title: Trypsin action on the growth of Sendai virus in tissue culture cells. I. Restoration of the infectivity for L cells by direct action of tyrpsin on L cell-borne Sendai virus.
abstract: Sendai virus grown in fertile eggs (egg Sendai) infects L cells in which the synthesis of L Sendai (grown in L cells) occurs by the one-step mechanism. L Sendai is not infectious for L cells when tested by the tube titration method although it is infectious for chick embryos. When L cells infected with egg Sendai were dispersed by trypsin and plated on a monolayer culture of L cells, the viral agents spread to the adjacent recipient cells in which the synthesis of L Sendai occurred. The newly infected L cells became infectious for L cells again by trypsin treatment. Kinetic experiments suggested that the target of trypsin is the mature virus, of L Sendai nature, just budding from the L-cell surface. By using an immunofluorescent cell-counting technique, recovery of the infectivity of L Sendai for L cells due to a direct enzymatic action of trypsin was demonstrated. Under the optimal condition, the infectivity increased 1,000-fold for L cells and 10-fold for chick embryos, and both the titers could favorably be compared. No increasing effect of trypsin was observed on the infectivity of egg Sendai. Density centrifugation studies revealed a difference between egg Sendai and L Sendai in the density. Trypsin treatment which induced the maximal enhancement of L Sendai infectivity did not affect both the densities, showing that variations of Sendai virus in the infectivity for L cells and in the density are independent types of host-controlled modification.
mesh_terms: D000818:Animals; D002452:Cell Count; D002499:Centrifugation, Density Gradient; D002642:Chick Embryo; D046508:Culture Techniques; D003588:Cytopathogenic Effect, Viral; D005455:Fluorescent Antibody Technique; D005615:Freezing; D014644:Genetic Variation; D005827:Genetics, Microbial; D006382:Hemadsorption; D006389:Hemagglutinins, Viral / Q000378:metabolism; D007106:Immune Sera / Q000494:pharmacology; D007739:L Cells; D010222:Parainfluenza Virus 1, Human / Q000187:drug effects / Q000254:growth & development / Q000276:immunology / Q000472:pathogenicity*; D011188:Potassium; D011817:Rabbits; D013644:Tartrates; D013997:Time Factors; D014357:Trypsin / Q000494:pharmacology*; D014361:Trypsin Inhibitors / Q000494:pharmacology
chemical_list: D006389:Hemagglutinins, Viral; D007106:Immune Sera; D013644:Tartrates; D014361:Trypsin Inhibitors; D014357:Trypsin; D011188:Potassium