Secretion of Nonstructural Protein 1 of Dengue Virus from Infected Mosquito Cells: Facts and Speculations

Dengue virus nonstructural protein 1 (NS1) is a multifunctional glycoprotein. For decades, the notion in the field was that NS1 is secreted exclusively from vertebrate cells and not from mosquito cells. However, recent evidence shows that mosquito cells also secrete NS1 efficiently. In this review, we discuss the evidence for secretion of NS1 of dengue virus, and of other flaviviruses, from mosquito cells, differences between NS1 secreted from mosquito and NS1 secreted from vertebrate cells, and possible roles of soluble NS1 in the insect flavivirus vector.