Suppression of CCR5- but not CXCR4-tropic HIV-1 in lymphoid tissue by human herpesvirus 6

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.

Virus-Induced Cell Fusion and Syncytia Formation

Most enveloped viruses encode viral fusion proteins to penetrate host cell by membrane fusion. Interestingly, many enveloped viruses can also use viral fusion proteins to induce cell-cell fusion, both in vitro and in vivo, leading to the formation of syncytia or multinucleated giant cells (MGCs). In addition, some non-enveloped viruses encode specialized viral proteins that induce cell-cell fusion to facilitate viral spread. Overall, viruses that can induce cell-cell fusion are nearly ubiquitous in mammals. Virus cell-to-cell spread by inducing cell-cell fusion may overcome entry and post-entry blocks in target cells and allow evasion of neutralizing antibodies. However, molecular mechanisms of virus-induced cell-cell fusion remain largely unknown. Here, I summarize the current understanding of virus-induced cell fusion and syncytia formation.

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.

Metagenomic Analysis of the Respiratory Microbiome of a Broiler Flock from Hatching to Processing

Elucidating the complex microbial interactions in biological environments requires the identification and characterization of not only the bacterial component but also the eukaryotic viruses, bacteriophage, and fungi. In a proof of concept experiment, next generation sequencing approaches, accompanied by the development of novel computational and bioinformatics tools, were utilized to examine the evolution of the microbial ecology of the avian trachea during the growth of a healthy commercial broiler flock. The flock was sampled weekly, beginning at placement and concluding at 49 days, the day before processing. Metagenomic sequencing of DNA and RNA was utilized to examine the bacteria, virus, bacteriophage, and fungal components during flock growth. The utility of using a metagenomic approach to study the avian respiratory virome was confirmed by detecting the dysbiosis in the avian respiratory virome of broiler chickens diagnosed with infection with infectious laryngotracheitis virus. This study provides the first comprehensive analysis of the ecology of the avian respiratory microbiome and demonstrates the feasibility for the use of this approach in future investigations of avian respiratory diseases.

The role of human herpesvirus-6 and inflammatory markers in the pathogenesis of multiple sclerosis

Multiple sclerosis (MS) is a destructive autoimmune neuroinflammatory and neurodegenerative disorder of the central nervous system (CNS) with unknown etiology and mechanism of pathogenesis. Pathogens, especially human herpes viruses, have been suggested as environmental factors of the MS and other neuroinflammatory disorders. This study aimed to determine the prevalence of HHV-6 antibody response in MS patients and investigate the levels of pro/anti-inflammatory cytokine and chemokines in MS patients in comparison with healthy subjects. Two hundred sixty-three patients with clinically defined MS (140 females and 123 males), along with 263 healthy subjects (140 females and 123 males), were recruited for this study. After the analysis of HHV-6 seropositivity/seronegativity, the levels of some pro/anti-inflammatory cytokines, including TNF-α, IFN-γ, IL-1β, IL-6, and IL-12 as well as two chemokines, namely CCL-2 and CCL-5 were determined by the enzyme-linked immunosorbent assay (ELISA) method in HHV-6 seropositive/seronegative MS patients and healthy subjects. Our results showed that the serum concentrations of TNF-α, IFN-γ, IL-1β, IL-6, and CCL-5 elevated in HHV-6 seropositive compared with seronegative MS patients (P < .05). Moreover, the levels of IL-12, IL-10, and CCL-2 levels were significantly lower in seropositive MS patients when compared with seronegative MS patients (P < .05). Also, our results revealed that the mean values of the expanded disability status scale (EDSS) were significantly higher in HHV-6 seropositive versus seronegative MS patients (P < .05). In conclusion, we proposed that HHV-6 infection may play a role in MS pathogenesis by changing cytokine signaling in MS patients that may lead to peripheral inflammation.

Prevalence of human herpesviruses in biliary fluid and their association with biliary complications after liver transplantation

Background

Beta-herpesviruses are common opportunistic pathogens that cause morbidity after liver transplantation (LT).

Methods

Objective of the study was to evaluate the prevalence and correlation of herpesviruses in bile, blood and liver tissue and to investigate their association with biliary complications and retransplantation (re-LT) free survival after LT.

The study design is a single-center case-control study. We performed quantative polymerase chain reaction (qPCR) for herpesvirus 1–8 DNA in bile, blood and liver tissue of 73 patients after first LT and analyzed their clinical courses retrospectively.

