title: [Early stages in the replication of aphthous fever virus. Kinetics of partial degradation and sites for the establishment of penetrating residual virus].
abstract: At input multiplicities between 5-10 UFP/cell FMDV O1 Caseros adsorb in BHK21 Clon 13 cells at a rate of 5-20% depending whether cells are in suspension or in monolayers. At least four washings with medium are required to eliminate non specifically adsorbed virions. The remaining attached virus appears to be in contact with "specific" receptors of the cytoplasmic membrane. After penetration, 80% of virus became degraded to slow molecular weight material which is detected at first in the subcellular fraction and is gradually excreted out of the cells. The degradation process occurs from 0 to 15 minutes and it is demonstrated by a parallel decrease in infectivity and stability of purified labelled FMDV O1 Caseros. The 20% remaining virus is found firmly attached to a subcellular fraction precipitable at 15,000 xg. Parental residual infectivity remains remarkably stable for 90 min at which time newly synthetized RNA appears. Fraction of 15,000 xg from infected cultures was obtained at 60 min PI and incubated in vitro at 37 C. The infectivity remains unaltered for a period of 120 min even if the preparation is treated with 0.2% of triton x 100. Fraction of 15,000 xg from infected and control cultures obtained at different time PI were seeded on a linear sucrose gradient. A sharp peak of acid phosphatase associated with the lower mobility bands indicates the presence of intact lysosome structures. A shoulder of the enzyme activity is detected between the two main protein bands. Associated with the region rich in unbroken lysosomes, a very sharp peak of infectivity and/or 3H uridine or 32P labelled incoming virus can be detected. A different pattern of the residual incoming infectivity is found associated with the more rapid sedimentation protein band. 3H uridine incorporation at the beginning of viral RNA synthesis initiation shows that an important amount of newly synthesized viral RNA is found in the lower mobility band of the 15,000 xg fraction. Some incorporation is also detected in the faster band. The results presented here suggest that some functional activity is associated with the residual virus present at the beginning of infection in the 15,000 xg fraction. It can also be accepted that this virus penetrates by pinocytosis of specific receptors at the cytoplasmic membrane.
mesh_terms: D000818:Animals; D005537:Aphthovirus / Q000302:isolation & purification / Q000502:physiology*; D002460:Cell Line; D006224:Cricetinae; D005347:Fibroblasts / Q000382:microbiology; D007668:Kidney; D007700:Kinetics; D008647:Mesocricetus; D012367:RNA, Viral / Q000096:biosynthesis; D013347:Subcellular Fractions / Q000382:microbiology; D014776:Virus Cultivation; D014779:Virus Replication
chemical_list: D012367:RNA, Viral
vernacular_title: Etapas tempranas en la replicación del virus de la fiebre aftosa. (VFA). Cinética de la degradación parcial y sitios de estabilización del virus penetrante residual.