CD40LG and syphilis: For example, syphilis-specific IgM cn be detected as early as 2 weeks after infection,[2] nontreponemal antibodies can be detected 5 to 7 weeks after initial infection, and both of these are generally correlated with disease activity.[3] The rabbit infectivity test (RIT) is another method used to establish infection with viable Treponema pallidum, and it has historically been considered as the gold standard for detecting active syphilis.