The devastating effects of viral diseases such as AIDs, smallpox, polio, influenza, diarrhea, and hepatitis are well known, and studies of viral pathogens are easily justified from a world health perspective. The importance of these and other viruses, however, extends well beyond their disease-causing potential. When properly harnessed, viruses can be powerful research tools for dissecting cellular processes.  Viruses also offer great promise as expression and delivery systems for vaccines and therapeutic genes (“gene therapy”).  This grant proposal seeks support for training virologists prepared to meet research challenges common to all viruses- which includes developing strategies to protect humans, animals, or plants from viral diseases as well as exploiting viruses as tools to improve the quality of life.

Viruses are extremely diverse and have evolved to infect nearly all life forms.  Amid this diversity, viruses with similar genome organizations exhibit major conserved themes in their replication strategies. Once inside a cell, all viruses must uncoat, replicate and transcribe their genomes, and then repackage their genomes into viral progeny that are released from cells. RNA viruses in particular must coordinate the switch between plus and minus strand synthesis and between replication and transcription while protecting their genomes from cellular nucleases. Because of the conserved nature of a virus’s intracellular life cycle, fundamental advances in our understanding of replication have come from viruses that infect both animal and non-animal hosts. One drawback of existing training programs in virology is the artificial division of plant and animal virus studies into separate university departments.  Training in animal virology is often associated with medical or veterinary schools, while research in plant virology is frequently part of agriculture-based programs. Such  limits in Virology training environments have led to the continuing segregation of topics according to virus hosts in the organization of workshop and symposium sessions at National and International meetings and the omission of studies on non-animal viruses in chapters on replication and gene expression in major Virology textbooks.  The Virology Program at the University of Maryland brings animal, plant and fungal virology together in an integrative program that broadens the research perspective and abilities of new virologists. The proximity of world-class virus and viroid research programs at the University of Maryland (College Park), the Center for Biosystems Research (College Park), the Virginia-Maryland Regional College of Veterinary Medicine (College Park), the National Institutes of Health (Bethesda), and the United States Department of Agriculture (Beltsville) makes this unique graduate training program possible. 

A basic understanding of how viruses exploit the cellular machinery to replicate their genomes holds the key to the control and manipulation of viruses; thus, the focus of this integrative program is the study of viral replication and gene expression. The inclusion of virologists in this program who specialize in a wide diversity of virus families results in an effective cross-pollination of research ideas as scientists, graduate students and post-doctoral trainees interact. 

The need for well-trained and imaginative virologists in the public health community is clear. During the next 25 years, the world population will increase by 2.5 billion people (mostly in developing countries). Increasing global trade, changes in insect vector populations, and global climate change all demand that the U.S. view viral diseases from a world health perspective. In spite of significant advances in the development of vaccines and antiviral agents, the death toll from viral diseases continues to climb. Presently, the World Health Organization (WHO) is involved in the development and/or implementation of viral vaccine programs for: acute respiratory viruses (including Respiratory syncytial virus and Parainfluenza virus), Dengue virus, Japanese encephalitis virus, Yellow fever virus, Hepatitis A, B, and C viruses, Human immunodeficiency virus, Measles virus, Mumps virus, Poliovirus, Rotavirus, Human papilloma virus, and Chicken pox virus. Many vaccine strategies rely on the attenuation of viruses to produce “live” vaccines. Knowledge of viral replication is essential to understanding the molecular basis for attenuation because genetic lesions in attenuated viruses are often located in replicase proteins or in non-coding regions of the genome. A particularly promising area of vaccine research applies knowledge of viral replication to the design of improved second-generation vaccine candidates using reverse genetics systems.  Our Virology Training Program includes many investigators associated with vaccine development programs allowing trainees to learn about virus vaccine research and the integral part that knowledge of virus replication and gene expression plays in this work. 

A second area of virology research with great potential for improving human health is the use of plants as gene delivery systems. Most research in this area is currently focused on the development of transgenic plants for the manufacturing of commodity chemicals, nutraceuticals, and pharmaceuticals that have medical importance such as antibodies or vaccines.  This strategy has several advantages.  For example, a field of plants expressing a given protein is simpler and less expensive to maintain than the large bacterial fermentation systems currently in use. Also, many proteins require post-translational modifications for activity, processes that occur only in eukaryotic systems.  Finally, plant-based expression technologies such as edible vaccines are relatively simple to initiate and thus are ideally suited for use in developing countries where a technologically advanced infrastructure is not available.

For such plant-based expression systems to be successful, high levels of recoverable product are essential. Unfortunately, the creation of transgenic plants is a time consuming and expensive task and the plants obtained often express insufficient levels of product to be of commercial or clinical value. This requirement greatly restricts the numbers and types of foreign gene constructs that can be tested, and makes it difficult to respond rapidly to emerging disease threats. The use of plant viruses as gene expression vectors provides a promising alternative to plant transformation. The main advantages of viral based vectors are the speed in which new expression constructs can be created, the ease of infecting large numbers of plants, and the potential for high levels of expression.  Plant viruses thus make ideal platforms for gene expression.  Our Virology Training Program includes several investigators who study plant virus replication at the molecular level, who are already training future virologists in this important and emerging field of biomedical research. 

A third area where virus research can make an important contribution to human health is in the development of novel treatments for both viral and nonviral diseases.  Vaccination remains the preferred strategy for controlling viral diseases because the intimate association of viruses with the host cellular machinery complicates the development of safe drugs. However, certain viruses have proven difficult targets for vaccines, and antiviral drugs provide the only option for controlling disease. Fundamental studies of viral replication and gene expression are relevant to the development of such drugs because most antiviral agents are targeted to viral replicase proteins. Other potential strategies for interrupting the virus replication cycle, such as induction of gene silencing by delivery of antisense oligonucleotides or modulation of immune regulators are possible and their success depends on knowledge of viral replication at the molecular level. Finally, retroviruses, vaccinia viruses, adenoviruses, adeno-associated viruses, and herpes viruses are all under investigation as gene delivery vectors for genetic diseases. Here again, a detailed knowledge of virus replication and gene expression is essential. Several virologists in our Virology Training Program study the structure and function of viral replicase proteins as well as essential genomic replication elements.  Trainees will thus learn the relationship between basic research and its application to important health problems.