We also evaluated production of the viral antigens in an insect cell based cell-free system (PyCSP not tested). In a limited number of attempts using the manufacturer's recommended conditions, only two of the four viral protein targets (FluM and CMVpp65) could be produced in this eukaryotic system. However, in contrast to results with the E. coli system, solubility analysis showed that at least 90% of the recombinants were soluble and partial polypeptides were not detected ( Figure 2 ).