Viral interactions in human lymphoid tissue: Human herpesvirus 7 suppresses the replication of CCR5-tropic human immunodeficiency virus type 1 via CD4 modulation

Co-Infections and Superinfections between HIV-1 and Other Human Viruses at the Cellular Level

Co-infection or superinfection of the host by two or more virus species is a common event, potentially leading to viral interference, viral synergy, or neutral interaction. The simultaneous presence of two or more viruses, even distantly related, within the same cell depends upon viral tropism, i.e., the entry of viruses via receptors present on the same cell type. Subsequently, productive infection depends on the ability of these viruses to replicate efficiently in the same cellular environment. HIV-1 initially targets CCR5-expressing tissue memory CD4+ T cells, and in the absence of early cART initiation, a co-receptor switch may occur, leading to the infection of naïve and memory CXCR4-expressing CD4+ T cells. HIV-1 infection of macrophages at the G1 stage of their cell cycle also occurs in vivo, broadening the possible occurrence of co-infections between HIV-1 and other viruses at the cellular level. Moreover, HIV-1-infected DCs can transfer the virus to CD4+ T cells via trans-infection. This review focuses on the description of reported co-infections within the same cell between HIV-1 and other human pathogenic, non-pathogenic, or low-pathogenic viruses, including HIV-2, HTLV, HSV, HHV-6/-7, GBV-C, Dengue, and Ebola viruses, also discussing the possible reciprocal interactions in terms of virus replication and virus pseudotyping.

Activation-neutral gene editing of tonsillar CD4 T cells for functional studies in human ex vivo tonsil cultures

The molecular and immunological properties of tissue-resident resting CD4 T cells are understudied due to the lack of suitable gene editing methods. Here, we describe the ex vivo culture and gene editing methodology ediTONSIL for CD4 T cells from human tonsils. Optimized CRISPR-Cas9 RNP nucleofection results in knockout efficacies of over 90% without requiring exogenous activation. Editing can be performed on multiple cell types in bulk cultures or on isolated CD4 T cells that can be labeled and reintroduced into their tissue environment. Importantly, CD4 T cells maintain their tissue-specific properties such as viability, activation state, or immunocompetence following reassembly into lymphoid aggregates. This highly efficient and versatile gene editing workflow for tonsillar CD4 T cells enables the dissection of molecular mechanisms in ex vivo cultures of human lymphoid tissue and can be adapted to other tonsil-resident cell types.

Investigating the outcomes of virus coinfection within and across host species

Interactions between coinfecting pathogens have the potential to alter the course of infection and can act as a source of phenotypic variation in susceptibility between hosts. This phenotypic variation may influence the evolution of host-pathogen interactions within host species and interfere with patterns in the outcomes of infection across host species. Here, we examine experimental coinfections of two Cripaviruses-Cricket Paralysis Virus (CrPV), and Drosophila C Virus (DCV)-across a panel of 25 Drosophila melanogaster inbred lines and 47 Drosophilidae host species. We find that interactions between these viruses alter viral loads across D. melanogaster genotypes, with a ~3 fold increase in the viral load of DCV and a ~2.5 fold decrease in CrPV in coinfection compared to single infection, but we find little evidence of a host genetic basis for these effects. Across host species, we find no evidence of systematic changes in susceptibility during coinfection, with no interaction between DCV and CrPV detected in the majority of host species. These results suggest that phenotypic variation in coinfection interactions within host species can occur independently of natural host genetic variation in susceptibility, and that patterns of susceptibility across host species to single infections can be robust to the added complexity of coinfection.

New tools for immunologists: models of lymph node function from cells to tissues

The lymph node is a highly structured organ that mediates the body's adaptive immune response to antigens and other foreign particles. Central to its function is the distinct spatial assortment of lymphocytes and stromal cells, as well as chemokines that drive the signaling cascades which underpin immune responses. Investigations of lymph node biology were historically explored in vivo in animal models, using technologies that were breakthroughs in their time such as immunofluorescence with monoclonal antibodies, genetic reporters, in vivo two-photon imaging, and, more recently spatial biology techniques. However, new approaches are needed to enable tests of cell behavior and spatiotemporal dynamics under well controlled experimental perturbation, particularly for human immunity. This review presents a suite of technologies, comprising in vitro, ex vivo and in silico models, developed to study the lymph node or its components. We discuss the use of these tools to model cell behaviors in increasing order of complexity, from cell motility, to cell-cell interactions, to organ-level functions such as vaccination. Next, we identify current challenges regarding cell sourcing and culture, real time measurements of lymph node behavior in vivo and tool development for analysis and control of engineered cultures. Finally, we propose new research directions and offer our perspective on the future of this rapidly growing field. We anticipate that this review will be especially beneficial to immunologists looking to expand their toolkit for probing lymph node structure and function.

Infection of the Ex Vivo Tonsil Model by HTLV-1 Envelope-Pseudotyped Viruses

Human T-cell leukemia virus type 1 (HTLV-1) is the causal agent of adult T-cell leukemia/lymphoma and HTLV-1-associated myelopathy/tropical spastic paraparesis. Its tropism is known to be broad in cultured cell lines, while in vivo data support a more selective transmission toward CD4+ T cells and the limited targeting of other hematopoietic cell types. An essential condition for HTLV-1 infection is cell-to-cell contact, to which both virological synapse and viral biofilm have been suggested to strongly contribute. As cell lines and animal models each present their own limitations in studying HTLV-1 replication, we have explored the use of an ex vivo model based on the secondary lymphoid tonsillar tissue. HIV-1 luciferase-expressing pseudotyped viruses bearing the HTLV-1 envelope protein at their surface were first shown to recapitulate the wide spectrum of infectivity of HTLV-1 toward various cell lines. Tonsil fragments were next exposed to pseudotyped viruses and shown to be reproducibly infected. Infection by HTLV-1 Env-pseudotyped viruses was blocked by different anti-gp46 antibodies, unlike infection by HIV-1 virions. The dose-dependent infection revealed a gradual increase in luciferase activity, which was again sensitive to anti-gp46 antibodies. Overall, these results suggest that the ex vivo tonsil model represents a reliable alternative for studying HTLV-1 replication and potentially viral latency, as well as early clonal formation.

