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  • C12N2770/24011—Flaviviridae
  • C12N2770/24311—Pestivirus, e.g. bovine viral diarrhea virus
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  • C12N2770/24361—Methods of inactivation or attenuation

Definitions

• the invention belongs to the field of animal health and in particular Bovine Viral Diarrhea Virus (BVDV).
• BVDV Bovine Viral Diarrhea Virus
• the invention provides infectious BVDV clones and methods to produce said BVDV clones.
• the invention further relates to methods of attenuating said clones, attenuated BVDV clones and vaccines comprising said attenuated clones.
• Bovine Viral Diarrhea Virus is the causative agent of BVD and mucosal disease in cattle (Baker, 1987; oennig and Plagemann, 1992; Thiel et al., 1996). Fetal infection during pregnancy can result in the resorption of the fetus, abortions as well as birth of immunotolerant calves which are persistently infected with BVDV. These calves lack or have very low neutralizing antibody titers and are continuously shedding high amounts of virus. Next to acutely infected cattle these calves are the major source for virus spreading and are therefore of prime importance in the epidemiology of this disease. The major economical impact of BVD results from high abortion rates, stillbirths, fetal. resorption, mummification, congenital malformations, and birth of weak and undersized calves. For a detailed review of the pathogenesis it is hereby referred to the article of Moennig and Liess of 1995.
• BVDV Two major antigenic groups of BVDV (type 1 and 2) have been described (Becher et al. 1999) which display limited cross neutralizing antibody reactions (Ridpath et al. 1994).
• Vaccines against the classical BVDV type 1 provide only partial protection from type 2 infection, and vaccinated dams may produce calves that are persistently infected with virulent BVDV type 2 (Bolin et al., 1991 , Ridpath et al., 1994).
• Killed vaccines inactivated whole virus
• subunit vaccines conventional purified or heterologously expressed purified viral proteins
• Live BVDV vaccines although attenuated, are most often associated with safety problems. As mentioned above, they cross the placenta of pregnant cows and lead to clinical manifestations in the fetus and/or the induction of persistently infected calves.
• Pregnant cows have to be kept separate from vaccinated cattle to protect fetuses and must not be vaccinated themselves. Furthermore, revertants of attenuated live BVDV pose a serious threat to cattle. For conventionally derived attenuated viruses wherein the attenuation is achieved by conventional multiple passaging, the molecular origin as well as the genetic stability of the attenuation remains unknown and reversion to the virulent wild-type is unpredictable.
• Live vaccines with defined mutations as a basis for attenuation would overcome the disadvantages of the present generation of attenuated vaccines.
• a further advantage of said attenuating mutations lies in their defined molecular uniqueness which can be used as a distinctive label for the attenuated pestivirus to distinguish it from pestiviruses from the field.
• BVDV of defined genetic identity which closely resemble wild-type viruses are hardly known, in particular not for type 2 BVDV.
• the technical problem underlying this invention was to provide a BVDV, in particular a BVDV type 2, of defined genetic identity.
• FIG. 1 Construction of the infectious cDNA clone.
• the upper part scetches a BVDV genome (kB) and the encoded polyprotein.
• the middle part shows the cDNA clones s (white), the RT-PCR product (light grey) and the PCR products (dark grey) used for engineering the infectious cDNA clone, and the lower part depicts the ends of the genomic cDNA sequences (underlined) and the sequences added at the 5' and 3' ends for in vitro transcription.
• Fig. 2 Growth curves of the recombinant virus XIKE-A and the wild type BVDV isolate VLS#399.
• MDBK cells were infected with the viruses at an m.o.i of 0.1 and harvested by freezing and thawing at the indicated time points. Titers were determined after infection of new MDBK cells by immunofluorescence staining 72h p.i.
• s Fig. 3 Growth curves of the recombinant virus XIKE-A and the E r ⁇ s mutants XIKE-B (H349 ⁇ ) and XIKE-C (H300L).
• MDBK cells were infected with the viruses at an m.o.i of 0.1 and harvested by freezing and thawing at the indicated time points. Titers were determined after infection of new MDBK cells by immunofluorescence staining 72h p.i.
• Fig. 4 Determination of RNAse activity of the recombinant viruses XIKE-A (wild type
• the enzymatic degradation of poly(U) was determined by measu ⁇ ng the OD 60 as s a marker of the release of small RNA fragments into the supernatant.
• Fig. 5 Body temperatures of animals infected with New York '93/C (animal #275, #612 and #1610, broken lines) or XIKE-A (animal #615, #377 and #091 , solid lines).
• Fig. 6 White blood cell (WBC) counts of animals infected with New York '93/C (animals #275, #612 and #1610, broken lines) or XIKE-A (animals #615, #377 and #091 , solid lines).
• Fig. 7 Body temperatures of animals infected with XIKE-A (animal #387, #388 and
• Fig. 8 White blood cell l(WBC) counts of animals infected with XIKE-A (animals #387, #388 and #418, broken lines) or XIKE-B (animals #415, #417 and #419, solid lines).
• BVDV refers to all viruses belonging to species BVDV 1 and BVDV 2 in the genus pestivirus within the family Flaviviridae (Becher et al. 1999).
• the more classical BVDV type 1 strains and the more recently recognized BVDV type 2 strains display some limited but distinctive differences in nucleotide and amino acid sequences.
