Transformation-associated Epstein-Barr virus antigens as targets for immune attack

Case report: a diagnostically challenging conjunctival mass caused by the Epstein-Barr virus

We present a paediatric case of infectious mononucleosis in a 13-year old, manifesting with follicular conjunctivitis and a conjunctival mass in one eye with no evidence of leucocytosis on the blood count. The diagnosis was confirmed following surgical excision and biopsy. The case represented a diagnostic challenge due to its atypism and given the steady increase in the prevalence of EBV-related ocular diseases in the last years, this report can serve as an example to prompt earlier serological tests to identify the aetiology in similar cases. This is important because EBV can be treated with acyclovir early in the active viral phase.

Cytotoxic drug sensitivity of Epstein-Barr virus transformed lymphoblastoid B-cells

BACKGROUND

Epstein-Barr virus (EBV) is the causative agent of immunosuppression associated lymphoproliferations such as post-transplant lymphoproliferative disorder (PTLD), AIDS related immunoblastic lymphomas (ARL) and immunoblastic lymphomas in X-linked lymphoproliferative syndrome (XLP). The reported overall mortality for PTLD often exceeds 50%. Reducing the immunosuppression in recipients of solid organ transplants (SOT) or using highly active antiretroviral therapy in AIDS patients leads to complete remission in 23-50% of the PTLD/ARL cases but will not suffice for recipients of bone marrow grafts. An additional therapeutic alternative is the treatment with anti-CD20 antibodies (Rituximab) or EBV-specific cytotoxic T-cells. Chemotherapy is used for the non-responding cases only as the second or third line of treatment. The most frequently used chemotherapy regimens originate from the non-Hodgkin lymphoma protocols and there are no cytotoxic drugs that have been specifically selected against EBV induced lymphoproliferative disorders.

METHODS

As lymphoblastoid cell lines (LCLs) are well established in vitro models for PTLD, we have assessed 17 LCLs for cytotoxic drug sensitivity. After three days of incubation, live and dead cells were differentially stained using fluorescent dyes. The precise numbers of live and dead cells were determined using a custom designed automated laser confocal fluorescent microscope.

RESULTS

Independently of their origin, LCLs showed very similar drug sensitivity patterns against 29 frequently used cytostatic drugs. LCLs were highly sensitive for vincristine, methotrexate, epirubicin and paclitaxel.

CONCLUSION

Our data shows that the inclusion of epirubicin and paclitaxel into chemotherapy protocols against PTLD may be justified.

The ecology and pathology of Epstein-Barr virus

Epstein-Barr virus achieves its ubiquitous and uniform epidemiological distribution by a dual strategy of latency to guarantee lifelong persistence and intermittent replication to guarantee transmission. These two functions appear to dictate residence in different cell types: latency in B lymphocytes and replication in epithelial cells. Both of these cell compartments are potential sites for EBV-associated malignancies.

Increased number of Epstein-Barr virus latently infected B-cells in T-cell non-Hodgkin's lymphoma tissues

Epstein-Barr virus (EBV) is a causative agent of malignant lymphomas occurring in immunocompromised hosts. Similar lymphoid tumors can be induced in mice with severe combined immunodeficiency (SCID mice) by transplanting human B-cells with latently infected EBV. We have previously observed that when apparently EBV-negative lymphomas were engrafted into SCID mice, 11 of 18 T-cell non-Hodgkin's lymphomas (NHLs) produced EBV associated lymphomas, but only 2 of 30 engrafted with B-NHLs. Previous studies suggested that EBV-infected cell inducing lymphomas in SCID mice may preferentially exist in T-cell NHL tissues. To prove this assumption, in situ hybridization (ISH) using oligonucleotide probes for EBV-encoded small RNAs 1 (EBER1) was used in this study to demonstrate EBV-bearing lymphocytes in NHL tissues. It was found that EBV-bearing cells existe in 9 of the 10 T-cell NHL surgical specimens. By contrast, in B cell NHLs, only 2 of 10 carried EBV-bearing cells. Further semi-quantitative analysis demonstrated that apparently significantly more EBV-bearing cells were present in T-cell NHL tissues than in B-cell NHLs. Moreover, these EBV-bearing cells in lymphoma tissues were shown to be of B-cell lineage, by the combinated analysis of immunostaining with CD20 and ISH with EBER1. These results indicated the increase of EBV-bearing B-cells in T-cell NHL tissues, suggesting the activation of B-cells with latently infected EBV by neoplastic T-cells.

Multistep evolution of B-cell-derived tumors in humans and rodents

At least three genetic changes are known to contribute to the genesis of Burkitt's lymphoma (BL): the Ig/myc translocation, the presence of Epstein-Barr virus (EBV) in the vast majority of the endemic and a minority of sporadic tumors, and a p53 mutation, present in approximately 60% of the BL-derived lines. Activation of c-myc by juxtaposition to Ig sequences is a universal common denominator in endemic and sporadic EBV positive and negative BLs. It acts by preventing the cell from leaving the cycling compartment and by facilitating immune escape. EBV probably acts by expanding the target cell population at risk and prolonging its life span. This, together with the malaria co-factor, would increase the risk of the translocation accident. The p53 mutation may be essential for the continued growth of the tumors where it occurs, since introduction of wild-type p53 leads to their apoptotic death.