Detection and Titration of Human Herpesvirus-8–Specific Antibodies in Sera From Blood Donors, Acquired Immunodeficiency Syndrome Patients, and Kaposi's Sarcoma Patients Using a Whole Virus Enzyme-Linked Immunosorbent Assay

Antibody profiling and predictive modeling discriminate between Kaposi sarcoma and asymptomatic KSHV infection

Protein-level immunodominance patterns against Kaposi sarcoma-associated herpesvirus (KSHV), the aetiologic agent of Kaposi sarcoma (KS), have been revealed from serological probing of whole protein arrays, however, the epitopes that underlie these patterns have not been defined. We recently demonstrated the utility of phage display in high-resolution linear epitope mapping of the KSHV latency-associated nuclear antigen (LANA/ORF73). Here, a VirScan phage immunoprecipitation and sequencing approach, employing a library of 1,988 KSHV proteome-derived peptides, was used to quantify the breadth and magnitude of responses of 59 sub-Saharan African KS patients and 22 KSHV-infected asymptomatic individuals (ASY), and ultimately to support an application of machine-learning-based predictive modeling using the peptide-level responses. Comparing anti-KSHV antibody repertoire revealed that magnitude, not breadth, increased in KS. The most targeted epitopes in both KS and ASY were in the immunodominant proteins, notably, K8.129-56 and ORF65140-168, in addition to LANA. Finally, using unbiased machine-learning-based predictive models, reactivity to a subset of 25 discriminative peptides was demonstrated to successfully classify KS patients from asymptomatic individuals. Our study provides the highest resolution mapping of antigenicity across the entire KSHV proteome to date, which is vital to discern mechanisms of viral pathogenesis, to define prognostic biomarkers, and to design effective vaccine and therapeutic strategies. Future studies will investigate the diagnostic, prognostic, and therapeutic potential of the 25 discriminative peptides.

Pathological Features of Kaposi's Sarcoma-Associated Herpesvirus Infection

Kaposi's sarcoma-associated herpesvirus (KSHV, human herpesvirus 8, or HHV-8) was firstly discovered in Kaposi's sarcoma tissue derived from patients with acquired immune deficiency syndrome. KSHV infection is associated with malignancies and certain inflammatory conditions. In addition to Kaposi's sarcoma, KSHV has been detected in primary effusion lymphoma, KSHV-associated lymphoma, and some cases of multicentric Castleman disease (MCD). Recently, KSHV inflammatory cytokine syndrome (KICS) was also defined as a KSHV-associated disease. In KSHV-associated malignancies, such as Kaposi's sarcoma and lymphoma, KSHV latently infects almost all tumor cells, and lytic proteins are rarely expressed. A high titer of KSHV is detected in the sera of patients with MCD and KICS, and the expression of lytic proteins such as ORF50, vIL-6, and vMIP-I and vMIP-II is frequently observed in the lesions of patients with these diseases. Immunohistochemistry of LANA-1 is an important diagnostic tool for KSHV infection. However, much of the pathogenesis of KSHV remains to be elucidated, especially regarding oncogenesis. Some viral proteins have been shown to have transforming activity in mammalian cells; however, these proteins are not expressed in latently KSHV-infected cells. KSHV encodes homologs of cellular proteins in its genome such as cyclin D, G-protein coupled protein, interleukin-6, and macrophage inflammatory protein-1 and -2. Molecular mimicry by these viral proteins may contribute to the establishment of microenvironments suitable for tumor growth. In this review, the virus pathogenesis is discussed based on pathological and experimental findings and clinical aspects.

Cross-sectional and longitudinal investigation of human herpesvirus 8 seroprevalence in HIV-1-infected individuals in Osaka, Japan

INTRODUCTION

High human herpesvirus 8 (HHV-8) seroprevalence has been reported in men who have sex with men (MSM) and are infected with HIV-1. However, it is unclear when they become infected with HHV-8. Thus, we conducted cross-sectional and longitudinal investigations of HHV-8 seroprevalence in HIV-1-infected individuals in Osaka, Japan.

PATIENTS AND METHODS

Plasma was collected from 121 individuals infected with HIV-1 and the anti-HHV-8 antibody titer was measured using an enzyme-linked immunosorbent assay with whole virus lysate. Subjects were classified into those with and without a past medical history of HHV-8-associated disease; the latter group was then classified into 3 subgroups based on the assumed route of HIV-1 infection: blood products, homosexual contact, and other routes. HHV-8 seroprevalence was compared among the groups and measured again approximately 3 years after the baseline measurement. The relationship between HHV-8 seropositivity and possible associated factors was also investigated.

RESULTS

All 15 subjects with HHV-8-associated disease were seropositive, and all 11 subjects in the blood product group were seronegative. In the MSM group, 25 (30%) of 79 subjects were HHV-8 seropositive and, in the non-MSM group, 1 (6%) of 16 subjects was (p < 0.0001). In the longitudinal investigation, seroconversion was observed in 10 (19%) of 52 subjects in the MSM group who were seronegative at baseline. A correlation was observed between seroconversion and symptomatic syphilis (p = 0.0432).

CONCLUSIONS

HHV-8 seropositivity and seroconversion rates were high in HIV-1-infected MSM, suggesting that, currently, HHV-8 is an epidemic pathogen in this population.

Conceptual Emergence of Human Herpesvirus 8 (Kaposi’s Sarcoma-associated Herpesvirus) as an Oral Herpesvirus

Recognition of the various clinico-epidemiologic forms of Kaposi’s sarcoma, a disease putatively caused by an infectious agent, did not provide ready clues as to how that agent might be transmitted, although fecal and sexual routes were implicated. Application of serologic and genome-detection assays, and cell-culture studies following the identification of human herpesvirus 8 as the causative agent now implicate that virus as one that is orally shed. While oral transmission of the virus might account for the viral endemicity in Africa and Mediterranean countries, why it is particularly prevalent among male homosexuals in the West remains more difficult to explain. Such explanation may be sought from behavioral studies into the role saliva plays in sexual interactions.

Healthy rabbits are susceptible to Epstein-Barr virus infection and infected cells proliferate in immunosuppressed animals

Background

Epstein-Barr virus (EBV) is an oncogenic virus implicated in the pathogenesis of several human malignancies. However, due to the lack of a suitable animal model, a number of fundamental questions pertaining to the biology of EBV remain poorly understood. Here, we explore the potential of rabbits as a model for EBV infection and investigate the impact of immunosuppression on viral proliferation and gene expression.

Methods

Six healthy New Zealand white rabbits were inoculated intravenously with EBV and blood samples collected prior to infection and for 7 weeks post-infection. Three weeks after the last blood collection, animals were immunosuppressed with daily intramuscular injections of cyclosporin A at doses of 20 mg/kg for 15 days and blood collected twice a week from each rabbit. The animals were subsequently sacrificed and tissues from all major organs were collected for subsequent analysis.

