Prevalence of human herpesvirus 8 infection measured by antibodies to a latent nuclear antigen in patients with various dermatologic diseases

A role for the internal repeat of the Kaposi's sarcoma-associated herpesvirus latent nuclear antigen in the persistence of an episomal viral genome

The latent nuclear antigen (LANA) of Kaposi's sarcoma-associated herpesvirus (KSHV) is required for the replication and partitioning of latent viral genomes. It contains an extended internal repeat (IR) region whose function is only incompletely understood. We constructed KSHV genomes lacking either LANA (KSHV-ΔLANA) or the IR region of LANA (KSHV-LANAΔ329-931). Although still capable of replicating a plasmid containing a latent origin of replication, LANAΔ329-931 does not support the establishment of stable cell lines containing a KSHV genome. These findings suggest a role for the LANA IR in KSHV episomal maintenance without its being required for replication.

Seroreactivity to Kaposi's sarcoma-associated herpesvirus (human herpesvirus 8) latent nuclear antigen in AIDS-associated Kaposi's sarcoma patients depends on CD4+ T-cell count

In AIDS/Kaposi's sarcoma (KS) patients, the sensitivity of immunofluorescence assays for detecting antibodies against latent nuclear antigen ranges from 52% to 93%. However, in classic and African KS, sensitivities above 90% have been reported systematically. This study evaluates whether CD4+ T-cell count affects seroreactivity to KSHV LANA and to lytic antigens in AIDS/KS patients. Kaposi's sarcoma-associated herpesvirus (KSHV) latent (IFA-LANA) and lytic (IFA-Lytic and ORF65/K8.1 EIA) antibodies were screened in 184 consecutive samples taken from 36 AIDS/KS patients grouped according to their CD4+ counts as follows: <100 (group A), 100-300 (group B), and >300 (group C) cells/mm(3). At enrollment, the immunofluorescence assay for the detection of antibodies against latent nuclear antigen (IFA-LANA) was positive in 3/11(27.2%) group A patients, in 10/11 (90.9%) group B patients, and in 14/14 (100%) group C patients (P < 0.01). Seropositivity to lytic antigens did not differ according to CD4+ T-cell count. Considering IFA-Lytic and ORF65/K8.1 EIA, seropositivity for lytic antigens was 100% in all three patient groups. In patients whose CD4+ count improved during follow-up, IFA-LANA seroconversion occurred; unstable counts resulted in a decrease in LANA antibody titers while the persistence of high counts resulted in unchanged, elevated antibody titers. In conclusion, LANA seroreactivity in AIDS/KS patients, as assessed by an immunofluorescence assay, depends on CD4+ T-cell count, rendering this evaluation important in the interpretation of seroepidemiological studies of KSHV infection in AIDS patients. To evaluate future serological tests based on latency-associated antigens, the selection of sera from KS patients with CD4+ cell count >300 cells/mm(3) as a positive gold standard is recommended.

Functional characterization of the M-type K15-encoded membrane protein of Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV) or human herpesvirus 8 is the causative agent of Kaposi's sarcoma, primary effusion lymphoma and the plasma-cell variant of multicentric Castleman's disease. Its alternatively spliced K15 gene encodes several membrane proteins with varying numbers of transmembrane domains. Two highly diverged alleles of the K15 gene, termed predominant (P) and minor (M), exist and share only 33 % amino acid identity with one another, but retain conserved putative src homology (SH) 2- and SH3-binding motifs. K15-M is thought to have entered the KSHV genome as the result of recombination with a related gamma(2)-herpesvirus. The more common K15-P allele has been shown to activate the mitogen-activated protein kinases Erk2 and JNK1 and the nuclear factor kappaB (NF-kappaB) pathway. To explore possible functional differences between K15-P and K15-M that might have influenced their spread in the KSHV population, here, the ability of the M form of K15 to activate these pathways was investigated. Similarly to K15-P, K15-M induces the activation of the Erk2 and JNK1 kinases, the NF-kappaB transcription factor and the expression of a similar range of cellular inflammatory genes, as assessed by gene-expression microarray studies and reporter assays. In epithelial cells, the activation of most K15-M target genes is impaired by mutagenesis of Y(490) in its SH2-binding motif Y(490)EEV, although this motif appears less important in endothelial cells. Therefore, K15-M and K15-P can trigger similar intracellular signalling pathways, despite their extensive sequence divergence.

