Janos Luka

The latent human herpesvirus-6A genome specifically integrates in telomeres of human chromosomes in vivo and in vitro

Previous research has suggested that human herpesvirus-6 (HHV-6) may integrate into host cell chromosomes and be vertically transmitted in the germ line, but the evidence—primarily fluorescence in situ hybridization (FISH)—is indirect. We sought, first, to definitively test these two hypotheses. Peripheral blood mononuclear cells (PBMCs) were isolated from families in which several members, including at least one parent and child, had unusually high copy numbers of HHV-6 DNA per milliliter of blood. FISH confirmed that HHV-6 DNA colocalized with telomeric regions of one allele on chromosomes 17p13.3, 18q23, and 22q13.3, and that the integration site was identical among members of the same family. Integration of the HHV-6 genome into TTAGGG telomere repeats was confirmed by additional methods and sequencing of the integration site. Partial sequencing of the viral genome identified the same integrated HHV-6A strain within members of families, confirming vertical transmission of the viral genome. We next asked whether HHV-6A infection of naïve cell lines could lead to integration. Following infection of naïve Jjhan and HEK-293 cell lines by HHV-6, the virus integrated into telomeres. Reactivation of integrated HHV-6A virus from individuals’ PBMCs as well as cell lines was successfully accomplished by compounds known to induce latent herpesvirus replication. Finally, no circular episomal forms were detected even by PCR. Taken together, the data suggest that HHV-6 is unique among human herpesviruses: it specifically and efficiently integrates into telomeres of chromosomes during latency rather than forming episomes, and the integrated viral genome is capable of producing virions.

HHV-6A infection induces expression of HERV-K18-encoded superantigen.

BACKGROUND The human endogenous retrovirus K-18 (HERV-K18) encodes a superantigen that causes deregulation of the immune system. This provirus is transcriptionally silent, but can be induced by Epstein-Barr virus (EBV) infection and IFN-alpha treatment. OBJECTIVES Since the herpesvirus EBV induces HERV-K18 expression in human B cells, it was of interest to determine if other herpesviruses would have similar HERV-K18 transactivation properties. Human herpesvirus (HHV)-6A, a neurotropic virus associated with multiple sclerosis, was a logical candidate for these studies. STUDY DESIGN HSB2 cells (HHV-6-negative control), HSB2-ML cells (containing latent HHV-6A genome) and HSB2/HHV-6A cells (HSB-2 cells productively infected with HHV-6A) were compared for their level of HERV-K18 transcription, using quantitative RT-PCR. RESULTS Latently infected HSB2-ML cells showed a significant increase in HERV-K18 RNA compared to the control cells. HERV-K18 expression was even greater in HSB2 cells productively infected with HHV-6A for 78h. CONCLUSION These results imply that HHV-6A, either in latent form or during acute infection, directly transactivates HERV-K18. This HERV-K18 induction may be mediated through IFN-alpha that is produced by the HHV-6A-infected cells. The functional implications of superantigen expression are discussed.

Persistent human herpesvirus‐6 infection in patients with an inherited form of the virus

Human herpesvirus‐6 (HHV‐6)A and 6B are ubiquitous betaherpesviruses viruses with lymphotropic and neurotropic potential. As reported earlier, these viruses establish latency by integration into the telomeres of host chromosomes. Chromosomally integrated HHV‐6 (CIHHV‐6) can be transmitted vertically from parent to child. Some CIHHV‐6 patients are suffering from neurological symptoms, while others remain asymptomatic. Four patients with CIHHV‐6 and CNS dysfunction were treated with valganciclovir or foscarnet. HHV‐6 replication was detected by reverse transcriptase polymerase chain reaction amplification of a late envelope glycoprotein. In this study we also compared the inherited and persistent HHV‐6 viruses by DNA sequencing. The prevalence of CIHHV‐6 in this cohort of adult patients from the USA suffering from a wide range of neurological symptoms including long‐term fatigue were found significantly greater than the reported 0.8% in the general population. Long‐term antiviral therapy inhibited HHV‐6 replication as documented by loss of viral mRNA production. Sequence comparison of the mRNA and the inherited viral genome revealed that the transcript is produced by an exogenous virus. In conclusion, the data presented here document that some individuals with CIHHV‐6 are infected persistently with exogenous HHV‐6 strains that lead to a wide range of neurological symptoms; the proposed name for this condition is inherited herpesvirus 6 syndrome or IHS. J Med. Virol. 85:1940–1946, 2013.