Results

The median follow-up was 48 months (range 2–102), during which a total of 16 patients underwent re-LT and 11 patients died. Of the patients, 46.5% received valganciclovir prophylaxis at the time of bile sample acquisition. Cytomegalovirus (CMV) (18.3%), human herpesvirus 6 (HHV-6) (34.2%), human herpesvirus 7 (HHV-7) (20.5%) and Epstein-Barr virus (EBV) (16.4%) were highly prevalent in bile after LT, while herpes simpex virus 1 and 2 (HSV-1, HSV-2), varicella-zoster virus (VZV) and human herpesvirus 8 (HHV-8) were not or rarely detected in bile. Valganciclovir prophylaxis did not reduce the prevalence of HHV-6 and HHV-7 in bile, but it did reduce the presence of CMV and EBV. The presence of HHV-6 in bile was associated with non-anastomotic biliary strictures (NAS) and acute cellular rejection (ACR).

Conclusions

CMV, EBV, HHV-6 and HHV-7 are more prevalent in biliary fluid than in liver biopsy or blood serum after LT. HHV-6 and HHV-7 might be associated with biliary complications after LT. Biliary fluids might be an attractive target for routine herpesvirus detection.

Ex Vivo Infection of Human Lymphoid Tissue and Female Genital Mucosa with Human Immunodeficiency Virus 1 and Histoculture

Histocultures allow studying intercellular interactions within human tissues, and they can be employed to model host-pathogen interactions under controlled laboratory conditions. Ex vivo infection of human tissues with human immunodeficiency virus (HIV), among other viruses, has been successfully used to investigate early disease pathogenesis, as well as a platform to test the efficacy and toxicity of antiviral drugs. In the present protocol, we explain how to process and infect with HIV-1 tissue explants from human tonsils and cervical mucosae, and maintain them in culture on top of gelatin sponges at the liquid-air interface for about two weeks. This non-polarized culture setting maximizes access to nutrients in culture medium and oxygen, although progressive loss of tissue integrity and functional architectures remains its main limitation. This method allows monitoring HIV-1 replication and pathogenesis using several techniques, including immunoassays, qPCR, and flow cytometry. Of importance, the physiologic variability between tissue donors, as well as between explants from different areas of the same specimen, may significantly affect experimental results. To ensure result reproducibility, it is critical to use an adequate number of explants, technical replicates, and donor-matched control conditions to normalize the results of the experimental treatments when compiling data from multiple experiments (i.e., conducted using tissue from different donors) for statistical analysis.

Herpesviruses: Harmonious Pathogens but Relevant Cofactors in Other Diseases?

Most vertebrates are infected with one or more herpesviruses and remain so for the rest of their lives. The relationship of immunocompetent healthy host with herpesviruses may sometime be considered as harmonious. However, clinically severe diseases can occur when host immunity is compromised due to aging, during some stress response, co-infections or during neoplastic disease conditions. Discord can also occur during iatrogenic immunosuppression used for controlling graft rejection, in some primary genetic immunodeficiencies as well as when the virus infects a non-native host. In this review, we discuss such issues and their influence on host-herpesvirus interaction.

The Interplay between Natural Killer Cells and Human Herpesvirus-6

Human Herpesvirus 6 (HHV-6) is a set of two closely related herpes viruses known as HHV-6A and HHV-6B. Both are lymphotropic viruses that establish latency in the host. The ability to evade the immune responses of effector cells is likely a major factor contributing to the development of a persistent HHV-6A/B (collectively termed HHV-6) infection. Natural killer (NK) cells are lymphocytes that, along with neutrophils and monocytes/macrophages, participate in the critical innate immune response during viral infections, but can also mediate the antigen-specific memory responses generally associated with adaptive immunity. NK cells compose the first barrier that viruses must break through to continue replication and dissemination, and a weak NK cell response may predispose an individual to chronic viral infections. Both HHV-6A and HHV-6B can interfere with NK cell-mediated anti-viral responses but the mechanisms by which each of these viruses affect NK cell activity differs. In this review, we will explore the nuanced relationships between the two viruses and NK cells, discussing, in addition, relevant disease associations.

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.

