Intra-Lymph Node Delivery Of Macroparticles Loaded With Rapamycin In Non-Human Primates

Introduction: Lymph nodes (LNs) are key tissues that coordinate adaptive immune responses. Our team has shown the immunomodulatory potency of intra-lymph node (iLN) injection of engineered micrometer-scale synthetic microparticle particles (MPs) loaded with antigens and rapamycin (Rapa) in murine models, but this approach has not previously been evaluated in non-human primates. Materials and Methods: Four Cynomolgus monkeys received a bilateral injection of iLN-MPs carrying Rapa in 2-4 inguinal LNs and received an intramuscular injection of ovalbumin and alum (OVA, 500ug) two weeks later, followed by OVA rechallenge at week 5. Four control animals received vaccinations without prior iLN-MP injections. Hematology and biochemistry values were collected at selected intervals. Antibodies to OVA were measured by ELISA and expressed as EC50. T and B cell subsets were analyzed by flow cytometry. Results and Discussion: WBC values fluctuated without consistent patterns associated with iLN-MP vaccinations, and liver and kidney function (AST, ALT, bilirubin, BUN) were normal after iLN-MPs. Control animals developed consistent anti-OVA IgM (EC50: 600-1800) and IgG (1000-5000) two weeks after vaccination and higher IgG (>12000) after rechallenge. In iLN-MPs animals, anti-OVA IgM (200-1800) was similar and IgG (100-2000) lower in response to the initial challenge, but with no significant suppression of secondary IgG responses after rechallenge. Memory T and B cell subsets decreased while Tregs were stable or increased after iLN-MPs in two animals. Conclusions: Intra-lymph node injections of MPs loaded with rapamycin were well tolerated. Early class-switching (IgG) responses to vaccine antigens tended to be lower after iLN-MPs, suggesting partial immunomodulation by iLN-MPs, although an effect of residual particle-associated rapamycin cannot be excluded. These data support the safety of this approach and enable future studies to test the efficacy of iLN-MP for induction of tolerance to allo- (or auto-) antigens in these translational settings.