Clinical impact of primary infection with roseoloviruses

Tesini, Brenda; Epstein, Leon G.; Caserta, Mary T.

doi:10.1016/j.coviro.2014.09.013

Cited by 75 publications

(68 citation statements)

References 46 publications

(62 reference statements)

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“…At an even earlier period of life, congenital infection following intrauterine transmission has been reported for about 1% of children, a frequency close to that observed with HCMV, and cases of perinatal transmission have been described (79)(80)(81)(82). As described below, congenital infection is mainly linked with ciHHV-6 in mothers (78). Primary infection can also happen later, in adults, as reported in a few cases (83).…”

Section: Human Infection Epidemiologymentioning

confidence: 87%

“…HHV-6 infection is usually acquired very early in life, between 6 months and 2 years of age, following the loss of protective maternal antibodies (78). At an even earlier period of life, congenital infection following intrauterine transmission has been reported for about 1% of children, a frequency close to that observed with HCMV, and cases of perinatal transmission have been described (79)(80)(81)(82).…”

Section: Human Infection Epidemiologymentioning

confidence: 99%

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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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Section: Human Infection Epidemiologymentioning

confidence: 87%

Section: Human Infection Epidemiologymentioning

confidence: 99%

Laboratory and Clinical Aspects of Human Herpesvirus 6 Infections

2015

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“…HHV-6 is subclassified into two distinct variants, HHV-6A and HHV-6B, which are considered independent viruses but share major genome sequence homologies and epidemiologies (3,4). Similarly to other members of the herpesvirus family, HHV-6 causes a relatively short and mild primary disease called roseola infantum, usually in children up to the age of 2 years, with a sudden rise of fever and rash as major symptoms (5). Following this initial infection, HHV-6 establishes lifelong latency in about 90% of all individuals examined (2).…”

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confidence: 99%

Human Herpesvirus 6B Downregulates Expression of Activating Ligands during Lytic Infection To Escape Elimination by Natural Killer Cells

Schmiedel

Tai

Levi‐Schaffer

et al. 2016

J Virol

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The Herpesviridae family consists of eight viruses, most of which infect a majority of the human population. One of the lessstudied members is human herpesvirus 6 (HHV-6) (Roseolovirus), which causes a mild, well-characterized childhood disease. Primary HHV-6 infection is followed by lifelong latency. Reactivation frequently occurs in immunocompromised patients, such as those suffering from HIV infection or cancer or following transplantation, and causes potentially life-threatening complications. In this study, we investigated the mechanisms that HHV-6 utilizes to remain undetected by natural killer (NK) cells, which are key participants in the innate immune response to infections. We revealed viral mechanisms which downregulate ligands for two powerful activating NK cell receptors: ULBP1, ULBP3, and MICB, which trigger NKG2D, and B7-H6, which activates NKp30. Accordingly, this downregulation impaired the ability of NK cells to recognize HHV-6-infected cells. Thus, we describe for the first time immune evasion mechanisms of HHV-6 that protect lytically infected cells from NK elimination. IMPORTANCEHuman herpesvirus 6 (HHV-6) latently infects a large portion of the human population and can reactivate in humans lacking a functional immune system, such as cancer or AIDS patients. Under these conditions, it can cause life-threatening diseases. To date, the actions and interplay of immune cells, and particularly cells of the innate immune system, during HHV-6 infection are poorly defined. In this study, we aimed to understand how cells undergoing lytic HHV-6 infection interact with natural killer (NK) cells, innate lymphocytes constituting the first line of defense against viral intruders. We show that HHV-6 suppresses the expression of surface proteins that alert the immune cells by triggering two major receptors on NK cells, NKG2D and NKp30. As a consequence, HHV-6 can replicate undetected by the innate immune system and potentially spread infection throughout the body. This study advances the understanding of HHV-6 biology and the measures it uses to successfully escape immune elimination. Human herpesvirus 6 (HHV-6) (Roseolovirus) was long neglected in research and medical diagnostics; however, in the past few years, it gained increasing attention. A variety of clinical complications were found to be associated with HHV-6 infection, especially concerning immunocompromised patients, in whom it has the ability to cause severe morbidity and mortality (1, 2). HHV-6 is subclassified into two distinct variants, HHV-6A and HHV-6B, which are considered independent viruses but share major genome sequence homologies and epidemiologies (3,4). Similarly to other members of the herpesvirus family, HHV-6 causes a relatively short and mild primary disease called roseola infantum, usually in children up to the age of 2 years, with a sudden rise of fever and rash as major symptoms (5). Following this initial infection, HHV-6 establishes lifelong latency in about 90% of all individuals examined (2). Reactivation frequentl...