Efficacy of a Cell-Cycle Decoying Killer Adenovirus on 3-D Gelfoam®-Histoculture and Tumor-Sphere Models of Chemo-Resistant Stomach Carcinomatosis Visualized by FUCCI Imaging

Stomach cancer carcinomatosis peritonitis (SCCP) is a recalcitrant disease. The goal of the present study was to establish an in vitro-in vivo-like imageable model of SCCP to develop cell-cycle-based therapeutics of SCCP. We established 3-D Gelfoam^® histoculture and tumor-sphere models of SCCP. FUCCI-expressing MKN-45 stomach cancer cells were transferred to express the fluorescence ubiquinized cell-cycle indicator (FUCCI). FUCCI-expressing MKN-45 cells formed spheres on agarose or on Gelfoam^® grew into tumor-like structures with G₀/G₁ cancer cells in the center and S/G₂ cancer cells located in the surface as indicated by FUCCI imaging when the cells fluoresced red or green, respectively. We treated FUCCI-expressing cancer cells forming SCCP tumors in Gelfoam^® histoculture with OBP-301, cisplatinum (CDDP), or paclitaxel. CDDP or paclitaxel killed only cycling cancer cells and were ineffective against G₁/G₂ MKN-45 cells in tumors growing on Gelfoam^®. In contrast, the telomerase-dependent adenovirus OBP-301 decoyed the MKN-45 cells in tumors on Gelfoam^® to cycle from G₀/G₁ phase to S/G₂ phase and reduced their viability. CDDP- or paclitaxel-treated MKN-45 tumors remained quiescent and did not change in size. In contrast, OB-301 reduced the size of the MKN-45 tumors on Gelfoam^®. We examined the cell cycle-related proteins using Western blotting. CDDP increased the expression of p53 and p21 indicating cell cycle arrest. In contrast, OBP-301 decreased the expression of p53 and p21 Furthermore, OBP-301 increased the expression of E2F and pAkt as further indication of cell cycle decoy. This 3-D Gelfoam^® histoculture and FUCCI imaging are powerful tools to discover effective therapy of SCCP such as OBP-301.

Human Herpesviruses as Copathogens of HIV Infection, Their Role in HIV Transmission, and Disease Progression

Of eight human herpesviruses (HHVs), often, only herpes simplex virus types 1 (HSV-1) and 2 (HSV-2) find mention in medical literature as both of these viruses are commonly associated with genital lesions and oral ulcers, commonly known as cold sores. However, role of human herpesviruses as copathogens and in aggravation and in the transmission of other human diseases, especially the Acquired immunodeficiency syndrome (HIV/AIDS) has only very recently been recognized. Therefore, screening and treating subclinical HHV infections may offer slowing of HIV infection, disease progression, and its transmission. Beside HSV-1 and HSV-2, HHV-3 a causative agent of herpes zoster remained one of the first manifestations of HIV disease before the era of highly active antiretroviral therapy (HAART). HHV-5 also known as human Cytomegalovirus infection remains a significant risk factor for HIV-associated mortality and morbidity even in HAART era. It is proposed that Cytomegalovirus viremia could be a better predictor of HIV disease progression than CD4+ T-lymphocyte count. The role of HHV-4 or Epstein-Burr virus and HHV-6, HHV-7, and HHV-8 is still being investigated in HIV disease progression. This review provides insight into the current understanding about these 8 HHVs, their co-pathogenesis, and role in HIV/AIDS disease progression. The review also covers recent literature in favor and against administering anti-HHV treatment along with HAART for slower AIDS progression and interrupted sexual transmission.

Piracy on the molecular level: human herpesviruses manipulate cellular chemotaxis

Cellular chemotaxis is important to tissue homeostasis and proper development. Human herpesvirus species influence cellular chemotaxis by regulating cellular chemokines and chemokine receptors. Herpesviruses also express various viral chemokines and chemokine receptors during infection. These changes to chemokine concentrations and receptor availability assist in the pathogenesis of herpesviruses and contribute to a variety of diseases and malignancies. By interfering with the positioning of host cells during herpesvirus infection, viral spread is assisted, latency can be established and the immune system is prevented from eradicating viral infection.

Inhibition of interleukin-2 gene expression by human herpesvirus 6B U54 tegument protein