• a suspiciousclone is a DNA vector or host cell strain into which such vector has been introduced.
• the DNA vector is a plasmid.
• An ..infectious clone is a DNA Vector with the capability to serve as a template for s transcription into a RNA that induces the generation of the the virus when introduced into susceptible cells.
• the RNA is produced by in vitro transcription and introduced into the cells by transfection technologies known to the skilled person.
• Attenuated BVDV particles or “attenuated viral particles” as used herein relates to BVDV particles attenuated by a method according to the invention (see infra).
• a full-length RNA is a RNA comprising at least 98 % of the sequence of a RNA occurring in a wild-type isolate.
• a full-length complementary DNA is a DNA comprising o a sequence complementary to at least 98 % of a RNA occuring in a wild-type isolate.
• calf relates to a bovine animal of six months of age or less.
• Authentical virulence means that there is no statistically s significant difference between the virulence of infectious BVDV particles according to the invention and wild-type BVDV isolates from which said DNA molecules containing a nucleotide sequence complementary to a BVDV RNA, preferably a type 2 RNA have been derived, for at least one predominant clinical parameter. Examples for such predominant clinical parameters are diarrhea, pyrexia and/or lethality. 0
• Attenuation means that there is a statistically significant difference between the virulence of attenuated BVDV particles according to the invention, said attenuated BVDV particles being attenuated by a method according to the invention, and wild-type BVDV isolates from which said attenuated BVDV particles have been derived, for the predominant clinical parameters diarrhea, pyrexia and lethality in animals infected with the same dose, preferably
• said attenuated BVDV particles do not cause diarrhea, pyrexia and lethality and thus may be used in a vaccine.
• RACE as used herein means rapid amplification of cDNA ends and is known as such in the art (Frohman et al, Proc. Natl. Acad. Sci USA 1988, 85: 8998-9002).
• ..Susceptible cell as used herein is a cell which can be infected with BVD virus or transfected with BVDV RNA, wherein said virus or RNA, when introduced into said susceptible cells, induces the generation of infectious BVDV.
• a fragment" according to the invention is any subunit of a DNA molecule or infectious BVDV clone according to the invention, i.e. any subset, characterized in that it is encoded by a shorter nucleic acid molecule than disclosed which can still be transcribed into RNA.
• a ..functional variant" of the DNA molecule or infectious BVDV clone according to the invention is a DNA molecule or infectious BVDV clone which possesses a biological activity (either functional or structural) that is substantially similar to the DNA molecule or infectious BVDV clone according to the invention.
• the term ..functional variant” also includes locallya fragment", locallya functional variant", -variant based on the degenerative nucleic acid code" or ..chemical derivative".
• Such a ..functional variant” e.g. may carry one or several nucleic acid exchanges, deletions or insertions. Said exchanges, deletions or insertions may account for 10% of the entire sequence.
• Said functional variant at least partially retains its biological activity, e.g. function as an infectious clone or a vaccine strain, or even exhibits improved biological activity.
• a -variant based on the degenerative nature of the genetic code is a variant resulting from the fact that a certain amino acid may be encoded by several different nucleotide tripletts. Said variant at least partially retains its biological activity, or even exhibits improved biological activity.
• a -fusion molecule may be the DNA molecule or infectious BVDV clone according to the invention fused to e.g. a reporter such as a radiolabel, a chemical molecule such as a fluorescent label or any other molecule known in the art.
• a -chemical derivative is a DNA molecule or s infectious BVDV clone according to the invention chemically modified or containing additional chemical moieties not normally being part of the molecule. Such moieties may improve the molecule's solubility, absorption, biological half life etc.
• a molecule is ..substantially similar" to another molecule if both molecules have substantially similar nucleotide sequences or biological activity.
• two 0 molecules possess a similar activity they are considered variants as that term is used herein if the nucleotide sequence is not identical, and two molecules which have a similar nucleotide sequence are considered variants as that term is used herein even if their biological activity is not identical.
• vaccine refers to a pharmaceutical composition comprising at least one immunologically active component that induces an immunological response in an animal and possibly but not necessarily one or more additional components that enhance the immunological activity of said active component.
• a vaccine may additionally comprise further components typical to pharmaceutical 0 compostions.
• the immunologically active component of a vaccine may comprise complete virus particles in either their original form or as attenuated particles in a so called modified live vaccine (MLV) or particles inactivated by appropriate methods in a so called killed vaccine (KV).
• MMV modified live vaccine
• KV killed vaccine
• the immunologically active component of a vaccine may comprise appropriate elements of said organisms (subunit vaccines) s whereby these elements are generated either by destroying the whole particle or the growth cultures containing such particles and optionally subsequent purification steps yielding the desired structure(s), or by synthetic processes including an appropriate manipulation by use of a suitable system based on, for example, bacteria, insects, mammalian or other species plus optionally subsequent isolation and purification so procedures, or by induction of said synthetic processes in the animal needing a vaccine by direct incorporation of genetic material using suitable pharmaceutical compositions (polynucleotide vaccination).
• a vaccine may comprise one or simultaneously more than one of the elements described above.
• vaccine as understood herein is a vaccine for veterinary use comprising antigenic substances and is administered for the purpose of inducing a specific and active immunity against a disease provoked by BVDV.
• the BVDV clone according to the invention confers active immunity that may be transferred passively via maternal antibodies against the immunogens it contains and sometimes also against antigenically related organisms.
