibitors.

Anti-chemokine antibodies after SARS-CoV-2 infection correlate with favorable disease course

Infection by SARS-CoV-2 leads to diverse symptoms, which can persist for months. While antiviral antibodies are protective, those targeting interferons and other immune factors are associated with adverse COVID-19 outcomes. Instead, we discovered that antibodies against specific chemokines are omnipresent after COVID-19, associated with favorable disease, and predictive of lack of long COVID symptoms at one year post infection. Anti-chemokine antibodies are present also in HIV-1 infection and autoimmune disorders, but they target different chemokines than those in COVID-19. Monoclonal antibodies derived from COVID- 19 convalescents that bind to the chemokine N-loop impair cell migration. Given the role of chemokines in orchestrating immune cell trafficking, naturally arising anti-chemokine antibodies associated with favorable COVID-19 may be beneficial by modulating the inflammatory response and thus bear therapeutic potential.

One-Sentence Summary

Naturally arising anti-chemokine antibodies associate with favorable COVID-19 and predict lack of long COVID.

Host Molecule Incorporation into HIV Virions, Potential Influences in HIV Pathogenesis

During the last phase of HIV viral production, nascent HIV virions acquire a fraction of the cellular lipid membrane to create the external lipid envelope, a process by which cellular proteins present on the surface of the infected cell can be incorporated along with Env trimers. Interestingly, several studies indicated that these incorporated host molecules could conserve their biological activity and consequently contribute to HIV pathogenesis either by enhancing the infectivity of HIV virions, their tissue tropism or by affecting immune cell functions. The following review will describe the main approaches used to characterize membrane bound host molecule incorporation into HIV virions, the proposed mechanisms involved, and the role of a non-exhaustive list of incorporated molecules.

C–C chemokine receptor 5 and acute graft‐versus‐host disease

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Application of CRISPR-Cas9 Gene Editing for HIV Host Factor Discovery and Validation

Human Immunodeficiency Virus (HIV) interacts with a wide array of host factors at each stage of its lifecycle to facilitate replication and circumvent the immune response. Identification and characterization of these host factors is critical for elucidating the mechanism of viral replication and for developing next-generation HIV-1 therapeutic and curative strategies. Recent advances in CRISPR-Cas9-based genome engineering approaches have provided researchers with an assortment of new, valuable tools for host factor discovery and interrogation. Genome-wide screening in a variety of in vitro cell models has helped define the critical host factors that play a role in various cellular and biological contexts. Targeted manipulation of specific host factors by CRISPR-Cas9-mediated gene knock-out, overexpression, and/or directed repair have furthermore allowed for target validation in primary cell models and mechanistic inquiry through hypothesis-based testing. In this review, we summarize several CRISPR-based screening strategies for the identification of HIV-1 host factors and highlight how CRISPR-Cas9 approaches have been used to elucidate the molecular mechanisms of viral replication and host response. Finally, we examine promising new technologies in the CRISPR field and how these may be applied to address critical questions in HIV-1 biology going forward.

Closing the Door with CRISPR: Genome Editing of CCR5 and CXCR4 as a Potential Curative Solution for HIV

Human immunodeficiency virus (HIV) infection can be controlled by anti-retroviral therapy. Suppressing viral replication relies on life-long medication, but anti-retroviral therapy is not without risks to the patient. Therefore, it is important that permanent cures for HIV infection are developed. Three patients have been described to be completely cured from HIV infection in recent years. In all cases, patients received a hematopoietic stem cell (HSC) transplantation due to a hematological malignancy. The HSCs were sourced from autologous donors that expressed a homozygous mutation in the CCR5 gene. This mutation results in a non-functional receptor, and confers resistance to CCR5-tropic HIV strains that rely on CCR5 to enter host cells. The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated (Cas) system is one of the methods of choice for gene editing, and the CRISPR/Cas system has been employed to target loci of interest in the context of HIV. Here, the current literature regarding CRISPR-mediated genome editing to render cells resistant to HIV (re)-infection by knocking out the co-receptors CCR5 and CXCR4 is summarized, and an outlook is provided regarding future (research) directions.

