A synergistic factor of an insect granulosis virus agglutinates insect cells

Summary The synergistic factor (SF), a lipoprotein which enhances in vivo and in vitro baculovirus infections, occurs in the matrix of the occlusion body (capsule) of a granulosis virus of the armyworm,Pseudaletia unipuncta. The SF attaches to certain areas on the surfaces of cell plasma membranes of cultured insect cells, resulting in marked cellular agglutination. The minimal amount of SF detectable by agglutination is approximately 3 g/ml. Cultured cells of 6 out of 10 insect species in 3 orders are agglutinated by the SF, but not those of 2 mammalian species and the erythrocytes of 8 vertebrate species.We thank Dr M. Nagata and Dr T. Yamamoto for preparing the synergistic factor and R.T. Hess and E.M. Omi for technical assistance. We also thank the donors who provided the cell lines. This work was supported by the National Science Foundation under Grant No. PCM-8201247.