Hantaan virus, aetiological agent of Korean haemorrhagic fever, has Bunyaviridae-like morphology.

Spherical to oval particles with a unit membrane and subunit surface structure were demonstrated by negative-contrast staining of supernatant fluids of A-549 cell cultures infected with strain 76-118 of Hantaan virus. The particles had an average diameter of about 95 nm, with a range of 80 to 110 nm. Similar particles were isolated by buoyant density fractionation in sucrose gradients. In four separate experiments, infectivity cosedimented with 95 nm particles at buoyant densities from 1.15 to 1.18 g/ml. Immunoaggregation of the virions was specifically produced by antisera obtained after Hantaan virus infection of man and rabbit. The known physicochemical and morphological properties of these particles are compatible with those generally reported for the Bunyaviridae family of viruses.

In vitro responses of guinea pig peritoneal macrophages to Legionella pneumophila.

Transmission and scanning electron microscopy were used to study the phagocytosis of virulent and avirulent strains of Legionella pneumophila. The interaction between L. pneumophila and peritoneal macrophages from normal guinea pigs or from animals that had survived infection was studied. The virulent strains survived and proliferated within the phagocyte after ingestion by either type of macrophage, whereas the avirulent strain of bacteria was killed by normal macrophages. Although the addition of immune serum enhanced phagocytosis, the outcome was the same as with normal serum.

In vitro interaction between normal cynolmolgus monkey alveolar macrophages and Legionnaires disease bacteria.

The interaction between normal cynomolgus monkey alveolar macrophages and Legionnaires disease bacteria was studied by transmission electron microscopy. After ingestion of Legionnaires disease bacteria, the organisms replicated within macrophages and destroyed the phagocytic cell.

Fat of Coxiella burnetti in macrophages from immune guinea pigs.

The interaction between Coxiella burnetii and peritoneal macrophages obtained from immune guinea pigs was studied by transmission electron microscopy. Phagocytosis and subsequent fate of ingested phase I and II rickettsiae were compared. Phase I rickettsiae were more resistant to phagocytosis than were phase II organisms. Macrophages from phase I- and II-immunized animals were equally capable of phagocytizing rickettsiae. Phase I and II rickettsiae previously treated with normal serum multiplied and destroyed macrophages from guinea pigs that had been immunized with phase II rickettsiae. Phase II organisms were initially suppressed in macrophages from phase I-immunized animals, but eventually multiplied in these cells. In contrast, only phase I organisms were destroyed by macrophages from phase I-immunized animals. Treatment of rickettsiae with immune serum enhanced ingestion by macrophages and potentiated the destruction of organisms by both types of macrophages. The macrophage migration inhibition assay was performed on peritoneal exudate cells from immune animals. Migration of peritoneal macrophages from phase I-immunized guinea pigs was inhibited, whereas macrophages from phase II-immunized animals migrated when cells were cultured in the presence of killed, intact phase I or II C. burnetii.

Electron microscopic study on the interaction between normal guinea pig peritoneal macrophages and Coxiella burnetii.

An electron microscopic study was conducted to explore the interaction between normal guinea pig peritoneal macrophages and phase I and II Coxeilla burnetii previously treated with either normal or immune serum. A comparison was made on the efficiency of phagocytosis and subsequent killing of rickettsiae by macrophages. Both phases of rickettsiae previously treated with normal serum multiplied within phagosomes after phagocytosis with resultant destruction of macrophages. In contrast, suspending rickettsiae in immune serum rendered them more susceptible to phagocytosis and potentiated their destruction within macrophages.