Complete genome sequence of cercopithecine herpesvirus 2 (SA8) and comparison with other simplexviruses

Application of CRISPR/Cas9 for Rapid Genome Editing of Pseudorabies Virus and Bovine Herpesvirus-1

The CRISPR/Cas9 system is widely used to manipulate viral genomes. Although Alphaherpesvirinae genomes are large and complicated to edit, in recent years several Pseudorabies virus (PRV) mutants have been successfully generated using the CRISPR/Cas9 system. However, the application of CRISPR/Cas9 editing on another member of alpha herpesviruses, bovine herpesvirus-1 (BHV-1), is rarely reported. This paper reports a rapid and straightforward approach to manipulating herpesviruses genome using CRISPR/Cas9. The recombinant plasmids contained the left and right arm of the thymidine kinase (TK) gene of PRV or of the glycoprotein I (gI) and glycoprotein E (gE) of BHV-1. Upon the cleavage of the TK or gIgE gene by Cas9 protein, this was replaced by the enhanced green fluorescence protein (eGFP) by homologous recombination. With this approach, we generated recombinant TK-/eGFP+ PRV and gIgE-/eGFP+ BHV-1 mutants and then proceeded to characterize their biological activities in vitro and in vivo. In conclusion, we showed that alpha herpesvirus, including PRV and BHV-1, can be rapidly edited using the CRISPR/Cas9 approach paving the way to the development of animal herpesvirus vaccines.

Towards a comprehensive view of the herpes B virus

Herpes B virus is a biosafety level 4 pathogen and widespread in its natural host species, macaques. Although most infected monkeys show asymptomatic or mild symptoms, human infections with this virus can cause serious neurological symptoms or fatal encephalomyelitis with a high mortality rate. Herpes B virus can be latent in the sensory ganglia of monkeys and humans, often leading to missed diagnoses. Furthermore, the herpes B virus has extensive antigen crossover with HSV, SA8, and HVP-2, causing false-positive results frequently. Timely diagnosis, along with methods with sensitivity and specificity, are urgent for research on the herpes B virus. The lack of a clear understanding of the host invasion and life cycle of the herpes B virus has led to slow progress in the development of effective vaccines and drugs. This review discusses the research progress and problems of the epidemiology of herpes B virus, detection methods and therapy, hoping to inspire further investigation into important factors associated with transmission of herpes B virus in macaques and humans, and arouse the development of effective vaccines or drugs, to promote the establishment of specific pathogen-free (SPF) monkeys and protect humans to effectively avoid herpes B virus infection.

Primate Simplexviruses Differ in Tropism for Macaque Cells

Primate simplexviruses are closely related neurotropic herpesviruses, which are largely apathogenic in their respective host species. However, cross-species transmission of Macacine alphaherpesvirus 1 (McHV1, also termed herpes B virus) from rhesus macaques to humans can cause fatal encephalomyelitis. In contrast, closely related viruses, such as Cercopithecine alphaherpesvirus 2 (CeHV2, also termed simian agent 8) or Papiine alphaherpesvirus 2 (PaHV2, also termed herpesvirus papio 2), have not been linked to human disease and are believed to be largely apathogenic in humans. Here, we investigated whether McHV1, PaHV2 and CeHV2 differ in their capacity to infect human and non-human primate (NHP) cells. For comparison, we included the human simplexviruses HSV1 and HSV2 in our analyses. All five viruses replicated efficiently in cell lines of human and African green monkey origin, and McHV1 and PaHV2 also showed robust replication in rhesus macaque cell lines. In contrast, the replication of CeHV2 and particularly HSV1 and HSV2 in cell lines of rhesus macaque origin were reduced or inefficient. Similarly, McHV1, but not CeHV2, efficiently infected rhesus macaque brain organoids. These results point towards the previously unappreciated partial resistance of certain rhesus macaque cells to HSV1/HSV2/CeHV2 infection and reveal similarities between the cell tropism of McHV1 and PaHV2 that might be relevant for risk assessment.

