Persistence of pneumonia virus of mice and Sendai virus in germ-free (nu/nu) mice.

The pathogenicity and persistence of pneumonia virus of mice (PVM) and Sendai virus has been studied using germ-free nu/nu mice. PVM was found to infect cells of the bronchial epithelium (and the alveolar wall) of the lungs of germ-free nu/nu mice using the immunoperoxidase technique. The virus was located in the bronchial epithelium for 11 days before elimination, but persisted in the alveolar wall for the duration of the experiment (20 days). After Day 10 a humoral antibody response to PVM was observed which persisted, although at a low level (1 in 40), by haemagglutination-inhibition (HI) testing. Sendai virus in nu/nu mice also infected cells of the bronchial epithelium and this persisted for the duration of the experiment (27 days). The persistence of virus in the bronchial epithelium in relation to lack of humoral antibody is discussed with reference to local secretory antibody production, especially since this does not occur with PVM.