Surface conjugation of EP67 to biodegradable nanoparticles increases the generation of long-lived mucosal and systemic memory T-cells by encapsulated protein vaccine after respiratory immunization and subsequent T-cell-mediated protection against respiratory infection

Encapsulation of protein vaccines in biodegradable nanoparticles (NP)increases T-cell expansion after mucosal immunization but requires incorporating a suitable immunostimulant to increase long-lived memory T-cells. EP67 is a clinically viable, host-derived peptide agonist of the C5a receptor that selectively activates antigen presenting cells over neutrophils. We previously found that encapsulating EP67-conjugated CTL peptide vaccines in NP increases long-lived memory subsets of CTL after respiratory immunization. Thus, we hypothesized that alternatively conjugating EP67 to the NP surface can increase long-lived mucosal and systemic memory T-cells generated by encapsulated protein vaccines. We found that respiratory immunization of naïve female C57BL/6 mice with LPS-free ovalbumin (OVA)encapsulated in PLGA 50:50 NP (∼380 nm diameter)surface-conjugated with ∼0.1 wt% EP67 through 2 kDa PEG linkers (i)increased T-cell expansion and long-lived memory subsets of OVA _323-339 -specific CD4 ⁺ and OVA _257-264 -specific CD8a ⁺ T-cells in the lungs (CD44 ^HI /CD127/KLRG1)and spleen (CD44 ^HI /CD127/KLRG1/CD62L)and (ii)decreased peak CFU of OVA-expressing L. monocytogenes (LM-OVA)in the lungs, liver, and spleen after respiratory challenge vs. encapsulation in unmodified NP. Thus, conjugating EP67 to the NP surface is one approach to increase the generation of long-lived mucosal and systemic memory T-cells by encapsulated protein vaccines after respiratory immunization.