A Recombinant System and Reporter Viruses for Papiine Alphaherpesvirus 2

Primate simplex viruses, including Herpes simplex viruses 1 and 2, form a group of closely related herpesviruses, which establish latent infections in neurons of their respective host species. While neuropathogenic infections in their natural hosts are rare, zoonotic transmission of Macacine alphaherpesvirus 1 (McHV1) from macaques to humans is associated with severe disease. Human infections with baboon-derived Papiine alphaherpesvirus 2 (PaHV2) have not been reported, although PaHV2 and McHV1 share several biological properties, including neuropathogenicity in mice. The reasons for potential differences in PaHV2 and McHV1 pathogenicity are presently not understood, and answering these questions will require mutagenic analysis. Here, we report the development of a recombinant system, which allows rescue of recombinant PaHV2. In addition, we used recombineering to generate viruses carrying reporter genes (Gaussia luciferase or enhanced green fluorescent protein), which replicate with similar efficiency as wild-type PaHV2. We demonstrate that these viruses can be used to analyze susceptibility of cells to infection and inhibition of infection by neutralizing antibodies and antiviral compounds. In summary, we created a recombinant system for PaHV2, which in the future will be invaluable for molecular analyses of neuropathogenicity of PaHV2.

[B virus]

B virus is a herpes virus that natutaly infects macaque monkeys. It is extremely neuropathogenic when infection occurs in humans. B virus infection has been reported only in laboratory workers and breeders of macaque monkeys in North America and the United Kingdom, and it is therefore recognized as a rare infectious disease. The first cases of B virus disease were reported in Japan in 2019 and in China in 2021, although no cases had been reported since 1997. Although B virus disease has not been reported for more than 20 years, the potential threat has always existed. The viral factors responsible for the strong neuropathogenicity of B virus to humans has not been identified. There are no reports of infection by contact with wild macaque monkeys, but the possibility can not been ruled out. In this paper, we describe its virological properties, findings from B virus disease from patient-reported cases, and the genotype of B virus.

Genomic nucleotide-based distance analysis for delimiting old world monkey derived herpes simplex virus species

BACKGROUND

Herpes simplex viruses form a genus within the alphaherpesvirus subfamily, with three identified viral species isolated from Old World monkeys (OWM); Macacine alphaherpesvirus 1 (McHV-1; herpes B), Cercopithecine alphaherpesvirus 2 (SA8), and Papiine alphaherpesvirus 2 (PaHV-2; herpes papio). Herpes B is endemic to macaques, while PaHV-2 and SA8 appear endemic to baboons. All three viruses are genetically and antigenically similar, with SA8 and PaHV-2 thought to be avirulent in humans, while herpes B is a biosafety level 4 pathogen. Recently, next-generation sequencing (NGS) has resulted in an increased number of published OWM herpes simplex genomes, allowing an encompassing phylogenetic analysis.

RESULTS

In this study, phylogenetic networks, in conjunction with a genome-based genetic distance cutoff method were used to examine 27 OWM monkey herpes simplex isolates. Genome-based genetic distances were calculated, resulting in distances between lion and pig-tailed simplex viruses themselves, and versus herpes B core strains that were higher than those between PaHV-2 and SA8 (approximately 14 and 10% respectively). The species distance cutoff was determined to be 8.94%, with the method recovering separate species status for PaHV-2 and SA8 and showed that lion and pig-tailed simplex viruses (vs core herpes B strains) were well over the distance species cutoff.

CONCLUSIONS

We propose designating lion and pig-tailed simplex viruses as separate, individual viral species, and that this may be the first identification of viral cryptic species.

A Fosmid-Based System for the Generation of Recombinant Cercopithecine Alphaherpesvirus 2 Encoding Reporter Genes

The transmission of Macacine alphaherpesvirus 1 (McHV-1) from macaques, the natural host, to humans causes encephalitis. In contrast, human infection with Cercopithecine alphaherpesvirus 2 (CeHV-2), a closely related alphaherpesvirus from African vervet monkeys and baboons, has not been reported and it is believed that CeHV-2 is apathogenic in humans. The reasons for the differential neurovirulence of McHV-1 and CeHV-2 have not been explored on a molecular level, in part due to the absence of systems for the production of recombinant viruses. Here, we report the generation of a fosmid-based system for rescue of recombinant CeHV-2. Moreover, we show that, in this system, recombineering can be used to equip CeHV-2 with reporter genes. The recombinant CeHV-2 viruses replicated with the same efficiency as uncloned, wt virus and allowed the identification of cell lines that are highly susceptible to CeHV-2 infection. Collectively, we report a system that allows rescue and genetic modification of CeHV-2 and likely other alphaherpesviruses. This system should aid future analysis of CeHV-2 biology.

