To explore virus-like particles formation of dengue virus serotype type 2 (DENV-2) structural proteins of, C, prM, E were expressed in silkworm larvae using recombinant Bombyx mori nucleopolyhedroviruses (BmNPV). Each recombinant BmNPV bacmid coding the 2C-prM-E polypeptide and E protein fused with the signal peptide of bombyxin from B. mori was injected into silkworm larvae. The expressed proteins were collected from hemolymph and fat body, and purified using affinity chromatography. E protein was observed at 55 kDa. The DENV virus-like particles (DENV-LPs) with a diameter approximately 35 nm was observed using transmission electron microscopy (TEM) and immunogold-labelling TEM analysis. The binding of each partially purified proteins to heparin, one of receptors for DENV was confirmed. DENV-LPs were secreted in silkworm larval hemolymph even still low amount, but the E protein and heparin binding function were confirmed.

This is the first finding that chitosan/BmNPV bacmid DNA nanocomplexes can rival the performance of commercially available transfection reagents for the expression of recombinant proteins in Bm5 cells and silkworm larvae.

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Materials and bacterial strainsFruit bodies of H. erinaceus cultivated by the Hokuto Corporation (Nagano, Japan) were freeze-dried and milled to prepare H. Erinaceus Powder (HEP). The bacterial strains P. gingivalis ATCC 33277 and S. gordonii ATCC 10558 were purchased from the American Type Culture Collection (ATCC: Manassas,