Research Description:
Untitled Document
The research focus of the laboratory is the study of the molecular biology of
RNA-containing animal viruses and application of the findings of molecular studies
to problems of clinical relevance. The virus that we study is rubella virus, a
major human pathogen. Rubella virus causes a mild childhood disease, rubella or
German measles, but when infection occurs during pregnancy the virus can cross
the placenta, infect the fetus, and cause severe birth defects. Rubella also occasionally
persists beyond acute illness; rubella virus persistence has been associated with
endocrine dysfunctions (eg. insulin dependent diabetes mellitus) in congenitally
infected patients, chronic arthritis and neurological symptoms in adults, and
a rare fatal neurodegenerative disorder, progressive rubella panencephalitis.
Live attenuated rubella virus vaccines have been in use in the U.S. for over 25
years, resulting in a dramatic decline in both rubella and rubella-associated
birth defects.
Two aspects of rubella virus are studied in the laboratory; the first is the
basic molecular biology of the virus. We determined the sequence of the virus
genomic RNA (9762 nucleotides) and then assembled a complete cDNA copy of the
virus genome in a plasmid. The genomic cDNA is immediately adjacent to an RNA
polymerase promoter site which allows us to make genomic RNA transcripts in
vitro. When transfected into susceptible culture cells, these transcripts
initiate viral replication. With this genomic "infectious clone",
we are able to do site-directed mutagenesis on the genomic cDNA and test the
resulting phenotype by transfection with the mutated transcripts. Thus far,
our mutagenesis efforts have concentrated on cis-acting elements within the
genome that direct viral RNA transcription and replication. We have also used
the infectious clone to modify rubella virus such that it expresses foreign
proteins. Our goal is to create a recombinant vaccine vector based on the successful
live, attenuated rubella vaccine that would immunize against other viral pathogens
as well as rubella virus. We are also in the process of creating a series of
rubella virus DNA vaccines that could be of use in elimination and control efforts
against the virus in underdeveloped countries.
Secondly, we are engaged in a collaborative program with the National Immunization
Program at the U.S. Centers for Disease Control to study the molecular epidemiology
of rubella virus. Comparative phylogenetic analysis of nucleotide sequences
of viral genomes, such as rubella virus, are of great use in characterizing
virus evolution and studying the epidemiology of the virus. Such data is particularly
useful in countries in which vaccination programs are in place in that it can
identify sources of viruses and track their spread. In general, the complete
genome does not have to be sequenced and we have concentrated on sequencing
a 1300 nucleotide regions from the viral E1 glycoprotein gene. We have made
isolates from recent rubella cases in the U.S.; phylogenetic analysis of the
E1 gene sequence of these viruses indicates that there two strains of virus
in the U.S., both of which are likely of imported origin. We are also collecting
viruses isolated worldwide to establish a databank for use in upcoming rubella
control efforts in several regions of the world.
For a more complete description of research ongoing in the lab, please visit
my home page.
Cells infected with a recombinant Vaccinia virus that expresses the rubella
virus E1 glycoprotein. E1 synthesis is demonstrated by immunofluorescent staining
Recent Publications:
Pappas, C.L., Tzeng, W.-P., and Frey, T.K. 2006. Evaluation of cis-acting elements in the rubella virus subgenomic RNA that play a role in its translation. Archives of Virology 151, 327-346.
Tzeng, W.-P., Matthews, J., and Frey, T.K. 2006. Analysis of rubella virus capsid protein-mediated enhancement of replicon replication and mutant rescue. Journal of Virology, accepted for publication
Tzeng, W.-P., and Frey, T.K. 2005. Rubella virus capsid protein modulation of viral genomic and subgenomic RNA synthesis. Virology 337, 327-334.
Tzeng, W.-P., Zhou, Y., Icenogle, J., and Frey, T.K. 2005. Novel replicon-based reporter gene assay for detection of rubella virus in clinical samples. Journal of Clinical Microbiology 43, 879-885.
Frey, T.K. 2004. Rubella nonstructural protease. In: Handbook of Proteolytic Enzymes, 2nd Edition, A.J. Barrett, N.D. Rawlings, and J.F. Woessner, eds, Academic Press, Ltd., London, pp. 1272-1273.
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