Questioning the Extreme Neurovirulence of Monkey B Virus (Macacine alphaherpesvirus 1)

Monkey B virus (Macacine alphaherpesvirus 1; BV) occurs naturally in macaques of the genus Macaca, which includes rhesus and long-tailed (cynomolgus) monkeys that are widely used in biomedical research. BV is closely related to the human herpes simplex viruses (HSV), and BV infections in its natural macaque host are quite similar to HSV infections in humans. Zoonotic BV is extremely rare, having been diagnosed in only a handful of North American facilities with the last documented case occurring in 1998. However, BV is notorious for its neurovirulence since zoonotic infections are serious, usually involving the central nervous system, and are frequently fatal. Little is known about factors underlying the extreme neurovirulence of BV in humans. Here we review what is actually known about the molecular biology of BV and viral factors affecting its neurovirulence. Based on what is known about related herpesviruses, areas for future research that may elucidate mechanisms underlying the neurovirulence of this intriguing virus are also reviewed.

Ancient Recombination Events between Human Herpes Simplex Viruses

Herpes simplex viruses 1 and 2 (HSV-1 and HSV-2) are seen as close relatives but also unambiguously considered as evolutionary independent units. Here, we sequenced the genomes of 18 HSV-2 isolates characterized by divergent UL30 gene sequences to further elucidate the evolutionary history of this virus. Surprisingly, genome-wide recombination analyses showed that all HSV-2 genomes sequenced to date contain HSV-1 fragments. Using phylogenomic analyses, we could also show that two main HSV-2 lineages exist. One lineage is mostly restricted to subSaharan Africa whereas the other has reached a global distribution. Interestingly, only the worldwide lineage is characterized by ancient recombination events with HSV-1. Our findings highlight the complexity of HSV-2 evolution, a virus of putative zoonotic origin which later recombined with its human-adapted relative. They also suggest that coinfections with HSV-1 and 2 may have genomic and potentially functional consequences and should therefore be monitored more closely.

Sequence of the ateline alphaherpesvirus 1 (HVA1) genome

Here, we report the genome sequence of a spider monkey alphaherpesvirus (ateline alphaherpesvirus 1, HVA1) and compare it with that of other primate alphaherpesviruses. The HVA1 genome is 147,346 bp long and contains 67 predicted ORFs. The genetic layout of the HVA1 genome is similar to that of the squirrel monkey alphaherpesvirus (saimirine alphaherpesvirus 1, HVS1) in that it lacks inverted repeat regions flanking the unique long region and homologues of the UL43, UL49.5, US8.5 and US10-12 genes. Unlike HVS1, HVA1 also lacks a homologue of the RL1 (γ34.5) gene and a replication origin near the end of the genome. Consistent with previous phylogenetic analyses, all predicted proteins of HVA1 are most closely related to those of HVS1.

Understanding Primate Herpesviruses

Viruses related to the herpes simplex viruses of humans are present in all nonhuman primate (NHP) species tested and cross species transmission has been documented. The herpesvirus present in macaques, Herpes B virus (BV) rarely causes disease in its natural macaque host. However, when transmitted to a nonnative host, BV has occasionally caused severe and even fatal disease if not treated immediately. Here we present a comprehensive review of the taxonomy, molecular biology, physiology, epidemiology, diagnosis and treatment of BV. We also summarizes what is known about related herpesviruses of other NHP species and the zoonotic potential of these viruses.

