In order to determine the time course of expressed antigen in silkworm and the optimum acquisition time for large scale's production, haemolymph from 10 silkworms was harvested every 12 h beginning at 60 hpi and stored at 220uC. Subsequently, the haemolymph was diluted to 1000 folds for detection of expression products (Fig. 3 ). There was a little at 60 hpi, and the accumulation of recombinant products were dramatically increased from 84 hpi and kept at the high levels during the late phase of infection. So, expressed antigen could be harvested at 108-120 hpi (at the condition about the mean rearing temperature of 25uC).