Studies on immunity in experimental syphilis. 2. Transfer of antibodies to the fetus in rabbits

Abstract

Female rabbits were injected intravenously with Treponema pallidum (Nichols strain) and bred after the infection became manifest. After parturition, the offsprings were examined on their circulating antibodies for syphilis by the cardiolipin slide test (VDRL) as well as the Treponema pallidum immobilization test (TPI). Immediately after birth, serum specimens from the young were invariably positive in both tests. In most cases, however, the VDRL antibody disappeared rapidly and became negative after 3 weeks, while the TPI antibody vanished gradually and were negative 3 to 4 months after birth, with few exceptions. Few offsprings, however, showed continuously a high TPI titer for more than 4 months. The offsprings were then inoculated intradermally with the treponema 4 months after birth. A typical skin lesion which is characteristic of the primary infection was observed in the young whose treponemal antibody disappeared spontaneously, while the offsprings with TPI antibody resisted completely to the infection as was always the case with the syphilitic rabbit.These results indicated that the treponemal antibodies in the young from infected females were derived from the maternal antibody without actual infection of the fetus in utero. However, evidence of the intrauterine infection of the fetus was also confirmed, although such cases were very rare.