| A suspended cell line QB-Tn9-4s derived from Trichoplusia ni embryos was cloned. The characteristics that the susceptibility of this cell line and BTI-Tn5B1-4 which is the most widely used insect cell line to Autographa californica multiple nuclear polyhedrosis virus (AcMNPV), and the production of AcMNPV and recombinant proteins were approximately same. But no clumps were produced when maximum density at late-log phase in serum medium cultures. In this paper, we described clone and isolation of culture cell from Trichoplusia ni cell line QB-Tn9-4s and reported their growth characteristics, production of virus and levels of recombinant protein expression:1. Eight cell clones were successfully isolated from the low passage suspended Trichoplusia ni cell line QB-Tn9-4s by use of 24-well cell clone plate (Greiner Labotechnik, Germany) and designated QB-Tn-A, QB-Tn-B, QB-Tn-C, QB-Tn-D, QB-Tn-E, QB-Tn-F, QB-Tn-G and QB-Tn-H, respectively.2. RAPD-PCR analysis of the genomic DNA from the eight clones confirmed their genetic identity as QB-Tn9-4s.3. The morphology and growth characterization among the cell clones were different . Clone QB-Tn-B was an attached clonal strain, while the others were suspended. Clones QB-Tn-A, B, C, D and E consist of approximately 60%～80% spindle-shaped cells, clones F, G and H were mostly made up of 44.5%, 49.5% and 80.0% comma-shaped cells, respectively.4. The population doubling times among six clones were different . Population doubling times of clone QB-Tn-A was the shortest with 21.37h and showed nearly equal to that of BTI-Tn5B1-4. Clone QB-Tn-E growed faster than parental cell line, while others clones did slower.5. The susceptibility of these clones to AcMNPV was investigated. The selected clones were highly susceptible to AcMNPV virus with an infection of over 92% cells with production of around 85～110 OBs per cell. The clone QB-Tn-A produced the highest number of OBs per cell when compared with BTI-Tn5B1-4, QB-Tn9-4s and Sf-9. The productions of AcMNPV buded virus (BV) of these clones tended to different. The clones QB-Tn-A and E were similar to the parental cell line QB-Tn9-4s (3.37×107 TCID50/mL), and the others were lower than the parental cell line.6. The production ofβ-galactosidase of clone QB-Tn-A was highest with 1.91×104IU/mL and had significant difference when compared to the parental cell line (1.38×104IU/mL). QB-Tn-B cells produced much more secreted alkaline phosphatase (SEAP) than its parent, QB-Tn9-4s, and at seven dsys p.i., the clone expressed 3.51-fold more SEAP as compared to QB-Tn9-4s cells.
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