Abstract
Serumfree cultures of insect cells play an important role in the fields of protein engineering, medicine, and biology. In this paper, the suspension cell line QB-Tn9-4s of Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) was successfully adapted to serumfree Sf-900 III medium and passaged for 52 generations. The adapted QB-Tn9-4s cells grew faster. Their population doubling time shortened from 27.4 hr in serum-containing medium to 24.1 hr, and their maximal density increased by 1.83-fold, reaching 3.50 ×10 6 cells/mL in serumfree culture in T-flasks. The cells readily adapted to spinner culture, with maximum cell density of 4.40 × 10 6 cells/mL in a spinner flask. Although the infection rate of Autographa californica multiple nucleopolyhedrovirus and production of occlusion bodies (OBs) of the adapted QB-Tn9-4s cells were 91.0% and 85.4 OBs/cell, respectively, similar to those of QB-Tn9-4s cells cultured in serum-containing medium and control BTI-Tn5B1-4 cells, their budded virus titer was 4.97 ×10 7 TCID50/mL, significantly higher than those of the latter two. In addition, the expression levels of β-galactosidase at six days postinfection and secreted alkaline phosphatase at seven days postinfection in the adapted QB-Tn9-4s cells reached 2.98 ± 0.15×10 4 IU/mL and 3.34 ± 0.13 IU/mL, respectively, significantly higher than those of QB-Tn9-4s and control BTI-Tn5B1-4 cultured in serum-containing media. The above findings establish a foundation for industrial production of virus and recombinant proteins in QB-Tn9-4s serumfree culture.
Highlights
Insect cell lines are of great importance in the production of baculovirus and recombinant proteins
BTI-Tn5B1-4 cells are highly susceptible to baculovirus and could provide superior production of occlusion bodies (OBs) and recombinant proteins when compared to other insect cell lines
An alphanodavirus named Tn5 cell line virus was identified during production of hepatitis E virus-like particles in BTITn5B1-4 cells infected with a recombinant baculovirus vector (Li et al 2007), there is a serious risk of contamination when using virus-like particles to produce vaccines or recombinant proteins for therapeutic purposes in BTI-Tn5B1-4 cells (Merten 2007)
Summary
Insect cell lines are of great importance in the production of baculovirus and recombinant proteins They are generally cultured in media containing a certain percentage of serum to support cell growth and proliferation. Sf-9 cells could yield more budded virus (BV), but they produce less OBs and recombinant proteins Both Sf-9 and BTI-Tn5B1-4 are adherent cells. QBTn9-4s is a suspension T. ni cell line established in our laboratory It has comparable production levels of OBs and recombinant proteins to BTI-Tn5B1-4 cells and does not agglomerate at high density in culture (Meng et al 2008). The results showed that in serum-free medium, QB-Tn9-4s cells could grow well and produce high levels of OBs and recombinant proteins, showing broad application potentials
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