Process for the inactivation of viruses with the aid of acridine derivatives

Abstract

The invention relates to the use of acridine or acridine derivatives, preferably in combination with benzalkonium chloride, for the inactivation of enveloped or nonenveloped viruses. The process according to the invention is preferably carried out in the presence of proteins whose biological activity is substantially retained.

Description

FIELD OF THE INVENTION

The invention relates to the use of acridine or acridine derivatives, preferably in combination with benzalkonium chloride, for the inactivation of enveloped or nonenveloped viruses. The process according to the invention is preferably carried out in the presence of proteins whose biological activity is largely retained.

BACKGROUND OF THE INVENTION

It has been known for years that untreated human plasma or serum can contain human pathogenic viruses, such as HIV, HBV or HCV, which, if transmitted to sensitive recipients, can cause serious diseases, such as AIDS or hepatitis. In order to prevent this potential virus transmission, therapeutics which are obtained from human plasma or serum are prepared, on the one hand, only from preselected starting materials which, as far as anyone can judge, are virus-free and, on the other hand, are subjected to virus-inactivating/eliminating steps in the preparation process. The efficiency of the virus inactivation/elimination method used is established using strict measures and continuously checked.

Besides physical virus inactivation steps, chemical virus inactivation steps are also known in the preparation of said therapeutics. A particularly frequently discussed chemical process is the SD (solvent/detergent) method. It is suitable for inactivating enveloped viruses, i.e. viruses which are surrounded by a lipid-containing membrane, but has the crucial disadvantage of being completely ineffective against all known nonenveloped (uncoated) viruses. Moreover, also no other chemical process is known which would be suitable to inactivate nonenveloped viruses while simultaneously retaining the biological activity of the protein constituents of the therapeutic or of the human plasma or serum.

Although the chemical virus inactivation processes are only used in a supplementary capacity to the physical methods, and although most viruses potentially transmissible by blood and blood products carry a lipid coat, for reasons of safety there is an exceptional need to make available chemical inactivation processes which also reliably inactivate nonenveloped viruses. This is all the more desirable as recently also HAV and parvoviruses, for example parvovirus B 19, were discussed as viruses which are potentially transmissible by blood fluids or blood products. (Vox Sanguinis 67, Supplement 1, 1994: Proceedings of a Symposium held at the New York Blood Center).

The invention was also based on the object of developing an industrially utilizable process for chemical virus inactivation, in which enveloped and nonenveloped viruses, e.g. parvo viruses, are inactivated with retention of the biological activity of proteins present, e.g. therapeutically useful proteins.

SUMMARY OF THE INVENTION

This object is achieved according to the invention by adding acridine or an acridine derivatives to the protein-containing liquid to be treated. It was surprisingly found that acridine or acridine derivatives inactivate enveloped and nonenveloped viruses. Acridine derivatives are, for example, ethacridine, 9-aminoacridine (=amina-crine), 3,6-acridinediamine (proflavine), acrisorcin, Acrizane chloride (=phenacridane chloride), Acridine Orange, quinacrine, acricide, acridone, acridine-9-carboxylic acid, acranil (1-[(6-chloro-2-methoxy-9-acridinyl)amino]-3-(diethylamino)-2-propanol dihydro-chloride), 3,7-diamino-5-phenylphenazinium chloride (phenosafranin, Safranin B Extra), phenoxazine, phenothiazine and especially acriflavine (3,6-diamino-10-methylacridinium, chloride and 3,6-acridineidiamine) and their salts, e.g. chlorides, sulfates, bromides.

Surprisingly, it was additionally found that a combination of acridine or an acridine derivative and benzalkonium chloride displays a synergistic action during virus inactivation, i.e. the magnitude of the virus inactivation of the combination is higher than that of each individual substance.

The virus inactivation process according to the invention can be carried out with protein solutions such as blood, serum, plasma, blood products, allantoic fluid or milk. The virus inactivation is carried out at a pH of 3 to 10 or 5 to 9 (in, for example, serum or plasma solutions) and a temperature of 1° C. to 80° C., preferably of 20° C. to 60° C., very preferably from 20° C. to 40° C. or 25° C. to 37° C., and lasts 30 minutes to 10 hours, preferably 2 to 5 hours. For virus inactivation, a concentration of 1.0 g/l-0.00001 g/l or 1.0 g/l-0.004 g/l, preferably 0.1 g/l-0.001 g/l, is used for the acridines or acridine derivatives, and a concentration of 0.1 g/l-0.004 g/l, preferably 0.05 g/l-0.01 g/l, for benzalkonium chloride.

