Malignant lymphoma induction in rabbits by intravenous inoculation of Epstein-Barr-virus-related herpesvirus from HTLV-II-transformed cynomolgus leukocyte cell line (Si-IIA)

Genetic diversity and molecular evolution of human and non-human primate Gammaherpesvirinae

The Gammaherpesvirinae sub-family is divided into two genera: Lymphocryptovirus and Rhadinovirus. Until the middle of the 1990s, the Rhadinovirus genus was only represented by Herpesvirus saimiri and Herpesvirus ateles, which infect New World monkey species. Until the year 2000, Epstein-Barr virus (EBV), the human prototype of the Lymphocryptovirus, and simian homologues had only been detected in humans and Old World non-human primates. It was thought, therefore, that the separation of the continents had resulted in drastic changes in Gammaherpesvirinae evolution. The discovery of Kaposi's sarcoma-associated herpesvirus in humans, belonging to the Rhadinovirus, followed by the identification of CalHV3 (Callitrichine herpesvirus 3), a lymphocryptovirus of the marmoset, challenged this paradigm. The description of numerous viruses belonging to this sub-family from various Old and New World primate species enabled a cospeciation hypothesis for these viruses and their hosts to be developed. This review focuses on the current knowledge of primate Gammaherpesvirinae genetic diversity and molecular evolution. We discuss the various theories based on current genetic data regarding evolutionary relationships between lymphocryptoviruses of Old World primates, the use of these data as a tool to study evolutionary relationships between New World monkey species, and the possible existence of a ninth human herpesvirus belonging to the Rhadinovirus genus.

Rabbit model for human EBV-associated hemophagocytic syndrome (HPS): sequential autopsy analysis and characterization of IL-2-dependent cell lines established from herpesvirus papio-induced fatal rabbit lymphoproliferative diseases with HPS

Epstein-Barr virus-associated hemophagocytic syndrome (EBV-AHS) is often associated with fatal infectious mononucleosis or T-cell lymphoproliferative diseases (LPD). To elucidate the true nature of fatal LPD observed in Herpesvirus papio (HVP)-induced rabbit hemophagocytosis, reactive or neoplastic, we analyzed sequential development of HVP-induced rabbit LPD and their cell lines. All of the seven Japanese White rabbits inoculated intravenously with HVP died of fatal LPD 18 to 27 days after inoculation. LPD was also accompanied by hemophagocytic syndrome (HPS) in five of these seven rabbits. Sequential autopsy revealed splenomegaly and swollen lymph nodes, often accompanied by bleeding, which developed in the last week. Atypical lymphoid cells infiltrated many organs with a "starry sky" pattern, frequently involving the spleen, lymph nodes, and liver. HVP-small RNA-1 expression in these lymphoid cells was clearly demonstrated by a newly developed in situ hybridization (ISH) system. HVP-ISH of immunomagnetically purified lymphoid cells from spleen or lymph nodes revealed HVP-EBER1+ cells in each CD4+, CD8+, or CD79a+ fraction. Hemophagocytic histiocytosis was observed in the lymph nodes, spleen, bone marrow, and thymus. HVP-DNA was detected in the tissues and peripheral blood from the infected rabbits by PCR or Southern blot analysis. Clonality analysis of HVP-induced LPD by Southern blotting with TCR gene probe revealed polyclonal bands, suggesting polyclonal proliferation. Six IL-2-dependent rabbit T-cell lines were established from transplanted scid mouse tumors from LPD. These showed latency type I/II HVP infection and had normal karyotypes except for one line, and three of them showed tumorigenicity in nude mice. These data suggest that HVP-induced fatal LPD in rabbits is reactive polyclonally in nature.

