Cell Intrinsic Determinants of Alpha Herpesvirus Latency and Pathogenesis in the Nervous System

Alpha herpesvirus infections (α-HVs) are widespread, affecting more than 70% of the adult human population. Typically, the infections start in the mucosal epithelia, from which the viral particles invade the axons of the peripheral nervous system. In the nuclei of the peripheral ganglia, α-HVs establish a lifelong latency and eventually undergo multiple reactivation cycles. Upon reactivation, viral progeny can move into the nerves, back out toward the periphery where they entered the organism, or they can move toward the central nervous system (CNS). This latency-reactivation cycle is remarkably well controlled by the intricate actions of the intrinsic and innate immune responses of the host, and finely counteracted by the viral proteins in an effort to co-exist in the population. If this yin-yang- or Nash-equilibrium-like balance state is broken due to immune suppression or genetic mutations in the host response factors particularly in the CNS, or the presence of other pathogenic stimuli, α-HV reactivations might lead to life-threatening pathologies. In this review, we will summarize the molecular virus-host interactions starting from mucosal epithelia infections leading to the establishment of latency in the PNS and to possible CNS invasion by α-HVs, highlighting the pathologies associated with uncontrolled virus replication in the NS.

Detection of a Novel Alphaherpesvirus and Avihepadnavirus in a Plantar Papilloma from a Rainbow Lorikeet (Trichoglosis moluccanus)

Cutaneous plantar papillomas are a relatively common lesion of wild psittacine birds in Australia. Next-generation sequencing technology was used to investigate the potential aetiologic agent(s) for a plantar cutaneous papilloma in a wild rainbow lorikeet (Trichoglosis moluccanus). In the DNA from this lesion, two novel viral sequences were detected. The first was the partial sequence of a herpesvirus with the proposed name, psittacid alphaherpesvirus 6, from the Mardivirus genus of the family alphaherpesviruses. This represents the first mardivirus to be detected in a psittacine bird, the first mardivirus to be detected in a wild bird in Australia, and the second mardivirus to be found in a biopsy of an avian cutaneous papilloma. The second virus sequence was a complete sequence of a hepadnavirus, proposed as parrot hepatitis B genotype H (PHBV-H). PHBV-H is the first hepadnavirus to be detected in a wild psittacine bird in Australia. Whether other similar viruses are circulating in wild birds in Australia and whether either of these viruses play a role in the development of the plantar papilloma will require testing of biopsies from similar lesions and normal skin from other wild psittacine birds.

The role of nuclear pores and importins for herpes simplex virus infection

Microtubule transport and nuclear import are functionally connected, and the nuclear pore complex (NPC) can interact with microtubule motors. For several alphaherpesvirus proteins, nuclear localization signals (NLSs) and their interactions with specific importin-α proteins have been characterized. Here, we review recent insights on the roles of microtubule motors, capsid-associated NLSs, and importin-α proteins for capsid transport, capsid docking to NPCs, and genome release into the nucleoplasm, as well as the role of importins for nuclear viral transcription, replication, capsid assembly, genome packaging, and nuclear capsid egress. Moreover, importin-α proteins exert antiviral effects by promoting the nuclear import of transcription factors inducing the expression of interferons (IFN), cytokines, and IFN-stimulated genes, and the IFN-inducible MxB restricts capsid docking to NPCs.

A novel herpesvirus from a wild-caught Madagascar spider tortoise shows evidence of host-viral coevolution with a duplication event in Durocryptodira

Herpesviruses can be significant reptile pathogens. Herpesviral infection in a wild-caught, male spider tortoise (Pyxis arachnoides) under human care was detected during a routine wellness examination prior to transition between zoologic organizations. The tortoise had no clinical signs of illness. Oral swabs obtained during a physical examination as part of pre-shipment risk mitigation for infectious disease were submitted for consensus herpesvirus PCR assay and sequencing. Based on comparative sequence analysis, the novel herpesvirus identified is a member of the subfamily Alphaherpesvirinae. Studies of herpesviral phylogeny in chelonian species support branching patterns of turtle herpesviruses that closely mirror those of their hosts. The symmetry of these patterns is suggestive of close codivergence of turtle herpesviruses with their host species. The distribution of these viruses in both tortoises and emydids suggests a phylogenetic duplication event in the herpesviruses after host divergence of the Pleurodira and basal to the divergence of Americhelydia. Herpesviral infections have been documented to cause higher morbidity when introduced to aberrant host species, and significant consideration must be given to the presence of herpesviruses in the management of tortoise collections, particularly collections that include various species of testudines.

