Endogenous retrovirus particles and their repercussion effects on the growth behaviour of continuous hybridoma cultivation processes.

Hybridoma cells used for the production of monoclonal antibodies are also known to form growth inhibitory substances. Growth inhibitors already described in the literature belong to the class of peptides and proteins likeTGF-ss (Transforming Growth Factor-ss). The endogenous retrovirus particles - a further potential substance producing this kind of effect - are described here. To examine whether the retrovirus particles participated in growth inhibitory effects hybridoma cells were cultivated in continuous perfusion mode by using a special reactor set-up. A rapid increase of the signal in the supernatant which coincided with a decrease of viability could be observed by monitoring the reverse transcriptase-activity during this type of fermentation process. The examination of concentrated and fractionated supernatant from this period showed growth inhibitory effects in the biological assay (MTT-assay). Investigations of respective fractions demonstrated retrovirus particles with reverse transcriptase-activity. Based on RT-PCR data it was shown that only inhibitory fractions contain retrovirus particles which were of E-MuLV and MCF origin.