• adjuvants like e.g. aluminiumhydroxide, mineral or other oils or ancillary molecules added to the vaccine or generated by the body after the respective induction by such additional components, like but not restricted to interferons, interleukins or growth factors.
• a "pharmaceutical composition” essentially consists of one or more ingredients capable of modifying physiological e.g. immunological functions of the organism it is administered to, or of organisms living in or on the organism.
• the term includes, but is not restricted to antibiotics or antiparasitics, as well as other constituents commonly used to achieve certain other objectives like, but not limited to, processing traits, sterility, stability, feasibility to administer the composition via enteral or parenteral routes such as oral, intranasal, intravenous, intramuscular, subcutaneous, intradermal or other suitable route, tolerance after administration, controlled release properties.
• BVDV bovine viral diarrhea virus
• the inventors for the first time provided a method to generate infectious clones and infectious BVDV particles derived thereof of defined genetic identity which at the same time have the pathogenicity closely resembling the wild-type virus. Furthermore, the inventors for the first time disclosed an infectious type 2 clone and infectious type 2 BVDV particles derived thereof.
• the inventors also invented a method to generate attenuated BVDV particles with genetic identity which may be attenuated by modification at only one defined genetic marker site.
• the invention allows to generate a causal link between genome modification and attenuation, which is essential in order to understand the functional mechanism of the attenuation and therefore helpful to assess the quality in use as a vaccine.
• the invention relates to a DNA molecule containing a nucleotide sequence complementary to a BVDV RNA, wherein said RNA, when introduced into susceptible host cells, induces the generation of infectious BVDV particles a) with the capability to induce viraemia and leukopenia in calves for a period of at least one day and at least one of the following clinical symptoms of the group comprising diarrhea and/or pyrexia lasting at least one day when infected with a dose of 6x10 6 TCID 5 o- b) with authentical virulence as defined supra as compared to a wild-type BVDV isolate from which such DNA molecule has been derived; and/or c) which are, when BVDV naive calves are infected at a dose of 6x10 6 TCID 5 o with such particles, lethal for at least 30 % of such calves within a period of 21 days; and/or d) with a virulence of not less than 90
• Said dose of 6x10 6 TCID 50 of step a) is preferably administered as 2x10 6 i.m. (gluteal muscle), 2x10 6 intranaseally, and 2x10 6 subcutaneously (over scapula) to obtain a total dose of 6x10 6 .
• Said clinical symptoms of step a) preferably should be observed in at least two thirds of all infected animals.
• Said leukopenia of step a) preferably shall be at least a 35% reduction below baseline on at least two consecutive days, wherein "baseline” relates to the average values of all animals 10 days before infection. Diarrhea is a typical symptom of infection with BVDV.
• the pyrexia of step a) is at least 40 °C.
• the invention relates to an infectious BVDV clone, capable of serving as a template for transcription into an RNA, wherein said RNA, when introduced into susceptible host cells, induces the generation of infectious BVDV particles f) with the capability to induce viraemia and leukopenia in calves for a period of at least one day and at least one of the following clinical symptoms of the group comprising diarrhea and/or, pyrexia lasting at least one day when infected with a dose of 6x10 6 TCID 50 ; and/or g) with authentical virulence as compared to a wild-type BVDV isolate from which such DNA molecule has been derived; and/or h) which are, when BVDV naive calves aged from 3 to 6 months are infected at a dose of 6x10 6 TCID 5 o with such particles, lethal for at least 30 % of such calves within a period of 21 days after infection; and/or i) with a virulence
• Said dose of 6x10 6 TCID 5 o of step f) is preferably administered as 2x10 6 i.m. (gluteal muscle), 2x10 6 intranaseally, and 2x10 6 subcutaneously (over scapula) to obtain a total dose of 6x10 6 .
• Said clinical symptoms of step a) preferably should be observed in at least two thirds of all infected animals.
• Said leukopenia of step f) preferably shall be at least a 35% reduction below baseline on at least two consecutive days, wherein "baseline" relates to the average values of all animals 10 days before infection.
• Said infectious BVDV clone preferably is a type 1 or type 2 clone.
• the virus that serves as the origin for constructing such clone is preferably obtained directly from a field isolate or retransferred to animals and subsequently reisolated from the animal with the strongest clinical symptoms and subsequently passaged no more than twice in cell culture, preferably once or not at all.
• the example (example 1) exemplifies this.
• the example demonstrates the cDNA-cloning of virus NY93/C which is, after several cell culture passages, retransferred into a bovine animal, reisolated and used for RNA preparation and cDNA cloning after not more than two cell culture passages of the reisolated virus.
• Another important embodiment of the invention is a BVDV particle generated by transcription using the DNA molecule or the BVDV clone according to the invention, the transfection of suitable cells or cell lines with said RNA and the collection of the resulting BVDV particles produced by said cells.
• Yet another embodiment is a BVDV particle generated by cloning the DNA molecule or the BVDV clone according to the invention into the genome of a suitable DNA virus, such DNA viruses being known to the artisan, followed by infection of suitable cells resulting in generation of BVDV particles produced by said cells.
• the DNA or infectious clone according to the invention may be transfected into suitable cells which then produce the RNA as disclosed for classical swine fever virus (CSFV) by van Gennip et. al. (1999) for cells which stably express T7 Polymerase.
