Sequencing of Kaposi's Sarcoma Herpesvirus (KSHV) genomes from persons of diverse ethnicities and provenances with KSHV-associated diseases demonstrate multiple infections, novel polymorphisms, and low intra-host variance.

Recently published near full-length KSHV genomes from a Cameroon Kaposi sarcoma case-control study showed strong evidence of viral recombination and mixed infections, but no sequence variations associated with disease. Using the same methodology, an additional 102 KSHV genomes from 76 individuals with KSHV-associated diseases have been sequenced. Diagnoses comprise all KSHV-associated diseases (KAD): Kaposi sarcoma (KS), primary effusion lymphoma (PEL), KSHV-associated large cell lymphoma (KSHV-LCL), a type of multicentric Castleman disease (KSHV-MCD), and KSHV inflammatory cytokine syndrome (KICS). Participants originated from 22 different countries, providing the opportunity to obtain new near full-length sequences of a wide diversity of KSHV genomes. These include near full-length sequence of genomes with KSHV K1 subtypes A, B, C, and F as well as subtype E, for which no full sequence was previously available. High levels of recombination were observed. Fourteen individuals (18%) showed evidence of infection with multiple KSHV variants (from two to four unique genomes). Twenty-six comparisons of sequences, obtained from various sampling sites including PBMC, tissue biopsies, oral fluids, and effusions in the same participants, identified near complete genome conservation between different biological compartments. Polymorphisms were identified in coding and non-coding regions, including indels in the K3 and K15 genes and sequence inversions here reported for the first time. One such polymorphism in KSHV ORF46, specific to the KSHV K1 subtype E2, encoded a mutation in the leucine loop extension of the uracil DNA glycosylase that results in alteration of biochemical functions of this protein. This confirms that KSHV sequence variations can have functional consequences warranting further investigation. This study represents the largest and most diverse analysis of KSHV genome sequences to date among individuals with KAD and provides important new information on global KSHV genomics.

Systematic analysis of Kaposi's sarcoma (KS)-associated herpesvirus genomes from a KS case-control study in Cameroon: Evidence of dual infections but no association between viral sequence variation and KS risk.

In sub-Saharan Africa, Kaposi's sarcoma-associated herpesvirus (KSHV) is endemic, and Kaposi's sarcoma (KS) is a significant public health problem. Until recently, KSHV genotype analysis was performed using variable gene regions, representing a small fraction of the genome, and thus the contribution of sequence variation to viral transmission or pathogenesis are understudied. We performed near full-length KSHV genome sequence analysis on samples from 43 individuals selected from a large Cameroonian KS case-control study. KSHV genomes were obtained from 21 KS patients and 22 control participants. Phylogenetic analysis of the K1 region indicated the majority of sequences were A5 or B1 subtypes and all three K15 alleles were represented. Unique polymorphisms in the KSHV genome were observed including large gene deletions. We found evidence of multiple distinct KSHV genotypes in three individuals. Additionally, our analyses indicate that recombination is prevalent suggesting that multiple KSHV infections may not be uncommon overall. Most importantly, a detailed analysis of KSHV genomes from KS patients and control participants did not find a correlation between viral sequence variations and disease. Our study is the first to systematically compare near full-length KSHV genome sequences between KS cases and controls in the same endemic region to identify possible sequence variations associated with disease risk.

Gammaherpesvirus infection and malignant disease in rhesus macaques experimentally infected with SIV or SHIV.

