ICTV Virus Taxonomy Profile: 2021.

Members of the family have enveloped, spherical virions with characteristic complex structures consisting of symmetrical and non-symmetrical components. The linear, double-stranded DNA genomes of 125-241 kbp contain 70-170 genes, of which 43 have been inherited from an ancestral herpesvirus. In general, herpesviruses have coevolved with and are highly adapted to their hosts, which comprise many mammalian, avian and reptilian species.

Human Herpesviruses 6A and 6B in Brain Diseases: Association versus Causation.

Human herpesvirus 6A (HHV-6A) and human herpesvirus 6B (HHV-6B), collectively termed HHV-6A/B, are neurotropic viruses that permanently infect most humans from an early age. Although most people infected with these viruses appear to suffer no ill effects, the viruses are a well-established cause of encephalitis in immunocompromised patients. In this review, we summarize the evidence that the viruses may also be one trigger for febrile seizures (including febrile status epilepticus) in immunocompetent infants and children, mesial temporal lobe epilepsy, multiple sclerosis (MS), and, possibly, Alzheimer's disease.

Clinical Diagnostic Testing for Human Cytomegalovirus Infections.

Human cytomegalovirus (HCMV) infections are among the most common complications arising in transplant patients, elevating the risk of various complications including loss of graft and death. HCMV infections are also responsible for more congenital infections worldwide than any other agent. Congenital HCMV (cCMV) infections are the leading nongenetic cause of sensorineural hearing loss and a source of significant neurological disabilities in children.

AMP-Activated Protein Kinase Restricts Zika Virus Replication in Endothelial Cells by Potentiating Innate Antiviral Responses and Inhibiting Glycolysis.

Viruses are known to perturb host cellular metabolism to enable their replication and spread. However, little is known about the interactions between Zika virus (ZIKV) infection and host metabolism. Using primary human retinal vascular endothelial cells and an established human endothelial cell line, we investigated the role of AMP-activated protein kinase (AMPK), a master regulator of energy metabolism, in response to ZIKV challenge.

Betaherpesvirus assembly and egress: Recent advances illuminate the path.

The human betaherpesviruses, human cytomegalovirus (HCMV; species Human betaherpesvirus 5) and human herpesviruses 6A, 6B, and 7 (HHV-6A, -6B, and -7; species Human betaherpesviruses 6A, 6B, and 7) are highly prevalent and can cause severe disease in immune-compromised and immune-naive populations in well- and under-developed communities. Herpesvirus virion assembly is an intricate process that requires viral orchestration of host systems. In this review, we describe recent advances in some of the many cellular events relevant to assembly and egress of betaherpesvirus virions.

Classification of human Herpesviridae proteins using Domain-architecture Aware Inference of Orthologs (DAIO).

We developed a computational approach called Domain-architecture Aware Inference of Orthologs (DAIO) for the analysis of protein orthology by combining phylogenetic and protein domain-architecture information. Using DAIO, we performed a systematic study of the proteomes of all human Herpesviridae species to define Strict Ortholog Groups (SOGs). In addition to assessing the taxonomic distribution for each protein based on sequence similarity, we performed a protein domain-architecture analysis for every protein family and computationally inferred gene duplication events.

Infection-Induced Changes Within the Endocytic Recycling Compartment Suggest a Roadmap of Human Cytomegalovirus Egress.

Human cytomegalovirus (HCMV) is an important pathogen in developing fetuses, neonates, and individuals with compromised immune systems. Gaps in our understanding of the mechanisms required for virion assembly stand in the way of development of antivirals targeting late stages of viral replication. During infection, HCMV causes a dramatic reorganization of the host endosecretory system, leading to the formation of the cytoplasmic virion assembly complex (cVAC), the site of virion assembly.

Betaherpesvirus Virion Assembly and Egress.

Virions are the vehicle for cell-to-cell and host-to-host transmission of viruses. Virions need to be assembled reliably and efficiently, be released from infected cells, survive in the extracellular environment during transmission, recognize and then trigger entry of appropriate target cells, and disassemble in an orderly manner during initiation of a new infection. The betaherpesvirus subfamily includes four human herpesviruses (human cytomegalovirus and human herpesviruses 6A, 6B, and 7), as well as viruses that are the basis of important animal models of infection and immunity.

Generation of a novel human cytomegalovirus bacterial artificial chromosome tailored for transduction of exogenous sequences.

The study of herpesviruses, including human cytomegalovirus (HCMV), is complicated by viral genome complexity and inefficient methods for genetic manipulation in tissue culture. Reverse genetics of herpesviruses has been facilitated by propagating their genomes in E. coli as bacterial artificial chromosomes (BACs), which enables complex and precise genetic manipulation using bacterial recombinational systems.

Protein-Protein Interactions Suggest Novel Activities of Human Cytomegalovirus Tegument Protein pUL103.

