Research:

Potential rotation projects
My lab primarily investigates Plasmodium falciparum malaria-induced dysregulation of EBV-specific T cell immunity and its role in the etiology of endemic Burkitt lymphoma (eBL), the most prevalent pediatric cancer in Equatorial Africa. Within the context of our ongoing studies of healthy Kenyan children with divergent malaria exposure histories (chronic/repeated infections in a holoendemic area versus low infection rates in a nearby highland, malaria hypoendemic area) and by examining children diagnosed with eBL we have established a repository of samples that can be used to address this question.

1. One avenue of exploration involves homeostatic cytokine regulation of memory T cells. IL-15 and/or IL-7 responsiveness of EBV-specific memory T cells may be impaired in children with chronic malaria exposure and in children with endemic Burkitt lymphoma (eBL). We would like to investigate IL-15Ra and IL-7Ra surface expression, and CFSE proliferation of EBV-specific T cells in response to cognate antigen with and without IL-15 or IL-7 stimulation and compared children with divergent malaria exposure histories and children diagnosed with eBL. T cell responsiveness to IL-15 and IL-7 can be measured by STAT5 phosphorylation and the specificity of this effect for EBV-specific T cells can be evaluated by comparing IL-15Ra and IL-7Ra expression and responsiveness on other lymphocyte subsets and CMV-specific T cells.

2. Another putative mechanism by which malaria may interfere with the development of immunologic memory and influence EBV-specific T cell immunity is through the Programmed death-1 (PD-1) pathway. PD-1 is an immune inhibitory molecule that negatively regulates activated immune cells upon interacting with its ligands, programmed death ligand-1 (PD-L1) and programmed death ligand-2 (PD-L2) resulting in down-regulation of immune responses. Previous studies in murine and primate viral and parasitic diseases have reported the up-regulation of PD-1 and soluble PD-1 (sPD-1) but no studies have reported the expression of PD-1 in individuals from areas with divergent malaria transmission dynamics or in children presenting with endemic Burkitt lymphoma (eBL). In addition the PD-1 pathway has been suggested to be involved in the evasion of antitumor immunity by the host immune system. Preliminary studies in my lab suggest that PD-1 expression is significantly increased on CD4, CD8 T cells, B cells and NK cells in those residing in high malaria transmission areas compared to age-matched individuals without a history of malaria exposure. Future studies will explore the kinetics of this effect, the impact of antigen dose and how malaria exploits PD-1 mediated regulation to impair the development of immunologic memory.

3. Another area of interest is the role of Th17 cells in pediatric immunity. Because of the naturally delayed production of T_H1 mediated pro-inflammatory cytokines (i.e. IL-12 and IFN-g) in utero, neonatal immunity is thought to be ‘suppressed’. However, more recent studies have shown that neonatal monocytes and antigen-presenting cells do express pro-inflammatory and regulatory cytokines (i.e. IL-6, IL-10 and IL-23) and at higher levels than adults. Thus T_H17 cells appear to be an early, sequential response to pathogens prior to the induction of a T_H1 or T_H2 response. T_H17 cells are also stimulated with IL-21 and IL-22 in an autocrine and paracrine fashion by natural killer cells. Exploring Th17 cell responses within the context of early-age human infections with malaria and EBV would be an exciting new avenue of investigation in my laboratory.