Meeting report: Convening on the influenza human viral challenge model for universal influenza vaccines, Part 1: Value; challenge virus selection; regulatory, industry and ethical considerations; increasing standardization, access and capacity.

In response to global interest in the development of a universal influenza vaccine, the Bill & Melinda Gates Foundation, PATH, and the Global Funders Consortium for Universal Influenza Vaccine Development convened a meeting of experts (London, UK, May 2018) to assess the role of a standardized controlled human influenza virus infection model (CHIVIM) towards the development of novel influenza vaccine candidates. This report (in two parts) summarizes those discussions and offers consensus recommendations. This article (Part 1) covers challenge virus selection, regulatory and ethical considerations, and issues concerning standardization, access, and capacity. Part 2 covers specific methodologic considerations. Current methods for influenza vaccine development and licensure require large costly field trials. The CHIVIM requires fewer subjects and the controlled setting allows for better understanding of influenza transmission and host immunogenicity. The CHIVIM can be used to identify immune predictors of disease for at-risk populations and to measure efficacy of potential vaccines for further development. Limitations to the CHIVIM include lack of standardization, limited access to challenge viruses and assays, lack of consensus regarding role of the CHIVIM in vaccine development pathway, and concerns regarding risk to study participants and community. To address these issues, the panel of experts recommended that WHO and other key stakeholders provide guidance on standardization, challenge virus selection, and risk management. A common repository of well-characterized challenge viruses, harmonized protocols, and standardized assays should be made available to researchers. A network of research institutions performing CHIVIM trials should be created, and more study sites are needed to increase capacity. Experts agreed that a research network of institutions working with a standardized CHIVIM could contribute important data to support more rapid development and licensure of novel vaccines capable of providing long-lasting protection against seasonal and pandemic influenza strains.

Convening on the influenza human viral challenge model for universal influenza vaccines, Part 2: Methodologic considerations.

In response to global interest in the development of a universal influenza vaccine, the Bill & Melinda Gates Foundation, PATH, and the Global Funders Consortium for Universal Influenza Vaccine Development convened a meeting of experts (London, UK, May 2018) to assess the role of a standardized controlled human influenza virus infection model (CHIVIM) towards the development of novel influenza vaccine candidates. This report (in two parts) summarizes those discussions and offers consensus recommendations. Part 1 covers challenge virus selection, regulatory and ethical considerations, and issues concerning standardization, access, and capacity. This article (Part 2) summarizes the discussion and recommendations concerning CHIVIM methods. The panelists identified an overall need for increased standardization of CHIVIM trials, in order to produce comparable results that can support universal vaccine licensure. Areas of discussion included study participant selection and screening, route of exposure and dose, devices for administering challenge, rescue therapy, protection of participants and institutions, clinical outcome measures, and other considerations. The panelists agreed upon specific recommendations to improve the standardization and usefulness of the model for vaccine development. Experts agreed that a research network of institutions working with a standardized CHIVIM could contribute important data to support more rapid development and licensure of novel vaccines capable of providing long-lasting protection against seasonal and pandemic influenza strains.

Serum and mucosal antibody responses to inactivated polio vaccine after sublingual immunization using a thermoresponsive gel delivery system.

Administering vaccines directly to mucosal surfaces can induce both serum and mucosal immune responses. Mucosal responses may prevent establishment of initial infection at the port of entry and subsequent dissemination to other sites. The sublingual route is attractive for mucosal vaccination, but both a safe, potent adjuvant and a novel formulation are needed to achieve an adequate immune response. We report the use of a thermoresponsive gel (TRG) combined with a double mutant of a bacterial heat-labile toxin (dmLT) for sublingual immunization with a trivalent inactivated poliovirus vaccine (IPV) in mice. This TRG delivery system, which changes from aqueous solution to viscous gel upon contact with the mucosa at body temperature, helps to retain the formulation at the site of delivery and has functional adjuvant activity from the inclusion of dmLT. IPV was administered to mice either sublingually in the TRG delivery system or intramuscularly in phosphate-buffered saline. We measured poliovirus type-specific serum neutralizing antibodies as well as polio-specific serum Ig and IgA antibodies in serum, saliva, and fecal samples using enzyme-linked immunosorbent assays. Mice receiving sublingual vaccination via the TRG delivery system produced both mucosal and serum antibodies, including IgA. Intramuscularly immunized animals produced only serum neutralizing and binding Ig but no detectable IgA. This study provides proof of concept for sublingual immunization using the TRG delivery system, comprising a thermoresponsive gel and dmLT adjuvant.

Prevention of K-Ras- and Pten-mediated intravaginal tumors by treatment with camptothecin-loaded PLGA nanoparticles.

