Fig 5.

Two modes of infection in the midgut. Most baculoviruses use the midgut only to produce the first generation of BV progeny that bud out from the basal lateral side of the midgut cell to infect other tissues. ODVs that enter midgut cells may (1) bypass virus replication in the midgut cell or (2) initiate virus replication. When MNPVs bypass replication, most nucleocapsids translocate to the basolateral side of the midgut cell. One or a few nucleocapsids enter the nucleus, unpackaged, and expresses envelope fusion protein (efp) genes. EFP proteins are translocated via the endoplasmic reticulum (ER) and Golgi to the basal lateral side of the cell where they meet up with nucleocapsids which then bud out. This is the passage effect. When MNPVs replicate in the midgut cell significantly greater numbers of BV are produced. However, this mode of infection requires 8–12 h vs 30 min when the virus bypasses viral replication.