The removal of the acridines and of the benzalkonium chloride from the protein solutions, if this is necessary, is possible by means of simple, known methods, such as adsorption on active carbon or dialysis.

A further advantage of the virus inactivation process according to the invention is the very extensive protection of the protein constituents of the material to be treated: different biological activities, e.g. antibody activity and clotting-activity, are not reduced or only reduced to a tolerable extent.

The virus inactivation process according to the invention can therefore be employed, for example, for the decontamination of the following materials:

protein-containing solutions (dilute or concentrated)

blood or blood products; both the liquid and the cellular constituents

serum, plasma

allantoic fluid

organ extracts

milk

buffer solutions

antigens for diagnostics

vaccines, antigens for vaccines

The process according to the invention is furthermore suitable for disinfection in virus contamination of, for example, areas, equipment, effluents, wastes and surfaces of all types. The disinfection of virus-contaminated organ transplants, e.g. cornea, cerebral meninges, liver, heart, lungs or kidneys is also possible.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is furthermore illustrated by the following examples.

Methods generally used in the process according to the invention

Virus: Was replicated in a known manner in tissue cultures; the virus harvests were centrifuged and used as starting material for the further investigations.

The infectiousness titer was determined in microtiter plates—8 replicates of 0.1 ml/-dilution stage—by double titration.

	Stock	Ethacridine	3% strength
	solutions:	lactate (EL)	in dist. water)
		Entozon ® (E)	3% strength Acridines
			in dist. water}
		Acriflavine (A)	1% strength
			in dist. water)
		Benzalkonium	10% in dist.
		chloride (BACI)	water

General experimental procedure:

9 parts of buffer or medium or protein solutions were mixed with 1 part of virus. The addition of the amounts of the stock solutions indicated in the individual examples for virus inactivation and renewed mixing with subsequent virus titration were then carried out. After the times and temperatures mentioned in the individual examples, samples were removed and titrated in double determinations in order to be able to measure the process-related virus inactivation.

Types of virus investigated

Abbreviation                     Name
PI                                                                        3                                                                    V Bovine parainfluenza 3 virus
BPV                              Bovine parvovirus
PPV                              Porcine parvovirus
IBRV                             Infectious bovine rhinotracheitis
                                 virus
BVDV                             Bovine viral diarrhoea virus
CPV                              Canine parvovirus
BAV-1                            Bovine adenovirus type 1
Reo 3                            Reovirus type 3
Influenza A                      Influenza A virus-Shangdong
Influenza B                      Influenza B virus - B Panama

Further abbreviations/names used in the text:

EME Medium    Eagles Minimum Essential Medium
Beriate ® P   Clotting factor VIII:C concentrate,
              Pasteurized (Behringwerke AG, Marburg,
              Germany)
Haemate ® P   Concentrate from clotting factor VIII
              and Von-Willebrand factor, pasteurized
              (Behringwerke AG, Marburg, Germany)
Beriplex ® P  pasteurized prothrombin complex con-
              centrate (Behringwerke AG, Marburg,
              Germany)
Venimmun ®    Human polyvalent immunoglobulin
              preparation (7S) for intravenous use
              (Behringwerke AG, Marburg, Germany)
Entozon ®     Preparation of the following composi-
              tion:
              1 g of granules contains 0.059 g of
              dimethoxy-6-nitro-9-[(3-diethylamino-
              2-hydroxy)propylamino]acridine dihy-
              drochloride and 0.295 g of ethacridine
              lactate (ASID Veterinär Vertriebs
              GmbH)
QAE cellulose Diethyle-2-hydroxypropylaminoethyl
              cellulose
              (Ion exchanger for protein purifica-
              tion)
FCS           Fetal calf serum

Example 1

Inactivation of PI 3 V by BACI

EME medium was mixed with PI 3 virus and BACI and incubated at 37° C. in a water bath. After the times indicated, samples were taken to test for virus inactivation. The results are shown in Tab. 1.

