CpG-ODN Facilitates Effective Intratracheal Immunization and Recall of Memory against Neoantigen-Expressing Alveolar Cells

Abstract

Intrapulmonary immune reactions are impaired by the tolerogenic environment of the lung. This is manifested by the absence of effective endogenous T cell responses upon neoantigen expression. This tolerance is considered to contribute to lung cancer and inefficient immune therapeutic interventions. To investigate the mechanisms contributing to lung tolerance and to overcome these restrictions, we developed a transgenic mouse model with induction of a neoantigen (OVA) exclusively in alveolar type II epithelial cells. This model is characterized by the absence of functional endogenous T cell responses upon OVA neoantigen induction. Standard DNA and protein vaccination protocols resulted in the accumulation of high numbers of antigen-specific CD8 T cells in the lung. However, clearance of antigen-expressing cells was not achieved. To overcome this tolerance, we induced inflammatory conditions by coapplication of the TLR ligands LPS and CpG-ODN during intrapulmonary vaccinations. Both ligands induced high numbers of neoantigen-specific T cells in the lung. However, only coapplication of CpG-ODN was sufficient to establish functional cytotoxic responses resulting in the elimination of neoantigen presenting target cells. Remarkably, CpG-ODN was also crucial for functional memory responses upon re-induction of the neoantigen. The results highlight the need of TLR9 co-stimulation for overcoming tolerization, which might be a key factor for therapeutic interventions.

Mucosal Immunization with a pH-Responsive Nanoparticle Vaccine Induces Protective CD8+ Lung-Resident Memory T Cells

“…Therefore, nanoparticles were coloaded with OVA protein and a nucleic acid adjuvant, CpG ODN 1826 (a single-stranded DNA agonist for TLR9). CpG DNA has been shown to enhance the CD8 + T cell response and has precedence for use in pulmonary immunization. ,, CpG was electrostatically complexed to OVA–NP conjugates (Figure S2B), and this formulation is referred to henceforth as OVA–NP/CpG or the “nanoparticle vaccine”.…”

“…CpG DNA has been shown to enhance the CD8 + T cell response and has precedence for use in pulmonary immunization. 40,44,53 CpG was electrostatically complexed to OVA−NP conjugates (Figure S2B), and this formulation is referred to henceforth as OVA−NP/CpG or the "nanoparticle vaccine".…”

Improved Functionality of Exhausted Intrahepatic CXCR5+ CD8+ T Cells Contributes to Chronic Antigen Clearance Upon Immunomodulation

“…Among various immunomodulatory functions, the liver has the propensity to prime functional CD8+ T cell immunity (20)(21)(22). We previously introduced a transgenic mouse model in which intracellular Ovalbumin (Ova) expression is activated by Tamoxifen (Tam) inducible CreERT2 recombinase (23,24), which allows for elucidating T cell responses towards Ova antigen in defined tissues (25)(26)(27)(28). Using OvaXCre mice, in which CreERT2 is controlled by the albumin promoter, we documented that the frequency of Ova expressing hepatocytes can be adjusted by Tam titration (23,(25)(26)(27).…”

“…We previously introduced a transgenic mouse model in which intracellular Ovalbumin (Ova) expression is activated by Tamoxifen (Tam) inducible CreERT2 recombinase (23,24), which allows for elucidating T cell responses towards Ova antigen in defined tissues (25)(26)(27)(28). Using OvaXCre mice, in which CreERT2 is controlled by the albumin promoter, we documented that the frequency of Ova expressing hepatocytes can be adjusted by Tam titration (23,(25)(26)(27). Moreover, we demonstrated that adoptive transfer of Ova-specific CD8+ T cells (OT-1 cells) or Ova-specific CD8+ T cell induction by vaccination eliminates low frequencies of Ova expressing hepatocytes.…”