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

Research Relevant Conditions and Pathology in Nonhuman Primates

Biomedical research involving animal models continues to provide important insights into disease pathogenesis and treatment of diseases that impact human health. In particular, nonhuman primates (NHPs) have been used extensively in translational research due to their phylogenetic proximity to humans and similarities to disease pathogenesis and treatment responses as assessed in clinical trials. Microscopic changes in tissues remain a significant endpoint in studies involving these models. Spontaneous, expected (ie, incidental or background) histopathologic changes are commonly encountered and influenced by species, genetic variations, age, and geographical origin of animals, including exposure to infectious or parasitic agents. Often, the background findings confound study-related changes, because numbers of NHPs used in research are limited by animal welfare and other considerations. Moreover, background findings in NHPs can be exacerbated by experimental conditions such as treatment with xenobiotics (eg, infectious morphological changes related to immunosuppressive therapy). This review and summary of research-relevant conditions and pathology in rhesus and cynomolgus macaques, baboons, African green monkeys, common marmosets, tamarins, and squirrel and owl monkeys aims to improve the interpretation and validity of NHP studies.

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.

Macacine Herpesvirus 1 in Long-Tailed Macaques, Malaysia, 2009-2011

Virus shedding by 39% of wild-caught macaques creates potential occupational risk for humans.

Macacine herpesvirus 1 (MaHV1; B virus) naturally infects macaques (Macaca spp.) and can cause fatal encephalitis in humans. In Peninsular Malaysia, wild macaques are abundant, and translocation is used to mitigate human–macaque conflict. Most adult macaques are infected with MaHV1, although the risk for transmission to persons who handle them during capture and translocation is unknown. We investigated MaHV1 shedding among 392 long-tailed macaques (M. fascicularis) after capture and translocation by the Department of Wildlife and National Parks in Peninsular Malaysia, during 2009–2011. For detection of MaHV1 DNA, PCR was performed on urogenital and oropharyngeal swab samples. Overall, 39% of macaques were shedding MaHV1 DNA; rates of DNA detection did not differ between sample types. This study demonstrates that MaHV1 was shed by a substantial proportion of macaques after capture and transport and suggests that persons handling macaques under these circumstances might be at risk for exposure to MaHV1.

A single viral gene determines lethal cross-species neurovirulence of baboon herpesvirus HVP2

Alpha-herpesviruses can produce more severe infections in non-natural host species than in their natural host. Isolates of the baboon alpha-herpesvirus Papiine herpesvirus 2 (HVP2) are either very neurovirulent in mice (subtype nv) or non-virulent (subtype ap), but no such difference is evident in the natural baboon host. Comparative genome sequencing was used to identify subtype-specific sequence differences (SSDs) between HVP2nv and HVP2ap isolates. Some genes were identified that despite exhibiting sequence variation among isolates did not have any SSDs, while other genes had comparatively high levels of SSDs. Construction of genomic recombinants between HVP2nv and HVP2ap isolates mapped the mouse neurovirulence determinant to within three genes. Construction of gene-specific recombinants demonstrated that the UL39 ORF is responsible for determining the lethal neurovirulence phenotype of HVP2 in mice. These results demonstrate that differences in a single viral gene can determine the severity of herpesvirus infection in a non-natural host species.

Reovirus-associated meningoencephalomyelitis in baboons

Baboon orthoreovirus (BRV) is associated with meningoencephalomyelitis (MEM) among captive baboons. Sporadic cases of suspected BRV-induced MEM have been observed at Southwest National Primate Research Center (SNPRC) for the past 20 years but could not be confirmed due to lack of diagnostic assays. An immunohistochemistry (IHC)-based assay using an antibody against BRV fusion-associated small transmembrane protein p15 and a conventional polymerase chain reaction (PCR)-based assay using primers specific for BRV were developed to detect BRV in archived tissues. Sixty-eight cases of suspected BRV-induced MEM from 1989 through 2010 were tested for BRV, alphavirus, and flavivirus by IHC. Fifty-nine of 68 cases (87%) were positive for BRV by immunohistochemistry; 1 tested positive for flavivirus (but was negative for West Nile virus and St Louis encephalitis virus by real-time PCR), and 1 virus isolation (VI) positive control tested negative for BRV. Sixteen cases (9 BRV-negative and 7 BRV-positive cases, by IHC), along with VI-positive and VI-negative controls, were tested by PCR for BRV. Three (of 9) IHC-negative cases tested positive, and 3 (of 7) IHC-positive cases tested negative by PCR for BRV. Both IHC and PCR assays tested 1 VI-positive control as negative (sensitivity: 75%). This study shows that most cases of viral MEM among baboons at SNPRC are associated with BRV infection, and the BRV should be considered a differential diagnosis for nonsuppurative MEM in baboons.

