Intracellular Forms of Meningopneumonitis Virus

Abstract

Viruses belonging to the psittacosis-lymphogranuloma group have morphological peculiarities which have made them the subject of controversy for many years. They are so large that the desirability of including the group with the viruses has often been questioned. Bedson and his colleages (1-4) described a life cycle for the virus of psittacosis based on the observation of intracellular forms even larger than the elementary bodies. These structures appeared as a graded series of spheres in the cytoplasm, suggesting a high degree of organization and, possibly, binary fission at some stage of development. Dense cytoplasmic inclusions (plaques, morulae) were often associated with the spherical forms.A number of investigations of the morphology of psittacosis and other members of the group have been reported, and the problem was reviewed recently by Meyer (13). I t was felt that a study by means of electron microscopy of virus-infected tissues should provide new information. Consequently, chorioallantois infected with meningopneumonitis virus, a representative member of the psittacosis-lymphogranuloma group, was selected for examination at the electron microscopic level. MethodsInoeulationl.--An allantoic fluid suspension of the "Cal 10" strain (18) of meningopneumonitis virus was inoculated on the chorioallantoic membrane of 12 day eggs. The virus was from the llth egg passage (allantoic cavity) and a heavy dose (0.5 ml. of undiluted fluid having a titer in mice greater than 10 -7) was used in order to have a large number in initially infected cells. Electron microscopic observations of normal membranes were made and described in an earlier study (8).Harvest and Fixation. Girardi, and Allen (18) showed that new virus appeared sometime between 24 and 48 hours after the inoculation of this strain of virus into the al-* Aided by Grants from the Jane Coffan Childs Memorial

Structure and Replication of the Trachoma Agent in Cell Cultures, as shown by Electron Microscopy

“…Already in several laboratories workers have turned to electron microscopy in the hope that greater resolving power would be decisive in the vexed question of taxonomic relationships. Thinsection studies have been made of cells infected with the agents of meningopneumonitis (Gaylord, 1954;Tajima, Nomura & Kubota, 1957;Higashi, 1959), feline pneumonitis (Litwin, 1959), psittacosis (Litwin, Officer, Brown & Moulder, 1961) and trachoma (Mitsui et ul, 1958). Materials examined included tissues of infected animals and embryonated eggs, as well as inoculated cell cultures; but in terms of advancing previous knowledge the outcome has been inconclusive.…”

Internal Structure of Rickettsia burnetii as shown by Electron Microscopy of Thin Sections

“…Animal viruses have been examined in thin sections of infected tissue. Vaccinia and fowl-pox viruses are oval with a single or double limiting membrane and an eccentrically placed inner body (Gaylord & Melnick, 1953;Morgan, Ellison, Rose & Moore 1954b); herpes virus is round or oval with a central body and one or two membranes probably depending upon the stage of development and the position in the cell (Morgan, Ellison, Rose & Moore 1954 a ) ; elementary bodies of meningo-pneumonitis virus are dense with central granules, but large circles with no internal granules are also seen in sections of infected tissue (Gaylord, 1954).…”

Morphology of Viruses

“…The identification of the larger and more diffuse sacs which have no distinctive morphology, as part of the virus cycle, is much more difficult. These larger forms may correspond in some way to the "plaques" which have been described previously by light microscopists, and Gaylord's studies (13) of sections of infected membranes show such large sacs within the infected cells. However, sac-like extrusions from the cell are seen in other virus infections of the chorioallantoic membrane (14) and probably are an accompaniment of degenerating cells (15 blebs.…”