Table of contents :

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Epidemiology Genomics Proteomics Transmission Pathogenesis Symptoms & signs Laboratory examinations Therapy

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Epidemiology : described by Chang et al in 1994^ref (particles were described in a short-term tissue culture of a KS lesion^{ref1, ref2}, and they were subsequently identified as cytomegalovirus^ref).  In sub-Saharan Africa, antibodies to HHV-8 can be found in upwards of 30% of the general population^{ref1, ref2}. From 10 to 25% of people from the Mediterranean area are seropositive for the virus. Geographic pockets in this area with higher or lower prevalences can be found. In the rest of the world, the seroprevalence in healthy donors, based on detection of latent and lytic proteins, is low, 2 to 5%^ref. Seroprevalence is 80 to 95% in classic KS patients, and 40 to 50% in HIV-1 patients without KS. Male-to-female ratio increases with age and pregnancy interferes with the course of disease (an inhibiting factor has been found in pregnants' urine)
Genomics : HHV-8 is related to the rhadinoviruses herpesvirus saimiri, found in squirrel monkeys, and herpesvirus ateles, found in spider monkeys. Both primates are native to South America. HHV-8 is also in the lineage of rhadinoviruses that infect macaques and African green monkeys^{ref1, ref2}. More recent studies^{ref1, ref2, ref3, ref4, ref5, ref6} have found additional rhadinoviruses that are closely related to HHV-8 infecting monkeys and chimpanzees. PCR has detected the DNA polymerase from rhadinoviruses in rhesus monkeys and pigtail macaques suffering from retroperitoneal fibromatosis (virus strains FHVMm and RFHVMn) and also in asymptomatic African green monkeys (virus strain ChRV-1). Retroperitoneal fibromatosis is characterized by a proliferation of spindle cells that is somewhat similar to KS. HHV-8 homologues were also detected in drill, mandrill, and a hybrid of Mandrillus leucophaeus-Mandrill sphinx, nonhuman primates living in Cameroon and Gabon, central Africa^ref. Gamma-2 herpesviruses of higher primates closely related to HHV-8 were isolated from chimpanzees and gorillas after finding that they expressed KHSV antigens^ref.

The central portion of the genome is flanked by the terminal repeats, labeled TR. The KSHV genome contains close to 100 open reading frames. Many of these are conserved in most herpesviruses; these are present in the conserved blocks (white boxes) and are not indicated. Other open reading frames are unique to rhadinoviruses, gammaherpesviruses, or KSHV and are present in more divergent areas of the genome (indicated by gray boxes). ORFs that have homology with herpesvirus saimiri are assigned the corresponding numbers, and ORFs without recognizable homologues were numbered separately and given the prefix K (K1 to K15)
HHV-8 exhibits typical herpesvirus morphology: 100- to 150-nm particles with a lipid envelope and an electron-dense central core^ref. Its capsid is icosahedral, with a 110-nm diameter, and consists of 162 hexagonal capsomeres^ref Mature virions with a glycoprotein coat are 140 nm in diameter. The tegument is a protein-filled region between the capsid and the envelope. The 75-nm torus-shaped core is a complex of DNA and protein. In appearance, HHV-8 is indistinguishable from a-, b-, and other gammaherpesvirus particles. Orenstein et al.^ref found herpesvirus particles in electron micrographs of KS lesions from three patients. Since HHV-8 has been found to productively infect spindle cells derived from microvascular endothelial cells and mononuclear cells, the particles found in the KS lesions are consistent with HHV-8. PCR analysis on the skin, lymph node, and spleen from the 3 patients was positive for HHV-8; however, the lymph node was positive for EBV as well. When the envelope glycoproteins of HHV-8 bind the proteoglycans on the surface of the host cell, penetration can occur by fusion of the viral envelope with the plasma membrane of the cell. HHV-8 infects dividing B cells (CD45⁺) during mitosis, much like EBV, the human gammaherpesvirus. Following circularization of the viral genome DNA replication and capsid assembly occur in the nucleus of the host cell. Pulsed-field gel electrophoresis of DNA extracted from purified HHV-8 virions shows that the full-length genome is 165 to 170 kb. Primary characterization of the genome was done by Moore et al.