Prevalence of antibodies to human herpesvirus 8 (HHV-8) in Saudi Arabian patients with and without renal failure.

BACKGROUND: Kaposi's sarcoma (KS) is the most common cancer occurring in renal transplant recipients in Saudi Arabia, where the reported incidence of posttransplantation KS is 10 times higher than the incidence in the United States and Western Europe. The reason for the particularly high incidence of posttransplantation KS in this geographic area is unknown. METHODS: To explore the possibility that the high incidence of posttransplantation KS might be the result of widespread infection with human herpesvirus 8 (HHV-8), we determined the prevalence of antibodies to HHV-8 in 201 patients with end-stage renal disease (ESRD) and a comparison group of 358 individuals without renal disease who were similar in age, sex, and area of residence. Antibodies to lytic cycle antigens of HHV-8 were determined by indirect immunofluorescence and confirmed by immunoblots using tetradecanoyl phorbol ester acetate-induced BC-3 cell extracts and recombinant small viral capsid antigen (ORF65). RESULTS: Antibodies to HHV-8 were detected in serum samples from 14 (6.97%) of 201 ESRD patients and from 10 (3.88%) of 258 in the comparison group (P=0.14). HHV-8 seropositive individuals were on average 10 years older than seronegative subjects (55.3 years vs. 46.9 years). Among HHV-8 seropositive subjects, 71% were male and 29% were female. CONCLUSIONS: Serologic evidence of HHV-8 infection was numerically more common in men and in patients with ESRD. However, among patients with and without ESRD, the strongest association was with increasing age.

High prevalence of antibodies to human herpesvirus 8 in relatives of patients with classic Kaposi's sarcoma from Sardinia.

A survey for antibodies to a recombinant small viral capsid antigen (sVCA) of human herpesvirus type 8 (HHV-8) was conducted in Sardinia, one of the world's highest incidence areas for classic Kaposi's sarcoma (KS). Prevalence of antibodies to HHV-8 sVCA was greatest in patients with KS (95%), followed by family members (39%) and a Sardinian control population age- and sex-matched to the relatives (11%). Within families, prevalence of antibodies was about equal among spouses, children, and siblings of KS patients, a finding that raises the possibilities of intrafamilial person-to-person or vertical transmission. Antibodies were detected 2-3 times more frequently in males than in females. The data show that prevalence of antibodies to HHV-8 sVCA correlates with the distribution of classic KS in a high- incidence area. Clustering of seroprevalence within some families suggests the presence of familial risk factors for active HHV-8 infection.

Serologic association of human herpesvirus eight with posttransplant Kaposi's sarcoma in Saudi Arabia.

BACKGROUND: This study investigates the association between human herpesvirus eight (HHV8) and Kaposi's sarcoma (KS), the most common cancer occurring in renal transplant recipients in Saudi Arabia. METHODS: A cross-sectional study of seroreactivity to HHV8 antigens in posttransplant KS patients from a tertiary care hospital in Riyadh, Saudi Arabia, and in control subjects without KS was conducted. Seroreactivity rates were determined using immunoblotting assays to detect antibodies to two lytic cycle HHV8 antigens: p40, an antigen found in infected cells, and sVCA, an HHV8-encoded small viral capsid antigen expressed in Escherichia coli. RESULTS: Antibodies to HHV8 p40 and sVCA were present in a significantly higher proportion of renal transplant patients with KS (13 of 14 patients) compared to renal transplant patients without KS (5 of 18; P<0.001) and compared to other control individuals (6 of 44; P<0.001). HHV8 seroreactivity was more common among patients with renal failure (28%) than among other control groups (7%). CONCLUSIONS: The serologic results provide evidence of a strong association between HHV8 and posttransplant KS in Saudi Arabia.

PIP: In Saudi Arabia, Kaposi's sarcoma occurs in 4.1% of renal transplant recipients and accounts for 70% of malignancies in this group. Human herpes virus 8 (HHV8) has been identified in the DNA of many of these patients. The association between HHV8 and Kaposi's sarcoma was investigated further in post-renal transplant Kaposi's sarcoma patients from a tertiary care hospital (King Faisal Specialist Hospital and Research Center) in Riyadh, Saudi Arabia (n = 14), and non-Kaposi's sarcoma controls with renal transplant (n = 18), chronic renal failure (n = 14), other cancers that did not affect renal function (n = 15), and healthy volunteers (n = 15). The median time from transplant to Kaposi's sarcoma was 13 months. A serum sample was assumed to have antibodies to HHV8 if antibody to either p40 or sVCA was detected. The prevalence of HHV8 seroreactivity was 13/14 (93%) in cases, 5/18 (28%) in renal transplants without Kaposi's sarcoma, and 11/62 (18%) in the aggregate control group. HHV8 seroreactivity was significantly more common (p 0.001) among transplant patients with Kaposi's sarcoma than those without this cancer (odds ratio, 33.80; 95% confidence interval, 2.96-904). These findings suggest an etiologic link between HHV8 and Kaposi's sarcoma presumably due to immunologic or cellular factors that influence host-virus interactions.

Identification, expression, and immunogenicity of Kaposi's sarcoma-associated herpesvirus-encoded small viral capsid antigen.

