Search

Our overall aim is to develop epitope-based assays for accurate differential diagnosis of B virus zoonotic infections in humans. Antibodies to cross-reacting epitopes on human-simplexviruses continue to confound the interpretation of current assays where abundant antibodies exist from previous infections with HSV types 1 and 2. To find B virus-specific epitopes we cloned ten monoclonal antibodies (mAbs) from the hybridomas we produced. Our unique collection of rare human sera from symptomatic and asymptomatic patients infected with B virus was key to the evaluation and identification of the mAbs as reagents in competition ELISAs (mAb-CE). The analysis of the ten mAbs revealed that the target proteins for six mAbs was glycoprotein B of which two are reactive to simian simplexviruses and not to human simplexviruses. Two mAbs reacted specifically with B virus glycoprotein D, and two other mAbs were specific to VP13/14 and gE-gI complex respectively. The mAbs specific to VP13/14 and gE-gI are strain specific reacting with B virus isolates from rhesus and Japanese macaques and not with isolates from cynomolgus and pigtail macaques. The mAb-CE revealed that a high proportion of naturally B virus infected rhesus macaques and two symptomatic humans possess antibodies to epitopes of VP13/14 protein and on the gE-gI complex. The majority of sera from B virus infected macaques and simplexvirus-infected humans competed with the less specific mAbs. These experiments produced a novel panel of mAbs that enabled B virus strain identification and confirmation of B virus infected macaques by the mAb-CE. For human sera the mAb-CE could be used only for selected cases due to the selective B virus strain-specificity of the mAbs against VP13/14 and gE/gI. To fully accomplish our aim to provide reagents for unequivocal differential diagnosis of zoonotic B virus infections, additional mAbs with a broader range of specificities is critical.

A 2-year-old, female, simian immunodeficiency virus E543-infected rhesus macaque (Macaca mulatta) was presented for necropsy following euthanasia due to a history of diarrhea, weight loss, and a small, round ulcer along the left labial commissure. Histopathologic examination of the ulcer revealed infiltration by large numbers of degenerate and nondegenerate neutrophils and macrophages admixed with syncytial epithelial cells. Rare epithelial cells contained herpetic inclusion bodies. These cells stained positive for Human herpesvirus 1 via immunohistochemistry, and DNA sequencing confirmed the presence of closely related Macacine herpesvirus 1 (B virus).

Herpes B virus infection is almost asymptomatic in macaques (Macaca spp.), which are the natural hosts of this pathogen, but is the cause of high mortality in humans. Reactivation of the latent virus in the trigeminal ganglia (TG) results in the shedding of infectious particles into the oral mucosal membrane. Saliva contaminated with the reactivated virus from the ganglia of the natural host is considered to be important for viral transmission to humans and other monkeys. In the present study, we investigated the prevalence of the herpes B virus genome in the left and right TG of seropositive asymptomatic cynomolgus macaques. The latent virus genome was detected using a polymerase chain reaction and microplate hybridization assay. We found that the virus DNA was present in one or both TG of 12 of the 30 macaques (40%) tested, with the virus being detected from both TG in five of the 12 macaques and from a single TG in the remaining seven.

Serologic testing for antibody to monkey B virus (BV) in macaque sera is problematic due to the biohazardous nature of BV antigens. Herpesvirus papio 2 (HVP2), a herpesvirus of baboons, is nonpathogenic to humans and is genetically and antigenically more closely related to BV than is human herpes simplex virus 1. This paper describes the results of our in-house laboratory that compared a BV antigen-based enzyme-linked immunosorbent assay (ELISA) by commercial testing laboratory and an HVP2-based ELISA in our laboratory by using 447 sera from 290 rhesus monkeys. The HVP2-based ELISA identified as positive 99.11% of the sera identified as BV-positive by the BV ELISA. The BV antigen-based ELISA identified as positive 98.21% of the sera identified as BV-positive by the HVP2-based ELISA. The HVP2 ELISA also identified two BV-negative and six BV-equivocal sera as positive. Both ELISAs identified the same 85 negative and three equivocal samples as negative and equivocal, respectively. The high degree of correlation (weighted kappa coefficient, 0.94) between the two tests indicates that the HVP2 ELISA is a sensitive and reliable assay for in-house testing of the BV status of rhesus monkeys.