Type I IFN response to Papiine herpesvirus 2 (Herpesvirus papio 2; HVP2) determines neuropathogenicity in mice

Isolates of baboon alpha-herpesvirus Papiine herpesvirus 2 (HVP2) exhibit one of two distinct phenotypes in mice: extremely neurovirulent or apathogenic. Previous studies implicated the type I interferon (IFN) response as being a major factor in controlling infection by apathogenic isolates. To further investigate the possibility that the host IFN-beta response underlies the pathogenicity of the two HVP2 subtypes, the susceptibility of mice lacking the IFN-beta receptor (IFNAR(-/-)) to infection was examined. Apathogenic isolates of HVP2 (HVP2ap) replicated in IFNAR(-/-) primary mouse dermal fibroblast (PMDF) cultures as well as neurovirulent (HVP2nv) isolates. IFNAR(-/-) mice were also susceptible to lethal infection by HVP2ap isolates. Unlike Balb/c or parental 129 mice, LD(50) and ID(50) values for HVP2ap were the same in IFNAR(-/-) mice indicating that in these mice infection always progressed to death. HVP2ap replicated in the skin at the site of inoculation and invaded dorsal root ganglia as efficiently as HVP2nv in IFNAR(-/-) mice. Since the virion host shutoff (vhs) protein encoded by the UL41 gene of herpes simplex virus has been implicated in circumventing the host IFN-beta response and the phenotype of UL41 deletion mutants of HSV is very similar to that of HVP2ap isolates, the UL41 gene was deleted from HVP2nv (Delta 41) and replaced with the UL41 ORF from HVP2ap (Delta 41C). Like the parental HVP2nv virus, the Delta 41C recombinant replicated efficiently in Balb/c PMDFs and did not induce a strong IFN-beta response. The neuropathogenicity of the Delta 41C recombinant was also the same as the parental HVP2nv virus in Balb/c mice, indicating that the vhs protein does not underlie the different neuropathogenic phenotype of HVP2ap and HVP2nv. In contrast, the Delta 41 deletion virus induced a strong IFN-beta response but was still able to undergo multiple rounds of replication in PMDF cultures, albeit at a slower pace than the parental HVP2nv. This was reflected in vivo as the Delta 41 mutant had an LD(50) equivalent to that of the parental HVP2nv virus although the time to death was longer. These results indicate that while the vhs protein is involved in preventing and/or suppressing an IFN-beta response, it is not responsible for the ability of HVP2nv to overcome IFN-beta induced resistance of uninfected cells and does not underlie the divergent pathogenicity of the two HVP2 subtypes in mice.

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.

Primary mouse dermal fibroblast cell cultures as an in vitro model system for the differential pathogenicity of cross-species herpesvirus papio 2 infections

Infection of mice with herpesvirus papio 2 (HVP2) parallels zoonotic monkey B virus infections. A major benefit of the HVP2/mouse model is the existence of two HVP2 subtypes: HVP2nv rapidly invades and destroys the CNS while HVP2ap produces no clinical signs and mild histopathological lesions. However, in the natural baboon host, no difference in pathogenicity of HVP2 subtypes is evident. Primary dermal fibroblast cells were evaluated as a model system for defining virus-host interactions that influence the outcome of a cross-species infection. No differences in plaque formation or virus replication were observed between HVP2 subtypes in primary baboon dermal fibroblast cultures. In contrast, when primary mouse dermal fibroblasts (PMDF) were infected, HVP2nv replicated to higher titers and was more efficient at shutting down host-cell protein synthesis compared to HVP2ap. HVP2ap-infected PMDF cells produced more IFN-beta compared to HVP2nv, and IFN-beta pretreatment of PMDF cultures inhibited HVP2ap replication but did not affect HVP2nv. The differential pathogenicity of HVP2 subtypes in mice and the lack of such differences in the natural baboon host are recapitulated in the primary dermal fibroblast cell culture system. This model may prove useful in examining early, local, host responses that influence the outcome of cross-species infections.

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.

