Sterilization of Blood and Its Derivatives With Vitamins

The invention relates to a method for sterilization of blood, plasma, blood- and plasma derivatives, cell suspensions or similar with a physiologically innocuous sterilant.

Human blood or human plasma or derived products potentially entail the risk of transmitting viral infection. In particular, human pathogenic lipid viruses such as HIV, HNANBV and HBV play a special role. For this reason, preparations derived from human blood or plasma must be virus inactivated.

Clotting preparations such as F VIII or F IX concentrates can be sterilized by means of heat (EP 0 037 078), but require appreciable amounts of stabilizers in order to stand such a treatment. In other methods, the preparation is heated in the lyophilized state, with additional use of organic solvents, pressure or steam in combination.

Chemical agents such as a combination of lipid solvents and detergents or beta-propiolactone in combination with UV irradiation (EP 0 014 333) are also used.

All these methods display various advantages, but also disadvantages which impair the application or the efficacy. The substances in solution added for heat sterilization must be removed again in the clotting factor end product. In heating in the lyophilized state, the poorly standardized residual moisture content determines the effectiveness of the method. In addition, numerous components of the blood cannot be lyophilized. Beta-propiolactone/UV can be used to sterilize F VIII only with loss of yield. Solvents and detergents must be removed again from biological material by elaborate processes.

So far, sterilization of cell suspensions is not possible. For example, heat sterilization methods are not suitable for erythrocyte suspensions, since the cells are destroyed. Chemical methods (detergents, solvents or beta-propiolactone) also bring about complete or partial hemolysis of the cells. Suspensions of white blood cells also cannot be sterilized with this method.

To summarize, unphysiological conditions and substances are used in all the sterilization methods so far described.

The invention is based on the task of providing a virus inactivation procedure which works under physiological conditions and with physiological substances, which is suitable for sterilization of blood/plasma or their derivatives as well as for cell suspensions. A physiologically well-tolerated substance which can remain in the biological material to be sterilized is used as sterilizing agent.

In accordance with the invention, this problem was resolved by use of vitamins or water soluble salts thereof as sterilizing agents. Vitamins are natural physiological substances of which the anti-infectious, health-promoting activity is already known. Moreover, vitamins do not have to be removed from the biological material to be sterilized, since the human body relies on supply of vitamins. Preferred vitamins are vitamin A, B, B.sub.1, B.sub.6, B.sub.12, C and E. Preferred salts are the acetates, such as vitamin A- and E-acetate.

Sterilization is carried out in that the biological material to be sterilized is mixed with 0.01 to 1.0 weight % of a vitamin (per volume% sterilisate) and preferably 0.2%, the pH value is adjusted to 5.6 to 8.5 and incubation is carried out with stirring for up to 24 hours at 10.degree. C. to 50.degree. C. Preferentially, the pH value is 7.15 and the temperature is 23.degree. C. to 37.degree. C., and more preferentially 23.degree. C. or 37.degree. C. The preferred sterilization time is three to four hours. If necessary, a dissolution mediator can be added to improve the solubility of the vitamin. A preferred solubilizer is e.g. Tween 80.

The method in accordance with the invention enables virus inactivation in blood, blood cells, blood plasma, blood serum, constituents of blood cells (e.g. interferons, interleukins or hemoglobins, red cell concentrates or concentrates of other cellular blood compounds as granulocytes, platelets, lymphocytes etc.) as well as plasma derivatives (e.g. plasma cryopoor plasma, coagulation factors, cryoprecipitate (e.g. factor VIII, IX, X, XIII etc.), immunoglobulines, the inhibitors .alpha..sub.1 antitrypsin, antithrombin III etc.).

The sterilizing agent, i.e. the vitamin, can remain in the biological material to be virus inactivated but it also may easily be removed from the sterilized preparation by means of washing gelfiltration, adsorption or ultrafiltration.