Herpes B virus DNA was specifically amplified by PCR, targeting the regions that did not cross-react with herpes simplex virus (HSV). The amplified products, which were shown to be highly genetic polymorphisms among herpes B virus isolates, were identified by microplate hybridization with probes generated by PCR. The products immobilized in microplate wells were hybridized with the biotin-labeled probes derived from the SMHV strain of herpes B virus. The amplified products derived from the SMHV and E2490 strains of herpes B virus were identified by microplate hybridization. PCR products amplified from the trigeminal ganglia of seropositive cynomolgus macaques were identified as herpes B virus DNA. The utility of the PCR-microplate hybridization assay for genetic detection and identification of the polymorphic region of herpes B virus was determined.

Herpesvirus papio 2 (HVP2), which infects baboons, is much more closely related genetically and antigenically to monkey B virus (BV) than to human herpes simplex virus 1(HSV1) and other related herpes viruses. The usefulness of HVP2 as an alternative test antigen in immunoblotting assays to detect BV-antibody in macaque monkey sera was assessed. Six HVP2 proteins reacted with BV-positive sera in immunoblotting. No specific bands could be detected with BV-negative sera. These results show the usefulness of HVP2 antigen as an alternative and safer antigen than authentic BV antigen in detecting BV antibody in immunoblotting.

In Puerto Rico, risk for transmission of B-virus from free-ranging rhesus monkeys to humans has become a serious challenge. An incident with an injured rhesus monkey, seropositive for B-virus, resulted in inappropriate administration of antiviral postexposure prophylaxis. This incident underscores the importance of education about risks associated with interactions between humans and nonhuman primates.

Nonhuman primates are widely used in biomedical research because of their genetic, anatomic, and physiologic similarities to humans. In this setting, human contact directly with macaques or with their tissues and fluids sometimes occurs. Cercopithecine herpesvirus 1 (B virus), an alphaherpesvirus endemic in Asian macaques, is closely related to herpes simplex virus (HSV). Most macaques carry B virus without overt signs of disease. However, zoonotic infection with B virus in humans usually results in fatal encephalomyelitis or severe neurologic impairment. Although the incidence of human infection with B virus is low, a death rate of >70% before the availability of antiviral therapy makes this virus a serious zoonotic threat. Knowledge of the clinical signs and risk factors for human B-virus disease allows early initiation of antiviral therapy and prevents severe disease or death.

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.

Detection of infectious viruses in clinical samples typically relies on daily examination of inoculated cell cultures for appearance of virus-induced cytopathic effect (CPE), with subsequent immunologic or genetic analysis to identify the specific virus producing the CPE. Performing virus isolation on samples suspected of containing Cercopithecine herpesvirus 1 (monkey B virus [BV]) is dangerous due to the extreme neuropathogenicity of this virus in humans, and minimally requires biosafety level 3 (BSL-3) facilities. To provide a safer method of detecting infectious BV in clinical samples, the eucaryotic green fluorescent protein (GFP) coding sequence was flanked with BV sequences containing transcriptional control elements. This construct was placed into a stealth vector and transfected into Vero cells, then stable transformed cell lines were selected. These cells express GFP only when infected with BV or other related primate herpesviruses. Expression of GFP allows detection of infectious BV in cultures sooner and more reliably than does standard microscopic observation for CPE. The ability to detect BV by GFP expression eliminates the need for further testing to identify the virus as an alpha-herpesvirus following development of CPE, thus allowing cell cultures to be sealed at inoculation. Although not entirely specific for BV, this cell line will make detection of infectious BV in samples collected from macaques safer to perform.