^ref, and others^{ref1, ref2} have done additional studies. The genome of HHV-8 is similar to that of herpesvirus saimiri in that it has a single contiguous region, 140 to 145 kb, containing all the coding regions. Some permissive and nonpermissive tumor cell lines harbor forms of HHV-8 viral DNA up to 270 kb in size^ref. The genome has repeats of 803 bp in length that are 85% guanidine and cytosine. Each molecule harbors 35 to 45 such repeats, but they are not arrayed uniformly or symmetrically at each end^ref. Like EBV, the latent HHV-8 genome appears to have a circular conformation, but the active DNA found during lytic replication is linear^ref. Strain variation is very common among human herpesviruses, e.g., herpes simplex virus types 1 and 2 in the alphaherpesvirus group, HHV-6 variants A and B in the betaherpesvirus group, and EBV types A and B in the gammaherpesvirus group. Hayward^ref found similar variation in the gene products of KSHV ORF-K1 and ORF-K15. Both of these seem to code for membrane-signaling proteins; they contain conserved tyrosine kinase interaction motifs within their C-terminal cytoplasmic domains^{ref1, ref2}. ORF-K1 and ORF-15 may play a key role in the biology and disease manifestation associated with HHV-8^ref. Based on the analysis of the ORF-K1 and ORF-15 genes, 5 HHV-8 variants (groups A to E) have been identified. Group B is dominant in Africa; D and E are confined to Pacific Island and Amerindian populations. In Europe and North America, groups A and C predominate^ref. Geographic strain variation in gene sequences has been identified in viruses isolated from Japan, Kuwait, Europe, Russia, Australia, South America, and the USA^{ref1, ref2, ref3, ref4, ref5}. Although specific variants have not been associated with different pathologies, the high level of strain variability in HHV-8 may have important functional implications, although no serological differences have been noted using the currently available serological assays. HHV-8 has many homologies with closely related viruses^ref but also has many unique sequences^ref. ORF-26 of HHV-8, which encodes the minor capsid protein, has 51% homology to VP23 of herpesvirus saimiri and is 39% homologous to the EBV open reading frame (ORF) for tegument, BD LF1^ref. Of the approximately 95 genes in the HHV-8 genome, nearly 25 encode novel proteins not found in other human herpesviruses. Many of these represent captured and diverged homologues of cellular genes that are referred to by ORF-K numbers if they do not have homologues in the herpesvirus saimiri genome. A number of genes seem to be responsible for KS pathogenesis: K1, K2, vMIPS, K4, K4.1, K5, K9, K12, ORF-6, ORF-71, ORF-73, ORF-74, and K15^ref
Proteomics :

• replication and transcription activator (Rta) expression during lytic reactivation of HHV-8 would lead to expression of some cellular genes, including IL-6, whereas activation of NF-kB could inhibit some responses to Rta.
• KsBcl-2 is a Bcl-2 homolog which lacks a loop domain and has poorly conserved BH3 and BH4 domains, escaping negative regulation by pro-apoptotic kinases and caspases.
• v-CXCR2 homolog
• latency-associated nuclear antigen (LANA) is expressed in all KSHV-associated tumors, including KS and PEL : it causes a cell cycle-dependent nuclear accumulation of GSK-3b, stabilizing and upregulating expression of b-catenin.
• K14 binds to CD200R and inhibits myeloid cells
• kaposin B activates MAPKAPK2, serving to block the decay of AU-rich mRNAs and increase the level of secreted cytokines^ref.
• v-FLIP
• v-cyclin
• v-IL-6

Transmission :

• sexual route (?) => it infects CD19⁺ B lymphocytes. During first trimester of pregnancy IFN protects the foetus from infection.
• through body fluids (e.g., saliva and blood).

Susceptibility : HLA-Aw23, HLA-Aw49, HLA-B35, HLA-C4, HLA-DR1, HLA-DR2, HLA-DR5, HLA-DQ1
Pathogenesis : KSHV infects both lymphatic endothelial cells (LECs) and blood vascular endothelial cells (BECs) in vitro. The gene expression microarray profiles of infected LECs and BECs show that KSHV induces transcriptional reprogramming of both cell types. Infection of differentiated BECs with KSHV leads to their lymphatic reprogramming; induction of 70% of the main lymphatic lineage–specific genes, including PROX1, a master regulator of lymphatic development; and downregulation of blood vascular genes^ref. The lymphangiogenic molecules VEGF-D and angiopoietin-2 are elevated in the plasma of individuals with AIDS and Kaposi sarcoma^ref. CD34⁺ HPCs may be a reservoir for KSHV infection and may provide a continuous source of virally infected cells in vivo^ref.