Neuropathogenesis of herpesvirus papio 2 in mice parallels infection with Cercopithecine herpesvirus 1 (B virus) in humans

Cercopithecine herpesvirus 1 (monkey B virus; BV) produces extremely severe and usually fatal infections when transmitted from macaque monkeys to humans. Cercopithecine herpesvirus 16 (herpesvirus papio 2; HVP2) is very closely related to BV, yet cases of human HVP2 infection are unknown. However, following intramuscular inoculation of mice, HVP2 rapidly invades the peripheral nervous system and ascends the central nervous system (CNS) resulting in death, very much like human BV infections. In this study, the neurovirulence of HVP2 in mice was further evaluated as a potential model system for human BV infections. HVP2 was consistently neurovirulent when administered by epidermal scarification, intracranial inoculation and an eye splash. Quantitative real-time PCR, histopathology and immunohistochemistry were used to follow the temporal spread of virus following skin scarification and to compare the pathogenesis of neurovirulent and apathogenic isolates of HVP2. Apathogenic isolates were found to be capable of reaching the CNS but were extremely inefficient at replicating within the CNS. It is concluded that neurovirulent strains of HVP2 exhibit a pathogenesis in mice that parallels that observed in human BV infections and that this model system may prove useful in dissecting the viral determinants underlying the extreme severity of zoonotic BV infections.

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

We have obtained the complete sequence of the herpesvirus simian agent 8 (SA8; cercopithecine herpesvirus 2) a baboon simplexvirus closely related to the monkey B virus and herpes simplex virus types 1 and 2. The genome of SA8 is 150,715 bp long, with an overall G/C content of 76%, the highest among the simplexviruses sequenced so far. The sequencing has confirmed that the genomic arrangement of SA8 is similar to that of other simplexviruses: unique long and unique short regions bordered by two sets of inverted repeats. All genes identified in SA8 are homologous and collinear with those of the monkey B virus, including the lack of the RL1 open reading frame, a gene responsible for neurovirulence in human herpes simplex viruses. This latter finding supports the hypothesis that a different pathogenetic mechanism may have developed in human simplexviruses, after their divergence from monkey simplexviruses.

Use of Herpesvirus Papio 2 as an Alternative Antigen in Immunoblotting Assay for B Virus Diagnosis

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.

Pathogenicity of different baboon herpesvirus papio 2 isolates is characterized by either extreme neurovirulence or complete apathogenicity

In comparisons of the pathogenicity of simian alphaherpesviruses in mice, two isolates of the baboon virus HVP2 were nearly as lethal as monkey B virus, a biological safety level 4 agent (J. W. Ritchey, K. A. Ealey, M. Payton, and R. Eberle, J. Comp. Pathol. 127:150-161, 2002). To confirm these results, mice were inoculated intramuscularly with 10(5) PFU of HVP2 isolates obtained from different baboon subspecies and primate centers. Some of the HVP2 isolates (6 of 13) caused paralysis and death in the mice, while 7 of 13 HVP2 isolates produced no clinical signs of disease. The apathogenic HVP2 isolates (HVP2ap) induced only low levels of serum antiviral immunoglobulin G relative to levels observed in sera from mice infected with the neurovirulent isolates of HVP2 (HVP2nv). Histological examination of tissues from mice inoculated with HVP2nv isolates showed extensive neural tissue destruction, while mice infected with HVP2ap isolates showed no lesions. Tissue samples collected at 48-h intervals postinfection suggested that HVP2ap isolates failed to replicate at the site of inoculation. There was no significant difference in the in vitro replication, plaque size, or cytopathic effect morphology of HVP2ap versus HVP2nv isolates. While HVP2 isolates replicated better in Vero monkey kidney cells than in murine L cells, plaquing efficiency of individual isolates did not correlate with the dichotomous pathogenic properties seen in mice. Phylogenetic analyses of both coding and intergenic regions (US4-6) of the HVP2 genome separated isolates into two distinct clades that correlated with the two in vivo virulence phenotypes. Taken together, these results demonstrate that two subtypes of HVP2 exist that are very closely related but differ dramatically in their ability to cause disease in a murine model.

The genome of herpesvirus papio 2 is closely related to the genomes of human herpes simplex viruses

Infection of baboons (Papio species) with herpesvirus papio 2 (HVP-2) produces a disease that is clinically similar to herpes simplex virus (HSV-1 and HSV-2) infection of humans. The development of a primate model of simplexvirus infection based on HVP-2 would provide a powerful resource to study virus biology and test vaccine strategies. In order to characterize the molecular biology of HVP-2 and justify further development of this model system we have constructed a physical map of the HVP-2 genome. The results of these studies have identified the presence of 26 reading frames that closely resemble HSV homologues. Furthermore, the HVP-2 genome shares a collinear arrangement with the genome of HSV. These studies further validate the development of the HVP-2 model as a surrogate system to study the biology of HSV infections.

