Cascade polymers also known as Starburst dendrimers are spheroidal polycations that can be synthesized with a well-defined diameter and a precise number of terminal amines per dendrimer. We show, using luciferase and beta-galactosidase containing plasmids, that dendrimers mediate high efficiency transfection of a variety of suspension and adherent cultured mammalian cells. Dendrimer-mediated transfection is a function both of the dendrimer/DNA ratio and the diameter of the dendrimer. Maximal transfection of luciferase are obtained using a diameter of 68 A and a dendrimer to DNA charge ratio of 6/1 (terminal amine to phosphate). Expression is unaffected by lysomotrophic agents such as chloroquine and only modestly affected (2-fold decrease) by the presence of 10% serum in the medium. Cell viability, as assessed by dye reduction assays, decreases by only 30% at 150 micrograms dendrimer/mL in the absence of DNA and about 75% in the presence of DNA. Under similar conditions polylysine causes a complete loss of viability. Gene expression decreased by 3 orders of magnitude when the charge ratio is reduced to 1:1. When GALA, a water soluble, membrane-destabilizing peptide, is covalently attached to the dendrimer via a disulfide linkage, transfection efficiency of the 1:1 complex is increased by 2-3 orders of magnitude. The high transfection efficiency of the dendrimers may not only be due to their diameter and shape but may also be caused by the pKa's (3.9 and 6.9) of the amines in the polymer. The low pKa's permit the dendrimer to buffer the pH change in the endosomal compartment. The characteristics of precise control of structure, favorable pKa's, and low toxicity make the dendrimers suitable for gene-transfer vehicles.

No abstract

With the exception of alum, emulsion-based vaccine adjuvants have been administered to far more people than any other adjuvant, especially since the 2009 H1N1 influenza pandemic. The number of clinical safety and immunogenicity evaluations of vaccines containing emulsion adjuvants has correspondingly mushroomed. In this review, the authors introduce emulsion adjuvant composition and history before detailing the most recent findings from clinical and postmarketing data regarding the effects of emulsion adjuvants on vaccine immunogenicity and safety, with emphasis on the most widely distributed emulsion adjuvants, MF59® and AS03. The authors also present a summary of other emulsion adjuvants in clinical development and indicate promising avenues for future emulsion-based adjuvant development. Overall, emulsion adjuvants have demonstrated potent adjuvant activity across a number of disease indications along with acceptable safety profiles.

The ongoing epizootic of highly pathogenic avian H5N1 influenza and its direct transmissibility and high pathogenicity in humans has led to renewed interest in the development of influenza vaccines with enhanced immunogenicity. Influenza vaccines are currently under development against influenza strains that are potentially pandemic threats, such as H5N1, as well as against the current seasonal influenza strains for use in populations susceptible to severe influenza disease. Influenza vaccines may be generally divided into two types: seasonal vaccines for use in a population that is largely primed to subtypes of the circulating influenza A strains and pandemic influenza vaccines that are designed to protect against influenza A viruses of a hemagglutinin (HA) subtype, to which the vast majority of the population is immunologically naive. Pandemic influenza vaccines can be further subdivided into prepandemic vaccines produced for use prior to or just after the declaration of a pandemic, and pandemic influenza vaccines that would be produced and used only after a pandemic is declared. Prepandemic influenza vaccines are formulated using HA and neuraminidase, which are likely to be antigenically similar to the influenza virus subtype deemed to pose the most probable pandemic threat. Enhanced vaccine immunogenicity is desirable for pandemic influenza vaccines and for seasonal vaccines used in target populations, such as the elderly, in which vaccine responses against the circulating influenza subtypes may be weak. Various methods to enhance the immunogenicity of influenza vaccines are under evaluation. Along with dose escalation and alternative delivery routes, strategies for improving the immunogenicity of influenza vaccines have focused on the use of immunologic adjuvants. An adjuvanted seasonal influenza vaccine, Fluad, has been licensed in some countries in Europe since 1997 for the elderly population, and a number of clinical trials have been completed or are in progress evaluating the use of adjuvants with pandemic and seasonal influenza vaccines. This review will focus on the use of emulsion-based adjuvants for enhancing the immunogenicity of pandemic influenza vaccines and of seasonal influenza vaccines in target populations.