Immunological aspects of Epstein-Barr virus infection

Epstein-Barr Virus Gastritis

We describe an exceedingly rare case of severe gastritis that was temporally associated with primary Epstein-Barr virus (EBV) infection. The patient was a 59-year-old immunocompetent man who presented with intermittent fever of unknown origin and epigastric pain for 18 days. A computed tomographic scan of the abdomen showed diffuse thickening of the gastric wall and esophagogastroduodenoscopy revealed numerous ulcers in the stomach. Histologic examination of gastric biopsies showed a dense and diffuse atypical lymphoid infiltrate in the lamina propria with erosions and focal lymphoepithelial lesions. No lymphoid follicles or Helicobacter microorganisms were identified. Immunohistochemical studies demonstrated the lymphoid infiltrate to consist of mixed T and B cells. Immunoglobulin heavy chain gene arrangement analysis showed a polyclonal pattern. The plasma cells present in the biopsies exhibited no light chain restriction as determined by in situ hybridization. Concurrent clinical work-up revealed peripheral lymphocytosis with atypical lymphocytes and positive serum IgM antibody to EBV capsid antigen in the absence of IgG antibody. These findings indicated that the gastric abnormalities were related to primary EBV infection as the predominant manifestation of infectious mononucleosis. This was further confirmed by subsequent in situ hybridization showing numerous EBV-positive lymphocytes in the gastric mucosa. The patient's symptoms were spontaneously resolved with only supportive treatment. A follow-up endoscopy 2 months later showed completely normal gastric mucosa and he remained well with no gastrointestinal complaints for 2 and a half years. This case illustrates the importance of a high index of suspicion to avoid misdiagnosis of gastric lymphoma that requires more aggressive therapies.

Epstein-Barr virus-induced hemophagocytic lymphohistiocytosis and X-linked lymphoproliferative disease: a mimicker of sepsis in the pediatric intensive care unit

A rare complication of infection with the Epstein-Barr virus is the development of hemophagocytic lymphohistiocytosis. Although most cases of Epstein-Barr virus-induced hemophagocytic lymphohistiocytosis develop in immunocompetent individuals, the rare immunodeficiency X-linked lymphoproliferative disease is often unmasked by Epstein-Barr virus infection and is clinically indistinguishable from Epstein-Barr virus-induced hemophagocytic lymphohistiocytosis. We describe the clinical course and management of a previously healthy 17-year-old boy who presented with hemodynamic collapse and severe systemic inflammatory response syndrome resulting from overwhelming hemophagocytosis in the setting of X-linked lymphoproliferative disease. A novel therapeutic approach using anti-tumor necrosis factor alpha therapy was instituted, aimed at attenuating the viral-induced hyperinflammatory state. Given the similarity to overwhelming sepsis, yet a substantially different therapeutic approach, this case illustrates the importance of early recognition and prompt treatment that are necessary to reduce the high morbidity and mortality associated with Epstein-Barr virus-induced hemophagocytic lymphohistiocytosis and X-linked lymphoproliferative disease.

Pathogenesis of chronic active Epstein-Barr virus infection: is this an infectious disease, lymphoproliferative disorder, or immunodeficiency?

Chronic active Epstein-Barr virus infection (CAEBV) is characterised by chronic or recurrent infectious mononucleosis-like symptoms, such as fever, hepatosplenomegaly, persistent hepatitis and extensive lymphadenopathy. Patients with CAEBV have high viral loads in their peripheral blood and/or an unusual pattern of EBV-related antibodies. This disease is rare but severe with high morbidity and mortality. Nearly three decades have passed since this disease was first identified, and recent advances in technology have increased our understanding of CAEBV pathophysiology. There is accumulating evidence that the clonal expansion of EBV-infected T or natural killer (NK) cells plays a central role in the pathogenesis of CAEBV. However, it remains unclear whether CAEBV is truly a monoclonal lymphoproliferative disorder. EBV-infected T or NK cells are able to evade the host cellular immune system due to the limited expression of viral proteins of reduced antigenicity. Recent studies suggest that infection of T or NK cells is a common event during primary EBV infection. A defect or single nucleotide polymorphism in host immune-modulating genes may allow for the expansion of virus infected cells giving rise to CAEBV. In this review, I summarise our current understanding of the pathogenesis of CAEBV and propose a model of CAEBV pathogenicity.