Human herpesvirus 6B (HHV-6B) is a ubiquitous pathogen causing lifelong infections in approximately 95% of humans worldwide. To persist within its host, HHV-6B has developed several immune evasion mechanisms, such as latency, during which minimal proteins are expressed, and the ability to disturb innate and adaptive immune responses. The primary cellular targets of HHV-6B are CD4(+) T cells. Previous studies by Flamand et al. (L. Flamand, J. Gosselin, I. Stefanescu, D. Ablashi, and J. Menezes, Blood 85:1263-1271, 1995) reported on the capacity of HHV-6A as well as UV-irradiated HHV-6A to inhibit interleukin-2 (IL-2) synthesis in CD4(+) lymphocytes, suggesting that viral structural components could be responsible for this effect. In the present study, we identified the HHV-6B U54 tegument protein (U54) as being capable of inhibiting IL-2 expression. U54 binds the calcineurin (CaN) phosphatase enzyme, causing improper dephosphorylation and nuclear translocation of NFAT (nuclear factor of activated T cells) proteins, resulting in suboptimal IL-2 gene transcription. The U54 GISIT motif (amino acids 293 to 297), analogous to the NFAT PXIXIT motif, contributed to the inhibition of NFAT activation. IMPORTANCE Human herpesvirus 6A (HHV-6A) and HHV-6B are associated with an increasing number of pathologies. These viruses have developed strategies to avoid the immune response allowing them to persist in the host. Several studies have illustrated mechanisms by which HHV-6A and HHV-6B are able to disrupt host defenses (reviewed in L. Dagna, J. C. Pritchett, and P. Lusso, Future Virol. 8:273-287, 2013, doi:10.2217/fvl.13.7). Previous work informed us that HHV-6A is able to suppress synthesis of interleukin-2 (IL-2), a key immune growth factor essential for adequate T lymphocyte proliferation and expansion. We obtained evidence that HHV-6B also inhibits IL-2 gene expression and identified the mechanisms by which it does so. Our work led us to the identification of U54, a virion-associated tegument protein, as being responsible for suppression of IL-2. Consequently, we have identified HHV-6B U54 protein as playing a role in immune evasion. These results further contribute to our understanding of HHV-6 interactions with its human host and the efforts deployed to ensure its long-term persistence.

Invading cancer cells are predominantly in G0/G1 resulting in chemoresistance demonstrated by real-time FUCCI imaging

Invasive cancer cells are a critical target in order to prevent metastasis. In the present report, we demonstrate real-time visualization of cell cycle kinetics of invading cancer cells in 3-dimensional (3D) Gelfoam® histoculture, which is in vivo-like. A fluorescence ubiquitination cell cycle indicator (FUCCI) whereby G0/G1 cells express a red fluorescent protein and S/G2/M cells express a green fluorescent protein was used to determine the cell cycle position of invading and non-invading cells. With FUCCI 3D confocal imaging, we observed that cancer cells in G0/G1 phase in Gelfoam® histoculture migrated more rapidly and further than cancer cells in S/G2/M phases. Cancer cells ceased migrating when they entered S/G2/M phases and restarted migrating after cell division when the cells re-entered G0/G1. Migrating cancer cells also were resistant to cytotoxic chemotherapy, since they were preponderantly in G0/G1, where cytotoxic chemotherapy is not effective. The results of the present report suggest that novel therapy targeting G0/G1 cancer cells should be developed to prevent metastasis.

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.

Wolbachia variants induce differential protection to viruses in Drosophila melanogaster: a phenotypic and phylogenomic analysis

Wolbachia are intracellular bacterial symbionts that are able to protect various insect hosts from viral infections. This tripartite interaction was initially described in Drosophila melanogaster carrying wMel, its natural Wolbachia strain. wMel has been shown to be genetically polymorphic and there has been a recent change in variant frequencies in natural populations. We have compared the antiviral protection conferred by different wMel variants, their titres and influence on host longevity, in a genetically identical D. melanogaster host. The phenotypes cluster the variants into two groups--wMelCS-like and wMel-like. wMelCS-like variants give stronger protection against Drosophila C virus and Flock House virus, reach higher titres and often shorten the host lifespan. We have sequenced and assembled the genomes of these Wolbachia, and shown that the two phenotypic groups are two monophyletic groups. We have also analysed a virulent and over-replicating variant, wMelPop, which protects D. melanogaster even better than the closely related wMelCS. We have found that a ~21 kb region of the genome, encoding eight genes, is amplified seven times in wMelPop and may be the cause of its phenotypes. Our results indicate that the more protective wMelCS-like variants, which sometimes have a cost, were replaced by the less protective but more benign wMel-like variants. This has resulted in a recent reduction in virus resistance in D. melanogaster in natural populations worldwide. Our work helps to understand the natural variation in wMel and its evolutionary dynamics, and inform the use of Wolbachia in arthropod-borne disease control.

