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In vitro Infectivity Assay for Mouse Mammary Tumor Virus
Judith P. Vacquier and Robert D. Cardiff
Proceedings of the National Academy of Sciences of the United States of America
Vol. 76, No. 8 (Aug., 1979), pp. 4117-4121
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/69780
Page Count: 5
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Studies of mouse mammary tumor virus (MMTV) have been impeded by the lack of an in vitro infectivity assay. We have developed a rapid, quantitative in vitro assay for MMTV infectivity based on the detection of positively staining foci by immunoperoxidase. This assay and a 50% end-point titration of MMTV infectivity gave identical virus titers. Infection of a rat hepatoma cell line, a feline kidney cell line, and a normal murine mammary gland cell line by virus from the mouse mammary tumor GR3A cell line was linear with respect to virus concentration. The infectious titers obtained in both homologous and heterologous cell lines were not significantly different, demonstrating a lack of host range specificity. Virus infectivity was inactivated by heating at 55 degrees C and by ultraviolet irradiation. Rabbit anti-MMTV serum neutralized the infectivity with a 50% neutralization end point of 1:5000. Applications of this assay to the study of the immunological, biological, and biochemical characteristics of MMTV are discussed.
Proceedings of the National Academy of Sciences of the United States of America © 1979 National Academy of Sciences