Enhancing influenza vaccine immunogenicity and efficacy through infection mimicry using silk microneedles

Traditional bolus vaccine administration leads to rapid clearance of vaccine from lymphoid tissue. However, there is increasing evidence suggesting that the kinetics of antigen delivery can impact immune responses to vaccines, particularly when tailored to mimic natural infections. Here, we present the specific enhancements sustained release immunization confers to seasonal influenza vaccine, including the magnitude, durability, and breadth of humoral responses. To achieve sustained vaccine delivery kinetics, we have developed a microneedle array patch (MIMIX), with silk fibroin-formulated vaccine tips designed to embed in the dermis after a short application to the skin and release antigen over 1-2 weeks, mimicking the time course of a natural influenza infection. In a preclinical murine model, a single influenza vaccine administration via MIMIX led to faster seroconversion, response-equivalence to prime-boost bolus immunization, higher HAI titers against drifted influenza strains, and improved protective efficacy upon lethal influenza challenge when compared with intramuscular injection. These results highlight infection mimicry, achieved through sustained release silk microneedles, as a powerful approach to improve existing seasonal influenza vaccines, while also suggesting the broader potential of this platform technology to enable more efficacious next-generation vaccines and vaccine combinations.

Improved immunogenicity of individual influenza vaccine components delivered with a novel dissolving microneedle patch stable at room temperature

Prevention of seasonal influenza epidemics and pandemics relies on widespread vaccination coverage to induce protective immunity. In addition to a good antigenic match with the circulating viruses, the effectiveness of individual strains represented in the trivalent vaccines depends on their immunogenicity. In this study, we evaluated the immunogenicity of H1N1, H3N2, and B seasonal influenza virus vaccine strains delivered individually with a novel dissolving microneedle patch and the stability of this formulation during storage at 25 °C. Our data demonstrate that all strains retained their antigenic activity after incorporation in the dissolving patches as measured by single radial diffusion (SRID) assay and immune responses to vaccination in BALB/c mice. After a single immunization, all three antigens delivered with microneedle patches induced superior neutralizing antibody titers compared to intramuscular immunization. Cutaneous antigen delivery was especially beneficial for the less immunogenic B strain. Mice immunized with dissolving microneedle patches encapsulating influenza A/Brisbane/59/07 (H1N1) vaccine were fully protected against lethal challenge by homologous mouse-adapted influenza virus. All vaccine components retained activity during storage at room temperature for at least 3 months as measured in vitro by SRID assay and in vivo by mouse immunization studies. Our data demonstrate that dissolving microneedle patches are a promising advance for influenza cutaneous vaccination due to improved immune responses using less immunogenic influenza antigens and enhanced stability.

Positive Contribution of Adjuvanted Influenza Vaccines to the Resolution of Bacterial Superinfections

BACKGROUND

Most preclinical studies assess vaccine effectiveness in single-pathogen infection models. This is unrealistic given that humans are continuously exposed to different commensals and pathogens in sequential and mixed infections. Accordingly, complications from secondary bacterial infection are a leading cause of influenza-associated morbidity and mortality. New vaccination strategies are needed to control infections on simultaneous fronts.

METHODS

We compared different anti-influenza vaccines for their protective potential in a model of viral infection with bacterial superinfection. Mice were immunized with H1N1/A/California/7/2009 subunit vaccines, formulated with different adjuvants inducing either T-helper type 1 (Th1) (MF59 plus CpG)-, Th1/2 (MF59)-, or Th17 (LTK63)-prone immune responses and were sequentially challenged with mouse-adapted influenza virus H1N1/A/Puerto Rico/8/1934 and Staphylococcus aureus USA300, a clonotype emerging as a leading contributor in postinfluenza pneumonia in humans.

RESULTS

Unadjuvanted vaccine controlled single viral infection, yet mice had considerable morbidity from viral disease and bacterial superinfection. In contrast, all adjuvanted vaccines efficiently protected mice in both conditions. Interestingly, the Th1-inducing formulation was superior to Th1/2 or Th17 inducers.