Latency-associated nuclear antigen (LANA) of Kaposi's sarcoma-associated herpesvirus interacts with origin recognition complexes at the LANA binding sequence within the terminal repeats

Kaposi's sarcoma-associated herpesvirus (KSHV) DNA persists in latently infected cells as an episome via tethering to the host chromosomes. The latency-associated nuclear antigen (LANA) of KSHV binds to the cis-acting elements in the terminal repeat (TR) region of the genome through its carboxy terminus. Previous studies have demonstrated that LANA is important for episome maintenance and replication of the TR-containing plasmids. Here we report that LANA associates with origin recognition complexes (ORCs) when bound to its 17-bp LANA binding cognate sequence (LBS). Chromatin immunoprecipitation of multiple regions across the entire genome from two KSHV-infected cell lines, BC-3 and BCBL-1, revealed that the ORCs predominantly associated with the chromatin structure at the TR as well as two regions within the long unique region of the genome. Coimmunoprecipitation of ORCs with LANA-specific antibodies shows that ORCs can bind and form complexes with LANA in cells. This association was further supported by in vitro binding studies which showed that ORCs associate with LANA predominantly through the carboxy-terminal DNA binding region. KSHV-positive BC-3 and BCBL-1 cells arrested in G(1)/S phase showed colocalization of LANA with ORCs. Furthermore, replication of The TR-containing plasmid required both the N- and C termini of LANA in 293 and DG75 cells. Interestingly, our studies did not detect cellular ORCs associated with packaged viral DNA as an analysis of purified virions did not reveal the presence of ORCs, minichromosome maintenance proteins, or LANA.

Kaposi's sarcoma-associated herpesvirus: clinical, diagnostic, and epidemiological aspects

Kaposi's sarcoma-associated herpesvirus (KSHI) is one of the few viruses proven to be associated with tumorigenesis in humans. Its causal association with all clinical and epidemiological variants of Kaposi's sarcoma (KS) is well established. KSHV is also involved in the pathogenesis of primary effusion lymphoma (PEL) and a subset of multicentric Castleman's disease (MCD). Possible associations of KSHV with other clinical settings have been extensively examined. The findings from several of these studies are contradictory and are yet to be resolved. Concentrated effort over the last decade, since the initial discovery of KSHV, led to the development of several experimental systems that resulted in a better comprehension of the biological characteristics of KSHV and set the stage for the understanding of mechainisms by which diseases are induced by the virus. The development of molecular, histological, and serological tools for KSHV diagnosis allowed researchers to track the transmission and to study the epidemiology of KSHV. These assays have been applied, in particular in ambiguous cases, in order to confirm clinically and pathologically based diagnoses. Here, we review the advances in the clinical, experimental, diagnostic, and epidemiological research of KSHV.

Higher prevalence of human herpesvirus 8 DNA sequence and specific IgG antibodies in patients with pemphigus in China

BACKGROUND

Environmental factors, including virus infection, may play a role in the onset and/or development of pemphigus. However, it is controversial whether human herpesvirus (HHV)-8 is involved in pathogenesis of pemphigus.

OBJECTIVE

The possible association of pemphigus with HHV-8 was investigated.

METHODS

A total of 36 lesional skin and 13 peripheral blood mononuclear cell specimens from 58 patients with pemphigus, and 18 normal skin and 230 peripheral blood mononuclear cell specimens from healthy individuals, were tested for HHV-8 DNA sequence by a nested polymerase chain reaction assay. In all, 29 sera from the patients and 109 sera from healthy individuals were tested for HHV-8-specific IgG antibodies by enzyme-linked immunosorbent assays using HHV-8-specific oligopeptides as antigens.

