Effect of detergents on the structure of integral membrane proteins of Sendai virus studied with size-exclusion high-performance liquid chromatography and monoclonal antibodies

Purification of the major envelop protein GP5 of porcine reproductive and respiratory syndrome virus (PRRSV) from native virions

Porcine reproductive and respiratory syndrome virus (PRRSV) is the cause of an economically important swine disease that has been devastating the global swine industry since the early 1990s. The current PRRSV vaccines are not very effective largely due to heterogeneic nature of the virus. The major envelope protein, GP5, exposes outside the virion, induces neutralizing antibodies, and thus is a primary target for developing a subunit vaccine. In this study, we report a process for purification of GP5 protein from native virions of PRRSV propagated in MARC-145 cells. PRRSV virions were first purified and concentrated through sucrose cushion ultracentrifugation. GP5 protein was subsequently solubilized with Triton X-100 detergent for further processing. Cation exchange chromatography (CEX) was utilized for partial fractionation of GP5, although the viral nucleocapsid protein (N) was a major impurity in CEX elution fractions. During a second chromatographic step, hydrophobic interaction chromatography (HIC) further purified GP5 protein by means of a two-stage elution scheme. Pure GP5 protein was eluted from the HIC resin in the second HIC elution stage by Triton X-100 displacement; however the protein is present as a homodimeric/tetrameric aggregate. This process may be useful in PRRSV subunit vaccine development.

Purification of the integral membrane glycoproteins D of herpes simplex virus types 1 and 2, produced in the recombinant baculovirus expression system, by ion-exchange high-performance liquid chromatography

Selective elution of Sendai virus integral membrane proteins by ion-exchange high-performance liquid chromatography (HPIEC) using different detergent concentrations was reported before [S. Welling-Wester, M. Freijlbrief, D.G.A.M. Koedijk, M.A. Braaksma, B.R.K. Douma and G.W. Welling, J. Chromatogr., 646 (1993) 37]. In the present study this novel approach was applied to the purification of the integral membrane glycoprotein D of Herpes simplex virus type 1 and 2. The glycoproteins D of types 1 (gD-1) and 2 (gD-2) were cloned into the baculovirus expression system and produced in protein-free cultured insect cells. Detergent extracts of recombinant baculovirus-infected insect cells containing gD-1 or gD-2 were prepared using pentaethyleneglycol monodecyl ether, for extraction (final concentration 2%, w/v). The same detergent was used as additive in the elution buffers for HPIEC on a Mono Q HR 5/5 column. At low (0.005%) detergent concentration, most of the proteins present in the extract including part of gD were eluted with the sodium chloride gradient whereas a subsequent blank run using the same gradient at higher detergent concentration (0.1%) resulted in selective elution of pure gD.

Comparison of detergents for extraction and ion-exchange high-performance liquid chromatography of Sendai virus membrane proteins

The integral membrane proteins of Sendai virus, haemagglutinin-neuraminidase (HN) and fusion protein (F) were extracted from purified virions with a non-ionic and two zwitterionic detergents, i.e., pentaethylene glycol monolauryl ether (C12E5), lauryldimethylamine oxide (LDAO) and dodecyldimethylammoniopropane-1-sulphonate (SB12), respectively. The extracts were subjected to ion-exchange high-performance liquid chromatography (HPIEC) using 0.1% of the detergent in the eluent on four different columns (MA7Q, Zorbax BioSeries SAX, Mono Q and PL-SAX) with a quaternary amine as interacting ligand and with different pore sizes: non-porous and 30, 80 nm and 400 nm, respectively. The relative recoveries of protein were similar for all the columns. The highest recovery of HN and F protein and the best separation were obtained with C12E5. Analysis of HPIEC fractions with monoclonal antibodies directed against conformational epitopes showed that C12E5 had less effect on the conformation than the other two detergents.