We describe a recombinant antigen for use in serologic tests for antibodies to Kaposi's sarcoma (KS)-associated herpesvirus (KSHV). The cDNA for a small viral capsid antigen (sVCA) was identified by immunoscreening of a library prepared from the BC-1 body cavity lymphoma cell line induced into KSHV lytic gene expression by sodium butyrate. The cDNA specified a 170-amino-acid peptide with homology to small viral capsid proteins encoded by the BFRF3 gene of Epstein-Barr virus and the ORF65 gene of herpesvirus saimiri. KSHV sVCA was expressed from a 0.85-kb mRNA present late in lytic KSHV replication in BC-1 cells. This transcript was sensitive to phosphonoacetic acid and phosphonoformic acid, inhibitors of herpesvirus DNA replication. KSHV sVCA expressed in mammalian cells or Escherichia coli or translated in vitro was recognized as an antigen by antisera from KS patients. Rabbit antisera raised to KSHV sVCA expressed in E. coli detected a 22-kDa protein in KSHV-infected human B cells. Overexpressed KSHV sVCA purified from E. coli and used as an antigen in immunoblot screening assay did not cross-react with EBV BFRF3. Antibodies to sVCA were present in 89% of 47 human immunodeficiency virus (HIV)-positive patients with KS, in 20% of 54 HIV-positive patients without KS, but in none of 122 other patients including children born to HIV-seropositive mothers and patients with hemophilia, autoimmune disease, or nasopharyngeal carcinoma. Low-titer antibody was detected in three sera from 28 healthy subjects. Antibodies to recombinant sVCA correlate with KS in high-risk populations. Recombinant sVCA can be used to examine the seroepidemiology of infection with KSHV in the general population.

Selective switch between latency and lytic replication of Kaposi's sarcoma herpesvirus and Epstein-Barr virus in dually infected body cavity lymphoma cells.

The BC-1 cell line, derived from a body cavity-based, B-cell lymphoma, is dually infected with Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV). In these studies, the relationships between these two gammaherpesviruses and BC-1 cells were characterized and compared. Single-cell cloning experiments suggested that all BC-1 cells contain both genomes. In more than 98% of cells, both viruses were latent. The two viruses could be differentially induced into their lytic cycles by chemicals. EBV was activated into DNA replication and late-gene expression by the phorbol ester tetradecanoyl phorbol acetate (TPA). KSHV was induced into DNA replication and late-gene expression by n-butyrate. Amplification of both EBV and KSHV DNAs was inhibited by phosphonoacetic acid. Induction of the KSHV lytic cycle by n-butyrate was accompanied by the disappearance of host-cell beta-actin mRNA. Induction of EBV by TPA was not accompanied by such an effect on host-cell gene expression. Induction of the KSHV lytic cycle by n-butyrate was associated with the expression of several novel polypeptides. Recognition of one of these, p40, served as the basis of development of an assay for antibodies to KSHV in the sera of infected patients. BC-1 cells released infectious EBV; however, there was no evidence for the release of encapsidated KSHV genomes by BC-1 cells, even though n-butyrate-treated cells contained numerous intranuclear nucleocapsids. The differential inducibility of these two herpesviruses in the same cell line points to the importance of viral factors in the switch from latency to lytic cycle.

Antibodies to butyrate-inducible antigens of Kaposi's sarcoma-associated herpesvirus in patients with HIV-1 infection.

BACKGROUND: The recent identification in patients with Kaposi's sarcoma of DNA sequences with homology to gammaherpesviruses has led to the hypothesis that a newly identified virus, Kaposi's sarcoma-associated herpeslike virus (KSHV), has a role in the pathogenesis of Kaposi's sarcoma. We developed serologic markers for KSHV infection. METHODS: KSHV antigens were prepared from a cell line (BC-1) that contains the genomes of both KSHV and the Epstein-Barr virus (EBV). We used immunoblot and immunofluorescence assays to examine serum samples from 102 patients with human immunodeficiency virus type 1 (HIV-1) infection for antibodies to KSHV-associated proteins and to distinguish these antibodies from antibodies to EBV antigens. A positive serologic response was defined by the recognition of an antigenic polypeptide, p40, in n-butyrate-treated BC-1 cells and by the absence of p40 recognition in untreated BC-1 cells or EBV-infected, KSHV-negative cells. The detection by the immunofluorescence assay of 10 to 20 times more antigen-positive cells in n-butyrate-treated BC-1 cells than in untreated cells was considered a positive response. RESULTS: Antibodies to the p40 antigen expressed by chemically treated BC-1 cells were identified in 32 of 48 HIV-1-infected patients with Kaposi's sarcoma (67 percent), as compared with only 7 of 54 HIV-1-infected patients without Kaposi's sarcoma (13 percent). These results were confirmed by an immunofluorescence assay. The positive predictive value of the serologic tests for Kaposi's sarcoma was 82 percent, and the negative predictive value 75 percent. CONCLUSIONS: The presence of antibodies to a KSHV antigenic peptide correlates with the presence of Kaposi's sarcoma in a high-risk population and provides further evidence of an etiologic role for KSHV.