How Phagocytes Acquired the Capability of Hunting and Removing Pathogens From a Human Body: Lessons Learned From Chemotaxis and Phagocytosis of Dictyostelium discoideum (Review)

How phagocytes find invading microorganisms and eliminate pathogenic ones from human bodies is a fundamental question in the study of infectious diseases. About 2.5 billion years ago, eukaryotic unicellular organisms–protozoans–appeared and started to interact with various bacteria. Less than 1 billion years ago, multicellular animals–metazoans–appeared and acquired the ability to distinguish self from non-self and to remove harmful organisms from their bodies. Since then, animals have developed innate immunity in which specialized white-blood cells phagocytes- patrol the body to kill pathogenic bacteria. The social amoebae Dictyostelium discoideum are prototypical phagocytes that chase various bacteria via chemotaxis and consume them as food via phagocytosis. Studies of this genetically amendable organism have revealed evolutionarily conserved mechanisms underlying chemotaxis and phagocytosis and shed light on studies of phagocytes in mammals. In this review, we briefly summarize important studies that contribute to our current understanding of how phagocytes effectively find and kill pathogens via chemotaxis and phagocytosis.

Activation of Endogenous Retrovirus, Brain Infections and Environmental Insults in Neurodegeneration and Alzheimer's Disease

Chronic neurodegenerative diseases are complex, and their pathogenesis is uncertain. Alzheimer’s disease (AD) is a neurodegenerative brain alteration that is responsible for most dementia cases in the elderly. AD etiology is still uncertain; however, chronic neuroinflammation is a constant component of brain pathology. Infections have been associated with several neurological diseases and viruses of the Herpes family appear to be a probable cause of AD neurodegenerative alterations. Several different factors may contribute to the AD clinical progression. Exogeneous viruses or other microbes and environmental pollutants may directly induce neurodegeneration by activating brain inflammation. In this paper, we suggest that exogeneous brain insults may also activate retrotransposons and silent human endogenous retroviruses (HERVs). The initial inflammation of small brain areas induced by virus infections or other brain insults may activate HERV dis-regulation that contributes to neurodegenerative mechanisms. Chronic HERV activation in turn may cause progressive neurodegeneration that thereafter merges in cognitive impairment and dementia in genetically susceptible people. Specific treatment for exogenous end endogenous pathogens and decreasing pollutant exposure may show beneficial effect in early intervention protocol to prevent the progression of cognitive deterioration in the elderly.

L-lysine therapy to control the clinical evolution of pityriasis rosea: Clinical case report and literature review

Pityriasis rosea (PR) is a dermatological disease with an erythemato-papulosquamous manifestation, distributed on the trunk and extremities affecting healthy people, especially children and young people between 10 and 35 years of age. The evolution is 6 to 8 weeks and may remain for 3 to 6 months. It regresses spontaneously and can leave changes in the skin color but reversibly. Acyclovir is indicated to minimize clinical manifestations with the suspected of viral association (HHV-6 and 7). Another group of the human herpesvirus family (HHV-1 and 2), causes herpes simplex that is controlled with the antivirals, including acyclovir, as well as the amino acid L-lysine, both showing positive and similar results in reducing the number of annual manifestations and the healing time of the lesions. The aim of this study is to report a case of PR in a child, to review the literature on the etiopathogenesis of the disease and on the effects of L-lysine as well as another amino acid in the treatment. An 11-year-old girl, phototype II, presented lesions diagnosed as PR. The cycle would be 6 to 8 weeks on average. A solution of L-lysine was prescribed for 30 days, on an empty stomach. After the fourth day of therapy, the cycle of new eruptions was interrupted, initial lesions regressed, accelerating the repair of larger lesions resulting in an improvement of the clinical condition. We concluded that the administration of L-lysine, in therapeutic doses, can be a safe alternative for the PR control.

Dynamics and predisposition of respiratory viral co-infections in children and adults

OBJECTIVES

The epidemiology of respiratory co-infection pairings is poorly understood. Here we assess the dynamics of respiratory viral co-infections in children and adults and determine predisposition for or against specific viral pairings.

METHODS

Over five respiratory seasons from 30 November 2013 through 6 June 2018, the mono-infection and co-infection prevalence of 13 viral pathogens was tabulated at The Cleveland Clinic. Employing a model to proportionally distribute viral pairs using individual virus co-infection rate with prevalence patterns of concurrent co-circulating viruses, we compared predicted occurrence with observed occurrence of 132 viral pairing permutations using binomial analysis.

RESULTS

Of 30 535 respiratory samples, 9843 (32.2%) were positive for at least one virus and 1018 (10.8%) of these were co-infected. Co-infected samples predominantly originated from children. Co-infection rate in paediatric population was 35.0% (2068/5906), compared with only 5.8% (270/4591) in adults. Adenovirus C (ADVC) had the highest co-infection rate (426/623, 68.3%) while influenza virus B had the lowest (55/546, 10.0%). ADVC-rhinovirus (HRV), respiratory syncytial virus A (RSVA)-HRV and RSVB-HRV pairings occurred at significantly higher frequencies than predicted by the proportional distribution model (p < 0.05). Additionally, several viral pairings had fewer co-infections than predicted by our model: notably metapneumovirus (hMPV)-parainfluenza virus 3, hMPV-RSVA and RSVA-RSVB.

CONCLUSIONS

This is one of the largest studies on respiratory viral co-infections in children and adults. Co-infections are substantially more common in children, especially under 5 years of age, and the most frequent pairings occurred at a higher frequency than would be expected by random. Specific pairings occur at altered rates compared with those predicted by proportional distribution, suggesting either direct or indirect interactions result between specific viral pathogens.