Endogenous and viral microRNAs in nasal secretions of water buffaloes (Bubalus bubalis) after Bubaline alphaherpesvirus 1 (BuHV-1) challenge infection

Bubaline alphaherpesvirus 1 (BuHV-1) is a pathogen of water buffaloes responsible for economic loss worldwide. MicroRNAs (miRNAs) regulate gene expression produced by alphaherpesviruses and hosts. This study aimed at (a) unravelling the ability of BuHV-1 to produce miRNAs, including hv1-miR-B6, hv1-miR-B8, hv1-miR-B9; (b) measuring the host immune-related miRNAs associated to herpesvirus infection, including miR-210-3p, miR-490-3p, miR-17-5p, miR-148a-3p, miR-338-3p, miR-370-3p, by RT-qPCR; (c) identifying candidate markers of infection by receiver-operating characteristic (ROC) curves; (d) exploiting the biological functions by pathway enrichment analyses. Five water buffaloes BuHV-1 and Bovine alphaherpesvirus 1 (BoHV-1) free were immunized against Infectious Bovine Rhinotracheitis (IBR). Five additional water buffaloes served as negative controls. All animals were challenged with a virulent wild-type (wt) BuHV-1 via the intranasal route 120 days after the first vaccination. Nasal swabs were obtained at days (d) 0, 2, 4, 7, 10, 15, 30, and 63 post-challenge (pc). The animals of both groups shed wt BuHV-1 up to d7 pc. Results demonstrated that (a) miRNAs produced by the host and BuHV-1 could be efficiently quantified in the nasal secretion up to d63 and d15 pc, respectively; b) the levels of host and BuHV-1 miRNAs are different between vaccinated and control buffaloes; c) miR-370-3p discriminated vaccinated and control animals; d) host immune-related miRNAs may modulate genes involved in the cell adhesion pathway of the neuronal and immune system. Overall, the present study provides evidence that miRNAs can be detected in nasal secretions of water buffaloes and that their expression is modulated by BuHV-1.

Neutralizing antibodies to bovine and bubaline alphaherpesviruses in water buffaloes (Bubalus bubalis)

Water buffaloes (Bubalus bubalis) have been introduced in many regions of the world as a source of animal protein. In many instances, bubaline cattle are reared close to or mixed with bovine or zebuine cattle. However, little is known about infectious diseases of bubaline and the interactions that may arise involving the microbiota of those species. Alphaherpesviruses of ruminants (bovine alphaherpesviruses types 1 and 5, BoHV-1, BoHV-5; bubaline alphaherpesvirus 1, BuHV-1) are highly cross-reactive in serological assays performed with bovine or zebuine sera. However, the profile of reactivity of bubaline cattle sera to alphaherpesviruses remains unknown. As such, it is not known which virus strain (or strains) would be most appropriate to be used as the challenge virus in the laboratory in search for alphaherpesvirus-neutralizing antibodies. In this study, the profile of neutralizing antibodies to alphaherpesviruses in bubaline sera was determined against different types/subtypes of bovine and bubaline alphaherpesviruses. Sera (n=339) were screened in a 24-h serum neutralization test (SN) against 100 TCID50 of each of the challenge viruses. From those, 159 (46.9 %) neutralized at least one of the viruses assayed; 131 (38.6%) sera neutralized the three viral strains used for screening. The viral strain that was neutralized by the largest number of sera was BoHV-5b A663 (149/159; 93.7%). A few sera neutralized only one of the challenge viruses: four sera neutralized BoHV-1 LA only; another neutralized BoHV-5 A663 only and four others neutralized BuHV-1 b6 only. SN testing with two additional strains gave rise to similar results, where maximum sensitivity (defined here as the largest number of sera that neutralized the challenge viruses) was obtained by adding positive results attained with three of the challenge strains. Differences in neutralizing antibody titers were not significant to allow inferences on which would be the most likely virus that induced the antibody responses detected here.

