Viral and cellular determinants of polarized trafficking of viral envelope proteins from insect-specific and insect-vectored viruses in insect midgut and salivary gland cells.

Systemic viral infection of insects typically begins with the primary infection of midgut epithelial cells (enterocytes) and subsequent transit of the progeny virus in an apical-to-basal orientation into the hemocoel. For insect-vectored viruses, an oppositely oriented process (basal-to-apical transit) occurs upon secondary infection of salivary glands and is necessary for virus transmission to non-insect hosts. To examine this inversely oriented virus transit in these polarized tissues, we assessed the intracellular trafficking of two model viral envelope proteins (baculovirus GP64 and vesicular stomatitis virus G) in the midgut and salivary gland cells of the model insect, IMPORTANCE: Viruses that use insects as hosts must navigate specific routes through different insect tissues to complete their life cycles. The routes may differ substantially depending on the life cycle of the virus. Both insect pathogenic viruses and insect-vectored viruses must navigate through the polarized cells of the midgut epithelium to establish a systemic infection. In addition, insect-vectored viruses must also navigate through the polarized salivary gland epithelium for transmission. Thus, insect-vectored viruses appear to traffic in opposite directions in these two tissues. In this study, we asked whether two viral envelope proteins (VSV G and baculovirus GP64) alone encode the signals necessary for the polarized trafficking associated with their respective life cycles. Using