These conditions certainly contributed to the rapid loss of the contaminating viruses. Only viruses that are present at very high titers and which grow very rapidly without adaptation would be able to survive such passaging. In a second series of

passages we also monitored more than 50 specimens that did not contain an influenza virus but were positive for other respiratory viruses. In these specimens interference by competing influenza virus growth was excluded. The culture conditions differed, as lower inoculum dilutions were used. Each sample/harvest was diluted 1:100 into the culture, which is the lowest standard dilution applied to recover very low-titred influenza virus. Also under these conditions 54 positive results for 8 different viruses became click here negative after only 2 or 3 passages and Wnt inhibitor after a total dilution of the original specimen by a factor of 2 × 10−4 to 2 × 10−5. When similar passages were conducted with adherent Vero cells (“Vero WHO seed”), several positive samples (adenovirus, rhinovirus, enterovirus, metapneumovirus, and bocavirus) remained positive after 2 passages. However, except for adenovirus, the counts did not increase but dropped

(data not shown). These results demonstrate that, under practical conditions as applied to grow influenza viruses, contaminating viruses can be effectively removed by passaging in MDCK 33016PF cells. In combination with their superior isolation efficiency [7] and [28], MDCK cells appear highly suitable to be used as an alternative to embryonated eggs to isolate and propagate candidate vaccine viruses.

The authors would like to thank Knut Schwarz, Marion Wellnitz, MTMR9 Veronika Horn and Inge Lettermann for their skillful technical assistance with these studies. We gratefully acknowledge confirmatory PCR test results by independent methods that were partly provided by Marcus Panning, of the Virology Department of the University Clinic in Freiburg, Germany. “
“Dendritic cells (DCs) are key components of the immune system which function by binding and collecting antigens. Following recognition, DCs present the antigen of interest through selective surface markers to T-cells in order to activate a specified immune response [1]. Antigen presentation also stimulates the differentiation of T-cells to B cells which release antibodies specific for the antigen of interest. It is these functions that researchers aim to exploit in the production of vaccines. Non-viral gene delivery to DCs is an attractive approach for DNA vaccination to elicit immune responses towards encoded antigenic sequences [2]. Non-viral techniques often entail delivery of nucleic acids that are bound to a cationic polymer (polycations) resulting in plasmid DNA (pDNA) – polymer products, known as polyplexes [3]. Polycations operate by binding and condensing pDNA into smaller structures thereby facilitating uptake.