UHRF1 Deficiency Inhibits Alphaherpesvirus through Inducing RIG-I-IRF3-Mediated Interferon Production

Type I interferon (IFN-I) response plays a prominent role in innate immunity, which is frequently modulated during viral infection. Here, we report DNA methylation regulator UHRF1 as a potent negative regulator of IFN-I induction during alphaherpesvirus infection, whereas the viruses in turn regulates the transcriptional expression of UHRF1. Knockdown of UHRF1 in cells significantly increases interferon-β (IFN-β)-mediated gene transcription and viral inhibition against herpes simplex virus 1 (HSV1) and pseudorabies virus (PRV). Mechanistically, UHRF1 deficiency promotes IFN-I production by triggering dsRNA-sensing receptor RIG-I and activating IRF3 phosphorylation. Knockdown of UHRF1 in cells upregulates the accumulation of double-stranded RNA (dsRNA), including host endogenous retroviral sequence (ERV) transcripts, while the treatment of RNase III, known to specifically digest dsRNA, prevents IFN-β induction by siUHRF1. Furthermore, the double-knockdown assay of UHRF1 and DNA methyltransferase DNMT1 suggests that siUHRF1-mediated DNA demethylation may play an important role in dsRNA accumulation and subsequently IFN induction. These findings establish the essential role of UHRF1 in IFN-I-induced antiviral immunity and reveal UHRF1 as a potential antivrial target. IMPORTANCE Alphaherpesviruses can establish lifelong infections and cause many diseases in humans and animals, which rely partly on their interaction with IFN-mediated innate immune response. Using alphaherpesviruses PRV and HSV-1 as models, we identified an essential role of DNA methylation regulator UHRF1 in IFN-mediated immunity against virus replication, which unravels a novel mechanism employed by epigenetic factor to control IFN-mediated antiviral immune response and highlight UHRF1, which might be a potential target for antiviral drug development.

Recombinant Pseudorabies Virus Usage in Vaccine Development against Swine Infectious Disease

Pseudorabies virus (PRV) is the pathogen of pseudorabies (PR), which belongs to the alpha herpesvirus subfamily with a double stranded DNA genome encoding approximately 70 proteins. PRV has many non-essential regions for replication, has a strong capacity to accommodate foreign genes, and more areas for genetic modification. PRV is an ideal vaccine vector, and multivalent live virus-vectored vaccines can be developed using the gene-deleted PRV. The immune system continues to be stimulated by the gene-deleted PRVs and maintain a long immunity lasting more than 4 months. Here, we provide a brief overview of the biology of PRV, recombinant PRV construction methodology, the technology platform for efficiently constructing recombinant PRV, and the applications of recombinant PRV in vaccine development. This review summarizes the latest information on PRV usage in vaccine development against swine infectious diseases, and it offers novel perspectives for advancing preventive medicine through vaccinology.

The Enduring Legacy of Randall Cohrs: A Meeting of the Minds in the Rocky Mountains

Randall Cohrs established the Colorado Alphaherpesvirus Latency Society (CALS) in 2011 [...]

Genetic Analysis of Chelonid Herpesvirus 5 in Marine Turtles from Baja California Peninsula

The Chelonid herpesvirus 5 (ChHV5) is the primary etiological agent associated with fibropapillomatosis (FP), a neoplastic disease in marine turtles. In this study, we report for the first time ChHV5 in marine turtles and a leech from Baja California Peninsula. Eighty-seven black, olive or loggerhead turtle species, one FP tumor and five leeches were analyzed. The tumor sample from an olive, a skin sample from a black and a leech resulted positive of ChHV5 for conventional PCR. Two viral variants were identified and grouped within the Eastern Pacific phylogenetic group, suggesting a possible flow of the virus in this region.