DNA dependent protein kinase (DNA-PK) enhances HIV transcription by promoting RNA polymerase II activity and recruitment of transcription machinery at HIV LTR

Despite reductions in mortality from the use of highly active antiretroviral therapy (HAART), the presence of latent or transcriptionally silent proviruses prevents HIV cure/eradication. We have previously reported that DNA-dependent protein kinase (DNA-PK) facilitates HIV transcription by interacting with the RNA polymerase II (RNAP II) complex recruited at HIV LTR. In this study, using different cell lines and peripheral blood mononuclear cells (PBMCs) of HIV-infected patients, we found that DNA-PK stimulates HIV transcription at several stages, including initiation, pause-release and elongation. We are reporting for the first time that DNA-PK increases phosphorylation of RNAP II C-terminal domain (CTD) at serine 5 (Ser5) and serine 2 (Ser2) by directly catalyzing phosphorylation and by augmenting the recruitment of the positive transcription elongation factor (P-TEFb) at HIV LTR. Our findings suggest that DNA-PK expedites the establishment of euchromatin structure at HIV LTR. DNA-PK inhibition/knockdown leads to the severe impairment of HIV replication and reactivation of latent HIV provirus. DNA-PK promotes the recruitment of Tripartite motif-containing 28 (TRIM28) at LTR and assists the release of paused RNAP II through TRIM28 phosphorylation. These results provide the mechanisms through which DNA-PK controls the HIV gene expression and, likely, can be extended to cellular gene expression, including during cell malignancy, where the role of DNA-PK has been well-established.

Vaginal Lactobacillus Inhibits HIV-1 Replication in Human Tissues Ex Vivo

Lactobacillus species, which dominate vaginal microbiota of healthy reproductive-age women, lower the risks of sexually transmitted infections, including the risk of human immunodeficiency virus (HIV) acquisition. The exact mechanisms of this protection remain to be understood. Here, we investigated these mechanisms in the context of human cervico-vaginal and lymphoid tissues ex vivo. We found that all six Lactobacillus strains tested in these systems significantly suppressed HIV type-1 (HIV-1) infection. We identified at least three factors that mediated this suppression: (i) Acidification of the medium. The pH of the undiluted medium conditioned by lactobacilli was between 3.8 and 4.6. Acidification of the culture medium with hydrochloric acid (HCl) to this pH in control experiments was sufficient to abrogate HIV-1 replication. However, the pH of the Lactobacillus-conditioned medium (CM) diluted fivefold, which reached ∼6.9, was also suppressive for HIV-1 infection, while in control experiments HIV-1 infection was not abrogated when the pH of the medium was brought to 6.9 through the use of HCl. This suggested the existence of other factors responsible for HIV-1 inhibition by lactobacilli. (ii) Lactic acid. There was a correlation between the concentration of lactic acid in the Lactobacillus-CM and its ability to suppress HIV-1 infection in human tissues ex vivo. Addition of lactic acid isomers D and L to tissue culture medium at the concentration that corresponded to their amount released by lactobacilli resulted in HIV-1 inhibition. Isomer L was produced in higher quantities than isomer D and was mostly responsible for HIV-1 inhibition. These results indicate that lactic acid, in particular its L-isomer, inhibits HIV-1 independently of lowering of the pH. (iii) Virucidal effect. Incubation of HIV-1 in Lactobacillus-CM significantly suppressed viral infectivity for human tissues ex vivo. Finally, lactobacilli adsorb HIV-1, serving as a sink decreasing the number of free virions. In summary, we found that lactobacilli inhibit HIV-1 replication in human tissue ex vivo by multiple mechanisms. Further studies are needed to evaluate the potential of altering the spectra of vaginal microbiota as an effective strategy to enhance vaginal health. Human tissues ex vivo may serve as a test system for these strategies.

Multiple sclerosis: an example of pathogenic viral interaction?

A hypothesis is formulated on viral interaction between HHV-6A and EBV as a pathogenic mechanism in Multiple Sclerosis (MS). Evidence of molecular and genetic mechanisms suggests a link between HHV-6A infection and EBV activation in the brain of MS patients leading to intrathecal B-cell transformation. Consequent T-cell immune response against the EBV-infected cells is postulated as a pathogenic basis for inflammatory lesion formation in the brain of susceptible individuals. A further link between HHV-6A and EBV involves their induction of expression of the human endogenous retrovirus HERV-K18-encoded superantigen. Such virally induced T-cell responses might secondarily also lead to local autoimmune phenomena. Finally, research recommendations are formulated for substantiating the hypothesis on several levels: epidemiologically, genetically, and viral expression in the brain.

Prevention of Tumor Formation by Latent Gammaherpesvirus Infection

Recent reports suggested that chronic herpesvirus infection, as a constituent of the so-called virome, may not only exert harmful effects but may also be beneficial to the host, for example mediating increased resistance to secondary infections or to tumors. To further challenge this concept, specifically regarding increased resistance to tumors, we infected chimeric HLA-DR4-H2-E (DR4) mice, a mouse strain which spontaneously develops hematological tumors, with the rodent herpesvirus murine gammaherpesvirus 68 (MHV-68). Using this model, we observed that infection with wildtype MHV-68 completely prevented tumor formation. This happened, however, at the cost of hyposplenism. In contrast to wildtype infection, infection with a latency-deficient mutant of MHV-68 neither prevented tumor formation nor induced hyposplenism. The underlying mechanisms are not known but might be related to an infection-mediated priming of the immune response, resulting in the suppression of a tumor promoting endogenous retrovirus. Thus, under certain circumstances, chronic herpesvirus infection may prevent the development of tumors.

