Nanna Skall Sørensen

Dendrimers for Vaccine and Immunostimulatory Uses: A Review

Dendrimers are well-defined (monodisperse) synthetic globular polymers with a range of interesting chemical and biological properties. Chemical properties include the presence of multiple accessible surface functional groups that can be used for coupling biologically relevant molecules and methods that allow for precise heterofunctionalization of surface groups. Biologically, dendrimers are highly biocompatible and have predictable biodistribution and cell membrane interacting characteristics determined by their size and surface charge. Dendrimers have optimal characteristics to fill the need for efficient immunostimulating compounds (adjuvants) that can increase the efficiency of vaccines, as dendrimers can provide molecularly defined multivalent scaffolds to produce highly defined conjugates with small molecule immunostimulators and/or antigens. The review gives an overview on the use of dendrimers as molecularly defined carriers/presenters of small antigens, including constructs that have built-in immunostimulatory (adjuvant) properties, and as stand-alone adjuvants that can be mixed with antigens to provide efficient vaccine formulations. These approaches allow the preparation of molecularly defined vaccines with highly predictable and specific properties and enable knowledge-based vaccine design substituting the traditional empirically based approaches for vaccine development and production.

Adjuvants and delivery systems in veterinary vaccinology: current state and future developments

Modern adjuvants should induce strong and balanced immune responses, and it is often desirable to induce specific types of immunity. As an example, efficient Th1-immunity-inducing adjuvants are highly in demand. Such adjuvants promote good cell-mediated immunity against subunit vaccines that have low immunogenicity themselves. The development of such adjuvants may take advantage of the increased knowledge of the molecular mechanisms and factors controlling these responses. However, knowledge of such molecular details of immune mechanisms is relatively scarce for species other than humans and laboratory rodents, and in addition, there are special considerations pertaining to the use of adjuvants in veterinary animals, such as production and companion animals. With a focus on veterinary animals, this review highlights a number of approaches being pursued, including cytokines, CpG oligonucleotides, microparticles and liposomes.

Optimal combinations of acute phase proteins for detecting infectious disease in pigs

The acute phase protein (APP) response is an early systemic sign of disease, detected as substantial changes in APP serum concentrations and most disease states involving inflammatory reactions give rise to APP responses. To obtain a detailed picture of the general utility of porcine APPs to detect any disease with an inflammatory component seven porcine APPs were analysed in serum sampled at regular intervals in six different experimental challenge groups of pigs, including three bacterial (Actinobacillus pleuropneumoniae, Streptococcus suis, Mycoplasma hyosynoviae), one parasitic (Toxoplasma gondii) and one viral (porcine respiratory and reproductive syndrome virus) infection and one aseptic inflammation. Immunochemical analyses of seven APPs, four positive (C-reactive protein (CRP), haptoglobin (Hp), pig major acute phase protein (pigMAP) and serum amyloid A (SAA)) and three negative (albumin, transthyretin, and apolipoprotein A1 (apoA1)) were performed in the more than 400 serum samples constituting the serum panel. This was followed by advanced statistical treatment of the data using a multi-step procedure which included defining cut-off values and calculating detection probabilities for single APPs and for APP combinations. Combinations of APPs allowed the detection of disease more sensitively than any individual APP and the best three-protein combinations were CRP, apoA1, pigMAP and CRP, apoA1, Hp, respectively, closely followed by the two-protein combinations CRP, pigMAP and apoA1, pigMAP, respectively. For the practical use of such combinations, methodology is described for establishing individual APP threshold values, above which, for any APP in the combination, ongoing infection/inflammation is indicated.

Pig α1-Acid Glycoprotein: Characterization and First Description in Any Species as a Negative Acute Phase Protein

The serum protein α1-acid glycoprotein (AGP), also known as orosomucoid, is generally described as an archetypical positive acute phase protein. Here, porcine AGP was identified, purified and characterized from pooled pig serum. It was found to circulate as a single chain glycoprotein having an apparent molecular weight of 43 kDa by SDS-PAGE under reducing conditions, of which approximately 17 kDa were accounted for by N-bound oligosaccharides. Those data correspond well with the properties of the protein predicted from the single porcine AGP gene (ORM1, Q29014 (UniProt)), containing 5 putative glycosylation sites. A monoclonal antibody (MAb) was produced and shown to quantitatively and specifically react with all microheterogenous forms of pig AGP as analyzed by 2-D electrophoresis. This MAb was used to develop an immunoassay (ELISA) for quantification of AGP in pig serum samples. The adult serum concentrations of pig AGP were in the range of 1–3 mg/ml in a number of conventional pig breeds while it was lower in Göttingen and Ossabaw minipigs (in the 0.3 to 0.6 mg/ml range) and higher in young (2–5 days old) conventional pigs (mean: 6.6 mg/ml). Surprisingly, pig AGP was found to behave as a negative acute phase protein during a range of experimental infections and aseptic inflammation with significant decreases in serum concentration and in hepatic ORM1 expression during the acute phase response. To our knowledge this is the first description in any species of AGP being a negative acute phase protein.

Porcine blood mononuclear cell cytokine responses to PAMP molecules: comparison of mRNA and protein production.

Pathogen-associated molecular patterns (PAMPs) are conserved molecules of microorganisms inducing innate immune cells to secrete distinct patterns of cytokines. In veterinary species, due to a lack of specific antibodies, cytokines are often monitored as expressed mRNA only. This study investigated the induction of IFN-α, IL-12 p40, IL-1β, TNF-α, IL-6 and IL-10 by PAMP-molecules [CpG oligonucleotide D19 (CpG), peptidoglycan (PGN), lipopolysaccharide (LPS), Pam(3)Cys and poly-U] in porcine blood mononuclear cells (BMC) within a 24 h period. As expected, cytokine responses were PAMP-specific, CpG inducing IFN-α and IL-12 p40, and PGN, LPS and Pam(3)Cys inducing varying amounts of IL-12 p40, IL-1β, TNF-α, IL-6 and IL-10. Surprisingly, the ssRNA-mimic poly-U induced IL-6 and IL-1β only. Using CpG, PGN and LPS, the kinetics of cytokine production measured as mRNA (reverse transcription (RT)-qPCR) and protein (ELISA), respectively, correlated well, mRNA responses preceding protein responses. With the exception of IL-1β and IL-6, mRNA-responses were transient, whereas protein responses, except for TNF-α, followed saturation kinetics. Remarkably, LPS-induced TNF-α mRNA was not followed by a protein response. These results provide guidelines concerning the timing and use of protein and mRNA determinations for the characterization of porcine cytokine responses to PAMPs, although given the low number of animals used here results are preliminary and need confirmation in a larger study.

Enhancement of Muramyldipeptide (MDP) Immunostimulatory Activity by Controlled Multimerization on Dendrimers

Peptidoglycan is a widespread bacterial PAMP molecule and a powerful initiator of innate immune responses. It consists of repeating units of MDP, which as a monomer is only weakly immunostimulatory. Here, MDP-coupled dendrimers were prepared and investigated for stimulation of pig blood mononuclear cells. Compared to monomeric MDP, MDP-dendrimers induced a markedly enhanced production of IL-12 p40, IL-1β and IL-6 and completely down-regulated surface expression of B7 and MHC class II. These results suggest a possible novel strategy based on controlled multimerization of minimal PAMP motifs on dendrimers for preparing molecularly defined immunostimulators with predictable bioactivities.