David H. Carver

Hemadsorption-Negative Plaque Test: New Assay for Rubella Virus Revealing a Unique Interference tion-negative plaque technique

A simple and rapid plaque procedure has been developed for detecting and accurately assaying rubella virus in a noncytopathic virus-cell relationship. Plaque-formation is based on the development, in individual cells infected with rubella virus, of a unique type of intrinsic interference to infection with Newcastle disease virus. Rubella virus—infected cells challenged with Newcastle disease virus and tested for hemadsorption 15 hours later stand out as hemadsorption-negative areas. Individual living cells infected with rubella virus can be resolved under conditions allowing standard cloning procedures. In principle, the hemadsorption-negative plaque test can be used to search for a new class of noncytopathic, non-hemadsorbing viruses—those that induce an intrinsic interference to infection by any hemadsorbing virus.

Interferon production and action in mouse, hamster and somatic hybrid mouse-hamster cells.

A hybrid mouse-hamster cell line was developed from a mouse cell line which produces a high titer of interferon and is sensitive to its action, and a hamster cell line which produces little interferon and is relatively insensitive to its action. Parental cell lines demonstrated complete species specificity with respect to interferon production and action. The hybrid cells produced interferon (or interferons) effective when tested on the mouse cell line and primary hamster cells; the hybrids were sensitive to the action of both mouse and hamster interferons. Hybrid cells produced ten times more hamster interferon than the parent hamster cell line and were eight times more sensitive to hamster interferon than the parent hamster cell line.