Human gammaherpesviruses are associated with malignancies in HIV infected individuals; in macaques used in non-human primate models of HIV infection, gammaherpesvirus infections also occur. Limited data on prevalence and tumorigenicity of macaque gammaherpesviruses, mostly cross-sectional analyses of small series, are available. We comprehensively examine all three-rhesus macaque gammaherpesviruses -Rhesus rhadinovirus (RRV), Rhesus Lymphocryptovirus (RLCV) and Retroperitoneal Fibromatosis Herpesvirus (RFHV) in macaques experimentally infected with Simian Immunodeficiency Virus or Simian Human Immunodeficiency Virus (SIV/SHIV) in studies spanning 15 years at the AIDS and Cancer Virus Program of the Frederick National Laboratory for Cancer Research. We evaluated 18 animals with malignancies (16 lymphomas, one fibrosarcoma and one carcinoma) and 32 controls. We developed real time quantitative PCR assays for each gammaherpesvirus DNA viral load (VL) in malignant and non-tumor tissues; we also characterized the tumors using immunohistochemistry and in situ hybridization. Furthermore, we retrospectively quantified gammaherpesvirus DNA VL and SIV/SHIV RNA VL in longitudinally-collected PBMCs and plasma, respectively. One or more gammaherpesviruses were detected in 17 tumors; generally, one was predominant, and the relevant DNA VL in the tumor was very high compared to surrounding tissues. RLCV was predominant in tumors resembling diffuse large B cell lymphomas; in a Burkitt-like lymphoma, RRV was predominant; and in the fibrosarcoma, RFHV was predominant. Median RRV and RLCV PBMC DNA VL were significantly higher in cases than controls; SIV/SHIV VL and RLCV VL were independently associated with cancer. Local regressions showed that longitudinal VL patterns in cases and controls, from SIV infection to necropsy, differed for each gammaherpesvirus: while RFHV VL increased only slightly in all animals, RLCV and RRV VL increased significantly and continued to increase steeply in cases; in controls, VL flattened. In conclusion, the data suggest that gammaherpesviruses may play a significant role in tumorogenesis in macaques infected with immunodeficiency viruses.

Relationship between human leukocyte antigen alleles and risk of Kaposi's sarcoma in Cameroon.

Several studies published to date report associations between human leukocyte antigen (HLA) alleles and different types of Kaposi's Sarcoma (KS). However, there is little concordance between the HLA alleles identified and the populations studied. To test whether HLA alleles associate with KS in a Cameroonian case-control study, we performed high-resolution HLA typing in KSHV seropositive individuals. Among HIV-positive individuals, carriers of HLA-B*14:01 were at a significantly higher risk of AIDS-KS (p = 0.033). For HIV-negative patients, a gene-wise comparison of allele frequencies identified the HLA-B (p = 0.008) and -DQA1 (p = 0.002) loci as possible risk factors for endemic KS. Our study provides additional understanding of genetic determinants of KS and their implications in disease pathogenesis. Further validation of these findings is needed to define the functional relevance of these associations.

Sensitivity of the C-Terminal Nuclease Domain of Kaposi's Sarcoma-Associated Herpesvirus ORF29 to Two Classes of Active-Site Ligands.

Kaposi's sarcoma-associated herpesvirus (KSHV), the etiological agent of Kaposi's sarcoma, belongs to the Herpesviridae family, whose members employ a multicomponent terminase to resolve nonparametric viral DNA into genome-length units prior to their packaging. Homology modeling of the ORF29 C-terminal nuclease domain (pORF29C) and bacteriophage Sf6 gp2 have suggested an active site clustered with four acidic residues, D476, E550, D661, and D662, that collectively sequester the catalytic divalent metal (Mn2+) and also provided important insight into a potential inhibitor binding mode. Using this model, we have expressed, purified, and characterized the wild-type pORF29C and variants with substitutions at the proposed active-site residues. Differential scanning calorimetry demonstrated divalent metal-induced stabilization of wild-type (WT) and D661A pORF29C, consistent with which these two enzymes exhibited Mn2+-dependent nuclease activity, although the latter mutant was significantly impaired. Thermal stability of WT and D661A pORF29C was also enhanced by binding of an α-hydroxytropolone (α-HT) inhibitor shown to replace divalent metal at the active site. For the remaining mutants, thermal stability was unaffected by divalent metal or α-HT binding, supporting their role in catalysis. pORF29C nuclease activity was also inhibited by two classes of small molecules reported to inhibit HIV RNase H and integrase, both of which belong to the superfamily of nucleotidyltransferases. Finally, α-HT inhibition of KSHV replication suggests ORF29 nuclease function as an antiviral target that could be combined with latency-activating compounds as a shock-and-kill antiviral strategy.

Infant feeding and treatment practices could lead to enhanced transmission of Kaposi's sarcoma-associated herpesvirus (KSHV) and other orally shed infections via saliva, in rural south-western Uganda.