• the DNA or infectious clone according to the invention may be expressed under control of an eukaryotic promotor in eukaryotic cells leading to the generation of infectious BVDV particles being able to be secreted from the cell (as exemplified by V. Racaniello and D. Baltimore for poliovirus (1981)).
• a highly important embodiment of the invention is an infectious BVDV type 2 clone.
• said infectious BVDV type 2 clone capable of serving as a template for transcription into an RNA, wherein said RNA, when introduced into susceptible host cells, induces the generation of infectious BVDV particles k) with the capability to induce viraemia and leukopenia in calves for a period of at least 1 day and at least one of the following clinical symptoms of the group comprising diarrhea and/or pyrexia lasting at least one day when infected with a dose of 6x10 6 TCID 50 ; and/or I) with authentical virulence as compared to a wild-type BVDV isolate from which such DNA molecule has been derived; and/or m) which are, when BVDV naive calves aged from 3 to 6 months are infected at a dose of 6x10 6 TCID 5 o with such particles, lethal for at least 30 % of such calves within a period of 21 days after infection;
• the invention relates to a BVDV type 2 clone obtainable by a method characterized by the following steps: aaa) a wild-type BVDV type 2 strain is isolated; o bbb) said wild-type BVDV type 2 strain is passaged in cell-culture; ccc) said cell culture-passaged BVDV type 2 strain is used to infect bovine animals and a BVDV strain is re-isolated from the most severely infected animal; ddd) said re-isolated BVDV type 2 strain is passaged no more than twice, s preferably once, in cell culture; eee) said re-isolated BVDV type 2 strain is reverse-transcribed and cloned resulting in a full-length cDNA clone, preferably the 5' and 3' ends are cloned using the RACE-technology.
• Said infectious DNA clone may then be transcribed into RNA under appropriate conditions, said RNA is introduced into appropriate cells or cell lines and the resulting BVDV type 2 particle is collected.
• a preferred embodiment relates to an infectious virus
• BVDV type 2 clone according to the invention as characterized by the DNA sequence s of SEQ ID NO. 1 or a fragment, functional variant, variant based on the degenerative nucleic acid code, fusion molecule or a chemical derivative thereof.
• a non-limiting example is provided in example 1.
• the invention further relates to a BVDV type 2 particle generated by in vitro transcription of the BVDV clone according to the invention into RNA, the transfection of o suitable cells or cell lines with said RNA and the collection of the resulting BVDV particles produced by said cells.
• the DNA or infectious clone according to the invention may be transfected into suitable cells which then produce the RNA as disclosed for classical swine fever virus (CSFV) by van Gennip et. al. (1999) for cells which stably express T7 Polymerase.
• CSFV classical swine fever virus
• DNA or infectious clone according to the invention may be expressed under control of an eukaryotic promotor in eukaryotic cells leading to the generation of infectious BVDV particles being able to be secreted from the cell (as exemplified by V. Racaniello and D. Baltimore for poliovirus (1981)).
• DNA molecule containing a nucleotide sequence complementary to a full-length BVDV type 2 RNA.
• said DNA molecule is characterized by the sequence SEQ ID NO. 1.
• the invention further relates to a DNA molecule according to the invention as characterized by SEQ ID No. 1 or a fragment, functional variant, variant based on the degenerative nucleic acid code, fusion molecule or a chemical derivative thereof.
• a non-limiting example is provided in example 1.
• the invention relates to a DNA molecule according to the invention, consisting of the sequence as characterized by SEQ ID No. 1.
• the invention further relates to a RNA molecule complementary to the DNA molecule according to the invention as described supra, or to the BVDV clone according to the invention as described supra.
• the invention also relates to a RNA molecule obtainable by transcription of the DNA molecule according to the invention as described supra, or the BVDV clone according to the invention as described supra.
• Another important aspect of the invention is a method for the production of an infectious BVDV clone from a wild-type BVDV isolate, said infectious BVDV clone being complementary to a RNA having authentical virulence as compared to said wild-type isolate, comprising the steps of p) isolating viral particles from an infected animal; preferably passaging not more than twice on suitable cell culture cells; q) preparing RNA from the viral particles; r) generating full-length complementary DNA after reverse transcription of the RNA; wherein the reverse transcription includes a step at elevated temperatures sufficient to break or reduce secondary structures of the RNA, and the use of a thermostable enzyme for this step, said enzyme being active at these elevated temperatures; s) incorporating the complementary DNA (cDNA) into a plasmid vector or into a DNA virus capable of directing the transcription of BVDV cDNA into RNA upon infection of suitable cells.
• Said viral particles preferably are isolated during viremia (step k)).
• BVDV clone from a wild-type BVDV isolate, said infectious BVDV clone being complementary to a RNA having authentical virulence as compared to said wild-type isolate, comprising the steps of ppp) isolating RNA from cells of an infected animal during viraemia or optionally after killing of said animal from its organ(s); qqq) generating full-length complementary BVDV DNA which preferably is assembled from DNA fragments after reverse transcription of the RNA; wherein the reverse transcription includes a step at elevated temperatures sufficient to break or reduce secondary structures of the RNA, and the use of a thermostable enzyme for this step, said enzyme being active at these elevated temperatures; rrr) incorporating the complementary DNA (cDNA) into a plasmid vector or into a DNA virus capable of directing the transcription of BVDV cDNA into RNA upon infection of suitable cells.