B-virus (Cercopithecine herpesvirus 1) infection in humans and macaques: potential for zoonotic disease

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.

Herpesvirus papio 2 encodes a virion host shutoff function

Infection of baboons with herpesvirus papio 2 (HVP-2) produces a disease that is similar to human infection with herpes simplex viruses (HSV). Molecular characterization of HVP-2 has demonstrated that the virion contains a factor which rapidly shuts off host cell protein synthesis after infection. Reduction of host cell protein synthesis occurs in parallel with the degradation of mRNA species. A homolog of the HSV virion host shutoff (vhs) gene was identified by Southern and DNA sequence analysis. The sequence of the HVP-2 vhs gene homolog had greater than 70% identity with the vhs genes of HSV 1 and 2. Disruption of the HVP-2 vhs open reading frame diminished the ability of the virus to shut off protein synthesis and degrade cellular mRNA, indicating that this gene was responsible for the vhs activity. The HVP-2 model system provides the opportunity to study the biological role of vhs in the context of a natural primate host. Further development of this system will provide a platform for proof-of-concept studies that will test the efficacy of vaccines that utilize vhs-deficient viruses.

Comparative pathology of infections with baboon and African green monkey alpha-herpesviruses in mice

The comparative pathology of Herpesvirus papio 2 (HVP2) of baboons and SA8 virus of African green monkeys relative to that of herpes simplex virus (HSV1) of man was investigated in young adult mice inoculated intramuscularly and observed for 21 days. The 50% infectious dose (ID(50)) for HVP2 was approximately 10(2.0) plaque-forming units (PFU), while the ID(50) for HSV1 and SA8 was 10(2.5) and 10(3.8), respectively. There were marked differences in the ability of these three viruses to invade the central nervous system (CNS) and cause clinical neurological disease. HSV1 produced neurological signs in a few animals given 10(6)PFU, but SA8 did not. In contrast, HVP2 readily invaded the CNS and produced fatal disease with doses as low as 10(2)PFU. Two isolates of HVP2 tested had a 50% CNS disease dose (CNSD(50)) of 10(2.5) and 10(3.0)PFU and an LD(50) of 10(3.8) and 10(4.3)PFU, respectively. Histopathological examination of tissue from HVP2-infected mice revealed severe lesions of inflammation and necrosis in the central, peripheral and autonomic nervous systems, as well as of other tissues including skin, adrenal glands and the gastrointestinal tract. Viral antigens were detected immunohistochemically in lesions. This study showed that while both HVP2 and SA8 could infect mice, there were marked differences in the ability of these two closely related viruses to cause clinical disease and CNS lesions. This murine model may prove useful in the investigation of viral or host determinants responsible for the varying neurovirulence of these simian alpha-herpesviruses.

Efficacy of a B virus gD DNA vaccine for induction of humoral and cellular immune responses in Japanese macaques

It is desirable to prevent dissemination of B virus (BV) in macaque colonies because transmission of BV to humans causes deadly encephalomyelitis. Vaccination of monkeys is one method that could confine spread of BV within macaque colonies. Availability of a BV DNA vaccine for use in macaques would eliminate the risk of working with infectious BV. Toward this end, we constructed a plasmid expressing the BV glycoprotein D (gD). Immunogenicity of this construct as a DNA vaccine was assessed in adult Japanese macaques by four intracutaneous injections at a dose of 500 microg per head. Results of enzyme-linked immunosorbent assay (ELISA) using a recombinant herpes simplex virus type 1 (HSV1) gD, a homologue of BV gD, showed that significant levels of antibody was induced in all vaccinated animals following each booster injection. Western blot of sera from vaccinated macaques confirmed the specific recognition of authentic BV gD. Immune sera were also demonstrated to contain neutralizing activity against infectious BV. Weak lymphoproliferative responses were also observed in vaccinated macaques using recombinant HSV1 gD as a stimulating antigen and flow cytometry analysis of one individual revealed the presence of HSV1 gD-responsive effector T cells. Thus, the BV gD DNA vaccine was demonstrated to induce both humoral and cellular immune responses in macaques which recognized BV gD.