Characterization of the Cyno-EBV LMP1 homologue and comparison with LMP1s of EBV and other EBV-like viruses

EBV latent membrane protein 1 (LMP1) is essential for EBV-mediated transformation and has been associated with several cases of malignancies. EBV-like viruses in Cynomolgus monkeys (Macaca fascicularis) have been associated with high lymphoma rates in immunosuppressed monkeys. In the study, the entire coding region of the Cyno-EBV LMP1 gene was cloned, sequenced and expressed in human embryonic kidney (HEK) cells 293. The Cyno-EBV LMP1 homologue sequence predicted a 588 amino acid (a.a.) protein with a short 19 a.a. N-terminus, six transmembrane domains and a long carboxy tail of 404 a.a. The protein contained a series of seven 9 a.a.-tandem repeats and two 20 a.a.-repeats, which harbored two potential TRAF binding motifs, PxQxT/S. These repeats shared no homology with the repeats in any other LMP1. However, the proline-rich sequence GPxxPx(6) found within the 11 a.a.-repeats of EBV LMP1 was conserved in Cyno-EBV carboxy tail and contained two consensus JAK/STAT sequences PxxPxP. A cluster of eight histidine residues was found in proximity to the last transmembrane domain of Cyno-EBV LMP1 and was exploited as a natural protein tag in expression studies. Western blot analysis revealed a major polypeptide of 110 kDa. Comparative functional studies showed that Cyno-EBV LMP1 expressed in HEK 293 cells shares the same ability as EBV LMP1 to induce NFkappaB driven CAT activity.

Characterization of an Epstein-Barr virus-related gammaherpesvirus from common marmoset (Callithrix jacchus)

A gammaherpesvirus related to Epstein-Barr virus (EBV; Human herpesvirus 4) infects otherwise healthy common marmosets (Callithrix jacchus). Long-term culture of common marmoset peripheral blood lymphocytes resulted in outgrowth of spontaneously immortalized lymphoblastoid cell lines, primarily of B cell lineage. Electron microscopy of cells and supernatants showed herpesvirus particles. There were high rates of serological cross-reactivity to other herpesviruses (68-86%), but with very low geometric mean antibody titres [1:12 to human herpesvirus 6 and 1:14 to Herpesvirus papio (Cercopithecine herpesvirus 12)]. Sequence analysis of the conserved herpesvirus DNA polymerase gene showed that the virus is a member of the lymphocryptovirus subgroup and is most closely related to a lymphocryptovirus from rhesus macaques and is closely related to EBV and Herpesvirus papio. High seroprevalence (79%, with geometric mean antibody titre of 1:110) among 28 common marmosets from two geographically distinct colonies indicated that the virus is likely present in many common marmosets in captivity. A New World primate harbouring a lymphocryptovirus suggests that this subgroup arose much earlier than previously thought.

Reduction of hematopoietic cell-specific tyrosine phosphatase SHP-1 gene expression in natural killer cell lymphoma and various types of lymphomas/leukemias : combination analysis with cDNA expression array and tissue microarray

To investigate the lymphomagenesis of NK/T lymphoma, we comprehensively and systematically analyzed the expression pattern of the human NK/T cell line (NK-YS) genome by cDNA expression array and tissue microarray. We detected significant changes in the gene expression of NK-YS cell line: an increase in 18 and a decrease in 20 genes compared to normal NK cells or peripheral blood mononuclear cells. Among these genes, we found a strong decrease in hematopoietic cell specific protein-tyrosine-phosphatase SH-PTP1 (SHP1) mRNA by cDNA expression array and reverse transcriptase-polymerase chain reaction. Further analysis with standard immunohistochemistry and tissue microarray, which used 207 paraffin-embedded specimens of various kinds of malignant lymphomas, showed that 100% of NK/T lymphoma specimens and more than 95% of various types of malignant lymphoma were negative for SHP1 protein expression. On the other hand, SHP1 protein was strongly expressed in the mantle zone and interfollicular zone lymphocytes in reactive lymphoid hyperplasia specimens. In addition, various kinds of hematopoietic cell lines, particularly the highly aggressive lymphoma/leukemia lines, lacked SHP1 expression in vitro, suggesting that loss of SHP1 expression may be related to not only malignant transformation, but also tumor cell aggressiveness. SHP1 expression could not be induced in either of two NK/T cell lines by phorbol ester, suggesting that genetic impairment or modification with methylation of SHP1 DNA could be one of the critical events in the pathogenesis of NK/T lymphoma. This evidence strongly suggests that loss of SHP1 gene expression plays an important role in multistep tumorigenesis, possibly as an anti-oncogene in the wide range of lymphomas/leukemias as well as NK/T lymphomas.