CONCLUSIONS

Our studies should help us better understand how differential immunity to influenza skews immune responses toward coinfecting bacteria and discover novel modes to prevent bacterial superinfections in the lungs of persons with influenza.

Fabrication of cell culture-derived influenza vaccine dissolvable microstructures and evaluation of immunogenicity in guinea pigs

Microstructure patches provide an opportunity for simple, effective, and safe vaccine administration, while achieving the desired immune response. We have evaluated the MicroCor transdermal system for cell culture-derived trivalent influenza vaccine administration. Influenza monovalent purified bulk vaccines (monobulks) (H1N1, H3N2, B) were concentrated by tangential flow filtration, lyophilized, and formulated with biocompatible excipients to form the microstructure array dissolvable tips. Standard single radial immunodiffusion (SRID) determined that the influenza antigens retained potency through the formulation and microstructure array fabrication processes. Array stability was evaluated for storage in both refrigerated and room temperature conditions. Microstructure mechanical strength was confirmed by application to excised pig skin, resulting in successful skin penetration and tip dissolution within 5 min of microstructure insertion. Guinea pigs immunized with influenza vaccine-loaded microstructures had hemagglutinin inhibition (HI) and IgG titers comparable to those obtained by intramuscular injection. After two immunizations, serum HI titers for all immunized groups were greater than 40 (>4-fold higher than the untreated group). These data demonstrate the feasibility for the development of skin delivery technologies that are compatible with cell culture-derived influenza vaccines.

Sublingual immunization with a subunit influenza vaccine elicits comparable systemic immune response as intramuscular immunization, but also induces local IgA and TH17 responses

Influenza is a vaccine-preventable disease that remains a major health problem world-wide. Needle and syringe are still the primary delivery devices, and injection of liquid vaccine into the muscle is still the primary route of immunization. Vaccines could be more convenient and effective if they were delivered by the mucosal route. Elicitation of systemic and mucosal innate and adaptive immune responses, such as pathogen neutralizing antibodies (including mucosal IgA at the site of pathogen entry) and CD4(+) T-helper cells (especially the Th17 subset), have a critical role in vaccine-mediated protection. In the current study, a sublingual subunit influenza vaccine formulated with or without mucosal adjuvant was evaluated for systemic and mucosal immunogenicity and compared to intranasal and intramuscular vaccination. Sublingual administration of adjuvanted influenza vaccine elicited comparable antibody titers to those elicited by intramuscular immunization with conventional influenza vaccine. Furthermore, influenza-specific Th17 cells or neutralizing mucosal IgA were detected exclusively after mucosal immunization.

Influenza subunit vaccine coated microneedle patches elicit comparable immune responses to intramuscular injection in guinea pigs

Delivery of influenza vaccine using innovative approaches such as microneedles has been researched extensively in the past decade. In this study we present concentration followed by formulation and coating of monobulks from 2008/2009 seasonal vaccine on to 3M's solid microstructured transdermal system (sMTS) by a GMP-scalable process. The hemagglutinin (HA) in monobulks was concentrated by tangential flow filtration (TFF) to achieve HA concentrations as high as 20mg/ml. The stability of the coated antigens was evaluated by the functional assay, single radial immunodiffusion (SRID). The data generated show stability of the coated antigen upon storage at 4°C and room temperature in the presence of desiccant for at least 8 weeks. Freeze-thaw stability data indicate the stability of the coated antigen in stressed conditions. The vaccine coated microstructures were evaluated in vivo in a guinea pig model, and resulted in immune titers comparable to the traditional trivalent vaccine administered intramuscularly. The data presented indicate the potential use of the technology in delivery of influenza vaccine. This paper also addresses the key issues of stability of coated antigen, reproducibility and scalability of the processes used in preparation of influenza vaccine coated microneedle patches that are important in developing a successful product.