Results

Following intravenous inoculation, all 6 rabbits seroconverted with raised IgG and IgM titres to EBV, but viral DNA in peripheral blood mononuclear cells (PBMCs) could only be detected intermittently. Following immunosuppression however, EBV DNA could be readily detected in PBMCs from all 4 rabbits that survived the treatment. Quantitative PCR indicated an increase in EBV viral load in PBMCs as the duration of immunosuppression increased. At autopsy, splenomegaly was seen in 3/4 rabbits, but spleens from all 4 rabbit were EBV PCR positive. EBER-in situ hybridization and immunoshistochemistry revealed the presence of a large number of EBER-positive and LMP-1 positive lymphoblasts in the spleens of 3/4 rabbits. To a lesser extent, EBER-positive cells were also seen in the portal tract regions of the liver of these rabbits. Western blotting indicated that EBNA-1 and EBNA-2 were also expressed in the liver and spleen of infected animals.

Conclusion

EBV can infect healthy rabbits and the infected cells proliferate when the animals are immunocompromised. The infected cells expressed several EBV-latent gene products which are probably driving the proliferation, reminiscent of what is seen in immunocompromised individuals. Further work is required to explore the potential of rabbits as an animal model for studying EBV biology and tumorigenesis.

Seroprevalence of HHV-6 and HHV-8 among blood donors in Greece

Background

Herpes viruses infection transmitted through healthy but infected blood donors pose a danger to herpes-naive immunocompromised recipients. The risk of transfusion-related HHV-8 transmission is different in endemic and not endemic areas. HHV-6 and HHV-8 seroprevalence and viral load among blood donors have been reported from different countries. The aim of our study was to assess the seroprevalence of HHV-8 and HHV-6 in volunteer blood donors from Greece which is unknown.

Findings

Serum samples from 179 healthy blood donors were tested for the presence of IgG antibodies against HHV-6 and HHV-8 with ELISA. None of the 179 donors of Greek origin tested was positive for HHV-8. HHV-6 seropositivity was assessed in 160 blood donors’ samples and was found to be 78.75% (126/160). The HHV-6 seroprevalence did not differ either between males and females or among different decade age groups.

Conclusions

The fact, that no blood donor was positive for HHV-8 IgG antibodies indicates that the risk for transfusion related HHV-8 transmission in Greece, if any, is negligible and does not warrant broad testing for HHV-8. Definitely further studies are needed, in order to clarify the potential risk of HHV-6 transmission.

Higher levels of neutralizing antibodies against KSHV in KS patients compared to asymptomatic individuals from Zambia

Kaposi sarcoma-associated herpesvirus (KSHV) is the etiologic agent for Kaposi Sarcoma (KS), the most common cancer diagnosed in HIV- infected patients. The role of neutralizing antibodies in KS pathogenesis and in KSHV infected individuals is not clearly understood. The goal of this study was to investigate and compare the prevalence and titers of neutralizing antibodies in plasma samples from KS patients and KSHV infected asymptomatic individuals from Zambia, a KS endemic region in sub-Saharan Africa. Plasma samples (N = 267) consisting of KS patients (group 1) and asymptomatic individuals (group 2) were collected from Lusaka, Zambia. A flow cytometry based quantitative neutralization assay utilizing recombinant KSHV expressing GFP was used to detect KSHV neutralizing antibodies. Our results show that the overall prevalence of neutralizing antibodies in KS patients (group 1) was 66.7% which was significantly higher than the prevalence of 6.5% present in KSHV infected asymptomatic individuals (group 2). Total antibody titers as well as neutralizing antibodies titers were found to be significantly higher among KS patients. It is likely that higher neutralizing antibodies prevalence and titers in KS patients result from higher levels of antigenic stimulation over time. This study is first to compare prevalence and titers of neutralizing antibodies in participants with and without disease from a KSHV endemic region.

Seroprevalence of Human herpesvirus 8 (HHV-8) and incidence of Kaposi's sarcoma in Iran

Seroepidemiological surveys show that the prevalence of human herpesvirus 8 (HHV-8) infection mostly varies in various geographical areas and reflects the local incidence of classic and endemic KS, being widespread in sub-Saharan Africa and Mediterranean countries and uncommon in the USA and Northern Europe. In the Middle East only few populations, such as Ashkenazi and Sephardic groups in Israel, have been adequately evaluated for HHV-8 seroprevalence. Among Iranian population a striking higher seroprevalence of HHV8 has been reported among haemodialysis (16.9%), renal transplant recipients (25%) and HIV (45.7%) patients compared to blood donors (2%). Kaposi's sarcoma (KS) is the rarest cancer in Iran, with an annual age-standardized incidence varying from 0.10 to 0.17 per 100,000 in males and from 0.06 to 0.08 per 100,000 in females. KS, however, is one of the most important malignancies in Iranian renal transplanted patients affecting up to 2.4% of organ recipients. The epidemiology of HHV8 and KS in Iran needs further evaluation. While the high prevalence of HHV-8 antibodies in HIV positive and haemodialysis individuals may be attributed to high-risk sexual behavior and polytransfusions, respectively, unknown determinants may be responsible for high seroprevalence of HHV8 and high incidence of KS in solid organ recipients. A global survey on HHV8 seroprevalence in Iran is mandatory to define co-factors associated with HHV8 infection and KS risk in the general Iranian population and in specific patient groups.

Chronic humoral rejection of human kidney allografts associates with broad autoantibody responses

BACKGROUND

Chronic humoral rejection (CHR) is a major complication after kidney transplantation. The cause of CHR is currently unknown. Autoantibodies have often been reported in kidney transplant recipients alongside antidonor human leukocyte antigen antibodies. Yet, the lack of comprehensive studies has limited our understanding of this autoimmune component in the pathophysiology of CHR.

METHODS

By using a series of ELISA and immunocytochemistry assays, we assessed the development of autoantibodies in 25 kidney transplant recipients with CHR and 25 patients with stable graft function. We also compared the reactivity of five CHR and five non-CHR patient sera with 8027 recombinant human proteins using protein microarrays.

RESULTS

We observed that a majority of CHR patients, but not non-CHR control patients, had developed antibody responses to one or several autoantigens at the time of rejection. Protein microarray assays revealed a burst of autoimmunity at the time of CHR. Remarkably, microarray analysis showed minimal overlap between profiles, indicating that each CHR patient had developed autoantibodies to a unique set of antigenic targets.

CONCLUSION

The breadth of autoantibody responses, together with the absence of consensual targets, suggests that these antibody responses result from systemic B-cell deregulation.

