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    Prevalence and distribution of human herpesvirus 6 variants A and B in adult human brain
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    Abstract:
    The presence of human herpesvirus 6 (HHV-6) in brain tissues of 40 consecutive post-mortem cases was examined. For each case, autopsy samples were collected from the cerebellum, frontal, temporal, parietal and occipital lobes of both sides of the brain. HHV-6 DNA was detected by nested polymerase chain reaction and characterised into variants A and B. Overall, 97/400 (24.3%) samples were positive for HHV-6 DNA with 16 being variant A and 81 being variant B, but none of the samples harboured both variants. When analysed by patient, 34/40 (85%) had HHV-6 DNA detected in the brain. The viral DNA positivity did not show significant variation with gender and age. Four patients harboured variant A, 23 harboured variant B, and seven had both variants at different positions. The results indicate that both HHV-6A and HHV-6B are neurotropic and human brain may be another site for latency. HHV-6B was detected in brain tissues of a majority (75%) of the studied population and with a widespread distribution within the brain. Although the observed prevalence of HHV-6A in brain is lower (27.5%), in view of its lower seroprevalence, the neuroinvasive potential of variant A may be comparable to that of variant B. Although both variants are potential pathogens for the nervous system, the fact that they can exist, probably for most of the time, as commensals in human brain needs to be considered when interpreting their roles in neuropathology.
    Keywords:
    Neuropathology
    Human brain
    Human herpesvirus 6
    Blood samples from human immunodeficiency virus (HIV)-positive patients were monitored for cytomegalovirus (CMV), human herpesvirus 6 (HHV-6), and HHV-7 by PCR. We detected CMV in 17% of the patients, HHV-6 in 6%, and HHV-7 in 3%. The viral loads of CMV were significantly higher than those of HHV-6 (P = 0.007) or HHV-7 (P = 0.01). Detection of CMV and HHV-6 was associated with low and high CD4 counts, respectively.
    Human herpesvirus 6
    Cytomegalovirus
    Betaherpesvirinae
    Cytomegalovirus infections

    Objectives

    To discuss the current knowledge of 3 recently discovered human herpesviruses (HHV-6, HHV-7, and HHV-8), and to provide a dermatological point of view.

    Data Sources

    References identified from bibliographies of pertinent articles in the English language.

    Study Selection and Data Extraction

    Articles were selected according to their impact factor and the interest for dermatologists.

    Data Synthesis

    As the other members of the family Herpesviridae, HHV-6, HHV-7, and HHV-8 may cause a primary infection, establish latent infection in a specific set of cells of their host, and then reactivate if conditions of altered immunity develop. The main pathological conditions associated with them are discussed.

    Conclusions

    Human herpesvirus 6, HHV-7, and HHV-8 have provided new insights in some dermatological diseases. Although new studies are needed, they may have a profound impact on dermatology in the years to come.
    Citations (34)
    The association of psoriasis with latent human herpesvirus infection has not been well described. To better understand the relationship between severe psoriasis and its treatment with latent human herpesvirus infection, we performed a cross-sectional study to determine if patients with severe psoriasis and psoriasis patients treated with immunosuppressive therapies have higher rates of Epstein-Barr virus and human herpesvirus 6 replication compared to healthy controls. The prevalence of Epstein-Barr virus and human herpesvirus 6 replication was measured in white blood cells by quantitative polymerase chain reaction. We found no evidence of active viral replication in white blood cells of healthy controls (0/10; 95% confidence interval 0-0.26), patients with severe psoriasis (0/25; 95% confidence interval 0-0.11) or severe psoriasis patients on immunosuppressive treatment (0/26; 95% confidence interval 0-0.11). The results of this study suggest that neither severe psoriasis alone, nor in combination with immunosuppressive therapy, is associated with an increase in Epstein-Barr virus or human herpesvirus 6 replication in white blood cells.
    Human herpesvirus 6
    Gammaherpesvirinae
    Immunosuppression
    Citations (5)
    We present a case report of a meningoradiculopathy associated with human herpesvirus 7, with long-term motor neurologic sequelae. It is important to consider human herpesvirus 7 as a potential pathogen of severe neurologic disease and sequelae in immunocompetent children, especially in older patients presenting neurologic signs.
    Human herpesvirus 6
    Neurologic disease
    Human disease
    Human pathogen
    Human herpesvirus 6
    Varicella zoster virus
    Cytomegalovirus
    Alphaherpesvirinae
    Simplexvirus