Genome sequence of a pathogenic isolate of monkey B virus (species Macacine herpesvirus 1)

The only genome sequence for monkey B virus (BV; species Macacine herpesvirus 1) is that of an attenuated vaccine strain originally isolated from a rhesus monkey (BVrh). Here we report the genome sequence of a virulent BV strain isolated from a cynomolgus macaque (BVcy). The overall genome organization is the same, although sequence differences exist. The greatest sequence divergence is located in non-coding areas of the long and short repeat regions. Like BVrh, BVcy has duplicated Ori elements and lacks an ORF corresponding to the γ34.5 gene of herpes simplex virus. Nine of ten miRNAs and the majority of ORFs are conserved between BVrh and BVcy. The most divergent genes are several membrane-associated proteins and those encoding immediate early proteins.

Analysis of the genome of leporid herpesvirus 4

The genome of a herpesvirus highly pathogenic to rabbits, leporid herpesvirus 4 (LHV-4), was analyzed using high-throughput DNA sequencing technology and primer walking. The assembled DNA sequences were further verified by restriction endonuclease digestion and Southern blot analyses. The total length of the LHV-4 genome was determined to be about 124 kb. Genes encoded in the LHV-4 genome are most closely related to herpesvirus of the Simplexvirus genus, including human herpesviruses (HHV-1 and HHV-2), monkey herpesviruses including cercopithicine (CeHV-2 and CeHV-16), macacine (McHV-1), bovine herpesvirus 2 (BHV-2), and a lineage of wallaby (macropodid) herpesviruses (MaHV-1 and -2). Similar to other simplexvirus genomes, LHV-4 has a high overall G+C content of 65-70% in the unique regions and 75-77% in the inverted repeat regions. Orthologs of ICP34.5 and US5 were not identified in the LHV-4 genome. This study shows that LHV-4 has the smallest simplexvirus genome characterized to date.

Herpes B virus utilizes human nectin-1 but not HVEM or PILRα for cell-cell fusion and virus entry

To investigate the requirements of herpesvirus entry and fusion, the four homologous glycoproteins necessary for herpes simplex virus (HSV) fusion were cloned from herpes B virus (BV) (or macacine herpesvirus 1, previously known as cercopithecine herpesvirus 1) and cercopithecine herpesvirus 2 (CeHV-2), both related simian simplexviruses belonging to the alphaherpesvirus subfamily. Western blots and cell-based enzyme-linked immunosorbent assay (ELISA) showed that glycoproteins gB, gD, and gH/gL were expressed in whole-cell lysates and on the cell surface. Cell-cell fusion assays indicated that nectin-1, an HSV-1 gD receptor, mediated fusion of cells expressing glycoproteins from both BV and CeHV-2. However, herpesvirus entry mediator (HVEM), another HSV-1 gD receptor, did not facilitate BV- and CeHV-2-induced cell-cell fusion. Paired immunoglobulin-like type 2 receptor alpha (PILRα), an HSV-1 gB fusion receptor, did not mediate fusion of cells expressing glycoproteins from either simian virus. Productive infection with BV was possible only with nectin-1-expressing cells, indicating that nectin-1 mediated entry while HVEM and PILRα did not function as entry receptors. These results indicate that these alphaherpesviruses have differing preferences for entry receptors. The usage of the HSV-1 gD receptor nectin-1 may explain interspecies transfer of the viruses, and altered receptor usage may result in altered virulence, tropism, or pathogenesis in the new host. A heterotypic cell fusion assay resulting in productive fusion may provide insight into interactions that occur to trigger fusion. These findings may be of therapeutic significance for control of deadly BV infections.

The evolution of infectious agents in relation to sex in animals and humans: brief discussions of some individual organisms

The following series of concise summaries addresses the evolution of infectious agents in relation to sex in animals and humans from the perspective of three specific questions: (1) what have we learned about the likely origin and phylogeny, up to the establishment of the infectious agent in the genital econiche, including the relative frequency of its sexual transmission; (2) what further research is needed to provide additional knowledge on some of these evolutionary aspects; and (3) what evolutionary considerations might aid in providing novel approaches to the more practical clinical and public health issues facing us currently and in the future?