Unlabelled: Human cytomegalovirus (HCMV) is an enveloped double-stranded DNA virus that causes severe disease in newborns and immunocompromised patients. During infection, the host cell endosecretory system is remodeled to form the cytoplasmic virion assembly complex (cVAC). We and others previously identified the conserved, multifunctional HCMV virion tegument protein pUL103 as important for cVAC biogenesis and efficient secondary envelopment.

Summary of the 9th international conference on human herpesviruses 6 and 7 (HHV-6A, HHV-6B, and HHV-7).

The 9th International Conference on Human herpesviruses 6 and 7 (HHV-6A, HHV-6B, and HHV-7) was held at Harvard Medical School in Boston, Massachusetts from November 9 to 11, 2015. Important new information was presented regarding: the biology of these viruses, particularly HHV-6A and HHV-6B; the biology and epidemiology of inherited chromosomally integrated HHV-6A/B; improved diagnostic tests; animal models for studying HHV-6 and HHV-7, and animal viruses with similarities to HHV-6 and HHV-7; established and possible disease associations; and new approaches to treatment. Here, we summarize work of particular interest.

Absence of human herpesvirus 6B detection in association with illness in children undergoing cancer chemotherapy.

The lymphotropic herpesviruses, cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human herpesvirus 6B (HHV-6B) can reactivate and cause disease in organ transplant recipients; the contributions of HHV-6A and HHV-7 to disease are less certain. Less is known about their pathogenic roles in children undergoing treatment for malignancies. Children with newly diagnosed cancer were followed for 24 months.

Roseoloviruses: unmet needs and research priorities: perspective.

The human roseoloviruses, human herpesviruses 6A (HHV-6A), HHV-6B, and HHV-7, are highly prevalent viruses that typically cause fever/rash illnesses such as roseola during early life primary infections. They also cause significant neurologic disease and complications following stem cell and solid organ transplantation, and have suggestive but less certain etiologic associations with other neurologic diseases and immunologic disorders. The US National Institute of Allergy and Infectious Diseases recently sponsored a workshop (Roseoloviruses: Clinical Impact, Interventions, and Research Needs) to discuss disease associations, novel biology, and the many unmet research needs related to Roseoloviruses.

Roseolovirus molecular biology: recent advances.

Human herpesviruses 6A, 6B, and 7 (HHV-6A, HHV-6B, and HHV-7) are classified within the roseolovirus genus of the betaherpesvirus subfamily. Most humans likely harbor at least two of these large DNA viruses, and 1% of humans harbor germline chromosomally integrated (ci) HHV-6A or HHV-6B genomes. Differences at the genetic level manifest as distinct biologic properties during infection and disease.

Trunkloads of viruses.

Elephant populations are under intense pressure internationally from habitat destruction and poaching for ivory and meat. They also face pressure from infectious agents, including elephant endotheliotropic herpesvirus 1 (EEHV1), which kills ~20% of Asian elephants (Elephas maximus) born in zoos and causes disease in the wild. EEHV1 is one of at least six distinct EEHV in a phylogenetic lineage that appears to represent an ancient but newly recognized subfamily (the Deltaherpesvirinae) in the family Herpesviridae.

Basics of virology.

Viruses are important pathogens of the nervous system. Here we describe the basic properties of viruses and the principles of virus classification, evolution, structure, and replication, with a focus on neurotropic viruses that are important neuropathogens of humans. These properties then provide the background for introductions to pathogenesis of viral diseases of the nervous system, host immune responses to virus infection, and the diagnosis and treatment of virus infections of the nervous system.

Identification of human cytomegalovirus genes important for biogenesis of the cytoplasmic virion assembly complex.

Unlabelled: Human cytomegalovirus (HCMV) has many effects on cells, including remodeling the cytoplasm to form the cytoplasmic virion assembly complex (cVAC), the site of final virion assembly. Viral tegument, envelope, and some nonstructural proteins localize to the cVAC, and cytoskeletal filaments radiate from a microtubule organizing center in the cVAC. The endoplasmic reticulum (ER)-to-Golgi intermediate compartment, Golgi apparatus, and trans-Golgi network form a ring that outlines the cVAC.

Deletion of the human cytomegalovirus US17 gene increases the ratio of genomes per infectious unit and alters regulation of immune and endoplasmic reticulum stress response genes at early and late times after infection.

Human cytomegalovirus (HCMV) employs numerous strategies to combat, subvert, or co-opt host immunity. One evolutionary strategy for this involves capture of a host gene and then its successive duplication and divergence, forming a family of genes, many of which have immunomodulatory activities. The HCMV US12 family consists of 10 tandemly arranged sequence-related genes in the unique short (US) region of the HCMV genome (US12 to US21).

Classification of HHV-6A and HHV-6B as distinct viruses.

Shortly after the discovery of human herpesvirus 6 (HHV-6), two distinct variants, HHV-6A and HHV-6B, were identified. In 2012, the International Committee on Taxonomy of Viruses (ICTV) classified HHV-6A and HHV-6B as separate viruses. This review outlines several of the documented epidemiological, biological, and immunological distinctions between HHV-6A and HHV-6B, which support the ICTV classification.