The Development of a Cold Adapted Influenza Virus A/Taiwan/1/30/86(H1N1)

The influenza A/Taiwan/1/30/86(H1N1) (A/Taiwan/30) cold- adapted virus, expressing the ability to reproduce at 29℃ and inability to reproduce at 37℃ (the ca phenotype), was successfully established by repeated passages at progressively lower temperatures in our laboratory. This strain is phenotypically stable and attenuated for mice. When the cold-adapted virus suspension was diluted to 3.2 10^(-6) HAU/ml and inoculated (0.1 ml of the virus suspension per chicken embryo) into the allantoic cavity of 10-day old chicken embryos, virus replication can only be detected in those cultures incubated at 29℃ but not at 37℃ On the other hand, we found that sera from various animal species somehow contained hemagglutination inhibition substances (HISs), exhibiting an inhibitory effect on the hemagglutination of influenza virus A/Taiwan/1/86(H1N1), which could be destroyed by the receptor destroying enzymes (RDEs). This result suggests that the chemical nature and the conformational structure of these HISs may be similar to those hemagglutinin receptors on the permissive erythrocytes and can be recognized and destroyed by the RDEs.