RESULTS

Prevalence of both HHV-8 DNA sequence (36.1% and 30.8% in lesional skin and in peripheral blood mononuclear cells, respectively) and HHV-8-specific IgG antibodies (34.5%) for patients with pemphigus was statistically higher than that of control subjects (<8% in both assays). There was no significant difference in HHV-8 prevalence among different types of pemphigus.

CONCLUSION

HHV-8 infection might be a contributing factor in the development of pemphigus.

Human herpesvirus 8 (HHV-8) and the etiopathogenesis of Kaposi's sarcoma

OBJECTIVE

To review the current literature on human herpesvirus 8 with particular attention to the aspects related to the etiopathogenesis of Kaposi's sarcoma.

MATERIALS AND METHODS

The authors searched original research and review articles on specific aspects of human herpesvirus 8 infection, including virology, epidemiology, transmission, diagnosis, natural history, therapy, and Kaposi's sarcoma etiopathogenesis. The relevant material was evaluated and reviewed.

RESULTS

Human herpesvirus 8 is a recently discovered DNA virus that is present throughout the world but with major geographic variation. In the Western world, the virus, transmitted mainly by means of sexual contact, is strongly associated with Kaposi's sarcoma and body cavity-based lymphoma and more controversially with multiple myeloma and other non-proliferative disorders. There is no specific effective treatment, but HIV protease inhibitors may play an indirect role in the clearance of human herpesvirus 8 DNA from peripheral blood mononuclear cells of HIV-infected patients. Human herpesvirus 8 DNA is present in saliva, but there are as yet no documented cases of nosocomial transmission to health care workers. The prevalence of human herpesvirus 8 among health care workers is probably similar to that in the general population.

CONCLUSION

Human herpesvirus 8 appears to be, at least in Western Europe and United States, restricted to a population at risk of developing Kaposi's sarcoma. Human herpesvirus 8 certainly has the means to overcome cellular control and immune responses and thus predispose carriers to malignancy, particularly Kaposi's sarcoma. The wide diffusion of Human herpesvirus 8 in classic Kaposi's sarcoma areas appears to represent an important factor in the high incidence of the disease. However, additional co-factors are likely to play a role in the development of Kaposi's sarcoma.

Kaposi's sarcoma and other manifestations of human herpesvirus 8

Kaposi's sarcoma (KS) was described by Moritz Kaposi in 1872 and was known for an entire century as a rare disorder of older men usually of Eastern European, Mediterranean, and/or Jewish origin. In the early 1980s, the prevalence of KS began to increase dramatically and soon became the most common malignancy in patients with AIDS, especially those who were male homosexuals. In 1994, a new human herpesvirus (HHV) was found to be present in almost 100% of KS lesions. This virus was found to be a gammaherpesvirus, closely related to Epstein-Barr virus, and was designated HHV-8. Subsequently, HHV-8 DNA was found in almost all specimens of classic KS, endemic KS, and iatrogenic KS, as well as epidemic KS (ie, AIDS KS). It is now believed that HHV-8 is necessary, but not sufficient, to cause KS and that other factors such as immunosuppression play a major role. The use of highly active antiretroviral therapy (HAART) since 1996 has markedly reduced the prevalence of AIDS KS in western countries, but because 99% of the 40 million patients with AIDS in the world cannot afford HAART, KS is still a very common problem. Primary effusion lymphoma and multicentric Castleman's disease are also thought to be due to HHV-8. Although HHV-8 DNA has been described in a number of other cutaneous disorders, there is little evidence that HHV-8 is of etiologic significance in these diseases. The mechanism by which HHV-8 causes KS, primary effusion lymphoma, and multicentric Castleman's disease is not well understood but is thought to involve a number of molecular events, the study of which should further our understanding of viral oncology. (J Am Acad Dermatol 2002;47:641-55.)

LEARNING OBJECTIVE

At the completion of this learning activity, participants should be familiar with Kaposi's sarcoma and other manifestations of human herpesvirus 8.