=> classical, endemic, and AIDS-associated iatrogenically acquired Kaposi's (angio)sarcoma (KS) / multiple hemorrhagic sarcomatosis^ref. In situ hybridization techniques have pinpointed the location of HHV-8 in the vascular endothelial cells and perivascular spindle-shaped cells in KS lesions^{ref1, ref2} (Li, S, 1714 ). This association has been supported both by molecular analysis^{ref1, ref2, ref3, ref4} and by seroepidemiological studies^{ref1, ref2, ref3}

=> lymphoproliferative disorders^ref :

	AIDS-related body cavity-based B-cell primary effusion lymphomas (PEL)ref	plasmablastic multicentric Castleman's disease (MCD) and MCD-associated plasmablastic lymphoma	germinotropic lymphoproliferative disorder (GLD)
clinical presentation	in immunodeficient patients, with systemic symptoms, poor prognosis	predominantly in immunodeficient patients, with systemic symptoms, poor prognosis	in immunocompetent patients with localized lymphadenopathy, favorable response to therapy
sites	body cavities, extranodal sites	lymph nodes, spleen	lymph nodes
morphology	immunoblasts with pleomorphic nuclei and abundant plasmacytoid cytoplasm	plasmablasts, preferentially residing in the mantle zone	plasmablasts, preferentially invading germinal centers
EBV	present in HIV-associated patients; absent in HIV-negative patients	negative	positive
cytoplasmic Ig expression	absent	high, always IgM	high, and heavy chain
Ig light chain	monotypic k or l chain	monotypic l	monotypic k or l
CD30	positive	weakly positive	variable
B-cell antigens	absent	weak or absent	absent
mutation in Ig genes	mutated in most	absent	mutated
cellular origin	germinal center or postgerminal center B cells	naive IgMl expressing B cells	germinal center B cells

(A) KS lesions in the lower extremities typical of a sporadic case. (B) Hyperpigmented KS lesions in the upper arms. (C) Histological section stained with hematoxylin and eosin of a nodular tumor stage lesion of KS. Note the spindle cell proliferation and abundant vasculature. (D) KSHV LANA (ORF-73) expression in KS. Staining with a rat monoclonal antibody revealed LANA positivity (diaminobenzidine, brown) in the nuclei of many spindle cells in a KS lesion. Positivity was also identified in endothelial cells lining the larger vascular spaces that may represent lymphatic vessels. (E) Histology of multicentric Castleman's disease. Hematoxylin- and eosin-stained section of a lymph node with HIV-associated Castleman's disease showing a single follicle with a large, concentrically arranged mantle zone surrounding a germinal center. The interfollicular area contains a network of small vessels. (F) KSHV vIL-6 expression in MCD. Immunohistochemical staining with polyclonal antiserum to vIL-6, showing cells with cytoplasmic positivity (diaminobenzidine, brown) in the mantle zone surrounding an atrophic germinal center. (G) Wright-Giemsa stain air-dried cytocentrifuge preparation of a KSHV-positive primary effusion lymphoma. The two tumor cells in this image are considerably larger than normal benign lymphocytes and neutrophils. The cells display significant polymorphism and possess moderately abundant basophilic cytoplasm. A prominent, clear perinuclear Golgi zone can be appreciated in the largest cell. The nuclei vary from large and round to highly irregular, multilobated, and pleomorphic and often contain one or more prominent nucleoli. (H) KSHV LANA (ORF-73) expression in KSHV-positive lymphomas. Staining with a rat monoclonal antibody revealed LANA positivity (alkaline phosphatase, red) in the nuclei of large, atypical lymphoma cells seen infiltrating reactive lymphoid tissue. This section was double stained with a polyclonal antiserum to kappa light chains (diaminobenzidine, brown), showing cytoplasmic positivity in a few of the surrounding cells but not the tumor cells. (I) KSHV vIL-6 expression in PELs. Immunohistochemical staining of cell block containing the BC-3 cell line was performed with a polyclonal rabbit antiserum to a vIL-6-specific peptide. Abundant expression is seen (diaminobenzidine, brown) in numerous lymphoma cells. (J) Detection by IFA of KSHV latent IgG antibody in serum from a classic KS patient. Typical nuclear speckles in the PEL cell line KS-1 are evident at a 1:50 dilution of the serum. (K) Presence of LANA-2 protein in KSHV-infected BCBL-1 cells. Diffuse finely speckled nuclear pattern of LANA-2 (green) is observed by IFA with LANA-2 monoclonal antibody. (L) Detection by IFA of KSHV lytic antibody in serum from a classic KS patient, using induced KS-1 cells. Apple green diffusely stained cells carry lytic antigen. Original magnifications: x200 (D, E, F, and I), x600 (C and H), and x1,000 (G).
