Monkey B virus (Cercopithecine herpesvirus 1).

Macaques are a particularly valuable nonhuman primate model for a wide variety of biomedical research endeavors. B virus (Cercopithecine herpesvirus 1; BV) is an alpha-herpesvirus that naturally infects conventional populations of macaques. Serious disease due to BV is rare in macaques, but when transmitted to humans, BV has a propensity to invade the central nervous system and has a fatality rate greater than 70% if not treated promptly. The severe consequences of human BV infections led to the inclusion of BV in the original NIH list of target viruses for elimination by development of specific pathogen-free rhesus colonies. In macaques and especially in humans, diagnosis of BV infection is not straightforward. Furthermore, development and maintenance of true BV specific pathogen-free macaque colonies has proven dif cult. In this overview we review the natural history of BV in macaques, summarize what is known about the virus at the molecular level, and relate this information to problems associated with diagnosis of BV infections and development of BV-free macaque colonies.

Sequence and genetic arrangement of the UL region of the monkey B virus (Cercopithecine herpesvirus 1) genome and comparison with the UL region of other primate herpesviruses.

The complete DNA sequence of the unique long (U(L)) region of monkey B virus (BV) was determined. Based on sequence homology and the presence of transcriptional control element motifs, homologues of every open reading frame present in the U(L) region of the Human herpesvirus 1 (herpes simplex virus 1, HSV-1) and Human herpesvirus 2 (herpes simplex virus 2, HSV-2) genomes were identified in BV. The BV genes are arranged in the same order and orientation as in HSV. These results demonstrate that the BV U(L) region is entirely co-linear with that of HSV-1 and HSV-2.

Differential detection of B virus and rhesus cytomegalovirus in rhesus macaques.

Non-human primate herpesviruses establish and maintain a lifelong persistent infection in immunocompetent hosts in the absence of clinical signs of disease. A fundamental issue for understanding the natural history of non-human primate herpesviruses is whether the viruses are maintained in a truly latent state or one characterized by a low level of chronic expression. To address this issue, a real-time PCR assay was developed to quantify Cercopithecine herpesvirus type 1 (B virus) DNA in mucosal fluids of rhesus macaques. This assay was rapid, sensitive (10 genome copies) and specific for B virus obtained from multiple species of macaques. The shedding profile of B virus was compared to another endemic herpesvirus, rhesus cytomegalovirus (RhCMV), in colony-reared monkeys. Mucosal swabs or saliva samples were taken daily from two groups of seropositive monkeys undergoing either a stressful relocation (group 1) or daily chair restraint (group 2). B virus DNA was detected in mucosal fluids from four animals relocated during the breeding season (group 1) but not from 10 animals moved at other times of the year. No B virus DNA was detected in any group 2 monkey. In contrast, RhCMV DNA was detected in the majority of animals of both groups 1 and 2. Detection of B virus DNA shedding is a relatively rare event associated with the breeding season, while RhCMV DNA is persistently detected in mucosal fluids of most monkeys.

One-step PCR to distinguish B virus from related primate alphaherpesviruses.

By adding betaine to the PCR mixture, we previously established a PCR method to amplify a DNA segment of the glycoprotein G gene of B virus (BV) derived from a rhesus macaque. We have found that DNA of other BV strains derived from cynomolgus, pigtail, and lion-tailed macaques can also serve as the template in our PCR assay. Under the same conditions no product was obtained with DNA of simian agent 8 of green monkeys and Herpesvirus papio 2 of baboons, or the human herpes simplex viruses types 1 and 2. Thus, this PCR method is useful to discriminate BV from other closely related primate alphaherpesviruses.

Sequence and genetic arrangement of the U(S) region of the monkey B virus (cercopithecine herpesvirus 1) genome and comparison with the U(S) regions of other primate herpesviruses.

The sequence of the unique short (U(S)) region of monkey B virus (BV) was determined. The 13 genes identified are arranged in the same order and orientation as in herpes simplex virus (HSV). These results demonstrate that the BV U(S) region is entirely colinear with that of HSV type 1 (HSV-1), HSV-2, and simian agent 8 virus.

