Transient Sensitivity of Intracellular Psittacosis Virus to X-rays

Abstract

MEMBERS of the psittacosis-LGV group of micro-organisms replicate through a series of cytochemically defined reactions, as visualized by fluorescence microscopy of infected cells stained with acridine orange¹. The replication cycle can be described as follows: (a) the viral particle (DNA-staining, green) penetrates into the cytoplasm; (b) in response to invasion, the host-cytoplasm contributes a matrix (RNA-staining, red-orange) resulting in a ‘red-ball’ inclusion; (c) the inclusions increase in size and number; (d) undergo a sequence of colour changes from shades of red to orange to yellow to green. Inclusions at the yellow-green stage contain mature, infectious virus in contrast to those at the red-orange stage. These cytochemical changes are dynamic and predictable. Drugs which inhibit the replication process of virus do so by interference with the sequence of replication. Thus, this intracellular indicator system has been applied to investigations of the mechanism of action of fluorinated pyrimidines², p-fluorophenylalanine³, aminopterin⁴ and antibiotics⁵.