Complete absence of KSHV/HHV-8 in posttransplant lymphoproliferative disorders: an immunohistochemical and molecular study of 52 cases

Posttransplant lymphoproliferative disorders (PTLDs), a heterogeneous group of monoclonal or polyclonal lesions, occur in immunosuppressed patients after solid organ or bone marrow transplantation. Although most PTLDs are Epstein-Barr virus (EBV)+ and seem to represent EBV-induced proliferations of monoclonal (or less often polyclonal) B, T, or plasma cells, a subset of PTLDs is EBV-. Because Kaposi sarcoma-associated herpesvirus/human herpesvirus 8 (KSHV/HHV-8) has been described in association with the development of hematolymphoid and nonhematolymphoid neoplasms in HIV+ patients, we investigated whether there is an association between KSHV/HHV-8 and PTLDs. Formalin-fixed, paraffin-embedded tissue from 52 confirmed PTLD cases were analyzed immunohistochemically for expression of KSHV/HHV-8 latent nuclear antigen (LNA)-1 protein and by polymerase chain reaction-hybridization analysis for the KSHV/HHV-8 genome. The PTLD subtypes included 12 with early lesions (1 plasmacytic hyperplasia and 11 infectious mononucleosis-like), 10 polymorphic, 23 monomorphic (5 Burkitt, 14 diffuse large B-cell lymphoma, 1 plasmacytoma, 1 multiple myeloma, and 2 T-cell), 1 Hodgkin lymphoma (HL), 5 HL-like lesions, and 1 unclassified or other. None of the 51 tested specimens showed expression of KSHV/HHV-8 LNA-1. Furthermore, all 46 specimens tested demonstrated complete absence of the KSHV/HHV-8 genome. Our data clearly indicated that KSHV/HHV-8 is not associated with PTLDs.

Development of an immunofluorescence assay using recombinant proteins expressed in insect cells to screen and confirm presence of human herpesvirus 8-specific antibodies

Human herpesvirus 8 (HHV-8), or Kaposi's sarcoma (KS)-associated herpesvirus, has been linked to all forms of KS. The results of most current serological assays for the detection of HHV-8-specific antibodies have low levels of concordance among themselves. To establish a sensitive and specific testing strategy that can be used to screen for HHV-8-specific antibodies, three HHV-8 proteins, ORF65, ORF73, and K8.1A, were expressed by using baculoviral vectors in insect cells and incorporated into a monoclonal antibody-enhanced immunofluorescence assay (mIFA) termed the Sf9 three-antigen mIFA. The results obtained by this mIFA were compared to those obtained by a standard mIFA with an HHV-8-infected B-cell line (BC3 mIFA). Test sera were obtained from patients diagnosed with KS, human immunodeficiency virus type 1-infected patients at high risk for HHV-8 infection, and healthy controls from a local blood bank. The combined use of both assays had a sensitivity of 94% and a specificity of 96%. The performance of these two assays when they were used together indicates that they may be useful for the reliable detection of HHV-8-specific immunoglobulin G antibodies in a population.

HIV-associated Kaposi sarcoma: pathogenic mechanisms

Kaposi sarcoma (KS) is a multicentric angioproliferative disorder characterized by spindle cell proliferation, neo-angiogenesis, inflammation, and edema. Human herpesvirus (HHV)-8, a gamma-herpesvirus, is a critical factor, but is not alone sufficient for the initiation of KS. Other cofactors such as human immunodeficiency virus (HIV), host-derived cytokines, chemokines, and growth factors are required for the development of KS. Whether HIV-associated KS is a reactive hyperplastic inflammatory lesion or a true neoplasm is still controversial. It is likely that HIV-associated KS begins as a reactive disorder that in some cases progresses to a monoclonal, an oligoclonal, and a polyclonal neoplasm.

Human herpesvirus 8 (HHV-8) infection in healthy urban employees from Greece: seroprevalence and associated factors

A cross-sectional study was carried out in healthy company employees from Greece with the aim of assessing the prevalence of human herpesvirus 8 (HHV-8) and identifying risk factors for this herpesviral infection. Serum samples obtained from 955 subjects were tested for antibodies to HHV-8 by the K8.1 enzyme-linked immunosorbent assay (ELISA). Associations between HHV-8 serostatus and potential risk factors were examined using t-test, chi square test, and multivariate logistic regression analysis. HHV-8 prevalence was 7.6% (95% confidence interval (CI): 6.0%, 9.5%) and it increased with age from 6.5% among <30 years old to 13.8% among > or =50 years old subjects (P = 0.006). HHV-8 seropositivity was independently associated with endoscopic examination (odds ratio (OR): 2.01; 95% CI: 1.09, 3.70; P = 0.026), HBsAg positivity (OR: 5.16; 95% CI: 2.02, 13.20; P = 0.001) and age (OR > or =50 years old vs. <50 years old: 2.09; 95% CI: 1.23, 3.52; P = 0.006). No statistically significant associations between HHV-8 positive status and gender, occupational status, surgery, transfusion, tattoos/body piercing, multiple sex partners, weakness/fatigue, HCV status were observed. HHV-8 is prevalent in Greece. The strong association between HBV infection and HHV-8 positive status supports the hypothesis of an association between these two viral infections. The association between HHV-8 seropositivity and endoscopic examination requires further investigation.

Human herpesvirus 8: serovprevalence and correlates in tumor patients from Xinjiang, China

Human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus, is etiologically associated with Kaposi's sarcoma and other lymphoproliferative diseases. Although HHV-8 prevalence exhibits considerable variation in different geographic regions and populations, the incidence of Kaposi's sarcoma appear to increase in areas with a high prevalence rate. In this study, an enzyme-linked immunosorbent assay based on mixed antigens of HHV-8 ORF(73), ORF(65), and K8.1 in the antigenic region was established and used to determine viral prevalence estimates and risk factors associated with HHV-8 infection. Of 482 tumor patients studied, the overall seropositivity of HHV-8 was 25.5%. Notably, Han people, who were immigrants or descendents of immigrants from inland of China, exhibited 26.4% seropositivity. This is similar to that observed in Uygur people, a local ethnic group with a high prevalence of HHV-8 infection and incidence of Kaposi's sarcoma. While there was no significant difference in patients with different tumors, HHV-8 seroprevalence was higher in individuals with malignant diseases. Logistic regression analysis suggests that the age is a risk factor associated with HHV-8 infection, with prevalence increasing from 12.5% under 20-27.5% above 50. These results suggest that unlike other parts of mainland of China, Xinjiang is an area with a high prevalence of HHV-8 infection.

Epidemiology of Epstein-Barr virus, cytomegalovirus, and Kaposi's sarcoma-associated herpesvirus infections in peripheral blood leukocytes revealed by a multiplex PCR assay

A multiplex polymerase chain reaction (PCR) has been developed for the simultaneous detection of Epstein-Barr virus (EBV), cytomegalovirus (CMV), and Kaposi's sarcoma-associated herpesvirus (KSHV) in a clinical sample. Primers of multiplex PCR were designed to amplify specific regions of the EBV EBNA1, CMV IE2, and KSHV LANA genes. This multiplex PCR assay was found to have detection sensitivities of 1-10 copies of purified viral DNA cloned into the plasmid. To assess diagnostic and pre-clinical applications with this method, we utilized KSHV-positive primary effusion lymphoma (PEL) cells, EBV-positive Burkitt's lymphoma cells, CMV-infected fibroblast cells, and clinically prepared peripheral blood leukocytes (PBLs) that had been infected with viruses. We found that this multiplex PCR assay has high sensitivity and specificity for simultaneous detection of EBV, CMV, and KSHV genomes in a single amplification from a clinical material. Using this multiplex PCR assay, we investigated the prevalence of EBV, CMV, and KSHV in PBL samples from normal Japanese randomly selected. KSHV, EBV, and CMV genomes were detected in samples from 2 (0.2%), 377 (39.5%), and 27 (2.8%) of the 953 blood donors, respectively. Interestingly, both EBV and CMV genomes were detected in samples from all KSHV-positive donors.

