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.

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.

Comparison of a microtiter plate system to Southern blot for detection of human herpesvirus 8 DNA amplified from blood and saliva.

The recent discovery of human herpesvirus 8 (HHV-8) as the etiologic agent of Kaposi's sarcoma (KS) has led to the interest in the development of PCR for this virus that is accurate, rapid, and convenient. We developed a sensitive PCR assay for HHV-8 with microtiter plate detection of amplimers. DNA was purified from white blood cells and saliva from HIV-infected men with and without Kaposi's sarcoma and one-step PCR was undertaken with primer sets specific for the N-terminal region of the glycoprotein B gene and open reading frame (orf) 26 of HHV-8. PCR was performed on 40 clinical specimens, followed by Southern blot and microtiter plate detection of amplimers. Results from the two methods of detection were nearly identical. Sensitivity for both methods based on serial dilution of a known standard was five to ten copies of HHV-8 per 400 ng of cellular DNA. In conclusion, microtiter plate detection of HHV-8 PCR amplimers is as sensitive and specific as Southern blot with much faster turnaround time at comparable cost, and utilizes common laboratory equipment.

Differences in DNA binding specificity among Roseolovirus origin binding proteins.

The Roseolovirus genus of the Betaherpesvirinae consists of the very closely related viruses, human herpesvirus 6 variants A and B (HHV-6A and HHV-6B) plus the somewhat more distantly related human herpesvirus 7 (HHV-7). The roseoloviruses each encode a homolog of the alphaherpesvirus origin binding protein (OBP) which is required for lytic DNA replication. In contrast, members of the other betaherpesvirus genera, the cytomegaloviruses, initiate DNA replication by a different mechanism. To better understand the basis of roseolovirus OBP sequence specificity, we investigated their ability to recognize each other's binding sites. HHV-6A OBP (OBP(H6A)) and HHV-6B OBP (OBP(H6B)) each bind to both of the HHV-7 OBP sites (OBP-1 and OBP-2) with similar strengths, which are also similar to their nearly equivalent interactions with their own sites. In contrast, HHV-7 OBP (OBP(H7)) had a gradient of binding preferences: HHV-7 OBP-2 > HHV-6 OBP-2 > HHV-7 OBP-1 > HHV-6 OBP-1. Thus, the roseolovirus OBPs are not equally reciprocal in their recognition of each other's OBP sites, suggesting that the sequence requirements for the interaction of OBPH7 at the OBP sites in its cognate oriLyt differ from those of OBPH6A and OBPH6B.

Quantitative, fluorogenic probe PCR assay for detection of human herpesvirus 8 DNA in clinical specimens.

A quantitative, fluorescence-based PCR assay (TaqMan-based system) was developed for detection of human herpesvirus 8 (HHV-8) DNA in clinical specimens. Primers and probes chosen from each of five 10-kb segments from the unique region of the HHV-8 genome were evaluated for sensitivity with dilution series of DNA extracted from a cell line (BCBL-1) that harbors HHV-8 DNA. Although several of the primer-probe sets performed similarly with BCBL-1 DNA that had been diluted in water, their performance differed when target DNA was diluted in a constant background of uninfected cell DNA, an environment more relevant to their intended use. The two best primer-probe combinations were specific for HHV-8 relative to the other known human herpesviruses and herpesvirus saimiri, a closely related gammaherpesvirus of nonhuman primates. PCRs included an enzymatic digestion step to eliminate PCR carryover and an exogenous internal positive control that enabled discrimination of false-negative from true-negative reactions. The new assays were compared to conventional PCR assays for clinical specimens (saliva, rectal brushings, rectal swab specimens, peripheral blood lymphocytes, semen, and urine) from human immunodeficiency virus-positive patients with or without Kaposi's sarcoma. In all instances, the new assays agreed with each other and with the conventional PCR system. In addition, the quantitative results obtained with the new assays were in good agreement both for duplicate reactions in the same assay and between assays.

Comparison of serologic assays for detection of antibodies against human herpesvirus 8.

