A Virus Disease of Swiss Mice Transmissible by Intranasal Inoculation

Abstract

Mice have been extensively employed in the study of the virus of human influenza since the discovery by Andrewes, Laidlaw, and Smith, 1 and by Francis 2 that these animals are susceptible to intranasal inoculation of ferret-passed virus. Francis3 has recently shown that influenza virus cultivated in the chorio-allantoic membrane of the developing chick embryo is pathogenic for mice and does not require ferret passage to raise its virulence. Many of the immunological studies of influenza virus have been made by means of protection tests using mice as test animals. It is obvious, therefore, that if the virus of the common cold could be made virulent for mice, a similar and valuable immunological study of this virus could be made.

After a number of preliminary failures in attempts to infect mice by intranasal inoculation of the virus of common cold, we began, during the summer of 1936, to use virus for inoculation which was being cultivated in the chorio-allantoic membrane of the chick embryo. By this means, with comparatively little difficulty, 3 different strains of virus were established in mice and could be passed in series by intranasal inoculation of emulsions of infected lung. After the few passages necessary to establish the strains, all 3 produced fairly uniform lesions in the lungs. The mortality rate was much less than that reported for human influenza virus, only about 10% of the mice dying in 4 or 5 days. About 75%, however, showed fairly extensive pulmonary consolidation at autopsy. The areas of pulmonary consolidation were plum colored, often involving a whole lobe, and their gross appearance closely resembled that seen in mice infected with human influenza virus. The serological relationship to one another of the 3 strains of common cold virus was studied by means of protection tests in mice.