CD68+ cells of monocyte/macrophage lineage in the environment of AIDS-associated and classic-sporadic Kaposi sarcoma are singly or doubly infected with human herpesviruses 7 and 6B

Update on human herpesvirus 7 pathogenesis and clinical aspects as a roadmap for future research

Human herpesvirus 7 (HHV-7) is a common virus that is associated with various human diseases including febrile syndromes, dermatological lesions, neurological defects, and transplant complications. Still, HHV-7 remains one of the least studied members of all human betaherpesviruses. In addition, HHV-7-related research is mostly confined to case reports, while in vitro or in vivo studies unraveling basic virology, transmission mechanisms, and viral pathogenesis are sparse. Here, we discuss HHV-7-related literature linking clinical syndromes to the viral life cycle, epidemiology, and viral immunopathogenesis. Based on our review, we propose a hypothetical model of HHV-7 pathogenesis inside its host. Furthermore, we identify important knowledge gaps and recommendations for future research to better understand HHV-7 diseases and improve therapeutic interventions.

A model approach to show that monocytes can enter microporous β-TCP ceramics

β-TCP ceramics are versatile bone substitute materials and show many interactions with cells of the monocyte-macrophage-lineage. The possibility of monocytes entering microporous β-TCP ceramics has however not yet been researched. In this study, we used a model approach to investigate whether monocytes might enter β-TCP, providing a possible explanation for the origin of CD68-positive osteoclast-like giant cells found in earlier works.We used flow chambers to unidirectionally load BC, PRP, or PPP into slice models of either 2 mm or 6 mm β-TCP. Immunofluorescence for CD68 and live/dead staining was performed after the loading process.Our results show that monocytes were present in a relevant number of PRP and BC slices representing the inside of our 2 mm slice model and also present on the actual inside of our 6 mm model. For PPP, monocytes were not found beyond the surface in either model.Our results indicate the possibility of a new and so far neglected constituent in β-TCP degradation, perhaps causing the process of ceramic degradation also starting from inside the ceramics as opposed to the current understanding. We also demonstrated flow chambers as a possible new in vitro model for interactions between blood and β-TCP.

Detection of HHV-6 Virus in specimen of a ductal pancreatic adenocarcinoma with comparison in tumor and normal tissue

AIMS

The association of human herpesvirus 6 (HHV-6) species with pancreatic cancer is controversially discussed. The aim of this study was to further investigate the postulated association and to identify the basis of HHV-6 DNA positivity reported for pancreatic cancer tissue.

METHODS

All samples of patients with pancreatic cancer (cancer and surrounding tissue) were analyzed for presence of HHV-6 DNA by PCR and then selected cases by immunohistochemistry.

RESULTS

Sixty eight per cent (68% = 52/77) of all patients were HHV-6 DNA positive in any of the samples, 49% (38/77) were positive in tumor tissue. Specimens of just one patient were HHV-6A DNA positive, all other patients were positive for HHV-6B. Immunohistochemical analysis of HHV-6 DNA positive samples did not reveal any specific HHV-6B protein positive tumor cell. In contrast, supposed immune cells presented intra- and peritumorally expressed HHV-6B-protein. The cause of presence of these cells in the tumor stroma is unknown, as of yet.

CONCLUSIONS

HHV-6 DNA-positivity of pancreatic cancer tissue described by us and others is probably not due to the infection of pancreatic cells by HHV-6, but rather due to the migration of HHV-6 positive immune cells into the pancreas. Based on our data, we suppose that there is no direct evidence for HHV-6 as a causative agent of pancreatic cancer, but further in-depth studies (including investigation of immune status of patients) are necessary to make definitive conclusions.

Co-infections and Pathogenesis of KSHV-Associated Malignancies

Kaposi’s sarcoma-associated herpesvirus (KSHV), also known as human herpes virus 8 (HHV-8) is one of the several carcinogenic viruses that infect humans. KSHV infection has been implicated in the development of Kaposi’s sarcoma (KS), primary effusion lymphoma, and multicentric Castleman’s Disease. While KSHV infection is necessary for the development of KSHV associated malignancies, it is not sufficient to induce tumorigenesis. Evidently, other co-factors are essential for the progression of KSHV induced malignancies. One of the most important co-factors, necessary for the progression of KSHV induced tumors, is immune suppression that frequently arises during co-infection with HIV and also by other immune suppressants. In this mini-review, we discuss the roles of co-infection with HIV and other pathogens on KSHV infection and pathogenesis.

The promotion of functional urinary bladder regeneration using anti-inflammatory nanofibers

Current attempts at tissue regeneration utilizing synthetic and decellularized biologic-based materials have typically been met in part by innate immune responses in the form of a robust inflammatory reaction at the site of implantation or grafting. This can ultimately lead to tissue fibrosis with direct negative impact on tissue growth, development, and function. In order to temper the innate inflammatory response, anti-inflammatory signals were incorporated through display on self-assembling peptide nanofibers to promote tissue healing and subsequent graft compliance throughout the regenerative process. Utilizing an established urinary bladder augmentation model, the highly pro-inflammatory biologic scaffold (decellularized small intestinal submucosa) was treated with anti-inflammatory peptide amphiphiles (AIF-PAs) or control peptide amphiphiles and used for augmentation. Significant regenerative advantages of the AIF-PAs were observed including potent angiogenic responses, limited tissue collagen accumulation, and the modulation of macrophage and neutrophil responses in regenerated bladder tissue. Upon further characterization, a reduction in the levels of M2 macrophages was observed, but not in M1 macrophages in control groups, while treatment groups exhibited decreased levels of M1 macrophages and stabilized levels of M2 macrophages. Pro-inflammatory cytokine production was decreased while anti-inflammatory cytokines were up-regulated in treatment groups. This resulted in far fewer incidences of tissue granuloma and bladder stone formation. Finally, functional urinary bladder testing revealed greater bladder compliance and similar capacities in groups treated with AIF-PAs. Data demonstrate that AIF-PAs can alleviate galvanic innate immune responses and provide a highly conducive regenerative milieu that may be applicable in a variety of clinical settings.