Improvement of serologic assays for detection of antibodies against human herpesvirus 8 (HHV-8) is critical to better understand its epidemiology and biology. We produced the HHV-8 latent (ORF73) and lytic (ORF65, K8.1, and glycoprotein B) antigens in the Semliki Forest virus system and evaluated their performance in immunofluorescence assays (IFAs) and enzyme-linked immunosorbent assays (ELISAs). These assays were compared with other latent antigen-based assays, including an IFA based on primary effusion lymphoma (PEL) cells and an ELISA based on bacterially expressed ORF73 antigen, as well as with other lytic antigen-based assays, including an IFA based on induced PEL cells, a commercial ELISA based on purified virions, and ELISAs based on K8.1- and ORF65-derived oligopeptides. We used a panel of 180 serum specimens obtained from three groups expected to have high, intermediate, and low HHV-8 prevalences. Using three different evaluation methods, we found that (i) the performances of the lytic antigen-based ELISAs were almost equivalent, (ii) the lytic antigen-based assays were more sensitive than the latent antigen-based assays, and (iii) in general, IFAs were more sensitive than ELISAs based on the same open reading frame. We also found that serum specimens from healthy individuals contained antibodies cross-reactive with HHV-8 glycoprotein B that can potentially cause false-positive reactions in lytic PEL-based IFAs. Although this is not a substantial problem in most epidemiologic studies, it may confound the interpretation of data in studies that require high assay specificity. Because the K8.1-based IFA provides sensitivity similar to that of lytic PEL-based IFAs and improved specificity, it can be a useful alternative to the PEL-based IFAs.

Primary human herpesvirus 8 infection generates a broadly specific CD8(+) T-cell response to viral lytic cycle proteins.

Human herpesvirus 8 (HHV-8) is a recently discovered gammaherpesvirus that is the etiologic agent of Kaposi sarcoma (KS). The natural history of primary HHV-8 infection, including clinical outcome and host immune responses that may be important in preventing disease related to HHV-8, has not been elucidated. The present study characterized the clinical, immunologic, and virologic parameters of primary HHV-8 infection in 5 cases detected during a 15-year longitudinal study of 108 human immunodeficiency virus type 1 seronegative men in the Multicenter AIDS Cohort Study. Primary HHV-8 infection was associated with mild, nonspecific signs and symptoms of diarrhea, fatigue, localized rash, and lymphadenopathy. There were no alterations in numbers of CD4(+) or CD8(+) T cells or CD8(+) T-cell interferon gamma (IFN-gamma) production to mitogen or nominal antigen. CD8(+) cytotoxic T-lymphocyte precursor (CTLp) and IFN-gamma reactivity were detected during primary HHV-8 infection, with broad specificity to 5 lytic cycle proteins of HHV-8 encoded by open reading frame 8 (ORF 8; glycoprotein B homolog of Epstein-Barr virus), ORF 22 (gH homolog), ORF 25 (major capsid protein homolog), ORF 26 (a minor capsid protein homolog), or ORF 57 (an early protein homolog), in association with increases in serum antibody titers and appearance of HHV-8 DNA in blood mononuclear cells. CD8(+) T-cell responses to HHV-8 decreased by 2 to 3 years after primary infection. This antiviral T-cell response may control initial HHV-8 infection and prevent development of disease.

Sequence requirements for interaction of human herpesvirus 7 origin binding protein with the origin of lytic replication.

