Molecular Mechanisms and Practical Use of Attenuated Viruses

Abstract

Cross protection is a phenomenon whereby prior infection with one virus (the primary virus) prevents or interferes with subsequent infection by another isolate of the same virus or a closely related virus (the secondary virus), suggesting that cross protection using attenuated viruses appears to offer a promising strategy for biological control of plants viral diseases. A few attenuated viruses have been commercially used as a “vaccine” in Japan. Because cross protection is effective in general, it is necessary to increase good attenuated strains against many severe viruses. To study the underlying molecular mechanism, it is essential to know how the attenuated isolate differs in genome structure from the original virulent isolate.