Signal peptide-binding drug as a selective inhibitor of co-translational protein translocation

In eukaryotic cells, surface expression of most type I transmembrane proteins requires translation and simultaneous insertion of the precursor protein into the endoplasmic reticulum (ER) membrane for subsequent routing to the cell surface. This co-translational translocation pathway is initiated when a hydrophobic N-terminal signal peptide (SP) on the nascent protein emerges from the ribosome, binds the cytosolic signal recognition particle (SRP), and targets the ribosome-nascent chain complex to the Sec61 translocon, a universally conserved protein-conducting channel in the ER-membrane. Despite their common function in Sec61 targeting and ER translocation, SPs have diverse but unique primary sequences. Thus, drugs that recognise SPs could be exploited to inhibit translocation of specific proteins into the ER. Here, through flow cytometric analysis the small-molecule macrocycle cyclotriazadisulfonamide (CADA) is identified as a highly selective human CD4 (hCD4) down-modulator. We show that CADA inhibits CD4 biogenesis and that this is due to its ability to inhibit co-translational translocation of CD4 into the lumen of the ER, both in cells as in a cell-free in vitro translation/translocation system. The activity of CADA maps to the cleavable N-terminal SP of hCD4. Moreover, through surface plasmon resonance analysis we were able to show direct binding of CADA to the SP of hCD4 and identify this SP as the target of our drug. Furthermore, CADA locks the SP in the translocon during a post-targeting step, possibly in a folded state, and prevents the translocation of the associated protein into the ER lumen. Instead, the precursor protein is routed to the cytosol for degradation. These findings demonstrate that a synthetic, cell-permeable small-molecule can be developed as a SP-binding drug to selectively inhibit protein translocation and to reversibly regulate the expression of specific target proteins.

Histocultures (tissue explants) in human retrovirology

Viral pathogenesis is studied predominantly in cultures of primary isolated cells or cell lines. Many retroviruses efficiently replicate only in activated cells. Therefore, in order to become efficient viral producers cells should be artificially activated, a procedure which significantly changes cell physiology. However, for many viral diseases, like HIV-1 and other retroviruses' diseases, critical pathogenic events occur in tissues. Therefore, cell isolation from their native microenvironment prevents single-cell cultures from faithfully reflecting important aspects of cell-cell and cell-pathogen interactions that occur in the context of complex tissue cytoarchitecture. Tissue explants (histocultures) that retain tissue cytoarchitecture and many aspects of cell-cell interactions more faithfully represent in vivo tissue features. Human histocultures constitute an adequate model for studying viral pathogenesis under controlled laboratory conditions. Protocols for various human histocultures as applied to study retroviral pathogenesis, in particular of HIV-1, have been refined by our laboratory and are described in the present publication. Histocultures of human tonsils and lymph nodes, as well as of recto-sigmoid and cervicovaginal tissues can be used to study viral transmission, pathogenesis and as a preclinical platform for antivirals evaluation.

Control of antiviral immunity by pattern recognition and the microbiome

Human skin and mucosal surfaces are in constant contact with resident and invasive microbes. Recognition of microbial products by receptors of the innate immune system triggers rapid innate defense and transduces signals necessary for initiating and maintaining the adaptive immune responses. Microbial sensing by innate pattern-recognition receptors is not restricted to pathogens. Rather, proper development, function, and maintenance of innate and adaptive immunity rely on continuous recognition of products derived from the microorganisms indigenous to the internal and external surfaces of mammalian host. Tonic immune activation by the resident microbiota governs host susceptibility to intestinal and extra-intestinal infections, including those caused by viruses. This review highlights recent developments in innate viral recognition leading to adaptive immunity, and discusses potential links between viruses, microbiota, and the host immune system. Furthermore, we discuss the possible roles of microbiome in chronic viral infection and pathogenesis of autoimmune disease and speculate on the benefit for probiotic therapies against such diseases.

Immune modulation during latent herpesvirus infection

Nearly all human beings, by the time they reach adolescence, are infected with multiple herpesviruses. At any given time, this family of viruses accounts for 35-40 billion human infections worldwide, making herpesviruses among the most prevalent pathogens known to exist. Compared to most other viruses, herpesviruses are also unique in that infection lasts the life of the host. Remarkably, despite their prevalence and persistence, little is known about how these viruses interact with their hosts, especially during the clinically asymptomatic phase of infection referred to as latency. This review explores data in human and animal systems that reveal the ability of latent herpesviruses to modulate the immune response to self and environmental antigens. From the perspective of the host, there are both potentially detrimental and surprisingly beneficial effects of this lifelong interaction. The realization that latent herpesvirus infection modulates immune responses in asymptomatic hosts forces us to reconsider what constitutes a 'normal' immune system in a healthy individual.

Improving potencies and properties of CD4 down-modulating CADA analogs

INTRODUCTION

CADA is a synthetic small molecule that inhibits HIV replication in cell cultures through down-modulating cell surface CD4 by inhibiting cotranslational translocation of nascent CD4 across the ER membrane in a signal sequence-specific manner. Analogs have been prepared mainly to increase potency and investigate the mechanism of action.

AREAS COVERED

This article reviews progress on discovery of more potent CADA analogs, including symmetrical and unsymmetrical compounds, as well as fluorescent derivatives. The article also discusses some properties of CADA and a more potent analog (KKD023) that are relevant to drug development, including aqueous solubility, permeability, metabolism and oral bioavailability.

EXPERT OPINION

Further studies on CADA analogs should focus on improving both potency and drug-like properties, and on elucidating the detailed mechanism of action. Solubility and permeability may be improved by reducing molecular weight, decreasing molecular flexibility and symmetry, or by a prodrug approach inducing active transport. Identifying the molecular mechanism of CD4 down-modulation may aid in assessing potential side effects of such immunomodulatory/anti-HIV drugs, and it could potentially lead to a general approach to designing drugs for specifically down-modulating other cell-surface proteins.

Replication of Epstein-Barr virus primary infection in human tonsil tissue explants

Epstein-Barr virus (EBV) may cause a variety of virus-associated diseases, but no antiviral agents have yet been developed against this virus. Animal models are thus indispensable for the pathological analysis of EBV-related infections and the elucidation of therapeutic methods. To establish a model system for the study of EBV infection, we tested the ability of B95–8 virus and recombinant EBV expressing enhanced green fluorescent protein (EGFP) to replicate in human lymphoid tissue. Human tonsil tissues that had been surgically removed during routine tonsillectomy were sectioned into small blocks and placed on top of collagen sponge gels in culture medium at the air-interface, then a cell-free viral suspension was directly applied to the top of each tissue block. Increasing levels of EBV DNA in culture medium were observed after 12–15 days through 24 days post-infection in tissue models infected with B95–8 and EGFP-EBV. Expression levels of eight EBV-associated genes in cells collected from culture medium were increased during culture. EBV-encoded small RNA-positive cells were detected in the interfollicular areas in paraffin-embedded sections. Flow cytometric analyses revealed that most EGFP⁺ cells were CD3⁻ CD56⁻ CD19⁺ HLA-DR⁺, and represented both naïve (immunoglobulin D⁺) and memory (CD27⁺) B cells. Moreover, EBV replication in this model was suppressed by acyclovir treatment in a dose-dependent manner. These data suggest that this model has potential for use in the pathological analysis of local tissues at the time of primary infection, as well as for screening novel antiviral agents.

