Tumour-necrosis factor-alpha (TNF-alpha) is a cytokine that contributes to a variety of inflammatory disease states. The protein exists as a membrane-bound precursor of relative molecular mass 26K which can be processed by a TNF-alpha-converting enzyme (TACE), to generate secreted 17K mature TNF-alpha. We have purified TACE and cloned its complementary DNA. TACE is a membrane-bound disintegrin metalloproteinase. Structural comparisons with other disintegrin-containing enzymes indicate that TACE is unique, with noteable sequence identity to MADM, an enzyme implicated in myelin degradation, and to KUZ, a Drosophila homologue of MADM important for neuronal development. The expression of recombinant TACE (rTACE) results in the production of functional enzyme that correctly processes precursor TNF-alpha to the mature form. The rTACE provides a readily available source of enzyme to help in the search for new anti-inflammatory agents that target the final processing stage of TNF-alpha production.

Today, many thousands of recombinant proteins, ranging from cytosolic enzymes to membranebound proteins, have been successfully produced in baculovirus-infected insect cells. Yet, in addition to its value in producing recombinant proteins in insect cells and larvae, this viral vector system continues to evolve in new and unexpected ways. This is exemplified by the development of engineered insect cell lines to mimic mammalian cell glycosylation of expressed proteins, baculovirus display strategies and the application of the virus as a mammalian-cell gene delivery vector. Novel vector design and cell engineering approaches will serve to further enhance the value of baculovirus technology.Over the past 20 years the baculovirus-insect cell expression system has become one of the most widely used systems for routine production of recombinant proteins [1][2][3][4][5][6] . A number of technological improvements have eliminated the original tedious procedures required to identify and isolate recombinant viruses, increasing the popularity of the system. These include development of a wide variety of transfer vectors, simplified recombinant virus isolation and quantification methods, advances in cell culture technology and the commercial availability of reagents. These enhancements have resulted in a virus-based expression system that is safe, easy to use and readily amenable to scale-up.In addition, biotechnology now uses baculoviruses in applications beyond the production of proteins in insect cells and larvae. These include the development of strategies for displaying foreign peptides and proteins on virus particles and the insertion of mammalian cell-active expression cassettes in baculoviruses to express genes efficiently into many different mammalian cell types. Baculoviruses engineered to display foreign peptides and proteins on the viral surface have proven particularly useful as immunogens and both surface display and capsid fusions may provide further opportunities for enhancing and targeting baculovirus-mediated transduction of mammalian cells.Here, we review recent advances in baculovirus-insect cell protein production, baculovirus display and the development and application of baculoviruses as mammalian-cell genedelivery vectors (Fig. 1).

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