LC/MS: An Essential Tool for Development of a Vaccine for Cosiella burnetiid: Highlights From ASMS 2018

C. burnetii is a small cocobacillus intracellular pathogen responsible for Q fever. It is spread from domesticated animals to humans via aerosols or contaminated dust. Infections are usually mild, but the ease of transmission and infection makes it a candidate for weaponization or bioterrorism. A poster by Goran Mitulovíc and colleagues at the Medical University of Vienna described work on developing a vaccine and diagnostic markers for C. burnettii (Mitulovíc, G.; Danchenko, M. et al. “Coxiella Burnetii Proteome Analyzed by µ-Pillar Arrayed Columns,” Poster WP389, ASTM 2018).

The key is to focus on the proteins of C. burnetii. The strain C. burnetii Henzerling 331 was grown in ACCM-2 host medium for seven days. Three different cultures were studied. One arm was administered (0.5 µg/mL) doxycycline every 24 hours. The second received a dose of 4 µg/mL of doxycycline every 24 hours. The third arm was doxycycline free. At the end of 7 days, each arm was harvested, washed with phosphate-buffered saline and stored at –80 °C. Next, the cells were lysed with the AllPrep RNA/Protein/DNA kit (Qiagen, Germantown, MD). Proteins were precipitated with cold acetone and then digested with trypsin. LC/MS with a µPAC pillar column (PharmaFluidics, Ghent, Belgium) coupled to an Orbitrap Q-Extactive Plus feeding data to Proteome Discoverer (both from Thermo Fisher Scientific, Waltham, MA).

This gave 761 proteins and 6156 peptides with a false discovery rate (FDR) of less than 0.1%. A complex Venn diagram shows 541 proteins common to the three arms. The high-dose arm shows 24 unique proteins, some of which were classed as stress proteins, including chaperones. The authors were able to assign origin and function to some proteins. They expect to use this data to study host–parasite interactions to design a new Q fever vaccine and diagnostic markers.

This poster is notable for the use of pillar columns, which provide very rapid separations with low sample loss due to nonspecific adsorption. Plus, the LC flow rate is low, which improves compatibility with mass spectrometers without flow splitting.

Robert L. Stevenson, Ph.D., is Editor Emeritus, American Laboratory/Labcompare; e-mail: [email protected]

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