RNA binding properties of the US11 protein from four primate simplexviruses

Background

The protein encoded by the Us11 gene of herpes simplex viruses is a dsRNA binding protein which inhibits protein kinase R activity, thereby preventing the interferon-induced shut down of protein synthesis following viral infection. Us11 protein is not essential for infectivity in vitro and in mice in herpes simplex virus type 1 (HSV1), however this virus has a second, and apparently more important, inhibitor of PKR activity, the γ₁34.5 protein. Recently sequenced simian simplexviruses SA8, HVP2 and B virus do not have an ORF corresponding to the γ₁34.5 protein, yet they have similar, or greater, infectivity as HSV1 and HSV2.

Methods

We have expressed the US11 proteins of the simplexviruses HSV1, HSV2, HVP2 and B virus and measured their abilities to bind dsRNA, in order to investigate possible differences that could complement the absence of the γ₁34.5 protein. We employed a filter binding technique that allows binding of the Us11 protein under condition of excess dsRNA substrate and therefore a measurement of the true Kd value of Us11-dsRNA binding.

Results and Conclusions

The results show a Kd of binding in the range of 0.89 nM to 1.82 nM, with no significant difference among the four Us11 proteins.

Structure and sequence of the saimiriine herpesvirus 1 genome

We report here the complete genome sequence of the squirrel monkey α-herpesvirus saimiriine herpesvirus 1 (HVS1). Unlike the simplexviruses of other primate species, only the unique short region of the HVS1 genome is bounded by inverted repeats. While all Old World simian simplexviruses characterized to date lack the herpes simplex virus RL1 (γ34.5) gene, HVS1 has an RL1 gene. HVS1 lacks several genes that are present in other primate simplexviruses (US8.5, US10-12, UL43/43.5 and UL49A). Although the overall genome structure appears more like that of varicelloviruses, the encoded HVS1 proteins are most closely related to homologous proteins of the primate simplexviruses. Phylogenetic analyses confirm that HVS1 is a simplexvirus. Limited comparison of two HVS1 strains revealed a very low degree of sequence variation more typical of varicelloviruses. HVS1 is thus unique among the primate α-herpesviruses in that its genome has properties of both simplexviruses and varicelloviruses.

Herpesvirus systematics

This paper is about the taxonomy and genomics of herpesviruses. Each theme is presented as a digest of current information flanked by commentaries on past activities and future directions. The International Committee on Taxonomy of Viruses recently instituted a major update of herpesvirus classification. The former family Herpesviridae was elevated to a new order, the Herpesvirales, which now accommodates 3 families, 3 subfamilies, 17 genera and 90 species. Future developments will include revisiting the herpesvirus species definition and the criteria used for taxonomic assignment, particularly in regard to the possibilities of classifying the large number of herpesviruses detected only as DNA sequences by polymerase chain reaction. Nucleotide sequence accessions in primary databases, such as GenBank, consist of the sequences plus annotations of the genetic features. The quality of these accessions is important because they provide a knowledge base that is used widely by the research community. However, updating the accessions to take account of improved knowledge is essentially reserved to the original depositors, and this activity is rarely undertaken. Thus, the primary databases are likely to become antiquated. In contrast, secondary databases are open to curation by experts other than the original depositors, thus increasing the likelihood that they will remain up to date. One of the most promising secondary databases is RefSeq, which aims to furnish the best available annotations for complete genome sequences. Progress in regard to improving the RefSeq herpesvirus accessions is discussed, and insights into particular aspects of herpesvirus genomics arising from this work are reported.

Herpes simplex virus type 2 tegument protein UL56 relocalizes ubiquitin ligase Nedd4 and has a role in transport and/or release of virions

Background

The ubiquitin system functions in a variety of cellular processes including protein turnover, protein sorting and trafficking. Many viruses exploit the cellular ubiquitin system to facilitate viral replication. In fact, herpes simplex virus (HSV) encodes a ubiquitin ligase (E3) and a de-ubiquitinating enzyme to modify the host's ubiquitin system. We have previously reported HSV type 2 (HSV-2) tegument protein UL56 as a putative adaptor protein of neuronal precursor cell-expressed developmentally down-regulated 4 (Nedd4) E3 ligase, which has been shown to be involved in protein sorting and trafficking.

