BACULOVIRUS EXPRESSION OF THE RESPIRATORY SYNCYTIAL VIRUS FUSION PROTEIN USING TRICHOPLUSIA-NI INSECT CELLS

Respiratory syncytial virus (RSV) is a major viral pathogen responsibl e for severe respiratory tract infections in infants, young children, and the elderly. The RSV fusion (F) protein is highly conserved among RSV subgroups A and B and is the major protective immunogen. A genetic ally-engineered version of the RSV F protein was produced in insect ce lls using the baculovirus expression system, To express a secreted for m of this protein, the transmembrane domain was eliminated by removing the region of the gene encoding 48 amino acids at the C-terminus. Pro duction of the truncated RSV F protein (RSV-Fs) was compared in two di fferent insect cell Lines, Spodoptera frugiperda (Sf9) and Trichoplusi a ni (High Five). The yield of RSV-Fs secreted from High Five insect c ells was over 7-fold higher than that from Sf9 insect cells. Processin g of the RSV-Fs protein was also different in the two insect cell line s, N-terminal sequencing demonstrated that while most of the RSV-Fs pr otein secreted by High Five cells was correctly processed at the F-2-F -1 proteolytic cleavage site, most of the RSV-Fs protein secreted by S f9 cells was unprocessed or incorrectly processed. Antigenicity of the major RSV F neutralization epitopes was maintained in the RSV-Fs prot ein secreted from High Five cells. The RSV-specific neutralizing antib ody titres in the sera of cotton rats immunized with the RSV-Fs protei n were equivalent to those in the sera of animals intranasally inocula ted with live RSV. Animals immunized with either Live RSV or the immun oaffinity purified RSV-Fs protein from High Five cells were completely protected against live virus challenge.