Ankudas, Milda M. (University of Illinois, Chicago) and Newton Khoobyarian. Rabbit heart cell cultures, strain RHF-1. II. Behavior of adenovirus types 1 to 4. J. Bacteriol. 84:1287-1291. 1962.-In general, the findings indicate that adsorption to RHF-1 cells of adenovirus types 1, 2, and 4, but not type 3, precedes the events leading toward virus multiplication. Adenovirus type 3 attained maximal adsorption (90%) in 2 hr, with no evidence of virus multiplication. Under optimal conditions in the present experiments, the type 1 virus appeared to be released from the infected cells at a much slower rate than types 2 and 4. No correlation seemed to exist between the extent of cytopathic changes produced by type 1 in RHF-1 cells and the rise in virus infectivity during the logarithmic phase. On the other hand, the progression of cytopathic effect of type 2- and type 4-infected cells appeared to be a direct result of virus propagation. Further-more, the relative yield of virus per host cell, though small in quantity, was more or less similar for all three types. Histopathologically, no marked difference among the cells infected with types 1, 2, and 4 was clearly evident. Upon serial subculturing of these viruses in RHF-1 cells, a concomitant decrease in infectious virus, as well as complement-fixing antigen titers at each passage level, was also noted.