As do human herpesvirus 6 variants A and B (HHV-6A and -6B), HHV-7 encodes a homolog of the alphaherpesvirus origin binding protein (OBP), which binds at sites in the origin of lytic replication (oriLyt) to initiate DNA replication. In this study, we sought to characterize the interaction of the HHV-7 OBP (OBP(H7)) with its cognate sites in the 600-bp HHV-7 oriLyt. We expressed the carboxyl-terminal domain of OBP(H7) and found that amino acids 484 to 787 of OBP(H7) were sufficient for DNA binding activity by electrophoretic mobility shift analysis. OBP(H7) has one high-affinity binding site (OBP-2) located on one flank of an AT-rich spacer element and a low-affinity site (OBP-1) on the other. This is in contrast to the HHV-6B OBP (OBP(H6B)), which binds with similar affinity to its two cognate OBP sites in the HHV-6B oriLyt. The minimal recognition element of the OBP-2 site was mapped to a 14-bp sequence. The OBP(H7) consensus recognition sequence of the 9-bp core, BRTYCWCCT (where B is a T, G, or C; R is a G or A; Y is a T or C; and W is a T or A), overlaps with the OBP(H6B) consensus YGWYCWCCY and establishes YCWCC as the roseolovirus OBP core recognition sequence. Heteroduplex analysis suggests that OBP(H7) interacts along one face of the DNA helix, with the major groove, as do OBP(H6B) and herpes simplex virus type 1 OBP. Together, these results illustrate both conserved and divergent DNA binding properties between OBP(H7) and OBP(H6B).

Blood-borne and sexual transmission of human herpesvirus 8 in women with or at risk for human immunodeficiency virus infection.

BACKGROUND: Human herpesvirus 8 (HHV-8), the causal agent of Kaposi's sarcoma, is transmitted sexually among homosexual men, but little is known of its transmission among women. Although HHV-8 has been detected in blood, there has been no clear evidence of blood-borne transmission. METHODS: We identified risk factors for HHV-8 infection in 1295 women in Baltimore, Detroit, New York, and Providence, Rhode Island, who reported high-risk sexual behavior or drug use. HHV-8 serologic studies were performed with two enzyme-linked immunosorbent assays. RESULTS: In univariate analyses, HHV-8 was associated with black race, Hispanic ethnic background, a lower level of education, and infection with syphilis, the human immunodeficiency virus (HIV), hepatitis B virus (HBV), or hepatitis C virus (HCV). The risk of seropositivity for HHV-8 increased with the frequency of injection-drug use (P<0.001); HHV-8 seroprevalence among the women who used drugs daily was three times that among women who never injected drugs. Among the women with a low risk of sexual transmission, HHV-8 seroprevalence was 0 percent in those who had never injected drugs and 36 percent in those who had injected drugs (P<0.001). However, injection-drug use was linked less strongly to HHV-8 infection than to infection with HBV or HCV. In a multivariate analysis, independent predictors of HHV-8 seropositivity included HIV infection (odds ratio, 1.6; 95 percent confidence interval, 1.1 to 2.2), syphilis infection (odds ratio, 1.8; 95 percent confidence interval, 1.1 to 2.8), and daily injection-drug use (odds ratio, 3.2; 95 percent confidence interval, 1.4 to 7.6). CONCLUSIONS: Both injection-drug use and correlates of sexual activity were risk factors for HHV-8 infection in the women studied. The independent association of HHV-8 infection with injection-drug use suggests that HHV-8 is transmitted through needle sharing, albeit less efficiently than HBV, HCV, or HIV.

CD8+ cytotoxic T lymphocyte responses to lytic proteins of human herpes virus 8 in human immunodeficiency virus type 1-infected and -uninfected individuals.

T cell immunity to lytic proteins of herpesviruses is important in host control of infection. We have characterized the cytotoxic T lymphocyte (CTL) response to 5 human herpesvirus 8 (HHV-8) homologues of lytic proteins in HHV-8-seropositive individuals. HLA class I-restricted, CD8(+) CTL responses to >/=1 HHV-8 lytic protein were detected in all 14 HHV-8-seropositive study subjects tested, with or without human immunodeficiency virus type 1 (HIV-1) infection, but not in any of 5 HHV-8-seronegative individuals. Seven of these study subjects with both HHV-8 and HIV-1 infection had greater anti-CTL reactivity to glycoprotein H (open-reading frame 22) than did the 7 study subjects infected only with HHV-8. Moreover, there was a strong, inverse correlation between HIV-1 load and glycoprotein H-specific CTL lysis in the study subjects infected with both viruses. CTL reactivity to HHV-8 lytic proteins may be involved in host control of HHV-8-related diseases, such as Kaposi's sarcoma.