Antiviral agents against equid alphaherpesviruses: Current status and perspectives

Equid herpesvirus infections cause respiratory, neurological and reproductive syndromes. Despite preventive and control measures and the availability of vaccines and immunostimulants, herpesvirus infections still constitute a major threat to equine health and for the equine industry worldwide. Antiviral drugs, particularly nucleoside analogues and foscarnet, are successfully used for the treatment of human alphaherpesvirus infections. In equine medicine, the use of antiviral medications in alphaherpesvirus infections would decrease the excretion of virus and diminish the risk of contagion and the convalescent time in affected horses, and would also improve the clinical outcome of equine herpesvirus myeloencephalopathy. The combined use of antiviral compounds, along with vaccines, immune modulators, and effective preventive and control measures, might be beneficial in diminishing the negative impact of alphaherpesvirus infections in horses. The purpose of this review is to analyse the available information regarding the use of antiviral agents against alphaherpesviruses, with particular emphasis on equine alphaherpesvirus infections.

Pneumomediastinum and subcutaneous emphysema in a cat associated with necrotizing bronchopneumonia caused by feline herpesvirus-1

This report describes a 1-year-old cat with acute dyspnea. Thoracic radiography revealed a pneumomediastinum and severe subcutaneous emphysema. Lower airway surgical exploration was unable to determine the cause. At postmortem examination, acute necrotizing bronchopneumonia and fibrinonecrotic tracheitis due to feline herpesvirus-1 were diagnosed.

Severe thrombocytopenia in aged rhesus macaques (Macaca mulatta) infected with simian varicella virus

Simian varicella virus was diagnosed in 2 geriatric rhesus macaques (Macaca mulatta). The macaques presented with typical skin lesions as well as severe thrombocytopenia as a result of infection. Idiopathic thrombocytopenic purpura is a known complication of varicella zoster virus infection in humans; however, this condition has not been reported previously as a complication of SVV infection. This case report discusses the clinical presentation, pathology, and thrombocytopenia of the affected macaques.

Factors limiting the health of semi-scavenging ducks in Bangladesh

Duck rearing is well suited to coastal and lowland areas in Bangladesh. It is an important component of sustainable livelihood strategies for poor rural communities as an additional source of household income. An epidemiological study was conducted during January 2005-June 2006 on 379 households in Chatkhil of the Noakhali District, Bangladesh which were using the recently devised "Bangladesh duck model". The overall objective of the study was to identify factors that significantly contributed to mortality and constrained productivity and to generate sufficient knowledge to enable establishment of a disease surveillance system for household ducks. The overall mortality was 15.0% in Chatkhil, with predation causing a significantly higher mortality compared with diseases (p < 0.001). Common diseases were duck plague and duck cholera. Morbid ducks frequently displayed signs associated with diseases affecting the nervous and digestive systems. Haemorrhagic lesions in various organs and white multiple foci on the liver were frequently observed in dead ducks. Epidemiological analysis with a shared frailty model that accounted for clustering of data by farm was used to estimate the association between survival time and risk factors. The overall mortality rate due to disease was significantly lower in vaccinated than in non-vaccinated ducks in all zones except zone 2 (p < 0.001). Only vaccinated ducks survived in zone 1. In conclusion, duck mortality and untimely sale of ducks appeared to be important constraints for household duck production in Chatkhil. Vaccination against duck plague appears to be an effective preventive strategy in reducing the level of associated duck mortality. A successful network was established amongst farmers and the surveillance team through which dead ducks, with accompanying information, were readily obtained for analysis. Therefore, there is an opportunity for establishing a long-term disease surveillance programme for rural ducks in Chatkhil of the Noakhali District of Bangladesh.