Unsymmetrical cyclotriazadisulfonamide (CADA) compounds as human CD4 receptor down-modulating agents

Cyclotriazadisulfonamide (CADA) inhibits HIV at submicromolar levels by specifically down-modulating cell-surface and intracellular CD4. The specific biomolecular target of CADA compounds is unknown, but previous studies led to an unsymmetrical binding model. To test this model, methods were developed for effective synthesis of diverse, unsymmetrical CADA compounds. A total of 13 new, unsymmetrical target compounds were synthesized, as well as one symmetrical analogue. The new compounds display a wide range of potency for CD4 down-modulation in CHO·CD4-YFP cells. VGD020 (IC(50) = 46 nM) is the most potent CADA compound discovered to date, and VGD029 (IC(50) = 730 nM) is the most potent fluorescent analogue. Structure-activity relationships are analyzed from the standpoint of additive or nonadditive energy effects of different substituents. They appear to be consistent with the zipper-type mechanism in which entropy costs are reduced for additional stabilizing interactions between the small molecule and its protein target.

Cervico-vaginal tissue ex vivo as a model to study early events in HIV-1 infection

Vaginal intercourse remains the most prevalent route of infection of women. In spite of many efforts, the detailed mechanisms of HIV-1 transmission in the female lower genital tract remain largely unknown. With all the obvious restrictions on studying these mechanisms in humans, their understanding depends on the development of adequate experimental models. Isolated cell cultures do not faithfully reproduce important aspects of cell-cell interactions in living tissues and tissue responses to pathogens. Explants and other types of ex vivo tissue models serve as a bridge between cell culture and tissues in vivo. Herein, we discuss various cervico-vaginal tissue models and their use in studying HIV vaginal transmission and consider future directions of such studies.

Contrasting roles for TLR ligands in HIV-1 pathogenesis

The first line of a host's response to various pathogens is triggered by their engagement of cellular pattern recognition receptors (PRRs). Binding of microbial ligands to these receptors leads to the induction of a variety of cellular factors that alter intracellular and extracellular environment and interfere directly or indirectly with the life cycle of the triggering pathogen. Such changes may also affect any coinfecting microbe. Using ligands to Toll-like receptors (TLRs) 5 and 9, we examined their effect on human immunodeficiency virus (HIV)-1 replication in lymphoid tissue ex vivo. We found marked differences in the outcomes of such treatment. While flagellin (TLR5 agonist) treatment enhanced replication of CC chemokine receptor 5 (CCR 5)-tropic and CXC chemokine receptor 4 (CXCR4)-tropic HIV-1, treatment with oligodeoxynucleotide (ODN) M362 (TLR9 agonist) suppressed both viral variants. The differential effects of these TLR ligands on HIV-1 replication correlated with changes in production of CC chemokines CCL3, CCL4, CCL5, and of CXC chemokines CXCL10, and CXCL12 in the ligand-treated HIV-1-infected tissues. The nature and/or magnitude of these changes were dependent on the ligand as well as on the HIV-1 viral strain. Moreover, the tested ligands differed in their ability to induce cellular activation as evaluated by the expression of the cluster of differentiation markers (CD) 25, CD38, CD39, CD69, CD154, and human leukocyte antigen D related (HLA)-DR as well as of a cell proliferation marker, Ki67, and of CCR5. No significant effect of the ligand treatment was observed on apoptosis and cell death/loss in the treated lymphoid tissue ex vivo. Our results suggest that binding of microbial ligands to TLRs is one of the mechanisms that mediate interactions between coinfected microbes and HIV-1 in human tissues. Thus, the engagement of appropriate TLRs by microbial molecules or their mimetic might become a new strategy for HIV therapy or prevention.

War and peace between microbes: HIV-1 interactions with coinfecting viruses

HIV-1 disrupts the homeostatic equilibrium between the host and coinfecting microbes, facilitating reactivation of persistent viruses and invasion by new viruses. These viruses usually accelerate HIV disease but occasionally create conditions detrimental for HIV-1. Understanding these phenomena may lead to anti-HIV-1 strategies that specifically target interactions between HIV-1 and coinfecting viruses.

Significantly reduced CCR5-tropic HIV-1 replication in vitro in cells from subjects previously immunized with Vaccinia Virus

Background

At present, the relatively sudden appearance and explosive spread of HIV throughout Africa and around the world beginning in the 1950s has never been adequately explained. Theorizing that this phenomenon may be somehow related to the eradication of smallpox followed by the cessation of vaccinia immunization, we undertook a comparison of HIV-1 susceptibility in the peripheral blood mononuclear cells from subjects immunized with the vaccinia virus to those from vaccinia naive donors.

Results

Vaccinia immunization in the preceding 3-6 months resulted in an up to 5-fold reduction in CCR5-tropic but not in CXCR4-tropic HIV-1 replication in the cells from vaccinated subjects. The addition of autologous serum to the cell cultures resulted in enhanced R5 HIV-1 replication in the cells from unvaccinated, but not vaccinated subjects. There were no significant differences in the concentrations of MIP-1α, MIP-1β and RANTES between the cell cultures derived from vaccinated and unvaccinated subjects when measured in culture medium on days 2 and 5 following R5 HIV-1 challenge.

Discussion

Since primary HIV-1 infections are caused almost exclusively by the CCR5-tropic HIV-1 strains, our results suggest that prior immunization with vaccinia virus might provide an individual with some degree of protection to subsequent HIV infection and/or progression. The duration of such protection remains to be determined. A differential elaboration of MIP-1α, MIP-1β and RANTES between vaccinated and unvaccinated subjects, following infection, does not appear to be a mechanism in the noted protection.