Identification of CD68(+) neutrophil granulocytes in in vitro model of acute inflammation and inflammatory bowel disease

CD-68 is widely regarded as a selective marker for human monocytes and macrophages and is commonly used in human pathology studies. The purpose of this study was to investigate the expression of CD-68 in human peripheral blood mononuclear cells (PBMCs), neutrophil granulocytes (NGs) and in inflamed intestinal tissue samples for comparison. PBMCs and NGs were isolated from heparinized human blood samples. Intestinal biopsies were obtained during routine endoscopic procedures from patients with inflammatory bowel disease (IBD), e.g. ulcerative colitis and Crohn's disease. Gene and protein expression was analyzed by real-time RT-PCR, Western blot and immunohistochemistry. Both PBMCs and NGs preparations contained cells that were positive for CD-68 and either neutrophil elastase (NE), or myeloperoxidase (MPO). CD-68(+)/NE(-)/MPO(-) cells were regarded as monocytes. CD-68 mRNA expression was detected in PBMCs and NGs preparations. With Western blot and by performing immunoprecipitation of cell lysate, we could clearly detect CD-68 in NGs, U-937, THP-1, Hep-G2, Jurkat cells and PBMCs. Identification of inflammatory cells in acutely inflamed colonic mucosa obtained from patients with IBD revealed a strong accumulation of CD-68(+)/MPO(+) cells compared to normal colonic mucosa. The uptake of the marker by phagocytosis was excluded by performing a double staining with CD-163/NE and CD-163/MPO in PBMCs, NGs cultures and in inflamed colonic mucosa. These results identify CD-68(+) NGs in peripheral blood and inflamed colonic mucosa. CD-68 is not only a marker for the macrophages-monocytes but also for NGs.

Characterization of infections of human leukocytes by non-polio enteroviruses

To elucidate the detailed susceptibilities of leukocytes to clinically important non-polio enteroviruses (EVs), primary monocytes and various human leukocyte cell lines were infected with coxsackievirus A24 (CVA24), coxsackievirus B3 (CVB3), and enterovirus 70 (EV70). The permissiveness was then assessed by determining virus replication and resultant cytopathic effects. Different EVs varied markedly in their ability to infect leukocyte cell lines. CVB3 replicated effectively in leukocytes of B-cell, T-cell, and monocyte origin, CVA24 in leukocytes of B-cell and monocyte origin, and EV70 in leukocytes of monocyte origin. Primary monocytes, as well as monocyte-derived U-937 cells, were permissive to all three EVs. We observed a positive correlation between cytotoxicity and active virus replication, except in CVB3-infected monocytes. U-937 cells efficiently generated CVB3 progeny virus without severe cellular damage, including cell death. Moreover, infectivity on leukocytes was not absolutely associated with the availability of viral receptors. These findings suggest that the susceptibility of human leukocytes to non-polio EVs may be responsible for virus transport during the viremic phase, particularly to secondary target organs, and that active replication of CVB3 in all human leukocyte lineages leads to greater dissemination, in agreement with the ability of CVB to cause systemic diseases.

A human herpesvirus miRNA attenuates interferon signaling and contributes to maintenance of viral latency by targeting IKKε

Type I interferon (IFN) signaling is the principal response mediating antiviral innate immunity. IFN transcription is dependent upon the activation of transcription factors IRF3/IRF7 and NF-κB. Many viral proteins have been shown as being capable of interfering with IFN signaling to facilitate evasion from the host innate immune response. Here, we report that a viral miRNA, miR-K12-11, encoded by Kaposi's sarcoma-associated herpesvirus (KSHV) is critical for the modulation of IFN signaling and acts through targeting I-kappa-B kinase epsilon (IKKɛ). Ectopic expression of miR-K12-11 resulted in decreased IKKɛ expression, while inhibition of miR-K12-11 was found to restore IKKɛ expression in KSHV-infected cells. Importantly, expression of miR-K12-11 attenuated IFN signaling by decreasing IKKɛ-mediated IRF3/IRF7 phosphorylation and by inhibiting the activation of IKKɛ-dependent IFN stimulating genes (ISGs), allowing miR-K12-11 suppression of antiviral immunity. Our data suggest that IKKɛ targeting by miR-K12-11 is an important strategy utilized by KSHV to modulate IFN signaling during the KSHV lifecycle, especially in latency. We also demonstrated that IKKɛ was able to enhance KSHV reactivation synergistically with the treatment of 12-O-tetradecanoylphorbol 13-acetate. Moreover, inhibition of miR-K12-11 enhanced KSHV reactivation induced by vesicular stomatitis virus infection. Taken together, our findings also suggest that miR-K12-11 can contribute to maintenance of KSHV latency by targeting IKKɛ.

Expression of CD68 in non-myeloid cell types

CD68, the human homologue of macrosialin, is commonly regarded as a selective marker for human monocytes and macrophages. Its expression is thought to be regulated by a macrophage-specific promoter. However, several immunohistochemical studies have indicated that CD68 antibodies also react with other haematopoietic and non-haematopoietic cell types. We investigated the expression of CD68 in various primary cells and carcinoma cell lines using immunohistochemistry, flow cytometry, Western blot analysis and qRT-PCR. Weak but significant immunoreactivity was detected in lymphocytes and several tumour cell lines whereas staining of primary fibroblasts and endothelial cells was comparable to macrophages. The intensity of CD68 staining in individual cell types depended on the antibody clone and the fixation technique. Anti-CD68 mAb KP1 should be used with great caution for frozen tissue sections due to its reactivity with a wide variety of cell types. Also, care should be taken when distinguishing macrophages from fibroblasts/stromal cells in paraffin sections after formalin fixation since both cell types are stained highly positive for CD68. In accordance, mRNA expression of CD68 was not only detected in macrophages and monocytes but also in fibroblasts as well as endothelial cells and tumour cells, although with a varying intensity. Cloning of full length 5'-sequences and determination of transcription start sites shows that macrophages and fibroblasts initiate transcription within the known promoter region; however, from different start sites, indicating alternative promoter architecture in myeloid versus non-myeloid cells. We suggest that CD68 is not a selective macrophage marker but rather a lysosomal protein that is enriched in macrophages.