In the examples below, Sendai viruses were used to demonstrate virus inactivation in accordance with the discovery. Sendai viruses have been proved to be very effective in experiments as model viruses for the human pathogenic lipid viruses HBV, HNANBV and HIV. Moreover Herpes virus HSV-I has been used.

100 ml human plasma were mixed with 0.2% vitamin C after the plasma had been contaminated with Sendai virus. The mixture was incubated for four hours at 23.degree. C. and pH 7.15.

A reference sample which was also contaminated with Sendai virus was incubated under the same conditions but without addition of the vitamin. The samples were frozen immediately after incubation at -80.degree. C. The infectious titers of Sendai virus were determined on incubated eggs. In the reference sample, a titer of 10.sup.2.7 infectious units/ml was found. In the sample with vitamin C, infectious virus was no longer demonstrated, corresponding to an inactivation of .gtoreq.2.7 log.sub.10.

Human erythrocytes, washed three times with 0.9% sodium chloride, were spiked with Sendai virus (dilution 1:100). 0.25% vitamin E-acetate was added to one aliquot of the virus spiked erythrocytes and the mixture incubated at 37.degree. C. for 3 hours. The second virus spiked aliquot was incubated without vitamin addition. In all the following examples, the control sample was treated identically. Infectious Sendai virus was titrated in embryonated eggs and antigen determined by haemagglutination assay.

In the vitamin E-acetate treated sample no infectious Sendai virus was detectable, whereas in the untreated sample 5.times.10.sup.4 Sendai/ml were found, corresponding to a reduction of virus titer of >4.7 log.sub.10 (Table I).

Human, erythrocytes, washed three times, were spiked with Herpes virus (HSV-I) and treated as described in Example 2, using vitamin E acetate, supplemented with Tween 80 (0.075%/0.01%) for better solubility.

Herpes virus was titrated on cell culture (Rita-cells) by plaque counting. The results are given in Table II. Tween 80 alone shows almost no virus inactivation activity. Even concentrations ten times higher than those used in the combination with vitamin E are ineffective.

Human plasma was spiked with Sendai virus (dilution 1:50) and one aliquot of the spiked plasma was incubated in the presence of 0.2% vitamin A acetate at 23.degree. C. for three hours. Virus titration was performed as described in Example 1. Treatment with vitamin A acetate resulted in a titer reduction of Sendai virus of >2.7 log.sub.10 (Table III).

Human plasma was spiked with Sendai virus as described in Example 4 and treated with vitamin A acetate (0.5%) supplemented with Tween 80 (0.15%).

Due to this treatment inactivation of Sendai virus of 2.0 log.sub.10 was achieved (Table III).

Human plasma was spiked with Sendai virus and treated with vitamin B.sub.6 (0.2%). Incubation was performed at 23.degree. C. for three hours. Titration of Sendai virus was performed as described above. Titer of infectious Sendai virus was reduced by treatment with vitamin B.sub.6 by >2.7 log.sub.10 (Table IV). Treatment with 0.1% vitamin B.sub.6 resulted in an inactivation of 1.0 log.sub.10.

Human plasma was spiked with Sendai virus and treated with vitamin B.sub.12 (0.2%). The inactivation of Sendai virus achieved by treatment with vitamin B.sub.12 was >2.7 log.sub.10 (Table IV).

Human erythrocytes, washed as described, were spiked with Herpes virus (HSV-I) and treated with vitamin A acetate (0.2%) plus Tween 80 (0.075%). The reduction of infectious HSV-I titer by this treatment was 2.0 log.sub.10 (Table V).

Human erythrocytes were spiked with Herpes virus (HSV-I) and treated with vitamin B.sub.12. The titer of infectious HSV-I was reduced by treatment with vitamin B.sub.12 by 1.0 log.sub.10 (Table V).

It will be understood that the specification and examples are illustrative but not limitative of the present invention and that other embodiments within the spirit and scope of the invention will suggest themselves to those skilled in the art.