Experimental infection of inbred guinea pigs with Treponema pallidum: development of lesions and formation of antibodies.

Inbred strain 2 and strain 13 guinea pigs were infected intradermally in the hind legs with different numbers of the virulent Nichols strain of Treponema pallidum. About 91% of the animals developed clearly visible lesions after being injected with 5 X 10(6) to 10 X 10(6) treponemes. T pallidum organisms could be isolated from skin lesions at various stages after infection. Infected animals were monitored for the production of specific treponemal and non-specific cardiolipin antibodies by the fluorescent treponemal antibody (FTA) and microhaemagglutination (MHA-TP) tests and the rapid plasma reagin (RPR) card test. Low levels of specific antibodies could be detected by both FTA and MHA-TP tests from three to four weeks after infection. Maximum titres of treponemal antibody generally occurred after week 6 and persisted for several more months. These peak titres ranged from 1/40 to 1/80 in the FTA test and 1/160 to 1/320 in the MHA-TP test. During the same period infected guinea pigs, unlike rabbits with syphilis, did not produce detectable quantities of antibodies against cardiolipin.