TABLE 1
Inactivation of PI 3 virus with BACI at 37° C.
	BACI	Virus titer	Virus inactiva-
	addition	found	tion
Time (h)	(mg/ml)	(log 10 /ml)	(log 10 /ml)
0-0.03 1)	0 (control)	7.4	—
	0.1	≦1.5	≧5.9
	0.005	≦1.5	≧5.9
	0.025	6.0	1.4
	0.0125	6.9	0.5
1	0 (control)	6.8	—
	0.1	≦1.5	≧5.3
	0.05	≦1.5	≧5.3
	0.025	≦1.5	≧5.3
	0.0125	5.5	1.3
1) Identical after addition of BACI and thorough mixing of the reaction batch

As emerges from the results in Table 1, PI 3 virus is very rapidly inactivated by the high doses of BACI (0.1 mg/ml, 0.05 mg/ml), i.e. in the time which was needed to mix the virus-containing sample thoroughly with BACI, to take a sample and to titrate this in order to determine the infectiousness of PI 3 virus, infectious virus was no longer detectable. At the two other BACI concentrations tested (0.025 mg/ml and 0.0125 mg/ml), a clear concentration-time dependence of virus inactivation is discernible.

Example 2

Virus Inactivation by Means of BACI or Entozon

The virus species shown in Tab. 2 were treated with BACI or Entozon and incubated at 45° C. Sample taking for virus titration was-carried out 1 or 2 hours after the start of the test.

TABLE 2
Virus inactivation by means of BACI or Entozon at 45° C.
		Substance	Virus titer	Virus inacti-
		Addition	found	vation
Virus	Time	(mg/ml)	(log 10 /ml)	(log 10 /ml)
BPV	1 hour	Control	0	4.7	0
		BACI	0.05	5.2	0
		BACI	0.01	5.2	0
	2 hours	Control	0	4.6	0
		BACI	0.05	4.6	0
		BACI	0.01	4.6	0
	1 hour	Control	0	4.7	0
		Entozon	0.030	≦1.5	≧3.2
		Entozon	0.015	≦1.5	≧3.2
	2 hours	Control	0	4.6	0
		Entozon	0.030	≦1.5	≧3.1
		Entozon	0.015	≦1.5	≧3.1
PPV	1 hour	Control	0	5.6	0
		Entozon	0.030	3.3	2.3
		Entozon	0.015	3.7	1.9
	2 hours	Control	0	5.6	0
		Entozon	0.030	2.2	3.4
		Entozon	0.015	2.7	2.9

As the results in Table 2 show, BPV is not inactivated by BACI under the test conditions selected. Inactivation is possible by means of Entozon, inactivation with BPV taking place substantially more rapidly than with PPV.

Example 3

Virus Inactivation by Means of BACI and Acriflavine

The suspensions of the virus species shown in Tab. 3 were treated with BACI or acriflavine and incubated at 37° C. for 2 hours. Samples were then taken for titration to determine the virus inactivation.

	TABLE 3
			Virus titer	Virus inacti-
		Substance addition	found	vation
	Virus	(mg/ml)	(log 10 /ml)	(log 10 /ml)
	IBRV	Control	0	5.1	0
		BACI	0.01	≦1.5	≧3.6
		Acriflavine	0.001	1.8	3.3
	PI 3 V	Control	0	5.6	0
		BACI	0.01	≦1.5	≧4.1
		Acriflavine	0.001	3.2	2.4
	BVDV	Control	0	6.2	0
		BACI	0.01	2.3	3.9
		Acriflavine	0.001	2.5	3.7
	BPV	Control	0	5.4	0
		BACI	0.01	5.9	0
		Acriflavine	0.001	≦1.5	≧3.9

As the results in Table 3 show, the enveloped virus species—IBRV, PI 3 V, BVDV—are inactivated both by BACI and acriflavine, the inactivation by BACI being somewhat greater. The naked virus BPV is inactivated by acriflavine, but not by BACI alone.

After virus inactivation by means of acriflavine and BACI was detected in EME medium, it was checked whether these substances can also inactivate virus in protein-containing solutions. The following protein solutions were treated with the virus species indicated:

Beriplex ®          PPV
Horse serum         BVDV, BPV
Beriate ®           BVDV, BPV, BAV-1, Reo 3, IBRV
Haemate ®           PPV, Reo 3
Venimmun ®          BVDV, PPV, CPV
FCS                 CPV
Egg allantoic fluid Influenza A, Influenza B

The results obtained in these experiments are shown in tabular form below.