• cDNA complementary DNA
• Suitable cells for cell culture are Madin-Darby bovine kidney (MDBK) cells, RD (bovine testicular) cells or bovine Turbinat (BT) cells. Further suitable cells are known to the person skilled in the art.
• MDBK Madin-Darby bovine kidney
• RD bovine testicular
• BT bovine Turbinat
• the infectious clone produced by the method according to the invention is a type 1 clone or preferably a type 2 clone.
• Another important aspect of the invention is a method for the production of an infectious BVDV clone from a wild-type BVDV isolate, said infectious BVDV clone being complementary to a RNA having a virulence of not less than 90 % of said wild-type isolate, comprising the steps of t) isolating viral particles from an infected animal; u) passaging not more than twice in suitable cell culture cells; preferably once or not at all; v) preparing RNA from the viral particles; w) generating full-length complementary DNA after reverse transcription of the RNA; wherein the reverse transcription includes a step at elevated temperatures sufficient to break or reduce secondary structures of the RNA, and the use of a thermostable enzyme for this step, said enzyme being active at these elevated temperatures; x) incorporating the complementary DNA (cDNA) into a plasmid vector or into a DNA virus capable of directing the transcription of BVDV cDNA into RNA upon infection of suitable cells.
• cDNA complementary DNA
• Said viral particles preferably are isolated during viremia (step t)).
• the full length complementary DNA (cDNA) of step x) preferably may be generated by assembling overlapping partial cDNA fragments (see also example 1 ).
• the invention relates to a method according to the invention, wherein the 5' end of the RNA is generated using RACE. Surprisingly, only by applying the RACE technology in conjunction with a thermostable polymerase it was possible to dissolve the secondary structure of the genome successfully.
• the invention relates to a method according to the invention, wherein RACE is carried out with a thermostable polymerase allowing reaction temperatures of at least 48°C, preferably 50-55°C, preferably also 56-60°C.
• the inventors also invented a method to generate attenuated BVDV particles with a defined genetic identity which preferably are attenuated at only one defined genetic marker site. This surprisingly allows the simple determination of revertants or the successful attenuation as only the presence of the genetic marker site needs to be determined by molecular biology methods known to the artisan.
• XIKE-B and XIKE-C of example 1 are non- limiting examples for such attenuated BVDV particles of defined sequence.
• Another important aspect of the invention is a method of BVD virus attenuation by introducing one or more mutations into the DNA molecule according to the invention as described supra or the infectious BVDV clone as described supra, wherein said mutation or mutations lead to or increase an attenuated phenotype of the recovered BVD virus.
• Yet another important aspect of the invention is a method of attenuation of a BVDV strain, comprising the steps of y) introducing one or more mutations into the DNA molecule according to the invention as described supra, or into the infectious BVDV clone according to the invention as described supra; z) introducing the mutated DNA into susceptible host cells wherein said DNA is transcribed into RNA or introducing an RNA transcribed from said DNA into said cells; and aa)collecting viral particles produced by these cells; wherein said mutation or mutations results in attenuation.
• a preferred aspect of the invention is a method of attenuation according to the invention as described supra, wherein the mutation or mutations is a nucleotide substitution, deletion, insertion, addition, or combination thereof.
• mutation means the replacement of a nucleotide by another (e.g. C for a T) a so-called “substitution” or any other mutation such as “deletion” or "insertion”.
• substitution means the removal of one or several nucleotides or amino acids.
• infectious BVDV clones are viruses of authentic virulence closely resembling wild-type viruses and at the same time having a defined genotype, said virus must be used as a positive control in animal experiments. Said infectious clones are excellent tools for generating specifically attenuated BVDV clones to be used for e.g. vaccination.
• the invention comprises BVDV clones wherein the
• RNase activity residing in glycoprotein E RNS is inactivated.
• said RNAse activity is inactivated by deletion and/or -other mutation such as substitution.
• said deletions and/or other mutations are located at the amino acids at position 295 to
• a more preferred aspect of the invention is a method of attenuation according to the invention, wherein the mutation or mutations is in the glycoprotein E rns and causes impaired or loss of function of the mutated protein.
• a more preferred aspect of the invention is a method of attenuation according to the invention, wherein the mutation consists of bb)deletion of all or part of the glycoprotein E r ⁇ s ; and/or cc) deletion or substitution of histidine at position 300 of SEQ ID NO. 1 ; and/or dd)deletion or substitution of histidine at position 349 of SEQ ID NO. 1.
• yet another important embodiment is a method for the attenuation of
• BVDV comprising the mutation of a BVDV clone according to the invention at histidine positions 300 and/or 349 wherein the coding triplett is deleted or substituted.
• Yet another important embodiment is a method for the attenuation of BVDV according to the invention, wherein the codon for histidine 300 is substituted by a codon for leucine.
• Yet another important embodiment is a method for the attenuation of BVDV according to the invention, wherein the codon for histidine 349 is deleted.
• Another important embodiment of the invention is an attenuated BVDV clone or BVDV strain obtainable by a method according to the invention.
• Another important embodiment of the invention is a vaccine comprising an attenuated BVDV clone or strain according to the invention, optionally in combination with a pharmaceutically acceptable carrier or excipient.
• a vaccine of the invention refers to a vaccine as defined above, wherein one immunologically active component is a live BVDV, wherein the RNase activity in its protein E RNS is inactivated.
• live vaccine refers to a vaccine comprising a particle capable of replication, in particular, a replication active viral component.