Serological evidence of alpha herpesvirus infection in sooty mangabeys

Contact between sooty mangabeys (SMs) and a pigtailed macaque prompted the serological screening of SMs for evidence of infection with B virus. Serological tests detected SM antibodies that reacted with B virus polypeptides. Additional testing was performed with sera from SMs with no previous contact with macaques. Results from these tests indicated that 56% (33/59) of the SMs had antibodies that reacted with B virus and SA8. SM antibodies also reacted with herpesvirus papio 2 and to a lesser extent with human alpha herpesviruses (HSV-1 and HSV-2). There was an age-related increase in the presence of these antibodies in SMs that was consistent with the serological pattern of reactivity observed in other nonhuman primate species infected with alpha herpesviruses. These data suggest that SMs may be a host for a herpesvirus that is antigenically similar to those viruses present in other Old World nonhuman primates.

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.

Development of a competitive ELISA for detection of primates infected with monkey B virus (Herpesvirus simiae)

Two competitive ELISAs (C-ELISAs) are described that allow detection of antibodies against monkey B virus (BV, Cercopithecine herpesvirus 1). The assays utilize monoclonal antibodies (MABs) directed against the BV glycoprotein B (gB). Two of these MABs specifically recognize BV gB while a third MAB also reacts with the gB homologues of other primate alpha-herpesviruses (herpes simplexvirus-1, HSV-1: HSV-2; simian agent-8, SA8; and Herpesvirus papio-2, HVP2). A C-ELISA using the single cross-reactive MAB 3E8 allowed detection of host antibodies against HSV-1, HSV-2, SA8, HVP2 or BV, thus proving to be a sensitive assay for the detection of infection by any of these primate alpha-herpesviruses. The C-ELISA using BV-specific MABs was less sensitive but did allow some discrimination between infection by BV versus other alpha-herpesviruses. It was also shown that a C-ELISA using HVP2 as antigen and the cross-reactive MAB 3E8 was as sensitive for detection of BV antibody in macaque sera as an assay employing BV antigen. This test format allows detection of BV-infected primates without the biohazards associated with preparation and use of BV antigen.

Protection against herpes B virus infection in rabbits with a recombinant vaccinia virus expressing glycoprotein D

Herpes B virus infects naturally monkeys of the macaque genus in whom it can cause recurrent oral and genital lesions. However, when the virus infects humans it causes a neurological illness with a high case fatality rate. Successful treatment is possible but this depends on diagnosis prior to the onset of respiratory arrest, and fatalities over the last 10 years have been the result of late or no diagnostic data on which to base anti-viral intervention. An effective vaccine would be an ideal way to combat the risk of herpes B virus disease in humans working with potentially infected monkeys or their tissues. A recombinant vaccinia virus expressing herpes B virus glycoprotein D (gD) was constructed and rabbits inoculated with the chimeric virus were tested for immunoglobulin responses to herpes B virus by virus neutralisation, ELISA and Western blot analyses. Anti-gD humoral responses were detected in all vaccinated animals by ELISA and Western blot but neutralising antibody was not detected prior to challenge with herpes B virus. Non-vaccinated rabbits died within 8 days of challenge while 10/11 vaccinated animals were protected against herpes B virus disease. No antibodies to herpes B virus proteins other than gD were detectable in surviving animals, suggesting minimal herpes B virus replication post challenge. Autopsies were carried out on 4/10 rabbits which had remained healthy at 31 days post challenge and the dorsal root ganglia adjacent to the inoculation site were removed. Attempts to detect herpes B virus DNA by PCR followed by hybridisation proved negative suggesting protection against latent herpes B virus infection.

Normal Immunologic Response to a Neoantigen, Bacteriophage ΦX-174, in Baboons With Long-Term Lymphohematopoietic Reconstitution From Highly Purified CD34+ Lin− Allogeneic Marrow Cells

