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P754 Quantitation of cytokines in rabbits following tri-antigen vaccine cocktail immunization and T. pallidum challenge
  1. Charmie Godornes1,
  2. Barbara Molini1,
  3. Lorenzo Giacani1,
  4. Alloysius Gomez2,
  5. Darrick Carter3,
  6. Caroline Cameron2,
  7. Sheila Lukehart1
  1. 1University of Washington, Medicine, Seattle, USA
  2. 2University of Victoria, Biochemistry and Microbiology, Victoria, Canada
  3. 3University of Washington, Global Health, Seattle, USA


Background Immunological analysis of primary and secondary syphilis in rabbits and humans suggests that T helper cells mount a vigorous interferon-γ-dominated immune response (TH1) to facilitate macrophage-mediated clearance of T. pallidum. In this study, we used quantitative reverse transcriptase (qRT)-PCR to evaluate post-challenge rabbit cytokine profiles of primary lesions in unimmunized rabbits and rabbits immunized with a tri-antigen vaccine cocktail.

Methods Groups of 8 male New Zealand White rabbits were immunized with a trivalent recombinant antigen cocktail, (N-term of TprK + N- term of Tpr Subfamily I + Tp 0751, emulsified in either of two custom adjuvants containing Natural or Synthetic TLR4 agonists + a natural Mincle agonist). Unimmunized control and immunized animals were intradermally challenged with 105 T. pallidum (Nichols) at each of 10 sites. Lesion biopsies were collected at days 2 and 21 post-challenge. Expression of IFN-γ, TGF-β, p40 IL-12/23, IL-4, IL-2, TNF-α, IL-10, IL-17A, IL-17F, and IL-22 was quantified by qRT-PCR using plasmids containing the target rabbit cytokines sequences, and expression levels were normalized to rabbit HPRT.

Results At day 2, transcripts for IFN-γ, IL-2, IL-17A, IL-17F, and TNF-α were significantly upregulated in both immunized groups (P<0.01) compared to controls, a finding consistent with the development of clinical delayed type hypersensitivity and the induction of a TH1-type immune response at challenge sites. At day 21, the level of IFN-γ was lower in the Natural adjuvant group (P<0.02), compared to controls, consistent with enhanced treponemal clearance in that group.

Conclusion In the development of a syphilis vaccine, it is important to determine correlates of protection to allow for assessment of the induction of a protective immune response. Our results demonstrate a robust immunization-induced TH1 and TH17 proinflammatory response in immunized rabbit groups, which suggests an effective level of resistance conferred by immunization with the trivalent protein vaccine.

Disclosure No significant relationships.

  • syphilis
  • Treponema pallidum
  • prevention
  • intervention and treatment

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