Example 4

Virus Inactivation with Acridines and Benzalkonium Chloride in Protein Solutions

As emerges from the results in Table 4, it is possible to inactivate completely different viruses in a methodologically simple manner in protein solutions using acridines and/or benzalkonium chloride. It appears clear here, however, that by means of benzalkonium chloride alone only envelope-containing viruses can be, inactivated, whereas by means of acridines both envelope-containing and also nonenveloped virus species are inactivated. Both substances act synergistically in their virucidal action, i.e. the magnitude of the, virus inactivation with the combination acriflavine+benzalkonium chloride is higher than with the two individual substances.

The results in Table 4 also show that virus inactivation in protein solutions is dependent on:

1. the virus species to be inactivated

2. the constituents and nature of the protein solution

3. the inactivating agent concentration

4. the inactivation time

5. the inactivation temperature.

The virus inactivation is also pH-dependent—results not shown. At a pH of below 5.5, virus inactivation takes place more slowly than at higher pHs.

Tables 5-7 contain the results of the biological activity of the protein solutions after virus inactivation by means of acriflavine and/or benzalkonium chloride. The biological activity was determined in Venimmun® by the content of antibodies before and after virus inactivation, and in Haemate®; Beriate® and Beriplex® by the determination of the clotting-promoting activity—measured in international units.

TABLE 4
Virus inactivation with acridines and benzalkonium chloride in protein solutions
Protein		Concentra-	Inactivation	Inactiva-	Control	Treatment	Titer re-
solution and	Inactiva-	tion	Temperature	tion time	titer	titer	duction
virus	ting agent	(mg/ml)	(° C.)	(h)	(log 10 /ml)	(log 10 /ml)	(log 10 /ml)
Horse serum +	Acriflavine	0.001	37	0	5.4	5.4	0
BPV				1	5.2	≦1.5	≧3.7
				2	5.1	≦1.5	≧3.6
Horse serum +	Acriflavine	0.001	37	0	5.0	5.0	0
BVDV				1	5.1	≦1.5	≧3.6
				2	5.0	≦1.5	≧3.5
Beriate + BPV	Acriflavine	0.001	37	0	5.4	5.4	0
				1	5.0	≦1.5	≧3.5
				2	5.0	≦1.5	≧3.5
Beriate +	Acriflavine	0.001	37	0	5.0	5.0	0
BVDV				1	5.0	≦1.5	≧3.5
				2	4.8	≦1.5	≧3.5
Beriate +	Ethacridine	0.3	45	0	5.4	5.1	0.3
Reo 3	lactate			1	4.7	≦1.5	≧3.2
				2	4.7	≦1.5	≧3.2
Beriate + IBR	Ethacridine	0.3	45	0	6.5	6.5	0
	lactate			1	5.7	2.0	3.7
				2	4.3	≦1.5	≧2.8
Haemate + PPV	Acriflavine	0.001	37	0	5.4	5.5	0
				1	5.5	3.3	2.2
				2	5.5	1.9	3.6
				3	5.3	≦1.5	≧3.8
Venimmun +	Acriflavine	0.001	37	0	4.0	4.0	0
PPV				1	3.9	≦1.5	≧2.4
				2	3.9	≦1.5	≧2.4
Venimmun +	Acriflavine	0.001	37	0	6.9	6.6	0.5
CPV				1	6.8	4.8	2.0
				2	6.8	3.9	2.9
				3	6.9	3.9	3.0
Venimmun +	Acriflavine	0.001	37	0	6.4	6.4	0
BVDV				1	5.8	4.5	1.3
				2	6.3	1.9	4.4
				3	6.0	0	≧6.0
Egg allantoic	Acriflavine	0.001	37	0	7.4	7.4	0
fluid +				1	7.1	6.4	0.7
Influenza				2	6.9	5.0	1.9
virus B
Egg allantoic	BACI	0.02	37	0	7.4	7.4	0
fluid +				1	7.1	6.0	1.1
Influenza				2	6.9	3.6	3.3
virus B
Egg allantoic	Acriflavine +	0.001	37	0	7.4	7.4	0
fluid +	BACI	0.02		1	7.1	4.1	3.0
Influenza				2	6.9	2.5	4.4
virus B
Beriplex +	Acriflavine	0.001	30	0	4.8	4.8	0
PPV				1	4.6	3.6	1.0
				2	4.6	2.9	1.7
				3	4.8	≦1.5	≧3.3
Beriplex +	BACI	0.001	30	0	4.8	4.8	0
PPV				1	4.8	4.8	0
				2	4.6	4.8	0
				3	4.6	4.6	0
Beriate + PPV	Acriflavine +	0.001	30	0	4.8	4.8	0
	BACI	0.01		1	4.8	3.5	1.3
				2	4.6	≦1.5	≧3.1
				3	4.6	≦1.5	≧3.1
Beriplex +	Acriflavine	0.001	37	0	4.8	4.8	0
PPV				1	4.6	2.0	2.6
				2	4.6	≦1.5	≧3.1
				3	4.8	≦1.5	≧3.3
Beriplex +	BACI	0.01	37	0	4.8	4.8	0
PPV				1	4.6	4.6	0
				2	4.6	4.6	0
				3	4.8	4.6	0.2
Beriplex +	Acriflavine +	0.001	37	0	4.8	4.8	0
PPV	BACI	0.01		1	4.6	1.8	2.8
				2	4.6	≦1.5	≧3.1
				3	4.8	≦1.5	≧3.3
FCS + CPV	Acriflavine	0.001	37	0	6.6	6.6	0
				1	n.d.	4.9	1.7
				2	n.d.	4.0	2.6
				3	6.9	3.4	3.5
FCS + CPV	Acriflavine	0.001	45	0	6.8	6.8	0
				1	n.d.	4.8	2.0
				2	n.d.	3.5	3.3
				3	7.0	2.8	4.2