Evolution of Multiple Domains of the HIV-1 Envelope Glycoprotein during Coreceptor Switch with CCR5 Antagonist Therapy

HIV-1 uses CD4 as a receptor and chemokine receptors CCR5 and/or CXCR4 as coreceptors. CCR5 antagonists are a class of antiretrovirals used to inhibit viral entry. Phenotypic prediction algorithms such as Geno2Pheno are used to assess CCR5 antagonist eligibility, for which the V3 region is screened. However, there exist scenarios where the algorithm cannot give an accurate prediction of tropism. The current study examined coreceptor shift of HIV-1 from CCR5-tropic strains to CXCR4-tropic or dual-tropic strains among five subjects in a clinical trial of the CCR5 antagonist vicriviroc. Envelope gene amplicon libraries were constructed and subjected to next-generation sequencing, as well as single-clone sequencing and functional analyses. Approximately half of the amplified full-length single envelope-encoding clones had no significant activity for infection of cells expressing high levels of CD4 and CCR5 or CXCR4. Functional analysis of 9 to 21 individual infectious clones at baseline and at the time of VF were used to construct phylogenetic trees and sequence alignments. These studies confirmed that specific residues and the overall charge of the V3 loop were the major determinants of coreceptor use, in addition to specific residues in other domains of the envelope protein in V1/V2, V4, C3, and C4 domains that may be important for coreceptor shift. These results provide greater insight into the viral genetic determinants of coreceptor shift. IMPORTANCE This study is novel in combining single-genome sequence analysis and next-generation sequencing to characterize HIV-1 quasispecies. The work highlights the importance of mutants present at frequencies of 1% or less in development of drug resistance. This study highlights a critical role of specific amino acid substitutions outside V3 that contribute to coreceptor shift as well as important roles of the V1/V2, V4, C3, and C4 domain residues.

Targeted Immuno-Antiretroviral to Promote Dual Protection against HIV: A Proof-of-Concept Study

The C-C motif chemokine receptor-5 (CCR5) expression on the T-cell surface is the prime barrier to HIV/AIDS eradication, as it promotes both active human immunodeficiency virus (HIV)-infection and latency; however, antiretrovirals (ARVs) suppress plasma viral loads to non-detectable levels. Keeping this in mind, we strategically designed a targeted ARVs-loaded nanoformulation that targets CCR5 expressing T-cells (e.g., CD4+ cells). Conceptually, CCR5-blocking and targeted ARV delivery would be a dual protection strategy to prevent HIV infection. For targeting CCR5+ T-cells, the nanoformulation was surface conjugated with anti-CCR5 monoclonal antibodies (CCR5 mAb) and loaded with dolutegravir+tenofovir alafenamide (D+T) ARVs to block HIV replication. The result demonstrated that the targeted-ARV nanoparticle’s multimeric CCR5 binding property improved its antigen-binding affinity, prolonged receptor binding, and ARV intracellular retention. Further, nanoformulation demonstrated high binding affinity to CCR5 expressing CD4+ cells, monocytes, and other CCR5+ T-cells. Finally, the short-term pre-exposure prophylaxis study demonstrated that prolonged CCR5 blockage and ARV presence further induced a “protective immune phenotype” with a boosted T-helper (Th), temporary memory (TM), and effector (E) sub-population. The proof-of-concept study that the targeted-ARV nanoformulation dual-action mechanism could provide a multifactorial solution toward achieving HIV “functional cure”.

Contribution of Sex Differences to HIV Immunology, Pathogenesis, and Cure Approaches

Approximately 38 million people were living with human immunodeficiency virus (HIV) in 2020 and 53% of those infected were female. A variety of virological and immunological sex-associated differences (sexual dimorphism) in HIV infection have been recognized in males versus females. Social, behavioral, and societal influences play an important role in how the HIV pandemic has affected men and women differently. However, biological factors including anatomical, physiologic, hormonal, and genetic differences in sex chromosomes can each contribute to the distinct characteristics of HIV infection observed in males versus females. One striking example of this is the tendency for women to have lower HIV plasma viral loads than their male counterparts early in infection, though both progress to AIDS at similar rates. Sex differences in acquisition of HIV, innate and adaptive anti-HIV immune responses, efficacy/suitability of specific antiretroviral drugs, and viral pathogenesis have all been identified. Sex differences also have the potential to affect viral persistence, latency, and cure approaches. In this brief review, we summarize the major biological male/female sex differences in HIV infection and their importance to viral acquisition, pathogenesis, treatment, and cure efforts.

