HHV-6, 7 and their related diseases

Alzheimer's disease as a viral disease: Revisiting the infectious hypothesis

Alzheimer's disease (AD) represents the most frequent type of dementia in elderly people. Two major forms of the disease exist: sporadic - the causes of which have not yet been fully understood - and familial - inherited within families from generation to generation, with a clear autosomal dominant transmission of mutations in Presenilin 1 (PSEN1), 2 (PSEN2) or Amyloid Precursors Protein (APP) genes. The main hallmark of AD consists of extracellular deposits of amyloid-beta (Aβ) peptide and intracellular deposits of the hyperphosphorylated form of the tau protein. An ever-growing body of research supports the viral infectious hypothesis of sporadic forms of AD. In particular, it has been shown that several herpes viruses (i.e., HHV-1, HHV-2, HHV-3 or varicella zoster virus, HHV-4 or Epstein Barr virus, HHV-5 or cytomegalovirus, HHV-6A and B, HHV-7), flaviviruses (i.e., Zika virus, Dengue fever virus, Japanese encephalitis virus) as well as Human Immunodeficiency Virus (HIV), hepatitis viruses (HAV, HBV, HCV, HDV, HEV), SARS-CoV2, Ljungan virus (LV), Influenza A virus and Borna disease virus, could increase the risk of AD. Here, we summarized and discussed these results. Based on these findings, significant issues for future studies are also put forward.

Human Herpesviruses as Copathogens of HIV Infection, Their Role in HIV Transmission, and Disease Progression

Of eight human herpesviruses (HHVs), often, only herpes simplex virus types 1 (HSV-1) and 2 (HSV-2) find mention in medical literature as both of these viruses are commonly associated with genital lesions and oral ulcers, commonly known as cold sores. However, role of human herpesviruses as copathogens and in aggravation and in the transmission of other human diseases, especially the Acquired immunodeficiency syndrome (HIV/AIDS) has only very recently been recognized. Therefore, screening and treating subclinical HHV infections may offer slowing of HIV infection, disease progression, and its transmission. Beside HSV-1 and HSV-2, HHV-3 a causative agent of herpes zoster remained one of the first manifestations of HIV disease before the era of highly active antiretroviral therapy (HAART). HHV-5 also known as human Cytomegalovirus infection remains a significant risk factor for HIV-associated mortality and morbidity even in HAART era. It is proposed that Cytomegalovirus viremia could be a better predictor of HIV disease progression than CD4+ T-lymphocyte count. The role of HHV-4 or Epstein-Burr virus and HHV-6, HHV-7, and HHV-8 is still being investigated in HIV disease progression. This review provides insight into the current understanding about these 8 HHVs, their co-pathogenesis, and role in HIV/AIDS disease progression. The review also covers recent literature in favor and against administering anti-HHV treatment along with HAART for slower AIDS progression and interrupted sexual transmission.

DRESS syndrome associé à une pan-uvéite bilatérale : à propos d’un cas

INTRODUCTION

DRESS syndrome (drug rash or reaction with eosinophilia and systemic symptoms) is a rare but life-threatening drug hypersensitivity syndrome with a potential viral cofactor. The syndrome is characterized by rash, fever, hematological disorders (eosinophilia, lymphocytosis), and systemic symptoms (adenopathy, multiorgan involvement).

CASE REPORT

We report the first description of acute bilateral panuveitis with elevated intraocular pressure associated with anticonvulsant-induced DRESS syndrome, hypogammaglobulinemia, and HHV-6 reactivation in a 63-year-old-woman. Complete general and ophthalmological recovery was obtained 4 weeks after the end of anticonvulsant drug exposure without corticosteroid prescription, with the patient remaining free of disease after 6 months.

DISCUSSION

Our data suggest that uveitis may be one of multivisceral involvements described in drug hypersensitivity syndrome. The data also suggest that HHV-6 may play a role in the complex pathogenesis of DRESS as well as in the development of immune inflammatory disorders such as bilateral panuveitis with elevated intraocular pressure and alteration of retinal and choroidal circulation in this patient.

Human herpesvirus 6 encephalitis associated with hypersensitivity syndrome

Hypersensitivity syndrome, a serious systematic reaction to a limited number of drugs, is associated with the reactivation of human herpesvirus 6. A 56-year-old man developed acute limbic encephalitis followed by multiple organ failure during the course of toxic dermatitis induced by aromatic anticonvulsants. The clinical features of skin eruptions, high fever, eosinophilia, and atypical lymphocytosis were compatible with drug hypersensitivity syndrome. The patient showed seroconversion for human herpesvirus 6, and polymerase chain reaction detected human herpesvirus 6 DNA in the cerebrospinal fluid. To our knowledge, this is the first report of human herpesvirus 6 encephalitis associated with hypersensitivity syndrome.

Human herpesviruses 6 and 7

Human herpesviruses 6 and 7 are newly discovered viruses that belong to the genus Roseolavirus within the subfamily Betaherpesvirinae. These ubiquitous viruses may cause primary or chronic persistent infection or remain in a state of latency for many years, until a decrease in the immunologic state of the host leads to reactivation of infection. Several diseases have been linked with HHV-6 and HHV-7. In the dermatologic arena, a definite association has been proven only for HHV-6 and exanthema subitum (roseola infantum), whereas the role of HHV-7 in the pathogenesis of pityriasis rosea remains a matter of debate.

Emerging viral infections

The past decade has witnessed the emergence of several significant viral pathogens and the further evolution of additional viral pathogens. Transmitted by a variety of differing routes, these organisms have presented substantial intellectual challenges to medicine of the 20th and 21st centuries. As perhaps the benchmark pathogen of the past decade, HIV has provided medicine and society with a most formidable opponent, and one that has yet to be fully conquered. Nonetheless, a variety of additional viral pathogens have also perplexed medicine over the past 10-15 years.