Defining the pathogenesis of gammaherpesvirus and Plasmodium coinfections

About This Grant

PROJECT SUMMARY Epstein-Barr virus (EBV) is a human DNA tumor virus that is present in nearly all cases of the endemic form of Burkitt lymphoma (eBL). In addition to the presence of an oncogenic gammaherpesvirus (GHV), eBL is characterized by translocations between the immunoglobulin locus and c-Myc proto-oncogene. Interestingly, this cancer occurs primarily in areas of the world where infections with the human malaria parasite Plasmodium falciparum (P. falciparum) are common. The epidemiology of these diseases supports the hypothesis that coinfections with EBV and P. falciparum cooperate to promote eBL development, but direct evidence to support this hypothesis is lacking. Since neither EBV nor P. falciparum readily infect mice, we coinfected mice with two well-established model pathogens, murine gammaherpesvirus 68 (MHV68) and P. yoelii, in an effort to better understand mechanisms by which GHVs and Plasmodium species might synergize to promote oncogenic mutations. MHV68 is a murine gammaherpesvirus that is genetically related to EBV and exhibits similar pathogenic phenotypes, especially coopting germinal center (GC) B cell reactions to establish long-term chronic infections in B lymphocytes. Like P. falciparum, P. yoelii stimulates polyclonal B cell activation and achieves high percentages of parasitemia prior to immune-mediated clearance. Using a newly developed PCR-based assay, we evaluated B cells following coinfections and detected the presence of Igh/Myc translocations that were only present in mice infected with both MHV68 and P. yoelii. This indicates that the defining eBL chromosomal abnormality can be generated through coinfecting mice with a GHV and Plasmodium parasite. Moreover, we found that ~90% of cells infected with MHV68 have expressed the GC mutagenic enzyme activation-induced cytidine deaminase (AID). These findings support our major hypothesis that MHV68 and P. yoelii interactions in GC B cells promote oncogenic Igh/Myc mutations. Experiments proposed in this application seek to understand how coinfection with P. yoelii impacts MHV68 latency, reactivation and transcription to promote translocations. We will identify viral gene products required and define the capacity of P. yoelii to stimulate B cell activation that leads to genomic instability. We will determine how GC B cell enzyme AID and coinfection-induced transcription synergize to facilitate non-immunoglobulin locus mutations, and we will define the oncogenic potential of coinfections over time. Results of this work will provide a more complete understanding of how altered infection dynamics due to GHV and Plasmodium species coinfections promote mutations such as those that define eBL.