=> MGUS^ref and multiple myeloma : initial studies evaluating the presence of KSHV in a large series of lymphoid proliferations failed to identify this virus in multiple myeloma or other plasma cell malignancies^{ref1, ref2, ref3, ref4}. However, an association between this virus and multiple myeloma was subsequently reported^{ref1, ref2}. In that study, KSHV DNA and RNA sequences were detected in bone marrow stromal cell cultures from patients with multiple myeloma as well as 2 of 8 patients with MGUS. This result, which was based on PCR and RT-PCR analyses, was subsequently confirmed by the same team using in situ hybridization and PCR analysis of DNA extracted from fresh bone marrow core biopsies^{ref1, ref2}. Since transcripts of KSHV vIL-6 were detected, it was hypothesized that KSHV uses a paracrine mechanism through production of this cytokine to stimulate the proliferation of the myeloma plasma cells. Multiple studies have been published since, with conflicting results. Several additional independent laboratories confirmed the specific presence of KSHV DNA sequences in multiple myeloma biopsies^{ref1, ref2, ref3} (P. Brousette, F. Meggetto, M. Attal, and G. Delsol, Letter, Science 278:1972, 1997; M. B. Rettig, J. W. Said, R. Sun, R. A. Vescio, and J. R. Berenson, Author's Reply, Science 278:1972-1973, 1997). However, other investigators have been unable to confirm this association when looking for KSHV DNA by PCR in bone marrow biopsies and/or dendritic cell cultures from bone marrow or peripheral blood^{ref1, ref2, ref3, ref4, ref5, ref6, ref7, ref8, ref9, ref10, ref11, ref12}. Serologic studies have been almost uniform in their findings, demonstrating that patients with multiple myeloma lack antibodies to KSHV^{ref1, ref2, ref3, ref4, ref5, ref6, ref7, ref8}. This lack of reactivity is not due to generalized immunosuppression, since antibodies to other more ubiquitous herpesviruses, such as EBV, HHV-6, and cytomegalovirus, are easily detectable in these patients by using comparable methodologies. Since MGUS patients are known to develop multiple myeloma or other lymphoproliferative diseases within 10 to 20 years^ref, the serum of MGUS patients, some of whom later developed multiple myeloma, was tested for the presence of HHV-8 IgG antibodies to both lytic and latent antigens (2). Even though the majority of these sera were positive for EBV antibody, no difference was found among normal blood donors, MGUS patients, and multiple myeloma patients for HHV-8 antibody.  Another group has also been unable to confirm the association between KSHV infection and multiple myeloma, using a variety of methods^ref (E. Cesarman, unpublished observation). In one paper, very weak seroreactivity to KSHV antigens was detected by immunoblotting^ref. While this may be confirmatory of the association between KSHV infection and multiple myeloma, it is possible that this low reactivity represents higher levels of nonspecific cross-reactivity than in control patients because of the gammopathy in multiple myeloma patients. Furthermore, the epidemiologic patterns of KS and multiple myeloma are distinct, suggesting different etiologies^ref. 3 explanations can be proposed to explain this controversy. (i) KSHV is not present in multiple myeloma or MGUS, and the identification of viral sequences by a fraction of investigators is due to technical artifacts, such as PCR contamination. (ii) KSHV is present in such low copy numbers in bone marrow and dendritic cell preparations in patients with multiple myeloma that the technique used by most laboratories is not sufficiently sensitive to detect them, although in several studies sensitivity controls suggest detection of 1 to 10 copies of KSHV. In this instance, the absent or very low serologic reactivity remains to be explained; it has been hypothesized that HHV-8 localization within the bone marrow-based dendritic cells may prevent the maturation of an antigenic response due to B-cell tolerance of antigens presented in the bone marrow^ref. This reasoning would not explain, however, the discrepant epidemiology of both diseases. (iii) A different virus is present in multiple myeloma, similar enough to be recognized by some PCR primers when certain protocols with low stringency are used. Antibodies to this novel virus may not recognize most KSHV antigens^ref. This explanation may be supported by sequence analysis of PCR products from specimens obtained from patients with multiple myeloma, where significant interpatient variation has been noted. There is higher reported homology in the sequences among different myeloma patients than when these sequences are compared with the KSHV sequences for KS specimens^ref. One study has suggested that sequences homologous to one of the regions of KSHV are widely disseminated in a variety of tissues, including multiple myeloma^ref. While this last possibility appears to be the most conciliatory explanation, much additional evidence needs to be provided to confirm the presence of a distinct KSHV-like virus and then to confirm its specific association with multiple myeloma and MGUS. In addition, a study using degenerate primers failed to detect novel herpesvirus sequences in multiple myeloma, suggesting that the presence of a novel human herpesvirus in this disease is not likely^ref.