The Japanese macaque or snow monkey (Macaca fuscata) is an autochthonous monkey in Japan. It has long been assumed that the monkey population was not infected with Cercopithecine herpesvirus 1 (monkey B virus [BV]) since cases of human BV infection have never been reported in Japan. Although serologic testing of captive snow monkeys in Japan revealed antibodies to BV, it was thought that native Japanese macaques had either been infected with herpes simplex virus from humans or with BV from other imported macaque species. To clarify this issue, we performed polymerase chain reaction (PCR) analysis to amplify BV sequences from trigeminal ganglia of 30 Japanese macaque monkeys that were seropositive for BV. Sequences from two BV genes, UL27 (360 bp) and UL19 (1.0 Kbp), from 3 of 30 monkeys were amplified. Results of restriction fragment length polymorphism analysis and DNA sequencing of the fragments provided evidence that native Japanese macaques are infected with BV. Phylogenetic analysis indicated that these monkeys harbor their own genotype of BV that is different from other known BV genotypes, and provided additional evidence supporting the co-evolution of BV and macaques.

Herpesvirus B (Cercopithecine herpesvirus 1) has been implicated as the cause of approximately 40 cases of meningoencephalitis affecting persons in direct or indirect contact with laboratory macaques. However, the threat of herpesvirus B in nonlaboratory settings worldwide remains to be addressed. We investigated the potential for exposure to herpesvirus B in workers at a "monkey forest" (a temple that has become a tourist attraction because of its monkeys) in Bali, Indonesia. In July 2000, 105 workers at the Sangeh Monkey Forest in Central Bali were surveyed about contact with macaques (Macaca fascicularis). Nearly half of those interviewed had either been bitten or scratched by a macaque. Prevalence of injury was higher in those who fed macaques. Serum from 31 of 38 Sangeh macaques contained antibodies to herpesvirus B. We conclude that workers coming into contact with macaques at the Sangeh Monkey Forest are at risk for exposure to herpesvirus B.

To study the pathogenesis of simian varicella virus (SVV) infection in its natural primate host, we inoculated adult SVV-seronegative African green monkeys intratracheally with 10(3)-10(4) PFU of SVV, sacrificed them 11 days, 2, 5, 10, and 12 months postinfection (p.i.), and examined lung, liver, and ganglia for SVV DNA and RNA. PCR analysis revealed SVV DNA in ganglia and viscera at 11 days and 2, 5, and 10 months p.i. Similarly, SVV transcripts corresponding to immediate early (IE), putative early (E), and late (L) SVV open-reading frames (ORFs) were found in liver, lung, and ganglia of most monkeys at multiple intervals for the 12-month study period. SVV-specific antigens were detected in ganglia and liver during acute varicella, but not in ganglia 12 months p.i. Analysis of control tissue (ganglia, lung, and liver) from uninfected SVV-seronegative adult African green monkeys did not reveal SVV DNA, SVV RNA, SVV-specific antigen, or varicella-specific pathological changes. Overall, intratracheal inoculation of SVV in African green monkeys resulted in the presence of viral DNA and transcription of multiple viral genes in many tissues for months after experimental infection.

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.

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.

Background and Purpose: National Institutes of Health's Division of Comparative Medicine has sponsored a multi-institutional program for the establishment of specific-pathogen-free (SPF) macaque colonies. B virus (Herpesvirus simiae, Cercopithecine herpesvirus type 1) has been targeted in this surveillance. Participating institutions have established individual timetables for frequency of testing and types of monitoring and husbandry techniques, all with the common goal of producing pathogen-free monkeys for research. The greatest biosecurity threat to the program comes from failure to detect seronegative latent infections, either in first-year macaques or macaques introduced in subsequent years, although these are supposed to operate as closed colonies., Methods: From January 1990 through December 1996, we screened macaques for B virus, using enzyme-linked immunoabsorbant assay (ELISA) and Western blot analysis., Results: During the first year, 1,097 macaques from six colonies were tested, and 88.4% tested negative for B virus. During the seventh year, 1,843 were tested, of which 99.7% tested negative. Seropositive macaques were detected as late as the seventh year., Conclusions: An aggressive program to establish an SPF colony of captive breeding macaques can be effective in reducing the risk of B-virus exposure.

