Analytical approach for the extraction of recombinant membrane viral glycoprotein from stably transfected Drosophila melanogaster cells.

Parameters for storage, lysis and concentration of Drosophila melanogaster Schneider 2 (S2AcRVGP) cells expressing the recombinant rabies virus glycoprotein (RVGP) were studied with regard to RVGP quantification by ELISA, for productivity evaluation and future purification. Lysis buffers were formulated with Tris, NaCl, glycerol, EDTA, KCl, Na(2)PO(4), MgCl(2), PMSF and NP-40 or CHAPS. S2AcRVGP cells (10(7) cells at the exponential growth phase) were frozen at -20 degrees C as a dry pellet, suspended in buffer (B) formulations or after treatment with lysis buffer (LB) formulations. They were then thawed as cell pellets or with B formulations or PBS at 4 degrees C or at room temperature and then lysed with LB formulations. For RVGP quantification by ELISA, a protocol was chosen of cell preparation including cell freezing as dry pellet, cell thawing at 4 degrees C with B4 (Tris, NaCl, MgCl(2), PMSF) and cell lysis with the LB4 (B4 + NP-40) since it fulfilled requirements of high RVGP detection, and was easily performed with mixtures freezing quickly, and a cost-saving LB formulation could be used. Using these established conditions, we examined the optimal cell concentration for RVGP quantification by ELISA. Results showed that an increase in the RVGP detection (from 62.5 to 1083 ng/10(7) cells) paralleled a decrease in the cell number (3 x 10(7) - 10(5) cells) used. The NP-40 concentration present in the LB4 was further investigated as a function of the cell number used for sample preparation. Previous results were confirmed indicating that higher NP-40 concentrations led to a decreased detection of RVGP. Altogether our data clearly pointed out the crucial effects of cell freeze, thaw, lysis and concentration on immune detection of recombinant membrane glycoproteins and can be useful as a guideline for sample preparation for this purpose.