Detection of human herpesvirus 7 DNA in peripheral blood reflects mainly CD4+ cell count in patients infected with HIV

Human herpesvirus-7 meningitis in an immunocompetent adult patient: a case report

Aim

The underlying pathological mechanisms of CNS human herpesvirus-7 (HHV-7) related infections are still unknown, especially among immunocompetent adults. Although HHV-7 meningitis in immunocompetent adults is usually uncommon, serious consideration for possible HHV-7 involvement should be taken when assessing CNS infection of unknown etiology.

Case presentation

We report a 53-year-old female who presented for fever and progressive headaches. Cerebrospinal fluid (CSF) analysis was compatible with a viral meningitis. CSF cultures were negative and HHV-7 DNA was the only strain detected in the CSF analysis. The patient died 1 month later following complications and cardiac arrest.

Conclusion

HHV-7 CNS infection in immunocompetent patient can be a serious infection. Prompt diagnosis and treatment management are essential for better outcome.

Human Herpesviruses 6A, 6B, and 7

Human roseoloviruses include three different species, human herpesviruses 6A, 6B, and 7 (HHV-6A, HHV-6B, HHV-7), genetically related to human cytomegalovirus. They exhibit a wide cell tropism in vivo and, like other herpesviruses, induce a lifelong latent infection in humans. In about 1% of the general population, HHV-6 DNA is covalently integrated into the subtelomeric region of cell chromosomes (ciHHV-6). Many active infections, corresponding to primary infections, reactivations, or exogenous reinfections, are asymptomatic. They also may cause serious diseases, particularly in immunocompromised individuals, including hematopoietic stem-cell transplant (HSCT) and solid-organ transplant recipients, and acquired immunodeficiency syndrome (AIDS) patients. This opportunistic pathogenic role is formally established for HHV-6 infection and less clear for HHV-7. It mainly concerns the central-nervous system, bone marrow, lungs, gastrointestinal tract, skin, and liver. As the best example, HHV-6 causes both exanthema subitum, a benign disease associated with primary infection, and severe encephalitis associated with virus reactivations in HSCT recipients. Diagnosis using serologic and direct antigen-detection methods currently exhibits limitations. The most prominent technique is the quantification of viral DNA in blood, other body fluids, and organs by means of real-time polymerase-chain reaction (PCR). The antiviral compounds ganciclovir, foscarnet, and cidofovir are effective against active infections, but there is currently no consensus regarding the indications of treatment or specifics of drug administration. Numerous questions about HHV-6A, HHV-6B, HHV-7 are still pending, concerning in particular clinical impact and therapeutic options in immunocompromised patients.

Cytokine and cellular responses to human herpesvirus-6B in patients with B-acute lymphoblastic leukemia

Primary infection with human herpesvirus-6 (HHV-6), is followed by its lifelong persistence in the host. Most T-cell responses to HHV-6 have been characterized using peripheral blood from healthy adults; however, the role of HHV-6 infection in immune modulation has not been elucidated for some diseases. Therefore, in this study the immune response to HHV-6 infection in patients with B-acute lymphoblastic leukemia (B-ALL) was analyzed. HHV-6 load was quantified in blood samples taken at the time of diagnosis of leukemia and on remission. The same concentrations of anti- and pro-inflammatory cytokines (IL-4, IL-1, IL-6, IL-8, IL-12p70, IL-17a, TNF-α and IFN-γ) were detected in plasma samples from 20 patients with and 20 without detectable HHV-6 virus loads in blood. Characterization of T-cell responses to HHV-6 showed low specific T-cells frequencies of 2.08% and 1.46% in patients with and without detectable viral loads, respectively. IFN-γ-producing T cells were detected in 0.03%-0.23% and in 0%-0.2% of CD4+T cells, respectively. Strong production of IL-6 was detected in medium supernatants of challenged T-cells whatever the HHV-6 status of the patients (973.51 ± 210.06 versus 825.70 ± 210.81 pg/mL). However, concentrations of TNF-α and IFN-γ were low. Thus, no association between plasma concentrations of cytokines and detection of HHV-6 in blood was identified, suggesting that HHV-6 is not strongly associated with development of B-ALL. The low viral loads detected may correspond with latently infected cells. Alternatively, HHV-6B specific immune responses may be below the detection threshold of the assays used.