Comparative study of Kaposi's sarcoma-associated herpesvirus serological assays using clinically and serologically defined reference standards and latent class analysis

Accurate determination of infection with Kaposi's sarcoma-associated herpesvirus (KSHV) has been hindered by the lack of a "gold standard" for comparison of serological assays used to estimate KSHV prevalence in serosurveys conducted in different settings. We have evaluated the performance of five in-house (developed at University College London [UCL], United Kingdom, and at the virology laboratory of the Instituto de Medicine Tropical [IMT] in Sao Paulo, Brazil) and two commercial (ABI and DIAVIR) serological assays to detect antibodies to latency-associated nuclear antigen (LANA) and to lytic KSHV antigens. We used a variety of serum samples assembled to represent populations likely to be at high, intermediate, and low risk of KSHV infection in Brazil. Composite reference standard panels were prepared based on clinical and serological parameters, against which assay performances were assessed using conventional Bayesian statistics and latent class analysis (LCA). Against the clinical reference standard, in-house immunofluorescence assays to detect anti-LANA antibodies (IFA-LANA) produced at UCL and IMT had similar performances, with sensitivities of 61% (95% confidence interval [CI], 48% to 74%) and 72% (95% CI, 58% to 83%) and specificities of 99% (95% CI, 94% to 100%) and 100% (95% CI, 96% to 100%), respectively, and only the IMT IFA-LANA was included in LCA, together with the IMT IFA-lytic and four enzyme-linked immunosorbent assays (ELISAs). The LCA indicated that the IMT whole-virus ELISA performed best (sensitivity, 87% [95% CI, 81% to 91%]; and specificity, 100% [95% CI, 98% to 100%]), confirming the results obtained with the conventional statistical approach. Commercially available ELISA-based tests yielded the lowest specificities using a spectrum of serum samples. The evaluation of KSHV serological assays is warranted before planning serosurveys in various settings.

Apoptotic effect of ganciclovir on primary effusion lymphoma cells infected with Kaposi's sarcoma-associated herpesvirus

We evaluated the cytotoxic and apoptotic effects of two purine nucleoside analogues, acyclovir (ACV) and ganciclovir (GCV), on lymphoma cells stably harboring Kaposi's sarcoma-associated herpesvirus (KSHV). Colorimetric caspase assay, flow cytometry, and immunoblotting with antibodies against apoptosis-related molecules revealed that GCV has cytotoxic activity toward KSHV-infected primary effusion lymphoma cells, while ACV has weak or little activity. In addition to the GCV-induced cytotoxicity, apoptosis via caspase-7/8, cleavage of poly(ADP-ribose) polymerase, and accumulation of p53 and p21 were induced by GCV treatment. In contrast, neither ACV nor GCV have cytotoxicity- or apoptosis-inducing activities toward uninfected cells.

Correlations between synthetic peptide-based enzyme immunoassays and immunofluorescence assay for detection of human herpesvirus 8 antibodies in different Argentine populations

Human herpesvirus 8 (HHV-8) antibody tests vary in sensitivity and specificity, depending on the population tested and on the type of assay. In this study, we evaluated the sensitivity and specificity of two peptide enzyme immunoassays using a multiple antigenic peptide (PK8.1-MAP) or a chimeric peptide (PK8.1-orf65) as the antigens and determined the HHV-8 seroprevalence in different Argentine populations using an immunofluorescence assay (IFA) as reference. For analysis, when either or both of the peptide EIAs were positive, the specimen was considered positive (PEIA). We estimated the sensitivity and specificity of PEIA to be 97% using Kaposi's sarcoma (KS) patients and healthy individuals as positive and negative controls respectively. Then, we expanded the control groups to include IFA positive men who have sex with men (MSM) and IFA negative blood donors. The sensitivity decreased to 83% but specificity remained high at 98%. Concordance between PEIA and IFA was 77% for 1/40 IFA titers and increased to 90% for titers >or=1/160. Seroprevalences for HHV-8 performed in the HIV positive MSM were (IFA 73.1%; PEIA55.2%); heterosexuals (52.5%, 22.2%), which includes injecting drug users (IDU) (54.0%, 32.4%) and non-IDU (51.6%, 16.1%). The inclusion of non-KS HHV-8 IFA positive individuals to the positive controls may be a substantial improvement towards the realistic assessment of assay sensitivity. These peptide EIAs can be used for trends in populations with high probability of being HHV-8 infected and negative results should be confirmed by IFA. IFA test is still the most suitable test for populations with low probabilities of being infected.

Epidemiology of Kaposi's Sarcoma herpesvirus (HHV8) in Västerbotten county, Sweden

A population-based serosurvey of Human Herpesvirus type 8 (HHV8) in Västerbotten County, an area of Northern Sweden with high incidence of Kaposi's Sarcoma, was conducted. Serum samples from an age- and sex-stratified random sample of 520 subjects (260 men and 260 women) participating in a population-based biobanking project were tested for antibodies against HHV8, using a sensitive indirect immunofluorescence assay to latent and lytic HHV8 antigens. Buffy coat DNA was also analyzed for viral DNA using real time PCR assay. HHV8 DNA was not detectable in any one of the buffy coat samples. Eighty-four subjects (16.2%) were HHV8 seropositive, 14.4% for the lytic HHV8 antigen, and 1.7% for the latent HHV8 antigen. HHV8 seroprevalences were not associated significantly with sex or age. HHV8 seropositivity was more common among smokers (OR: 1.95, 95% CI: 1.02-3.75), but was less common among consumers of wine and spirits (OR: 0.44, 95% CI: 0.25-0.77 and OR: 0.50, 95% CI: 0.26-0.95, respectively). In summary, HHV8 has an intermediate high and stable seroprevalence rate in Northern Sweden, but environmental determinants that can explain the viral distribution were not found.

Human Herpesvirus 8 Infection in Hemodialysis Patients

BACKGROUND

The aim of the present study was to evaluate human herpesvirus 8 (HHV-8) seroprevalence in Greek hemodialysis patients. Patterns of change in HHV-8 serostatus (seroconversions and seroreversions) over time were also evaluated.

METHODS

Serum samples obtained from a cohort of 485 Greek hemodialysis patients were tested for antibodies to HHV-8 by whole virus lysate enzyme-linked immunosorbent assay, and reactive samples were confirmed by means of the orf-73 enzyme-linked immunosorbent assay. HHV-8 seroprevalence at study entry and the incidence of seroreversions and seroconversions per 100 person-years were estimated.

RESULTS

The prevalence of HHV-8 antibodies in Greek hemodialysis patients at enrollment was 7.2%. No univariate associations were established between HHV-8 serostatus and patients' characteristics. Incidences of seroreversions and seroconversions were 16.4/100 person-years (95% confidence interval, 7.1 to 32.3) and 0.28/100 person-years (95% confidence interval, 0.03 to 1.02), respectively. Patients 50 years and younger had an increased probability for seroreversion to HHV-8 antibodies than patients older than 50 years (log-rank test, P = 0.018).