Immunohistological evaluation of immune cell infiltrate in cutaneous Kaposi's sarcoma

Typically, Kaposi's sarcoma (KS) also presents with immune cell infiltrates. This study does immunophenotype characterization for demographics of some of these cells to test the hypothesis that 'development of end-stage (nodular/tumor) KS is associated with numeric alteration in immune cell infiltrates.' Fifteen cases of classic-KS (nodular/tumor) and 20 normal biopsies were examined using antigen-antibody reactions and immunoperoxidase staining for histiocytes (CD68), B cells (CD20) and T cells (CD3). Variations between normal and lesions were observed with significant increases in immune cell infiltrates (2.3+/-0.6 vs. 6.4+/-0.4); CD68(+) (4.0+/-1.0 vs. 7.0+/-0.5); CD3(+) (3.0+/-1.1 vs. 10.1+/-0.8); and CD20(+) (0.0+/-0.0 vs. 0.3+/-0.0). Increased density of immune cells in the nodular lesions of KS may reflect increased antigenicity of these lesions; the increase in T cells suggests enhanced T cell activity in KS. However, these issues should be tested by further studies.

Quantification of platelet composition in experimental venous thrombosis by real-time polymerase chain reaction

INTRODUCTION

Platelets play a key role in thrombus formation. Determination of the platelet component in a thrombus provides pathophysiological insights to the thrombotic event and aids in selecting an appropriate therapeutic intervention. In this study a sensitive and reliable method to characterize the cellular components of experimental thrombi was developed using real-time polymerase chain reaction (PCR).

METHODS AND RESULTS

Vena cava thrombosis was induced by either oxidative injury to topical FeCl(2) (FeCl(2)-VT) or stenosis-limited blood flow and a hypotonic pressure stress (stasis-VT) in rats. High levels of platelets were identified in the thrombus containing vessels by real-time PCR analysis of target gene amplification using the 2(-DeltaDeltaCT) values by normalizing the data with gene expression in naive vessels and with a housekeeping gene, ribosomal protein L32. By this analysis, the levels of PF-4 (as a platelet marker) mRNA were significantly higher in FeCl(2)-VT (2(-DeltaDeltaCT)=7.8) than in stasis-VT (2(-DeltaDeltaCT)=4.2, p<0.05). Enhanced platelet enrichment in FeCl(2)-VT was also confirmed qualitatively by scanning electronic microscopic analysis. In addition, real-time PCR using a panel of genes representing vascular injury, inflammation and thrombosis showed marked induction (2(-DeltaDeltaCT)>5) in MCP-1, IL-1beta, iNOS and P-selectin mRNA expression in both models.

CONCLUSIONS

These data demonstrate the utility of real-time PCR to quantitate platelets and other cell components in vascular thrombosis, which may facilitate the characterization and thus therapeutic intervention of a particular thrombotic event in both preclinical animal models and clinical conditions.

Anatomical mapping of human herpesvirus reservoirs of infection

Following primary infection, all eight human herpesviruses persist lifelong in the human host. However, a mapping of all anatomic sites of human herpesvirus persistence is lacking. Fresh tissue specimens representing approximately 40 major anatomic sites from eight autopsies were screened using a recently developed real-time PCR method for detection of all eight human herpesviruses. Patients with evidence of active herpesvirus infection (herpes simplex 1 (HSV-1), herpes simplex 2 (HSV-2), varicella-zoster virus (VZV), Epstein-Barr virus (EBV), cytomegalovirus (CMV), herpesvirus 6 (HHV-6), herpesvirus 7 (HHV-7), and herpesvirus 8 (HHV-8)) at the time of death were excluded to avoid detection of widely disseminated infection. Despite this precaution, widespread HSV-1 positivity (with blood positivity) was detected in one case-an elderly male who died of cardiac arrest. In a middle-aged male with HIV-AIDS, HSV-1 was found in neural and pharyngeal tissues, skin, cartilage, bone, and urinary bladder, whereas in two other cases, HSV-1 was restricted to neural tissues. HSV-2 was detected in a single site, the anus, in the male with HIV-AIDS. VZV was detected only twice, once in the adrenal gland and once in the small intestine. CMV was detected in three cases, most commonly in nasal mucosa, trachea, thyroid, intestine, and liver. EBV was detected in all eight cases, especially in nasal mucosa, tonsil, spleen, lymph node, tongue, and intestine, but in only two of six whole-blood specimens. HHV-6, like EBV, was detected in all eight cases, most commonly in salivary glands, thyroid, stomach, intestines, liver, and pancreas. HHV-7, like EBV and HHV-6, was detected in all eight cases, most commonly in salivary glands, tonsil, lymph nodes, and bone marrow. HHV-8 was detected in only two sites (both lymph nodes) from two cases. Herpesviruses were detected in three of six whole-blood specimens, including HSV-1, EBV, HHV-6, and HHV-7. These results represent the most comprehensive mapping of herpesvirus tissue distribution in humans reported to date.

Latent infection of human herpesvirus 7 in CD4(+) T lymphocytes

To determine the cell populations in peripheral blood that are infected latently with human herpesvirus 7 (HHV-7), the real-time polymerase chain reaction (PCR) was used to determine the quantities of viral DNA in adherent and non-adherent cells from 71 healthy volunteers. Real-time PCR, which detected the U31 gene of HHV-7, was developed to measure viral load. The majority of non-adherent cells (14/16; 87.5%) contained HHV-7 DNA, while most of the adherent cells did not (1/16; 6.3%). HHV-7 viral load in non-adherent cells was significantly higher than that in adherent cells (P < 0.0001). Then, HHV-7 DNA load was compared between the CD4-positive and -negative cell fractions derived from the non-adherent cells of 26 healthy adults. As in the previous experiment, only 2 (7.7%) of the 26 adherent cell specimens contained small amounts of HHV-7 DNA (27.7 copies/1 x 10(6) cells and 208.7 copies/1 x 10(6) cells). In contrast, 88.5% of CD4(+) T cell samples (23/26 specimens) were positive for HHV-7 DNA, ranging from 0.4 to 3,542.8 copies/1 x 10(6) cells. Viral DNA was detected in only 3 (11.5%) of the 26 CD4(-) T cell specimens, with 8.4, 63.5, and 74.1 copies/1 x 10(6) cells. HHV-7-positive DNA loads were significantly higher in the CD4(+) T cells than those observed in the CD4(-) T cells (P = 0.0005). The relationship between HHV-7 viral loads in non-adherent cells and those in saliva was investigated. Comparison of HHV-7 DNA load between blood CD4(+) T cells and saliva revealed that the HHV-7 DNA load in saliva correlated with that present in CD4(+) T cells (r = 0.415; P = 0.0174).