Human herpesvirus 7

Az emberi 7-es herpeszvírus 1990 óta ismert, közeli rokonságban áll a 6-os herpeszvírussal, annak B változatával. Csak emberi sejtekben szaporodik, receptora a CD4 molekula. A fertőzött sejtek egy részében élethossziglan lappang, gyakran reaktiválódik és a nyálban tünetmentesen ürül. Gyermekek egy része 3–4 éves korára tünetmentesen fertőződik, de minden életkorban találhatók szeronegatív egyének, akik fogékonyak a fertőzés iránt. Gyermekekben ritkán exanthema subitum, múló lázas-görcsös állapotok, fiatal felnőttekben rózsahámlás, immunszuppresszált egyénekben a reaktiválódott 6-os B herpeszvírussal és cytomegalovirussal egyetemben halálos szövődmények alakulhatnak ki. Egyéb vírusokat is aktiválhat más kórképekben. A vírus patogenezisében a legfontosabb, hogy megváltozik a fertőzött lymphocytákból kiáramló citokinek és növekedési faktorok egyensúlya, amely láncreakcióként hat az immunrendszer és egyéb szervek sejtjeire. A vírusellenes antitestek kimutatása kereskedelmi forgalomban kapható készletekkel (immunfluoreszcencia, ELISA, immunoblot), a nukleinsav kimutatása fészkes polimeráz láncreakcióval lehetséges. A fertőzés következtében kialakult betegségek legtöbbje nem igényel kezelést, de súlyos szövődmények esetén ganciclovir és származékai, valamint foscarnet és cidofovir alkalmazható.

Macrophage involvement in Epstein-Barr virus-related tumors

Epstein-Barr virus (EBV) is known as a causative agent of Burkitt's lymphoma, nasopharyngeal carcinoma and approximately 10% of stomach carcinoma cases. In other human cancers, EBV gene expression including lytic infection protein detected using in situ hybridization and immunofluorescence staining has been reported. Moreover, the expression and replication of EBV genes in cultured normal macrophages and in histiocytes of Langerhans' cell histiocytosis have been identified. The aim of this study was to examine EBV expression in macrophages in other EBV-associated human tumors. Forty-one cases of EBV-associated tumors, which had been confirmed to express EBV, were examined. Tissue sections after in situ hybridization were double-stained immunohistochemically with the monoclonal anti-CD68 antibody. EBV expression in macrophages in the lesions of nasopharyngeal carcinoma, oral cancer, thyroid carcinoma, renal cell carcinoma, testicular carcinoma, uterine carcinoma, cutaneous T-cell lymphoma and anaplastic large-cell lymphoma was identified, whereas macrophages in normal or non-cancerous lesions showed no EBV expression. Many tumor-associated macrophages in EBV-related tumors carry EBV, which appears to induce the EBV lytic infection of macrophages. Therefore, the possibility that the lytic infection of macrophages by EBV and the resulting inflammation play certain roles in the oncogenesis of EBV-associated human tumors was raised.

Viruses within the Flaviviridae decrease CD4 expression and inhibit HIV replication in human CD4+ cells

Viral infections alter host cell homeostasis and this may lead to immune evasion and/or interfere with the replication of other microbes in coinfected hosts. Two flaviviruses are associated with a reduction in HIV replication or improved survival in HIV-infected people (dengue virus (DV) and GB virus type C (GBV-C)). GBV-C infection and expression of the GBV-C nonstructural protein 5A (NS5A) and the DV NS5 protein in CD4(+) T cells inhibit HIV replication in vitro. To determine whether the inhibitory effect on HIV replication is conserved among other flaviviruses and to characterize mechanism(s) of HIV inhibition, the NS5 proteins of GBV-C, DV, hepatitis C virus, West Nile virus, and yellow fever virus (YFV; vaccine strain 17D) were expressed in CD4(+) T cells. All NS5 proteins inhibited HIV replication. This correlated with decreased steady-state CD4 mRNA levels and reduced cell surface CD4 protein expression. Infection of CD4(+) T cells and macrophages with YFV (17D vaccine strain) also inhibited HIV replication and decreased CD4 gene expression. In contrast, mumps virus was not inhibited by the expression of flavivirus NS5 protein or by YFV infection, and mumps infection did not alter CD4 mRNA or protein levels. In summary, CD4 gene expression is decreased by all human flavivirus NS5 proteins studied. CD4 regulation by flaviviruses may interfere with innate and adaptive immunity and contribute to in vitro HIV replication inhibition. Characterization of the mechanisms by which flaviviruses regulate CD4 expression may lead to novel therapeutic strategies for HIV and immunological diseases.

A systematic approach to virus-virus interactions

A virus–virus interaction is a measurable difference in the course of infection of one virus as a result of a concurrent or prior infection by a different species or strain of virus. Many such interactions have been discovered by chance, yet they have rarely been studied systematically. Increasing evidence suggests that virus–virus interactions are common and may be critical to understanding viral pathogenesis in natural hosts. In this review we propose a system for classifying virus–virus interactions by organizing them into three main categories: (1) direct interactions of viral genes or gene products, (2) indirect interactions that result from alterations in the host environment, and (3) immunological interactions. We have so far identified 15 subtypes of interaction and assigned each to one of these categories. It is anticipated that this framework will provide for a more systematic approach to investigating virus–virus interactions, both at the cellular and organismal levels.

Toxoplasma gondii inhibits R5 HIV-1 replication in human lymphoid tissues ex vivo

Critical events of HIV-1 pathogenesis occur in lymphoid tissues where HIV-1 is typically accompanied by infections with other pathogens (HIV co-pathogens). Co-pathogens greatly affect the clinical course of the disease and the transmission of HIV. The apicomplexan parasite Toxoplasma gondii is a common HIV co-pathogen associated with AIDS development. Here, we examined the interaction of T. gondii and HIV in coinfected human lymphoid tissue ex vivo. Both pathogens readily replicate in ex vivo infected blocks of human tonsillar tissue. Surprisingly, we found that live T. gondii preferentially inhibits R5 HIV-1 replication in coinfected tissues. This effect is reproduced by treatment of the tissue blocks with recombinant C-18, a T. gondii-encoded cyclophilin that binds to CCR5. These ex vivo findings raise the possibility that, in addition to being a co-factor in HIV disease, T. gondii may influence the outcome of viral infection by preferentially suppressing R5 variants.