The CD34 antigen is thought to be expressed by hematopoietic stem cells in adult humans and nonhuman primates. We present data that baboons transplanted with highly purified allogeneic CD34+ marrow cells devoid of detectable mature and immature T and B lymphocytes and myeloid cells, isolated from sex-mismatched mixed lymphocyte culture (MLC) nonreactive siblings, have maintained stable lymphohematopoietic engraftment with donor cells for greater than 4.9, greater than 6.0, and 5.0 years. Cytogenetic analysis of unfractionated marrow and peripheral blood cells at multiple time points after transplantation show virtually all donor cells in two animals and stable mixed chimerism in the third. We used polymerase chain reaction to show that colony-forming unit–granulocyte-macrophage, burst-forming unit-erythroid, and high proliferative potential colony-forming cells (HPP-CFC) were virtually all of donor origin in two animals and present at lower levels in the stable mixed chimera. CD20+ B-lymphoblastoid cell lines derived by Herpesvirus Papio transformation of peripheral blood cells were virtually all donor in two animals and 50% donor in the mixed chimera. CD4+ and CD8+ T cells and neutrophils purified from the peripheral blood of the two female animals also were all donor-derived. To assess immunologic function after transplantation, we immunized the three long-term chimeric animals and two normal control animals with bacteriophage ΦX-174, a neoantigen that requires the interaction of antigen-presenting cells, T lymphocytes, and B lymphocytes to mount a normal antibody response. Experimental and control animals, when immunized with bacteriophage, had similar serum Ig levels. The experimental and control animals generated similar titers of antibacteriophage antibodies after primary and secondary immunizations with evidence of amplification and class switching. These findings further support the hypothesis that the CD34+ antigen is expressed on hematopoietic stem cells that can mediate stable long-term lymphohematopoiesis in vivo and, importantly, that normal immunologic function can be reconstituted in vivo after transplantation of the highly purified CD34+ Lin− cells alone.

Normal Immunologic Response to a Neoantigen, Bacteriophage ΦX-174, in Baboons With Long-Term Lymphohematopoietic Reconstitution From Highly Purified CD34+ Lin− Allogeneic Marrow Cells

The CD34 antigen is thought to be expressed by hematopoietic stem cells in adult humans and nonhuman primates. We present data that baboons transplanted with highly purified allogeneic CD34+ marrow cells devoid of detectable mature and immature T and B lymphocytes and myeloid cells, isolated from sex-mismatched mixed lymphocyte culture (MLC) nonreactive siblings, have maintained stable lymphohematopoietic engraftment with donor cells for greater than 4.9, greater than 6.0, and 5.0 years. Cytogenetic analysis of unfractionated marrow and peripheral blood cells at multiple time points after transplantation show virtually all donor cells in two animals and stable mixed chimerism in the third. We used polymerase chain reaction to show that colony-forming unit–granulocyte-macrophage, burst-forming unit-erythroid, and high proliferative potential colony-forming cells (HPP-CFC) were virtually all of donor origin in two animals and present at lower levels in the stable mixed chimera. CD20+ B-lymphoblastoid cell lines derived by Herpesvirus Papio transformation of peripheral blood cells were virtually all donor in two animals and 50% donor in the mixed chimera. CD4+ and CD8+ T cells and neutrophils purified from the peripheral blood of the two female animals also were all donor-derived. To assess immunologic function after transplantation, we immunized the three long-term chimeric animals and two normal control animals with bacteriophage ΦX-174, a neoantigen that requires the interaction of antigen-presenting cells, T lymphocytes, and B lymphocytes to mount a normal antibody response. Experimental and control animals, when immunized with bacteriophage, had similar serum Ig levels. The experimental and control animals generated similar titers of antibacteriophage antibodies after primary and secondary immunizations with evidence of amplification and class switching. These findings further support the hypothesis that the CD34+ antigen is expressed on hematopoietic stem cells that can mediate stable long-term lymphohematopoiesis in vivo and, importantly, that normal immunologic function can be reconstituted in vivo after transplantation of the highly purified CD34+ Lin− cells alone.

Detection and differentiation of primate alpha-herpesviruses by PCR

A rapid method for detection and differentiation of 5 primate alpha-herpesviruses (human herpes simplex virus types 1 and 2 [HSV1, HSV2], green monkey simian agent 8, baboon herpesvirus 2 [HVP2], and macaque B virus [BV]) was developed utilizing the polymerase chain reaction (PCR). PCR primers were located in conserved regions of the gene encoding the glycoprotein B, which flanks an intervening region that is highly divergent among the 5 viruses. Amplified PCR products from the 5 viruses were readily differentiated by their unique restriction enzyme digestion patterns. No variation in digestion patterns was noted among strains of HSV1, HSV2, or HVP2. One clinical isolate of BV exhibited variation in a single restriction site, but its overall restriction pattern remained typical of BV. This method (PCR/RFLP) allowed the presence of herpesvirus DNA in clinical swabs from primates to be readily detected and the virus unambiguously identified.