• a vaccine according to the invention comprises an attenuated BVD virus type 1 according to the invention combined with an attenuated BVD virus type 2 according to the invention or any other antigenetic group and a pharmaceutically acceptable carrier or excipient.
• Said vaccine may be administered as a combined vaccine.
• said attenuated BVD virus type 1 according to the invention may be administered first followed by an administration of an attenuated BVD virus type 2 according to the invention three to four weeks later.
• a vaccine according to the invention comprises an attenuated BVD virus type 1 according to the invention wherein the RNase activity in its protein E RNS is inactivated, combined with an attenuated BVD virus type 2 according to the invention wherein the RNase activity in its protein E RNS is inactivated, or any other antigenetic group wherein the RNase activity in its protein E RNS is inactivated, and a pharmaceutically acceptable carrier or excipient.
• Said vaccine may be administered as a combined vaccine.
• said attenuated BVD virus type 1 according to the invention as described supra may be administered first followed by an administration of an attenuated BVD virus type 2 according to the invention as described supra three to four weeks later.
• the invention preferably relates to a method of treating a BVDV-infected bovine animal with an attenuated BVDV according to the invention as described supra, wherein the said attenuated BVDV or the vaccine composition as disclosed supra is administered to the bovine animal in need thereof at a suitable dosis as known to the skilled person and the reduction of BVDV symptoms such as viremia and leukopenia and/or pyrexia and/or diarrhea is monitored. Said treatment preferably may be repeated.
• the following examples serve to further illustrate the present invention; but the same should not be construed as limiting the scope of the invention disclosed herein.
• Example 1 serve to further illustrate the present invention; but the same should not be construed as limiting the scope of the invention disclosed herein.
• MDBK cells were obtained from the American Type Culture Collection (Rockville, Md.). Cells were grown in Dulbecco's modified Eagle's medium supplemented with 10% fetal calf serum (FCS; tested for the absence of pestivirus and antibodies against pestiviruses) and nonessential amino acids.
• FCS fetal calf serum
• Bovine viral diarrhea strain New York '93 field isolate VLS#399 was kindly provided by E. J. Dubovi (New York State College of Veterinary Medicine, Cornell University, ⁇ Ithaca). The virus underwent one animal passage and was termed disregardNew York '93/C" thereafter.
• lysates of infected cells were used for reinfection of culture cells. Lysates were prepared by freezing and thawing cells 3 to 5 days after infection and were stored at -70°C. Unless indicated otherwise in the text, a multiplicity of infection (m.o.i.) of 0,1 was used for infection of culture cells.
• m.o.i. a multiplicity of infection
• the infected cells were fixed with ice- cold acetone:methanol (1 :1 ) for 15 min at -20°C, air dried and rehydrated with phosphate buffered saline (PBS).
• PBS phosphate buffered saline
• RNA hybridization was prepared 48 hours after infection by cesium density gradient centrifugation as described before (R ⁇ menapf et al. 1989). Gel electrophoresis, radioactive labelling of the probe, hybridization, and posthybridization washes were done as described before (R ⁇ menapf et al. 1989).
• a radioactively labelled PCR product (nucleotides 4301 to 5302) from strain New York 93/C was used as a probe.
• PCR was carried out either with Tf/-Polymerase (Promega,
• the primers used for amplification of the 3' end of the genome were upstream, CM46 GCACTGGTGTCACTCTGTTG for the first round and CM80 GAGAAGGCTGAGGGTGATGCTGATG for the nested PCR and downstream, nls- GACTTTCCGCTTCTTTTTAGG.
• Reverse transcription PCR was was done with the TitanTM One Tube RT-PCR System (Boehringer Mannheim, Germany), using 2 ⁇ g of total RNA as a template and following the manufacturer's instructions.
• the primers for amplification of the E ms coding region were upstream, CM28: GGAGAGAATATCACCCAGTG; and downstream, CM21:
• CTCCACTCCGCAGTATGGACTTGC The amplified RT-PCR products were purified by preparative agarose gel electrophoresis and elution with the Nucleotrap kit (Macherey-Nagel, D ⁇ ren, Germany) as recommended by the manufacturer.
• RNA-oligonucleotide nls+: CCTAAAAAGAAGCGGAAAGTC were incubated with 5 units of T4 polynucleotide kinase (New England Biolabs, Schwalbach, Germany) in 30 ⁇ l kinase-mix (2 mM ATP, 50 mM Tris-HCI pH 7.5, 10 mM MgCI 2 , 10 mM dithiothreitol, 25 ⁇ g/ml bovine serum albumin) for 40 min at 37°C.
• the primer was passed through a sephadex G-15 spin column (Sambrook et al. 1989) and further purified by phenol/chloroform extraction and ethanol precipitation. Ligation was carried out using 5 ⁇ g of total RNA prepared from infected culture cells and 150 pmol of the phosphorylated oligonucleotide with 20 units of T4-RNA-Ligase (New England Biolabs, Schwalbach, Germany) in 50 ⁇ l of ligase-mix (50 mM Tris-HCI pH 7.8, 10 mM MgCI 2l 10 mM dithiothreitol, 1 mM ATP, 40% polyethylene glycol and 50 units of RNA guard (Amersham, Freiburg, Germany)) for 16 hours at 17°C. The product was purified by phenol/chloroform extraction and ethanol precipitation.