CONCLUSION

We observed a fair number of seroreversions and a low incidence of seroconversion to HHV-8 infection in hemodialysis patients in Greece. Our data provide indirect evidence that HHV-8 transmission in the hemodialysis setting is uncommon.

Multiplex PCR-based DNA array for simultaneous detection of three human herpesviruses, EVB, CMV and KSHV

Human lymphotropic herpesviruses, Epstein-Barr virus (EBV), cytomegalovirus (CMV) and Kaposi's sarcoma-associated herpesvirus (KSHV) are responsible for a wide variety of human diseases. Due to an increase in diseased states associated with immunosuppression, more instances of co-morbid infections with these herpesviruses have resulted in viral reactivations that have caused numerous fatalities. Therefore, the development of rapid and accurate method to detect these viruses in immunocompromised patients is vital for immediate treatment with antiviral prophylactic drugs. In this study, we developed a new multiplex PCR method coupled to DNA array hybridization, which can simultaneously detect all three human herpesviruses in one single cell sample. Multiplex PCR primers were designed to amplify specific regions of the EBV (EBER1), CMV (IE) and KSHV (LANA) viral genomes. Pre-clinical application of this method revealed that this approach is capable of detecting as few as 1 copy of the viral genomes for KSHV and CMV and 100 copies of the genome for EBV. Furthermore, this highly sensitive test showed no cross-reactivity among the three viruses and is capable of detecting both KSHV and EBV viral genomes simultaneously in the lymphoblastoid cells that have been double infected with both viruses. Thus, this array-based approach serves as a rapid and reliable diagnostic tool for clinical applications.

Human herpesvirus 8--a novel human pathogen

In 1994, Chang and Moore reported on the latest of the gammaherpesviruses to infect humans, human herpesvirus 8 (HHV-8) [1]. This novel herpesvirus has and continues to present challenges to define its scope of involvement in human disease. In this review, aspects of HHV-8 infection are discussed, such as, the human immune response, viral pathogenesis and transmission, viral disease entities, and the virus's epidemiology with an emphasis on HHV-8 diagnostics.

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.

Respective roles of serological status and blood specific antihuman herpesvirus 8 antibody levels in human herpesvirus 8 intrafamilial transmission in a highly endemic area

Transmission of human herpesvirus 8 (HHV-8), the etiological agent of Kaposi's sarcoma, occurs mainly during childhood in endemic countries and, to a large extent, through intrafamilial contacts. To additionally investigate this familial transmission, and especially the role of plasma anti-HHV-8 antibody titers, we conducted a large survey in a village from Cameroon, Central Africa, including 92 families (608 individuals). Plasma samples were tested for specific IgG directed against HHV-8 lytic antigens by immunofluorescence assay, and titers were determined by 2-fold dilutions. Global HHV-8 seroprevalence was 60%, raising from 32% under 9 years up to a plateau of around 62% between 15 and 40 years. The familial correlation patterns in HHV-8 seropositive/seronegative status showed strong dependence from mother to child and between siblings. In contrast, no familial correlation in anti-HHV-8 antibody levels was observed among infected subjects. In particular, no relationship was observed between the anti-HHV-8 antibody titer of HHV-8 seropositive mothers and the proportion of their HHV-8 seropositive children. Furthermore, a random permutation study of the anti-HHV-8 antibody titers among HHV-8 infected subjects showed that the main risk factor for infection was the HHV-8 serologic status and not the antibody level. In addition, no correlation was found between anti-HHV-8 antibody levels and buffy coat HHV-8 viral loads in a subsample of 95 infected subjects. Overall, these results strongly suggest that, in this highly endemic population from Central Africa, HHV-8 transmission mainly occurs from mother to child and between siblings, and it is independent of plasma antibody levels of HHV-8 infected relatives.

Repeated measures study of human herpesvirus 8 (HHV-8) DNA and antibodies in men seropositive for both HHV-8 and HIV

OBJECTIVE

To study the natural history and pathogenesis of human herpesvirus 8 (HHV-8) infection in HHV-8-seropositive, immunosuppressed men.

DESIGN

Longitudinal study of 87 HHV-8- and HIV-seropositive men [42 with Kaposi's sarcoma (KS)] during four visits over a 2 month period.

METHODS

: Patients provided oral fluid and blood. HHV-8 antibody titers were measured with peptide-based enzyme-linked immunosorbent assays (ELISA) for ORF65 and K8.1; HHV-8 DNA was detected with polymerase chain reaction ELISA.

RESULTS

HHV-8 DNA was present in oral fluid or peripheral blood mononuclear cells (PBMC) at one or more of the four visits in 71% of men with KS and 56% of men without KS. The strongest correlate of HHV-8 DNA in PBMC was the presence of KS [odds ratio (OR), 8.7; 95% confidence interval (CI), 3.4-22]. Detection of HHV-8 DNA in oral fluid or PBMC was often intermittent, but individuals who shed virus at one time point were more likely to shed at other times. Some men had incomplete epitope recognition in their anti-HHV-8 antibody response. High antibody titers were associated with the absence of circulating HHV-8, particularly for the ORF65 seroassay (OR, 0.16; 95% CI, 0.05-0.51).

CONCLUSIONS

Among HHV-8 seropositive men, circulating virus is common even in the absence of disease. The link between KS and HHV-8 DNA in PBMC suggests that anti-herpes drugs may impede KS development or progression. Seroassays should target multiple epitopes to achieve maximal sensitivity. HHV-8 replication may be limited by high antibody titers or other immune function for which antibodies are a marker.

Comparative evaluation of three serological methods for detection of human herpesvirus 8-specific antibodies in Canadian allogeneic stem cell transplant recipients

Human herpesvirus 8 (HHV-8) has been associated with all types of Kaposi's sarcoma (KS), including posttransplantation KS. However, little is known regarding HHV-8 infections in hematopoietic stem cell transplant (SCT) recipients. In this study, we used a variety of serological assays, including in-house-developed enzyme immunoassays (EIAs) utilizing synthetic peptides corresponding to lytic viral antigens (ORFs 65 and K8.1) and a commercial EIA kit based on a whole virus lysate (Advanced Biotechnologies Inc.), as well as latent- and lytyc-antigen-based immunofluorescence assays (IFAs) to determine the seroprevalence of HHV-8 in 42 allogeneic SCT recipients from Canada. Using the two peptide-based EIA methods as for screening, HHV-8-specific antibodies were detected in five (12%) patients between days 21 and 91, although only one (2%) subject was positive for HHV-8-specific antibodies before transplantation. All positive results from these five patients were confirmed by at least one of the IFAs, with an additional patient showing seropositivity before transplantation. However, the commercial EIA was negative at all time points (days -7, 21, and 91) in those five patients. The episodes of seroconversion or reactivation were not associated with sustained viremia, since HHV-8 DNA was not detected by real-time PCR in the corresponding leukocytes and plasma of the seropositive patients. No clinical or laboratory abnormalities were clearly associated with HHV-8 seropositivity. This study confirms the utility of simple peptide-based EIA methods to assess the presence of HHV-8-specific antibodies in immunocompromised patients and emphasizes the need of conducting prospective studies to determine the source of HHV-8 infection in SCT recipients.

