Dataset on protein composition of a human plasma sub-proteome able to modulate the Dengue 2 virus infection in Huh 7.5 cells

The four serotypes of dengue virus (DENV1-4) are the causal agents of the emerging disease Dengue Fever and its severe forms. DENV is inoculated into human blood through a mosquito bite. Thus, plasma is an important media for DENV dissemination in infected persons and several important interactions should take place for the virus with human plasma proteins that strongly influence or may determine the course of the infection. This dataset contains 239 proteins identified in the elution fractions of human plasma subjected to DE-52 anion exchange chromatography. Data on DENV2 infection of Huh 7.5 cells in presence of the human plasma fraction is also presented.


a b s t r a c t
The four serotypes of dengue virus (DENV1-4) are the causal agents of the emerging disease Dengue Fever and its severe forms. DENV is inoculated into human blood through a mosquito bite. Thus, plasma is an important media for DENV dissemination in infected persons and several important interactions should take place for the virus with human plasma proteins that strongly influence or may determine the course of the infection. This dataset contains 239 proteins identified in the elution fractions of human plasma subjected to DE-52 anion exchange chromatography. Data on DENV2 infection of Huh 7.5 cells in presence of the human plasma fraction is also presented.  Data of proteins present in the different chromatography fractions could be useful for laboratories working on the fractionation of human plasma using different chromatographic approaches.

Data
This dataset describes conditions of chromatographic fractionation of human plasma resulting in a protein sample able to modulate DENV infection in mammalian cells, provides the identity of proteins contained in the different chromatography fractions and presents data on the infection of Huh 7.5 cells with DENV2 in presence of abovementioned human plasma sample.
The mouse brain-derived virus preparation was obtained by homogenization of suckling mouse brains infected with DENV2 (New Guinea strain) using RPMI-1640 medium. Purified flavivirusreactive mAb 4G2 was provided by the Unit for Production of Monoclonal Antibodies (CIGB, Cuba).

Fractionation of human plasma samples
Frozen human plasma samples from healthy volunteers were obtained from expired stocks of local blood banks, pooled and fractionated by anion exchange chromatography (AXC). Briefly, 125 mL of pooled human plasma were dialyzed against equilibration buffer (50 mM Hepes pH 6, 60 mM NaCl, 1 mM EDTA) and then centrifuged at 10,000 g for 30 min at 4°C, diluted 3-fold in equilibration buffer and subjected to tandem filtration through Whatman 1 qualitative filter paper (Whatman, UK) and a 0.45 mm membrane. The resulting sample was loaded at a flow rate of 10 cm/h onto an XK-26 chromatography column (GE Healthcare, USA) packed with 10 mL of DE-52 gel, which was next washed with equilibration buffer until absorbance at 280 nm returned to baseline (bound protein represented, in average, 1.2% of the initial protein contents of the sample and no more than 60% of the total protein binding capacity estimated for DE-52 at pH 6.0). Then, the column was washed sequentially with preparations of equilibration buffer containing increasing concentrations of NaCl (0.3 M, 0.6 M and 1 M) at 30 cm/h, and the protein species still bound to the column afterwards were eluted by the successive application of 0.02 M sodium acetate pH 3.0, water and 0.01 M NaOH. Chromatography fractions were used either separately or pooled in a single sample (ELU AXC ) [2] ( Fig. 1). Upon collection, a protease inhibitor cocktail consisting of 1 μg/mL leupeptin, 1 μg/mL pepstatin A, 1 μg/mL soybean trypsin inhibitor and 1 mM PMSF was added to the eluted fractions, which were subsequently dialyzed against 10 mM Hepes pH 7.0, 0.15 M NaCl, 1 mM CaCl 2 and stored at À20°C until used.

Virus-binding activity of plasma fractions
Microtiter plates were coated with 1 mg protein content of the corresponding AXC chromatography fraction diluted in 50 mL of 0.05 M sodium carbonate/bicarbonate buffer, pH 9.6. After coating, the plates were washed with 0.05% Tween 20 in 10 mM Hepes pH 7.0, 0.12 M NaCl, 1 mM CaCl 2 (HBCa-T) and remaining non-specific binding sites were blocked with 1% Bovine Serum Albumin in HBCa-T for 1 h at 37°C. Specified dilutions of mouse-derived DENV2 were added to the plates and the binding reaction was allowed to proceed for 2 h at 37°C. Bound virus was detected by incubation with biotinylated Mab 4G2 at 5 mg/mL (1 h at 37°C) followed by washing with HBCa-T and incubation with a streptavidin-peroxidase conjugate (1 h at 37°C). After washing, the plates were developed by adding 0.001% H 2 O 2 , 1 mg/mL o-phenylenediamine in 0.01 mol/L citric acid-phosphate buffer pH 5.0 for 20 min at room temperature, stopping the reactions by adding 20 mL of 2.5 M H 2 SO 4 , and reading absorbance at 492 nm in a microplate reader (Fig. 2).

Protein composition of AXC eluates
The pH of the AXC eluates was first adjusted to 8.  Protein identification based on MS/MS spectra was performed by searching the Swissprot database with the Mascot ver. 2.3 engine [3]. Searching limiters included propionamide cysteine as a fixed modification as well as methionine oxidation and deamidation of glutamine and asparagine as variable modifications, a precursor ion m/z tolerance of 10 ppm and trypsin as proteolytic enzyme, with up to one missed cleavage. Only doubly-and triply-charged precursor ions were considered, using an error of 0.2 Da for matching daughter ions in the MS/MS spectra. The false discovery rate (FDR) was set to 1% for peptide and protein identifications. In the case of proteins identified from a single peptide, the ESI-MS/MS spectra were manually inspected and the identification considered reliable only if four or more consecutive C-terminal y n 00 fragment ions were assigned to intense signals and complementary b n ions were detected.
Data of protein identification is presented in Supplementary file S1.

DENV2 infection in presence of ELU AXC
Ninety-six well plates (Costar, 3597) were seeded with 3 Â 10 4 cells/well of the Huh 7.5 line and incubated 18-24 h at 37°C, 5% CO 2 until 90% confluence. The DENV2 inoculum was added at a multiplicity of infection (m.o.i) of 0.01 and infection was allowed to proceed for 2 h. Non-internalized virions were inactivated by a short treatment with Gly pH 3.0, the infection was allowed to proceed for 24 h, and viral yield was evaluated in cell supernatants by plaque formation assays in Vero cells (Fig. 3). For the assays involving a pre-incubation step at 4°C, the monolayers were pre-chilled for 5 min on ice, the indicated dilutions of plasma sample alone or mixed with DENV2 in DMEM w/o FBS were added, and the plates were further incubated for 90 min at 4°C. Afterwards, the monolayers were washed twice with DMEM 2% FBS (pre-chilled to 4°C). The plates incubated with virus:plasma sample mixtures were then incubated for 24 h at 37°C.
Post-infection activity was evaluated by infecting the cells as described above and then, after washing twice with DMEM w/o FBS, adding dilutions of the plasma samples in DMEM w/o FBS and incubating the plates for 6 h at 37°C, 5% CO 2 . Next, the monolayers were washed again and DMEM 2% FBS was added. The supernatants were collected 24 h post infection for virus titration in a plaque assay using Vero cells.

Appendix A. Supplementary material
Supplementary data associated with this article can be found in the online version at http://dx.doi. org/10.1016/j.dib.2015.12.016. Fig. 4. Results of acute toxicity testing. Concentration is expressed in % for TX100 concentration and mg/mL for ELU AXC . Data correspond to mean with range from two independent experiments, each performed in triplicate.