• Single-stranded (-) DNA from the 5' end of the virus genome was generated with displayThermo-RT reverse transcriptase (Display Systems Biotech, Copenhagen, Denmark) using 2 ⁇ g of total RNA from infected cells and 100 pmol of primer CM79 (see WorcesterPCR and RT-PCR"), and following the manufacturer's instructions (reaction: 65 °C for 10 min; 42°C for 40 min, 65°C for 15 min).
• the DNA was purified by two sequential phenol/chloroform extractions and ethanol precipitations with % vol of 10 M ammonium acetate (Schaefer 1995).
• a poly-dA tail was added to the first cDNA strand with Terminal deoxynucleotidyl Transferase (TdT) (Roche Molecular Biochemicals, Mannheim, Germany) using 50% of the -first strand" product, 50 units terminal transferase, 6,25 ⁇ M dATP and 1 ,5 mM CoCI 2 in 50 ⁇ l of TdT buffer as recommended by the manufacturer. After incubation at 37°C for 30 min, the product was purified by phenol/chloroform extraction and ethanol precipitation.
• TdT Terminal deoxynucleotidyl Transferase
• cDNA library Construction of a cDNA library and nucleotide sequencing. Synthesis of cDNA, cloning and library screening were generally carried out as described previously (Meyers et al. 1991). cDNA synthesis was primed with oligos BVD13, BVD14 and BVD15 (Meyers et al.
• Exonuclease 111 and nuclease S1 were used to establish deletion libraries of cDNA clones (Henikoff 1987). Nucleotide sequencing of double-stranded DNA was carried out with the BigDye Terminator Cycle Sequencing Kit (PE Applied Biosystems, Rothstadt, Germany). As a rule, both DNA strands of the cDNA clones were sequenced; overlaps between independent cDNA clones were sequenced on at least two clones. In total, about 47.000 nucleotides were analyzed which equals an overall coverage of ⁇ 3.8 for the entire genome. Sequence analysis and alignments were done with Genetics Computer Group software (Devereux et al. 1984). s
• cDNA clones from the library were used for construction of the full length cDNA clone: plasmid C3/8 (nucleotides 35 to 2411 ), plasmid C5/11 (nucleotides 22 to 2400) plasmid 8/11 (nucleotides 3400 to 7814), plasmid 13/27 (nucleotides 4783 to 9910) and plasmid C4/24 (nucleotides 8658 to 12322).
• a fragment ..RT-E2" reaching from s nucleotide position 2144 to position 4447 was obtained by RT-PCR with primers CM29 (GATGTAGACACATGCGACAAGAACC) and CM51 (GCTTCCACTCTTATGCCTTG), using total RNA from MDBK cells infected with field isolate VLS#399 as a template.
• CM29 GATGTAGACACATGCGACAAGAACC
• CM51 GCTTCCACTCTTATGCCTTG
• RT-PCR product foulRT-E2 was inserted into the ⁇ /cfel / Hind ⁇ sites of this plasmid after restriction with the same enzymes; the resulting plasmid was pKANE ⁇ . Then, the AatW fragment from clone C5/11 was transferred into the AatW site of pKANE ⁇ , yielding s plasmid pKANEI 4.
• the 5' end of the recombinant cDNA clone was generated by PCR with primers CM87 (GCTCTAGACGGCCGTAATACGACTCACTATAGGTATACGAGATTAGCTAAAGAACT CGTATATGGATTGGACGTCAAC) that introduces a T7 promoter sequence upstream of the first cDNA nucleotide, and CM79 (see purePCR and RT-PCR"); plasmid C5/11 was o used as the PCR template.
• the PCR product was ligated into the Xba ⁇ and BsrG ⁇ sites of cDNA clone C5/9, resulting in plasmid pKANE22.
• oligo CM87 contained a false nucleotide
• pKANE22 was repaired by PCR with oligos CM88 (GACGGCCGTAATACGACTCACTATAGTATACG) and CM79.
• the PCR product was treated with E. coli DNA-Polymerase I (Klenow fragment) to produce blunt ends and then restricted with BsrGI. It was cloned into the Spel blu ⁇ t / BsrGI sites of pKANE22, resulting in plasmid pKANE22A.
• the insert of cDNA clone 8/11 was cut with Xho ⁇ and BamHl and cloned into pACYC177 cut with the same enzymes; the resulting plasmid was named pKANE6.
• the vAvrll / BamHl fragment of cDNA clone 13/27 was transferred to pKANE ⁇ , yielding plasmid pKANE15.
• the EcoRV / Mfe ⁇ fragment from pKANE14 was inserted into pKANE15 digested with the same enzymes.
• the resulting plasmid was pKANE21.
• pKANE21 was digested with Sacll and EcoRV, and a corresponding fragment from pKANE14 was cloned into these sites, leading to plasmid pKANE24. Then the
• Sacll/Sacll fragment from pKANE 22A was cloned into pKANE24 cut with the same enzyme.
• the resulting plasmid was pKANE28AII.
• the 3' end of the genome was generated by PCR with primers B2-11500
• CGGAATTCGCCCGGGCTGTTAGAGGTCTTCCCTAGT which adds an Srf ⁇ site to the 3' end of the genome.
• the PCR product was cut with BamHl and EcoRI and cloned into pACYC177, resulting in plasmid pKANE17. Then, the Sac ⁇ JKpn2 ⁇ fragment of cDNA clone C4/24 was transferred to pKANE17; the plasmid was called pKANE20.