HV(MNE), a novel lymphocryptovirus related to Epstein-Barr virus, induces lymphoma in New Zealand White rabbits

HV(MNE) is a novel Epstein-Barr (EBV)-like virus isolated from a Macaca nemestrina with CD8(+) T-cell mycosis fungoides-cutaneous T-cell lymphoma. Here it is demonstrated that intravenous inoculation of irradiated HV(MNE)-infected T cells or cell-free virus from the J94356(PBMC) cell line in New Zealand White rabbits results in seroconversion to the viral capsid antigen (VCA) of EBV; all animals that seroconverted to VCA developed malignant lymphoma within months of inoculation. In contrast, control rabbits, inoculated with heat-inactivated culture supernatants from the same cell line, failed to seroconvert to VCA and did not develop disease. Disseminated lymphoma cells of mixed origin were detected in most vital organs, including the spleen, liver, lungs, kidneys, and heart of the affected rabbits. Neoplastic infiltrates were also observed in lymph nodes, thymus, skin, and subcutaneous tissues. HV(MNE) DNA and EBV-like RNA expression was demonstrated in the lymphomatous organs and in 2 transformed T-cell lines, one established from the lymph node and the other from the blood of the 2 lymphomatous animals. Analysis of one of these T-cell lines demonstrated the persistence of HV(MNE) DNA, expression of an LMP1-like protein, and acquisition of interleukin-2 independence, and constitutive activation of the Jak/STAT pathway. Thus, HV(MNE) in rabbits provides a valuable animal model for human T-cell lymphoma whereby genetic determinants for T-cell transformation by this EBV-like animal virus can be studied.

An animal model for human EBV-associated hemophagocytic syndrome: herpesvirus papio frequently induces fatal lymphoproliferative disorders with hemophagocytic syndrome in rabbits

Epstein-Barr virus-associated hemophagocytic syndrome (EBV-AHS) is often associated with fatal infectious mononucleosis. However, the animal model for EBV-AHS has not been developed. We reported the first animal model for EBV-AHS using rabbits infected with EBV-related herpesvirus of baboon (HVP). Eleven of 13 (85%) rabbits inoculated intravenously with HVP-producing cells developed fatal lymphoproliferative disorders (LPD) between 22 and 105 days after inoculation. LPD was also accompanied by hemophagocytic syndrome (HPS) in nine of these 11 rabbits. The peroral spray of cell-free HVP induced the virus infection with increased anti-EBV-viral capsid antigen-IgG titers in three of five rabbits, and two of these three infected rabbits died of LPD with HPS. Autopsy revealed hepatosplenomegaly and swollen lymph nodes. Atypical lymphoid T cells expressing EBV-encoded small RNA-1 infiltrated diffusely in many organs, frequently involving the lymph nodes, spleen, and liver. Hemophagocytic histiocytosis was observed in the lymph nodes, spleen, bone marrow, and thymus. HVP-DNA was detected in the tissues and peripheral blood from the infected rabbits by polymerase chain reaction or Southern blot analysis. Reverse transcriptase-polymerase chain reaction revealed both HVP-EBNA1 and HVP-EBNA2 transcripts, suggesting latency type III infection. These data indicate that the high rate of rabbit LPD with HPS induction is caused by HVP. This system is useful for studying the pathogenesis, prevention, and treatment of human EBV-AHS.

