VIRUS BIOGRAPHIES. I. GROWTH OF WEST NILE AND GUAROA VIRUSES IN TISSUE CULTURE.

Southam, Chester M. (Sloan-Kettering Institute for Cancer Research, New York, N.Y.), Frederick H. Shipkey, Virginia I. Babcock Roller Bailey, and Robert A. Erlandson. Virus biographies. I. Growth of West Nile and Guaroa viruses in tissue culture. J. Bacteriol. 88:187-199. 1964.-Monolayer tissue cultures of HEp 2 cells (human epidermoid carcinoma) were inoculated with Guaroa or West Nile viruses. At daily intervals for 4 days thereafter, these cultures were studied by (i) light microscopy of living cultures and stained cultures, (ii) intracerebral inoculation of mice to titrate infectivity, (iii) acridine orange stain to observe nucleic acid changes, (iv) fluorescein-labeled antibody technique to observe specific viral antigen, and (v) electron microscopy to observe virus particles. Guaroa virus infectivity increased progressively over the 4-day period, and caused definite cytolysis by day 3. Cytoplasmic ribonucleic acid (RNA) staining was increased by 24 hr, and by 48 hr the RNA formed globular masses, particularly in degenerating cells. Viral antigen was occasionally seen on day 1, and increased progressively thereafter, forming numerous sharply outlined particles in cytoplasm concentrated at the cell membrane. Virus particles were ellipsoids with a dense nucleoid and a single membrane approximately 70 by 90 mmu, which appeared to form at the cell membrane just before being discharged. West Nile virus infectivity increased sharply between 1 and 2 days, but caused little cytolysis even by 4 days. Cytoplasmic RNA staining increased progressively for the 4 days, usually forming a large juxtanuclear mass in each affected cell. Viral antigen was not detected on day 1, but increased progressively thereafter, forming a crescent or a single diffuse mass adjacent to the nucleus. Virus particles were spheres approximately 30 mmu in diameter, with a dense nucleoid and a single membrane. They appeared to form in granular foci in the cytoplasm and then to fill the channels of the endoplasmic reticulum. No significant nuclear changes were observed with either virus by any of these techniques.