Systems analysis of human responses to an aluminium hydroxide-adsorbed TLR7 agonist (AS37) adjuvanted vaccine reveals a dose-dependent and specific activation of the interferon-mediated antiviral response

The candidate Adjuvant System AS37 contains a synthetic toll-like receptor agonist (TLR7a) adsorbed to alum. In a phase I study (NCT02639351), healthy adults were randomised to receive one dose of licensed alum-adjuvanted meningococcal serogroup C (MenC-CRM₁₉₇) conjugate vaccine (control) or MenC-CRM₁₉₇ conjugate vaccine adjuvanted with AS37 (TLR7a dose 12.5, 25, 50 or 100 µg). A subset of 66 participants consented to characterisation of peripheral whole blood transcriptomic responses, systemic cytokine/chemokine responses and multiple myeloid and lymphoid cell responses as exploratory study endpoints. Blood samples were collected pre-vaccination, 6 and 24 h post-vaccination, and 3, 7, 28 and 180 days post-vaccination. The gene expression profile in whole blood showed an early, AS37-specific transcriptome response that peaked at 24 h, increased with TLR7a dose up to 50 µg and generally resolved within one week. Five clusters of differentially expressed genes were identified, including those involved in the interferon-mediated antiviral response. Evaluation of 30 cytokines/chemokines by multiplex assay showed an increased level of interferon-induced chemokine CXCL10 (IP-10) at 24 h and 3 days post-vaccination in the AS37-adjuvanted vaccine groups. Increases in activated plasmacytoid dendritic cells (pDC) and intermediate monocytes were detected 3 days post-vaccination in the AS37-adjuvanted vaccine groups. T follicular helper (Tfh) cells increased 7 days post-vaccination and were maintained at 28 days post-vaccination, particularly in the AS37-adjuvanted vaccine groups. Moreover, most of the subjects that received vaccine containing 25, 50 and 100 µg TLR7a showed an increased MenC-specific memory B cell responses versus baseline. These data show that the adsorption of TLR7a to alum promotes an immune signature consistent with TLR7 engagement, with up-regulation of interferon-inducible genes, cytokines and frequency of activated pDC, intermediate monocytes, MenC-specific memory B cells and Tfh cells. TLR7a 25-50 µg can be considered the optimal dose for AS37, particularly for the adjuvanted MenC-CRM₁₉₇ conjugate vaccine.

Mannosylation of LNP Results in Improved Potency for Self-Amplifying RNA (SAM) Vaccines

Mannosylation of Lipid Nanoparticles (LNP) can potentially enhance uptake by Antigen Presenting Cells, which are highly abundant in dermal tissues, to improve the potency of Self Amplifying mRNA (SAM) vaccines in comparison to the established unmodified LNP delivery system. In the current studies, we evaluated mannosylated LNP (MLNP), which were obtained by incorporation of a stable Mannose-cholesterol amine conjugate, for the delivery of an influenza (hemagglutinin) encoded SAM vaccine in mice, by both intramuscular and intradermal routes of administration. SAM MLNP exhibited in vitro enhanced uptake in comparison to unglycosylated LNP from bone marrow-derived dendritic cells, and in vivo more rapid onset of the antibody response, independent of the route. The increased binding antibody levels also translated into higher functional hemagglutinin inhibition titers, particularly following intradermal administration. T cell assay on splenocytes from immunized mice also showed an increase in antigen specific CD8⁺ T responses, following intradermal administration of MLNP SAM vaccines. Induction of enhanced antigen specific CD4⁺ T cells, correlating with higher IgG2a antibody responses, was also observed. Hence, the present work illustrates the benefit of mannosylation of LNPs to achieve a faster immune response with SAM vaccines and these observations could contribute to the development of novel skin delivery systems for SAM vaccines.

The droplet size of emulsion adjuvants has significant impact on their potency, due to differences in immune cell-recruitment and -activation

Self-emulsification is routinely used for oral delivery of lipophilic drugs in vivo, with the emulsion forming in vivo. We modified this technique to prepare novel oil-in-water emulsions of varying droplet size and composition on bench to enable adjuvanted vaccine delivery. We used these formulations to show that smaller droplets (20 nm) were much less effective as adjuvants for an influenza vaccine in mice than the emulsion droplet size of commercial influenza vaccine adjuvants (~160 nm). This was unexpected, given the many claims in the literature of the advantages of smaller particulates. We also undertook cell-recruitment mechanistic studies at site of injection and draining lymph nodes to directly address the question of why the smaller droplets were less effective. We discovered that emulsion droplet size and composition have a considerable impact on the ability to recruit immune cells to the injection site. We believe that further work is warranted to more extensively explore the question of whether, the smaller is not 'better', is a more common observation for particulate adjuvants.

Co-administration of GM-CSF expressing RNA is a powerful tool to enhance potency of SAM-based vaccines

Self-amplifying mRNAs (SAM)-based vaccines have been shown to induce a robust immune response in various animal species against both viral and bacterial pathogens. Due to their synthetic nature and to the versatility of the manufacturing process, SAM technology may represent an attractive solution for rapidly producing novel vaccines, which is particularly critical in case of pandemic infections or diseases mediated by newly emerging pathogens. Recent published data support the hypothesis that Antigen Presenting Cells (APCs) are responsible for CD8+ T-cell priming after SAM vaccination, suggesting cross-priming as the key mechanism for antigen presentation by SAM vaccines. In our study we investigated the possibility to enhance the immune response induced in mice by a single immunization with SAM by increasing the recruitment of APCs at the site of injection. To enhance SAM immunogenicity, we selected murine granulocyte-macrophage colony-stimulating factor (GM-CSF) as a model chemoattractant for APCs, and developed a SAM-GM-CSF vector. We evaluated whether the use of SAM-GM-CSF in combination with a SAM construct encoding the Influenza A virus nucleoprotein (NP) would lead to an increase of APC recruitment and NP-specific immune response. We indeed observed that the administration of SAM-GM-CSF enhances the recruitment of APCs at the injection site. Consistently with our hypothesis, co-administration of SAM-GM-CSF with SAM-NP significantly improved the magnitude of NP-specific CD8+ T-cell response both in terms of frequency of cytotoxic antigen-specific CD8+ T-cells and their functional activity in vivo. Furthermore, co-immunization with SAM-GM-CSF and SAM-NP provided an increase in protection against a lethal challenge with influenza virus. In conclusion, we demonstrated that increased recruitment of APCs at the site of injection is associated with an enhanced effectiveness of SAM vaccination and might be a powerful tool to potentiate the efficacy of RNA vaccination.

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.

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.

[The normal topographic and CT-tomographic anatomy of the ostiomeatal complex]

Recent advances in the pathophysiology of the nasal cavity and paranasal sinuses and the development of endoscopic equipment and techniques have led to a new "functional" surgical management of chronic or recurrent sinusal conditions. The ostiomeatal complex is a narrow and intricate passage way providing aeration and mucus clearance from anterior ethmoid sinus, maxillary sinus and frontal sinus. CT, allowing the detailed demonstration of normal and abnormal patterns of the ostiomeatal complex, permits accurate preoperative planning, which has reduced the number of surgical complications. Ostiomeatal complex anatomy and the corresponding CT features are analyzed, as seen in 85 patients with or without rhinosinusal inflammatory lesions. The CT technique with coronal and axial scans and electronic parasagittal reconstructions, is also reported. Finally, the images obtained on different CT planes are compared, as proposed by other authors.