This qualitative sub-study investigated household practices affecting orally shed infections using Kaposi's sarcoma-associated herpesvirus (KSHV) as a focus. Participants enrolled from 50 households in rural south-western Uganda were followed monthly up to three times. At enrolment, in-depth interviews were completed, and venous blood collected. KSHV seropositivity was defined as anti-KSHV antibody detection to any of 25 antigens by multiplex bead-based assay. Mouthwash samples from every visit were tested by qPCR and KSHV shedders defined as individuals with KSHV DNA detected. At least one KSHV seropositive person was in 48/49(98%) households. Among those, 79% had 1+ KSHV shedders including 45% with 1+ always shedders and 92% with 1+ intermittent shedders, not mutually exclusively. All respondents reported feeding infants with pre-masticated hard food/fruits and testing food/tea temperature. Temperature was tested by tasting, pouring tea on their hand, or touching the cup to their cheek. Some cooled food/tea using a utensil or blowing over it. Food sharing amongst children and adults and using the same dish was common practice. To treat colic pain, carers/mothers reported chewing herbs and spitting into the child's mouth. Feeding and treatment practices did not vary by KSHV status. We identified potential KSHV transmission modes in rural Ugandan households.

Factors affecting Kaposi's sarcoma-associated herpesvirus transmission in rural Ugandan households, a longitudinal study.

Background: We report the impact of HIV infection within a household on oral Kaposi's sarcoma-associated herpesvirus (KSHV) shedding. Methods: We enrolled 469 individuals from 90 households. Mouthwash rinse samples collected at three monthly visits, were analyzed for KSHV DNA using quantitative polymerase chain reaction (qPCR). Generalized linear mixed effects logistic models were applied to analyze factors associated with KSHV ever shedding, and among shedders, always versus intermittent shedding. Linear mixed effects models were applied to models of KSHV viral loads. Intraclass correlation coefficients (ICCs) were calculated to assess the contribution of household-level factors to variations in shedding probabilities. Hotspot analyses of geospatial feature clusters were calculated using Getis-Ord Gi* statistic and visualized using inverse distance weighted interpolation. Results: Analyses included 340 KSHV seropositive individuals, aged 3 + years, with qPCR results from 89 households. Forty households had 1 + persons living with HIV (PLWH), while 49 had none. Among participants, 149(44%) were KSHV ever shedders. Of 140 who shed KSHV at two or more visits, 34(24%) were always shedders. Increasing number of KSHV seropositive household members was significantly associated with ever shedding [Odds ratio(OR) (95% Confidence Interval(95%CI)):1.14(1.03,1.26);p = 0.013]. Among KSHV shedders, a statistically significant age-related trend was identified with 10-19 years being more likely to be always shedders (type III test p = 0.039) and to have higher viral loads (type III test p = 0.027). In addition, higher viral loads were significantly associated with increasing number of household members [coefficient(95%CI):0.06(0.01,0.12);p = 0.042], increasing number of KSHV seropositive members [coefficient(95%CI):0.08(0.01,0.15);p = 0.021], and living in households with 1 + PLWH [coefficient(95%CI):0.51(0.04,0.98);p = 0.033]. Always shedders exhibited higher viral loads than intermittent shedders [coefficient(95%CI):1.62(1.19,2.05);p < 0.001], and viral loads increased with the number of visits where KSHV DNA was detected in saliva (type III test p < 0.001). Household-level factors attributed for 19% of the variability in KSHV shedding (ICC:0.191;p = 0.010). Geospatial analysis indicated overlapping hotspots of households with more KSHV seropositive individuals and KSHV shedders, distinct from areas where PLWH were clustered. Discussion: KSHV oral shedding is influenced by multiple factors at the individual, household, and regional levels. To mitigate ongoing KSHV transmission a comprehensive understanding of factors contributing to oral KSHV reactivation and transmission within households is needed.

Factors affecting Kaposi's sarcoma-associated herpesvirus transmission in rural Ugandan households, a longitudinal study.