Regulation of epitope exposure in the gp41 membrane-proximal external region through interactions at the apex of HIV-1 Env

Glycoprotein Env of human immunodeficiency virus type 1 (HIV-1) mediates viral entry through membrane fusion. Composed of gp120 and gp41 subunits arranged as a trimer-of-heterodimers, Env adopts a metastable, highly dynamic conformation on the virion surface. This structural plasticity limits the temporospatial exposure of many highly conserved, neutralizing epitopes, contributing to the difficulty in developing effective HIV-1 vaccines. Here, we employed antibody neutralization of HIV-1 infectivity to investigate how inter- and intra-gp120 interactions mediated by variable loops V1/V2 and V3 at the Env apex regulate accessibility of the gp41 membrane-proximal external region (MPER) at the Env base. Swapping the V3 loop from Env_SF162 into the Env_HXB2 background shifted MPER exposure from the prefusogenic state to a functional intermediate conformation that was distinct from the prehairpin-intermediate state sensitive to gp41-targeted fusion inhibitors. The V3-loop swap had a profound impact on global protein dynamics, biasing the equilibrium to a closed conformation resistant to most anti-gp120 antibodies, stabilizing the protein to both cold- and soluble CD4-induced Env inactivation, and increasing the CD4 requirements for viral entry. Further dissection of the Env_HXB2 V3 loop revealed that residue 306 uniquely modulated epitope exposure and trimer stability. The R306S substitution substantially decreased sensitivity to antibodies targeting the gp41 MPER and, surprisingly, the gp120 V3-loop crown (residues 312–315), but had only modest effects on exposure of intervening gp120 epitopes. Furthermore, the point mutation reduced soluble CD4-induced inactivation, but had no impact on cold inactivation. The residue appeared to exert its effects by electrostatically modifying the strength of intra-subunit interactions between the V1/V2 and V3 loops. The distinct patterns of neutralization and stability pointed to a novel prefusogenic Env conformation along the receptor activation pathway and suggested that apical Env-regulation of gp41 MPER exposure can be decoupled from much of the dynamics of gp120 subunits.

Surface glycoprotein Env is the main target for neutralizing antibodies elicited by HIV-1 vaccines. Env spontaneously fluctuates among different structures, limiting exposure of many attractive antibody-binding epitopes and, thereby, confounding vaccine development. To characterize these fluctuations, we examined how exposure of the MPER epitope found at the base of Env is regulated by interactions of the V3 loop located in the apex. Starting with an extremely flexible Env with a readily-exposed MPER, we identified two alterations that substantially restricted antibody access to the epitope. The first, a wholesale swap of V3 loops between HIV-1 strains, energetically stabilized Env in a closed structure that restricted access to antibodies throughout the protein. The second, a point mutation that altered V3-loop charge, specifically destabilized the MPER-exposed conformation but had minimal impact on antibody access to Env regions in between the apex and base. The results indicate that MPER exposure is not explicitly tied to the dynamics of Env regions between the apex and base and suggest a new structural fluctuation during Env activation.

Coreceptor Functions of Cell Surface Heparan Sulfate Proteoglycans

Receptor-ligand interactions play an important role in many biological processes by triggering specific cellular responses. These interactions are frequently regulated by coreceptors that facilitate, alter, or inhibit signaling. Coreceptors work in parallel with other specific and accessory molecules to coordinate receptor-ligand interactions. Cell surface heparan sulfate proteoglycans (HSPGs) function as unique coreceptors because they can bind to many ligands and receptors through their HS and core protein motifs. Cell surface HSPGs are typically expressed in abundance of the signaling receptors and, thus, are capable of mediating the initial binding of ligands to the cell surface. HSPG coreceptors do not possess kinase domains or intrinsic enzyme activities and, for the most part, binding to cell surface HSPGs does not directly stimulate intracellular signaling. Because of these features, cell surface HSPGs primarily function as coreceptors for many receptor-ligand interactions. Given that cell surface HSPGs are widely conserved, they likely serve fundamental functions to preserve basic physiological processes. Indeed, cell surface HSPGs can support specific cellular interactions with growth factors, morphogens, chemokines, extracellular matrix (ECM) components, and microbial pathogens and their secreted virulence factors. Through these interactions, HSPG coreceptors regulate cell adhesion, proliferation, migration and differentiation, and impact the onset, progression, and outcome of pathophysiological processes, such as development, tissue repair, inflammation, infection, and tumorigenesis. This review seeks to provide an overview of the various mechanisms of how cell surface HSPGs function as coreceptors.

Total synthesis of Icetexanes Diterpenoids: (±)-Rosmaridiphenol, (±)-Pisiferin, (±)-Barbatusol from Abitane

We report the rearrangement of abitane core 3 with trifluoromethanesulfonic anhydride in pyridine afforded the icetexane core 4, which was key intermediate for total synthesis of structurally intriguing and biologically active compounds (±)-barbatusol, (±)-rosmaridiphenol and (±)-pisiferin.