Update on infections with human herpesviruses 6A, 6B, and 7

Human herpesviruses 6A, 6B, and 7 (HHV-6A, HHV-6B, HHV-7) are genetically related to cytomegalovirus. They belong to the Roseolovirus genus and to the Betaherpesvirinae subfamily. They infect T cells, monocytes-macrophages, epithelial cells, and central nervous system cells. These viruses are ubiquitous and are responsible for lifelong chronic infections, most often asymptomatic, in the vast majority of the general adult population. HHV-6B is responsible for exanthema subitum, which is a benign disease of infants. HHV-6A and HHV-6B also cause opportunistic infections in immunocompromised patients: encephalitis, hepatitis, bone marrow suppression, colitis, and pneumonitis. Their etiological role in chronic diseases such as multiple sclerosis, cardiomyopathy, and thyroiditis is still controversial. The pathogenicity of HHV-7 is less clear and seems to be much more restricted. Chromosomal integration of HHV-6A and HHV-6B is transmissible from parents to offspring and observed in about 1% of the general population. This integration raises the question of potential associated diseases and can be a confounding factor for the diagnosis of active infections by both viruses. The diagnosis of HHV-6A, HHV-6B, and HHV-7 infections is rather based on gene amplification (PCR), which allows for the detection and quantification of the viral genome, than on serology, which is mainly indicated in case of primary infection. Ganciclovir, foscarnet, and cidofovir inhibit the replication of HHV-6A, HHV-6B, and HHV-7. Severe infections may thus be treated but these therapeutic indications are still poorly defined.

Detection of human herpesvirus 7 DNA from the CSF in association with neurosarcoidosis

This study reports a previously healthy, immunocompetent adult male in whom human herpesvirus 7 (HHV-7) DNA was detected continuously from the cerebrospinal fluid (CSF). This patient developed definite sarcoidosis with primary symptomatic manifestations in the central nervous system (CNS). The initial presentation was with loss of visual acuity and papilledema. Brain MR imaging at presentation confirmed papilledema, but otherwise there were no focal abnormalities or signs of hydrocephalus. CSF investigation revealed pleocytosis and elevated protein levels. HHV-7 DNA was detected repeatedly from CSF but not from blood over 1 year follow-up. High resolution computed tomography of lungs was normal. Positron emission tomography showed several metabolically active lymph nodes in the mediastinum, and the histopathological investigation revealed granulomatous inflammation consistent with sarcoidosis. The finding of HHV-7 DNA in the CSF in the context of neurosarcoidosis has not been reported previously. The detection of HHV-7 DNA may result from the selective activation of CD4+ T-lymphocytes in the CSF caused by neurosarcoidosis. Further studies are needed to establish whether the detection of HHV-7 DNA in the CSF in association with neurosarcoidosis represents a clinically significant HHV-7 CNS infection.

Human herpesvirus 6 and 7 in febrile status epilepticus: the FEBSTAT study

PURPOSE

In a prospective study, Consequences of Prolonged Febrile Seizures in Childhood (FEBSTAT), we determined the frequency of human herpesvirus (HHV)-6 and HHV-7 infection as a cause of febrile status epilepticus (FSE).

METHODS

Children ages 1 month to 5 years presenting with FSE were enrolled within 72 h and received a comprehensive assessment including specimens for HHV-6 and HHV-7. The presence of HHV-6A, HHV-6B, or HHV-7 DNA and RNA (amplified across a spliced junction) determined using quantitative polymerase chain reaction (qPCR) at baseline indicated viremia. Antibody titers to HHV-6 and HHV-7 were used in conjunction with the PCR results to distinguish primary infection from reactivated or prior infection.

KEY FINDINGS

Of 199 children evaluated, HHV-6 or HHV-7 status could be determined in 169 (84.9%). HHV-6B viremia at baseline was found in 54 children (32.0%), including 38 with primary infection and 16 with reactivated infection. No HHV-6A infections were identified. HHV-7 viremia at baseline was observed in 12 children (7.1%), including eight with primary infection and four with reactivated infection. Two subjects had HHV-6/HHV-7 primary coinfection at baseline. There were no differences in age, characteristics of illness or fever, seizure phenomenology or the proportion of acute EEG or imaging abnormalities in children presenting with FSE with or without HHV infection.

SIGNIFICANCE

HHV-6B infection is commonly associated with FSE. HHV-7 infection is less frequently associated with FSE. Together, they account for one third of FSE, a condition associated with an increased risk of both hippocampal injury and subsequent temporal lobe epilepsy.

