Human cytomegalovirus multiple-strain infections and viral population diversity in haematopoietic stem cell transplant recipients analysed by high-throughput sequencing.

Human cytomegalovirus (HCMV) is an important opportunistic pathogen in allogeneic haematopoietic stem cell transplant (HSCT) recipients. High-throughput sequencing of target-enriched libraries was performed to characterise the diversity of HCMV strains present in this high-risk group. Forty-four HCMV-DNA-positive plasma specimens (median viral input load 321 IU per library) collected at defined time points from 23 HSCT recipients within 80 days of transplantation were sequenced. The genotype distribution for 12 hypervariable HCMV genes and the number of HCMV strains present (i.e. single- vs. multiple-strain infection) were determined for 29 samples from 16 recipients. Multiple-strain infection was observed in seven of these 16 recipients, and five of these seven recipients had the donor (D)/recipient (R) HCMV-serostatus combination D + R + . A very broad range of genotypes was detected, with an intrahost composition that was generally stable over time. Multiple-strain infection was not associated with particular virological or clinical features, such as altered levels or duration of antigenaemia, development of acute graft-versus-host disease or increased mortality. In conclusion, despite relatively low viral plasma loads, a high frequency of multiple-strain HCMV infection and a high strain complexity were demonstrated in systematically collected clinical samples from this cohort early after HSCT. However, robust evaluation of the pathogenic role of intrahost viral diversity and multiple-strain infection will require studies enrolling larger numbers of recipients.

Neuropsychiatric disease relevance of circulating anti-NMDA receptor autoantibodies depends on blood-brain barrier integrity.

In 2007, a multifaceted syndrome, associated with anti-NMDA receptor autoantibodies (NMDAR-AB) of immunoglobulin-G isotype, has been described, which variably consists of psychosis, epilepsy, cognitive decline and extrapyramidal symptoms. Prevalence and significance of NMDAR-AB in complex neuropsychiatric disease versus health, however, have remained unclear. We tested sera of 2817 subjects (1325 healthy, 1081 schizophrenic, 263 Parkinson and 148 affective-disorder subjects) for presence of NMDAR-AB, conducted a genome-wide genetic association study, comparing AB carriers versus non-carriers, and assessed their influenza AB status. For mechanistic insight and documentation of AB functionality, in vivo experiments involving mice with deficient blood-brain barrier (ApoE(-/-)) and in vitro endocytosis assays in primary cortical neurons were performed. In 10.5% of subjects, NMDAR-AB (NR1 subunit) of any immunoglobulin isotype were detected, with no difference in seroprevalence, titer or in vitro functionality between patients and healthy controls. Administration of extracted human serum to mice influenced basal and MK-801-induced activity in the open field only in ApoE(-/-) mice injected with NMDAR-AB-positive serum but not in respective controls. Seropositive schizophrenic patients with a history of neurotrauma or birth complications, indicating an at least temporarily compromised blood-brain barrier, had more neurological abnormalities than seronegative patients with comparable history. A common genetic variant (rs524991, P=6.15E-08) as well as past influenza A (P=0.024) or B (P=0.006) infection were identified as predisposing factors for NMDAR-AB seropositivity. The >10% overall seroprevalence of NMDAR-AB of both healthy individuals and patients is unexpectedly high. Clinical significance, however, apparently depends on association with past or present perturbations of blood-brain barrier function.

Recruitment of the tumour suppressor protein p73 by Kaposi's Sarcoma Herpesvirus latent nuclear antigen contributes to the survival of primary effusion lymphoma cells.

Kaposi's Sarcoma Herpesvirus (KSHV) is the causative agent of Kaposi's Sarcoma (KS) and two rare lymphoproliferative disorders, primary effusion lymphoma (PEL) and the plasmablastic variant of multicentric Castleman's disease (MCD). The KSHV latency-associated nuclear antigen-1 (LANA), required for the replication and maintenance of latent viral episomal DNA, is involved in the transcriptional regulation of viral and cellular genes and interacts with different cellular proteins, including the tumour suppressor p53. Here, we report that LANA also recruits the p53-related nuclear transcription factor p73, which influences cellular processes like DNA damage response, cell cycle progression and apoptosis. Both the full-length isoform TAp73α, as well as its dominant negative regulator ΔNp73α, interact with LANA. LANA affects TAp73α stability and sub-nuclear localisation, as well as TAp73α-mediated transcriptional activation of target genes. We observed that the small-molecule inhibitor Nutlin-3, which disrupts the interaction of p53 and p73 with MDM2, induces apoptotic cell death in p53 wild-type, as well as p53-mutant PEL cell lines, suggesting a possible involvement of p73. The small-molecule RETRA, which activates p73 in the context of mutant p53, leads to the induction of apoptosis in p53-mutant PEL cell lines. RNAi-mediated knockdown of p73 confirmed that these effects depend on the presence of the p73 protein. Furthermore, both Nutlin-3 and RETRA disrupt the LANA-p73 interaction in different PEL cell lines. These results suggest that LANA modulates p73 function and that the LANA-p73 interaction may represent a therapeutic target to interfere with the survival of latently KSHV-infected cells.