Phenotypic alterations and survival of monocytes following infection by human herpesvirus-6

Freshly isolated monocytes rapidly undergo physiological changes in vitro, resulting in programmed cell death (apoptosis). Activation of monocytes, which promotes differentiation into macrophages, is known to inhibit apoptotic processes. In the present study, we report that human herpesvirus-6 (HHV-6) prevents monocytes from undergoing spontaneous apoptosis during the first 72 hours of culture. Furthermore, significant alterations in cell-surface phenotype were observed after 72 hours of infection with HHV-6. HHV-6-infected monocyte cultures have considerably reduced levels of CD14, CD64 (FcgammaRI) and HLA-DR antigen on their surface, while CD32 (FcgammaRII) expression is unaffected. On the basis of these results, we hypothesize that HHV-6 promotes monocytes survival and causes phenotypic modifications that could favor immune evasion and ensure its persistence within the infected host.

Amplification of autoimmune disease by infection

Reports of infection with certain chronic persistent microbes (herpesviruses or Chlamydiae) in human autoimmune diseases are consistent with the hypothesis that these microbes are reactivated in the setting of immunodeficiency and often target the site of autoimmune inflammation. New experimental animal models demonstrate the principle. A herpesvirus or Chlamydia species can be used to infect mice with induced transient autoimmune diseases. This results in increased disease severity and even relapse. The evidence suggests that the organisms are specifically imported to the inflammatory sites and cause further tissue destruction, especially when the host is immunosuppressed. We review the evidence for the amplification of autoimmune inflammatory disease by microbial infection, which may be a general mechanism applicable to many human diseases. We suggest that patients with autoimmune disorders receiving immunosuppressing drugs should benefit from preventive antiviral therapy.

Histological features of kaposi sarcoma in a patient receiving highly active antiviral therapy

The introduction of highly active anti-retroviral therapy (HAART) has changed the clinical presentation of skin diseases in patients with the Acquired Immune Deficiency Syndrome (AIDS). This occurs as a consequence of a newly recognized effect of this therapy known as the "Immune Reconstitution Syndrome," which develops with improvement of immunity. One manifestation of this syndrome is alteration of the natural history of Kaposi sarcoma (KS). While there are multiple reports of KS regression during HAART, there is little documentation of the histologic changes that occur. We present the case of a 55-year-old homosexual male with KS for over 4 years who underwent 6 biopsies over a 3-year period before, during, and after HAART. Kaposi sarcoma lesions prior to HAART were multinodular with ill-defined borders clinically and demonstrated typical features of nodular stage KS histologically. After initiation of HAART in this patient, lesions became uninodular, well circumscribed, and histologically were noted to be less cellular and surrounded by a dense fibrotic stroma. Although the mechanisms for these histologic changes are not clear, it may be due to activity of HAART against human herpesvirus type 8 (HHV-8), the causative agent of KS, to reconstitution of immunity due to diminution in HIV viral load, or both.

Immunohistochemical assessment of fractalkine, inflammatory cells, and human herpesvirus 7 in human salivary glands

Human fractalkine (CX3CL1), a delta-chemokine, is implicated in the mediation of multiple cell functions. In addition to serving as a chemotactic factor for mononuclear cell subtypes, membrane-bound fractalkine may promote viral infection by interacting with virions that encode putative fractalkine-binding proteins. Fractalkine expression in normal epithelial tissues studied to date is either constitutive or is upregulated with inflammation. In salivary glands, the expression of fractalkine is unknown. Moreover, salivary glands are a major site for the persistent and productive infection by human herpesvirus (HHV)-7, which encodes two putative fractalkine-binding gene products, U12 and U51. Surprisingly, the cellular distribution of HHV-7 in major salivary glands has not been explored. We therefore determined by immunohistochemistry the cellular localization of fractalkine in three different salivary glands: parotid, submandibular, and labial glands. Fractalkine expression was highly variable, ranging from high to undetectable levels. We further examined the association of fractalkine with inflammatory cell infiltration or HHV-7 infection of salivary epithelial cells. Inflammatory cells were always adjacent to epithelial cells expressing fractalkine, consistent with a function of fractalkine in inflammatory cell recruitment and/or retention in salivary glands. In contrast, HHV-7-infected epithelial cells did not always express fractalkine, suggesting that fractalkine may not be an absolute requirement for viral entry.

Detection of a gene cluster that is dispensable for human herpesvirus 6 replication and latency

The U3-U7 gene cluster of human herpesvirus 6 (HHV-6) was replaced with an enhanced green fluorescent protein-puromycin gene cassette containing the cytomegalovirus major immediate-early promoter. Neither viral replication in T cells nor latency and reactivation in macrophages was impaired. During HHV-6 latency, the cytomegalovirus promoter used the transcription start sites employed in cytomegalovirus latency.

Recognition of a novel stage of betaherpesvirus latency in human herpesvirus 6

Latency-associated transcripts of human herpesvirus 6 (H6LTs) (K. Kondo et al. J. Virol. 76:4145-4151, 2002) were maximally expressed at a fairly stable intermediate stage between latency and reactivation both in vivo and in vitro. H6LTs functioned as sources of immediate-early protein 1 at this stage, which up-regulated the viral reactivation.

Human herpesvirus 6: molecular biology and clinical features

Human herpesvirus 6 (HHV-6) exists as distinct variants HHV-6A and HHV-6B. The complete genomes of HHV-6A and HHV-6B have been sequenced. HHV-6B contains 97 unique genes. CD46 is the cell receptor for HHV-6, explaining its broad tissue tropism but its restricted host-species range. HHV-6 utilizes a number of strategies to down-regulate the host immune response, including molecular mimicry by production of a functional chemokine and chemokine receptors. Immunosuppression is enhanced by depletion of CD4 T lymphocytes via direct infection of intra-thymic progenitors and by apoptosis induction. Infection is widespread in infants between 6 months and 2 years of age. A minority of infants develop roseola infantum, but undifferentiated febrile illness is more common. Reactivation from latency occurs in immunocompromised hosts. Organ-specific clinical syndromes occasionally result, but indirect effects including interactions with other viruses such as human immunodeficiency virus type 1 and human cytomegalovirus or graft dysfunction in transplant recipients may be more significant complications in this population. Recent advances in quantitative PCR are providing additional insights into the natural history of infection in paediatric populations and immunocompromised hosts.