Consistent inhibition of HIV-1 replication in CD4+ T cells by acyclovir without detection of human herpesviruses

Acyclovir, a nucleoside analog, is thought to be specific for the human herpesviruses because it requires a virally encoded enzyme to phosphorylate it to acyclovir monophosphate. Recently, acyclovir triphosphate was shown to be a direct inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase. Here, we showed that acyclovir is an inhibitor of HIV-1 replication in CD4(+) T cells from cord blood that have undetectable levels of the eight human herpesviruses. Additionally, acyclovir phosphates were detected by reverse-phase-high performance liquid chromatography (RP-HPLC) and quantified in a primer extension assay from cord blood. The data support acyclovir as an inhibitor of HIV-1 replication in herpesvirus-negative cells.

Viral interactions in human lymphoid tissue: Human herpesvirus 7 suppresses the replication of CCR5-tropic human immunodeficiency virus type 1 via CD4 modulation

Human immunodeficiency virus (HIV) infection is often accompanied by infection with other pathogens that affect the clinical course of HIV disease. Here, we identified another virus, human herpesvirus 7 (HHV-7) that interferes with HIV type 1 (HIV-1) replication in human lymphoid tissue, where critical events of HIV disease occur. Like the closely related HHV-6, HHV-7 suppresses the replication of CCR5-tropic (R5) HIV-1 in coinfected blocks of human lymphoid tissue. Unlike HHV-6, which affects HIV-1 by upregulating RANTES, HHV-7 did not upregulate any CCR5-binding chemokine. Rather, the inhibition of R5 HIV-1 by HHV-7 was associated with a marked downregulation of CD4, the cellular receptor shared by HHV-7 and HIV-1. HHV-7-induced CD4 downregulation was sufficient for HIV-1 inhibition, since comparable downregulation of CD4 with cyclotriazadisulfonamide, a synthetic macrocycle that specifically modulates expression of CD4, resulted in the suppression of HIV infection similar to that seen in HHV-7-infected tissues. In contrast to R5 HIV-1, CXCR4-tropic (X4) HIV-1 was only minimally suppressed by HHV-7 coinfection. This selectivity in suppression of R5 and X4 HIV-1 is explained by a suppression of HHV-7 replication in X4- but not in R5-coinfected tissues. These results suggest that HIV-1 and HHV-7 may interfere in lymphoid tissue in vivo, thus potentially affecting the progression of HIV-1 disease. Knowledge of the mechanisms of interaction of HIV-1 with HHV-7, as well as with other pathogens that modulate HIV-1 replication, may provide new insights into HIV pathogenesis and lead to the development of new anti-HIV therapeutic strategies.

Identification of human herpesvirus 6 variants A and B by primer-specific real-time PCR may help to revisit their respective role in pathology

BACKGROUND

Human herpesvirus 6 (HHV-6) isolates are classified into two variants, termed HHV-6A and HHV-6B, on the basis of distinct genetic, antigenic and biological characteristics, but the specific pathogenicity of each variant remains poorly understood.

OBJECTIVES

To design a rapid, sensitive and specific real-time variant-specific PCR (VS-PCR) method to differentiate both variants in biological specimens.

STUDY DESIGN

The VS-PCR was adapted from a real-time PCR assay, based on TaqMan technology, previously developed for the genome quantitation of both HHV-6 variants [Gautheret-Dejean A, Manichanh C, Thien-Ah-Koon F, Fillet AM, Mangeney N, Vidaud M, et al. Development of a real-time polymerase chain reaction assay for the diagnosis of human herpesvirus-6 infection and application to bone marrow transplant patients. J Virol Meth 2002;100:27-35], a consensual reverse primer (Taq2) being changed into two variant-specific primers named H6A and H6B. This method was applied to a large set of biological specimens obtained in different pathological contexts.

RESULTS

The sensitivity threshold was about 10 copies/well for HHV-6A-specific PCR (PCR-A) and 1 copy/well for HHV-6B-specific PCR (PCR-B). Both assays showed a linear dynamic range from 10 to 100,000 copies of HHV-6 DNA. Regarding the specificity and the capacity of discrimination of each assay, one variant could be detected and identified in the presence of more than 1000 times higher concentrations of the other variant in virus mixtures. The comparison of the results obtained with this VS-PCR with those previously obtained with a classic PCR method allowed us to validate our new technique on a wide panel of biological samples, including numerous patients with severe HHV-6-related symptoms. The high prevalence of HHV-6B was confirmed in healthy individuals and immunocompromised patients. HHV-6A was identified in distinct samples from several patients exhibiting neurological disorders.

CONCLUSIONS

We developed a new VS-PCR assay, able to differentiate HHV-6A and HHV-6B in biological samples, even in the case of mixed infections. Our study confirms the wide prevalence of HHV-6B and highlights the potential greater neuropathogenic role of HHV-6A in immunocompromised patients and young infants.