Restoration of the infectivity of Rickettsia tsutsugamushi to susceptible animals by passage in athymic nude mice.
Restoration of the infectivity of three prototypes of Rickettsia tsutsugamushi (i.e., Gillium, Karp and Kato strains) was examined to obtain each antiserum for the diagnosis of rickettsiosis and to prepare target antigens. When successively passed in embryonated yolk sac, rickettsiae gradually lost their infectivity to susceptible animals; after several passages in mice only Kato strain retained infectivity and others became completely avirulent. When these strains were passaged in athymic nude mice only once, they restored even stronger infectivity than original ones to other animals. The infectivity was retained in further passages in BALB/c, DDD mice or in guinea pigs. Thus excellent strain specific antisera were produced in guinea pigs, enabling defined diagnosis of rickettsial infection. Furthermore, successful restoration of the infectivity is expected to contribute to the studies on pathogenesis of rickettsiosis.
D000818:Animals; D001431:Bacteriological Techniques; D008297:Male; D051379:Mice; D008819:Mice, Nude; D012285:Orientia tsutsugamushi / Q000472:pathogenicity*