Leukemic histiocytic sarcoma in a captive common squirrel monkey (Saimiri sciureus) with Saimiriine Gammaherpesvirus 2 (Rhadinovirus), Saimiri sciureus lymphocryptovirus 2 (Lymphocryptovirus) and Squirrel monkey retrovirus (β-Retrovirus) coinfection

Hematopoietic neoplasia other than lymphoma and leukemia is uncommon among non-human primates. Herein, we provide the first evidence of occurrence of leukemic histiocytic sarcoma in a captive common squirrel monkey with Saimiriine Gammaherpesvirus 2 (Rhadinovirus), Saimiri sciureus lymphocryptovirus 2 (Lymphocryptovirus), and Squirrel monkey retrovirus (β-Retrovirus) coinfection.

Macaca arctoides gammaherpesvirus 1 (strain herpesvirus Macaca arctoides): virus sequence, phylogeny and characterisation of virus-transformed macaque and rabbit cell lines

Herpesvirus Macaca arctoides (HVMA) has the propensity to transform macaque lymphocytes to lymphoblastoid cells (MAL-1). Inoculation of rabbits with cell-free virus-containing supernatant resulted in the development of malignant lymphomas and allowed isolation of immortalised HVMA-transformed rabbit lymphocytes (HTRL). In this study, the HVMA genome sequence (approx. 167 kbp), its organisation, and novel aspects of virus latency are presented. Ninety-one open reading frames were identified, of which 86 were non-repetitive. HVMA was identified as a Lymphocryptovirus closely related to Epstein-Barr virus, suggesting the designation as 'Macaca arctoides gammaherpesvirus 1' (MarcGHV-1). In situ lysis gel and Southern blot hybridisation experiments revealed that the MAL-1 cell line contains episomal and linear DNA, whereas episomal DNA is predominantly present in HTRL. Integration of viral DNA into macaque and rabbit host cell genomes was demonstrated by fluorescence in situ hybridisation on chromosomal preparations. Analysis of next-generation sequencing data confirmed this finding. Approximately 400 read pairs represent the overlap between macaque and MarcGHV-1 DNA. Both, MAL-1 cells and HTRL show characteristics of a polyclonal tumour with B- and T-lymphocyte markers. Based on analysis of viral gene expression and immunohistochemistry, the persistence of MarcGHV-1 in MAL-1 cells resemble the latency type III, whereas the expression pattern observed in HTRL was more comparable with latency type II. There was no evidence of the presence of STLV-1 proviral DNA in MAL-1 and HTRL. Due to the similarity to EBV-mediated cell transformation, MarcGHV-1 expands the available in vitro models by simian and rabbit cell lines.

Posttransplant Lymphoproliferative Disorders in Neuronal Xenotransplanted Macaques

Posttransplant lymphoproliferative disorders (PTLDs) are a heterogeneous group of lymphoid proliferations that occur in the setting of depressed T-cell function due to immunosuppressive therapy used following solid organ transplantation, hematopoietic stem cell transplantation, and also xenotransplantation. In the present study, 28 immunosuppressed parkinsonian Macaca fascicularis were intracerebrally injected with wild-type or CTLA4-Ig transgenic porcine xenografts to identify a suitable strategy to enable long-term cell survival, maturation, and differentiation. Nine of 28 (32%) immunosuppressed primates developed masses compatible with PTLD, located mainly in the gastrointestinal tract and/or nasal cavity. The masses were classified as monomorphic PTLD according to the World Health Organization classification. Immunohistochemistry and polymerase chain reaction (PCR) analyses revealed that the PTLDs were associated with macaca lymphocryptovirus as confirmed by double-labeling immunohistochemistry for CD20 and Epstein-Barr nuclear antigen 2 (EBNA-2), where the viral protein was located within the CD20+ neoplastic B cells. In sera from 3 distinct phases of the experimental life of the primates, testing by quantitative PCR revealed a progression of the viral load that paralleled the PTLD progression and no evidence of zoonotic transmission of porcine lymphotropic herpesvirus through xenoneuronal grafts. These data suggest that monitoring the variation of macaca lymphocryptovirus DNA in primates could be used as a possible early diagnostic tool for PTLD progression, allowing preemptive treatment such as immunosuppression therapy reduction.