Kaposi's sarcoma-associated herpesvirus infection of endothelial cells inhibits neutrophil recruitment through an interleukin-6-dependent mechanism: a new paradigm for viral immune evasion.

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent of Kaposi's sarcoma (KS), an endothelial cell (EC) neoplasm characterized by dysregulated angiogenesis and inflammation. KSHV infection of EC causes production of proinflammatory mediators, regarded as possible initiators of the substantial mononuclear leukocyte recruitment seen in KS. Conversely, KSHV immune evasion strategies exist, such as degradation of EC leukocyte adhesion receptors by viral proteins. Here, we report the effects of KSHV infection of primary EC on recruitment of flowing leukocytes. Infection did not initiate adhesion of any leukocyte subset per se. However, on cytokine-stimulated EC, KSHV specifically inhibited neutrophil, but not PBL or monocyte, transmigration, an observation consistent with the inflammatory cell profile found in KS lesions in vivo. This inhibition could be recapitulated on uninfected EC using supernatant from infected cultures. These supernatants contained elevated levels of human interleukin 6 (hIL-6), and both the KSHV- and the supernatant-induced inhibitions of neutrophil transmigration were abrogated in the presence of a hIL-6 neutralizing antibody. Furthermore, preconditioning of EC with hIL-6 mimicked the effect of KSHV. Using RNA interference (RNAi), we show that upregulation of suppressor of cytokine signaling 3 (SOCS3) was necessary for this effect of hIL-6. These studies reveal a novel paracrine mode of KSHV immune evasion, resulting in reduced recruitment of neutrophils, a cell type whose antiviral and antitumor roles are becoming increasingly appreciated. Moreover, the findings have implications for our understanding of the contribution of hIL-6 to the pathogenesis of other inflammatory disorders and tumors in which this cytokine is abundant.

Incidence and impact of herpes simplex and cytomegalovirus detection in the respiratory tract after lung transplantation.

Herpesvirus infections cause morbidity in lung transplant recipients. The study was conducted to investigate the incidence and impact of herpes simplex virus (HSV) and cytomegalovirus (CMV) detection in the respiratory tract (RT) of lung and heart-lung transplant recipients (LTR) during the postoperative phase. In a prospective cohort study, 91 LTR having at least 1 nasopharyngeal swab (NPS) sent for virus diagnostics were monitored for CMV and HSV detection in NPS during their post-transplant hospital stay on cardiothoracic surgery wards (median 4 weeks) by direct immunofluorescence testing for HSV, virus culture, and CMV and HSV polymerase chain reaction (PCR). Bronchoalveolar lavages (BALs) were analyzed with the same protocol except that HSV PCR was only performed on request. Risk factor analysis for the outcome '90-day mortality' was performed. Fifteen LTR had virus detection in NPS (16.5%): 9 had CMV, 5 had HSV, and 1 had both CMV and HSV. Four of 84 LTR had CMV detection in BAL (4.8%). Absence of CMV detection in NPS had a negative predictive value of 98.8% for absence of CMV detection in BAL. HSV DNA detection in NPS, especially if detected within 8 days after transplantation, was associated with 90-day mortality. In conclusion, detection of herpesviruses in the RT was clinically relevant and frequent, despite antiviral prophylaxis.

The impact of preexisting or acquired Kaposi sarcoma herpesvirus infection in kidney transplant recipients on morbidity and survival.

