Adaptation of Influenza B Virus to Mice by Use of Certain Adjuvants. ∗

Abstract

Summary and conclusions

The addition of a variety of bacterial cell suspensions, cell extracts, or non-bacterial substances to influenza virus, strain IB45, preparations at each passage in mice apparently aided the initially non-virulent virus in such a manner that it could establish itself in the mouse lung and propagate through repeated mouse passage. This addition of adjuvant had to be repeated at each passage for 4 to 8 passages, after which extensive lesions and regular deaths occurred in mice. At this time the adjuvant could be omitted and the virus would continue to propagate. Single addition of adjuvant at the first passage was not sufficient for the virus to establish itself in the mouse, since the virus disappeared after 3 passages. Virus alone was never present after the third passage in mice. There is no evidence that any one of the preparations possessed greater action than the others, although the addition of killed bacterial cells seemed to give somewhat more rapid adaptation of the virus in the mouse than cell extracts or non-cellular substances. An influenza B virus that was initially non-infective for mice became infective when certain addjuvants of bacterial or non-bacterial origin were added to each passage of virus. A procedure such as this may be useful in the isolation and adaptation of influenza viruses in mice.