Redefining chronic viral infection

Viruses that cause chronic infection constitute a stable but little-recognized part of our metagenome: our virome. Ongoing immune responses hold these chronic viruses at bay while avoiding immunopathologic damage to persistently infected tissues. The immunologic imprint generated by these responses to our virome defines the normal immune system. The resulting dynamic but metastable equilibrium between the virome and the host can be dangerous, benign, or even symbiotic. These concepts require that we reformulate how we assign etiologies for diseases, especially those with a chronic inflammatory component, as well as how we design and interpret genome-wide association studies, and how we vaccinate to limit or control our virome.

Interactions between viral and prokaryotic pathogens in a mixed infection with cardiovirus and mycoplasma

In the natural environment, animal and plant viruses often share ecological niches with microorganisms, but the interactions between these pathogens, although potentially having important implications, are poorly investigated. The present report demonstrates, in a model system, profound mutual effects of mycoplasma and cardioviruses in animal cell cultures. In contrast to mycoplasma-free cells, cultures contaminated with Mycoplasma hyorhinis responded to infection with encephalomyocarditis virus (EMCV), a picornavirus, but not with poliovirus (also a picornavirus), with a strong activation of a DNase(s), as evidenced by the TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) immunofluorescence assay and electrophoretic analysis of host DNA. This degradation was reminiscent of that observed upon apoptosis but was caspase independent, judging by the failure of the specific pan-caspase inhibitor Q-VD-OPh to prevent it. The electrophoretic mobility of the enzyme responsible for DNA degradation and dependence of its activity on ionic conditions strongly suggested that it was represented by a DNase(s) of mycoplasma origin. In cells not infected with EMCV, the relevant DNase was dormant. The possibility is discussed that activation of the mycoplasma DNase might be linked to a relatively early increase in permeability of plasma membrane of the infected cells caused by EMCV. This type of unanticipated virus-mycoplasma "cooperation" may exemplify the complexity of pathogen-host interactions under conditions when viruses and microorganisms are infecting the same host. In the course of the present study, it was also demonstrated that pan-caspase inhibitor zVAD(OMe).fmk strongly suppressed cardiovirus polyprotein processing, illustrating an additional pitfall in investigations of viral effects on the apoptotic system of host cells.

Use of human tissue explants to study human infectious agents

The study of human cell-cell and cell-pathogen interactions that occur in the context of complex tissue cytoarchitecture is critical for deciphering the mechanisms of many normal and pathogenic processes. This protocol describes methods for culturing and infecting explants of human tissues to study the pathogenesis of human infectious agents and their local interactions. The protocol relies on the use of fresh human tissues dissected into small blocks or biopsies that are cultured at the liquid-air interface on collagen rafts. These tissue blocks retain their cytoarchitecture and support productive infection of various pathogens without exogenous stimulation. Experimental details for setting up cultures of human tonsils, lymph nodes and cervicovaginal and rectosigmoid tissues, including protocols for their infection with HIV-1 and other pathogens, are described here. Using this protocol, culture and infections can be set up in 3-6 h and be maintained for 2-3 weeks, depending on the tissue used.

Coinfecting viruses as determinants of HIV disease

The human body constitutes a balanced ecosystem of its own cells together with various microbes ("host-microbe ecosystem"). The transmission of HIV-1 and the progression of HIV disease in such an ecosystem are accompanied by de novo infection by other microbes or by activation of microbes that were present in the host in homeostatic equilibrium before HIV-1 infection. In recent years, data have accumulated on the interactions of these coinfecting microbes-viruses in particular-with HIV. Coinfecting viruses generate negative and positive signals that suppress or upregulate HIV-1. We suggest that the signals generated by these viruses may largely affect HIV transmission, pathogenesis, and evolution. The study of the mechanisms of HIV interaction with coinfecting viruses may indicate strategies to suppress positive signals, enhance negative signals, and lead to the development of new and original anti-HIV therapies.

Identification of respiratory viruses in asymptomatic subjects: asymptomatic respiratory viral infections

The medical literature of the past 4 decades was searched regarding respiratory virus detection by polymerase chain reaction and conventional methods (culture, antigen detection, serology) in asymptomatic subjects in an attempt to determine the prevalence and clinical significance of such viruses in normal persons.

Characterization of a peptide domain within the GB virus C NS5A phosphoprotein that inhibits HIV replication

Background

GBV-C infection is associated with prolonged survival in HIV-infected people and GBV-C inhibits HIV replication in co-infection models. Expression of the GBV-C nonstructural phosphoprotein 5A (NS5A) decreases surface levels of the HIV co-receptor CXCR4, induces the release of SDF-1 and inhibits HIV replication in Jurkat CD4+ T cell lines.

Methodology/Principal Findings

Jurkat cell lines stably expressing NS5A protein and peptides were generated and HIV replication in these cell lines assessed. HIV replication was significantly inhibited in all cell lines expressing NS5A amino acids 152–165. Substitution of an either alanine or glycine for the serine at position 158 (S158A or S158G) resulted in a significant decrease in the HIV inhibitory effect. In contrast, substituting a phosphomimetic amino acid (glutamic acid; S158E) inhibited HIV as well as the parent peptide. HIV inhibition was associated with lower levels of surface expression of the HIV co-receptor CXCR4 and increased release of the CXCR4 ligand, SDF-1 compared to control cells. Incubation of CD4+ T cell lines with synthetic peptides containing amino acids 152–167 or the S158E mutant peptide prior to HIV infection resulted in HIV replication inhibition compared to control peptides.

