Encapsulation of an EP67-Conjugated CTL Peptide Vaccine in Nanoscale Biodegradable Particles Increases the Efficacy of Respiratory Immunization and Affects the Magnitude and Memory Subsets of Vaccine-Generated Mucosal and Systemic CD8+ T Cells in a Diameter-Dependent Manner

The diameter of biodegradable particles used to coencapsulate immunostirmilants and subunit vaccines affects. the magnitude of memory CD8(+) T cells generated by systemic immunization. Possible effects on the magnitude of CD8(+) T cells generated by mucosal immunization or memory subsets that potentially correlate more, strongly with,protection against certain pathogens, however, are unknown. In this study, we conjugated our novel host-derived mucosal inimunostimulant, EP67, to the protective MCMV CTL epitope, pp89, through alysosomal protease-labile double arginine linker,(pp89-RR-EP67) and encapsulated in PLGA 50:,50 micro- or -nanoparicles. We then compared total magnitude, effector/central memory (CD127/KRLG1/CD62L), and IFN-gamma/TNE-alpha/IL.2 secreting subsets of pp89-specific CD8(+) T cells.as well as protection of naive female BALB/c mice against primary respiratory infection with MCMV 21 days' after respiratory immunization. We found that decreasing the diameter of encapsulating particle from,hem to rim '(i) increased the magnitude of pp89-specific CD8+ T cells in the lungs and spleen; (ii) partially changed, CD127/KLRG1 effector memory subsets in the lungs but riot the Spleen; (iii) changed CD127/KRLG1/CD62L effector/central memory subsets in the spleen;' (iv) changed pp89=resperisive IFN.gamma/TNF-alpha/IL-2 secreting subsets the lungs and spleen; (v) did not affect the extent to which encapsulation increased efficacy against primary MCMV respiratory infection over uneneapsulated pp89-RR-EP67. Thus, although not observed under Our current experimental conditions with MCMV, varying the diameter of nanoscale biodegradable particles may increase the efficacy of mucosal immunization with coencapsulated immimostimulant/subunit vaccines against certain pathogens by selectively increasing memory subset(s) of-CD8+ T cells that correlate the strongest with protection.