New options in herpes management

Herpesviruses in the alpha group--HSV-1, HSV-2, and VZV (i.e., HSV-3)--are ubiquitous in American society. HSV-1 is associated primarily with herpes labialis, while HSV-2 is involved in about 70% of cases of genital herpes. Varicellazoster virus causes chickenpox in unvaccinated children and others, and latent virus produces shingles later in life. Since many patients with HSV-1 and HSV-2 infections are asymptomatic, testing is important in determining presence of the viruses. Several antiviral agents effective against HSV have been marketed. While the infection cannot be cured, the available medications are effective for reducing the duration of outbreaks, recurrences, and possibly viral transmission.

[Alpha-herpesvirus infection in the central nervous system]

Herpes simplex virus type 1 (HSV1) encephalitis is commonly observed, but HSV1 myelitis is rare. On the other hand, HSV2 is common etiologic agent for ascending necrotizing myelitis associated with diabetes mellitus, malignant tumors, AIDS and immunocompromised hosts. It is suggested that latent infection of the virus of root ganglia or primary infected virus is possibly followed by spread of infection to the central nervous system, particularly in immunocompromised patients. In this report, pathological findings and clinical symptoms of our recent encephalitis and myelitis cases infected with HSV2 and HSV1 are described.

[Study of alpha-herpesvirus: present state and future developments]

The herpesvirus is a ubiquitous infectious agent present in a variety of vertebrates including humans. The virus has a duplex DNA molecule of 120-240 kbp within an icosahedral capsid surrounded by an envelope. Latency is a central feature of herpesvirus biology. Studies of herpesviruses relate to 1) diagnosis, prevention, and the treatment of diseases associated with herpesvirus infections, 2) elucidation of biological mechanisms of mammalian cells using herpesviruses, 3) construction of vaccine and vector systems for gene therapy, and 4) establishment of putative associations of herpesviruses with host organisms during evolution (suggesting the host-linked evolution of herpesvirus).

[Alpha herpesvirus infections in AIDS patients]

Alpha-herpesvirus infections by herpes simplex virus and varicella-zoster virus among HIV-infected patients were summarized. These infections were occurred in a high frequency and shown to be extensive lesions, prolonged virus excretion from the lesions, generalized infection, and uncommon diseases as compared these of with immunocompetent patients. Acyclovir-resistant viruses appeared. These evidences supplied the profound understanding of the pathogenesis and new subjects in the field of herpesvirus infection. Recent introduction of HAART against HIV and the appropriate use of anti-herpesvirus drugs, however, reduced the development of severe infection, and provided successful treatment, respectively.

[Sexually transmitted diseases of alpha herpes virus in women]

Among two alpha herpes viruses, Herpes Simplex Virus(HSV) and Varicella Zoster virus(VZV), HSV infects genital sites and is frequently transmitted by sexual contact while VZV has quite different mode of transmission and rarely infects genital site except herpes zoster at the vulva. Genital herpes is the second and the third leading cause of STDs in women and men respectively. While 90% of male genital herpes was caused by HSV-2, 55% of female genital herpes was by HSV-2 and the remaining 45% by HSV-1. As for primary infection of female genital herpes, 60% was caused by HSV-1 and 40% by HSV-2. On the otherhand about 90% of recurrent infection was by HSV-2 suggesting that HSV-2 is closely related to latent infection of the female genital tract.

[Alpha-herpes virus infections--male genital herpes]

In Japan, male genital herpes is the third popular male STD, the most popular one being gonococcal infection and the second chlamydial infection. As specific clinical findings, superficial ulcer lesions with pain are formed in the genital area, especially in the prepuce. After HSV infection in genital mucocutaneous sites, viral particles are transported to the neurons. The state of subsequent HSV infection from external genitalia to the neurons is known as latent infection. 76% of our cases of the first episode of genital herpes infection were caused by HSV-2, and most of the recurrent episodes was caused by HSV-2. Oral acyclovir administration for five to ten days has shortened the treatment period, although about 20 days were required without any treatment. The remaining problems are, asymptomatic HSV shedding, severe infections in immunocompromised patients, transmission of HSV to sex partners and vertical infection to neonates.