=> hemophagocytic syndrome (HPS) with KSHV-related effusion lymphoma : novel association of HHV-8 with hemophagocytic syndrome (HPS) has been reported. HPS is a fulminant, fatal, systemic illness that occurs in association with infection and malignancy. HPS is characterized as an infiltration of the reticuloendothelial system by histocytes that engulf and destroy the formed elements of blood. Patients with HPS suffer from systemic illness with fever, adenopathy, hepatosplenomegaly, liver failure, cytopenia, and coagulopathy. HPS is generally associated with AIDS patients in advanced stages of the disease. Examination of the spleen of an HPS patient revealed HHV-8 DNA by PCR. No EBV DNA was detected^ref. Another case of HPS was reported by Low et al.^ref, in which the patient had HHV-8 infection. After he was treated with the antiviral agent foscarnet, the patient improved dramatically. This suggested that foscarnet, an antiherpesvirus agent, blocked in vivo HHV-8 replication. More cases of HPS are needed to confirm the association with HHV-8.
=> pemphigus vulgaris and pemphigus foliaceus are autoimmune diseases of the skin characterized by separation of the dermis and epidermis; the origin is unknown, but KS is the most frequent malignancy observed in pemphigus patients^ref. A group studying pemphigus patients without HIV in Texas^{ref1, ref2} found HHV-8 DNA in the lesional skin of 4 of 6 patients with pemphigus vulgaris and 6 of 6 patients with pemphigus foliaceus who were studied. The PCR DNA sequences differed among all these patients. No HHV-8 DNA was found in normal skin from 10 controls tested from the same area. Patients with pemphigus vulgaris have a more frequent incidence of KS than those with pemphigus foliaceus. It has been suggested that HHV-8 has a tropism for pemphigus lesions. Researchers in New Mexico have found a high incidence of pemphigus in a New Mexican population, identified by self-identification and HLA typing as descendants of Sephardic Jews who came to the southwestern USA to avoid persecution during the Spanish Inquisition (Bordenave, K, 825). It could well be that the patients from Texas have a similar heritage and that there is no cause and effect between HHV-8 and pemphigus, but both have a high frequency in this unique population that traces its origin to the Mediterranean basin. Other investigators have failed to identify an association between KSHV infection and pemphigus^{ref1, ref2, ref3, ref4}
=> bullous phemigoid : at least 5 cases have been reported in which KS has developed in association with it^{ref1, ref2, ref3}. With the exception of one case, these were not studied for the presence of HHV-8. In the case that was investigated^ref, KS developed during a 3-year period of radiotherapy for bullous phemigoid. HHV-8 DNA sequences were found in 2 separate KS lesions but not in control skin from the same patient. The immunosuppressive therapy that the bullous phemigoid patient received could have activated HHV-8, which led to the development of KS.