Human herpesvirus 8 seroconversion in Kenyan women by enzyme-linked immunosorbent assay and immunofluorescence assay

BACKGROUND

Human herpesvirus 8 (HHV-8) antibody tests vary in reported sensitivity and specificity, depending on the population tested and the assay.

OBJECTIVE

The purpose of this study was to compare the ability to detect seroconversion to HHV-8 in a cohort of HHV-8 seronegative female commercial sex workers in Kenya using three tests: HHV-8 viral lysate-based enzyme-linked immunosorbent assay (ELISA), an immunofluorescence assay for HHV-8 lytic antigens (IFA-lytic) and IFA for latent nuclear antigens (IFA-LANA).

STUDY DESIGN

By ELISA, 16 women from a prospective cohort of commercial sex workers were identified as seroconverting to HHV-8. A total of 124 post-enrollment samples from these 16 women as well as the enrollment samples were tested for HHV-8 antibodies by all three assays to monitor seroconversion.

RESULTS

Of 16 women with apparent seroconversion by ELISA, 8 had a rise in IFA-lytic titers either concomitant with or prior to the first positive ELISA sample and no initial LANA by IFA. Five of the 16 women were IFA-LANA positive at entry, indicating prior infection with HHV-8. Three women had no evidence of seroconversion by either IFA-lytic or IFA-LANA and two of these three had increased ELISA reactivity concomitant with HIV-1 infection.

CONCLUSIONS

Conversion from a negative to a positive ELISA result for HHV-8 antibody indicated seroconversion in only half of the study cohort of 16 women when IFA-lytic and IFA-LANA results were considered. The IFA-lytic assay was more sensitive than ELISA for early antibody responses. The IFA-LANA was positive in some women who had neither IFA-lytic nor ELISA antibodies suggesting it may be a marker for latent infections. Presumptive identification of incident HHV-8 infection by ELISA screening followed by IFA-lytic testing to confirm the positive test and IFA-LANA to rule out prior infection provides the most accurate documentation of HHV-8 seroconversion.

Antibodies against human herpesvirus 8 in South African renal transplant recipients and blood donors

OBJECTIVE

To examine the seroprevalence of human herpesvirus 8 (HHV-8) antibodies in a selected group of renal transplant recipients and blood donors, in relation to various socio-demographic variables.

SUBJECTS

Anonymised serum samples were obtained from 306 black donors attending blood donations at the SA National Blood Transfusion Service, Johannesburg, and 430 recipients of renal transplants at Johannesburg General Hospital, from 1998 to 1999.

METHODOLOGY

Serum samples were tested by indirect immunofluorescence assay to detect IgG antibodies against HHV-8. Crude and adjusted seroprevalence, and odds ratios were calculated to examine the relationship between antibodies to HHV-8 and age, sex, population, and risk group.

RESULTS

Adjusted HHV-8 seroprevalence at 'medium to high' antibody titres (at least 1:51,200) increased with age, from 2% (age 15-24; 95% CI=0.7-5.2) to 10% (age 45+; 95% CI=6.3-15.2). Whites had the lowest % adjusted seroprevalence (1.8; 95% CI:0.8-4.2), followed by blacks (7.4; 95% CI=5.1-10.8), Asians/Indians (9.5; 95% CI=3.6-22.9), and individuals of mixed race (12.5; 95% CI=4.5-30.2). Seroprevalence was not related to gender, or to occupation of blood donors. HHV-8 seroprevalence did not differ significantly between first-time blood donors, repeat donors, and transplant recipients (P=0.49). Transplant recipients had a greater proportion of persons with high HHV-8 antibody intensity; however, this difference was statistically not significant (P=0.08).

CONCLUSIONS

Blood donors and renal transplant patients had relatively high HHV-8 antibody titres. Given the strong association between HHV-8 seropostivity and the risk of developing Kaposi's sarcoma, it may be prudent in settings where HHV-8 seroprevalence is high to screen for HHV-8 in donated blood used for these immunocompromised individuals.

Comparison of human herpesvirus 8 and Epstein-Barr virus seropositivity among children in areas endemic and non-endemic for Kaposi's sarcoma

Human herpesvirus 8 (HHV-8) is the etiologic agent of Kaposi's sarcoma (KS). Several studies indicate horizontal HHV-8 transmission among children in areas where KS is endemic, but few studies have assessed acquisition of HHV-8 by children in low seroprevalence areas. Antibody screening was carried out for HHV-8 and Epstein-Barr virus (EBV) on 787 serum specimens from children living in two areas where HHV-8 is not endemic, the United States (US) and Germany, and on 184 specimens from children living in a KS-endemic area (Nigeria). For children in the US and Germany, the results showed low HHV-8 seroprevalence rates (3-4%). However, US children aged 6 months to 5 years had higher HHV-8 antibody titers than did 6-17-year-old children (P < 0.01), a finding consistent with more recent infections being detected in the younger children. Compared with seroprevalence rates and antibody titers in US and German children, those in Nigerian children were significantly higher, and seroprevalence increased with age. There was no evidence of cross-reactivity between assays for HHV-8 and EBV, despite the genetic similarity of these two herpesviruses. The data indicate that HHV-8 transmission among children where HHV-8 is not endemic occurs, but is uncommon. The findings also suggest that HHV-8 antibodies, as measured by current tests, may not persist for long periods in populations at low risk for KS and that vertical transmission is rare, although longitudinal studies are necessary to address directly these issues.

Prevalence of antibodies to human herpesvirus-8 in populations with and without risk for infection in São Paulo State

Human herpesvirus 8 (HHV-8) is a newly described herpesvirus that is etiologically associated with all forms of Kaposi's sarcoma (KS). Seroepidemiological studies have shown high prevalence rates of HHV-8 antibodies among men who have sex with men (MSM) and AIDS patients, African children, Brazilian Amerindians, and elderly individuals in certain regions of Europe. The aim of the present study was to determine the prevalence of HHV-8 antibodies in healthy children and young adults from different cities in São Paulo State, and in a population at high risk for HHV-8 infection: HIV-negative MSM, and AIDS patients with and without KS. Antibodies to HHV-8 latency-associated nuclear antigen and lytic-phase antigens were detected by immunofluorescence assays. In 643 healthy children and young adults from the general population attending a vaccination program for yellow fever in ten different cities in São Paulo State, the prevalence of HHV-8 antibodies detected by the presence of latent or lytic antigens ranged from 1.0 to 4.1% in the different age groups (mean=2.5%). In the MSM group, the prevalence was 31/95 (32.6%). In the group of patients with AIDS, the prevalence was 39.2% (51/130) for non-KS patients and 98.7% (77/78) for AIDS patients with the diagnosis of KS confirmed by histopathological examination. We conclude that HHV-8 has a restricted circulation among healthy children and young adults in the general population of São Paulo State and a high prevalence among MSM and AIDS patients.

Human Herpesvirus 8 Infection Among Various Population Groups in Southern Israel

OBJECTIVE

To compare the prevalence of antibodies to human herpesvirus 8 (HHV-8) or Kaposi sarcoma-associated herpesvirus among Israeli and Ethiopian subjects.

