RELATIONSHIP BETWEEN OXYGEN-UPTAKE RATE AND TIME OF INFECTION OF SF9 INSECT CELLS INFECTED WITH A RECOMBINANT BACULOVIRUS

Oxygen uptake rates (OUR) of Sf9 insect cells propagated in a serum-fr ee medium (SF900II, Gibco) and of cells infected with a recombinant Ac NPV were investigated before and after infection in a laboratory-scale bioreactor. The volumetric OURs of uninfected and exponentially growi ng cells were found to be proportional to the cell density. For infect ed cultures, the specific OUR of cells increased immediately after add ition of virus and a maximum of 1.3 times the value of uninfected cell s was noted for all the cultures between 8 to 30 hours post infection, which coincides with the period at which most viral replication and t he majority of DNA synthesis takes place. It was observed that the rat e of rise in the specific OUR decreased as the eel density at the time of infection increased, which meant that the later the infection, the later the maximum sOUR was observed. We therefore suggest that OUR me asurement can be used to reflect the efficiency of a batch infection. Carbohydrate and amino acid consumption rates from an infected run wer e analysed in an effort to identify substrate(s) that may be used at i ncreased rates to fuel the rise in oxygen demand observed early in the infection cycle. No observable rise in the consumption rates of gluco se or glutamine, which are the major energy sources for animal cells, were seen after infection but an increase in the consumption rates of some amino acids suggests that infected Sf9 cells may utilise amino ac ids at an enhanced rate for energy post infection.