Molecular mass, biochemical composition, and physicochemical behavior of the infectious form of the scrapie precursor protein monomer

A highly purified fraction obtained from scrapie (263-K strain)-infected hamsters' brains by an alternative procedure without proteinase K treatment contained a protease-resistant form of the scrapie precursor protein (PrPSc) and infectivity of 9.9 +/- 0.7 log LD50/ml. Polyclonal antibodies produced against hamster scrapie amyloid protein (PrP27-30) and used in a neutralization test diminished infectivity of the PrPSc preparations by 1.6 log after intracerebral inoculation and by 1 log after intraperitoneal inoculation. PrPSc was subjected to size-exclusion HPLC; greater than or equal to 60% of the eluted infectious units were recovered from the peak with an apparent mass of 30.4 +/- 0.6 kDa. Characterization by UV absorption spectra, SDS/PAGE, immunoblots, N-terminal amino acid sequence, and neutral sugar and amino sugar analyses demonstrated homogeneity of the infectious units. The neutral sugar and amino sugar compositional analyses revealed high mannose, glucosamine, fucose, and sialic acid content. This demonstrated an extensive posttranslational modification by the complex type of N-linked glycosylation and glycane core of C-terminal glycolipid of PrPSc. The results correspond to the predicted size, composition, and sequence of PrPSc and indicate that this protein may be the only component of scrapie infectious unit or the infectious form of scrapie precursor.

Comparison of non-ionic detergents for extraction and ion-exchange high-performance liquid chromatography of Sendai virus integral membrane proteins

The integral membrane proteins of Sendai virus haemagglutinin-neuraminidase (HN) and fusion protein (F) were extracted from purified virions with 2% of a non-ionic detergent, i.e., polyoxyethylene alkyl ethers varying by 8-14 hydrocarbon units in the alkyl chain and by 4-8 ethylene glycol units in the oxyethylene chain. Triton X-100 and octyl glucoside were included as reference detergents. The hydrophile-lipophile balance (HLB) and the critical micelle concentration (CMC) of the detergents were determined. A decrease in length of the oxyethylate by 8-5 ethylene glycol units and an increase in the alkylate by 8-12 hydrocarbon units resulted in higher yields of extracted proteins. The highest yields were obtained for C12E5 with an HLB of 11.7. Yields of extracted protein could be correlated with the HLB values of the polyoxyethylene alkyl ethers. The structural integrity of HN and F was not affected during extraction by either detergent as measured by their reactivity with monoclonal antibodies directed against native HN and F. Extracts were subjected to anion-exchange high-performance liquid chromatography (HPLC) on a Mono Q column in the presence of 0.1% of the detergent used for extraction. Eluate fractions were analysed by sodium dodecyl polyacrylamide gel electrophoresis and recoveries of HN and F protein were determined by size-exclusion HPLC. The immunological activity of HN and F was tested in an enzyme-linked immunosorbent assay. The highest recoveries of HN and F (80%) were obtained with C10E5 in the elution buffer. HN and F were partially purified and the immunological activity was well preserved.

Comparison of ion-exchange high-performance liquid chromatography columns for purification of Sendai virus integral membrane proteins

The recovery and separation of the integral membrane proteins, the haemagglutinin-neuraminidase (HN) and the fusion protein (F), from a Sendai virus detergent extract were compared on three different ion-exchange high-performance liquid chromatography (IE-HPLC) columns: Mono Q, TSK DEAE-NPR and Zorbax BioSeries SAX. The detergent, either 1-O-n-octyl-beta-glucopyranoside (octylglucoside) or decyl polyethylene glycol-300 (decyl PEG-300), used for extraction of HN and F proteins from the virions, was also present in the elution buffers at a concentration of 0.1%. Recovery of HN and F proteins was primarily dependent on the detergent present in the eluent, resulting in yields of HN varying from 18 to 28 and 56 to 67%, when octylglucoside and decyl PEG-300, respectively, were used. The highest yield for HN protein was obtained by separation on either a Mono Q or a TSK DEAE-NPR column with decyl PEG-300 as the additive. Yields of F protein were lower, and the highest recovery of 46% was found in the presence of decyl PEG-300 by separation on the Mono Q column. Analysis of the fractions by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and by size-exclusion HPLC indicated that the HN protein eluted in the presence of decyl PEG-300 from the Mono Q and the TSK DEAE-NPR columns was obtained in pure form, while the F protein was slightly contaminated with HN. Analysis of the fractions with monoclonal antibodies directed against conformational epitopes of HN and F proteins indicated that after IE-HPLC the conformation of the proteins is largely retained.