ROTAVIRUS DISEASE, BUT NOT INFECTION AND DEVELOPMENT OF INTESTINAL HISTOPATHOLOGICAL LESIONS, IS AGE RESTRICTED IN RABBITS

The rabbit model of rotavirus infection has proved to be useful for as sessing active immunity and protection after infection or vaccination with virus or virus-like particles. One limitation of the rabbit model is that after experimental infection of rabbits, clinical diarrhea is not routinely induced. Lack of diarrhea in the rabbit model has been proposed to be due to the fluid absorptive capability of the cecum or attenuation of virus strains through tissue culture adaptation. To tes t whether a wild-type lapine rotavirus strain SAP (BAPwt) isolated fro m diarrheic rabbits would cause disease on passage in rabbits. 1-, 2-, 10-, and 18-week-old rabbits were orally inoculated with BAPwt, its t issue culture-adapted counterpart strain (BAP-2), tissue culture-adapt ed lapine strain ALA, or PBS. Lapine rotavirus infection in 1-week-old , but not greater than or equal to 2-week-old, rabbits resulted in the development of disease characterized by soft, wet, yellow-to-brownish -green partially formed-to-liquid stools observed only at the time of virus antigen shedding. The level and duration of virus shedding after infection were prolonged in 1-week-old rabbits compared with rabbits greater than or equal to 2 weeks of age. Although diarrhea was not obs erved beyond the first 2 weeks of life, histopathological changes, inc luding villus shortening and fusion, increased vacuolation of epitheli al cells, and mononuclear infiltration of the lamina propria, were obs erved throughout the small intestine between 12 and 120 h after ALA in fection in 1-week-old, 1- to 2-month-old, and 11-month-old rabbits. In 11-month-old rabbits, onset of intestinal damage appeared to be sligh tly delayed, was less severe, and was not observed in the duodenum. Th ere were no differences in the immune responses to rotavirus infection in rabbits of different age groups (1 week to 5 years of age). All ra pine rotavirus-inoculated rabbits seroconverted and were protected fro m virus challenge at 28 days postinoculation. Like in mice, rotavirus disease is age restricted in rabbits. (C) 1998 Academic Press.