Cytokine and chemokine responses in the blood and cerebrospinal fluid of patients with human herpesvirus 6B-associated acute encephalopathy with biphasic seizures and late reduced diffusion

Acute encephalopathy with biphasic seizures and late reduced diffusion has become increasingly common among various types of human herpesvirus 6B (HHV-6B) encephalitis at the time of primary viral infection. The aim of the present study is to explore the pathophysiology of HHV-6B-associated acute encephalopathy with biphasic seizures and late reduced diffusion. Five cytokines and five chemokines were measured in serum and cerebrospinal fluid (CSF) obtained from 12 HHV-6B-associated acute encephalopathy with biphasic seizures and late reduced diffusion patients and 19 control exanthem subitum (without complications) patients. Serum interleukin (IL)-10 (P = 0.007) and IL-8 (P = 0.025) were significantly higher in the patients with the disease than controls. Serum IL-1β (P = 0.034) and monocyte chemoattractant protein (MCP)-1 (P = 0.002) were significantly higher in the controls than patients with the disease. In patients with the disease, IL-10 (P = 0.012), regulated on activation normal T cell expressed and secreted (RANTES; P = 0.001), and monokine induced by interferon γ (MIG; P = 0.001) were significantly higher in serum than CSF, meanwhile IL-6 (P = 0.034), IL-8 (P = 0.034), and MCP-1 (P = 0.001) were significantly higher in CSF than serum. Additionally, serum IL-10 was significantly higher in the disease patients with sequelae than those without sequelae (P = 0.016). Several cytokines and chemokines may be associated with the pathogenesis of acute encephalopathy with biphasic seizures and late reduced diffusion. Moreover, the regulation of cytokine networks appears to be different between peripheral blood (systemic) and central nervous system.

Human Herpesvirus 6 and Neuroinflammation

Human herpesvirus (HHV-) 6A and HHV-6B are two distinct β-herpesviruses which have been associated with various neurological diseases, including encephalitis, meningitis, epilepsy, and multiple sclerosis. Although the reactivation of both viruses is recognized as the cause of some neurological complications in conditions of immunosuppression, their involvement in neuroinflammatory diseases in immunocompetent people is still unclear, and the mechanisms involved have not been completely elucidated. Here, we review the available data providing evidence for the capacity of HHV-6A and -6B to infect the central nervous system and to induce proinflammatory responses by infected cells. We discuss the potential role of both viruses in neuroinflammatory pathologies and the mechanisms which could explain virus-induced neuropathogenesis.

Immunomodulation and immunosuppression by human herpesvirus 6A and 6B

Like other members of the Herpesviridae family, human herpesvirus (HHV)-6A and HHV-6B have developed a wide variety of strategies to modulate or suppress host immune responses and, thereby, facilitate their own spread and persistence in vivo. Long considered two variants of the same virus, HHV-6A and HHV-6B have recently been reclassified as distinct viral species, although the established nomenclature has been maintained. In this review, we summarize the distinctive profiles of interaction of these two viruses with the human immune system. Both HHV-6A and HHV-6B display a tropism for CD4+ T lymphocytes, but they can also infect, in a productive or nonproductive fashion, other cells of the immune system. However, there are important differences regarding the ability of each virus to infect cytotoxic effector cells, as HHV-6A has been shown to productively infect several of these cells, whereas HHV-6B infects them inefficiently at best. In addition to direct cytopathic effects, both HHV-6A and HHV-6B can interfere with immunologic functions to varying degrees via cytokine modulation, including blockade of IL-12 production by professional antigen-presenting cells, modulation of cell-surface molecules essential for T-cell activation, and expression of viral chemokines and chemokine receptors. Some of these effects are related to signaling through and downregulation of the viral receptor, CD46, a key molecule linking innate and adaptive immune responses. Increasing attention has recently been focused on the importance of viral interactions with dendritic cells, which may serve both as targets of virus-mediated immunosuppression and as vehicles for viral transfer to CD4+ T cells. Our deepening knowledge of the mechanisms developed by HHV-6A and HHV-6B to evade immunologic control may lead to new strategies for the prevention and treatment of the diseases associated with these viruses. Moreover, elucidation of these viral mechanisms may uncover new avenues to therapeutically manipulate or modulate the immune system in immunologically mediated human diseases.

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.

[Human herpesvirus-6 and human herpesvirus-7 (HHV-6, HHV-7)]

human herpesvirus 6 (HHV-6) is the major causative agent of exanthem subitum which is one of popular diseases in infant, and establishes latent infections in adults of more than 90%. Recently, the encephalitis caused by reactivated- HHV-6 has been shown in patients after transplantation. In addition, the relationship HHV-6 and drug-induced hypersensitivity syndrome has also been reported. human herpesvirus 7 (HHV-7) was isolated from the stimulated-peripheral blood lymphocytes of a healthy individual, and also causes exanthema subitum. Both viruses are related viruses which belong to betaherpesvirus subfamily, and replicate and produce progeny viruses in T cells.

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.

