Baculoviruses are rod-shaped (baculum in Latin means 'stick') dsDNA viruses found mainly in insects. The most common baculovirus used for expression studies is Autographa californica multiple nuclear polyhedrosis virus (AcMNPV), which relies on the lepidopteran species Spodoptera frugiperda and Trichoplusia ni as host insects. AcMNPV particles surround themselves with a protective matrix consisting of the protein polyhedrin, which permits survival in the environment and efficient spread to new hosts. Under the control of the extremely strong promoter pPolh, polyhedrin is expressed at extremely high levels (up to 50% of all cellular protein) at the end of the baculovirus life cycle. The baculovirus expression system makes use of the fact that in cell culture a polyhedrin coat is not essential for virus propagation and thus heterologous proteins can be expressed under the control of the pPolh promoter (see O'Reilly et al. (1997) for further reading). Using the sf9 insert cells, Yrbio offer the baculovirus expression services.