The impact of preexisting or acquired Kaposi sarcoma herpesvirus (KSHV) infection in kidney transplant recipients was evaluated in a prospective study. Serum collected from kidney donors and recipients before transplantation were tested for antibodies against KSHV latent nuclear antigen. Three groups of recipients were defined: group A (KSHV+), group B (KSHV-, KSHV+ donor) and group C (donor and recipient KSHV-). Blood was collected from recipients, every 3 months for 3 years, for KSHV viremia (groups A and B), quantitative (group A) and qualitative serology (group B). Data of group C recipients were extracted from a French database. The prevalence of KSHV antibodies was 1.1% in donors and 3.2% in recipients. There were respectively 161, 64 and 4744 recipients in groups A, B and C. In group A, 13% developed Kaposi's sarcoma (KS). Age >53.5 years (p = 0.025) and black skin (p = 0.0054) were associated with KS development. In group B, three recipients developed clinical manifestations related to KSHV infection. There was no difference in terms of survival and graft loss between the three groups. In conclusion, although kidney recipients should be aware of the additional risk of KSHV morbidity, KSHV+ recipients should not be systematically excluded from kidney transplantation.

Rapid quantitative PCR assays for the simultaneous detection of herpes simplex virus, varicella zoster virus, cytomegalovirus, Epstein-Barr virus, and human herpesvirus 6 DNA in blood and other clinical specimens.

Rapid diagnosis of human herpesvirus primary infections or reactivations is facilitated by quantitative PCRs. Quantitative PCR assays with a standard thermal cycling profile permitting simultaneous detection of herpes simplex virus (HSV), varicella zoster virus (VZV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human herpesvirus 6 (HHV6) DNA were developed and validated for diagnostic use. High specificity and sensitivity were achieved and the new PCR assays correlated well with commercial PCR assays. Twenty two thousand eight hundred sixty eight PCR tests were undertaken on specimens obtained from immunosuppressed patients. DNAemia was frequent with EBV (43.5%), HHV6 (32.4%), CMV (12.8%), and VZV (12.9%). As already described for EBV and CMV, high virus loads of HHV6 and VZV were associated with clinical symptoms and poor clinical outcome, for example, three of four patients with VZV virus loads >10(5) copies/ml died. A high proportion of lower respiratory specimens was positive for EBV- (38.8%), HHV6- (29.4%), and CMV-DNA (18.2%). For CMV, infection was confirmed in 66.7% of patients by virus isolation or positive pp65 antigenaemia. Differentiation of HHV6A, -B and HSV-1, -2 by melting curve analysis revealed that HHV6A and HSV-2 represented only 1.8% and 3.3% of all positive specimens, respectively. In conclusion, these results indicate significant improvements for the early diagnosis of primary infections or reactivations of five human herpesviruses especially in immunosuppressed patients. Detection of coinfections with multiple herpesviruses is facilitated. Quantitative results enable monitoring of virus load during antiviral therapy. A standard thermal cycling profile permits time and cost effective use in a routine diagnostic setting.

Adverse effects of rabies pre- and postexposure prophylaxis in 290 health-care-workers exposed to a rabies infected organ donor or transplant recipients.

The recent unfortunate rabies transmissions through solid organ transplants of an infected donor in Germany required the initiation of a vaccination program to protect health care workers (HCWs) with close contact to rabies-infected patients. A systematic follow-up of adverse effects was initiated. Rabies postexposure prophylaxis (PEP) was started in 269 HCWs at four German hospitals. Pre-exposure prophylaxis (PreEP) was administered to 74 HCWs caring for an already diagnosed rabies patient. At each vaccination date, HCWs were interviewed for symptoms possibly representing adverse effects. Adverse effects of PEP and PrePEP were compared. Out of 269 HCWs, 216 were included for the investigation of adverse effects. Of these 216 HCWs, 114 (53%) individuals developed at least one systemic adverse effect. Incidences of tiredness (30.6%), malaise (26.4%), headache (26.9%), dizziness (14.8%), and chills (13.0%) declined in the course of PEP (p < 0.05), whereas incidences of fever (7.4%), paraesthesias (7.9%), arthralgias (1.9%), myalgias (4.2%), nausea (9.3%), diarrheas (2.8%) and vomiting (1.4%) did not. In 11 (5.1%) HCWs PEP was discontinued mostly due to adverse reactions (four suffered strong headaches, two HCWs meningeal irritations, two chills, one paraesthesia, one malaise, and one a rush). Systemic effects of PEP or PreEP did not differ significantly. Despite relatively high incidences of moderate severe adverse reactions rabies PEP is safe. Strong headache, tiredness, dizziness, and paraesthesias are the most important postvaccinal symptoms. Vaccinees suffering from adverse effects of PEP must be strongly encouraged to complete PEP, as it is to date the only protection against fatal rabies.

