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The need for more effective influenza vaccines is highlighted by the emergence of novel influenza strains, which can lead to new pandemics. There is a growing population of susceptible subjects at risk for severe complications of influenza, such as the elderly who are only in part protected by current licensed seasonal vaccines. One strategy for improving seasonal and pandemic vaccines takes advantage of adjuvants to boost and modulate evoked immune responses. In this study, we examined the capacity of the recently described adjuvant cyclic di-adenosine monophosphate (c-di-AMP) to serve as an adjuvant for improved mucosal influenza vaccines, and induce effective protection against influenza H5N1. In detail, c-di-AMP promoted (i) effective local and systemic humoral immune responses, including protective hemagglutination inhibition titers, (ii) effective cellular responses, including multifunctional T cell activity, (iii) induction of long-lasting immunity, and (iv) protection against viral challenge. Furthermore, we demonstrated the dose-sparing capacity of the adjuvant as well as the ability to evoke cross-clade protective immune responses. Overall, our results suggest that c-di-AMP contributes to the generation of a protective cell-mediated immune response required for efficacious vaccination against influenza, which supports the further development of c-di-AMP as an adjuvant for seasonal and pandemic influenza mucosal vaccines.

To cite this article: Debarry J, Hanuszkiewicz A, Stein K, Holst O, Heine H. The allergy-protective properties of Acinetobacter lwoffii F78 are imparted by its lipopolysaccharide. Allergy 2010; 65: 690–697. Abstract Background: An increasing number of epidemiological studies show that exposure to farming environment during early childhood strongly influences the development of allergic reactions later in life (‘hygiene hypothesis’). Also, it had been shown that certain bacteria from this environment may have allergy-protective properties. In the present study, we further characterized one of these bacteria, namely Acinetobacter lwoffii F78, with regard to the bacteria-induced signaling and possible mechanisms of allergy protection. Methods: The impact of A. lwoffii F78 on human monocyte-derived dendritic cells especially with respect to their THelper cell polarization capacity was investigated by ELISA and real-time PCR experiments as well as confocal microscopy. The responsible molecule for these effects was further characterized and identified using blocking experiments. Results: It was shown that A. lwoffii F78 induced a TH1-polarizing program in human dendritic cells which led to TH1 differentiation. In addition, a positive influence on the TBet/GATA3 level could be detected. Blocking experiments revealed that the lipopolysaccharide (LPS) of A. lwoffii F78 was the responsible molecule promoting these effects. Conclusion: We found evidence that the allergy-protecting effects of A. lwoffii F78 are because of the activation of a TH1-polarizing program in human dendritic cells, and that the LPS of A. lwoffii F78 is responsible for these beneficial effects.

Background Children who grow up in a farming environment show lower levels of atopic sensitization, hay fever, and asthma than children of the same age not living in such an environment. A number of investigations provided good evidence that this is due to an early-life contact with cowsheds, farm animals, and/or consumption of products like raw milk. Also, it had been indicated that microorganisms might have an important effect on the development of allergies, and thus the question arose of which farm microbial organisms, their products, or both might induce or influence allergy-protective mechanisms. Objective We sought to gain further insight into the potential allergy-protective properties of microbes isolated from the farming environment. Methods Of a number of bacterial species identified in cowsheds of farms, 2 were selected, isolated, and characterized, namely Acinetobacter lwoffii F78 and Lactococcus lactis G121. The isolates were investigated with regard to their activation of pattern-recognition receptors, the maturation of human monocyte-derived dendritic cells, the upregulation of inflammatory cytokines, the T H 1-polarizing Notch ligand expression, and their influence on the allergic phenotype. Results It is shown that both bacterial isolates were able to reduce allergic reactions in mice, to activate mammalian cells in vitro , and to induce a T H 1-polarizing program in dendritic cells. Conclusion Our data strongly support the hygiene hypothesis, which states that an environment rich in microbiologic structures, such as a farming environment, might protect against the development of allergies. Clinical implications This work provides the first data on a potential application of cowshed bacteria in allergy protection.

TLR are primary triggers of the innate immune system by recognizing various microorganisms through conserved pathogen-associated molecular patterns. TLR2 is the receptor for a functional recognition of bacterial lipopeptides (LP) and is up-regulated during various disorders such as chronic obstructive pulmonary disease and sepsis. This receptor is unique in its ability to form heteromers with TLR1 or TLR6 to mediate intracellular signaling. According to the fatty acid pattern as well as the assembling of the polypeptide tail, LP can signal through TLR2 in a TLR1- or TLR6-dependent manner. There are also di- and triacylated LP, which stimulate TLR1-deficient cells and TLR6-deficient cells. In this study, we investigated whether heterodimerization evolutionarily developed to broaden the ligand spectrum or to induce different immune responses. We analyzed the signal transduction pathways activated through the different TLR2 dimers using the three LP, palmitic acid (Pam)octanoic acid (Oct)2C-(VPGVG)4VPGKG, fibroblast-stimulating LP-1, and Pam2C-SK4. Dominant-negative forms of signaling molecules, immunoblotting of MAPK, as well as microarray analysis indicate that all dimers use the same signaling cascade, leading to an identical pattern of gene activation. We conclude that heterodimerization of TLR2 with TLR1 or TLR6 evolutionarily developed to expand the ligand spectrum to enable the innate immune system to recognize the numerous, different structures of LP present in various pathogens. Thus, although mycoplasma and Gram-positive and Gram-negative bacteria may activate different TLR2 dimers, the development of different signal pathways in response to different LP does not seem to be of vital significance for the innate defense system.