Epstein-Barr virus but not cytomegalovirus is associated with reduced vaccine antibody responses in Gambian infants

BACKGROUND

Epstein-Barr virus (EBV) and cytomegalovirus (CMV) are persistent herpesviruses that have various immunomodulatory effects on their hosts. Both viruses are usually acquired in infancy in Sub-Saharan Africa, a region where childhood vaccines are less effective than in high income settings. To establish whether there is an association between these two observations, we tested the hypothesis that infection with one or both viruses modulate antibody responses to the T-cell independent meningococcal polysaccharide vaccine and the T-cell dependent measles vaccines.

METHODOLOGY/PRINCIPAL FINDINGS

Infection with EBV and CMV was diagnosed by the presence of virus-specific IgM in the peripheral blood or by the presence of IgG at higher levels than that found in umbilical cord blood. Anti-meningococcus IgG and IgM were quantified by ELISA. Anti-measles antibody responses were quantified by haemagglutinin antibody inhibition assay. Infants infected with EBV had reduced IgG and IgM antibody responses to meningococcal polysaccharides and to measles vaccine. Infection with CMV alone predicted no changes in the response to meningococcal polysaccharide. While CMV alone had no discernable effect on the antibody response to measles, the response of infants infected with both CMV and EBV was similar to that of infants infected with neither, suggesting that the effects of CMV infection countered the effects of EBV on measles antibody responses.

CONCLUSIONS

The results of this exploratory study indicate that infection with EBV is associated with reduced antibody responses to polysaccharides and to measles vaccine, but suggest that the response to T-cell dependent antigens such as measles haemagglutinin may be restored by infection with CMV.

Kinetics of cytokine and chemokine responses in patients with primary human herpesvirus 6 infection

BACKGROUND

Cytokines and chemokines induced by human herpesvirus 6 (HHV-6) infection may play an important role in the observed HHV-6-associated clinical complications. However, basic data for cytokine and chemokine synthesis in primary HHV-6 infected patient without complication is lacking.

OBJECTIVE

Aim of this study was to elucidate basic kinetic data for expressions of cytokines and chemokines in patients with primary HHV-6 infection without complication.

STUDY DESIGN

Twenty-six patients suffering from fever were enrolled in this study. Fourteen biomarkers were measured in 74 serially collected sera samples from 26 patients. Additionally, serum samples obtained from 14 healthy children were used for control.

RESULTS

Twenty of the 26 patients were diagnosed with primary HHV-6 infection based on viral isolation and serological analysis. The mean age (P=0.1289) and proportion of males to females (P=0.9999) between the patients with and without primary HHV-6 infection were not statistically different. At the acute phase of the disease, three cytokines (IFN-γ; P=0.0046, IL-2; P=0.0366, and IL-4; P=0.0255) and one chemokine (MCP-1; P=0.0019) were significantly higher in patients with primary HHV-6 infection compared to those without infection. Interleukin-5 levels during the convalescent period were significantly higher in patients with HHV-6 infection (P=0.0205). By 1 month post-infection, cytokine and chemokine expression had returned to almost basal levels.

CONCLUSION

As suggested by the previous in vitro studies, present in vivo analysis also suggests that HHV-6 has potency for induction of cytokines and chemokines.

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.

CCL3L1 copy number is a strong genetic determinant of HIV seropositivity in Caucasian intravenous drug users

BACKGROUND

A high copy number of CCL3L1, the most potent human immunodeficiency virus (HIV)-suppressive chemokine, associates with reduced HIV susceptibility. Whether CCL3L1 influences acquisition of multiple blood-borne infections (eg, hepatitis C virus [HCV], HIV, and hepatitis B virus [HBV] infections), which occur commonly among injection drug users (IDUs), is unknown.

METHODS

We determined CCL3L1 copy number by real-time polymerase chain reaction among 374 Caucasian IDUs from Estonia; 285 were HCV positive, 208 were HIV positive, 177 were HCV and HIV positive, and 57 were HCV and HIV negative.

RESULTS

In univariate and multivariate analyses, HCV and HBV seropositivity and duration of IDU each strongly predicted HIV seropositivity. A high CCL3L1 copy number (>2) was associated with an 80% reduced risk of acquiring HIV infection after adjusting for age, sex, HCV and HBV status, CCR5-Delta32 polymorphism, and IDU duration (odds ratio, 0.20; 95% confidence interval, 0.09-0.45). By contrast, CCL3L1 gene dose did not influence HCV seropositivity. Among HCV-positive IDUs, there was a 3.5-fold overrepresentation and 65% underrepresentation of a high CCL3L1 copy number among HCV-positive, HIV-negative subjects and HCV-positive, HIV-positive subjects, respectively.