Increase in infectivity of targeted Moloney murine leukemia virus-based gene-delivery vectors through lowering the threshold for fusion.

Many research groups have developed targeted vectors for gene therapy based on Moloney murine leukemia virus (MoMLV). Despite proper binding of the targeted vector to the target molecule, little or no infectivity of human cells expressing the target molecule has been achieved in most studies. One of the reasons for this lack of infectivity may be steric hindrance within the targeted envelope glycoprotein (Env), impeding the conformational changes required for fusion and infection. Here, attempts were made to solve this problem by mutating key residues within Env of two targeted MoMLV-based vectors, MoMLV-E-Sel and MoMLV-FBP. Selection of key residues was based on an Env with reduced threshold for fusion, that of the CD4-independent human immunodeficiency virus type 2 isolate ROD/B. It was shown here that vectors bearing MoMLV-FBP Env with a V512M substitution had higher titres and faster kinetics of entry than vectors bearing parental targeted Env proteins. This could be due to the partial release of steric constraints that result in an Env with a reduced threshold for fusion.

Insertion of targeting domains into the envelope glycoprotein of Moloney murine leukemia virus (MoMLV)-based vectors modulates the route of mCAT-1-mediated viral entry.

Several groups have inserted targeting domains into the envelope glycoprotein (Env) of Moloney murine leukemia virus (MoMLV) in an attempt to produce targeted retroviral vectors for human gene therapy. While binding of these modified Envs to the target molecule expressed on the surface of human cells was observed, specific high-titer infection of human cells expressing the target molecule was not achieved. Here we investigate the initial steps in the entry process of targeted MoMLV vectors both in murine and human cells expressing the MoMLV receptor, the mouse cationic amino acid transporter-1 (mCAT-1). We show that insertion of a small ligand targeted to E-selectin and of a single chain antibody (scFv) targeted to folate-binding protein (FBP) into the N-terminus of MoMLV Env results in the reduction of the infectivity and the kinetics of entry of the MoMLV vectors. The use of soluble receptor-binding domain (sRBD), bafilomycin A1 (BafA1) and methyl-beta-cyclodextrin (MbetaC) increase the infectivity of the MoMLV vectors targeted to FBP (MoMLV-FBP) suggesting that the scFv targeted to FBP increases the threshold for fusion and might re-route entry of the targeted MoMLV-FBP vector towards an endocytic, non-productive pathway.

Reduced seroprevalence of Kaposi's sarcoma-associated herpesvirus (KSHV), human herpesvirus 8 (HHV8), related to suppression of Anopheles density in Italy.

In two formerly malarious parts of Italy, age-related seroprevalence rates of Kaposi's sarcoma-associated herpesvirus [human herpesvirus 8 (KSHV/HHV8)] were determined from local blood donors and correlated with periods of vector control during anti-malaria campaigns. In Veneto, decreased KSHV/HHV8 seroprevalence in the 1951-1955 birth cohort coincides with the peak of DDT house-spraying. In Sardinia, where larviciding augmented indoor DDT-spraying, a significant drop of KSHV/HHV8 seroprevalence between 1945 and 1950 and 1951-1955 birth cohorts (P = 0.0046) coincides with suppression of the malaria vector Anopheles labranchiae Falleroni (Diptera: Culicidae). These results are consistent with age-related association between KSHV/HHV8 seroprevalence rates in native/resident populations and the density of malaria vectors in Veneto and Sardinia. This example supports our 'promoter arthropod' hypothesis on the role of haematophagous insects [putatively blackflies (Simuliidae), sandflies (Phlebotominae) and biting midges (Ceratopogonidae), as well as mosquitoes] when their bites induce hypersensitivity and immunosuppression, potentiate KSHV/HHV8 transmission via human saliva (when insect bite lesions are licked by another person whose saliva carries the virus) and may facilitate Kaposi's sarcoma.

Kaposi's sarcoma and human herpesvirus 8 infection do not protect HIV-1 infected homosexual men from AIDS dementia complex.