Spectrum of Kaposi's sarcoma-associated herpesvirus, or human herpesvirus 8, diseases

Human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus (KSHV), discovered in 1994, is a human rhadinovirus (gamma-2 herpesvirus). Unlike other human herpesviruses (herpes simplex virus, Epstein-Barr virus, varicella-zoster virus, cytomegalovirus, HHV-6, and HHV-7), it is not widespread in the general population and has many unique proteins. HHV-8 is strongly associated with all subtypes of Kaposi's sarcoma (KS), multicentric Castleman's disease, and a rare form of B-cell lymphoma, primary effusion lymphoma. In addition, HHV-8 DNA sequences have been found in association with other diseases, but the role of the virus in these diseases is largely unconfirmed and remains controversial. The seroprevalence of HHV-8, based on detection of latent and lytic proteins, is 2 to 5% in healthy donors except in certain geographic areas where the virus is endemic, 80 to 95% in classic KS patients, and 40 to 50% in HIV-1 patients without KS. This virus can be transmitted both sexually and through body fluids (e.g., saliva and blood). HHV-8 is a transforming virus, as evidenced by its presence in human malignancies, by the in vitro transforming properties of several of its viral genes, and by its ability to transform some primary cells in culture. It is not, however, sufficient for transformation, and other cofactors such as immunosuppressive cytokines are involved in the development of HHV-8-associated malignancies. In this article, we review the biology, molecular virology, epidemiology, transmission, detection methods, pathogenesis, and antiviral therapy of this newly discovered human herpesvirus.

Human herpesvirus 8 and oral health care: an update

OBJECTIVE

The purpose of this report was to review the current literature on human herpesvirus 8 (HHV-8) with particular attention to the aspects of interest for dental health care workers.

MATERIAL AND METHODS

The authors searched original research and review articles on specific aspects of HHV-8 infection, including virology, epidemiology, transmission, diagnosis, natural history, therapy, and oral aspects. The relevant material was evaluated and reviewed.

RESULTS

HHV-8 is a recently discovered DNA virus that is present throughout the world but with major geographic variation. In the Western world, the virus, transmitted mainly by means of sexual contact, is strongly associated with Kaposi's sarcoma and body cavity-based lymphoma and more controversially with multiple myeloma and non-neoplastic disorders. There is no specific effective treatment, but human immunodeficiency virus protease inhibitors may play an indirect role in the clearance of HHV-8 DNA from peripheral blood mononuclear cells of patients infected with human immunodeficiency virus. HHV-8 DNA is present in saliva, but as yet, there are no documented instances of nosocomial transmission to health care workers. The prevalence of HHV-8 among dental health care workers is probably similar to that in the general population.

CONCLUSION

HHV-8 does not appear to be ubiquitous in most populations, particularly in western Europe and the United States, where it may be restricted to a population at risk of having Kaposi's sarcoma develop (men infected with human immunodeficiency virus and patients who are iatrogenically immunosuppressed). Most serologic studies suggest a global HHV-8 seroprevalence of 2% to 10% and show that the virus may be under immunologic control in people who are healthy but infected with HHV-8. Also, HHV-8 certainly has the means to overcome cellular control and immune responses and thus predispose to malignancy. To date, there are no data to suggest that health care staff members are at particular risk of HHV-8 acquisition through occupational routes.

Selected cutaneous vascular neoplasms. A review

This article reviews the pathology of benign, borderline, and malignant vascular neoplasms of the skin. The classification of vascular lesions of childhood is presented. Defined variants of hemangioma (including sinusoidal, microvenular, glomeruloid, epithelioid, and targetoid hemosideric hemangioma, as well as acquired tufted hemangioma and angiofibroma) are discussed. Borderline hemangioendotheliomas are classified. Kaposi sarcoma is reviewed with an update on the role of human herpesvirus type 8 in its pathogenesis. Angiosarcoma and acquired progressive lymph-angioma are also discussed.