Conclusions/Significance

Expression of GBV-C NS5A amino acids 152–165 are sufficient to inhibit HIV replication in vitro, and the serine at position 158 appears important for this effect through either phosphorylation or structural changes in this peptide. The addition of synthetic peptides containing 152–167 or the S158E substitution to Jurkat cells resulted in HIV replication inhibition in vitro. These data suggest that GBV-C peptides or a peptide mimetic may offer a novel, cellular-based approach to antiretroviral therapy.

Opportunistic pathogens in AIDS: trends, diagnosis and priorities

The second International Conference on Opportunistic Pathogens in AIDS was organized by the Department of Laboratory Medicine, All India Institute of Medical Sciences (New Delhi, India). The conference was held at the All India Institute of Medical Sciences in India between the 27th and 29th January 2008, and was attended by 225 participants representing 21 countries. The conference focused on trends, diagnosis and management of coinfections among HIV patients. In addition, as part of this conference, a symposium was held on the links between substance abuse, HIV and neuropathology.

Upregulation of human cytomegalovirus by HIV type 1 in human lymphoid tissue ex vivo

HIV-1 copathogens are believed to play a critical role in progression to AIDS. Human cytomegalovirus (HCMV) has a high prevalence in the general population and is a common copathogen in HIV-1-infected individuals. Important events in copathogen interactions with HIV-1 take place in lymphoid tissue where critical events in HIV-1 disease occur. Here, we used an experimental system of human lymphoid tissue ex vivo to investigate interactions of HCMV with HIV-1. We inoculated ex vivo blocks of human lymphoid tissue with a recombinant strain of HCMV, expressing the green fluorescent protein, and HIV-1 and monitored viral replication and the phenotype of productively infected cells. HCMV readily replicated in tissue blocks as revealed by the release of HCMV viral DNA and an increasing number of viral-positive cells. Immunophenotyping of HCMV-infected cells showed a preferential infection of activated lymphocytes. The number of these cells significantly increased in HIV-1-coinfected tissues. Accordingly, HCMV replication was enhanced 2- to-3 fold. This upregulation occurred in tissues infected with either CXCR4- or CCR5-utilizing HIV-1. Thus, HIV-1 creates new targets for HCMV, which may explain the strong association of HCMV with HIV-1 infection in vivo. Ex vivo-infected human lymphoid tissue constitutes a model to study the mechanisms of HCMV tissue pathogenesis and its interactions with HIV-1 and this model may provide new targets for anti-HIV-1 therapy.

Interactions between human immunodeficiency virus type 1 and vaccinia virus in human lymphoid tissue ex vivo

Vaccinia virus (VACV) has been attracting attention recently not only as a vector for various vaccines but also as an immunization tool against smallpox because of its potential use as a bioterrorism agent. It has become evident that in spite of a long history of studies of VACV, its tissue pathogenesis remains to be fully understood. Here, we investigated the pathogenesis of VACV and its interactions with human immunodeficiency virus type 1 (HIV-1) in the context of human lymphoid tissues. We found that ex vivo-cultured tonsillar tissue supports productive infection by the New York City Board of Health strain, the VACV strain of the Dryvax vaccine. VACV readily infected both T and non-T (B) lymphocytes and depleted cells of both of these subsets equally over a 12-day period postinfection. Among T lymphocytes, CD8(+) cells are preferentially depleted in accordance with their preferential infection: the probability that a CD8(+) T cell will be productively infected is almost six times higher than for a CD4(+) T cell. T cells expressing CCR5 and the activation markers CD25, CD38, and HLA-DR are other major targets for infection by VACV in lymphoid tissue. As a consequence, VACV predominantly inhibits the replication of the R5(SF162) phenotype of HIV-1 in coinfected tissues, as R5-tropic HIV-1 requires activated CCR5(+) CD4(+) cells for productive infection. Human lymphoid tissue infected ex vivo by VACV can be used to investigate interactions of VACV with other viruses, in particular HIV-1, and to evaluate various VACV vectors for the purpose of recombinant vaccine development.

Host factors influencing susceptibility to HIV infection and AIDS progression

Transmission of HIV first results in an acute infection, followed by an apparently asymptomatic period that averages ten years. In the absence of antiretroviral treatment, most patients progress into a generalized immune dysfunction that culminates in death. The length of the asymptomatic period varies, and in rare cases infected individuals never progress to AIDS. Other individuals whose behavioral traits put them at high-risk of HIV transmission, surprisingly appear resistant and never succumb to infection. These unique cases highlight the fact that susceptibility to HIV infection and progression to disease are complex traits modulated by environmental and genetic factors. Recent evidence has indicated that natural variations in host genes can influence the outcome of HIV infection and its transmission. In this review we summarize the available literature on the roles of cellular factors and their genetic variation in modulating HIV infection and disease progression.

Design and cellular kinetics of dansyl-labeled CADA derivatives with anti-HIV and CD4 receptor down-modulating activity

A new class of anti-retrovirals, cyclotriazadisulfonamide (CADA) and its derivatives, specifically down-regulate CD4, the main receptor of HIV, and prevent HIV infection in vitro. In this work, several CADA derivatives, chemically labeled with a fluorescent dansyl group, were evaluated for their biological features and cellular uptake kinetics. We identified a derivative KKD-016 with antiviral and CD4 down-modulating capabilities similar to those of the parental compound CADA. By using flow cytometry, we demonstrated that the dose-dependent cellular uptake of this derivative correlated with CD4 down-modulation. The uptake and activity of the dansyl-labeled compounds were not dependent on the level of expression of CD4 at the cell surface. Removal of the CADA compounds from the cell culture medium resulted in their release from the cells followed by a complete restoration of CD4 expression. The inability of several fluorescent CADA derivatives to down-modulate CD4 was not associated with their lower cellular uptake and was not reversed by facilitating their cell penetration by a surfactant. These results prove the successful integration of the dansyl fluorophore into the chemical structure of a CD4 down-modulating anti-HIV compound, and show the feasibility of tracking a receptor and its down-modulator simultaneously. These fluorescent CADA analogs with reversible CD4 down-regulating potency can now be applied in further studies on receptor modulation, and in the exploration of their potentials as preventive and therapeutic anti-HIV drugs.