TABLE 5
Determination of the biological activity (antibody titer)
in protein solutions before and after virus inactivation
by means of acriflavine and benzalkonium chloride
		Reciprocal neutra-
		lization titer 1
		against polio virus
	Tempera-	Type 1
			ture and	Without	With
			duration	inacti-	inacti-
	Protein		of the	vating	vating
	solution	Name	treatment	agent	agent 2
	Low-cryo	H1	37° C.	646	646
	human plasma	H2	2 hours	741	562
	(invididual	H3		741	646
	plasma)	H4		646	741
		H5		376	562
	Venimmun ®	V1	37° C.	2234	851
	(Final	V2	2 hours	1950	1698
	product)	V3		1698	1698
	various	V4		1698	1698
	batches	V5		1479	1479
	Low-cryo	H1	45° C.	427	977
	human plasma	H2	2 hours	1288	977
	(individual	H3		1288	977
	plasma)	H4		977	1122
		H5		977	1288
	Venimmun ®	V1	45° C.	1950	2234
	(Final	V2	2 hours	2570	2234
	product)	V3		2234	1479
	various	V4		2234	1950
	batches	V5		2234	1479
	1 Titer calculation according to Spearman-Karber from log 2 dilution series using 8 replicates/dilution stage
	2 Acriflavine 0.001 mg/ml + BACI 0.02 mg/ml

TABLE 6
Determination of the biological activity (antibody titer
in protein solutions before and after virus inactivation
by means of acriflavine and benzalkonium chloride
		Temperature	Rec. HAH anti-PI 3	Rec. HAH anti-reo3
		and duration	virus	virus
Protein		of the	Antibody titer 1	Antibody titer 1
solution	Name	treatment	Without I. 2	With I. 2	Without I. 2	With I. 2
Low-cryo	H1	45° C.	80	80	320	320
human	H2	2 hours	80	80	320	320
plasma	H3		80	80	320	320
(indivi-	H4		80	80	320	320
dual	H5		80	80	320	320
plasma)
Venimmun ®	V1	45° C.	320	320	320	320
(Final	V2	2 hours	320	320	320	320
product)	V3		320	320	320	320
various	V4		320	320	320	320
batches	V5		320	320	320	320
Horsye se-	P1	45° C.	n.d.	n.d.	640	640
rum (indi-	P2	2 hours			640	640
vidual	P3				640	640
sera)	P4				640	640
	P5				640	640
1 Titer determination in log 2 dilution series
2 I. = inactivating agents: acriflavine 0.001 mg/ml + BACI 0.02 mg/ml

