P114 Modulation of vaccine-induced T cell immunity by specific adjuvants

Abstract

Introduction Successful vaccination requires generation of long-lasting and protective T cell responses, and thus, therapeutic strategies aimed to enhance vaccine-induced T cell immunity are a source of great interest. Here we have investigated the influence of toll-like receptor (TLR)-3 ligands as well as type I interferon (IFN) agonists on the maintenance of CD8 + T cell memory in the context of mucosal influenza vaccination. Methods Mice and vaccine studies. C57BL/6 J male mice between 8–10 weeks of age were used for our studies. Cold-adapted influenza vaccines were rescued by reverse genetics using A/Puerto Rico/8/34 (H1N1) hemagglutinin (HA) and neuraminidase (NA) segments in a A/Ann Arbor/6/60/ (H2N2) background (6 + 2 reassortant). Recombinant viruses were grown at 33 °C in 9-days old chicken eggs and titrated in Madin-Darby canine kidney cells (MDCKs) as described elsewhere. Nutlin-3 was purchased from Cayman Chemicals, poly I:C was purchased from Invivogen. Combinations of vaccine + adjuvants were administered intranasally in a maximum volume of 50 ml. Tissue samples were harvested from euthanized mice and processed for analysis of viral titers, quantitative RT-PCR, or ELISA. In survival experiments mice were sacrificed if their weight dropped more than 25% of their initial body weight as per institutional guidelines. The animal experiments were performed according to the guidelines of the German animal protection law. All animal protocols were approved by the relevant German authorities. Flow cytometry. Lung samples were enzymatically digested with 2 mg/ml of Collagenase D (Roche). Mediastinal lymph nodes were disrupted mechanically. Tissue samples were processed for flow cytometry and red cells were lysed using BD Red Blood Cell Lysing Buffer. Samples were acquired on a FACS canto II instrument and analyzed with FlowJO software (Treestar). Results Engagement of TLR3 and type I IFN signaling by candidate adjuvants of cold-adapted influenza vaccines in mice, increased vaccine-induced cytokine production early after mucosal administration, including enhanced production of MCP1, IP-10 and G-CSF. This increase in vaccine-induced early inflammatory responses resulted in robust cytotoxic T lymphocyte (CTL) activity, rapid viral clearance, and enhanced survival to influenza challenge. Conversely, vaccine adjuvants did not influence antibody titers in vaccinated individuals, suggesting that the early events that take place during the innate phase of the immune response play a chief role on the establishment and modulation of adaptive immunity. Conclusion Our results indicated that specific adjuvants with the ability to enhance TLR3 and type I IFN signaling enhance cytokine responses associated to vaccine administration, which resulted in improved CD8 + T cell-dependent recall responses. Of note, adjuvant-vaccine regimens reduced the vaccine dose necessary to provide protection to lethal challenge. These findings indicate that modulation of innate immunity via TLR ligands and type I IFN agonists may serve as a therapeutic strategy to enhance T cell memory maintenance after influenza vaccination, and may provide means to reduce the amount of vaccine stock necessary to protect individuals at risk in the face of an influenza pandemic.