Abstract: A method of producing a vaccine useful in animals which comprises producing a reassortment by gene exchange from an avian influenza A virus parent and an animal influenza A virus parent and then selecting for the reassortant containing two animal surface antigen genes and six avian internal genes by temperature and antibodies.

Abstract: This invention relates to a precursor or intermediate for a rotavirus vaccine to protect infants and young children against diarrhea caused by rotavirus. The invention is the efficient propagation of a strain of human rotavirus type 2 prepared by a method of cultivation by multiple passages in vivo in gnotobiotic piglets and by multiple passages in vitro subsequently in AGMK (African green monkey kidney) cell cultures. Additionally, rotavirus is treated with a biologically active amount of trypsin prior to growth in AGMK cells, and the inoculated cell cultures are centrifuged at a low centrifugal force before incubation.

Abstract: A method and resulting temperature sensitive (ts) recombinants which may be produced by modifying wild-type influenza A viruses by utilization of chemically mutagenized donor viruses possessing ts lesions and shut off temperatures in the area 37.degree.-38.degree. C. Such a recombinant virus has been produced that contains the surface H3 antigen of influenza A/Hong Kong/1968 (H3N2) virus and a temperature-sensitive (ts) lesion derived from a ts mutant of influenza A/Great Lakes/1965 (H2N2) virus. Additional donor viruses include influenza A/Hong Kong/1968-ts-1[A], influenza A double recombinant 10B, and influenza A/Hong Kong/1968-ts-1[E]. When utilized as a vaccine, these temperature-sensitive recombinant viruses have the facility to develop only mild symptoms, but the infection induces complete resistant to influenzal disease produced by challenge with a virulent wild-type virus. The temperature-sensitive donor mutant is prepared chemically by growth of the virus in the presence of 5-fluorouracil (5-FU).