An animal model for Epstein-Barr virus (EBV)-associated lymphomagenesis in the human: malignant lymphoma induction of rabbits by EBV-related herpesvirus from cynomolgus

It is very important to develop and analyze animal models of Epstein-Barr virus (EBV)-associated tumors in the human. However, only a few reports on the animal models of EBV infection have been reported. Here we review those previous models and describe the details on our newly developed rabbit model of malignant lymphoma induced by EBV-related virus from cynomolgus. In brief, Si-IIA-EBV or Cyno-EBV induced T-cell lymphomas in rabbits inoculated intravenously (77-90%), orally (82-89%), subcutaneously (3/3) and intraperitoneally (2/3) about 2-5 months later. EBV-DNA was detected in peripheral blood by polymerase chain reaction 2 days after oral inoculation of Cyno-EBV while antiviral capsid antigen immunoglobulin G (IgG) was raised 3 weeks after the inoculation. Rabbit lymphomas and their cell lines contained EBV-DNA and expressed EBV-encoded small RNA-1 and EBV-associated nuclear antigen. Rabbit lymphoma cell lines, some of which have specific chromosomal abnormality, showed tumorigenicity in nude mice. The significance and further research subjects of this animal model will be discussed. We believe that the present rabbit model of lymphoma with specific chromosomal abnormalities is very useful for clarifying the role of EBV in human EBV-associated lymphoma and provides a means for studying prophylactic and therapeutic regimens.

A Novel Epstein-Barr Virus-Like Virus, HVMNE, in aMacaca Nemestrina With Mycosis Fungoides

Epstein-Barr virus (EBV) infection of humans has been associated with the development of lymphoid malignancies mainly of B-cell lineage, although occasionally T-cell lymphomas have been reported. We describe here the characterization of a novel EBV-like virus (HVMNE) isolated from a simian T-cell lymphotropic virus type I/II (STLV-I/II) seronegative pigtailed macaque (Macaca nemestrina) with a cutaneous T-cell lymphoma. Immunohistochemistry studies on the skin lesions demonstrated that the infiltrating cells were of the CD3+/CD8+ phenotype. Two primary transformed CD8+ T-cell lines were obtained from cultures of peripheral blood mononuclear cells (PBMC) and skin, and, with time, both cell lines became interleukin-2–independent and acquired the constitutive activation of STAT proteins. Polymerase chain reaction analysis of the DNA from the cell lines and tissues from the lymphomatous animal demonstrated the presence of a 536-bp DNA fragment that was 90% identical to EBV polymerase gene sequences, whereas the same DNA was consistently negative for STLV-I/II sequences. Electron microscopy performed on both cell lines, after sodium butyrate treatment, showed the presence of a herpes-like virus that was designated HVMNE according to the existing nomenclature. In situ hybridization studies using EBV Epstein-Barr viral-encoded RNA probes showed viral RNA expression in both CD8+ T-cell lines as well as in the infiltrating CD8+ T cells of skin-tissue biopsies. Phylogenetic analysis of a 465-bp fragment from the polymerase gene of HVMNE placed this virus within theLymphocryptovirus genus and demonstrated that HVMNEis a distinct virus, clearly related to human EBV and other EBV-like herpesviruses found in nonhuman primates.

A Novel Epstein-Barr Virus-Like Virus, HVMNE, in aMacaca Nemestrina With Mycosis Fungoides

Epstein-Barr virus (EBV) infection of humans has been associated with the development of lymphoid malignancies mainly of B-cell lineage, although occasionally T-cell lymphomas have been reported. We describe here the characterization of a novel EBV-like virus (HVMNE) isolated from a simian T-cell lymphotropic virus type I/II (STLV-I/II) seronegative pigtailed macaque (Macaca nemestrina) with a cutaneous T-cell lymphoma. Immunohistochemistry studies on the skin lesions demonstrated that the infiltrating cells were of the CD3+/CD8+ phenotype. Two primary transformed CD8+ T-cell lines were obtained from cultures of peripheral blood mononuclear cells (PBMC) and skin, and, with time, both cell lines became interleukin-2–independent and acquired the constitutive activation of STAT proteins. Polymerase chain reaction analysis of the DNA from the cell lines and tissues from the lymphomatous animal demonstrated the presence of a 536-bp DNA fragment that was 90% identical to EBV polymerase gene sequences, whereas the same DNA was consistently negative for STLV-I/II sequences. Electron microscopy performed on both cell lines, after sodium butyrate treatment, showed the presence of a herpes-like virus that was designated HVMNE according to the existing nomenclature. In situ hybridization studies using EBV Epstein-Barr viral-encoded RNA probes showed viral RNA expression in both CD8+ T-cell lines as well as in the infiltrating CD8+ T cells of skin-tissue biopsies. Phylogenetic analysis of a 465-bp fragment from the polymerase gene of HVMNE placed this virus within theLymphocryptovirus genus and demonstrated that HVMNEis a distinct virus, clearly related to human EBV and other EBV-like herpesviruses found in nonhuman primates.