Results

In this study, we visualized and characterized the dynamic intracellular localization of UL56 and Nedd4 using live-cell imaging and immunofluorescence analysis. UL56 was distributed to cytoplasmic vesicles, primarily to the trans-Golgi network (TGN), and trafficked actively throughout the cytoplasm. Moreover, UL56 relocalized Nedd4 to the vesicles in cells transiently expressing UL56 and in cells infected with HSV-2. We also investigated whether UL56 influenced the efficiency of viral replication, and found that extracellular infectious viruses were reduced in the absence of UL56.

Conclusion

These data suggest that UL56 regulates Nedd4 and functions to facilitate the cytoplasmic transport of virions from TGN to the plasma membrane and/or release of virions from the cell surface.

Putative Functional Domains of Human Cytomegalovirus pUL56 Involved in Dimerization and Benzimidazole D-Ribonucleoside Activity

Background

Benzimidazole d-ribonucleosides inhibit DNA packaging during human cytomegalovirus (HCMV) replication. Although they have been shown to target pUL56 and pUL89 (the large and small subunits of the HCMV terminase, respectively) their mechanism of action is not yet fully understood. We aimed here to better understand HCMV DNA maturation and the mechanism of action of benzimidazole derivatives.

Methods

The HCMV pUL56 protein was studied by sequence analysis of the HCMV UL56 gene and herpesvirus counterparts combined with primary structure analysis of the corresponding amino acid sequences.

Results

The UL56 sequence analysis of 45 HCMV strains and counterparts among herpesviruses allowed the identification of 12 conserved regions. Moreover, comparison with the product of gene 49 (gp49) of bacteriophage T4 suggested that the pUL56 zinc finger is localized close to the dimerization site of pUL56, providing a spatial organization of the catalytic site that allows recognition and cleavage of DNA.

Conclusions

This study provides a basis to investigate the mechanism of concatemeric DNA cleavage and a biochemical basis for DNA packaging inhibition by benzimidazole derivatives.

Herpes simplex virus type 2 UL56 interacts with the ubiquitin ligase Nedd4 and increases its ubiquitination

The herpes simplex virus UL56 gene is conserved among most members of the Alphaherpesvirinae family and plays a critical role in viral pathogenicity in vivo. The HSV-2 UL56 protein (UL56) is a C-terminally anchored type II membrane protein that is predicted to be inserted into the virion envelope, leaving its N-terminal domain in the tegument. UL56 interacts with KIF1A and UL11. Here we report that UL56 also interacts with the ubiquitin ligase Nedd4 and increases its ubiquitination. Nedd4 was identified as a UL56-interacting protein by a yeast two-hybrid screen. UL56 bound to Nedd4 via its PY motifs. Nedd4 was phosphorylated and degraded in wild-type HSV-2-infected cells but not in cells infected with a UL56-deficient mutant. Ubiquitination assays revealed that UL56 increased ubiquitinated Nedd4, which was actively degraded in infected cells. UL56 also caused a decrease in Nedd4 protein levels and the increased ubiquitination in cotransfected cells. However, UL56 itself was not ubiquitinated, despite its interaction with Nedd4. Based on these findings, we propose that UL56 regulates Nedd4 in HSV-2-infected cells, although deletion of UL56 had no apparent effect on viral growth in vitro.

Anti-CeHV1 antibodies of two cynomolgus macaques cross-react with HSV2 but not HSV1 antigens in ELISA

BACKGROUND

The aim of the study was to compare the cross-reactivity of macaque anti-CeHV1 antibodies with type 1 and type 2 human herpes simplex viruses (HSV1 and HSV2).

METHODS

We studied the serum of 344 animals which had been tested either positive (n = 39) or negative (n = 305) for the presence of CeHV1 antibodies by expert laboratories. Macaque serums were studied by means of two ELISA: one based on HSV1 antigen-coated wells, the other on polystyrene beads coated with HSV1 and HSV2 antigens in approximately equal proportions.