TABLE 7
Determination of the biological activity (clotting
activity) of protein solutions before and after virus
inactivation by means of acriflavine (A) and benzalkonium
chloride (BACL)
				Inacti-
		Tempera-		vating
		ture and		agent
		duration	Inacti-	concen-
	Protein	of the	vating	tration	Activity
	solution	treatment	agent	(mg/ml)	(IU/ml)
	cryo-	3 hours	A	0.01	3.9
	protein	45° C.	A	0.03	4.2
	solution		A	0.001	4.4
	after		BACI	0.1	6.9
	Al(OH) 3 +		BACI	0.05	6.1
	QAE		A + BACI	0.001 +	4.1
	treatment			0.05
			Control	0	5.3
	Haemate ®	3 hours	A	0.002	18.9
	Factor	37° C.	A	0.001	16.8
	VIII		BACI	0.02	20.7
			A + BACI	0.001 +	17.6
				0.02
			Control	0	24.1
	Beriplex ®	3 hours	A	0.002	48.8
	Factor II	37° C.	A	0.001	50.0
			BACI	0.02	61.3
			A + BACI	0.001 +	47.9
				0.02
			Control	0	68.6

As emerges from the results in Tables 5 and 6, the content of neutralizing (Polio Type 1) and hemagglutination-inhibiting (HAH) antibodies (PI 3 —and Reo 3 virus) in Venimmun® is not affected to an extent-exceeding the test variations (as a rule ±1 log 2 stage) during virus inactivation by means of acridines and benzalkonium chloride. The activity decrease with the clotting preparations (Beriate®, Haemate®, Beriplex®) after acridines/benzalkonium chloride, inactivation is tolerable (Table 7).

Claims

1. A process for inactivating viruses, comprising:(a) forming a composition by adding acridine or an acridine derivative to a material suspected to contain viruses, wherein the acridine or acridine derivative is present at non-cytotoxic concentrations; and (b) incubating the composition of step (a) in vitro; wherein the acridine derivative is selected from the group consisting of ethacridine, 9-aminoacridine, 3,6 acridinediamine, acrisorcin acrizane, acridine orange, quinacrine, acricide, acridone, acridine-9-carboxylic acid, acranil, phenosafranin, phenoxazine, phenothiazine, acriflavine, and salts thereof.

2. The process as claimed in claim 1, wherein the material further comprises at least one protein, wherein the protein retains its biological activity.

3. The process as claimed in claim 1, wherein said process is performed at a temperature of 20-60° C.

4. The process as claimed in claim 1, wherein said process is performed at a temperature of 25-37° C.

5. The process as claimed claim 1, wherein said process is performed at pH 5-9.

6. The process as claimed in claim 1, wherein said acridine or acridine derivative is present at a concentration of 0.0001 to 1.0 g/l.

7. The process as claimed in claim 6, wherein said acridine or acridine derivative is present at a concentration of 0.0005 to 0.1 g/l.

8. The process as claimed in claim 1, wherein said process is performed for 0.5 to 10 hours.

9. The process as claimed in claim 8, wherein said process is performed for 2 to 5 hours.

10. The process as claimed in claim 1, wherein the viruses are nonenveloped viruses.

11. The process as claimed in claim 1, wherein the viruses are enveloped viruses.

12. A process for inactivating viruses, comprising:(a) forming a composition by adding benzalkonium chloride and acridine or an acridine derivative to a material suspected to contain viruses, wherein the benzalkonium chloride is present at a concentration up to 0.1 g/l and the acridine or acridine derivative is present at non-cytotoxic concentrations; and (b) incubating the composition of step (a) in vitro, wherein the material further comprises at least one protein that retains its biological activity.

13. The process as claimed in claim 12, wherein said process is performed at a temperature of 20-60° C.

14. The process as claimed in claim 12, wherein said process is performed at a of 25-37° C.

15. The process as claimed in claim 12, wherein said process is performed at pH 5-9.

16. The process as claimed in claim 12, wherein said acridine or acridine derivative is present at a concentration of 0.0001 to 1.0 g/l.

17. The process as claimed in claim 16, wherein said acridine or acridine derivative is present at a concentration of 0.0005 to 0.1 g/l.

18. The process as claimed in claim 12, wherein said benzalkonium chloride is present at a concentration of 0.004 to 0.1 g/l.

19. The process as claimed in claim 18, wherein said benzalkonium chloride is present at a concentration of 0.01 to 0.05 g/l.

20. The process as claimed in claim 12, wherein said process is performed for 0.5 to 10 hours.

21. The process as claimed in claim 20, wherein said process is performed for 2 to 5 hours.

22. The process as claimed in claim 12, wherein the viruses are nonenveloped viruses.

23. The process as claimed in claim 12, wherein the viruses are enveloped viruses.