CONCLUSION

Among IDUs with extensive exposure to HCV and HIV, CCL3L1 copy number is a major determinant of HIV seropositivity but not of HCV seropositivity. The contrasting distribution of a protective high CCL3L1 copy number among HCV-positive, HIV-negative IDUs versus HCV-positive, HIV-positive IDUs may reflect that HIV preferentially selects for subjects with a low CCL3L1 gene dose.

Human herpesvirus 6

Az 1986-ban felfedezett emberi 6-os herpeszvírus A és B változata molekuláris tulajdonságai alapján a legősibb emberi herpeszvírus. A B változat cseppfertőzéssel terjed a tünetmentes vírusürítő felnőttekről a két év alatti kisgyermekekre, akikben alkalmilag exanthema subitum jöhet létre. A vírus a CD4+ macrophagokat, lymphocytákat fertőzi, utóbbiakban élethossziglan lappangás, időnként a nyálmirigyekben vírustermeléssel járó perzisztencia alakul ki. Felnőttkorban ez a változat csontvelő- és szervátültetések kapcsán, immunszuppresszió talaján reaktiválódik, és akár halálos szövődményeket hoz létre. Sclerosis multiplex, idült fáradtság tünetegyüttes, Hodgkin- és nem Hodgkin-lymphomák kialakulásában kofaktor. A CD+-sejteket fertőző és bennük lappangó A változat közvetlen kórokozó képessége nem ismert. A HIV-fertőzést rendkívül erősen transzaktiváljain vitroés betegekben egyaránt. Papillomavírusok által okozott daganatokban is transzaktivátor. Mindkét vírusváltozat kórokozó képessége a megváltozott citokin- és kemokinegyensúlyon alapszik. A két változat elkülönítése szerológiailag nehézkes, erre a savóból vagy a fehérvérsejtekből végzett változatspecifikus PCR alkalmas. A súlyos komplikációk kezelésére, esetleg kemoprofilaxisára ganciclovir, esetleg foscarnet és cidofovir használható.

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.

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.

Inhibition of HIV-1 replication in human monocyte-derived macrophages by parasite Trypanosoma cruzi

BACKGROUND

Cells of monocyte/macrophage lineage are one of the major targets of HIV-1 infection and serve as reservoirs for viral persistence in vivo. These cells are also the target of the protozoa Trypanosoma cruzi, the causative agent of Chagas disease, being one of the most important endemic protozoonoses in Latin America. It has been demonstrated in vitro that co-infection with other pathogens can modulate HIV replication. However, no studies at cellular level have suggested an interaction between T. cruzi and HIV-1 to date.

METHODOLOGY/PRINCIPAL FINDINGS

By using a fully replicative wild-type virus, our study showed that T. cruzi inhibits HIV-1 antigen production by nearly 100% (p<0.001) in monocyte-derived macrophages (MDM). In different infection schemes with luciferase-reporter VSV-G or BaL pseudotyped HIV-1 and trypomastigotes, T. cruzi induced a significant reduction of luciferase level for both pseudotypes in all the infection schemes (p<0.001), T. cruzi-HIV (>99%) being stronger than HIV-T. cruzi (approximately 90% for BaL and approximately 85% for VSV-G) infection. In MDM with established HIV-1 infection, T. cruzi significantly inhibited luciferate activity (p<0.01). By quantifying R-U5 and U5-gag transcripts by real time PCR, our study showed the expression of both transcripts significantly diminished in the presence of trypomastigotes (p<0.05). Thus, T. cruzi inhibits viral post-integration steps, early post-entry steps and entry into MDM. Trypomastigotes also caused a approximately 60-70% decrease of surface CCR5 expression on MDM. Multiplication of T. cruzi inside the MDM does not seem to be required for inhibiting HIV-1 replication since soluble factors secreted by trypomastigotes have shown similar effects. Moreover, the major parasite antigen cruzipain, which is secreted by the trypomastigote form, was able to inhibit viral production in MDM over 90% (p<0.01).

CONCLUSIONS/SIGNIFICANCE

Our study showed that T. cruzi inhibits HIV-1 replication at several replication stages in macrophages, a major cell target for both pathogens.

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.

Evolution of SIV toward RANTES resistance in macaques rapidly progressing to AIDS upon coinfection with HHV-6A

BACKGROUND

Progression to AIDS is often associated with the evolution of HIV-1 toward increased virulence and/or pathogenicity. Evidence suggests that a virulence factor for HIV-1 is resistance to CCR5-binding chemokines, most notably RANTES, which are believed to play a role in HIV-1 control in vivo. HIV-1 can achieve RANTES resistance either by phenotypic switching from an exclusive CCR5 usage to an expanded coreceptor specificity, or by the acquisition of alternative modalities of CCR5 usage. An infectious agent that might promote the evolution of HIV-1 toward RANTES resistance is human herpesvirus 6A (HHV-6A), which is frequently reactivated in HIV-1-infected patients and is a potent RANTES inducer in lymphoid tissue.

