Nanovaccine administration route is critical to obtain pertinent iNKt cell help for robust anti-tumor T and B cell responses (1)
Biodegradable poly(lactic-co-glycolic acid) (PLGA) nanoparticles based vaccines have advantages such as 1) antigens are protected from premature degradation by proteolytic enzymes in the serum, 2) higher amounts of antigen gets delivered to professional antigen-presenting cells, and 3) antigen and adjuvant co-delivery guarantees maturation and activation of Dendritic cells (DCs) thereby providing both TCR and co-stimulatory signals to T cells, resulting in strong anti-tumor responses in preclinical mouse models.
PLGA nanoparticles (NP) encapsulating only ovalbumin, NP (OVA); only IMM-60, NP (IMM60); a combination of both,NP(OVA+IMM60) or NP(HPV+IMM60) were prepared using a w/o/w emulsion and solvent evaporation–extraction method. In order to track nanoparticles (NPs) in vivo, the ovalbumin was labeled using a fluorescent dye with near-infrared emission (VivoTag S750, PerkinElmer) according to the manufacturer’s instructions and injected by IV injection into several mouse strains.
Already 30 minutes after intravenous injection, OVA-Vivo750 could be detected in the liver and in the bladder via whole-body imaging. By contrast, subcutaneous and intranodal administration led to substantially lower drainage to the liver, and most of the antigen remained at the injection site. Subcutaneous and intranodal administration delivered less antigen to the liver but more to the lymph nodes (LNs) where antigen was stably retained for at least four days
No significant difference in the number of antigen-specific CD8+ T cells in the spleens between groups of mice vaccinated via different routes. On day 14, when the immune response was declining, the number of antigen-specific CD8+ T cells also contracted similarly in all groups. By contrast, on day 7, significantly higher in vivo, antigen-specific, cytotoxicity by intravenous vaccinations were observed and the number of IFN-y producing CD8+ T cells was significantly higher in mice that were injected intravenously than the mice injected subcutaneously.
Measuring the serum levels of ovalbumin-specific antibodies revealed a faster emergence of the Th2 linked anti-ovalbumin IgG1 antibodies after intravenous or intranodal administration when compared to the subcutaneous route. The most striking difference was observed in Th1 associated IgG2 c switching, which appeared to be mostly restricted to the intravenous route of administration.
Intravenous vaccination is most effective in delaying tumor growth and the induction of systemic IFN-γ levels. Even though IFN- γ levels were also elevated in tumor-bearing mice injected subcutaneously, anti-ova IgG2c production was only found after intravenous vaccination. At a low dose, the survival benefit of the nanoparticle delivery by the intravenous route became even more prominent over intranodal and subcutaneous routes, in which the systemic IFN-γ has disappeared. A clear increase in the delay of tumor growth when vaccination is combined with anti PD1 blocking antibodies. Surprisingly, of the groups treated with the anti-PD-1 antibody, the most striking increase in survival was observed within the intravenously vaccinated mice group. intravenous route of administration acts synergistically with immune checkpoint blockade while other routes of administration do not.
The intravenous route gives rise to the most potent antigen-specific Th1 type T and B cell responses and could be successfully combined with checkpoint modulation for the treatment of established tumors.