Baculoviruses are a group of rod-shaped, enveloped, double-stranded DNA viruses having a circular, supercoiled genome varying from 90 to 160 kb in size. They have been successfully used for efficient expression of engineered proteins. A baculovirus system is more attractive than other protein expression systems because of its high level expression, posttranslational modification ability, and safety for use in humans (Smith et al., 1983, Mol. Cell Biol. 3, 2156-2165).
However, the conventional baculovirus expression system has one disadvantage. More specifically, host cells infected with baculoviruses lyse upon maturation of viral progenies. During the cell lysis, (1) the engineered protein leaks and is difficult to recover, leading to low protein yields; (2) the host cell lysosomes break down and release proteases, causing degradation of the engineered protein; (3) endoplasmic reticules and Golgi bodies also break down, resulting in poor posttranslational modification and blockade of intracellular trafficking of a membrane or secretory engineered protein. Thus, there is a need for a non-lytic baculovirus.