The Degradation of the Rhinovirion as Studied By High Resolution Stereo Electron Microscopy
Picornaviruses, a group of small RNA-containing viruses are further divided into two sub-groups, the enteroviruses which are acid stable, and the rhinoviruses which suffer marked loss of infectivity at acid pH. We have found a ninety per cent decrease in infectious titer after subjection to pH 5.5 as compared to the titer of the original material at pH 7. 0. Considerable morphological degradation of the virion, as monitored by electron microscopy, has also occurred by pH 5. 5. It appears that capsid breakdown proceeds through loss of a vertex capsomere group followed by release of the viral genome in the form of a ribonucleoprotein strand (Fig. 1). However, the conventional flattened electron microscopic image produced by these small virus particles makes further interpretation at a high resolution extremely difficult.