On December 10, 1997, a 22-year-old female worker at a primate center died from Cercopithecine herpesvirus 1 (B virus) infection 42 days after biologic material (possibly fecal) from a rhesus macaque (Macaca mulatta) splashed into her right eye. This report summarizes the clinical features of her illness and the subsequent investigation by CDC in response to a technical assistance request from the Occupational Safety and Health Administration (OSHA) and presents interim recommendations to prevent ocular splash exposures. This investigation documented the hazard of ocular splashes and indicated that dendritic corneal lesions, such as herpetic skin vesicles, are not always present in B virus infection.

Although monkey B virus (herpesvirus simiae; BV) is common in all macaque species, fatal human infections appear to be associated with exposure to rhesus macaques (Macaca mulatta), suggesting that BV isolates from rhesus monkeys may be more lethal to nonmacaques than are BV strains indigenous to other macaque species. To determine if significant differences that would support this supposition exist among BV isolates, we compared multiple BV strains isolated from rhesus, cynomolgus, pigtail, and Japanese macaques. Antigenic analyses indicated that while the isolates were very closely related to one another, there are some antigenic determinants that are specific to BV isolates from different macaque species. Restriction enzyme digest patterns of viral DNA revealed marked similarities between rhesus and Japanese macaque isolates, while pigtail and cynomolgus macaque isolates had distinctive cleavage patterns. To further compare genetic diversity among BV isolates, DNA sequences from two regions of the viral genome containing genes that are conserved (UL27 and US6) and variable (US4 and US5) among primate alphaherpesviruses, as well as from two noncoding intergenic regions, were determined. From these sequence data and a phylogenetic analysis of them it was evident that while all isolates were closely related strains of BV, there were three distinct genotypes. The three BV genotypes were directly related to the macaque species of origin and were composed of (i) isolates from rhesus and Japanese macaques, (ii) cynomolgus monkey isolates, and (iii) isolates from pigtail macaques. This study demonstrates the existence of different BV genotypes which are related to the macaque host species and thus provides a molecular basis for the possible existence of BV isolates which vary in their levels of pathogenicity for nonmacaque species.

Two adult female cynomolgus monkeys (Macaca fascicularis) that had been housed together for 4 months died within 2 weeks of each other after brief illnesses. Monkey No. 1 presented with collapse, watery stool, and hypothermia and died overnight. Monkey No. 2 presented with dyspnea, nasal discharge, leukopenia, and hypoproteinemia and was euthanized after 2 days. Both animals had peritoneal effusions, massive necrosis of pharyngeal, esophageal, and gastric mucosa, and multifocal hepatic and pancreatic necrosis. Monkey No. 2 also had lingual ulcers and locally extensive necrosis of spleen, adrenal glands, and lymph nodes. Large numbers of eosinophilic intranuclear inclusion bodies were present in epithelial and syncytial cells adjoining the necrotic foci in Monkey No. 2 but were absent in Monkey No. 1. Monkey No. 1 seroconverted to cercopithecine herpesvirus 1 (CHV-1, commonly known as herpes B) in the month before death. CHV-1 was isolated from a sample of stomach from Monkey No. 2, and electron microscopy of liver from this animal demonstrated herpesvirus particles within hepatocytes. Both animals were seropositive for simian type D retrovirus, and the virus was cultured from the liver of Monkey No. 2. A diagnosis of disseminated CHV-1 infection was made, possibly occurring secondary to immunosuppression due to infection with simian type D retrovirus. Although a high percentage of cynomolgus monkeys are apparently infected with CHV-1, disseminated disease is rare. Because infection with CHV-1 in humans is associated with a high fatality rate, familiarity with the lesions of disseminated infection with this virus is important.