Cerebral lymphoma in an adenosine deaminase-deficient patient with severe combined immunodeficiency receiving polyethylene glycol-conjugated adenosine deaminase

Polyethylene glycol-conjugated adenosine deaminase (PEG-ADA) provides an alternate therapy to mismatched stem cell transplantation for patients with ADA-deficient severe combined immunodeficiency. Although replacement therapy with PEG-ADA is effective in preventing infections, immune function does not return to normal, and most patients remain lymphopenic. Information is limited regarding the prognosis of patients on long-term ADA-replacement therapy. Here we present a case of a 10-year-old child who was diagnosed with ADA-severe combined immunodeficiency at 4 weeks of age after contracting pneumonia. Treatment with PEG-ADA was begun, the biochemical markers of ADA deficiency normalized, and his clinical progress was very good without significant infections. At 10 years of age, after presenting with headaches and cranial nerve deficits, he was diagnosed with Epstein-Barr virus-positive malignant brain lymphoma. It did not respond to various regimens of aggressive chemotherapy, and the patient expired 5 months later. We speculate that in this patient the immunologic surveillance by T cells may have been defective with respect to elimination of Epstein-Barr virus-infected cells, hence the formation of neoplasm. The possible mechanisms underlying such pathology are reviewed.

High fatality rate of Epstein-Barr virus-associated lymphoproliferative disorder occurring after bone marrow transplantation with rabbit antithymocyte globulin conditioning regimens

Epstein-Barr virus (EBV)-associated lymphoproliferative disorder (EBV-LPD) following bone marrow transplantation can be fatal. The major risk factors for the development of EBV-LPD are ex vivo T-cell depletion or in vivo T-cell depletion with either antithymocyte globulin (ATG) or monoclonal anti-T-cell antibodies. Between March 1999 and January 2001, a total of 23 transplants with ATG of equine source (20 transplants) and ATG of rabbit source (3 transplants) used as part of the preparatory regimen were performed at the Barbara Ann Karmanos Cancer Institute in Detroit, Mich. The three patients who received rabbit ATG developed EBV-LPD between 60 and 90 days following bone marrow transplantation. However, there were no cases of EBV-LPD in the equine group. Treatment given in these cases consisted of tapering immunosuppression, antiviral therapy, unprocessed donor lymphocyte infusion, mobilized peripheral blood progenitor cell rescue infusion (one patient), and chemotherapy (one patient). All three patients died of complications from EBV-LPD. The association of rabbit ATG with the development of EBV-LPD suggests that patients receiving rabbit ATG as part of their preparatory regimens require close monitoring of the EBV viral load and possible early intervention with antiviral therapy.

Heat shock protein 90 expression in Epstein-Barr virus-infected B cells promotes gammadelta T-cell proliferation in vitro

The aim of this study was to elucidate the in vitro response of gammadelta T cells to Epstein-Barr virus (EBV)-infected B cells and to determine whether EBV-induced heat shock proteins (HSPs) might serve as gammadelta T-cell stimulants. Cytofluorometric analysis revealed HSP90 cell surface expression in 12% of the EBV-immortalized B-cell population in all four of the B-cell lines tested. HSP27, HSP60, and HSP70 were not detected on the cell surface by cytofluorometry in these same B-cell lines. HSP90 and HSP60, but not HSP70 or HSP27, were detected on the cell surface after 125I cell surface labeling and immunoprecipitation with anti-human HSP monoclonal antibodies. In vitro kinetic studies indicated that gammadelta T cells increased at least twofold by day 11 postinfection in cultures of EBV-seronegative peripheral blood lymphocytes infected with EBV, whereas percentages of alphabeta T cells in these same cultures either decreased slightly or remained relatively unchanged in response to EBV infection. Addition of anti-human HSP90 monoclonal antibody to the EBV-infected lymphocyte cultures inhibited gammadelta T-cell expansion by 92%. The inhibition of gammadelta T-cell expansion by anti-HSP90 antibody was reversed upon treatment with exogenous HSP90. Taken together, these results indicate that HSP90 played an important role in the stimulation of gammadelta T cells during EBV infection of B cells in vitro and may serve as an important immunomodulator of gammadelta T cells during acute EBV infection.

Immune evasion by gamma-herpesviruses

Persistent viruses, such as herpesviruses, transmit infection by evading cytotoxic T cells during lytic replication. The gamma-herpesviruses additionally evade T cells during the proliferation of latently infected lymphocytes to establish a persistent viral reservoir. Lytic gene expression in sites of lymphoproliferation appears to make a vital contribution to this latent immune evasion. Lytic antigens may therefore be a key immune target. Investigations into a murine gamma-herpesvirus have now provided evidence that vaccination with apathogenic, latency-deficient mutants can largely protect against subsequent wild-type gamma-herpesvirus latency establishment.

