Development of increased serum immunoblot reactivity against a 45,000-dalton polypeptide of Treponema pallidum (Nichols) correlates with establishment of chancre immunity in syphilitic rabbits.

Rabbits developed chancre immunity 5.0 to 7.5 weeks after intradermal infection with 10(3) Treponema pallidum (Nichols). The serological response against T. pallidum antigen during this 2.5-week period was examined by Western immunoblotting. Sera from rabbits infected for 5.0 weeks contained antibodies against 7 of 13 major T. pallidum immunogens, with strongest binding detected against a polypeptide of Mr 47,000. By 7.5 weeks of infection, syphilitic rabbit sera recognized 10 of 13 antigens; the most evident increase in serological reactivity was directed against a polypeptide of Mr 45,000, suggesting that the development of a strong serological response against this polypeptide correlated with the onset of chancre immunity.