In summary, all FluHA, FluM, CMVpp65, EBNA3 and PyCSP IVTT recombinants could be produced in the E. coli cell-free IVTT system, using the manufacturer's recommended conditions. However, at least 70% of each IVTT product was insoluble. In contrast, only two of the four viral antigens could be produced in the insect cell based system but in this system at least 90% of the product was soluble.