RESULTS

SIV isolates obtained from pig-tailed macaques (M. nemestrina) after approximately one year of single infection with SIV(smE660) or dual infection with SIV(smE660) and HHV-6A(GS) were characterized for their growth capacity and sensitivity to HHV-6A- and RANTES-mediated inhibition in human or macaque lymphoid tissues ex vivo. Four out of 4 HHV-6A-coinfected macaques, all of which progressed to full-blown AIDS within 2 years of infection, were found to harbor SIV variants with a reduced sensitivity to both HHV-6A and RANTES, despite maintaining an exclusive CCR5 coreceptor specificity; viruses derived from two of these animals replicated even more vigorously in the presence of exogenous HHV-6A or RANTES. The SIV variants that emerged in HHV-6A-coinfected macaques showed an overall reduced ex vivo replication capacity that was partially reversed upon addition of exogenous RANTES, associated with suppressed IL-2 and enhanced IFN-gamma production. In contrast, SIV isolates obtained from two singly-infected macaques, none of which progressed to AIDS, maintained HHV-6A/RANTES sensitivity, whereas the only AIDS progressor among singly-infected macaques developed an SIV variant with partial HHV-6A/RANTES resistance and increased replication capacity, associated with expanded coreceptor usage.

CONCLUSION

These results provide in vivo evidence of SIV evolution toward RANTES resistance in macaques rapidly progressing to AIDS. RANTES resistance may represent a common virulence factor allowing primate immunodeficiency retroviruses to evade a critical mechanism of host antiviral defense.

The bacterial symbiont Wolbachia induces resistance to RNA viral infections in Drosophila melanogaster

Wolbachia are vertically transmitted, obligatory intracellular bacteria that infect a great number of species of arthropods and nematodes. In insects, they are mainly known for disrupting the reproductive biology of their hosts in order to increase their transmission through the female germline. In Drosophila melanogaster, however, a strong and consistent effect of Wolbachia infection has not been found. Here we report that a bacterial infection renders D. melanogaster more resistant to Drosophila C virus, reducing the load of viruses in infected flies. We identify these resistance-inducing bacteria as Wolbachia. Furthermore, we show that Wolbachia also increases resistance of Drosophila to two other RNA virus infections (Nora virus and Flock House virus) but not to a DNA virus infection (Insect Iridescent Virus 6). These results identify a new major factor regulating D. melanogaster resistance to infection by RNA viruses and contribute to the idea that the response of a host to a particular pathogen also depends on its interactions with other microorganisms. This is also, to our knowledge, the first report of a strong beneficial effect of Wolbachia infection in D. melanogaster. The induced resistance to natural viral pathogens may explain Wolbachia prevalence in natural populations and represents a novel Wolbachia–host interaction.

Many symbiotic bacteria confer fitness benefits to the organisms that they infect. Wolbachia are one of the most widespread intracellular bacteria, infecting a great number of species of insects. Here we show that in the fruit fly Drosophila melanogaster, infection with Wolbachia increases resistance to a natural pathogen of Drosophila, an RNA virus called Drosophila C virus. Furthermore, we show that Wolbachia also increases resistance of Drosophila to two other RNA viruses (Nora and Flock House virus) but not to a DNA virus (Insect Iridescent Virus 6). These results identify a significant new factor that regulates D. melanogaster resistance to infection by RNA viruses. Our results add to a growing body of literature showing that the response of an organism to a particular pathogen is modulated by prior or contemporaneous interactions with other microorganisms. That the fruit fly clearly benefits from increased resistance to viruses may provide a solution to the longstanding puzzle as to why Wolbachia is so common in natural populations of D. melanogaster.

Wolbachia are one of the most widespread intracellular bacteria. InDrosophila melanogaster, the presence ofWolbachia increases resistance to infection by RNA viruses.

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.

Coinfection alters the playing field: herpesviruses induce acyclovir to inhibit HIV

The antiherpes drug acyclovir was found to inhibit HIV following its phosphorylation by human herpesviruses, providing a hypothesis to explain the observed beneficial effects of acyclovir therapy on HIV viral load and HIV disease progression. This report underscores the importance of studying HIV in the context of microbial copathogens.

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.

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.