My laboratory’s long-standing interest in the biosynthetic
sorting of membrane-bound and secretory proteins has focused on the structure,
function and transcriptional regulation of the molecular chaperones of the
endoplasmic reticulum. These proteins are critical components in the folding,
assembly and modification of these types of proteins. Currently, we are focusing
on two new projects which emerged from these earlier studies: 1) the use of
molecular chaperones to produce more effective anti-tumor vaccines and 2)
the elucidation of the host response to prion infection.
1. Chaperone-based vaccines (a collaboration with the Wold laboratory).
The efficacy of molecular chaperones as adjuvants for the induction of anti-tumor
immunity has been demonstrated in many laboratories over the last two decades.
Similarly, the exploration of the therapeutic use of poxviruses in cancer
treatment has a long and diverse history. These findings have led us to determine
whether poxviruses or other vectors would be an efficient and effective way
to accomplish the intracellular delivery of molecular chaperones into tumor
cells. Once in the cells, the chaperones could sample the peptide epitopes
generated within the tumor and, upon lysis of the infected tumor cells, release
the chaperones for uptake by the immune system. The chaperones would then
provide these tumor-specific peptides to the MHC Class I antigen-presenting
molecules for cell-surface expression. In this project, our combined expertise
in chaperone structure and function and Vaccinia virus (VV) genetics and viral
vector gene therapy will be combined with the experience developed by VirRx,
Inc., in murine tumor models. This puts us in an excellent position to test
the feasibility of using VV vectors capable of expressing high levels of molecular
chaperones to induce therapeutically effective tumor immunity and to further
our basic understanding of the role of the chaperones in this process.
2. The host response to prion infection.
The need to understand the mechanisms of pathogenesis of the transmissible
spongiform encephalopathies (TSE), the causative agent of which is the prion,
has acquired an increased urgency in recent years. The recent evidence from
the United Kingdom that a new variant of Creutzfeldt-Jakob disease (vCJD)
in humans is related to “mad cow” disease, bovine spongiform encephalopathy
(BSE), and the observation of an ever-growing outbreak of chronic wasting
disease among deer and elk in the United States have brought the issue of
emerging prion diseases into the spotlight. These facts, coupled with the
realization that these outbreaks were most likely the result of human activity,
such as feeding products derived from infected animals to healthy animals,
also raises the specter of the use of the prions as agents of bioterrorism.
An increased understanding of the way in which prions, unusual “protein
only” infectious agents, cause disease may allow us to develop ways
to enhance our biological defenses against them. Further, it may enable us
to develop reagents and protocols that allow more sensitive detection of the
presence of prions in clinical samples and thus allow earlier detection of
infection. The general goal of our project is to elucidate both the cellular
and molecular response of the host to infection by prions. Currently, in one
facet of our study, we are using a tissue culture model system to examine,
in detail, early steps in infection and to assess reproducible alterations
in cellular physiology that result from prion infection and propagation. We
plan to employ microarray analysis and proteomic technologies to probe the
molecular response of the cells undergoing prion infection. A second part
of our project begins with observation that one of the most intriguing aspects
of prion infection is its interaction with the host immune system. Specifically,
while the infected host exhibits no specific humoral or cellular immune response
against prions, the immune system seems to aid rather than prevent prion propagation.
It is likely that infecting prions first come into contact with the innate
immune system of the host, specifically resident dendritic cells (DC) of the
tissues. This facet of our study is designed to study the interaction between
prions and DC and to test the hypothesis that prions evade the immune defenses
of the host by inhibiting the differentiation, maturation and/or antigen presenting
function of DC.