Pneumovax™ was kindly donated by CSL Biotherapies, Australia. The co-administered Tritanrix™-HepB™ and Hiberix™ vaccines were kindly donated by GlaxoSmithKline. Clinicaltrials.gov number NCT00170612. “
“The obligate intracellular pathogen

Chlamydophila (Cp.) psittaci primarily infects birds and is horizontally transmitted through aerosols of nasal secretions and faeces. Initially, the respiratory tract is infected, from where the disease further spreads leading to a systemic infection. Mainly in the poultry industry substantial financial losses result from a decrease in egg-production and the need for antibiotic treatment. Zoonotic transmission occurs in people in close contact with infected birds, the clinical outcome ranging from unapparent to severe flu-like symptoms or pneumonia [1].

Immunisation with a plasmid DNA encoding the Major Outer Membrane Protein GSK1120212 supplier (pcDNA1/MOMP) leads to significant protection against severe clinical signs, lesions and bacterial excretion as compared to placebo-vaccinated controls [2]. However, rhinitis (in 43% of the turkeys), pharyngeal excretion (14%) and thoracic (71%) and abdominal (29%) air sac lesions can still be observed. It has been reported that DNA vaccination, using unformulated plasmid DNA (pDNA), shows a low gene transfer efficiency in the host cell and hence a low antigen expression [3]. Therefore, we examined if we could further improve the current pcDNA1/MOMP vaccine. To enhance pDNA delivery into the host

cells, cationic liposomes or cationic ABT 199 TCL polymers such as polyethyleneimine (PEI) and dendrimers can be used. These cationic carriers bind the pDNA electrostatically and condense it into positively charged nanoparticles that are more easily taken up by host cells. Furthermore, they protect the pDNA against extracellular nucleases [4]. Several studies have already shown that cationic liposomes, PEI and dendrimers can enhance the transfection efficiency leading to improved gene expression in vitro and in vivo [5], [6], [7], [8], [9], [10], [11] and [12]. To optimise transgene expression, different strategies like the use of regulatory elements, Kozak sequences and codon optimisation can be applied [13]. In a recent study performed by Zheng et al. [14], codon optimisation significantly enhanced gene expression and immunogenicity of a C. muridarum MOMP-based DNA vaccine. The first aim of this study was to investigate whether the transfection efficiency of pcDNA1/MOMP could be enhanced by forming complexes with cationic liposomes or polymers, in addition to improving the translation efficiency of the cloned ompA gene by codon optimisation. Another critical step in the immunisation process is the choice of the vaccine delivery route, which plays a vital role in creating protective immune responses. In experimental studies, the intramuscular route is generally accepted as the ‘gold standard’.