Retinal necrosis in X-linked lymphoproliferative disease

BACKGROUND X-linked lymphoproliferative disease is a hereditary disease that renders the males susceptible to fatal infectious mononucleosis, aplastic anemia, malignant lymphoma, and hypogammaglobulinemia after infection by the Epstein-Barr virus. METHODS The authors examined the clinical and pathologic findings in an 8-year-old boy with bilateral retinal necrosis who died with aplastic anemia as a complication of X-linked lymphoproliferative disease. RESULTS Results of histopathologic examination of the eyes disclosed retinal necrosis, and examination using the polymerase chain reaction technique showed Epstein-Barr virus genomic DNA in the left eye. CONCLUSION Retinal necrosis may be part of the expanding spectrum of X-linked lymphoproliferative disease. It is unknown if the retinal necrosis is due directly to Epstein-Barr virus infection or a host inflammatory response.

Characterization of a human herpes virus-6 (HHV-6) and epstein-barr virus (EBV) associated leukemic cell line, J6-1

This report characterizes the J6-1 cell line derived from a Chinese acute myelomonocytic leukemia patient and previoulsy reported to be associated with EBV. These studies showed that J6-1 cells were also infected with HHV-6 as demonstrate at the DNA level by PCR and Southern blot hybridization and by expression of HHV-6 early membrane antigen on the J6-1 cell surface. Further characterization showed J6-1 was co-infected with EBV type 2. Generally, cells infected with EBV type 2 do not grow wellin vitro, However, J6-1, although difficult to maintainin vitro, has been growth for 15 years. Possibly, co-infection with HHV-6 confers this property. In this regard, J6-1 cells exhibited density dependent growth which could be inhibited with an anti-HHV-6-MA monoclonal antibody (MAb). In contrast, anti-HHV-6-VCA MAb stimulate the J6-1 cell proliferation. Electron microscopic analysis showed that, morphologically, there were two types of J6-1 cell, one with lymphoblastoid features and one with a monocytoid appearance. Accordingly, the flow profile of the J6-1 cell line showed heterogeneity with two populations comprised of CD15-, CD19+cells with low light scatter (small cells) and a population with greater light scatter (larger cells) which was CD15+, CD19+, The population was negative for progenitor cell markers (CD33, 34), and T cell markers. Southern analysis showed no T cell receptor rearrangement, however there was a clonal JH and kappa light chain expressing population. Glycocytochemical analysis showed several endogenous lectin receptors on the J6-1 cell surface: BSA-Xylose, BSA-Rhamnose, BSA-Gal, BSA-Lac. This cell line shares many characteristics with other monocytic/lymphoblastoid cell lines isolated elsewhere and provides circumstantial evidence linking Herpes viruses, as least as co-factors, to leukemia cell growth.

Activation of Epstein-Barr virus in latently infected cell lines.

Several methods that can switch between latency and replication of Epstein-Barr virus (EBV) have been developed. These methods made it possible to identify and characterize the majority of virus proteins associated with the virus replication and to develop new assays for diagnosis. A possible activator protein encoded from the BamHI Z fragment of EBV genome, which can disrupt latency in EBV-genome positive cell lines, has also been identified. The developments in activation of the virus lytic cycle will be reviewed in this paper.

Chapter 10 Interactions between HHV-6 and other viruses

Publisher Summary HHV-6 has been most commonly isolated from the peripheral blood of immunocompromised individuals, including patients with acquired immunodeficiency syndrome (AIDS). HHV-6 isolates have also been obtained from patients with autoimmune disorders—another category of individuals with severe immunologic dysfunctions. This chapter provides a strong motivation to study the interactions between HHV-6 and different viral agents, particularly human immunodeficiency virus (HIV) or other viruses targeting the immune system. This chapter also gives a brief overview of interactions between HHV-6 and HIV-I, HHV-6 and HTLV-I, HHV-6 and the Epstein–Barr virus (EBV), and between HHV-6 and the human cytomegalovirus HCMV.

Chapter 5 Infection, latency and immortalization of human cells with HHV-6

Publisher Summary This chapter discusses the infection, latency, and immortalization of human cells with HHV-6. Human herpesvirus-6 (HHV-6) classified as lymphotropic herpesvirus was discovered by Salahuddin. Human herpesvirus-6, originally named human B lymphotropic virus (HBLV), has shown to be tropic for T cells, some B cells, and fibroblasts. This virus readily infects mitogen-activated human cord blood and peripheral blood mononuclear cells in vitro. Studies have shown that whether the latency of HHV-6 could be associated with neoplasia of T cell origin, and whether the immortalized CDC positive cells may play a role in the development of AIDS. This chapter also presents the in vitro infection and replication of human cells and latency of HHV-6 to explore target cells for permissive replication and to shed some light on how HHV-6, under the right circumstances, could be capable of immortalizing T cells.