Human herpesvirus 7 in dermatology: what role does it play?

Human herpesvirus 7 (HHV-7) was discovered in 1989 as a new member of the beta-herpesvirus subfamily. Primary infection occurs early in life and manifests as exanthema subitum, or other febrile illnesses mimicking measles and rubella. Thus, HHV-7 has to be considered as a causative agent in a variety of macular-papular rashes in children. In addition, HHV-7 was found in some cases of other inflammatory skin disorders, such as psoriasis. There are controversial data on the detection of HHV-7 in pityriasis rosea, but so far there is not enough evidence for a pathogenetic association of HHV-7 with this exanthematic skin disease. Although HHV-7 can be found in some cases of Hodgkin's disease, there are no data supporting a direct causative role in this lymphoma type nor in other nodal or primary cutaneous lymphomas. In various epidemiologic forms of Kaposi's sarcoma, infection of monocytic cells with HHV-7 was demonstrated, which may indirectly influence tumor biology. In the context of immunosuppression, HHV-7 has recently been identified as an emerging pathogen in transplant recipients and may exacerbate graft rejection in renal transplant recipients. The ability of HHV-7 to induce cytokine production in infected cells could make HHV-7 an important pathogenetic co-factor in inflammatory and neoplastic disorders. Moreover, the restricted cellular tropism of HHV-7 may render this virus an interesting vector for gene therapy. Thirteen years after the discovery of HHV-7, there has been considerable progress in characterizing its genetic structure, virus-induced effects on infected host cells and in the development of diagnostic tools. Nevertheless, the role of HHV-7 in various skin diseases and the clinical manifestations of reactivation of HHV-7 infection have still to be defined.

Activation of monocyte cyclooxygenase-2 gene expression by human herpesvirus 6. Role for cyclic AMP-responsive element-binding protein and activator protein-1

Prostaglandin E(2) (PGE(2)) is an arachidonic acid metabolite mainly produced by activated monocytes/macrophages (Mo/Mphi) that display broad immunomodulatory activities. Several viruses capable of infecting Mo/Mphi modulate PGE(2) synthesis in a way that favors the infection processes and the spread of virions. In the present work, we studied the effect of human herpesvirus 6 (HHV-6) infection of Mo/Mphi on PGE(2) synthesis. Our results indicate that HHV-6 induces COX-2 gene expression and PGE(2) synthesis within a few hours of infection. We mapped the different promoter elements associated with COX-2 gene activation by HHV-6 to two cis-acting elements: a cyclic AMP-responsive element and an activator protein-1 element. HHV-6 immediate-early protein 2 was identified as a modulator of COX-2 gene expression in Mo/Mphi. Finally, addition of PGE(2) to HHV-6-infected peripheral blood mononuclear cells cultures was found to increase significantly viral replication. Overall, these results further contribute to the immunomodulatory properties of HHV-6 and highlight a potential role for eicosanoids in the replication process of this virus.

Human herpesvirus 6 and human herpesvirus 7: emerging pathogens in transplant patients

Human herpesvirus 6 (HHV-6) and HHV-7 are two recently identified beta-herpesviruses, genetically related to human cytomegalovirus (CMV). Infection with both viruses is common worldwide with rates of seropositivity in adults over 90%. Infection with both viruses usually occurs in early childhood. In this age group HHV-6 is a cause of febrile illness including exanthem subitum, and likewise, primary HHV-7 infection has been associated with febrile illness. Similar to the other human herpesviruses, in particular CMV, the viruses have the potential for enhanced pathogenicity in the immunocompromised host. Active infection with both viruses is common following bone marrow or solid organ transplantation, most likely through reactivation of recipient's virus or re-infection considering their high prevalence in the population. Both viruses can be detected by PCR in the peripheral blood of healthy individuals and although the significance of blood-borne transmission is not clear, a preliminary study suggested that it was not significant for HHV-6. However, there is growing evidence that these viruses may be medically important in the post-transplant period. In bone marrow transplant patients HHV-6 has been associated with a range of clinical disease including encephalitis, interstitial pneumonitis, early and late graft failure and bone marrow suppression. There is also growing evidence for potential interactions among the beta-herpesviruses in liver and renal transplant patients. HHV-6 infection has been associated with an increased risk of developing CMV disease and opportunistic infections and HHV-7 infection has also been linked to an increased risk of CMV disease.

Strong interaction between human herpesvirus 6 and peripheral blood monocytes/macrophages during acute infection

Human herpesvirus 6 (HHV-6) encodes a viral chemokine and chemokine receptors that may modify the functions of monocytes/macrophages (MO/M phi) during productive HHV-6 infection. The interactions between HHV-6 and MO/M phi during acute infection, however, remain poorly understood. In this study, we investigated the tropism of HHV-6 in peripheral blood mononuclear cells (PBMCs) during acute infection. We detected 637 +/- 273 copies of viral DNA in 10(4) MO/M phi. in contrast, in 10(4) CD4+ T cells, which have been reported to be viral carriers during the acute infection of HHV-6, we found only 115 +/- 42 copies of viral DNA. Consistent with these data, virus was isolated from MO/M phi an order of magnitude more frequently than from CD4+ T cells. Viral mRNA U79/80, which indicates viral replication, was detectable in the MO/M phi. In addition, the mRNAs that encode viral chemokine receptors U12 and U51, which may modify the function of MO/M phi, were expressed in the cells. Therefore, productively infected MO/M phi may be the dominant cell population that is responsible for HHV-6 viremia during acute HHV-6 infection. The strong interaction of HHV-6 with MO/M phi may be partly responsible for the pathogenesis of this virus.

