(921) A STING-agonist Conjugate Vaccine Potently Synergizes with admixed QS-21 liposomes and CpG to Elicit Robust Th1 Immunity against Chlamydia in mice
Graduate Student Univ. of North Carolina, Chapel Hill, United States
Disclosure(s):
Emily Hand: No financial relationships to disclose
Introduction/Rationale: Chlamydia trachomatis (CT) is the most common bacterial sexually transmitted infection and can cause pelvic inflammatory disease and infertility in women. CT vaccine development has been hindered by a lack of safe adjuvants that elicit high frequencies of IFNγ⁺ memory CD4 T cells (Th1) required for protection. Our lab developed a novel subunit vaccine consisting of the immunodominant Chlamydia protease-like activity factor (CPAF) antigen conjugated to a novel STING agonist CL1151 (CPAF-CL1151), that induces a protective Th1 response in mice. We hypothesized the addition of QS-21 liposomes and/or a TLR9 agonist (CpG1826) with CPAF-CL1151 would synergistically enhance Th1 immunity against Chlamydia.
Methods: C57BL/6 mice were immunized intramuscularly (i.m.) or via combined i.m. and intranasal (i.n.) route with different adjuvant combinations (-CL1151± QS-21±CpG). CPAF-specific T cell responses were determined by IFNγ ELISpot, ELISA, and ICS. THP-1 derived macrophages were stimulated with CPAF-CL1151, QS-21, or both and cytokine secretion quantified by ELISA.
Results: ELISpot showed mice vaccinated i.m with -CL1151+QS-21 had a 2-fold increase in splenic IFNγ⁺ CD4 T cells compared to -CL1151 (p < 0.001), and an 8-fold increase compared to QS-21 (p < 0.0001). The triple-adjuvant vaccine (-CL1151+QS-21+CpG) delivered i.m + i.n enhanced the frequency of IFNγ⁺ CD4 T cells by 2-fold (p < 0.01) and induced a 6-fold increase in IFNγ secretion by splenocytes upon CPAF restimulation (p < 0.01) over -CL1151+QS-21 . In THP-1 macrophages, -CL1151 + QS-21 had >10-fold increases in IFNβ, IL-6, and IL-1β secretion relative to individual adjuvants, indicating activation of interferon and inflammasome pathways.
Conclusion: These data highlight the Th1 synergy of TLR, saponin, and STING adjuvants and demonstrates the potential of multi-adjuvant vaccines against intracellular bacterial pathogens. Future studies will define the synergistic molecular and cellular pathways underlying this protective CD4 T cell immunity.