BACKGROUND: We report the impact of HIV infection within a household on oral Kaposi's sarcoma-associated herpesvirus (KSHV) shedding. METHODS: We enrolled 469 individuals from 90 households. Mouthwash rinse samples collected at three monthly visits were analyzed for KSHV DNA using quantitative polymerase chain reaction (qPCR). Generalized linear mixed effects logistic models were applied to analyze factors associated with KSHV ever shedding, and among shedders, always versus intermittent shedding. Linear mixed effects models were applied to models of KSHV viral loads. Intraclass correlation coefficients (ICCs) were calculated to assess the contribution of household-level factors to variations in shedding probabilities. Hotspot analyses of geospatial feature clusters were calculated using Getis-Ord Gi* statistic and visualized using inverse distance weighted interpolation. RESULTS: Analyses included 340 KSHV seropositive individuals, aged 3 + years, with qPCR results from 89 households. Forty households had 1 + persons living with HIV (PLWH), while 49 had none. Among participants, 149(44%) were KSHV ever shedders. Of 140 who shed KSHV at two or more visits, 34(24%) were always shedders. Increasing number of KSHV seropositive household members was significantly associated with ever shedding [Odds ratio(OR) (95% Confidence Interval(95%CI)):1.14(1.03,1.26);p = 0.013]. Among KSHV shedders, a statistically significant age-related trend was identified with 10-19 years being more likely to be always shedders (type III test p = 0.039) and to have higher viral loads (type III test p = 0.027). In addition, higher viral loads were significantly associated with increasing number of household members [coefficient(95%CI):0.06(0.01,0.12);p = 0.042], increasing number of KSHV seropositive members [coefficient(95%CI):0.08(0.01,0.15);p = 0.021], and living in households with 1 + PLWH [coefficient(95%CI):0.51(0.04,0.98);p = 0.033]. Always shedders exhibited higher viral loads than intermittent shedders [coefficient(95%CI):1.62(1.19,2.05);p < 0.001], and viral loads increased with the number of visits where KSHV DNA was detected in saliva (type III test p < 0.001). Household-level factors attributed for 19% of the variability in KSHV shedding (ICC:0.191;p = 0.010). Geospatial analysis indicated overlapping hotspots of households with more KSHV seropositive individuals and KSHV shedders, distinct from areas where PLWH were clustered. DISCUSSION: KSHV oral shedding is influenced by multiple factors at the individual, household, and regional levels. To mitigate ongoing KSHV transmission a comprehensive understanding of factors contributing to oral KSHV reactivation and transmission within households is needed.

Characteristics and outcomes of KSHV-associated multicentric Castleman disease with or without other KSHV diseases.

Kaposi sarcoma (KS)-associated herpesvirus (KSHV)-associated multicentric Castleman disease (MCD) is a relapsing and remitting systemic lymphoproliferative disorder characterized by severe inflammatory symptoms most common among people living with HIV (PLWH). Patients with KSHV-MCD may present with concurrent KSHV-associated diseases, such as KS and/or primary effusion lymphoma (PEL). We evaluated clinical and immunologic characteristics, the effects of concurrent KSHV malignancies, and treatments from the largest prospective natural history study of participants with KSHV-MCD within the United States. Treatment options administered at investigator discretion included high-dose zidovudine with valganciclovir (AZT/VGC), rituximab, or rituximab with liposomal doxorubicin (R-Dox) during KSHV-MCD flares. Survival analyses and prognostic factors were explored for all participants. Sixty-two participants with HIV were enrolled, including 20 with KSHV-MCD alone, 34 with KSHV-MCD and KS, 1 with KSHV-MCD and PEL, and 7 with all KSHV-associated diseases. Forty-four percent of KSHV-MCD diagnoses were made at our institution. Forty-four participants received rituximab-based therapies, 20 of whom had maintenance AZT/VGC or interferon. Participants receiving R-Dox and then maintenance AZT/VGC had the highest 5-year progression-free survival (89%). Cytokine profiles during KSHV-MCD flares did not differ by the presence of concurrent KSHV-associated diseases. The 10-year survival was 71% (95% confidence interval [CI], 56% to 82%) for all participants. A concurrent diagnosis of PEL negatively impacted survival (PEL hazard ratio, 5.4; 95% CI, 1.8 to 16.8). KSHV-MCD is an underdiagnosed condition among PLWH, including those with KS. KSHV-MCD has an excellent prognosis with appropriate treatment. Physicians should be alert for patients with multiple KSHV diseases, which impact optimal treatment and survival outcomes. This study was registered at www.clinicaltrials.gov as #NCT00099073.

Polymorphisms in KSHV-encoded microRNA sequences affect levels of mature viral microRNA in Kaposi Sarcoma lesions.