[Ophthalmic area]

Although herpes simplex virus type 1 or herpes zoster virus is generally considered to cause ocular infection among alpha herpesviruses, herpes simplex virus type 2(HSV-2) retinitis has been recently reported. Acute retinal necrosis(ARN) syndrome is associated with herpesviruses, but the mechanisms remain unclear. The representative ocular infection by alpha herpesviruses is herpes simplex virus type 1(HSV-1) keratitis. The clinical types, ocular symptoms and therapy are reviewed in herpetic ocular infections(HSV-1 blephalitis, conjunctivitis, keratitis, retinitis). In addition, ocular infections caused by herpes zoster virus are reviewed.

[Clinical manifestations of the subfamily alpha-herpesvirinae in childhood]

Herpes simplex virus(HSV) and varicella-zoster virus(VZV) belonging to the subfamily of alpha-herpesvirinae have the capacity to establish latent infection in neural tissues and to reactivate from these sites. HSV infection is characterized by a vesicular eruption, fever, and other constitutional symptoms but frequently inapparent both in primary and recurrent infections. However, the infection produces a wide spectrum of illness ranging from the trivial fever blisters to the most severe fatal sporadic encephalitis and neonatal infection. In contrast, VZV develops varicella, a common contagious disease of childhood during primary infection and zoster by reactivation of latent virus acquired during varicella. In normal children, the systemic symptoms of both diseases are mild, whereas serious complications are often observed in children with deficiencies in cell-mediated immunity. Acyclovir has been the drug of choice for treatment of severe infection with HSV and VZV for approximately 2 decades. Now, two new agents, valacyclovir and famciclovir will supplant acyclovir for certain indications.

[Alphaherpesvininae--dermatology]

The subfamily alphaherpesuvirinae contains herpes simplex virus(HSV) and varicella-zoster virus(VZV) in the Dermatology. HSV infectious diseases are herpetic gingivostomatitis, herpes labialis, facial herpes simplex, Kaposi's varicelliform eruption, genital herpes, lumbosacral herpes simplex, and herpetic whitlow. The primary form of VZV infection is varicella, and the reactivation form is herpes zoster. These infectious diseases in the dermatological clinics usually occur in adult. In this paper we mention clinical manifestations and treatment.

[Transplantation associated alpha herpes virus infection]

Immunosuppression after organ or bone marrow transplantation changes its severity with the time lapse. After bone marrow transplantation, HSV infection occurs in early period and VZV infection, in intermediate period. Aciclovir prophylaxis is effective for preventing HSV in early period and also for elevating the compliance of drug intake. It delays onset of VZV infection on the other hand. VZV infection is usually very severe if it is occurred early, before 100 days after transplant. There was some case of VZV infection with severe abdominal pain without any skin involvement. The incidence of VZV infection in bone marrow recipients was 29%. Even in stable period it caused considerable mental problems in some patient.

[Alpha herpes virus and facial palsy]

Alpha herpes virus is the major causes of peripheral facial palsy such as Bell's palsy or Ramsay Hunt syndrome. Ramsay Hunt syndrome is caused by varicella zoster virus (VZV) infection, and can be diagnosed by facial nerve paralysis associated with herpetic eruption on the pinna, and complication of by vestibulo-cochlear dysfunction. On the other hand, Bell's palsy presents only facial palsy and its diagnosis is made by the exclusion of known conditions. The causes of Bell's palsy had been unknown for many years, however, recently it was revealed that herpes simplex type 1 was the major cause of Bell's palsy by PCR. Because early treatment with acyclovir and prednisone was proven to be effective, we should make efforts to diagnose these diseases as early as possible.

