From Cryoprecipitate to Virus-Safe High-Purity Concentrate

First of all, let me say a few words about the audience. I see so many familiar faces, faces that accompanied me over many years, and I am very moved that you all have come to Münster on the occasion of my 70th birthday. I would like to thank especially Professor Jürgens and Dr. Pollmann, who have brought us together here today.

It would have never occurred to me that our work at the Behringwerke on virus-safe coagulation factor concentrates should one day find such recognition. The fact that I can celebrate this in the form of today's symposium, together with all of you who contributed, gives me great pleasure indeed.

Before I come to the actual topic, I would like to thank Professor Sutor for his original laudatory speech, in which he related so many delightful stories that brought back fond memories.

I have to confess that I was rather reluctant to agree to this celebration symposium. Professor Sutor has already alluded to the reason why I am not a friend of large gatherings and events. Maybe that has to do with the fact that I come from a small village in Hinterpommern. It is called Rohr (translated as reed), probably because it is situated on a small, secluded lake in the woods. That is where I was born, in a lonely forester's house. Rohr lies between two larger cities: Schlawe and Rummelsburg. Being such a remote place, it was accordingly shrouded in legendary lore. The places beyond Rummelsburg were considered the back of beyond. In another saying, Rummelsburg and Schlawe supposedly had only one lark between them. In the morning the lark was singing in Rummelsburg and in the afternoon in Schlawe, or, according to still another saying, Rohr was a place where foxes and hares bid each other good night.

So much for my origins. Now I want to turn to my subject: ``From cryoprecipitate to virus-safe high purity concentrate.''

There is a chance that during my presentation I will refer to results that have already been mentioned by the previous speakers or are already known to you. I will therefore try to put the emphasis on the background setting during the initial development of pasteurized high-purity coagulation factor VIII (FVIII) concentrates and the associated problems that were encountered.

Most commercially available FVIII concentrates use cryoprecipitate as the starting material. Cryoprecipitate is prepared by thawing frozen plasma at low temperature. Under such conditions, certain plasma components, the so-called cryoglobulins, form an insoluble residue known as cryoprecipitate. It consists of cold-insoluble, high-molecular-weight proteins that are able to associate with other proteins and/or cells. Thus, for example, FVIII:C binds to von Willebrand factor (vWF), forming a FVIII-vWF complex, which in turn interacts with platelets. Another example is FXIII, which associates with fibrinogen or fibronectin that can bind to fibroblasts.

Cryoprecipitate contains predominately five proteins (Fig. [1]). Three of these are adhesion proteins, namely, fibrinogen, fibronectin, and vWF; all five are involved in the final phase of hemostasis. Cryoprecipitate is highly enriched in fibrinogen and fibronectin whereas the FVIII:C content is very low. For every 1 mg of FVIII:C, there are 14,000 mg of fibrinogen and fibronectin in comparison. As a result, the isolation of FVIII:C from the cryoprecipitate requires removal of large amounts of other proteins. The presence of contaminating proteinases, which can attack and inactivate the FVIII-vWF complex, complicates the purification schemes still further. However, these observations served as the starting point to search for ways and measures that would avoid losses during the enrichment and purification of FVIII:C. The efforts stretched over two decades! Looking back, it is evident, that there were a number of quite different reasons why the purification of FVIII-vWF from human plasma turned out to be such a challenging task.

REFERENCES

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