[Intranasal infection of ICR mice with herpes simplex virus type 1]

Intranasal inoculation of mice with herpes simplex virus (HSV) provides a model of human herpetic infection through a natural route of inoculation. Five-week-old male ICR mice were infected intranasally with various strains of herpes simplex virus type 1 (HSV-1), and the fundamental aspects of the pathogenicity of this virus were studied. Six virus strains examined showed variance in their virulence determined by lethal dose 50 (LD50) for mice. Four of the strains were revealed to be virulent, and two were shown to be attenuated. The relative degree of virulence among these strains corresponded well to that shown by intraperitoneal inoculation. When mice were inoculated with a virulent virus strain (F), virus multiplication was shown clearly in several organs tested, such as the lung, brain, olfactory bulb, trigeminal ganglion, spinal cord and adrenal gland. Viremia was also demonstrated. On the other hand, in mice inoculated with an attenuated virus strain (-GCr), virus was recovered only from the lung and adrenal gland and in much less amount than in the respective organs of mice infected with the virulent strain. No viremia was demonstrated. These data strongly suggest that the lethal effect of HSV-1 on mice is dependent upon whether or not significant virus multiplication occurs in the central nervous system, which is the critical target organ of HSV. Preinoculation of mice with an attenuated strain via the intranasal route suppressed the lethal effect of subsequent infection with any of the virulent strains by the same route of inoculation, although this protection phenomenon was not so pronounced when the virulent UNO-1A strain was used.(ABSTRACT TRUNCATED AT 250 WORDS)