Coxsackievirus B4 myocarditis in an orangutan

A 37-year-old female orangutan died at the zoological garden. Autopsy examination demonstrated severe coxsackievirus B4 myocarditis immunohistochemically as a cause of the death. Apoptosis of the cardiac muscle cells was observed using the TdT-mediated dUTP-biotin nick endo labeling method and was considered to play a role in the myocarditis. Congestion of the liver and both lungs due to cardiac failure was also observed. Coxsackievirus infection is found frequently in the Okinawan human population. The present orangutan's infection might have come from visitors who were allowed to go near the orangutan. Malignant tumors, severe suppurative infections, and intestinal parasite infections were not observed. Epstein-Barr virus DNA was detected in lymph nodes, but there was no Burkitt's lymphoma.

Multi-epitope DNA vaccines

The evolution of vaccine strategies has seen a move from whole organisms to recombinant proteins, and further towards the ultimate in minimalist vaccinology, the epitope. The epitope-based approach is clearly compelling as only a relatively tiny, but immunologically relevant, sequence is often capable of inducing protective immunity against a large and complex pathogen. The post-reductionist era in epitope-based vaccinology has seen a quest to re-construct complexity and design vaccines containing many epitopes. The hope is that such multi-epitope vaccines might induce immunity against multiple antigenic targets, multiple strain variants, and/or even multiple pathogens. The ability of DNA vaccination to co-deliver a series of antibody and/or CD4 T cell epitopes remains largely unexplored. Successful viral vector and DNA-based experimental vaccines coding for multiple contiguous CD8 CTL epitopes have, however, recently been described. This simple CTL poly-epitope (or polytope) strategy may find application in the design of vaccines against several diseases including EBV, HIV and cancer.

Malignant lymphoma induction of rabbits with oral spray of Epstein-Barr virus-related herpesvirus from Si-IIA cells (HTLV-II-transformed Cynomolgus cell line): a possible animal model for Epstein-Barr virus infection and subsequent virus-related tumors in humans

Malignant lymphoma (ML) was induced in eight of nine rabbits inoculated by oral spray of the cell-free pellets from Si-IIA culture (HTLV-II-transformed leukocyte cell line of the Cynomolgus-producing Epstein-Barr virus (EBV)-related herpesvirus) after 64-141 days. None of the rabbits inoculated with EBV from B-95-8 cells or HTLV-II from MOT cells developed ML. Malignant lymphomas were usually of diffuse, large-cell or mixed type. HTLV-II infection was excluded by the polymerase chain reaction (PCR) and the particle agglutination test. EBV-encoded RNA-1 and EBV-related DNA were detected in the tumor tissues by in situ hybridization and PCR, respectively. Anti-viral capsid antigen of EBV antibody (anti-VCA) was observed 3 weeks after oral inoculation of Si-IIA cell-free pellets. Polymerase chain reaction revealed continuous detection of EBV-related virus DNA in the peripheral blood leukocytes from 3 days after oral inoculation. These results show that ML induced orally with Si-IIA cell-free pellets was caused by EBV-related herpesvirus harbored by Si-IIA cells. Oral spray of EBV from B-95-8 also induced EBV infection in rabbits, which was confirmed both by the presence of anti-VCA and by PCR. These oral infection and malignant lymphoma induction systems of rabbit using EBV-related virus from Si-IIA or human EBV are useful animal models for the study of EBV infection and EBV-related lymphomas in humans.