NANOVACCINE PLATFORM CONTAINING TLR-9 AGONIST REQUIRES IFN-γ FOR INDUCE ANTIGEN-SPECIFIC IGG2A ANTIBODY RESPONSE

CONSTANZA MARIN; FEDERICO RUIZ MORENO; GIULIANA VEDELAGO; SANTIAGO PALMA; DANIEL ALBERTO ALLEMANDI; GABRIEL MORON; MARIA CRISTINA PISTORESI PALENCIA; BELKYS MALETTO

Congreso; LXIX REUNIÓN SAI; 2021

The subunit vaccines have many advantages; however, they need appropriate adjuvants to enhance immune response. Our group developed an adjuvant strategy in which OVA and CpG-ODN are formulated with a nanostructure (Coa-ASC16) formed by self-assembly of 6-O-ascorbyl palmitate (ASC16). We have previously shown that this nanoformulation (OCC) elicited stronger OVA-specific antibodies, and Th1 and CD8+ T-cell responses compared with a solution of OVA and CpG-ODN (OC). OCC elicited early IFN-γ secretion in lymph nodes (LN) draining the injection site peaking at 24 h after injection, and this secretion was higher than the one produced by the OC group. Conversely, the IFN-γ concentration in serum was higher in OC mice than in OCC mice. Here, we study the source of innate IFN-γ production and its requirement to induce an adaptive immune response. Wilde-type and IFN-γ-deficient mice were subcutaneously immunized with a single-dose of OC or OCC. LN and spleen from wilde-type mice were collected 24 h after injection and IFN-γ producing cells were assessed by flow cytometry after incubation with RPMI in the presence of Brefeldin A and Monensin at 37 °C 5% C02. The frequency of IFN-γ+ cells found in LN was higher in OCC mice than in OC mice (p<0.001), but no differences were observed in spleen. Furthermore, the relative proportion of IFN-γ+ cells was different between both groups, the main difference being the increased size of IFN-γ+ NK1.1 cells population in LN of OCC mice compared to OC mice (p<0.001). In IFN-γ-deficient mice, OCC elicited lower OVA-specific IgG2a titers than in wild-type mice; however, OVA-specific CD4+ T cells proliferation and frequency of SIINFEKL-Kbtetramer+ CD8+ T cells were not affected. Understanding the mechanism by which adjuvants engage the immune responses is critically important for the development of vaccines. Our results support the hypothesis that early IFN-γ production is important for obtaining productive responses to adjuvanted vaccines.