Primary squamous cell carcinoma of the vagina is an uncommon disease that often exhibits few symptoms before reaching an advanced stage. Topical intravaginal therapies for resolving precancerous and cancerous vaginal lesions have the potential to be non-invasive and safer alternatives to existing treatment options. Two factors limit the testing of this approach: lack of a preclinical intravaginal tumor model and absence of safe and effective topical delivery systems. In this study, we present both an inducible genetic model of vaginal squamous cell carcinoma in mice and a novel topical delivery system. Tumors were generated via activation of oncogenic K-Ras and inactivation of tumor suppressor Pten in LSL-K-RasG12D/+PtenloxP/loxP mice. This was accomplished by exposing the vaginal epithelium to a recombinant adenoviral vector expressing Cre recombinase (AdCre). As early as 3 weeks after AdCre exposure exophytic masses protruding from the vagina were observed; these were confirmed to be squamous cell carcinoma by histology. We utilized this model to investigate an anticancer therapy based on poly(lactic-co-glycolic acid) (PLGA) nanoparticles loaded with camptothecin (CPT); our earlier work has shown that PLGA nanoparticles can penetrate the vaginal epithelium and provide sustained CPT release. Particles were lavaged into the vaginal cavity of AdCre-infected mice. None of the mice receiving CPT nanoparticles developed tumors. These results demonstrate a novel topical strategy to resolve precancerous and cancerous lesions in the female reproductive tract.

Application of nanotechnologies for improved immune response against infectious diseases in the developing world.

There is an urgent need for new strategies to combat infectious diseases in developing countries. Many pathogens have evolved to elude immunity and this has limited the utility of current therapies. Additionally, the emergence of co-infections and drug resistant pathogens has increased the need for advanced therapeutic and diagnostic strategies. These challenges can be addressed with therapies that boost the quality and magnitude of an immune response in a predictable, designable fashion that can be applied for wide-spread use. Here, we discuss how biomaterials and specifically nanoscale delivery vehicles can be used to modify and improve the immune system response against infectious diseases. Immunotherapy of infectious disease is the enhancement or modulation of the immune system response to more effectively prevent or clear pathogen infection. Nanoscale vehicles are particularly adept at facilitating immunotherapeutic approaches because they can be engineered to have different physical properties, encapsulated agents, and surface ligands. Additionally, nanoscaled point-of-care diagnostics offer new alternatives for portable and sensitive health monitoring that can guide the use of nanoscale immunotherapies. By exploiting the unique tunability of nanoscale biomaterials to activate, shape, and detect immune system effector function, it may be possible in the near future to generate practical strategies for the prevention and treatment of infectious diseases in the developing world.

High loading efficiency and tunable release of plasmid DNA encapsulated in submicron particles fabricated from PLGA conjugated with poly-L-lysine.

Poly(lactic-co-glycolic acid) (PLGA) particles have been widely explored as vehicles for delivery of plasmid DNA to mammalian cells both in vitro and in vivo. Achieving high incorporation efficiencies and control over release kinetics are significant challenges in encapsulating hydrophilic molecules such as DNA within submicron particles fabricated from PLGA. This study explored two modifications in the preparation of submicron particles to specifically address these challenges. Firstly, we compared homogenization and sonication as energy sources for emulsification. It was demonstrated that particles prepared with homogenization resulted in higher encapsulation efficiency and a linear release profile of DNA as compared to particles prepared with sonication, which exhibited lower encapsulation efficiency and a burst release. Also investigated was conjugation of poly-L-lysine to PLGA (PLGA-PLL) to create an electrostatically favorable interaction between the carrier material and the DNA. Particles fabricated with high weight percentages of PLGA-PLL/PLGA resulted in remarkably increased loading (>90%). Additionally, the release profile could be dictated by the quantity of PLGA-PLL incorporated into the particles. Particles incubated in vitro on COS-7 cells were able to transfect cells. These results demonstrated that DNA encapsulation and release were modulated by the method of fabrication.

Development and characterization of enhanced green fluorescent protein and luciferase expressing cell line for non-destructive evaluation of tissue engineering constructs.

