Chromosomally integrated HHV-6: impact on virus, cell and organismal biology

Kaufer, Benedikt B.; Flamand, Louis

doi:10.1016/j.coviro.2014.09.010

Cited by 97 publications

(99 citation statements)

References 69 publications

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“…The expression kinetics of U94 have been classified as those of either an IE (24,25) or an E (23) gene. Biochemical data suggest that the U94 protein could facilitate integration (2,3,13). However, despite some growth defects, an HHV-6A U94 deletion mutant proved as efficient as WT HHV-6A at integrating host chromosomes, indicating that U94 is dispensable for HHV-6A integration (14).…”

Section: Discussionmentioning

confidence: 97%

Cell Culture Systems To Study Human Herpesvirus 6A/B Chromosomal Integration

Gravel¹,

Dubuc²,

Wallaschek

et al. 2017

J Virol

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Human herpesviruses 6A/B (HHV-6A/B) can integrate their viral genomes in the telomeres of human chromosomes. The viral and cellular factors contributing to HHV-6A/B integration remain largely unknown, mostly due to the lack of efficient and reproducible cell culture models to study HHV-6A/B integration. In this study, we characterized the HHV-6A/B integration efficiencies in several human cell lines using two different approaches. First, after a short-term infection (5 h), cells were processed for single-cell cloning and analyzed for chromosomally integrated HHV-6A/B (ciHHV-6A/B). Second, cells were infected with HHV-6A/B and allowed to grow in bulk for 4 weeks or longer and then analyzed for the presence of ciHHV-6. Using quantitative PCR (qPCR), droplet digital PCR, and fluorescent in situ hybridization, we could demonstrate that HHV-6A/B integrated in most human cell lines tested, including telomerase-positive (HeLa, MCF-7, HCT-116, and HEK293T) and telomerase-negative cell lines (U2OS and GM847). Our results also indicate that inhibition of DNA replication, using phosphonoacetic acid, did not affect HHV-6A/B integration. Certain clones harboring ciHHV-6A/B spontaneously express viral genes and proteins. Treatment of cells with phorbol ester or histone deacetylase inhibitors triggered the expression of many viral genes, including U39, U90, and U100, without the production of infectious virus, suggesting that the tested stimuli were not sufficient to trigger full reactivation. In summary, both integration models yielded comparable results and should enable the identification of viral and cellular factors contributing to HHV-6A/B integration and the screening of drugs influencing viral gene expression, as well as the release of infectious HHV-6A/B from the integrated state.IMPORTANCE The analysis and understanding of HHV-6A/B genome integration into host DNA is currently limited due to the lack of reproducible and efficient viral integration systems. In the present study, we describe two quantitative cell culture viral integration systems. These systems can be used to define cellular and viral factors that play a role in HHV-6A/B integration. Furthermore, these systems will allow us to decipher the conditions resulting in virus gene expression and excision of the integrated viral genome resulting in reactivation.KEYWORDS chromosomal integration, ddPCR, telomere

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Section: Discussionmentioning

confidence: 97%

Cell Culture Systems To Study Human Herpesvirus 6A/B Chromosomal Integration

Gravel¹,

Dubuc²,

Wallaschek

et al. 2017

J Virol

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“…However, these findings were not based on a comparison with nonhuman roseolovirus; our MRV genome sequence should shed additional light on roseolovirus-specific genes. HHV-6 has been reported to integrate in the telomeres of human chromosomes, while HHV-7 has not been observed to have this property (50)(51)(52). HHV-6 integration appears to be dependent on DR sequences at both ends of its genome, mirroring the hexameric TTAGGG sequence in human telomeres (53).…”

Section: Discussionmentioning

confidence: 99%

A Murine Herpesvirus Closely Related to Ubiquitous Human Herpesviruses Causes T-Cell Depletion

