Baculovirus has recently been emerged as a new tool for vaccine vector development since it has many advantages as a vaccine platform (28) (29) (30) . First, baculovirus, which has been used to overexpress recombinant proteins in insect cells, is neither replication-competent nor pathogenic in mammalian cells, making it safer vaccine vector than other mammalian viral vectors. In addition, baculovirus-based vaccines produced in insect cells are not contaminated by LPS. Second, baculovirus-based vaccine possesses several advantages upon production, such as easy manipulation, relatively simple scale-up, and high titers (11, 31) . Thirdly, there is no pre-existing vector immunity against baculovirus in mammals, which enables baculovirus to escape vector neutralization by pre-existing immunity during in vivo delivery (19) . Lastly, baculovirus has the ability to stimulate strong innate immunity, exhibiting strong adjuvanticity itself. It has been previously shown that inoculation of wild-type baculovirus alone can stimulate the secretion of inflammatory cytokines from innate immune cells and confer protection from lethal virus infection in mice (16) . Consistent with this report, intranasal inoculation of control baculovirus also provided partial protection against live RSV challenge in our study (Fig. 6) . The baculovirus-mediated stimulation of innate immunity might be associated with the induction of type I interferons, mediated by both TLR9-dependent (32) and TLR9-independent pathways (33) . Thus, it becomes evident that baculovirus can act as a natural adjuvant by stimulating innate immunity and be used as a safe and effective vaccine carrier.