Human herpesviruses 6 and 7 in chronic fatigue syndrome: a case-control study.

We conducted this study to determine whether infection with human herpesvirus (HHV) 6A, HHV-6B, or HHV-7 differed between patients with chronic fatigue syndrome and control subjects. We recruited 26 patients and 52 nonfatigued matched control subjects from Atlanta. Serum samples were tested by enzyme immunoassay for seroreactivity to HHV-6, and all were seropositive. Lymphocyte specimens were cocultivated with cord blood lymphocytes and assayed for HHV-6 and HHV-7; neither virus was isolated. Finally, lymphocytes were tested by use of 3 polymerase chain reaction methods for HHV-6A, HHV-6B, and HHV-7 DNA. HHV-6A or HHV-6B DNA was detected in 17 (22.4%) of 76 samples, and there were no significant differences (by matched analyses) between patients (3 [11.5%] of 26) and control subjects (14 [28%] of 50). HHV-7 DNA was detected in 14 subjects, and although control subjects (12 [24%]) were more likely than patients (2 [7.7%]) to be positive, the difference was not statistically significant. We found no evidence that active or latent infection with HHV-6A, HHV-6B, HHV-7, or any combination these 3 HHVs is associated with chronic fatigue syndrome.

Comparison of serologic assays and PCR for diagnosis of human herpesvirus 8 infection.

A variety of assays for the diagnosis human herpesvirus 8 (HHV-8) infection have been reported. We compared several such assays with a panel of 88 specimens from human immunodeficiency virus (HIV)-infected patients with Kaposi's sarcoma (KS) (current-KS patients; n = 30), HIV-infected patients who later developed KS (later-KS patients; n = 13), HIV-infected patients without KS (no-KS patients; n = 25), and healthy blood donors (n = 20). PCR assays were also performed with purified peripheral blood mononuclear cells (PBMCs) to confirm positive serologic test results. The order of sensitivity of the serologic assays (most to least) in detecting HHV-8 infection in current-KS patients was the mouse monoclonal antibody-enhanced immunofluorescence assay (MIFA) for lytic antigen (97%), the orfK8.1 peptide enzyme immunoassay (EIA) (87%), the orf65 peptide EIA (87%), MIFA for latent antigen (83%), the Advanced Biotechnologies, Inc., EIA (80%), and the orf65 immunoblot assay (80%). Combination of the results of the two peptide EIAs (combined peptide EIAs) increased the sensitivity to 93%. For detection of infection in later-KS patients, the MIFA for lytic antigen (100%), the orfK8.1 peptide EIA (85%), and combined peptide EIAs (92%) were the most sensitive. Smaller percentages of no-KS patients were found to be positive (16 to 56%). Most positive specimens from the current-KS and later-KS groups were positive by multiple assays, while positive specimens from the no-KS group tended to be positive only by a single assay. PCR with PBMCs for portions of the HHV-8 orf65 and gB genes were positive for less than half of current-KS and later-KS patients and even fewer of the no-KS patients. The concordance between serologic assays was high. We propose screening by the combined peptide EIAs. For specimens that test weakly positive, we recommend that MIFA for lytic antigen be done. A positive result with a titer of >/=1:40 would be called HHV-8 positive. A negative or low titer would be called HHV-8 negative. If a population has a high percentage of persons who test positive by the combined peptide EIAs, then a MIFA could be performed with the negative specimens to determine if any positive specimens are being missed. Alternatively, if a population has a low percentage that test positive, then a MIFA could be performed with a subset of the negative specimens for the same reason. As described above, only a titer of >/=1:40 would be considered HHV-8 positive.

New immunofluorescence assays for detection of Human herpesvirus 8-specific antibodies.