Background: We previously reported Kaposi sarcoma-associated herpesvirus (KSHV) microRNA sequence variants in clinical samples correlated with increased risk of multicentric Castleman's disease (MCD). We then demonstrated that microRNAs with variant sequence have different maturation and mature microRNA expression in vitro. Here, we illustrate the association between microRNA sequence and changes in mature microRNA levels within Kaposi sarcoma (KS) lesions. Methods: KSHV microRNA sequences were determined from 20 KS lesions and 4 control skin biopsies from individuals evaluated for KS. Levels of mature KSHV microRNAs were measured with 21 custom small RNA qRT-PCR assays using RNA RNU6B as endogenous control. Results: The levels of 13 KSHV-encoded microRNAs were elevated in KS lesions compared to control biopsies. MicroRNA 9-5p was strongly down regulated in South African vs. US biopsies. Low levels of K12-9-5p were associated with single nucleotide polymorphisms (SNPs) in miR-K12-9-5p, 4-5p, 5-3p, 7-3p and pri-miR-K12-3. One SNP in pri-miR-K12-3 resulted in down regulation of miR-K12-6-3p, 8-3p, 10-3p, 12-5p and the upregulation of 5-5p, illustrating sequence variants outside pre-microRNAs were also associated with changes in mature microRNA levels. Conclusions: The levels of mature KSHV-encoded microRNAs in KS lesions correlate with sequence variation reflecting changes in secondary and tertiary RNA structure.

Evidence for a Mesothelial Origin of Body Cavity Effusion Lymphomas.

Background: Primary effusion lymphoma (PEL) is a Kaposi's sarcoma herpes virus (KSHV)-induced lymphoma that typically arises in body cavities of HIV-infected patients. PEL cells are often co-infected with Epstein-Barr virus (EBV). "PEL-like" lymphoma is a KSHV-unrelated lymphoma that arises in body cavities of HIV-negative patients. "PEL-like" lymphoma is sometimes EBV positive. The derivation of PEL/"PEL-like" cells is unclear. Methods: Mesothelial cells were cultured from body cavity effusions of 23 patients. Cell proliferation, cytokine secretion, marker phenotypes, KSHV/EBV infection, and clonality were evaluated by standard methods. Gene expression was measured by quantitative polymerase chain reaction and immunoblotting. A mouse model of PEL (3 mice/group) was used to evaluate tumorigenicity. Results: We found that the mesothelia derived from six effusions of HIV-infected patients with PEL or other KSHV-associated diseases contained rare KSHV + or EBV + mesothelial cells. After extended culture (16-17 weeks), some mesothelial cells underwent a trans-differentiation process, generating lymphoid-type CD45 + /B220 + , CD5 + , CD27 + , CD43 + , CD11c + , and CD3 - cells resembling "B1-cells," most commonly found in mouse body cavities. These "B1-like" cells were short lived. However, long-term KSHV + EBV - and EBV + KSHV - clonal cell lines emerged from mesothelial cultures from two patients that were clonally distinct from the monoclonal or polyclonal B-cell populations found in the patients' original effusions. Conclusions: Mesothelial-to-lymphoid transformation is a newly identified in vitro process that generates "B1-like" cells and is associated with the emergence of long-lived KSHV or EBV-infected cell lines in KSHV-infected patients. These results identify mesothelial cultures as a source of PEL cells and lymphoid cells in humans.

Detection and quantification of Kaposi's sarcoma-associated herpesvirus to predict AIDS-associated Kaposi's sarcoma.

OBJECTIVE: To identify immunologic and virologic predictors of AIDS-associated Kaposi's sarcoma (KS). DESIGN: Nested case-control analysis of KS risk in a cohort of 132 HIV-infected homosexual men in New York and Washington, DC, USA. METHODS: For each KS case, we selected two HIV-infected controls, matched for CD4 cell count and Kaposi's sarcoma-associated herpesvirus (human herpesvirus 8; KSHV) serostatus (enzyme immunoassay for antibody to KSHV protein K8.1). Cell-associated KSHV and Epstein-Barr virus (EBV) viral loads were measured with quantitative real-time PCR assays on samples collected 1 year (median) before KS diagnosis. RESULTS: Thirty-one men developed AIDS-associated KS (incidence 3.1 per 100 person years). Among HIV-infected men, KS incidence was higher among those with K8.1 seropositivity (5.0 versus 1.4 per 100 person years; P = 0.004), low CD4 cell count [hazard ratio (HR), 1.49; 95% confidence interval (CI), 1.24-1.79 per 100 x 10(6) cells/l decline), or high HIV RNA level (HR, 3.96; 95% CI, 2.19-7.16 per log(10)). In the case-control analysis, nine of 70 evaluated subjects had KSHV viremia, generally low level (median viral load 180 copies per 1 x 10(6) cells). KSHV viremia was associated with increased KS risk (unadjusted odds ratio, 9.1; 95% CI, 1.7-48; odds ratio, 11.7; 95% CI, 1.8-76 after adjustment for K8.1 serostatus, CD4 cell count, and HIV RNA). Among K8.1-seropositive subjects, KS incidence was tenfold higher in those with KSHV viremia (30.3 per 100 person years versus 3.4 per 100 person years in those without viremia). Also, EBV viral loads were higher in cases than in controls (P = 0.07). CONCLUSIONS: Among individuals with HIV-KSHV coinfection, KSHV viremia identifies a subgroup with extremely high risk for developing KS.

