Human-specific Alu detection by PCR. Part 3

EBV is a herpesvirus associated with approximately 1% of tumours worldwide. EBV is the epitome of B lymphotropic viruses, but the spectrum of tumours associated with EBV extends to various types of human malignancies and carcinomas. Ubiquitous EBV infection in humans implies that most individuals carry EBV-infected cells. Therefore, mere detection of the virus in individuals with a tumour is not sufficient for establishing a causal relationship between both events. Currently there is no in vivo model that can adequately recapitulate EBV infection and its association with B-cell lymphomas. In this experiment, we can observe the development of EBV-related lymphoma in the SCID mice engrafted with hu-PBLs from EBV-seropositive donors. 72% of mice (21/29) developed tumors in EBV-positive hu-PBL/SCID chimeras. The tumors possess solid, aggressive and fatal features, and belong to high malignant NHL in histopathology. Both Alu-gene detection and immune marker examination showed that the induced-tumors were derived from human B-cell, and the tumor cells contained EBV-encoded small RNA (EBER). We have successfully induced human B-cell lymphomas in the body of hu-PBL/SCID chimeras. An in vivo model of human CD20+ B-lymphoma was established in SCID mice with huPBLs transplantation from EBV-seropositive donors.

Our present experiment showed that intraperitoneal transfer of hu-PBLs from EBV+ donors to SCID mice could generate human-derived B cell lymphomas. But it is necessary for us to monitor EBV-associated human B-cell lymphoma development in the body of SCID mice. IgG is an immunoglobulin secreted by plasmocyte when mature B cells are differentiated into plasmocytes by antigen stimulation. It is reported that human-derived IgG can be used to assess whether immune function of SCID mouse with hu-PBL engraftment is reconstructed and that antigen stimulation promotes human secondary IgG responses in hu-PBL/SCID mouse. Interestingly, a significantly positive relationship exists between the appearance of human IgG and tumorigenesis of B-cell lymphoma in the findings of our present study. Those SCID mice in which human serum IgG continuously increased would finally developed visible tumors in their bodies. In the mice without human serum IgG during all the experimental phases, no tumor or only micro-lymphaproliferative lesions was identified with microscope. From our data, human serum IgG concentrations in hu-PBL/SCID chimeras were also related to the serum IgG levels from original donors. However, the IgG level from a donor was not related to the development of tumors. It meant that all B-lymphocytes that produce different IgG levels from various donors had the same potential to develop lymphomas if activated by EBV. Moreover, it is of importance and practice for us to replicate the tumor model in the future. So we can predict the tumorigenesis by detecting human serum IgG levels from hu-PBL/SCID mice during the experimental phases. More importantly, it can give us a dependable serum marker if we want to test therapeutic intervention on the EBV-induced lymphomas.