The prevalence of Herpesvirus papio 2 (HVP2) in several groups of captive and wild-caught baboons was determined by detection of anti-HVP2 antibodies in 133 sera of adult baboons. Over 90% of newly imported (wild-caught) adult olive baboons (Papio anubis) from Kenya and chacma baboons (P. ursinus) from South Africa were found to have anti-HVP2 titers. Similarly, approximately 85% of captive breeding colony baboons (P. anubis and P. cynocephalus) were seropositive for HVP2. Infected animals were generally easily identifiable by enzyme-linked immunosorbent assay because anti-HVP2 IgG titers in immune animals were usually high (16,000 to 64,000). There was little variation in the relative reactivity patterns of individual HVP2-immune sera when tested against herpes simplex viruses 1 and 2, monkey B virus, H. cercopithecus 2, and HVP2, or against different HVP2 strains. Also, differences were not detected between reactivity of olive and chacma baboon immune sera. Analysis of the polypeptide specificity of immune sera by western blot identified four viral antigens that were consistent targets of immune sera. These antigens were the gB glycoprotein, a pair of unidentified glycoproteins of 80 to 100 kDa, the gD glycoprotein, and a series of smaller capsid proteins. Additional viral proteins were variably recognized by individual immune sera. The results of this study indicate that HVP2 is a common infection of baboons; there is little antigenic variation among HVP2 strains; and there are several HVP2 antigens that represent consistent targets of the anti-HVP2 immune response of baboons.

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.

We have sequenced a simian varicella virus (SVV) open reading frame (ORF), 3,123 bp in length, whose product has 51% amino acid homology with the sequence encoded by the ORF of varicella-zoster virus gene 21. Several regions are highly conserved between the two ORFs, with homologies of approximately 80%. The SVV gene is transcribed in tissue culture cells productively infected with SVV and in monkey ganglia latently infected with SVV.

The importance of venereal modes of B virus (cercopithecine herpesvirus 1) transmission was evaluated in 49 rhesus monkeys tested at necropsy. Antibodies to B virus were demonstrated in 19 monkeys, but no active viral shedding was detected in mucosal swabs collected at death. The polymerase chain reaction demonstrated presence of the ICP 18.5 (UL28) gene of B virus in neuronal tissues of 15 monkeys presumed to be latently infected, including 12.8% of trigeminal and 22.9% of lumbosacral ganglia pools. Two monkeys tested positive at both sites. Breeding history was predictive of B virus seropositivity (odds ratio, 1.64; 95% confidence interval, 1.21-2.23; P < .05). The population attributable risk of B virus seropositivity due to breeding was 22.7%, similar to the proportion of monkeys with B virus DNA in neuronal tissues subserving the genital region. Sexual contact is a significant, but not predominant, mode of B virus transmission between monkeys.

Three men who had worked at the same animal research facility and had had contact with macaque monkeys were infected with B virus (Herpesvirus simiae). Their clinical presentations varied from self-limited aseptic meningitis syndrome to fulminant encephalomyelitis and death. Patient 1 was treated only after a respiratory arrest and other signs of advanced brain stem dysfunction had occurred. He died 8 days after hospital admission, despite treatment with acyclovir. Patient 2 presented with subtle signs and symptoms of brain stem encephalitis. He received antiviral therapy with intravenous ganciclovir. Patient 3 had a headache without meningismus and was also treated with acyclovir. Both patients 2 and 3 survived and did not have objective sequelae. Viral culturing, ELISA and western blot antibody testing, and magnetic resonance imaging all proved useful in the diagnosis of these patients' conditions.

Rapid diagnosis of B virus (herpesvirus simiae) infection in humans followed by early antiviral treatment is essential for the patient's survival. To improve laboratory diagnosis of B virus infections, a polymerase chain reaction (PCR)-based test using synthetic oligonucleotide primers and probe was developed to detect B virus DNA in clinical samples. After the specificity of the PCR was assessed for detection of several B virus isolates, the method was used to investigate human and monkey specimens, and results were compared with those obtained by viral culture. PCR appeared to be more sensitive than conventional virus isolation and thus of practical use for a rapid identification of B virus infection when conventional viral cultures are negative.

