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UBC Theses and Dissertations

A Conserved epitope on the surface of carlaviruses Wieczorek, Andrew A.


The seed certification program in British Columbia relies heavily on double antibody sandwich-enzyme-linked immunosorbent assays (DAS-ELISA) for detection of plant pathogens. Each individual sample requires a separate test for each pathogen. The aim of this research was to simplify the procedure, which would result in considerable savings in both cost and labour. A method to facilitate the testing by allowing several individual samples to be evaluated in a single trial was developed by finding a unique antibody that could be used for the detection of several viruses. A monoclonal antibody was raised to the coat protein of potato virus M which also reacted to other members of the carlavirus group. Viruses morphologically similar to carlaviruses but belonging to the potyvirus and potexvirus groups were also challenged with the PVM antibody, but failed to react, despite evidence of conserved amino acid sequences in the coat proteins of carlaviruses and potexvirus. A variety of host species infected with viruses from all three groups were also tested to eliminate the possibility of a reaction by the antibody to a plant component. Partial characterization of the epitope to which the antibody reacts was also accomplished. It is postulated that the epitope is conformational in nature, since the antibody fails to detect coat protein subunits in Western blots, and does not react to virus degraded by long-term storage either in purified form or in tissue. Since the epitope readily reacts in DAS-ELISA, it was concluded that the antigenic site must be located on the surface of the virus particle. This is the first demonstration of an epitope that shows broad specificity within a virus group which is located on the surface of the virus rather than buried in the viral core. The utilization of this epitope for diagnostic purposes is discussed.

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