Comparison of Different Cell Lines for the Production of Recombinant Baculovirus Proteins

The levels of many recombinant proteins produced using the baculovirus expression vector (BEV) system are extraordinarily high (1 , 2 ), in many cases approaching 1000 mg/L, the level of polyhedrin expression. Unfortunately, other proteins that have been expressed in the BEV system are produced at much lower levels, which are often >5 mg/L (Table 1 ). Certainly, vector construction plays a major role in the level of protein expression, and many of the early reports of lower level expression using BEV can probably be traced to the use of suboptimal vectors that lacked sequences important to high level transcription from the polyhedrin promoter 3 ). However, more recent data on baculovirus expression levels using improved transfer vectors continue to reveal pro teins that are expressed at levels below 5 mg/L (4 –6 ). The questions that remain concern the reasons for such large differences and whether these reasons are in some way related to the insect cell line that is used.

Recombinant protein	Expression level	Reference
Secretory Glycoproteina
Tissue factor	0.5–2 mg/L	(5,22)
Tissue plasminogen activator	2-3 mg/L	(8,14)
Complement receptor	20.5–2 mg/L	(14)
Erythropoietin	10 mg/L	(11)
Interleukin	21–22 mg/L	(12)
Epidermal growth factor receptor	1mg/L	(6)
Epstein-Barr virus gp350/220	10 mg/L	(4)
Cytoplasmic Proteinsb
Polyhedrin	>500 mg/L	(12)
β-galactosidase	>500 mg/L	(18)
Adenovirus penton base	>200 mg/L	c
Chloramphenicol acetyltransferase	>l00 mg/L	(13)