The fine structure of inclusion bodies and the morphological changes of VERO cells (monkey kidney cell line) infected with Edmonston strain of measles virus were examined in the electron microscope and localization of viral antigen was followed by means of ferritin-conjugated antibody method. And the following results were obtained.
1) In the nuclear inclusion area, randomly arrayed tubular structures with frequent ordered arrays were recognized. The cytoplasmic inclusion was also consisted of an aggregate of randomly arrayed tubular structures. The tubular structure in the cytoplasmic inclusion was twice wider than that in the nuclear inclusion, having approximate diameter of 30 to 40mμ. The exact nature of these tubular material remains undetermined.
2) Many of the infected cells which contained cytoplasmic inclusion developed a lot of tiny cytoplasmic processes and spherical bodies on and outside the cell wall. In general, most of the spherical bodies had dense outer membrane but they were varied in size, shape and internal structure.
3) Measles virus antigen was demonstrated on the surface of the spherical bodies and cytoplasmic processes. It was hardly possible to identify mature virus particle because the spherical bodies were markedly pleomorphic. The spherical bodies and cytoplasmic processes with dense outer membrane containing viral antigen would be intimately related to the maturation and release of measles virus.
