Intradermal delivery of a fractional dose of influenza H7N9 split vaccine elicits protective immunity in mice and rats

Immune Response of Inactivated Rabies Vaccine Inoculated via Intraperitoneal, Intramuscular, Subcutaneous and Needle-Free Injection Technology-Based Intradermal Routes in Mice

Inoculation routes may significantly affect vaccine performance due to the local microenvironment, antigen localization and presentation, and, therefore, final immune responses. In this study, we conducted a head-to-head comparison of immune response and safety of inactivated rabies vaccine inoculated via intraperitoneal (IP), intramuscular (IM), subcutaneous (SC) and needle-free injection technology-based intradermal (ID) routes in ICR mice. Immune response was assessed in terms of antigen-specific antibodies, antibody subtypes and neutralizing antibodies for up to 28 weeks. A live rabies virus challenge was also carried out to evaluate vaccine potency. The dynamics of inflammatory cell infiltration at the skin and muscle levels were determined via histopathological examination. The kinetics and distribution of a model antigen were also determined by using in vivo fluorescence imaging. Evidence is presented that the vaccine inoculated via the ID route resulted in the highest antigen-specific antibody and neutralizing antibody titers among all administration routes, while IP and IM routes were comparable, followed by the SC route. Antibody subtype analysis shows that the IP route elicited a Th1-biased immune response, while SC and IM administration elicited a prominent Th2-type immune response. Unexpectedly, the ID route leads to a balanced Th1 and Th2 immune response. In addition, the ID route conferred effective protection against lethal challenge with 40 LD50 of the rabies CVS strain, which was followed by IP and IM routes. Moreover, a one-third dose of the vaccine inoculated via the ID route provided comparable or higher efficacy to a full dose of the vaccine via the other three routes. The superior performance of ID inoculation over other routes is related to longer local retention at injection sites and higher lymphatic drainage. Histopathology examination reveals a transient inflammatory cell infiltration at ID and IM injection sites which peaked at 48 h and 24 h, respectively, after immunization, with all side effects disappearing within one week. These results suggest that needle-free injection technology-based ID inoculation is a promising strategy for rabies vaccination in regard to safety and efficacy.

Intradermal Delivery of Dendritic Cell-Targeting Chimeric mAbs Genetically Fused to Type 2 Dengue Virus Nonstructural Protein 1

Targeting dendritic cells (DCs) by means of monoclonal antibodies (mAbs) capable of binding their surface receptors (DEC205 and DCIR2) has previously been shown to enhance the immunogenicity of genetically fused antigens. This approach has been repeatedly demonstrated to enhance the induced immune responses to passenger antigens and thus represents a promising therapeutic and/or prophylactic strategy against different infectious diseases. Additionally, under experimental conditions, chimeric αDEC205 or αDCIR2 mAbs are usually administered via an intraperitoneal (i.p.) route, which is not reproducible in clinical settings. In this study, we characterized the delivery of chimeric αDEC205 or αDCIR2 mAbs via an intradermal (i.d.) route, compared the elicited humoral immune responses, and evaluated the safety of this potential immunization strategy under preclinical conditions. As a model antigen, we used type 2 dengue virus (DENV2) nonstructural protein 1 (NS1). The results show that the administration of chimeric DC-targeting mAbs via the i.d. route induced humoral immune responses to the passenger antigen equivalent or superior to those elicited by i.p. immunization with no toxic effects to the animals. Collectively, these results clearly indicate that i.d. administration of DC-targeting chimeric mAbs presents promising approaches for the development of subunit vaccines, particularly against DENV and other flaviviruses.