Synergism between HIV and other viruses in the mouth

The HIV family replicate in and are shed from the mouth. Oral sexual practices potentially contribute to the overall extent of HIV transmission, particularly if high-risk practices are not restricted. Herpesviruses and papillomaviruses that appear in the oral cavity can determine oral HIV replication. The mechanisms probably include heterologous transactivation, enhanced expression of HIV receptors and co-receptors in target cells, release of cytokines and chemokines, and production of superantigens. Oral diseases peculiar to, or more common in, the HIV-infected patient further predispose to heightened oral HIV replication and trafficking. Defining the mechanisms by which oral viruses interact with HIV in the co-infected host should permit intervention measures against oral HIV transmission to be more precisely targeted.

Identification of human herpesvirus 6 latency-associated transcripts

Four kinds of latency-associated transcripts of human herpesvirus 6 were identified which were detected only in latently infected cells. Although they were oriented in the same direction as the immediate-early 1 and 2 (IE1/IE2) genes and shared their protein-coding region with IE1/IE2, their transcription start sites and exon(s) were latency associated.

Antiviral agents active against human herpesviruses HHV-6, HHV-7 and HHV-8

A series of antiviral compounds were examined for their activity against human herpesvirus type 6 (HHV-6), type 7 (HHV-7) and type 8 (HHV-8). They were selected either because they are already approved for clinical use in the treatment of herpesvirus infections (acyclovir, valaciclovir, penciclovir, famciclovir, ganciclovir, brivudin, foscarnet and cidofovir) or have demonstrated marked activity against herpesviruses (lobucavir, H2G, A-5021, D/L-cyclohexenyl G and S2242). In view of their host cell specificity, different cells and assays had to be used for determining antiviral activity against these three viruses. The most potent compounds with the highest antiviral selectivity index were: (i) for HHV-6; foscarnet, S2242, A-5021 and cidofovir; (ii) for HHV-7; S2242, cidofovir and foscarnet; and (iii) for HHV-8; S2242, cidofovir and ganciclovir. As mycophenolic acid has been shown to enhance significantly the activity of acyclic guanosine analogues (such as acyclovir, penciclovir and ganciclovir) in vitro against HSV-1, HSV-2, VZV and HCMV, it would seem worth evaluating whether mycophenolic acid also potentiates the activity of these acyclic guanosine analogues against HHV-6, -7 and -8.

Productive infection of primary macrophages with human herpesvirus 7

Here we demonstrate replication of human herpesvirus 7 (HHV-7), a T-lymphotropic virus, in macrophages. Productive replication was lost after 2 weeks, but HHV-7 DNA was detected up to 1 month after infection. Thus, macrophages become infected by HHV-7 and might play an important role as a viral reservoir, as has been demonstrated for human immunodeficiency virus type 1.

Activation of Kaposi's sarcoma-associated herpesvirus (human herpesvirus 8) lytic replication by human cytomegalovirus

The majority of Kaposi's sarcoma-associated herpesvirus (KSHV)-infected cells identified in vivo contain latent KSHV, with lytic replication in only a few percent of cells, as is the case for the cells of Kaposi's sarcoma (KS) lesions. Factors that influence KSHV latent or lytic replication are not well defined. Because persons with KS are often immunosuppressed and susceptible to many infectious agents, including human cytomegalovirus (HCMV), we have investigated the potential for HCMV to influence the replication of KSHV. Important to this work was the construction of a recombinant KSHV, rKSHV.152, expressing the green fluorescent protein (GFP) and neo (conferring resistance to G418). The expression of GFP was a marker of KSHV infection in cells of both epithelial and endothelial origin. The rKSHV.152 virus was used to establish cells, including human fibroblasts (HF), containing only latent KSHV, as demonstrated by latency-associated nuclear antigen expression and Gardella gel analysis. HCMV infection of KSHV latently infected HF activated KSHV lytic replication with the production of infectious KSHV. Dual-color immunofluorescence detected both the KSHV lytic open reading frame 59 protein and the HCMV glycoprotein B in coinfected cells, and UV-inactivated HCMV did not activate the production of infectious KSHV-GFP. In addition, HCMV coinfection increased the production of KSHV from endothelial cells and activated lytic cycle gene expression in keratinocytes. These data demonstrate that HCMV can activate KSHV lytic replication and suggest that HCMV could influence KSHV pathogenesis.

Lymphomatoid papulosis and human herpesviruses--A PCR-based evaluation for the presence of human herpesvirus 6, 7 and 8 related herpesviruses

BACKGROUND

Lymphomatoid papulosis (LyP) is a chronic, recurrent lymphoproliferative disorder of the skin that belongs to the group of primary cutaneous CD30-positive T-cell lymphomas. Ultrastructural and clinical features of LyP suggest that it has a viral etiology. Human herpesviruses have been proposed as causative cofactors for LyP because of their oncogenic potential and their association with other lymphomas.

METHODS

LyP skin lesions and a LyP-derived cell line were examined for the presence of the recently discovered oncogenic human herpesvirus 8 (HHV-8) and the two T-lymphotropic human herpesviruses 6 and 7 (HHV-6 and HHV-7) by nested polymerase chain reaction (PCR) using virus-specific oligonucleotide primers. Furthermore, a recently described method involving degenerate PCR primers was applied to detect highly conserved DNA sequences shared by a variety of herpesviruses, especially oncogenic gamma-herpesviruses, in an attempt to identify a yet undiscovered herpesvirus associated with LyP.

RESULTS

HHV-6 and 8 could not be found in 26 archival and 11 snap-frozen LyP lesions and a LyP tumor cell line. HHV-7 DNA sequences were detected in 14% (5 of 37) of LyP samples. HHV-6 was found in 23% (3 of 13) and HHV-7 in 8% (1 of 13) of normal skin samples from healthy individuals, respectively. Using degenerate PCR primers to amplify the highly conserved polymerase region of herpesviruses, no DNA sequences related to human herpesviruses could be detected.

CONCLUSIONS

LyP is not associated with HHV-6, HHV-7 and HHV-8. In addition, the studies using degenerate PCR primers do not indicate the presence of a previously undescribed human herpesvirus in LyP.

Increased expression of human herpesvirus 7 in lymphoid organs of AIDS patients

BACKGROUND

Human herpesvirus 7 (HHV-7) interferes reciprocally with the human immunodeficiency virus (HIV) in CD4 T lymphocytes, as infection with HIV results in a down modulation of the CD4 molecule and inhibition of replication of HHV-7, and vice versa. Correlations between HHV-7 and HIV at the organ level have not been studied in detail.

