Purification and properties of a chlamydial hemagglutinogen

A hemagglutinogen was isolated from the soluble antigens of a 6BC strain of psittacosis grown in cell culture. The antigen, which was purified by chromatography and electrophoresis, has a molecular weight of 100 000 to 120 000 and a density of 1.235 at 4 °C. The serologic activity of the hemagglutinogen was not affected by acid hydrolysis but was decreased by neuraminidase treatment. It reacted more strongly with homologous than with heterologous antiserum, which might suggest the presence of more than one antigen in the preparation not separable on the basis of molecular weight, density, or electro-phoretic mobility in polyacrylamide gel. A possible alternative explanation would be the presence of a group- and type-specific activity on the same molecule.

Inapparent respiratory infection of inbred Swiss mice with sulfadiazine-resistant, iodine-negative Chlamydiae

Three chlamydial strains were isolated from the lungs of three different strains of mice that were inbred for over 30 years. These chlamydial strains were resistant to sulfadiazine and did not induce iodine-positive, glycogen-like material in the inclusions of infected L cells which characterizes them as Chlamydia psittaci.

Electron microscopic studies of the rickettsia Coxiella burneti: entry, lysosomal response, and fate of rickettsial DNA in L-cells

The rickettsial agent Coxiella burneti was studied in cultured mouse L cells by use of the electron microscope. Rickettsiae gain entry to the host cell in an apparently passive manner through phagocytic activity by L cells. The L cells show a lysosomal response to the presence of rickettsiae, as determined by cytochemical tests for acid phosphatase and 5′-nucleotidase. Further, examination of C. burneti within lysosomes suggests that rickettsiae can be degraded by the host cell. Autoradiographic analyses using tritiated thymidine show that rickettsial DNA is largely restricted to the dense nucleoid region, and when such labeled rickettsiae are used to inoculate L cells, most of the label becomes localized in the host cell nucleus. The above information is discussed in terms of dynamic interactions between C. burneti and infected L cells.

Interferon action: effect on the formation of poxvirus specific polysomes and viral RNA

Treatment of chick embryo fibroblast cells or mouse L-cells with homologous interferon resulted in a reduced formation of poxvirus specific polysomes and of viral RNA. In chick cells infected with cowpox virus the reduced formation of viral polysomes and virus-specific RNA after pretreatment of cells with interferon was observed at all timepoints studied (1 - 6 hours p. i.). Exposure of cells to poly I: poly C caused a similar effect. In mouse L-cells infected with vaccinia WR virus pretreatment with interferon did not result in a reduced formation of viral polysomes or virus-specific RNA up to 1 hour p. i. At about 45 min even a slight increase of the formation of viral polysomes and RNA was observed. At later stages of infection (2 -4 hours p. i.) a reduced synthesis of viral polysomes and RNA was seen, similar to that found in the chicken fibroblast system.

Properties of RNA transcriptase in reovirus subviral particles

Subviral particles containing reovirus RNA transcriptase have been isolated from extracts of virus-infected mouse fibroblast cells. The purified particles which lacked the outer protein capsomeres of the mature virion had a buoyant density of 1.43-1.44 g/ml in CsCl and contained all of the double-stranded RNA genome of the intact virus. The particles were free of nuclease activity. RNA synthesis required all four ribonucleoside triphosphates and was dependent on magnesium or manganese; optimal activity required potassium or ammonium ions. In the presence of a ribonucleoside triphosphate regenerating system, reaction rates were linear for 20 hr. RNA yields of 40-fold in excess of input template could be obtained. Completed RNA chains were released from the subviral particles. In the course of RNA synthesis, the double-stranded RNA template was fully conserved. The RNA products formed in vitro displayed profiles in sucrose gradients similar to those found for in vitro reovirus mRNA. The RNA products were single-stranded and did not self-anneal. Over 90 percent of the transcriptase products could be annealed with template double-stranded RNA. The annealed products migrated in acrylamide gels as double-stranded RNA, indicating efficient in vitro transcription.