Rapid discrimination of monkey B virus from human herpes simplex viruses by PCR in the presence of betaine.

A PCR method to amplify DNA segments of the glycoprotein G gene of monkey B virus (BV) was achieved by adding betaine to the PCR mixture, in spite of the high G+C content of this gene. No product was obtained when DNA of human herpes simplex viruses (HSVs) was used as the template under the same conditions. Thus, this PCR method is useful in discriminating BV from HSVs.

Retrospective analysis of an outbreak of B virus infection in a colony of DeBrazza's monkeys (Cercopithecus neglectus).

In 1981, an outbreak of herpetic disease developed in a colony of DeBrazza's monkeys (Cercopithecus neglectus). In seven of eight infected animals, clinical signs of infection included vesicular and ulcerative lesions on the lips, tongue, and/or palate. Histologic examination of lesions revealed intranuclear inclusion bodies, and electron microscopy revealed nucleocapsids and virions with typical herpesvirus morphology. Although a virus was isolated that appeared similar to monkey B virus, techniques available at the time did not allow precise identification of the virus. Analysis of serum from one surviving monkey collected 12 years after the outbreak revealed a pattern of reactivity characteristic of B virus-positive serum on the basis of results of ELISA and western immunoblot analysis. Polymerase chain reaction analysis of archived paraffin-embedded tissue specimens and molecular analysis of the one viral isolate obtained from a DeBrazza's monkey indicated that the virus responsible for the outbreak was a new genotype of B virus. Testing of sera from lion-tailed macaques (Macaca silenus) housed in an adjacent cage at the same zoo indicated that these animals harbored this virus and, thus, were the likely source of the virus that infected the DeBrazza's monkeys. This study documents usefulness of archiving samples from disease outbreaks for later analysis. In addition, this incident underscores the importance of considering herpes B virus infection when outbreaks of disease having characteristics of herpetic infections develop in nonhuman primates kept at institutions that also house macaques.

Viral isolates derived from simian varicella epizootics are genetically related but are distinct from other primate herpesviruses.

Epizootics of a natural varicella-like disease occur in populations of nonhuman primates. Several primate herpesviruses have been isolated from these epizootics, but the relatedness of these isolates to each other is not well-defined. In this study, we demonstrated that the restriction endonuclease (REn) profiles of four epidemiologically distinct isolates were similar, although not identical, indicating that simian varicella epizootics are caused by various strains of simian varicella virus (SVV). The genetic variation among the isolates did not map to a specific region of the SVV genome and REn differences were detected within the SVV DNA long component and the inverted repeat region. Southern blot hybridization demonstrated that SVV is more closely related to varicella-zoster virus than to other primate herpesviruses. The study indicates that the current herpesvirus classification scheme should be changed to include SVV as a single taxonomic group within the Varicellovirus genus of alphaherpesviruses. In addition, REn profiles of SVV isolates, derived from primary and secondary episodes of simian varicella in the same monkey, were identical, providing evidence for SVV reactivation in a latently infected monkey.

The simian herpesviruses.

Increased use of monkeys in biomedical research has led to an intensified awareness of potential dangers posed by zoonotic infections. Zoonoses have an impact not only upon human health and safety but also upon continued availability of nonhuman primate resources for the biomedical community. Neurotropic herpesviruses indigenous to primates are significant owing to their potential for causing severe or fatal infections when transmitted between human and nonhuman primates or between different species of monkeys. Although the macaque herpesvirus (B virus) is known to many investigators, other simian herpesviruses have remained relatively obscure in spite of reports of disease-causing potential. In this review we summarize what is known about the natural history and pathogenic potential of simian alpha-herpesviruses. Recent research into the molecular biology of this group of viruses is also reviewed, and recent advances toward development of diagnostic tests based on these data are discussed.

Herpesvirus papio 2, an SA8-like alpha-herpesvirus of baboons.