Several assays have been developed for detection of immunoglobulin G antibodies to Human herpesvirus 8 (HHV-8), including immunofluorescence assays (IFAs) and enzyme-linked immunosorbent assays (ELISAs). However, the specificity and sensitivity of these assays are not completely defined due to the lack of a "gold standard." Although IFAs based on primary effusion lymphoma (PEL) cell lines are used widely, the assays can be confounded by nonspecific reactions against cellular components and potential cross-reaction with antibodies against other herpesviruses. To provide more reliable IFAs, we established recombinant Semliki Forest viruses (rSFVs) expressing the HHV-8-specific proteins ORF73 and K8.1 and used BHK-21 cells infected with these rSFVs for IFA (ORF73-IFA and K8.1-IFA). Expression of the HHV-8-specific proteins at very high levels by the rSFV system allowed easy scoring for IFA and thereby increased specificity. The rSFV system also allowed detection of antibodies against glycosylation-dependent epitopes of K8.1. Titers measured by rSFV-based IFAs and PEL-based IFAs correlated well (correlation coefficients of >0.9), and concordances of seroreactivities between rSFV-based and PEL-based IFAs were >97% (kappa > 0.93). K8.1-IFA was more sensitive than either ORF73-IFA or peptide ELISAs. Using PEL-based lytic IFA as a reference assay, the sensitivity and specificity of K8.1-IFA were estimated to be 94 and 100%, respectively. HHV-8 prevalences determined by K8.1-IFA among the human immunodeficiency virus (HIV)-positive (HIV(+)) Kaposi's sarcoma (KS) patients, HIV(+) KS(-) patients, and healthy controls were 100, 65, and 6.7%, respectively, which were consistent with prior reports. Therefore, our rSFV-based IFAs may provide a specific and sensitive method for use in epidemiology studies. In addition, they will provide a basis for further development of diagnostic tests for HHV-8 infection.

Human herpesvirus 8 and Kaposi's sarcoma in persons infected with human immunodeficiency virus.

Human herpesvirus 8 (HHV-8) was detected in 1994 in biopsies of Kaposi's sarcoma (KS) tissues from a patient with AIDS. The evidence that HHV-8 infection is etiologically related to the development of KS is compelling. Essentially all patients with KS of any epidemiological type have serological evidence of HHV-8 infection. About 30%-40% of homosexual men infected with human immunodeficiency virus (HIV) are seropositive for HHV-8; rates are lower (<10%) among HIV-infected women, hemophiliacs, and injection drug users. Among homosexual men, the probability of HHV-8-seropositivity is directly proportional to the numbers of previous male sex partners, which suggets that HHV-8 is a sexually transmitted infection. Although HHV-8 is detectable in saliva and semen, the exact mechanism of transmission is not known. A reduction in KS incidence among patients with AIDS in the 1980s has been attributed to lower rates of HHV-8 transmission that resulted from alterations in sexual behaviors. A further decline in KS incidence has been associated with the use of antiretroviral therapy. Antiretroviral therapy to control HIV replication and to limit the associated immunodeficiency is currently the best approach for preventing KS in persons infected with HHV-8 and HIV.

U94, the human herpesvirus 6 homolog of the parvovirus nonstructural gene, is highly conserved among isolates and is expressed at low mRNA levels as a spliced transcript.

Human herpesvirus 6 variants A and B (HHV-6A and HHV-6B, respectively) encode homologs (U94) of the parvovirus nonstructural gene, ns1 or rep. Here we describe the HHV-6B homolog and analyze its genetic heterogeneity and transcription. U94 nucleotide and amino acid sequences differ by approximately 3.5% and 2.5%, respectively, between HHV-6A and HHV-6B. Among a collection of 17 clinically and geographically disparate HHV-6 isolates, intravariant nucleotide and amino acid sequence divergence was less than 0.6% and 0.2%, respectively; all 13 HHV-6B isolates had identical amino acid sequences. The U94 transcript is spliced to remove a 2.6-kb intron and is expressed at very low levels relative to other HHV-6B genes, reaching approximately 10 copies per cell 3 days after infection. The mRNA has several small AUG-initiated open reading frames upstream of the U94 open reading frame, a hallmark of proteins expressed at low levels. Consistent with this, the U94-encoded protein was immunologically undetectable in HHV-6B-infected cells. The high degree of sequence conservation suggests that the gene function is nearly intolerant of sequence variation. The low abundance of U94 transcripts and the presence of encoded inefficient translation initiation suggest that the U94 protein may be required only in small amounts during infection.