METHODS

Serum samples were obtained from 98 Israeli Jewish students aged 18-30 years, 100 HIV-1-seronegative Ethiopian immigrants to Israel of the same age, and 100 HIV-1-seronegative Ethiopian children 1-12 years old upon their arrival in southern Israel. Plasma samples were obtained from 3 hospitalized patients with multicentric Castleman disease (MCD) as positive controls. All serum samples were tested for antibodies to both latent and lytic antigens. Antibodies to the lytic antigens and the latency-associated nuclear antigen (LANA) of HHV-8 were detected by enzyme linked immunosorbent assay and by immunofluorescence assay. HHV-8 DNA from serum or plasma samples was detected by polymerase chain reaction analysis.

RESULTS

Antibodies to HHV-8 LANA were detected in 2.9% of the Israeli subjects aged 18-30 years and in 26% of the Ethiopian subjects from both age groups tested. Antibodies to the lytic antigens were detected in all 3 MCD patients, in 4% of the Ethiopian children, and in 2% of the 18- to 30-year-old Ethiopians. No antibodies to the lytic antigens were detected in the Israeli students. HHV-8 DNA was detected in all 3 MCD patients and in 2 of 4 of the Ethiopian children positive for the lytic antigens.

CONCLUSIONS

HHV-8 is highly prevalent in Ethiopian immigrants to Israel as compared with Israeli students. Antibodies to HHV-8 in Ethiopia are acquired before puberty. The results of this study indicate the association of HHV-8 with MCD, as has been documented by many other researchers.

Multicenter comparison of serologic assays and estimation of human herpesvirus 8 seroprevalence among US blood donors

BACKGROUND

As part of assessing the possibility of transfusion transmission of human herpesvirus 8 (HHV-8 or Kaposi's sarcoma-associated herpesvirus), HHV-8 seroprevalence was estimated among US blood donors, the performance of HHV-8 serologic tests was compared, and the presence of HHV-8 DNA was tested for in donated blood.

STUDY DESIGN AND METHODS

Replicate panels of 1040 plasma specimens prepared from 1000 US blood donors (collected in 1994 and 1995) and 21 Kaposi's sarcoma patients were tested for antibodies to HHV-8 in six laboratories. HHV-8 PCR was performed on blood samples from 138 donors, including all 33 who tested seropositive in at least two laboratories and 22 who tested positive in at least one.

RESULTS

The estimated HHV-8 seroprevalence among US blood donors was 3.5 percent (95% CI, 1.2%-9.8%) by a conditional dependence latent-class model, 3.0 percent (95% CI, 2.0%-4.6%) by a conditional independence latent-class model, and 3.3 percent (95% CI, 2.3%-4.6%) by use of a consensus-derived gold standard (specimens positive in two or more laboratories); the conditional dependence model best fit the data. In this model, laboratory specificities ranged from 96.6 to 100 percent. Sensitivities ranged widely, but with overlapping 95 percent CIs. HHV-8 DNA was detected in blood from none of 138 donors evaluated.

CONCLUSIONS

Medical and behavioral screening does not eliminate HHV-8-seropositive persons from the US blood donor pool, but no viral DNA was found in donor blood. Further studies of much larger numbers of seropositive individuals will be required to more completely assess the rate of viremia and possibility of HHV-8 transfusion transmission. Current data do not indicate a need to screen US blood donors for HHV-8.

AIDS-related malignancies

Immunodeficiency alters the risk of cancer. Specific types of immune dysfunction are associated with different tumor risks, but most tumors are related to oncogenic viruses. In acquired immunodeficiency due to the human immunodeficiency virus (HIV), HIV itself rarely directly causes cancer; rather, it provides the immunologic background against which other viruses can escape immune control and induce tumors. The most common malignancies are Kaposi's sarcoma and non-Hodgkin's lymphoma. This chapter discusses the pathophysiologic background of these tumors, how they have been affected by the use of anti-HIV medications, and their clinical management.

Molecular genetics of Kaposi's sarcoma-associated herpesvirus (human herpesvirus-8) epidemiology and pathogenesis

Kaposi's sarcoma had been recognized as unique human cancer for a century before it manifested as an AIDS-defining illness with a suspected infectious etiology. The discovery of Kaposi's sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus-8, in 1994 by using representational difference analysis, a subtractive method previously employed for cloning differences in human genomic DNA, was a fitting harbinger for the powerful bioinformatic approaches since employed to understand its pathogenesis in KS. Indeed, the discovery of KSHV was rapidly followed by publication of its complete sequence, which revealed that the virus had coopted a wide armamentarium of human genes; in the short time since then, the functions of many of these viral gene variants in cell growth control, signaling apoptosis, angiogenesis, and immunomodulation have been characterized. This critical literature review explores the pathogenic potential of these genes within the framework of current knowledge of the basic herpesvirology of KSHV, including the relationships between viral genotypic variation and the four clinicoepidemiologic forms of Kaposi's sarcoma, current viral detection methods and their utility, primary infection by KSHV, tissue culture and animal models of latent- and lytic-cycle gene expression and pathogenesis, and viral reactivation from latency. Recent advances in models of de novo endothelial infection, microarray analyses of the host response to infection, receptor identification, and cloning of full-length, infectious KSHV genomic DNA promise to reveal key molecular mechanisms of the candidate pathogeneic genes when expressed in the context of viral infection.

Determination of antiviral efficacy against lymphotropic herpesviruses utilizing flow cytometry

Epstein-Barr virus (EBV), human herpesvirus type 6 (HHV-6), and human herpesvirus type 8 (HHV-8) comprise a group of lymphotropic herpesviruses which are responsible for a wide range of diseases, including lymphoproliferative disorders and tumors. We have developed several flow cytometric assay (FACS) systems to evaluate antiviral efficacy against EBV, HHV-6 and HHV-8. Assays using either EBV or HHV-8, members of the gammaherpesvirus subfamily, have shown that while EBV responds well to acyclovir (ACV), HHV-8 was most sensitive to cidofovir (CDV). Since HHV-6 strains are divided into two sub-groups, A and B, we evaluated antiviral efficacy for strains from each group. The group A strain, HHV-6(GS), was inhibited by foscarnet (PFA), CDV and ganciclovir (GCV) in both Sup-T1 and HSB-2 cell lines. HHV-6(Z-29), a representative group B virus, was inhibited by GCV and CDV but not by PFA. Our findings indicate that flow cytometry can be utilized to efficiently evaluate new antiviral agents against lymphotropic herpesviruses and that the results are comparable to those obtained by other methods such as immunofluorescence.

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.

Human herpesvirus 8 infection

Human herpesvirus 8, also known as Kaposi sarcoma-associated herpesvirus, is etiologically associated with Kaposi sarcoma and other rare malignancies. Human herpesvirus 8 infection is common in certain areas of Africa and Italy, but occurs in only 0% to 15% of adult populations in North America and Europe. Reports of human herpesvirus 8 prevalence of 3% to over 50% among children in Central Africa, Brazil, and South Texas suggest that horizontal transmission of human herpesvirus 8 occurs among children. Primary human herpesvirus 8 infection in immunocompetent children is associated with a fever and maculopapular rash.