RESULTS

In the serum of two animals originating from Vietnam, we found anti-CeHV1 antibodies cross-reacting with HSV2 but not with HSV1 antigens. For the serum with the highest titer, inhibition by soluble antigens confirmed the high affinity of the antibodies for HSV2 antigens.

CONCLUSIONS

Tests using HSV1 and HSV2 in a combined way are better suited to macaque screening than tests using only HSV1 antigens.

Naturally transmitted herpesvirus papio-2 infection in a black and white colobus monkey

CASE DESCRIPTION

A 6.5-year-old female eastern black and white colobus monkey (Colobus guereza) was evaluated after acute onset of ataxia and inappetence.

CLINICAL FINDINGS

The monkey was ataxic and lethargic, but no other abnormalities were detected via physical examination, radiography, or clinicopathologic analyses. During the next 2 days, the monkey's clinical condition deteriorated, and its WBC count decreased dramatically. Cytologic examination of a CSF sample revealed marked lymphohistiocytic inflammation.

TREATMENT AND OUTCOME

Despite supportive care, the monkey became apneic; after 20 hours of mechanical ventilation, fatal cardiac arrest occurred. At necropsy, numerous petechiae were detected within the white matter tracts of the brain; microscopic lesions of multifocal necrosis and hemorrhage with intranuclear inclusions identified in the brain and adrenal glands were consistent with an acute herpesvirus infection. A specific diagnosis of herpesvirus papio-2 (HVP-2) infection was made on the basis of results of serologic testing; PCR assay of tissue specimens; live virus isolation from the lungs; and immunohistochemical identification of the virus within brain, spinal cord, and adrenal gland lesions. Via phylogenetic tree analysis, the colobus HVP-2 isolate was grouped with neuroinvasive strains of the virus. The virus was most likely transmitted to the colobus monkey through toys shared with a nearby colony of baboons (the natural host of HVP-2).

CLINICAL RELEVANCE

To the authors' knowledge, this is the first reported case of natural transmission of HVP-2 to a nonhost species. Infection with HVP-2 should be a differential diagnosis for acute encephalopathy in primate monkeys and humans, particularly following exposure to baboons.

The ribonucleotide reductase domain of the R1 subunit of herpes simplex virus type 2 ribonucleotide reductase is essential for R1 antiapoptotic function

The R1 subunit (ICP10) of herpes simplex virus type 2 (HSV-2) ribonucleotide reductase (RR), which in addition to its C-terminal reductase domain possesses a unique N-terminal domain of about 400 aa, protects cells against apoptosis. As the NH2domain on its own is not antiapoptotic, it has been postulated that both domains of R1 or part(s) of them could be necessary for this function. Here, N- and C-terminal deletions were introduced in HSV-2 R1 to map the domain(s) involved in its antiapoptotic potential. The results showed that, whereas most of the NH2domain including part of the recently described putativeα-crystallin domain is dispensable for antiapoptotic activity, it is the integrity of the structured RR domain that is required for protection. As theα-crystallin domain appears to play an important role in protein folding and oligomerization, the N-terminal boundary of the antiapoptotic domain could not be defined precisely. In addition, this study provided evidence that overexpression of HSV-2 R2 at levels up to 30-fold more than HSV-2 R1 did not decrease protection from tumour necrosis factor alpha, indicating that the R1 surface where R2 binds is not involved in antiapoptotic activity. Importantly, this result suggests that the co-expression of both RR subunits during the lytic cycle should not affect protection from this cytokine.

New Functional Domains of Human Cytomegalovirus pUL89 predicted by Sequence Analysis and Three-Dimensional Modelling of the Catalytic Site DEXDc

Introduction

Benzimidazole d-ribonucleosides inhibit DNA packaging during human cytomegalovirus (HCMV) replication. Although they have been shown to target pUL56 and pUL89, the large and small subunits of the HCMV terminase respectively, their mechanism of action is not yet fully understood.

