RABBIT MODEL OF LYME BORRELIOSIS - ERYTHEMA MIGRANS, INFECTION-DERIVED IMMUNITY, AND IDENTIFICATION OF BORRELIA-BURGDORFERI PROTEINS ASSOCIATED WITH VIRULENCE AND PROTECTIVE IMMUNITY

dErythema migrans (EM), persistent skin infection, and visceral dissem ination can be induced reproducibly in the adult male New Zealand Whit e rabbit by intradermal injection of as few as 10(3) Borrelia burgdorf eri. EM was found to persist for 7+/-3 d, Skin culture positivity (inf ection) cleared within a mean of 6.7+/-1.4 wk after infection and simi larly visceral infection was not demonstrated after 8 wk; infection-de rived immunity to intradermal challenge was evident 5 mo after initial infection, The extent of the protection against EM and dermal infecti on induced by untreated infection was directly related to the extent o f prior in vitro passage of the B31 strain. Initial infection with as few as 4 x 10(3) B31 passage 4 induced complete protection against EM and skin infection upon subsequent challenge with 4 x 10(7) B31, passa ge 4, Initial infection with B31 passage 27 led to partial protection against EM along with complete protection against skin infection. Init ial infection with passage 47 led to partial protection against EM, bu t conferred no protection against skin infection, Using serum from rab bits fully immune to reinfection, we defined a set of B. burgdorferi p roteins present in virulent B31, but absent in the avirulent American Type Culture Collection B31 strain, termed ''va'' for virulent strain associated, The va proteins of B31 passages 1, 27, and 47 differed str ikingly, thus raising the possibility that these changes may relate in a causal way to the differences in induction of protective immunity o bserved.