Sialic acids in Trichoplusia ni and Danaus plexippus egg glycoproteins

Baculovirus expression vector insect cell system (BEVIS) is useful for high level production of human therapeutic proteins. However, it has been reported that recombinant glycoproteins produced from this system are, in many cases, biologically inactive or less active than authentic counterparts, due to incomplete glycosylation potential of insect cells used so far, producing recombinant proteins with only high- or paucimannosidic oligosaccharides without sialylation. The presence of sialic acids in insects is still controversial. Egg proteins of Trichoplusia ni and Danaus plexippus were isolated, and the presence of sialic acids was examined using reverse-phase fluorescent HPLC after derivatization of samples with 1,2-diamino-4,5-methylenedioxybenzene (DMB). The proteins of both eggs were shown to contain 5-N-acetylneuraminic acid. The results suggest that both insects may be able to produce proteins with sialylated complex-type oligosaccharide chains.