Non-human Primate Lymphocryptoviruses: Past, Present, and Future

Epstein-Barr virus (EBV) orthologues from non-human primates (NHPs) have been studied for nearly as long as EBV itself. Cross-reactive sera and DNA hybridization studies provided the first glimpses of the closely related herpesviruses that belonged to the same gamma-1 herpesvirus, or lymphocryptovirus, genus, as EBV. Over the years, detailed molecular and sequence analyses of LCVs that infect humans and other NHPs revealed similar colinear genome structures and homologous viral proteins expressed during latent and lytic infection. Despite these similarities, experimental infection of NHPs with EBV did not result in acute symptoms or persistent infection as observed in humans, suggesting some degree of host species restriction. Genome sequencing and a molecular clone of an LCV isolate from naturally infected rhesus macaques combined with domestic colonies of LCV-naïve rhesus macaques have opened the door to a unique experimental animal model that accurately reproduces the normal transmission, acute viremia, lifelong persistence, and immune responses found in EBV-infected humans. This chapter will summarize the advances made over the last 50 years in our understanding of LCVs that naturally infect both Old and New World NHPs, the recent, groundbreaking developments in the use of rhesus macaques as an animal model for EBV infection, and how NHP LCVs and the rhLCV animal model can advance future EBV research and the development of an EBV vaccine.

The genomic sequence of lymphocryptovirus from cynomolgus macaque

Lymphocryptoviruses such as Epstein-Barr virus (EBV) cause persistent infections in human and non-human primates, and suppression of the immune system can increase the risk of lymphocryptovirus (LCV)-associated tumor development in both human and non-human primates. To enable LCV infection as a non-clinical model to study effects of therapeutics on EBV immunity, we determined the genomic DNA sequence of the LCV from cynomolgus macaque, a species commonly used for non-clinical testing. Comparison to rhesus macaque LCV and human EBV sequences indicates that LCV from the cynomolgus macaque has the same genomic arrangement and a high degree of similarity in most genes, especially with rhesus macaque LCV. Genes showing lower similarity were those encoding proteins involved in latency and/or tumor promotion or immune evasion. The genomic sequence of LCV from cynomolgus macaque should aid the development of non-clinical tools for identifying therapeutics that impact LCV immunity and carry potential lymphoma risk.

Quantitative PCR assays reveal high prevalence of lymphocryptovirus as well as lytic phase gene expression in peripheral blood cells of cynomolgus macaques

Lymphocryptoviruses such as Epstein-Barr virus (EBV) are important pathogens in both human and non-human primates, particularly during immunosuppression. Immunomodulatory molecules that may suppress antiviral immunity are commonly tested in the cynomolgus macaque. To enable the study of lymphocryptovirus (LCV) in this non-clinical model, PCR-based assays were developed to measure LCV viral load, as well as transcripts for the lytic phase LCV gene, BALF-2. Results from studies employing these assays showed that LCV genome was detected in the oropharyngeal epithelium of all cynomolgus monkeys tested, and the majority had viral genome in peripheral blood mononuclear cells (PBMCs). The results also revealed LCV lytic phase gene expression not only in the oropharynx of most monkeys, but also in PBMCs of approximately one half of monkeys tested. This unexpected finding suggests that initiation of the lytic gene expression cascade occurs often in the peripheral blood cells of healthy monkeys.

[Genetic diversity and evolution of primate Gammaherpesvirinae]

The Gammaherpesvirinae sub-family is divided into two genera, the Lymphocryptovirus and the Rhadinovirus. Until recently, Epstein-Barr virus (EBV), the human prototype of the Lymphocryptovirus genus, and simian homologues have only been detected in humans and Old World non-human primates. In other respects, the Rhadinovirus genus was only represented by Herpesvirus saimiri and Herpesvirus ateles of New World monkey species. Therefore, the general thinking at that time was that the separation of the continents resulted in drastic changes in the Gammaherpesvirinae evolution. The discovery of the human herpesvirus 8 (HHV8), belonging to the Rhadinovirus genus, followed by the identification of CalHV3 (Callitrichine herpesvirus 3) a lymphocryptovirus of marmoset, challenged this old paradigm. The recent description of numerous viruses belonging to the Gammaherpesvirinae subfamily from different Old and NewWorld primate species let to develop and to support co-speciational evolution hypotheses of these viruses and their hosts. This review focuses on our current knowledge of the genetic diversity and evolution of primate Gammaherpesvirinae.