Clinical disease associated with simian agent 8 infection in the baboon

Simian agent 8 (SA8) is an alphaherpesvirus that was first reported as a spontaneous natural infection in a captive baboon colony in 1988. It was first isolated from an African vervet monkey in 1958 and was classified as a simian agent. Simian agent 8 was later isolated from a baboon rectal swab specimen in 1969 and from an oral lesion in a vervet monkey in 1972. Restriction endonuclease analysis was used to identify the virus as SA8. In a 1-year period, 70 baboons housed in two outside 6-acre breeding corrals developed lesions principally on the genitalia and oral cavity. The incidence was the same for males and females, with recurrence rate, severity of the lesions, and duration for the lesions to resolve being greater in the female baboons. Lesions involving the mouth, tongue, and lips were most commonly observed in the juvenile population. The lesions tended to start as small multiple papules or vesicles, which advanced to large pustular or ulcerative areas. Using an every-other-day treatment regimen consisting of Nolvasan cleaning and procaine penicillin G injections, it took an average of 14 to 21 days for the lesions to resolve totally. Thirty-seven percent of the baboons with herpetic lesions experienced another episode of SA8 infection, usually within 1 year of development of the primary lesion. Several complications have been documented to be associated with SA8 infections. Partial or total vaginal obstruction is most common, leading to impaired breeding performance and pyelonephritis. A vaginal corrective surgical procedure has been developed to allow these females to return to productive breeding status within the colony. Penile urethral obstruction, also causing pyelonephritis, was observed in the male baboons. A case of sciatic neuritis was reported in a baboon that presented with self mutilation of the foot; viral isolation revealed the etiologic agent to be SA8. Four female baboons with chronic SA8 infections went on to develop perineal neoplasms. This is an economically important disease entity in captive baboons because it causes severe morbidity, decreased reproductive performance, and ultimately death in 1% of the baboon colony each year. The baboon is a promising animal model in which to study genital herpes as it relates to disease in human beings.

New therapeutic approaches to the alphaherpesvirus infections

The character of diseases caused by alphaherpesviruses has changed over the last decade. The severity of disease and the frequency of acyclovir resistance has increased with the increase in the number of immunocompromised patients. Compounding the trend towards more virulent herpes disease is the current emphasis towards outpatient management of many diseases. Much of the current antiviral research focuses on providing drugs with (i) improved oral bioavailability and pharmacokinetics which permit less frequent oral or topical dosing for suppressive treatment of herpes simplex virus (HSV) infections, (ii) different mechanisms of action for synergic effects in treating resistant HSV infections in the immunocompromised host and (iii) improved efficacy. Future antiviral agents will probably target enzymes or viral factors essential for infection or will inhibit other steps in the viral infection cycle, such as viral entry, protein synthesis or capsid assembly. Medications that augment the immune response constitute another pathway for combating herpes viral infections. Many of the newer experimental agents target essential processes unique to herpesvirus replication and, therefore, potentially have high selectivity.

Cloning and sequence analysis of a Marek's disease virus origin binding protein (OBP) reveals strict conservation of structural motifs among OBPs of divergent alphaherpesviruses

Marek's disease virus (MDV) is a highly cell-associated avian herpesvirus. In its natural host, MDV induces Marek's disease (MD), a lethal condition characterized by malignant lymphoma of T cells. Although symptoms of MD may be prevented by vaccination, no practical pharmacological method of control has been widely accepted. Viral replication represents a point at which pharmacological control of herpesvirus infection may be most successful. However, this requires detailed knowledge of viral replication proteins. Studies in HSV-1 DNA replication implicate the UL9 protein as a key initiator of replication. For example, binding of UL9 to HSV-1 origins is a prerequisite for assembly of additional replication proteins. In this study, a protein, whose apparent molecular size is similar to that of HSV-1 UL9, was identified in extracts of MDV infected cells by western blot analysis with anti-HSV-1 UL9 antibody. A putative MDV UL9 gene was subsequently identified through sequencing of MDV genome fragments (BamHI G and C). Extended DNA sequence analysis revealed an open reading frame (ORF) which could encode a protein homologous to HSV-1 UL9. The MDV UL9 ORF encodes 841 amino acids, producing a sequence 49% identical to HSV-1 UL9 and 46% identical to VZV gene 51 product (VZV UL9). MDV UL9 shares numerous structural motifs with HSV-1 and VZV UL9 proteins, including six conserved N-terminal helicase motifs, an N-terminal leucine zipper motif, a C-terminal pseudo-leucine zipper sequence, and a putative helix-turn-helix structure.