=> skin tumors. In a study of 69 patients who were HIV positive or who were immunosuppressed following organ transplantation, many subsequently developed skin tumors. Among those that had premalignant Bowen's disease, 71.4% had HHV-8 DNA; 50% of those who developed squamous cell carcinoma were positive for HHV-8 DNA; and 33.3% of those with actinic keratosis, a malignant epidermal disorder, were positive. A lower frequency, 16.7%, was found in those who developed extramammary Paget's disease, in both proliferative and nonproliferative lesions^{ref1, ref2}. Similar associations were reported by a second group^ref. These studies suggested that HHV-8 infection may increase the likelihood of proliferative skin disease. However, several additional well-controlled studies failed to confirm this association^{ref1, ref2, ref3}. In a study of HIV-1 carriers in Thailand^ref, HHV-8 DNA was found in 25% of those with skin diseases and only 7.4% with no skin involvement. Carriers with antibodies to lytic HHV-8 antigens also had low CD4 and CD8 counts, and specific HHV-8 polypeptides with a molecular mass of 34,000 to 40,000 Da were identified by immunoprecipitation. This adds to the body of evidence linking HHV-8 to skin disorders in the presence of immunosuppression. An association between KSHV and some angiosarcomas has also been reported. In one study, 7 of 24 patients with angiosarcoma studied plus one of five who had hemangioma, none of whom had systemic immunosuppression, were positive for HHV-8 DNA. The association of these 2 diseases involving endothelial cells was the first evidence for disease associated with HHV-8 other than KS that does not require immune suppression^ref. HHV-8 DNA was detected in vascular neoplasms, which are endothelial in origin. HHV-8 DNA was found only in hemangioma (1 of 20) and angiosarcoma (7 of 24). While these studies indicated a tropism of HHV-8 for endothelial cells, they did not demonstrate whether HHV-8 contributes actively to the pathology or is just a passenger virus. Although angiosarcoma and KS are different diseases, these tumors have a common histiogenesis from within the vascular compartment. Other investigators have failed to identify HHV-8 in angiosarcomas, casting doubts on the specificity of this association^{ref1, ref2, ref3, ref4, ref5, ref6, ref7, ref8}.
=> salivary gland tumors : it is common for healthy individuals to carry a latent infection of endemic human herpesviruses in their salivary glands, and shedding of EBV, cytomegalovirus, HHV-6, and HHV-7 during reactivation is well documented. Even though HHV-8 is not as widespread as other human herpesviruses, it has been detected in the saliva of HIV-1-infected individuals^ref, leading to the supposition that HHV-8 could spread via saliva as well as by sexual routes. Even though HHV-8 has been found in saliva, to date there has been only one identification of HHV-8 DNA by PCR in bilateral mucosa-associated lymphoid tissue lymphoma of the parotid gland of a female patient with Sjögren's syndrome^ref; therefore, it is unlikely HHV-8 plays any etiological role in vascular or epithelial neoplasms in immunocompromised patients.
=> reactive lymphadenopathy : HHV-8 was localized in lymphoid and monocyte-macrophage cells scattered in the interfollicular regions of lymph nodes but not in the endothelial cells of 2 patients^ref
=> chronic interstitial pneumonitis characterized by florid hyperplasia : HHV-8 has been found in inflammatory cells infiltrating the intervalvular interstitium of lung tissue, in endothelial cells of the pulmonary vasculature, and rarely in pneumocytes^ref. This study indicates that HHV-8 can infect nonneoplastic lymph nodes of immunocompetent individuals. HHV-8 has also been associated with interstitial pneumonitis in HIV-infected patients^ref.
=> primary pulmonary hypertension (PPH) : despite initial reports suggested that infection with the vasculotropic virus HHV-8 may have a pathogenetic role^ref, subsequent studies disproved the association. Samples of lung tissue, taken at autopsy, from 10 Japanese patients with PPH and samples of lung tissue from 12 Japanese patients with secondary pulmonary hypertension were tested for the presence of HHV-8. All samples from patients with PPH contained plexiform lesions around pulmonary arterial vessels, but immunohistochemistry failed to detect the HHV-8-encoded latency-associated nuclear antigen. HHV-8 DNA could not be amplified by PCR for the HHV-8-encoded K1 and KS330₂₃₃ genes in any sample. These data suggest that HHV-8 infection is not associated with PPH in Japanese patients^{ref1, ref2}
=> sarcoidosis has been described as a systemic disorder characterized by the presence in multiple tissues of noncaseating epithelioid cell granulomas, which may spontaneously resolve or convert to hyaline connective tissue. The etiology of sarcoidosis is unknown. HHV-8 DNA was found in a wide range of sarcoid but not nonsarcoid tissues^ref. The finding of a high frequency of HHV-8 DNA was attributed to PCR cross-contamination. A diagnosis of KS coexisting in the same lesion as a sarcoidosis, a disease characterized by suppressed cell-mediated immunity, was made in an HIV-negative patient. The biopsy of the newly disrupted skin lesion revealed a mid-dermal tumor composed of irregularly shaped vascular spaces, proliferation of spindle-shaped cells, and extravasated erythrocytes typical of KS, plus multiple noncaseating tuberculoid granulomas. HHV-8 was detected in this lesion by PCR^ref.