Successful Unrelated Cord Blood Transplantation for Epstein-Barr Virus-Associated Lymphoproliferative Disease with Hemophagocytic Syndrome

We report a case of successful umbilical cord blood transplantation (CBT) for Epstein-Barr virus (EBV)-associated lymphoproliferative disease (LPD) in a 6-year-old girl. The patient had hemophagocytic syndrome with excessive circulating levels of EBV DNA that was refractory to immunochemotherapy. Multiple hepatosplenic lesions favored the diagnosis of EBV-associated LPD, although the aggressive course precluded the histopathologic diagnosis. Unrelated CB cells mismatched at 1 HLA locus were infused after patient conditioning with 900 mg/m2 etoposide, 2 g/m2 cytarabine, 16 mg/kg busulfan, and 200 mg/kg cyclophosphamide. Complete chimeric status was obtained on day 19 posttransplantation. Drug fever and acute graft-versus-host disease of the skin (grade II) were the major complications. A transient increase of EBV DNA 1 year after CBT indicated a primary EBV infection of the donor cells. The patient is alive with no evidence of disease 27 months after CBT. There has been no previous report of successful CBT for EBV-related LPD/lymphoma. CBT can be a curative treatment for the disease, even if no viral memory has been set in the stem cell source.

Dominant expression of interleukin-10 and transforming growth factor-beta genes in activated T-cells of chronic active Epstein-Barr virus infection

Chronic active Epstein-Barr virus (EBV) infection is a chronic mononucleosis syndrome associated with clonal proliferation of EBV-carrying T-/natural killer (NK)-cells. High levels of circulating EBV and activated T-cells are sustained during the prolonged disease course, whereas it is not clear how ectopic EBV infection in T-/NK-cells has been established and maintained. To assess the biological role of activated T-cells in chronic active EBV infection (CAEBV), EBV DNA and cellular gene expressions in peripheral T-cells were quantified in CAEBV and infectious mononucleosis (IM) patients. In CAEBV, HLA-DR(+) T-cells had higher viral load and larger amounts of IFN gamma, IL-10, transforming growth factor-beta (TGF beta), and cytotoxic T lymphocyte antigen-4 (CTLA4) mRNA than HLA-DR(-)T-cells. HLA-DR(+) T cells of IM patients transcribed more IFN gamma and IL-10 than their HLA-DR(-)T cells. Expression levels of IFN gamma and forkhead box p3 (Foxp3) in CAEBV HLA-DR(+) T-cells were higher than in IM HLA-DR(+) T-cells. The effective variables to discriminate the positivity of HLA-DR were IL-10, IFN gamma, CTLA4, TGF beta, and IL-2 in the order of statistical weight. EBV load in CAEBV T-cells correlated with the expression levels of only IL-10 and TGF beta. These results suggest that CAEBV T-cells are activated to transcribe IFN gamma, IL-10, and TGF beta excessively, and the latter two genes are expressed preferentially in the EBV-infected subsets. The dominant expression of regulatory cytokines in T-cells may imply a viral evasion mechanism in the disease.

A consecutive priming-boosting vaccination of mice with simian immunodeficiency virus (SIV) gag/pol DNA and recombinant vaccinia virus strain DIs elicits effective anti-SIV immunity

To evaluate immunity induced by a novel DNA prime-boost regimen, we constructed a DNA plasmid encoding the gag and pol genes from simian immunodeficiency virus (SIV) (SIVgag/pol DNA), in addition to a replication-deficient vaccinia virus strain DIs recombinant expressing SIV gag and pol genes (rDIsSIVgag/pol). In mice, priming with SIVgag/pol DNA, followed by rDIsSIVgag/pol induced an SIV-specific lymphoproliferative response that was mediated by a CD4+-T-lymphocyte subset. Immunization with either vaccine alone was insufficient to induce high levels of proliferation or Th1 responses in the animals. The prime-boost regimen also induced SIV Gag-specific cellular responses based on gamma interferon secretion, as well as cytotoxic-T-lymphocyte responses. Thus, the regimen of DNA priming and recombinant DIs boosting induced Th1-type cell-mediated immunity, which was associated with resistance to viral challenge with wild-type vaccinia virus expressing SIVgag/pol, suggesting that this new regimen may hold promise as a safe and effective vaccine against human immunodeficiency virus type 1.

[Viral carcinogenesis of head and neck tumors]

Approximately 15% of malignant diseases are caused by infectious agents. Human papilloma viruses (HPV) can be frequently found in oral carcinomas, especially tonsillar cancer. A group of HPV-infected tumors shows clear signs for a virally induced transformation process: high-risk HPVs can be detected in all tumor cells, the viral oncogenes E6 and E7 are constantly expressed and lead to upregulation of cellular p16(INK4a), a cyclin-dependent kinase inhibitor. The patients frequently lack typical risk factors associated with head and neck cancers such as drinking and smoking. Epstein-Barr viruses (EBV) are associated with lymphoproliferative disorders and cause nasopharyngeal carcinoma (NPC). NPC has a high incidence in some East Asian countries. In this review, the molecular pathogenesis of HPV- and EBV-associated malignancies are described and the clinical relevance of the presented findings is discussed.