OBJECTIVE: To examine the association between Kaposi's sarcoma (KS), human herpes virus 8 (HHV8) and AIDS dementia complex (ADC). DESIGN: A total of 599 HIV-1 infected homosexual men participated in a prospective cohort study (Amsterdam, 1984-1996). METHODS: The risk for ADC in patients with prior KS or HHV8 infection was estimated using the Cox proportional hazards method with adjustments for antiretroviral medication and low CD4 cell counts. RESULTS: Of the 599 participants, 290 (48.4%) had HHV8 antibodies, 99 (16.5%) had KS and 30 (5.0%) had ADC. ADC was diagnosed in 5.2% of participants with KS and 5.0% of those without KS, and in 4.8% of HHV8 seropositive compared to 5.2% seronegative individuals and thus was not associated with KS or HHV8 infection. Using a time-dependent Cox proportional hazards analysis with the date of KS as risk factor, the risk for ADC was 2.7 [95% confidence interval (CI), 0.92-7.96; P = 0.07) and when only definite ADC was considered it was 3.5 (95% CI, 1.00-12.26;P = 0.05). After adjusting for decreases in CD4 cell count and use of medication, the hazards ratio for participants with KS to develop ADC was 2.0 (95% CI, 0.66-5.77; P = 0.23) and 2.6 (95% CI, 0.73-9.12; P = 0.14), respectively. HHV8 seropositivity, adjusted for the same variables, showed a risk for ADC of 0.85 (95% CI, 0.41-1.77;P = 0.66) and for definite ADC 0.69 (95% CI, 0.27-1.73; P = 0.42). The expected neuroprotective effects of antiretroviral medication were observed. CONCLUSIONS: KS or HHV8 does not significantly influence the risk for developing ADC in a group with a uniform risk for developing KS therefore we recommend caution in searching for a KS-associated or HHV8-derived therapy for ADC.

Kaposi's sarcoma-associated herpesvirus serology in Europe and Uganda: multicentre study with multiple and novel assays.

A multicentre study was undertaken to define novel assays with increased inter-assay concordance, sensitivity, specificity and predictive value for serological diagnosis of human herpesvirus type 8 (HHV-8) infection. A total of 562 sera from European and Ugandan human immunodeficiency virus (HIV)-infected or uninfected individuals with or without Kaposi's sarcoma (KS) and blood donors were examined under code by 18 different assays in seven European laboratories. Sera from KS patients and all non-KS sera found positive by at least 70%, 80%, or 90% of the assays were considered "true positive." The validity of the assays was then evaluated by univariate logistic regression analysis. Two immunofluorescence assays (IFA) for detection of antibodies against HHV-8 lytic (Rlyt) or latent (LLANA) antigens and two enzyme-linked-immunosorbent assays (ELISA) (M2, EK8.1) for detection of antibodies against HHV-8 structural proteins were found to be highly concordant, specific, and sensitive, with odds ratios that indicated a high predictive value. When used together, the two IFA (Rlyt-LLANA) showed the best combination of sensitivity (89.1%) and specificity (94.9%). The performance of these assays indicate that they may be used for the clinical management of individuals at risk of developing HHV-8 associated tumours such as allograft recipients.

KSHV/HHV8-associated lymphoproliferations in the AIDS setting.

Kaposi's sarcoma-associated herpesvirus (KSHV) or human herpesvirus 8 (HHV8) is associated with two lymphoproliferative disorders in the AIDS setting, primary effusion lymphoma (PEL) and the plasma cell variant of multicentric Castleman's disease (MCD). In PEL, KSHV persists in a latent form in most lymphoma cells, although viral production has been seen infrequently. In MCD, the viral gene expression pattern is less restrictive, virus production appears to occur and to correlate with the severity of this disease. Several viral genes may contribute to the particular features of these two disorders: among them a viral homologue of interleukin 6 (vIL6) has attracted much attention and been shown to promote the growth of plasma cells. It is thought that its activity is important in the pathogenesis of both PEL and MCD. Other viral genes, in particular a D-type cyclin homologue, the latent nuclear antigen LANA, and one or more of the viral homologues of interferon regulatory factors (vIRFs) may also contribute. Although it is conceivable that viral infection per se could explain much, if not all, of the features of MCD, it is likely that additional genetic alterations play a role in the pathogenesis of PEL.

No increased human herpesvirus 8 seroprevalence in patients with HIV-associated non-Hodgkin's lymphoma.