=> Kikuchi's disease (histocytic necrotizing lymphadenitis) is a common self-limited disorder of the cervical lymph nodes that occurs predominantly in young Asian females. It is characterized by fever, flu-like symptoms, elevated erythrocytes, neuropenia, an elevated sedimentation rate, and lymphocytosis. Huh et al.^ref found HHV-8 DNA by PCR followed by hybridization and Southern blot analysis in 6 samples of archival tissues from 26 patients with Kikuchi's disease. The authors concluded that HHV-8 may be an important factor in the pathogenesis of Kikuchi's disease. However, this result has not been confirmed by other researchers.
Transplantation risks : there is a 1 to 3% risk of KS with renal transplantation^ref, with the median interval to diagnosis of KS being 29 to 31 months^{ref1, ref2}. In Saudi Arabia, where there is a higher prevalency of HHV-8, the transplantation risk of KS rises to 3 to 5%^ref. Cattani et al.^ref assessed the risk of development of KS in pre- and postrenal transplantation. Overall, 23% of the patients who were HHV-8 positive before transplantation developed KS, whereas only 0.7% of seronegative control patients developed the disease. Posttransplantation KS has also been associated with transplantation of heart and lungs^{ref1, ref2, ref3, ref4}. However, it is still unclear whether posttransplantation KS is due to the reactivation of HHV-8. Most KS was from reactivation of latent HHV-8 infection due to immunosuppression rather than from new infection from the transplanted organ or transfusion. Studies of renal transplant patients in regions of high HHV-8 prevalency reveal that the immunosuppression treatment that precedes transplantation can activate latent virus and lead to iatrogenic KS^{ref1, ref2, ref3}. Therefore, in these areas, serological screening of the recipients is as important as screening of donors. Although most cases of transplant KS seem to be due to reactivation of virus in the recipient, cases of KS being transmitted from a donor organ have been reported^{ref1, ref2}. Serological and molecular testing on renal transplant patients has demonstrated persistent reactivation of HHV-8, which can lead to KS^ref. HHV-8 infection has been cited as a cause of bone marrow transplant failure^ref. A primary HHV-8 infection developed in two patients after both received kidneys from a seropositive cadaver donor. The patients developed disseminated KS after experiencing an acute syndrome characterized by fever with plasmacytosis. A case of HHV-8 viremia was reported after transplantation of autologous peripheral stem cells in an HHV-8-seropositive patient with non-Hodgkin's lymphoma, but there was no evidence of other infection. The reactivation manifested itself with a fever and marrow anaplasia with plasmacytosis. HHV-8 latent antigen and transcripts were expressed in the aplastic marrow but not in two normal marrow samples. It seems clear there is a high risk of KS associated with transplants due to the immunosuppression of the recipient, regardless of whether the HHV-8 is from the patient, the donor, or a blood transfusion^ref. HHV-8 DNA was found in kidney allografts in two of three transplant recipients prior to the development of KS. An increase in the level of HHV-8 DNA was detected in the third patient. This study suggested that direct genotypic and serologic analyses in kidney allografts in primary infection or increased viral antibody can predict the development of KS. Therefore, monitoring the transplant recipient for HHV-8 infection could be used to provide effective antiviral therapy^ref.