A Unique Case of Classic Kaposi's sarcoma restricted to the toes.

BACKGROUND: Kaposi's sarcoma associated-herpesvirus causes all forms of Kaposi's sarcoma, and six major subtypes have been described based on the amino acid sequences of the open reading frame K1. MAIN OBSERVATION: A 71-year-old man from China, HIV negative, presented with nodules on the dorsal aspect of his toes. Biopsy confirmed the diagnosis of Kaposi's sarcoma and virology studies of his blood and saliva confirmed the presence of Kaposi's sarcoma associated-herpesvirus infection. Viral genotyping was consistent with subtype C3. Intervention has been deferred as our patient has remained clinically asymptomatic and without evident growth of his lesions over a 2-year follow up. CONCLUSIONS: We herein report the first known case of Kaposi's sarcoma restricted to the toes caused by the viral subtype C3 in an HIV-negative patient from Harbin, China.

Reactivation of Kaposi's sarcoma-associated herpesvirus by natural products from Kaposi's sarcoma endemic regions.

Kaposi's sarcoma (KS) and its causative agent, Kaposi's sarcoma associated herpesvirus (KSHV/HHV-8), a gamma2 herpesvirus, have distinctive geographical distributions that are largely unexplained. We propose the "oncoweed" hypothesis to explain these differences, namely that environmental cofactors present in KS endemic regions cause frequent reactivation of KSHV in infected subjects, leading to increased viral shedding and transmission leading to increased prevalence of KSHV infection as well as high viral load levels and antibody titers. Reactivation also plays a role in the pathogenesis of KSHV-associated malignancies. To test this hypothesis, we employed an in vitro KSHV reactivation assay that measured increases in KSHV viral load in KSHV infected primary effusion lymphoma (PEL) cells and screened aqueous natural product extracts from KS endemic regions. Of 4,842 extracts from 38 countries, 184 (5%) caused KSHV reactivation. Extracts that caused reactivation came from a wide variety of plant families, and extracts from Africa, where KSHV is highly prevalent, caused the greatest level of reactivation. Time course experiments were performed using 28 extracts that caused the highest levels of reactivation. The specificity of the effects on viral replication was examined using transcriptional profiling of all viral mRNAs. The array data indicated that the natural extracts caused an ordered cascade of lytic replication similar to that seen after induction with synthetic activators. These in vitro data provide support for the "oncoweed" hypothesis by demonstrating basic biological plausibility.

Genotypic characterization of Kaposi's sarcoma-associated herpesvirus in asymptomatic infected subjects from isolated populations.

Molecular epidemiological studies of Kaposi's sarcoma-associated herpesvirus (KSHV) have concentrated on characterization of viral strains in tumour biopsy samples from Kaposi's sarcoma (KS) patients, mostly obtained in the United States and Europe. Tumour biopsies are a convenient source of viral DNA, as they have a high viral load compared to peripheral blood. However, sequences obtained from biopsies may not be representative of viral strains in asymptomatic subjects and information on ethnicity is often not available. Here, a population-based approach has been used to study the molecular and seroepidemiology of KSHV in isolated populations in Ecuador and Botswana. Amerindians in Ecuador had a variable prevalence of KSHV and all strains characterized were of subtype E, based on K1 sequencing. All Amerindian strains had predominant (P)-type K15 alleles and had sequences in both T0.7 and ORF 75 that appeared to be characteristic of these strains. The prevalence of KSHV in two ethnic groups in Botswana was extremely high. K1 sequences from both Bantu and San subjects were mostly of subtypes B and A5, which are typical of African KSHV strains, but the sequence from one San subject did not cluster with any known subtype. Considerable heterogeneity was seen in the T0.7 and ORF 75 genes in the San subjects and one had a minor (M)-type K15 allele. The heterogeneity of the KSHV strains found in these subjects from Botswana contrasts with the homogeneity of KSHV strains in Amerindians, reflecting differences in the evolutionary history of these populations.