Human herpesvirus 8 (HHV-8) is closely associated with Kaposi's sarcoma (KS), HIV-associated Castleman's disease, and primary effusion lymphoma. As a high frequency of non-Hodgkin's lymphoma (NHL) has been reported in patients with HIV-associated KS, we hypothesized that HHV-8 infection could be indirectly implicated in the pathogenesis of NHL. We assessed the prevalence of HHV-8 antibodies in 63 patients with NHL compared with 126 HIV-infected matched control patients without NHL. Serum samples from cases and controls were assayed for antibodies to HHV-8 lytic and latent antigens using an indirect immunofluorescence assay. In patients with concordant serologic results, HHV-8 antibodies were detected in 41.5% of the NHL cases and 37% of the controls. This absence of a significant difference in HHV-8 seroprevalence between cases and controls (p =.73) does not support a possible role for HHV-8 infection in the development of NHL in HIV-infected patients.

A prospective seroepidemiological study of human herpesvirus-8 infection and the risk of multiple myeloma.

Presence of the Human Herpesvirus 8 (HHV8) genome has been reported in the bone marrow of multiple myeloma (MM) patients. So far, serological studies of HHV8 and MM have been inconsistent but have not included prospective epidemiological studies. We evaluated whether HHV8 infection is associated with increased risk for MM in a prospective population-based study of 39 000 Finnish subjects who donated serum samples in the period 1968-72. Serum samples from 47 subjects who developed MM during a 23-year follow-up and 224 age, area of residence and sex-matched subjects who remained healthy over a similar follow-up period were evaluated for HHV8 antibodies at enrollment, as assayed both with an immunofluorescence assay (IFA) for lytic and latent HHV8 antigens and by Western blot (WB) with three recombinant HHV8 proteins (ORFs 65, 73 and K8.1A). HHV8 seropositivity for at least one HHV8 protein on WB was found in 7% of the Finnish population and was not associated with the risk of developing MM (Relative Risk (RR) = 0.89, Confidence Interval (CI): 0.25-3.25). HHV8 seropositivity for lytic and latent antigens in the IFA was found in 16% and 0.4% of the Finnish population and tended to associate with risk of MM (RR = 2.02, CI: 0.94-4.33 and RR = 10.00, CI: 0.91-110.29, respectively). In conclusion, no statistically significant evidence for an association between HHV8 infection and the risk of future MM was found.

A chimpanzee rhadinovirus sequence related to Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8: increased detection after HIV-1 infection in the absence of disease.

OBJECTIVE: To look for a virus related to Kaposi's sarcoma-associated herpesvirus (KSHV) or human herpesvirus 8 (HHV8) in chimpanzees and to investigate phylogenetic and biological similarities to KSHV. METHODS: Peripheral blood mononuclear cell (PBMC) DNA samples from chimpanzees (Pan troglodytes troglodytes) were screened with newly designed consensus oligonucleotide primers for the DNA polymerase gene of KSHV-related gamma2-herpesviruses (rhadinoviruses). Samples from HIV-1-infected and -uninfected chimpanzees were screened with virus-specific primers. Antibodies to KSHV structural and latent antigens were measured by immunofluorescence, enzyme-linked immunosorbent assay (ELISA) and Western blot. RESULTS: We identified 972 base pairs (bp) of a new viral DNA polymerase sequence with 81.6% (nucleotides) and 93.2% (protein) identity to that of KSHV/HHV8. It was detected in 15/37 (41%) animals experimentally infected with HIV-1, but only in one out of 30 uninfected animals (P<0.001). Antibodies were found by immunofluorescence to structural, but not latent, KSHV antigens in nearly all HIV-1-infected and uninfected animals. CONCLUSION: Like man and two other Old World primate species, chimpanzees harbour a virus closely related to KSHV/HHV8, termed Pan troglodytes rhadinovirus-1 (PtRV-1). Like KSHV, PtRV-1 is more easily detected by polymerase chain reaction (PCR) in the PBMC of HIV-1-infected than of HIV-1-uninfected individuals, suggesting increased viral load. Despite the close phylogenetic relationship and biological similarities between KSHV and PtRV-1, Kaposi's sarcoma (KS) has not been reported in HIV-1-infected chimpanzees. PtRV-1 may lack some of the pathogenic determinants of KSHV, or humans and chimpanzees may differ in how they control the infection with their respective rhadinoviruses.