Patel

Zhao

Penna

et al. 2017

J Virol

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The human roseoloviruses human herpesvirus 6A (HHV-6A), HHV-6B, and HHV-7 comprise the Roseolovirus genus of the human Betaherpesvirinae subfamily. Infections with these viruses have been implicated in many diseases; however, it has been challenging to establish infections with roseoloviruses as direct drivers of pathology, because they are nearly ubiquitous and display species-specific tropism. Furthermore, controlled study of infection has been hampered by the lack of experimental models, and until now, a mouse roseolovirus has not been identified. Herein we describe a virus that causes severe thymic necrosis in neonatal mice, characterized by a loss of CD4 ϩ T cells. These phenotypes resemble those caused by the previously described mouse thymic virus (MTV), a putative herpesvirus that has not been molecularly characterized. By next-generation sequencing of infected tissue homogenates, we assembled a contiguous 174-kb genome sequence containing 128 unique predicted open reading frames (ORFs), many of which were most closely related to herpesvirus genes. Moreover, the structure of the virus genome and phylogenetic analysis of multiple genes strongly suggested that this virus is a betaherpesvirus more closely related to the roseoloviruses, HHV-6A, HHV-6B, and HHV-7, than to another murine betaherpesvirus, mouse cytomegalovirus (MCMV). As such, we have named this virus murine roseolovirus (MRV) because these data strongly suggest that MRV is a mouse homolog of HHV-6A, HHV-6B, and HHV-7.IMPORTANCE Herein we describe the complete genome sequence of a novel murine herpesvirus. By sequence and phylogenetic analyses, we show that it is a betaherpesvirus most closely related to the roseoloviruses, human herpesviruses 6A, 6B, and 7. These data combined with physiological similarities with human roseoloviruses collectively suggest that this virus is a murine roseolovirus (MRV), the first definitively described rodent roseolovirus, to our knowledge. Many biological and clinical ramifications of roseolovirus infection in humans have been hypothesized, but studies showing definitive causative relationships between infection and disease susceptibility are lacking. Here we show that MRV infects the thymus and causes T-cell depletion, suggesting that other roseoloviruses may have similar properties.KEYWORDS herpesviruses, roseolovirus T he study of herpesviruses has been fruitful, not only revealing mechanisms that drive disease but also providing insight into diverse processes, including oncogenesis and immune regulation (1). The Herpesviridae family includes several highly prevalent human pathogens (1-3). While they are related, these viruses have diverse genomes,

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“…This phenomenon was further reported to be present in human cells in vivo, including cells which can be transmitted as germinal cells to offspring and hematopoietic stem cells transferred to a transplant recipient (64,65). It appears to be a unique feature among human herpesviruses and raises numerous novel questions regarding both pathophysiology and diagnosis (25,66). The covalent linkage between viral and cellular DNAs occurs within the subtelomeric region of chromosomes, likely by a mechanism of homologous recombination between telomeric repeat sequences of viral and cellular origins.…”

Section: Chromosomal Integrationmentioning

confidence: 99%

“…These repeated sequences likely play a major role in the process of chromosomal integration of the HHV-6 genome (ciHHV-6) (see below). This integration has been reported to occur through a junction between host chromosomes and the perfect telomeric repeats at the right end of DR R (23)(24)(25). The overall number of protein-encoding open reading frames (ORFs) is about 110 to 120 according to the different published nucleotide sequences (26)(27)(28).…”

Section: Genome and Genetic Variabilitymentioning

confidence: 99%

Laboratory and Clinical Aspects of Human Herpesvirus 6 Infections

2015

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SUMMARY Human herpesvirus 6 (HHV-6) is a widespread betaherpesvirus which is genetically related to human cytomegalovirus (HCMV) and now encompasses two different species: HHV-6A and HHV-6B. HHV-6 exhibits a wide cell tropism in vivo and, like other herpesviruses, induces a lifelong latent infection in humans. As a noticeable difference with respect to other human herpesviruses, genomic HHV-6 DNA is covalently integrated into the subtelomeric region of cell chromosomes (ciHHV-6) in about 1% of the general population. Although it is infrequent, this may be a confounding factor for the diagnosis of active viral infection. The diagnosis of HHV-6 infection is performed by both serologic and direct methods. The most prominent technique is the quantification of viral DNA in blood, other body fluids, and organs by means of real-time PCR. Many active HHV-6 infections, corresponding to primary infections, reactivations, or exogenous reinfections, are asymptomatic. However, the virus may be the cause of serious diseases, particularly in immunocompromised individuals. As emblematic examples of HHV-6 pathogenicity, exanthema subitum, a benign disease of infancy, is associated with primary infection, whereas further virus reactivations can induce severe encephalitis cases, particularly in hematopoietic stem cell transplant recipients. Generally speaking, the formal demonstration of the causative role of HHV-6 in many acute and chronic human diseases is difficult due to the ubiquitous nature of the virus, chronicity of infection, existence of two distinct species, and limitations of current investigational tools. The antiviral compounds ganciclovir, foscarnet, and cidofovir are effective against active HHV-6 infections, but the indications for treatment, as well as the conditions of drug administration, are not formally approved to date. There are still numerous pending questions about HHV-6 which should stimulate future research works on the pathophysiology, diagnosis, and therapy of this remarkable human virus.

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Chromosomally integrated HHV-6: impact on virus, cell and organismal biology

Cited by 97 publications

References 69 publications

Cell Culture Systems To Study Human Herpesvirus 6A/B Chromosomal Integration

Cell Culture Systems To Study Human Herpesvirus 6A/B Chromosomal Integration

A Murine Herpesvirus Closely Related to Ubiquitous Human Herpesviruses Causes T-Cell Depletion

Laboratory and Clinical Aspects of Human Herpesvirus 6 Infections

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