Laboratory examinations : PCR
Therapy : inhibitors of herpesvirus DNA polymerase are effective in combating lytic but not latent DNA infection. Foscarnet and ganciclovir induced regression of KS lesions in a small trial of HIV-infected patients and in three large follow-up studies^ref. In spite of these encouraging results, no change in the number of PBMCs infected with HHV-8 was found. HHV-8 was very sensitive to cidofovir when tested in vitro, whereas HHV-8 was only moderately sensitive to foscarnet and ganciclovir^{ref1, ref2}. Therefore, low doses of cidofovir or a high dose of foscarnet or ganciclovir could suppress clinical reactivation of HHV-8. These antiviral drugs did not inhibit episomal virus DNA polymerase, suggesting that the latent form of viral DNA is replicated by host DNA polymerase^ref. Foscarnet is known to be very toxic, and therefore, clinical dosages for this drug must be worked out for each patient. Although acyclovir has been very effective in preventing EBV (gamma-1 herpesvirus) infection of oral hairy leukoplakia^ref in AIDS patients, it has shown no such efficacy against HHV-8. Since these drugs work on the level of the viral polymerase, they are effective only in combating actively replicating virus and have no effect on the latent stage of infection. While the latent virus is not likely to cause damage, people at risk for virus reactivation, such as AIDS patients, should be monitored so that effective therapy can be instituted if the virus becomes active. The effect of antiretroviral therapy and the use of zidovudine to prevent perinatal transmission were also reported^{ref1, ref2, ref3, ref4}. Boivin et al.^ref showed that one AIDS patient with KS had a low viral load in KS skin lesions and PBMCs while on highly active antiretroviral therapy (HAART), suggesting a strong relationship between tumor burden and HHV-8 viral load in spite of HAART's having no direct anti-HHV-8 activity^ref. Antitumor activity of fractionated doses of oral etoposide in the treatment of AIDS-related KS was reported^ref, with a significant reduction in KS at a manageable clinical toxicity of the drug. These investigators, however, did not measure the effect on HHV-8. The institution of HAART triple-drug combination therapy has correlated with a decrease in the incidence of AIDS-related KS^ref. Cattelan et al.^ref studied AIDS-KS patients after they had been placed on the HAART regimen. Reduction in anti-ORF-65 antibody correlated with clinical improvements, but LNA showed a variable pattern. Decrease in plasma HIV-1 RNA levels and an increase in CD4 lymphocytes due to antiviral therapy with nucleotide analogs and protease inhibitors correlated with a regression of KS lesions. Another antiviral therapy of HIV-1 also had an ameliorative effect on AIDS-associated KS^ref. Topical treatment with 10% docosanel cream inhibits a broad spectrum of enveloped viruses in vitro, including herpes simplex virus types 1 and 2, cytomegalovirus, HHV-6, and HIV-1; KS lesions were reduced by 20%, and no treated patients experienced KS disease progression. In this study, no attempt was made to measure or detect HHV-8.

foscarnet. Latent infection with KSHV in B lymphocytes can be terminated by glycyrrhizic acid (GA), a triterpenoid compound earlier shown to inhibit the lytic replication of other herpesviruses. GA disrupts latent KSHV infection by downregulating the expression of LANA and upregulating the expression of viral cyclin and selectively induces cell death of KSHV-infected cells. Reduced levels of LANA lead to p53 reactivation, an increase in ROS, and mitochondrial dysfunction, which result in G₁ cell cycle arrest, DNA fragmentation, and oxidative stress–mediated apoptosis. Latent genes are involved in KSHV-induced oncogenesis, and strategies to interfere with their expression might prove useful for eradicating latent KSHV infection and have future therapeutic implications^ref.

Most primary effusion lymphomas (PEL) and Kaposi's sarcoma tumor cells are latently infected with HHV-8 and hence resistant to antiherpesvirus drugs that are dependent on lytic replication. In contrast, many of the cells infected with HHV-8 in multicentric Castleman's disease support lytic replication, so that clinical improvement frequently occurs in response to treatment with antiherpesvirus drugs. The resistance of latently-infected tumor cells to antiherpesvirus drugs can be overcome by inducing HHV-8 to reenter the lytic cascade in the presence of antiherpesvirus drugs. This leads to apoptosis of virally infected cells without increasing production of infectious virus. Alternatively, the replication and maintenance of the HHV-8 episome during latency can be disrupted by glycyrrhizic acid or hydroxyurea so that the virus no longer contributes to tumorigenesis. Both the innate and acquired immune systems can also be augmented to help prevent or treat HHV-8-associated tumors^ref

HHV-8-encoded vFLIP is one of the few viral proteins to be expressed in latently infected cells and plays a key role in the survival and proliferation of PEL cells. 2 main functions have been ascribed to HHV-8 vFLIP, inhibition of caspase 8/FADD-like IL-1-converting enzyme and activation of NF-kB. vFLIP-expressing transgenic mice lack any of the features seen in mice deficient in caspase 8 or FADD protein and are not resistant to Fas-induced apoptosis. On the other hand, these mice display constitutive activation of classical and alternative NF-kB pathways, enhanced response to mitogenic stimuli, and increased incidence of lymphoma. Collectively, our results demonstrate that HHV-8 vFLIP is an oncogenic protein that mimics the signaling activities of caspase 8 during antigen receptor signaling and could contribute to the development of lymphoproliferative disorders via constitutive NF-kB activation independent of inhibition of Fas-induced apoptosis^ref.

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