Advancing the health and well-being of animals and people

Co-Principal Investigator:  Hélène Marquis
Co-Principal Investigator:  Kirk Mauer
Resident Trainee: Bryant Blank, Laboratory Animal Medicine

Contact Information: Email:; Phone: 607-253-3273
Sponsor: Collaborative Research Grants Program
Grant Number: N/A
Title: Modulation of Innate Immunity by a Bacterial Phospholipase
Annual Direct Cost: $45,000
Project Period: 10/01/10-09/30/31/2

DESCRIPTION (provided by applicant): The social and economic impact of infectious diseases is enormous. It is estimated that 300 million people suffer from AIDS, malaria or tuberculosis worldwide, which account for about half of all infectious diseases. There is a critical need for new interventions that modulate the immune response to infection, either to hasten clearance of pathogenic microbes or enhance the efficacy of vaccines. Our long-term goal is to develop a new and safe approach to hasten and enhance the immune response to microbial pathogens. Listeria monocytogenes is a foodborne bacterial pathogen that has the ability to multiply in the cytosol of infected cells and to spread from cell to cell using an actin-based mechanism of motility. Escape from vacuoles, which are formed upon cell-to-cell spread, is mediated in part by a phospholipase C (PC-PLC), whose activation is dependent on a decrease in vacuolar pH. Therefore, active PC-PLC is secreted specifically in acidified vacuoles during the intracellular life cycle of L. monocytogenes. We have generated a mutant strain of L. monocytogenes that constitutively secretes active PC-PLC in the cytosol of infected cells. Loss of regulation of PC-PLC activity during infection does not affect host cell viability or the ability of bacteria to multiply intracellularly. Similarly, loss of regulation of PC-PLC activity does not change the initial course of infection in mice; however, beginning at 2 days post-infection there is an increase in the efficiency of immune clearance.

Our hypothesis is that PC-PLC up regulates the immune response to infection when delivered as an active enzyme in the cytosol of host cells, consequently conferring a protective effect against infection.

The objectives of this application are: (1) to determine how PC-PLC influences the transcriptional and translational response to infection in macrophages, and (2) to systematically characterize the effects of PC-PLC on the immune response to infection in vivo. If our results confirm that PC-PLC acts as an adjuvant to hasten and enhance the immune response to infection, we will next investigate methods to efficiently and safely deliver PC-PLC as a novel treatment modality.

The studies described herein have the capability to significantly impact our ability to manipulate the immune response to other infectious diseases, potentially leading to the development of new prophylactic and curative approaches.