Serial Passage Of Baculorvirus In A Transfected P35 Gene Insect Cell Line

The replication of MsNPV and AcNPV in a Mythimna separate cell line, NEAV-Ms-7311 and a transfected gene Mythimna separate cell line, TMsF, is presented. The result showed that TMsF cells was highly susceptible to AcNPV with 74% of the infection rates postinfection.15 clones were obtained by cell cloning. After several passages, 11 clones of them were selected and named as CT-1, CT-2.. .CT-11. They were examined for their resistance to nutritional stress in PBS and infection of AcNPV. CT-7 and CT-8 clones which appeared strong resistance to PBS and high products of OBs were obtained. AcNPV was subsequently grown in these cell lines for 10 serial passage, result showed infectivity and OB yields dropped off rapidly in CT-8 and TMsF cell lines and did not in CT-7.The morphology of CT-7, grown in Grace medium, generally consisted of spindle cells with presence of some round cells. The CT-7 cell line reached maximum density of 9 ×10⁵ cells/ml at five days and the population doubling time is 37.1h. Wild-type AcNPV (MOI:10) infected the CT-7 cells with an infection of 80.5% of the cells and the production of occlusion bodies (OBs) by it was high, hightest of 66.4 OBs/cell.Budded virus titer reached a maximum titer at the third passage at the same time in two lines. The CT-7 cell line reached maximum titer of 3 ×10⁸ TCID₅₀/ml and did not drop off obviously in later passage. It was higher than in TMsF cell line. But the chang trend of budded virus titer descended obviously from 2.7×10⁷TCID₅₀/ml to 1.4×10⁶ TCID₅₀/ml in TMsF cell line.CT-7 cells showed high resistance to nutrient stress in comparison with parental cell line TMsF when cells were exposed to PBS. Cell viability was 86% with CT-7 after one day in PBS. Four days later, 6% CT-7 cells were survived but TMsF cell line died within two days.Bioassay was performed using OBs generated from different viral passage to examine the relationship between mortality and passage number. CT-7 cells showed higher morility for Spodoptera exigua larvae and changed smoothly from 47%⁶3%.But TMsF cell line was opposite.AcNPV was replicated in CT-7 cells for 10 passages continuously and there was no significant change in morphology of the occlusion bodies, OBs production and virus titer...