Undergraduate Researcher The Ohio State University, United States
Disclosure(s):
Owen V. Summers: No financial relationships to disclose
Introduction/Rationale: Though an effective HIV vaccine remains elusive, the ALVAC/gp120/alum regimen shows partial efficacy, mediated in part by antibody-dependent cell-mediated cytotoxicity of NK cells. NK cells play a dual role in vaccines: their cytokines support antibody responses, but their cytotoxicity can kill T follicular helper cells, impairing germinal center (GC) reactions and affinity maturation. Our prior work showed that an aryl hydrocarbon receptor (AHR) agonist as an oral adjuvant to ALVAC enhanced splenic NK cell memory and ADCC phenotypes, thought to improve vaccine efficacy. We investigated how this novel adjuvant affects NK cell phenotypes involved in antibody responses to further promote vaccine efficacy.
Methods: Twenty-four age-sex-matched C57BL/6 mice were randomized into four groups: ALVAC, I3C, ALVAC+I3C, and a PBS control. ALVAC-SIV was given intramuscularly at week 0, with an ALVAC-SIV/gp120/alum booster at week 2. Oral I3C was given daily. After sacrifice at week 4, lymphocytes from blood, bone marrow, lung, and spleen were analyzed via spectral flow cytometry. Group differences were assessed by Mann-Whitney U tests; phenotypic clusters by UMAP and FlowSOM; and polyfunctionality by SPICE.
Results: The oral adjuvant with ALVAC enriched CD62L+ NK cells in blood and bone marrow (p < 0.0001), associated with lymph node homing. The NK cells produced less granzyme B (p < 0.0001) but more TNFα and IL-1β (p < 0.01), consistent with B cell support. Polyfunctional analysis shows that these NK cells diversified into multi-cytokine-producing subsets. Together, these findings suggest that the adjuvant reprograms NK cells to promote GC responses and enhance vaccine-induced antibody protection.
Conclusion: This study demonstrates that our novel oral adjuvant reprograms NK cells to favor lymph node homing and cytokine-mediated B cell help, supporting GC responses essential for antibody maturation. These findings highlight the promise of AHR agonists as innovative adjuvants to enhance HIV vaccine efficacy.
