Norwalk Virus-Like Particles (VLPs) for Studying Natural Groundwater DisinfectionEPA Grant Number: R824770 shared with R824775
Title: Norwalk Virus-Like Particles (VLPs) for Studying Natural Groundwater Disinfection
Investigators: Grant, Stanley B.
Current Investigators: Grant, Stanley B. , Estes, Mary K. , Olson, Terese M. , Ogunseiten, Oladele
Institution: University of California - Irvine , Baylor College of Medicine
Current Institution: University of California - Irvine , Baylor College of Medicine , University of Michigan
EPA Project Officer: Hiscock, Michael
Project Period: September 1, 1995 through August 1, 1996 (Extended to October 31, 1999)
Project Amount: $230,000
RFA: Water and Watersheds (1995) Recipients Lists
Research Category: Water and Watersheds , Water
Description:Many outbreaks of gastroenteritis occur in the U.S. and these are often caused by waterborne or foodborne transmission of Norwalk virus (NV). Some of these outbreaks can be traced to the contamination of groundwater supplies by inadequate filtration of sewage effluent from private or community septic tank systems. To limit the spread of microbial pathogens through groundwater, the U.S. EPA has proposed a new set of rules under the 1996 reauthorization of the Safe Drinking Water Act that would require public water systems to disinfect source water from each groundwater well unless "natural disinfection" can be demonstrated or a variance can be obtained. With respect to NV, however, the efficacy of these proposed rules is questionable because the environmental variables that control the "natural disinfection" of this particular viral pathogen in subsurface systems are largely unknown. We are utilizing recombinant Norwalk virus (rNV) particles as a model system to overcome the long-standing barrier to conducting filtration experiments with NV. These particles are produced by a molecular biology procedure in which the gene for the single structural protein for NV is cloned into a baculovirus expression system. When the recombinant capsid protein is expressed, it spontaneously self-assembles into virus-like particles (VLPs) that are morphologically and antigenically identical to the native Norwalk virus. The resulting rNV VLPs differ from live NV in only one known but important respect: they lack the genetic material (in particular, RNA) necessary for replication in the host. Thus, while the rNV VLPs "look" like a real Norwalk virus, they are harmless protein particles that cannot initiate infection in humans. The idea behind the current project is to utilize these rNV VLPs, which were originally developed for a new human vaccine, to investigate the natural removal of Norwalk virus in groundwater by physicochemical filtration.
In the first year of this project, we have completed a set of experiments examining the influence of pore water pH on the surface charge of the rNV VLPs and their filtration rates in packed beds of quartz sand (manuscript submitted for publication). These initial results suggest that pore water pH may be the most important factor in determining the capacity of groundwater systems to provide "natural disinfection" by physicochemical filtration. Ultimately, the rNV VLPs could lead to new approaches for establishing set-back distances between groundwater wells and potential sources of viral pathogens (like groundwater recharge basins and septic tanks) and for assessing the degree to which water contaminated with human waste is "naturally disinfected" by percolation through the subsurface matrix.