OBJECTIVE

To study the presence and cellular distribution of HHV-7 in lymphoid organs, i.e. lymph nodes (LNs) and spleen in AIDS patients and HIV-seronegative individuals.

STUDY DESIGN

Cross-sectional study. The detection of HHV-7 specific antigen pp85, the 85 kDa encoded tegument phosphoprotein by U14 gene, was performed by immunohistochemistry (IHC) with a well characterized monoclonal antibody (mAb 5E1) to pp85. Nested polymerase chain reaction (PCR) was applied to detect HHV-7 specific DNA sequences.

RESULTS

Cells infected with HHV-7 were detected in five of seven LNs from AIDS patients and in one of five LNs from HIV-seronegative patients. The infected cells were mainly macrophages. In samples from HIV-seropositive patients, a significantly higher number of HHV-7 infected cells could be observed than in specimens from HIV-seronegative patients. Neither the antigen nor DNA sequences of HHV-7 could be detected in spleen tissue from HIV-seronegative and AIDS patients.

CONCLUSIONS

The data indicate that HHV-7 undergoes a higher extent of reactivation from latency and/or of replication under immunosuppression due to HIV-infection, similar to the other beta-herpesviruses HHV-6 and human cytomegalovirus (HCMV). The data further suggest that LNs, but not the spleen, may be a site of latency and consequently of reactivation of HHV-7 in AIDS patients.

RANTES binding and down-regulation by a novel human herpesvirus-6 beta chemokine receptor

The human herpesvirus 6 (HHV-6) U51 gene defines a new family of betaherpesvirus-specific genes encoding multiple transmembrane glycoproteins with similarity to G protein-coupled receptors, in particular, human chemokine receptors. These are distinct from the HHV-6 U12 and HCMV US28 family. In vitro transcription and translation as well as transient cellular expression of U51 showed properties of a multiple transmembrane protein with a 30-kDa monomer as well as high m.w. aggregates or oligomers. Transient cellularly expressed U51 also appeared to form dimeric intermediates. Despite having only limited sequence similarity to chemokine receptors, U51 stably expressed in cell lines showed specific binding of the CC chemokine RANTES and competitive binding with other beta chemokines, such as eotaxin; monocyte chemoattractant protein 1, 3, and 4; as well as the HHV-8 chemokine vMIPII. In epithelial cells already secreting RANTES, U51 expression resulted in specific transcriptional down-regulation. This correlated with reduced secretion of RANTES protein into the culture supernatants. Regulation of RANTES levels may alter selective recruitment of circulating inflammatory cells that the virus can infect and thus could mediate the systemic spread of the virus from initial sites of infection in epithelia. Alternatively, chemokine regulation could modulate a protective inflammatory response to aid the spread of virus by immune evasion. Such mimicry, by viral proteins, of host receptors leading to down-regulation of chemokine expression is a novel immunomodulatory mechanism.

Human herpesvirus 8: is it a tumor virus?

Human herpesvirus 8 (HHV-8), also termed Kaposi's sarcoma-associated herpesvirus, was identified in Kaposi's sarcoma (KS) biopsy specimens in 1994. The epidemiological data available to date indicate a strong association of HHV-8 with KS. It appears that HHV-8 is necessary for KS development. HHV-8 DNA is invariably found in all epidemiological forms of KS and primary effusion lymphomas. In contrast, HHV-8 DNA is rarely found in various tumor and nontumor tissues from patient groups not at risk of KS. Although current serology does not allow us to assess the HHV-8 prevalence in the general population, high titers of HHV-8 antibodies are almost exclusively found in KS risk groups. In addition, HHV-8 seroconversion has been shown to precede KS development. The mechanisms and genes involved in HHV-8 pathogenesis are less clear. HHV-8 belongs to a family of transforming viruses, and several candidate oncogenes have been identified by using rodent fibroblast transformation assays. However, expression of most of these genes could not be shown in latently infected tumor cells. As the HHV-8 genome encodes several cytokines and cytokine receptor homologues, HHV-8 may also promote KS pathogenesis through paraendocrine mechanisms.

Human herpesvirus 7

Human herpesvirus 7, reported in 1990 is a lymphotropic member of the betaherpesvirus subfamily of herpesviruses. The virus is highly seroprevalent, primary infection usually occurs during childhood, and it has been associated with cases of exanthem subitum, pityriasis rosea, neurological manifestations and transplant complications. The latter two may warrant antiviral intervention, in vitro studies have shown that HHV-7 is susceptible to several nucleoside phosphonate compounds. In vitro, the virus has approximately a 5 day growth cycle in cultured lymphocytes; in vivo, latency is established in peripheral blood T-cells and a persistent infection is established in salivary gland tissue from which infectious virus is constitutively shed in saliva. The HHV-7 genome is approximately 145 kb and encodes at least 84 different proteins. Studies characterising HHV-7 gene products and the required interactions between viral and cellular genes necessary for virus replication, persistence and latency are in their infancy. HHV-7 infection has a variety of effects on host cells including upregulation of interleukin 15 and down-modulation of the cell surface molecule CD4; the latter serves as the cellular membrane receptor for HHV-7. Since HIV also infects T-cells via the CD4 molecule, the interactions of these viruses within T-cells during the course of AIDS are important areas of investigation.

Penile intraepithelial neoplasia overlying Kaposi's sarcoma lesions: role of viral synergy?

Several viral agents have been detected in the lesional tissue of Kaposi's sarcoma (KS). Their precise oncogenic role remains to be determined. A 32-year-old heterosexual man with acquired immunodeficiency syndrome (AIDS) who had penile lesions of KS with overlying epithelial changes characteristic of intraepithelial neoplasia associated with concurrent infection by human papillomavirus (HPV) and human herpesvirus 8 (HHV-8) is reported. The absence of viral DNA from uninvolved skin suggests that this coinfection is more than coincidental and may involve synergy between these viruses, as has already been suggested for HPV and herpes simplex 2 virus.