The epidemiology of B virus infection in a large (n = 157) cohort of rhesus macaques at the California Regional Primate Research Center was evaluated prospectively from September 1989 through January 1991 by serial physical examinations, a behavioral substudy (n = 51), and repeated diagnostic testing. Half were B virus antibody-positive at baseline; subsequently, incident cases of infection were documented through serology alone (42) or with virus isolation (5). Eight recurrent infections and a single symptomatic (primary) case were observed. Risk of B virus infection increased as monkeys aged, with few > 3 years old remaining uninfected. Postpubertal monkeys and those entering sexual adolescence (2-3 years) were at greatest risk, although wounding by cagemates and breeding history (for females) were both significant predictors of time to infection. B virus was isolated from oral or conjunctival and genital tissues in equal proportions. Transmission occurred only during the breeding season, possibly coinciding with an elevation in social stressors in the population.

A 26-year-old veterinary technician who became infected with B virus at the site of a needlestick injury is described. After the patient was treated with intravenous acyclovir, all cultures became negative for B virus and have remained so during treatment with oral acyclovir. The literature on infections due to B virus in humans is reviewed, and a detailed discussion of the various aspects of this simian herpesvirus is presented.

3 different types of observation all demonstrated that B virus (Herpesvirus simiae) infection of monkeys was not confined to the mouth but was also a genital infection. (1) Latent B virus was reactivated in a seropositive female monkey, which was immunosuppressed with antilymphocyte globulin, and infectious virus was excreted in the genital tract. (2) During an epizootic in a breeding colony, B virus was isolated from 4 genital and 3 oral sites as well as from a skin lesion. (3) In cultures of sensory nerve ganglia taken from seropositive monkeys, B virus was recovered more frequently from ganglia subserving the genital region than the oral region.

Studies of B virus (Herpesvirus simiae) antibody in several species of macaque lead to the following generalizations. Newborn monkeys are not infected with B virus, even when born of seropositive mothers. Young monkeys remain uninfected until they become adults. The majority of adults develop B virus antibody unless their physical contact with seropositive adults is restricted. These observations are consistent with sexual transmission of B virus and classification of the disease in monkeys as venereal. However, infection at oral and dermal sites also occurs and may play a part in monkey-to-monkey transmission. Epizootics of B virus occurred during early attempts to start B virus-free breeding colonies. They appeared to originate from reactivated latent B virus in adult monkeys which had only low titres of antibody. The stress produced when groups of adult strangers were assembled to form breeding colonies was the most effective known inducer of latent B virus. Total exclusion of animals with any trace of antibody has enabled the establishment of new breeding colonies which are free from B virus.

The suspected ability of herpes simiae (B virus) to persist in a latent form has been confirmed in rhesus monkeys. The virus was recovered from primary oral lesions of 2 young monkeys and again, 6 months after disappearance of symptoms, from cultures of Gasserian ganglia taken from the same individuals. B virus was identified by its effects in vivo and in vitro and in cross neutralization tests with antisera to reference B virus and herpes simplex virus. Tests showed that the same virus was present in oral lesions and in ganglia. The one-way immunological relationship between herpes simplex virus and B virus was clearly shown in results of cross neutralization tests.

When small doses of herpes simplex virus (HSV) were given to rabbits a significant degree of protection was afforded against later infection with herpes simiae (B virus). Only 12/47 rabbits died within 3 weeks of receiving B virus dosages that would normally have proved lethal. B virus became latent in survivors and was recovered from brain and spinal cord suspensions from rabbits which died within 6 months and from dorsal root ganglia of rabbits which had survived for more than 2 years without overt signs of infection. A minority of the survivors tested also yielded HSV. Rabbits with latent B virus in the ganglia showed little or no detectable neutralizing antibody to B virus. The possibility is discussed that human populations having a high frequency occurrence of HSV antibody may include carriers of latent B virus.

The methods used at the Clinical Research Centre, Northwick Park Hospital, to treat wounds potentially infected with neurotropic viruses are outlined. Emphasis is laid on first aid and on surgical attention. Patients should remain under medical supervision for at least four weeks after the injury, the need for specific post-exposure treatment depending on the nature of the exposure.