Endemic Burkitt's lymphoma (eBL) arises from the germinal center (GC). It is a common tumor of young children in tropical Africa and its occurrence is closely linked geographically with the incidence of P. falciparum malaria. This association was noted more than 50 years ago. Since then we have learned that eBL contains the oncogenic herpes virus Epstein-Barr virus (EBV) and a defining translocation that activates the c-myc oncogene. However the link to malaria has never been explained. Here we provide evidence for a mechanism arising in the GC to explain this association. Accumulated evidence suggests that eBL arises in the GC when deregulated expression of AID (Activation-induced cytidine deaminase) causes a c-myc translocation in a cell latently infected with Epstein-Barr virus (EBV). Here we show that P. falciparum targets GC B cells via multiple pathways to increase the risk of eBL. 1. It causes deregulated expression of AID, thereby increasing the risk of a c-myc translocation. 2. It increases the number of B cells transiting the GC. 3. It dramatically increases the frequency of these cells that are infected with EBV and therefore protected from c-myc induced apoptosis. We propose that these activities combine synergistically to dramatically increase the incidence of eBL in individuals infected with malaria.

In this study we show that in long-term persistent infection, Epstein-Barr virus (EBV)-infected cells undergoing a germinal center (GC) reaction in the tonsils are limited to the follicles and proliferate extensively. Despite this, the absolute number of infected cells per GC remains small (average of 3 to 4 cells per germinal center; range, 1 to 9 cells), and only about 38 to 55% (average, 45%) of all GCs carry infected cells. The data fit a model where, on average, cells in the GC divide approximately three times; however, only one progeny cell survives to undergo a further three divisions. Thus, a fraction of cells undergo multiple rounds of division without increasing in numbers; i.e., they die at the same rate that they are dividing. We conclude that EBV-infected cells in the GC undergo the extensive proliferation characteristic of GC cells but that the absolute number is limited either by the immune response or by the availability of an essential survival factor. We suggest that this behavior is a relic of the mechanism by which EBV establishes persistence during acute infection. Lastly, the expression of the viral latent protein LMP1 in GC B cells, unlike in vitro, does not correlate directly with the expression of bcl-2 or bcl-6. This emphasizes our claim that observations made regarding the functions of EBV proteins in cell lines or in transgenic mice should be treated with skepticism unless verified in vivo. Epstein-Barr virus (EBV) is a human herpesvirus that establishes a lifetime persistent infection in Ͼ90% of all adults (reviewed in references 21 and 51). The virus persists in rest-ing, latently infected memory B cells that circulate in the periphery and lymph nodes (5; reviewed in references 53 and 55). In these cells the virus is quiescent, at least at the level of viral protein expression (23). This lack of viral proteins is presumably a major reason why these cells are able to persist in the face of a healthy immune response. The other property for which EBV is well known is its ability to infect resting B cells and drive them to become activated proliferating lymphoblasts through the expression of nine latent proteins and several untranslated RNAs (reviewed in reference 45). The latter include a large number of microRNAs (miRNAs) (7,12,17,44).The current model of Epstein-Barr virus persistence holds that the virus drives resting B cells to become activated lymphoblasts so that they can differentiate through a germinal center (GC) reaction to become resting memory B cells (55-57), where the virus persists. The GC is the structure in the follicles of secondary lymphoid organs where antigen-activated B cells undergo a T-cell-dependent immune response (1, 35, 37). The production and maintenance of GCs are absolutely dependent on the expression of the transcription factor bcl-6 (13, 58) and are initiated by the rapid proliferation of antigenspecific B cells. During this expansion phase, B cells divide approximately every 6 to 12 h (2, 37) so that 3 Ϯ 2 founder cells can create a GC of approximatel...

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