My primary long-term career goal is to achieve independence as an NIH-funded veterinarian-scientist performing quality translational research in the emerging field of platelet immunology. My secondary long-term career goal is to bridge the gap between basic science and animal models by facilitating the development, optimization and validation of novel translational in vitro systems that emulate in vivo conditions. These long- term career goals are synergistic and innovative as there are myriad projects that could benefit from more accurate in vitro modeling. As I develop my independent research program, my short-term career goal is to advance the field of platelet immunology by investigating the role of platelet interactions with leukocytes in the innate immune response during acute viral infection using a combination of relevant well-characterized animal models and innovative in vitro models. To achieve success as a veterinarian-scientist, the next five years are critical for my transition to independent researcher. I recently finished my PhD in December of 2012, I achieved Diplomate status in the American College of Laboratory Animal Medicine in 2011, and I am currently an Instructor at Johns Hopkins University. While I have a strong background in platelet biology and in animal models of human disease, I would benefit from gaining additional research experience in virology, monocyte immunology, endothelial biology and in vitro model development, and building strong networking connections within the platelet immunology community. SERCA funding would provide me with protected time for my research, allow me to build my publication record, and provide me with the seasoned career mentorship of Dr. M. Christine Zink, DVM, PhD, DACVP, necessary to help me learn to strike an effective balance between performing research, managing a productive lab, mentoring, and pursuing funding. The Department of Molecular and Comparative Pathobiology at Johns Hopkins University School of Medicine provides a well-funded, supportive environment in which I can accomplish these goals. Collaborations with virologist, Dr. Janice Clements, and bioengineer, Dr. Wilbur Lam, will provide additional intellectual and material resources necessary to accomplish my aims, and will ultimately enable me to develop my own truly independent research program in platelet immunology and to achieve true independence as a veterinarian-scientist promoting novel in vitro technologies in this exciting new field. The emerging field of platelet immunology has demonstrated that platelets play key roles in the innate immune response to a number of pathogens through both cytokine signaling and direct cell-cell interactions.(1) However, the role of platelet-leukocyte interactions in the innate immune response to viral infection remains largely unexplored. I recently published that platelets are activated and bound to 80% of circulating CD16+ monocytes during acute infection in the SIV/macaque model of HIV infection, while platelets are resting and bound to only 6% of these monocytes in mock-inoculated controls.(2) Platelet binding induces phenotypic changes in the monocyte, including increased transcription of cyclooxygenase-2 (COX-2) with resultant synthesis of prostaglandin-E2 (PGE2).(3) PGE2 differentially modulates the expression of surface markers including CCR5 and integrins on target cells via tissue-specific E-prostanoid receptors (EPRs).(4, 5) CD16+ monocytes are preferentially infected with SIV and establish inflammatory foci in select organs such as the brain during acute infection,(6, 7) yet the reasons for this increased susceptibility to infection and the initiating stimulus that causes the first cells of this monocyte subset to cross endothelia barriers to enter some tissues more than others are unknown. My central hypothesis is that platelet activation drives the formation of circulating CD16+ platelet-monocyte aggregates (PMAs) through p-selectin - PSGL-1 interactions during acute SIV infection contributes to disease progression by upregulating COX-2 and stimulating PGE2 synthesis within the monocyte and thereby 1) increasing the susceptibility of circulating CD16+ monocytes to infection in an autocrine fashion, and 2) modulating CD16+ monocyte binding to and transmigration through different microvascular endothelial subsets into tissues in a paracrine fashion. I plan to use classic and innovative in vitro techniques with both macaque and human samples to supplement the well-characterized and consistent in vivo SIV/macaque model of acute viral infection in pursuit of the following specific aims:
Specific Aim #1 : To determine the mechanisms through which platelet activation drives platelet-monocyte aggregate formation during acute SIV infection, and to establish whether these interactions can be modulated with receptor-specific antibodies or existing anti-inflammatory or antiplatelet therapies.
Specific Aim #2 : To determine whether binding of platelets to a monocyte increases the CD16+ monocyte's susceptibility to SIV infection through autocrine PGE2 signaling through receptor subtype, EPR1, with resultant upregulation of CCR5.
Specific Aim #3 : To establish whether binding of platelets to a monocyte changes the CD16+ monocyte's affinity for microvascular endothelial subsets harvested from different organs as a result of paracrine PGE2 signaling with adjacent endothelium in an organ-specific EPR subtype dependent manner.
Despite 20 years of intense research, we still do not fully understand what drives the development of disease in HIV-infected individuals. Platelets are small anucleate blood cells that associate directly with the majority of CD16+ monocytes within the blood. CD16+ monocytes are known to become infected with HIV and initiate organ-based disease early in infection more than other monocytes. This grant will examine whether the act of platelets binding to monocytes helps to drive the development of disease by making the monocyte more susceptible to infection by HIV and encouraging the monocyte to enter into organs from the blood.