Several SA8 isolates obtained from baboons were compared to the prototype SA8 herpesvirus of African green monkeys. SDS-PAGE and restriction enzyme analyses revealed definite differences between green monkey and baboon isolates. DNA and amino acid sequences of the gB, gD and gJ glycoprotein genes exhibited substantial differences in variable regions. For the gB and gD, the amount of amino acid substitutions between SA8 and the baboon viruses was comparable to levels observed between analogous genes of SA8 & B virus or HSV1 & HSV2. Although a high degree of antigenic cross-reactivity was apparent, virus-specific antigenic determinants were also readily detected. Phylogenetic analyses supported separation of the baboon isolates and SA8 as distinct viruses. Taken together these results suggest that although closely related to SA8, the baboon viruses represent a distinct simian alpha-herpesvirus which we propose be designated Herpesvirus papio 2.

Biology of B virus in macaque and human hosts: a review.

B virus is a zoonotic alpha-herpesvirus enzootic in Asian monkeys of the genus Macaca. At least 25 cases of human disease caused by B virus have occurred to date, leading to death in 16 instances. Advances in the technology available for the diagnosis of B virus infection and in the agents for its treatment are improving the prognosis for cases in human beings. Efforts are under way at several institutions in the United States to establish B virus-free colonies of rhesus macaques for use in biomedical research. Unfortunately, the epidemiology of B virus in group-housed macaques is poorly understood. The elucidation of factors important in the transmission of B virus between monkeys will greatly enhance efforts to eradicate this virus and may help to minimize further human exposure to the agent.

Discrimination between twenty isolates of herpesvirus simiae (B virus) by restriction enzyme analysis of the viral genome.

Twenty isolates, obtained from adult breeding monkeys, were all identified as herpesvirus simiae (B virus) by neutralisation with polyclonal B virus antiserum. Subsequent analysis of restriction enzyme profiles produced by digestion of DNA from the isolates enabled discrimination to be made between them. In particular Cynomolgus monkey isolates could be distinguished from those of Rhesus animals. One isolate (isolate 9) could not be typed either as B virus or as the antigenically related herpesvirus SA8, despite neutralisation by B virus antiserum. Unlike herpes simplex virus, B virus isolates could not be divided into oral and genital types on the basis of restriction enzyme profiles.

Simian alphaherpesviruses and their relation to the human herpes simplex viruses.

Biochemical and immunological properties of structural and non-structural polypeptides of the human simplex viruses (HSV1 and HSV2) and four related herpesviruses of non-human primates [Herpesvirus simiae (B virus), H. cercopithicus (SA8), H. saimiri 1 (HVS 1), and H. ateles 1 (HVA 1)] were compared. Using a radioimmunoassay (RIA), the presence of antigenic determinants shared among all six viruses was demonstrated. The relative degree of antigenic cross-reactivity among these viruses was further assessed by competition RIA. Antigenically, HSV 1 and HSV 2 were most closely related to each other although both SA 8 and B virus were also very closely related to HSV 1. Considerably less cross-reactivity existed between either HVS 1 or HVA 1 and the other four primate herpesviruses. Cross-hybridization between simian and human herpesvirus genomes demonstrated that extensive homology exists between each of the simian viruses and both HSV1 and HSV 2. Viral polypeptides bearing common antigenic determinants were identified by immune precipitation of infected cell polypeptides and by immunoblotting. Among the polypeptides of HSV which were recognized by antisera to simian viruses were the VP 5 and p40 proteins, both of which are structural components of the virion nucleocapsid. Using recombinant plasmids containing sequences of the HSV 1 VP5, p40, DNA polymerase, major DNA binding protein, and TK enzyme genes, homologous sequences were detected in all four simian viruses. Together, these results demonstrate that HSV 1, HSV 2, SA 8, and B virus form a closely related sub-group of the primate herpesviruses; HVS 1 and HVA 1 are also related to the other four primate herpesviruses, albeit more distantly.