The role of HHV-8 in Kaposi's sarcoma

The epidemiology of Kaposi's sarcoma (KS) amongst North American and Northern European patients with AIDS suggests that an infectious agent other than HIV is involved in its pathogenesis. Several lines of evidence indicate that human herpesvirus 8 (HHV-8), also termed Kaposi's sarcoma associated herpesvirus, is the sought after agent. DNA of HHV-8 is invariably found in all forms of KS where the virus is present in the KS spindle cell. In contrast, HHV-8 DNA is not regularly detected in most other malignancies. Antibodies against HHV-8 are more frequently found in groups at risk of KS, and HHV-8 seroconversion precedes KS development. Several HHV-8 genes have been identified that exhibit transforming potential in cell culture systems. In addition, the virus encodes and induces several cytokines and angiogenic factors. This is of particular interest as models of KS pathogenesis developed before the discovery of HHV-8 emphasized the importance of inflammatory cytokines. Although the expression pattern of viral genes in KS is not certain yet, it appears likely that the pathogenetic role of HHV-8 in KS may be rather complex and differs from other virus-induced malignancies. 1999 Academic Press.

Human herpesvirus 6 infects dendritic cells and suppresses human immunodeficiency virus type 1 replication in coinfected cultures

Human herpesvirus 6 (HHV-6) has been implicated as a cofactor in the progressive loss of CD4(+) T cells observed in AIDS patients. Because dendritic cells (DC) play an important role in the immunopathogenesis of human immunodeficiency virus (HIV) disease, we studied the infection of DC by HHV-6 and coinfection of DC by HHV-6 and HIV. Purified immature DC (derived from adherent peripheral blood mononuclear cells in the presence of granulocyte-macrophage colony-stimulating factor and interleukin-4) could be infected with HHV-6, as determined by PCR analyses, intracellular monoclonal antibody staining, and presence of virus in culture supernatants. However, HHV-6-infected DC demonstrated neither cytopathic changes nor functional defects. Interestingly, HHV-6 markedly suppressed HIV replication and syncytium formation in coinfected DC cultures. This HHV-6-mediated anti-HIV effect was DC specific, occurred when HHV-6 was added either before or after HIV, and was not due to decreased surface expression or function of CD4, CXCR4, or CCR5. Conversely, HIV had no demonstrable effect on HHV-6 replication. These findings suggest that HHV-6 may protect DC from HIV-induced cytopathicity in AIDS patients. We also demonstrate that interactions between HIV and herpesviruses are complex and that the observable outcome of dual infection is dependent on the target cell type.

Trafficking to the plasma membrane of the seven-transmembrane protein encoded by human herpesvirus 6 U51 gene involves a cell-specific function present in T lymphocytes

The sequence of human herpesvirus 6 (HHV-6) U51 open reading frame predicts a protein of 301 amino acid residues with seven transmembrane domains. To identify and characterize U51, we derived antipeptide polyclonal antibodies and developed a transient expression assay. We ascertained that U51 was synthesized in cord blood mononuclear cells infected with either variant A- or variant B-HHV-6 and was transported to the surface of productively infected cells. When synthesized in transient expression systems, U51 intracellular trafficking was regulated in a cell-type-dependent fashion. In human monolayer HEK-293 and 143tk- cells, U51 accumulated predominantly in the endoplasmic reticulum and failed to be transported to the cell surface. In contrast, in T-lymphocytic cell lines J-Jhan, Molt-3, and Jurkat, U51 was successfully transported to the plasma membrane. We infer that transport of U51 to the cell surface requires a cell-specific function present in activated T lymphocytes and T-cell lines.

Human herpesvirus 6: An emerging pathogen

Infections with human herpesvirus 6 (HHV-6), a beta-herpesvirus of which two variant groups (A and B) are recognized, is very common, approaching 100% in seroprevalence. Primary infection with HHV-6B causes roseola infantum or exanthem subitum, a common childhood disease that resolves spontaneously. After primary infection, the virus replicates in the salivary glands and is shed in saliva, the recognized route of transmission for variant B strains; it remains latent in lymphocytes and monocytes and persists at low levels in cells and tissues. Not usually associated with disease in the immunocompetent, HHV-6 infection is a major cause of opportunistic viral infections in the immunosuppressed, typically AIDS patients and transplant recipients, in whom HHV-6 infection/reactivation may culminate in rejection of transplanted organs and death. Other opportunistic viruses, human cytomegalovirus and HHV-7, also infect or reactivate in persons at risk. Another disease whose pathogenesis may be correlated with HHV-6 is multiple sclerosis. Data in favor of and against the correlation are discussed.

Propagation and characterization of human herpesvirus-7 (HHV-7) isolates in a continuous T-lymphoblastoid cell line (SupT1)

After initial culture of HHV-7 in PHA-stimulated human cord blood mononuclear cells (HCBMC), six HHV-7 isolates were propagated successfully in an immature continuous T-lymphoblastoid cell line SupT1. All six isolates infected efficiently the SupT1 cells, and the infected cells became grossly enlarged and multinucleated 7-21 days post-infection. Various stages of HHV-7 morphogenesis were detected. Cell-free supernatants from HHV-7-infected SupT1 cells were infectious to HCBMC as well as to SupT1 cells. The HHV-7-infected SupT1 and HCBMC cell lysates contained more infectious virus than the centrifuged cell culture fluid supernates from the same culture. The HHV-7 isolates H7-2, H7-3, JHC, and JB, concentrated 500 times, had average infectivity titers of 10(3.0) TCID50/ml while strains H7-4 and KHR titered approximately 1-2 logs higher. When all six HHV-7 isolates were propagated in SupT1 and culture fluid supernatants were examined 14-21 days post-infection by negative stain electron microscopy they contained an average of 1.9 x 10(9) virus particles/liter. IFA and ELISA, using HHV-7/SupT1 cell lysate as an antigen, seem to correlate well in detecting high and low HHV-7 antibody in sera from chronic fatigue patients and healthy donors as controls. HHV-7 from SupT1 cell culture was free of HHV-6 and other human herpesviruses as tested by PCR, and the HHV-7 PCR signal was still strong when the viral preparation was diluted to 4.82 x 10(2) genome copies. Since HCBMC are expensive to obtain and available in only small amounts, it is difficult to obtain large quantities of HHV-7 antigen. On the other hand, the SupT1 cell is an excellent source to produce consistently sufficient quantities of HHV-7 for purification studies, development of immunodiagnostics, in vivo infectivity studies, evaluation of antiviral drugs, and molecular biological studies.