A synthetic lymph node containing inactivated Treponema pallidum cells elicits strong, antigen-specific humoral and cellular immune responses in mice.

The goal of this study was to investigate the use of a synthetic lymph node (SLN) for delivery of Treponema pallidum (Tp) antigens. Immune responses of C57BL/6 mice were analyzed at 4, 8, and 12 weeks after SLN implantation. Group 1 mice received SLN with no antigen; Group 2, SLN with formalin-inactivated Tp (f-Tp); and Group 3, SLN with f-Tp plus a CpG oligodeoxynucleotide. When tested by ELISA, sera from Group 2 and Group 3 mice showed stronger IgG antibody reactivity than sera from Group 1 mice to sonicates of f-Tp or untreated Tp, but not to sonicate of normal rabbit testicular extract at all times. The IgG1 level was higher than IgG2c level for Group 2 mice at all times and for Group 3 mice at 4 and 8 weeks. IgG1 and IgG2c levels were nearly equivalent for Group 3 mice at 12 weeks. Immunoblotting showed that IgG from Group 2 and Group 3 mice recognized several Tp proteins at all times. Supernatants of splenocytes from Group 2 and Group 3 mice contained significantly more IFNγ than those from Group 1 mice after stimulation with f-Tp at all times. A significant level of IL-4 was not detected in any supernatants. These data show that strong humoral and cellular immune responses to Tp can be elicited via a SLN.