Methods and results

To better understand HCMV DNA maturation and the mechanism of action of benzimidazole derivatives, we studied the HCMV pUL89 protein by a genetic approach combined with primary structure analysis. The pUL89 sequence analysis of 25 HCMV strains and counterparts among herpesviruses allowed identification of 12 conserved regions. We also built a three-dimensional model of the pUL89 ATPasic catalytic site, including ATPase motor motifs I, II and III, that may facilitate the development of future antiviral drugs active against HCMV. Finally, we identified several putative functional domains in pUL89, such as pUL89 zinc finger (pUL89-ZF), DNA cutting sites and portal binding sites, that are probably involved in CMV DNA cleavage and packaging.

Genomic cartography of varicella-zoster virus: a complete genome-based analysis of strain variability with implications for attenuation and phenotypic differences

In order to gain a better perspective on the true variability of varicella-zoster virus (VZV) and to catalogue the location and number of differences, 11 new complete genome sequences were compared with those previously in the public domain (18 complete genomes in total). Three of the newly sequenced genomes were derived from a single strain in order to assess variations that can occur during serial passage in cell culture. The analysis revealed that while VZV is relatively stable genetically it does posses a certain degree of variability. The reiteration regions, origins of replication and intergenic homopolymer regions were all found to be variable between strains as well as within a given strain. In addition, the terminal viral sequences were found to vary within and between strains specifically at the 3' end of the genome. Analysis of single nucleotide polymorphisms (SNPs) identified a total of 557 variable sites, 451 of which were found in coding regions and resulted in 187 different in amino acid substitutions. A comparison of the SNPs present in the two gE mutant strains, VZV-MSP and VZV-BC, suggested that the missense mutation in gE was primarily responsible for the accelerated cell spread phenotype. Some of the variations noted with high passage in cell culture are consistent with variations seen in the IE62 gene of the vaccine strains (S628G, R958G and I1260V) that may help in pinpointing variations essential for attenuation. Although VZV has been considered to be one of the most genetically stable human herpesviruses, this initial assessment of genomic VZV cartography provides insight into ORFs with previously unreported variations.

The complete genome sequence of herpesvirus papio 2 (Cercopithecine herpesvirus 16) shows evidence of recombination events among various progenitor herpesviruses

We have sequenced the entire genome of herpesvirus papio 2 (HVP-2; Cercopithecine herpesvirus 16) strain X313, a baboon herpesvirus with close homology to other primate alphaherpesviruses, such as SA8, monkey B virus, and herpes simplex virus (HSV) type 1 and type 2. The genome of HVP-2 is 156,487 bp in length, with an overall GC content of 76.5%. The genome organization is identical to that of the other members of the genus Simplexvirus, with a long and a short unique region, each bordered by inverted repeats which end with an "a" sequence. All of the open reading frames detected in this genome were homologous and colinear with those of SA8 and B virus. The HSV gene RL1 (gamma(1)34.5; neurovirulence factor) is not present in HVP-2, as is the case for SA8 and B virus. The HVP-2 genome is 85% homologous to its closest relative, SA8. However, segment-by-segment bootstrap analysis of the genome revealed at least two regions that display closer homology to the corresponding sequences of B virus. The first region comprises the UL41 to UL44 genes, and the second region is located within the UL36 gene. We hypothesize that this localized and defined shift in homology is due to recombination events between an SA8-like progenitor of HVP-2 and a herpesvirus species more closely related to the B virus. Since some of the genes involved in these putative recombination events are determinants of virulence, a comparative analysis of their function may provide insight into the pathogenic mechanism of simplexviruses.

Herpes simplex virus and varicella-zoster virus: why do these human alphaherpesviruses behave so differently from one another?

Members of the Herpesviridae family of viruses are classified into the alpha, beta and gamma subfamilies. The alpha subfamily is estimated to have diverged from the beta and gamma subfamilies 200-220 million years ago. The ancestors of the herpes simplex virus (HSV) and the varicella-zoster virus (VZV), two ubiquitous and clinically important human pathogens, appeared 70-80 million years ago. As these viruses coevolved with their specific primate hosts, genetic rearrangements led to the development of the contemporary alphaherpesviruses and their distinct complement of genes. Here the distinct features of HSV and VZV are discussed in terms of their transmissibility, clinical picture, tissue tropism, establishment of latency/reactivation and immune evasion, which can, at least in part, be explained by differences in their genomes.