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“…HHV-6B is a ubiquitous virus that infects almost 100% of the human population. It is the etiological agent of the febrile illness roseola infantum, also known as the sixth childhood eruptive disease (2,3). Reactivation of HHV-6B in immunosuppressed individuals is associated with adverse clinical outcomes, including life-threatening encephalitis or graft rejection in transplant patients (4).…”

mentioning

confidence: 99%

Stabilization of Telomere G-Quadruplexes Interferes with Human Herpesvirus 6A Chromosomal Integration

Gilbert-Girard

Gravel

Artusi

et al. 2017

J Virol

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Human herpesviruses 6A and 6B (HHV-6A/B) can integrate their genomes into the telomeres of human chromosomes using a mechanism that remains poorly understood. To achieve a better understanding of the HHV-6A/B integration mechanism, we made use of BRACO-19, a compound that stabilizes G-quadruplex secondary structures and prevents telomere elongation by the telomerase complex. First, we analyzed the folding of telomeric sequences into G-quadruplex structures and their binding to BRACO-19 using G-quadruplex-specific antibodies and surface plasmon resonance. Circular dichroism studies indicate that BRACO-19 modifies the conformation and greatly stabilizes the G-quadruplexes formed in G-rich telomeric DNA. Subsequently we assessed the effects of BRACO-19 on the HHV-6A initial phase of infection. Our results indicate that BRACO-19 does not affect entry of HHV-6A DNA into cells. We next investigated if stabilization of G-quadruplexes by BRACO-19 affected HHV-6A's ability to integrate its genome into host chromosomes. Incubation of telomerase-expressing cells with BRACO-19, such as HeLa and MCF-7, caused a significant reduction in the HHV-6A integration frequency (P Ͻ 0.002); in contrast, BRACO-19 had no effect on HHV-6 integration frequency in U2OS cells that lack telomerase activity and elongate their telomeres through alternative lengthening mechanisms. Our data suggest that the fluidity of telomeres is important for efficient chromosomal integration of HHV-6A and that interference with telomerase activity negatively affects the generation of cellular clones containing integrated HHV-6A.IMPORTANCE HHV-6A/B can integrate their genomes into the telomeres of infected cells. Telomeres consist of repeated hexanucleotides (TTAGGG) of various lengths (up to several kilobases) and end with a single-stranded 3= extension. To avoid recognition and induce a DNA damage response, the single-stranded overhang folds back on itself and forms a telomeric loop (T-loop) or adopts a tertiary structure, referred to as a G-quadruplex. In the current study, we have examined the effects of a G-quadruplex binding and stabilizing agent, BRACO-19, on HHV-6A chromosomal integration. By stabilizing G-quadruplex structures, BRACO-19 affects the ability of the telomerase complex to elongate telomeres. Our results indicate that BRACO-19 reduces the number of clones harboring integrated HHV-6A. This study is the first of its kind and suggests that telomerase activity is essential to restore a functional telomere of adequate length following HHV-6A integration.

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Clinical impact of primary infection with roseoloviruses

Cited by 75 publications

References 46 publications

Laboratory and Clinical Aspects of Human Herpesvirus 6 Infections

Laboratory and Clinical Aspects of Human Herpesvirus 6 Infections

Human Herpesvirus 6B Downregulates Expression of Activating Ligands during Lytic Infection To Escape Elimination by Natural Killer Cells

Stabilization of Telomere G-Quadruplexes Interferes with Human Herpesvirus 6A Chromosomal Integration

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