Sudden drop in Hybridoma viability

[Haldiwala]

Hi,
I am culturing a mouse hybridoma cell line. The problem I'm facing is that cells grow find during the first four days of a batch culture (initial cell density 100,000 cells/mL) and reach upto 2-3 million cells/mL by day 5. After that cells start to die and there is drop in viable cell number every day until by day 8 the culture is finished. In short, there is no stationary phase of batch culture and from late exponential phase, cells start to die. Could anyone surmise what is going on here and how to prevent this sudden drop in cell viability. If you need more info, please let me know.
Thanks.

[Jyerka]

Haldiwala-
What you're seeing is normal for hybridomas. Feeding will get you a bit of an extended phase- make sure you have amino acids etc./maybe add some hydrolisates, do an osmolarity shift to get them working hard- but you will still get this steep viability curve. They will not maintain as CHO etc. You need to perfuse to get an efficient continuous harvest.
Are these recently off selection? Recently off serum?

[Haldiwala]

Thanks for your prompt reply and suggestions to try. They are not off serum recently and were selected at least 6 months ago. I'll look into developing a fed-batch protocol and get back if more questions arise.

Kind regards,

Arshad