Effect of prolactin on progenitor cells of the hemopoietic system

Abstract

A synergistic factor (SF) enhanced the infection of Autographa californica nuclear polyhedrosis virus (AcNPV) in vitro. When the AcNPV was inoculated together with the SF to a Spodoptera frugiperda cell line, the enhancement of AcNPV increased dose-responsively to the SF. Enhancement, however, did not require the coinoculation of AcNPV and SF since it occurred in the pretreatment of the cells with the SF alone and even after a 24-hr interval of SF pretreatment. There was a difference in the activity of the SF on the AcNPV propagated in a cell culture system during various periods of virus propagation. When the SF was treated with phospholipase C, the enhancement of AcNPV infection did not occur in vitro and confirmed our previous study in vivo. The cells appeared to phagocytize the SF and the uptake occurred rapidly (within 1 min), but there was no uptake when the SF was treated with phospholipase C. These results indicate that the SF is a binding molecule in which the phospholipid component is essential for its phagocytosis and enhancement of baculovirus infection. The SF appears to have two different binding sites, one for the cell plasma membrane and the other for the enveloped virion.