Efficient drug delivery to lymph nodes by intradermal administration and enhancement of anti-tumor effects of immune checkpoint inhibitors

Immune checkpoint inhibitors are novel immunotherapy drugs that have improved cancer treatments. Yet only a small percentage of patients experience durable responses to immune checkpoint inhibitors. Recently, it has been suggested that lymph nodes are important for the efficacy of immunotherapy. However, it is still unclear whether the efficient anti-PD-L1 antibody delivery to tumor-draining lymph nodes improves drug efficacy. In this study, we first characterized lymphatic drug delivery by intradermal administration compared with conventional subcutaneous and systemic administration in rodents and non-human primates. The results confirmed that intradermal administration of immune checkpoint inhibitors is suitable for efficient delivery to the tumor-draining lymph node. In FM3A and EMT6 tumor mice models with different PD-L1 expressions in tumor, efficient delivery of anti-PD-L1 antibody to tumor-draining lymph node by intradermal administration resulted in efficient inhibition of tumor growth in both models. The intradermal administration of low-dose anti-PD-L1 antibody also significantly suppressed tumor growth compared to intraperitoneal administration. It also suppressed tumor growth regardless of PD-L1 expression in tumors, suggesting the importance of blocking PD-L1 in tumor-draining lymph nodes. Hence, efficient delivery by intradermal administration of anti-PD-L1 antibody to tumor-draining lymph node might to be helpful to enhance drug efficacy and potentially reduce adverse events.

Development of a diffusion-weighed mathematical model for intradermal drainage quantification

The quantitative assessment of lymphatic dermal clearance using NIR fluorescent tracers is particularly important for the early diagnosis of several potential disabling diseases. Currently, half-life values are computed using a mono-exponential mathematical model, neglecting diffusion of the tracer within the dermis after injection. The size and position of the region of interest are subjectively manually selected around the point of injection on the skin surface where the fluorescence signal intensity is averaged, neglecting any spatial information contained in the image. In this study we present and test a novel mathematical model allowing the objective quantification of dermal clearance, taking into consideration potential dermal diffusion. With only two parameters, this "clearance-diffusion" model is simple enough to be applied in a variety of settings and requires almost no prior information about the system. We demonstrate that if dermal diffusion is low, the mono-exponential approach is suitable but still lacking objectivity. However, if dermal diffusion is substantial, the clearance-diffusion model is superior and allows the accurate calculation of half-life values.

Differential capability of Bacillus thuringiensis Cry1Ac protoxin and toxin to induce in vivo activation of dendritic cells and B lymphocytes

The insecticidal Bacillus thuringiensis protein Cry1Ac is produced as a protoxin and becomes activated to a toxin when ingested by larvae. Both proteins are immunogenic and able to activate macrophages. The proposed mechanism of immunostimulation by Cry1Ac protoxin has been related to its capacity to activate antigen-presenting cells (APC), but its ability to activate dendritic cells (DC) has not been explored. Here we evaluated, in the popliteal lymph nodes (PLN), spleen and peritoneum, the activation of DC CD11c⁺ MHC-II⁺ following injection with single doses (50 μg) of Cry1Ac toxin or protoxin via the intradermal (i.d.) and intraperitoneal (i.p.) routes in C57BL/6 mice. In vivo stimulation with both Cry1Ac proteins induced activation of DC via upregulation of CD86, primarily in PLN 24 h after i. d. injection. Moreover, this activation was detected in DC, displaying CD103+, a typical marker of migratory DC, while upregulation of CD80 was uniquely induced by toxin. Tracking experiments showed that Cy5-labeled Cry1Ac proteins could rapidly reach the PLN and localize near DC, but some label remained in the footpad. When the capacity of Cry1Ac-activated DC to induce antigen presentation was examined, significant proliferation of naïve T lymphocytes was induced exclusively by the protoxin. The protoxin elicited a Th17-biased cytokine profile. Moreover, only the Cry1Ac toxin induced a pronounced proliferation of B cells from both untreated and Cry1Ac-injected mice, suggesting that it acts as a polyclonal activator. In conclusion, Cry1Ac protoxin and toxin show a distinctive capacity to activate APCs.

Skin thickness in neonates: Implications for intradermal vaccination

INTRODUCTION

Intradermal (ID) injection is an alternate route that enhances vaccine immunogenicity and decreases vaccine dose. Regular immunization usually starts at age 2 months, and the limited immune capacity of neonates and young infants makes them vulnerable to infection. Successful ID vaccine delivery in this population requires knowledge of skin thickness. Although skin thickness has been evaluated in infants aged 2 months or older, no comparable data are available for neonates, including preterm neonates.

METHODS

This prospective observational study used ultrasonography to assess skin thickness in 70 neonates (35 full-term and 35 preterm neonates) at deltoid, suprascapular, and thigh sites. The measurements were compared in relation to anatomical site, between full-term and preterm infants, and with skin thickness values for children aged 2 months or older, which were collected in our previous study using the same measurement technique.

RESULTS

In full-term neonates, skin was significantly thicker at the suprascapular site than at the deltoid and thigh sites (P < 0.05); in preterm neonates, skin was significantly thicker at the suprascapular site than at the thigh site (P < 0.05). Skin thickness values at all three sites were significantly lower in preterm neonates than in full-term neonates (P < 0.05). As compared with skin thickness values for infants aged 2 months, values for full-term neonates were significantly lower for the deltoid and suprascapular sites (P < 0.001).

CONCLUSIONS

Skin thickness values for neonates were affected by prematurity and were significantly lower than those for infants aged 2 months. These findings are important in the design of ID injection devices for neonates and young infants.

Immune responses after fractional doses of inactivated poliovirus vaccine using newly developed intradermal jet injectors: a randomized controlled trial in Cuba

INTRODUCTION

The World Health Organization recommends that, as part of the new polio endgame, a dose of inactivated poliovirus vaccine (IPV) be introduced by the end of 2015 in all countries using only oral poliovirus vaccine (OPV). Administration of fractional dose (1/5th of full dose) IPV (fIPV) intradermally may reduce costs, but its administration is cumbersome with BCG needle and syringe. We evaluated performance of two newly developed intradermal-only jet injectors and compared the immune response induced by fIPV with that induced by full-dose IPV.

METHODS

Children between 12 and 20 months of age, who had previously received two doses of OPV, were enrolled in Camaguey, Cuba. Subjects received a single dose of IPV (either full-dose IPV intramuscularly with needle and syringe or fIPV intradermally administered with one of two new injectors or with BCG needle or a conventional needle-free injector). Serum was tested for presence of poliovirus neutralizing antibodies on day 0 (pre-IPV) and on days 3, 7 and 21 (post-vaccination).

RESULTS

Complete data were available from 74.2% (728/981) subjects. Baseline median antibody titers were 713, 284, and 113 for poliovirus types 1, 2, and 3, respectively. Seroprevalence at study end were similar across the intervention groups (≥ 94.8%). The immune response induced with one new injector was similar to BCG needle and to the conventional injector; and superior to the other new injector. fIPV induced significantly lower boosting response compared to full-dose IPV. No safety concerns were identified.

INTERPRETATION

One of the two new injectors demonstrated its ability to streamline intradermal fIPV administration, however, further investigations are needed to assess the potential contribution of fIPV in the polio endgame plan.