This study investigates the utility of genetically modified cells developed for the qualitative and quantitative non-destructive evaluation of cells on biomaterials. The Fisher rat fibroblastic cell line has been genetically modified to stably express the reporter genes enhanced green fluorescence protein (EGFP) and luciferase. These reporter genes provide two unique opportunities to evaluate cell growth on materials without destruction of the sample. Utilizing the fluorescence of EGFP expressed in the cells, we were able to demonstrate distribution of cells in a oligo(poly(ethylene glycol) fumarate) hydrogel material and on a titanium fiber mesh scaffold using an inverted fluorescent light microscope. In addition, we were able to utilize a molecular light imaging system to macroscopically image the cells on these materials both with fluorescence and luminescence, as well as quantify the signal from the samples. Quantification of cell growth on the titanium mesh material for a period of 28 days was accomplished using the molecular light imaging system. Imaging was extended in vivo to cells on the titanium mesh scaffolds subcutaneously implanted in Fisher rats for a period of 28 days. This study outlines a non-destructive method to evaluate cells growing on biomaterials in vitro and in vivo.

Early osteoblastic differentiation induced by dexamethasone enhances adenoviral gene delivery to marrow stromal cells.

We investigated the implications of induced osteogenic differentiation on gene delivery in multipotent rat marrow stromal cells (MSCs). Prior to genetic manipulation cells were cultured with or without osteogenic supplements (5x10(-8) M dexamethasone, 160 microM l-ascorbic acid 2-phosphate, and 10 mM beta-glycerophosphate). Comparison of liposome, retroviral, and adenoviral vectors demonstrated that all three vectors could mediate gene delivery to primary rat MSCs. When these vectors were applied in the absence or presence of osteogenic supplements, we found that MSCs differentiated prior to transduction with adenovirus type 5 vectors produced a 300% increase in transgene expression compared to MSCs that were not exposed to osteogenic supplements. This differentiation effect appeared specific to adenoviral mediated gene delivery, since there was minimal increase in retroviral gene delivery and no increase in liposome gene delivery when MSCs were treated with osteogenic supplements. In addition, we also determined this increase in transgene production to occur at a higher concentration of dexamethasone (5x10(-8) M) in the culture medium of MSCs prior to adenoviral transduction. We found that this increased transgene production could be extended to the osteogenic protein, human bone morphogenetic protein 2 (hBMP-2). When delivered by an adenoviral vector, hBMP-2 transgene production could be increased from 1.4 ng/10(5) cells/3 days to 4.3 ng/10(5) cells/3 days by culture of MSCs with osteogenic supplements prior to transduction. These results indicate that the utility of MSCs as a therapeutic protein delivery mechanism through genetic manipulation can be enhanced by pre-culture of these cells with dexamethasone.

In vivo evaluation of gene therapy vectors in ex vivo-derived marrow stromal cells for bone regeneration in a rat critical-size calvarial defect model.

Cells genetically modified to produce osteoinductive factors have potential for use in enhancing bone regeneration for reconstructive applications. Genetic modification of cells can be accomplished by a variety of gene therapy vectors. In this study we evaluated the ex vivo genetic modification of rat marrow stromal cells (MSCs) by adenoviral, retroviral, and cationic lipid vectors containing the gene for human bone morphogenetic protein 2 (hBMP-2). We investigated both the in vitro and in vivo osteogeneic potential of MSCs modified by each vector. In vitro, we found that only MSCs modified with the adenoviral vector produced detectable hBMP-2 and demonstrated a statistically significant increase in endogenous alkaline phosphatase activity indicative of osteogeneic differentiation. We further investigated the ability of genetically modified MSCs seeded on a titanium mesh scaffold to facilitate bone formation in vivo. In an orthotopic critical-size defect created in the rat cranium, bone formation was observed in all conditions with MSCs modified by the adenoviral vector demonstrating a small but statistically significant increase in bone formation relative to the other vectors and control. Implants in an ectopic location demonstrated minimal bone formation relative to the orthotopic location, with MSCs modified with cationic lipids forming less bone than the other vectors and control. Our results show that MSCs genetically modified with adenovirus containing the hBMP-2 gene had enhanced osteogeneic capacity relative to unmodified MSCs or MSCs modified by the other vectors. This study was the first to compare three different gene therapy vectors for the genetic modification of cells to produce osteoinductive factors for the purpose to enhance bone regeneration.

Bone regeneration through transplantation of genetically modified cells.

To the author's knowledge, the rabbit is the largest animal model used to explore bone regeneration with genetically modified cells. This technology needs to be expanded to larger animal models that represent a more clinically relevant application in which cells are isolated from the animal, expanded ex vivo, genetically modified, and implanted in a critical-size bone defect in the donor animal. Furthermore, optimization of the vector type, vector dose, cell dose, and carrier material choice must be accomplished in animal models before clinical investigation is initiated. Most research has focused on a single osteoinductive protein; however, multiple proteins may synergize to further enhance bone formation. In conclusion, transplantation of genetically modified cells provides a new opportunity to improve bone tissue regeneration.