Detection of human herpesvirus-8 in peripheral blood mononuclear cells from adult Japanese patients with multicentric Castleman's disease

Human herpesvirus-8 (HHV-8) encodes viral homologues of cellular genes, including viral interleukin 6 (vIL-6), which induces endogenous human IL-6 (hIL-6) secretion. Unregulated overproduction of hIL-6 in lymph nodes (LN) is thought to be responsible for the systemic manifestations of multicentric Castleman's disease (MCD). In the present study, we assessed the presence of HHV-8 and HHV-8-encoded viral homologues in LN and peripheral blood mononuclear cells (PBMC) from adult Japanese patients with MCD. HHV-8 DNA was amplified by nested polymerase chain reaction (PCR) and was detected in LN from 13 out of 16 MCD patients (81%). HHV-8 DNA was also detected in PBMC from six out of seven patients (86%) whose LN were positive for HHV-8 DNA. Because mRNA could not be successfully extracted from LN sections that were either formalin-fixed or embedded in paraffin, we examined the expression of mRNA for HHV-8-encoded viral homologues, such as vIL-6, vBCL-2, vCyclin-D and viral G-protein-coupled receptor (vGPCR) by nested reverse transcription (RT)-PCR in PBMC from 10 MCD patients. However, mRNA of these HHV-8-encoded viral homologues was not detected in any patients tested. Although our results do not indicate a role for HHV-8-encoded viral homologues in the pathogenesis of MCD, they do suggest that HHV-8 infection may be associated with MCD in adult Japanese patients.

Human herpesvirus 8 seroprevalence and viral load in healthy adult blood donors

BACKGROUND

Human herpesvirus 8 (HHV-8) is widely suspected to be a human tumor virus because it is associated with Kaposi's sarcoma and primary effusion B cell lymphoma. Report of a case of HHV-8-positive donor blood in the US has led to concern for the safety of donor blood from HHV-8-seropositive donors.

STUDY DESIGN AND METHODS

The findings of HHV-8 seroprevalence and virus load from 100 randomly selected blood donors from the Houston, Texas, area are reported. Serology with serial titration was performed using a highly sensitive indirect immunofluorescence assay to lytic and latent HHV-8 antigens. For detection of blood-borne virus, buffy-coat DNA was subjected to two ultrasensitive nested PCR-dot blot assays to HHV-8 orf26 and orf72 regions.

RESULTS

At a screening titer of 1 in 10, nearly one-quarter (23%; 95% CI, 15-33) of the blood donors are HHV-8 seropositive with a geometric mean titer of 1 in 53. Seroreactivity to lytic antigens (23%) greatly exceeded that to latent antigens (5%). There was a significant association between seropositivity and older age (p < 0.02), white ethnicity (OR, 3.33; 95% CI, 1.40-7.95) and ABO blood group B (OR, 6.44; 95% CI, 2.46-16.80). No association with sex or CMV seropositivity was demonstrated. No HHV-8 viremia was detected, even though 64 percent of tested donor blood samples were EBV DNA positive.

CONCLUSIONS

Despite a relatively high HHV-8 seroprevalence in this cohort of Houston area blood donors, HHV-8 DNA was not detected in any sample of donor whole blood using a highly sensitive PCR assay. Thus, at least in the southeast Texas region, large-scale screening of blood donor units for HHV-8 antibody or DNA seems unwarranted.

Human herpesvirus 8, Kaposi's sarcoma, and associated conditions

HHV-8 is a recently identified human herpes virus that can produce tumors, most often in immune compromised hosts. The virus is most closely associated with Kaposi's sarcoma, but is also clearly associated with primary effusion lymphomas and multicentric Castleman's disease. The prevalence of HHV-8 infection varies considerably, but is highest among men who have sex with men and others with histories of sexually transmitted diseases and high numbers of lifetime sexual partners. HHV-8 is shed in saliva, and less commonly in genital secretions. Treatment of HHV-8 associated diseases includes reversal of immune compromise either via discontinuation of immunosuppressives or immune reconstitution via antiretroviral regimens. Specific antiviral drug inhibit HHV-8 replication, and can result in responses in certain HHV-8-associated conditions.

Laboratory diagnosis of human herpesvirus 8 infection in humans

Human herpesvirus 8 (HHV-8) is causally associated with Kaposi's sarcoma, primary effusion lymphoma and multicentric Castleman's disease. Serological and molecular biology assays are used to investigate the biology of this virus in different populations and diseases. Serological assays are mainly used to study the prevalence of the viral infection and to predict the diagnosis of Kaposi's sarcoma and other HHV-8-associated cancers. The appearance of antibodies against lytic antigens precedes the appearance of antibodies against latent antigens, probably explaining the lower sensitivity of assays based on latent HHV-8 antigens. The lack of international reference serum panels is presently the major bottleneck for further progress in the field of HHV-8 serology. Molecular biological assays are an absolute requirement for both the diagnosis and the follow-up of HHV-8 infection. Qualitative methods have been particularly useful to elucidate the mode of transmission and the causal association between HHV-8 and HHV-8-associated diseases. Quantitative methods have become an essential tool to monitor the progression of the infection and the effects of antiviral therapies. This review analyzes the performance of the different serological and molecular biological assays available at present. The main conclusion is that more research is needed to define the most useful laboratory tests for the diagnosis of HHV-8 infection and to establish the clinical role of such tests.

Prospective study of the effects of antiretroviral therapy on Kaposi sarcoma--associated herpesvirus infection in patients with and without Kaposi sarcoma

OBJECTIVE

To investigate the effect of highly active antiretroviral therapy (HAART) on circulating Kaposi sarcoma (KS)-associated herpesvirus (KSHV) load in HIV-infected individuals with and without KS.

DESIGN

Twenty-nine HIV-infected subjects (21 with KS and 8 without KS) were recruited for the study; they were prospectively studied before and at regular intervals during HAART.

METHODS

Patients with KS were clinically assessed using Adult Clinical Trials Group (ACTG) criteria, and sequential blood samples were obtained from all patients for determination of plasma HIV-1 load, CD4 cell count, titer of antibody to KSHV, and KSHV load.

RESULTS

Ten of 21 patients with KS had a favorable KS response (complete response, 6; partial response, 4) with HAART alone. Of the 20 subjects with detectable KSHV viremia prior to HAART, over one half (12 [60%]) had an undetectable KSHV load with antiretroviral therapy. There was no significant difference between subjects receiving protease inhibitor- or nonnucleoside reverse transcriptase inhibitor-based treatment combinations. Achieving undetectable KSHV viremia is associated with a better clinical outcome in patients with KS.

CONCLUSIONS

To our knowledge, we demonstrate for the first time that both protease inhibitor-based and nonnucleoside reverse transcriptase inhibitor-based antiretroviral treatment combinations may lead to an undetectable KSHV load and confirm that an undetectable KSHV load is associated with KS regression. There was no clear association between CD4 cell count response and KS response to HAART, but there was a significant relationship between HIV load response to HAART and clinical improvement of KS.