Occurrence of primary cancers in association with multiple myeloma and Kaposi's sarcoma in the United States, 1973-1995.

The causes of multiple myeloma (MM) are obscure, but a laboratory association was recently reported between MM and human herpesvirus 8 (HHV-8), the probable etiologic agent of Kaposi's sarcoma (KS). Although there has been some additional laboratory corroboration, most laboratory studies have found no association between MM and HHV-8. We looked for indirect evidence of an HHV-8/MM association by evaluating whether MM is associated with KS in the United States. Cancer incidence and survival data were obtained from the Surveillance, Epidemiology, and End Results (SEER) program for the years 1973-1995. Strength of association was assessed for a number of cancer pairs using standardized incidence ratios (SIRs) (observed/expected double cancers). KS was strongly associated (SIR > 15) with non-Hodgkin's lymphoma and anal cancer, was modestly associated (2.5 < SIR < 5.5) with MM, Hodgkin's disease, and testicular cancer and was not significantly associated with 6 other cancers. Besides being associated with KS, MM was weakly associated (1.7 < SIR < 2.3) with Hodgkin's disease and testicular cancer. The SIRs for 7 other cancers paired with MM were all less than 1.6. Factors that might be responsible for the KS/MM association include MM-related immune dysfunction, HIV and HHV-8, but the role of these factors cannot be directly assessed through the SEER database. Although we cannot rule out the possibility that HHV-8 is linked to a small proportion of MM cases, the modest KS/MM association is evidence that the vast majority of MM cases are not likely to be associated with HHV-8.

Glycoprotein B of human herpesvirus 8 is a component of the virion in a cleaved form composed of amino- and carboxyl-terminal fragments.

Human herpesvirus 8 (HHV-8) or Kaposi's sarcoma-associated herpesvirus (KSHV) is the only known human member of the Rhadinovirus genus of the gammaherpesvirus subfamily. Antibodies against peptides representing portions of the amino- and carboxyl-termini of HHV-8 gB were produced and used to detect gB expression in Vero cells transfected with the gB gene, in the HHV-8-harboring cell line, BCBL-1, and in purified virions. Expression of gB was detected in approximately 3% of uninduced BCBL-1 cells, while up to 30% of the cells expressed gB after 12-O-tetradecanoylphorbol-13-acetate (TPA) induction of virus replication. Indirect immunofluorescence assays and confocal microscopy showed that gB was distributed throughout the cytoplasm of BCBL-1 cells and transfected Vero cells. Immunoblot analyses of virion preparations revealed the presence of full-length as well as two smaller than full-length gB-derived species corresponding to the amino- and carboxy-terminal portions of gB, respectively. Biochemical analysis of the gB carbohydrate moieties using glycosylation inhibitors revealed that gB contained N-linked oligosaccharides of the high-mannose type, characteristic of precursor carbohydrate chains added in the endoplasmic reticulum.

Antiviral screening assays for human herpesviruses 6 and 7.

Human herpesviruses 6 and 7 are ubiquitous herpesviruses that normally infect their hosts early in life. There are two variant groups of human herpesvirus 6 (HHV-6): variants A (HHV-6A) and B (HHV-6B). Variant A has not been unambiguously associated with a specific disease but may contribute to disease in immunocompromised patients; variant B is the major etiologic agent of roseola (roseola infantum or exanthem subitum) and other febrile illnesses of young children, and has been associated with disease in immunocompromised patients. HHV-6B is frequently present in plaque regions in the brains of multiple sclerosis patients, although an etiologic association has not been proven. Human herpesvirus 7 (HHV-7) has been associated with some cases of roseola. The clinical spectrum of these viruses remains to be completely defined. Braun et al. (1) recently described three clinical scenarios that might warrant the use of antivirals to treat HHV-6 infections: (1) transplant recipients with idiopathic pneumonitis (2), multiple sclerosis patients, and (3) patients with HHV-6-associated encephalitis. For HHV-7, cases of neurologic involvement during primary infection might warrant investigation (2).