• oligos for mutant H"297"L were CM128 (AACAGGAGTCTATTAGGAATTTGGCCA) and CM129 (TGGCCAAATTCCTAATAGACTCCTGTT). The presence of the desired mutations and the absence of second site mutations were verified by nucleotide sequencing.
• RNA and transfection of MDBK cells were done essentially as described before (Meyers et al. 1996a). Briefly, 2 ug of the respective cDNA construct was linearized with Srfl and purified by phenol extraction and ethanol precipitation.
• T7 RNA polymerase Transcription with T7 RNA polymerase (NEB, Schwalbach, Germany) was carried out in a total volume of 50ul transcription mix (40mM Tris-HCI, pH 7.5; 6mM MgCI 2 ; 2mM spermidine; 10mM NaCI; 0.5 mM of each ATP, GTP, CTP and UTP; 10 mM dithiothreitol; 100ug/ml of bovine serum albumine) with 50 units of T7 RNA polymerase in the presence of 15 units RNAguard (Pharmacia, Freiburg, Germany). After incubation at 37°C for 1h the reaction mixture was passed through a Sephadex G-50 spun column and further purified by phenol extraction and ethanol precipitation.
• 50ul transcription mix 40mM Tris-HCI, pH 7.5; 6mM MgCI 2 ; 2mM spermidine; 10mM NaCI; 0.5 mM of each ATP, GTP, CTP and UTP;
• RNA/DEAE-dextran complex was established by mixing RNA dissolved in 100 ⁇ l HBSS (5 g of Hepes, 8 g of NaCI, 0.37 g of KCI, 0.125 g of Na 2 HP04.2H 2 0 and 1 g of dextrose per Liter; pH 7.05) with 100 ⁇ l DEAE-dextran (1mg/ml in HBSS) and incubation for 30 minutes on ice.
• Pelleted cells were washed once with DMEM without FCS, centrifuged and then resuspended in the RNA DEAE-dextran mixture. After 30 minutes incubation at 37°C, 20 ⁇ l dimethyl sulfoxide was added and the mixture incubated for 2 minutes at room temperature. After addition of 2 ml HBSS, cells were pelleted and washed once with HBSS and once with medium without FCS. Cells were resuspended in DMEM with FCS and seeded in a 10.0-cm-diameter dish. 48h to 72h post transfection cells were split and seeded as appropriate for subsequent analyses.
• Electroporation was used for determination of the specific infectivity of RNA.
• 3x10 6 MDBK cells in 0.5 ml of phosphate buffered saline (PBS) without magnesium and calcium were mixed with appropriate amounts of RNA and transferred into a 2 mm electroporation cuvette. Electroporation was done with one pulse of 960 ⁇ F, 180 Volt in a Hoefer PG 200 Progenetor II. Afterwards, the cells were seeded in 3.5 cm dishes and analyzed by immunofluorescence about 20 h later. Determination of RNAse activity. MDBK cells were infected with the recombinant viruses and grown for 48 hours.
• PBS phosphate buffered saline
• RNAse activity were carried out as described before (Meyers et al. 1999) with the exception that incubation of the probes at 37°C was 30 min instead of
• buffy coats were prepared from all blood samples. 5 ml ice cold lysis buffer were added to an aliquot of heparin stabilized blood (containing ca. 10 7 leucocytes) and incubated on ice for 10 min, followed by centrifugation The pellet was washed once with lysis buffer and twice with PBS without Ca 2+ and Mg + before it was resuspended in 2 ml PBS. MDBK cells seeded in 24-well plates were inoculated with 200 ⁇ l of the buffy coat preparations and incubated for 5 days. Viral antigen was detected by immunofluorescence microscopy with the BVDV E2 mAb mix (see above).
• virus-neutralizing antibodies was tested in serum samples that had been inactivated by incubation at 56°C for 30 min.
• the sera were diluted in steps of 1:2 on 96 well microtitre plates and inoculated with a suspension of strain New York '93/C /100 TCIDso per well) for 1 hour at 37°C. 10 1 75 MDBK cells were added to each well and incubated for 5 days. Infection was analysed by immunofluorescence, calculated by the method of Kaerber (Mayr et al. 1974) and expressed as the 50 % endpoint dilution which neutralized approx. 100 TCID 50 .
• nasal swabs were taken at the time points indicated in the results section, diluted in 2 ml of transport buffer (PBS supplemented with 5 %
• MDBK cells were inoculated in 24 well plates with
• the strain NY'93/C is the second BVDV type 2 genome that has been fully sequenced. Northern blot analysis showed that, contrary to strain 890 (Ridpath and Bolin 1995), the genome of NY'93/C contains no large insertions or deletions (data not shown). Nucleotide sequence analysis revealed that the genome is 12332 nucleotides long and contains one open reading frame encoding a polyprotein of 3913 amino acids.
• the 5' untranslated region (position 1 to 385) was determined by RACE technology and was found to be identical with the New York '93 sequence published by Topliff and Kelling (1998) except for position 21. In contrast to other known type 2 genomes (Ridpath 1995; Topliff and Kelling 1998), strain NY93/C has adenine at this position instead of thymin.
• the full-length clone was constituted from four cDNA plasmids selected from the initial phage library and one RT-PCR product encompassing the region between positions 2265 and 4301. At the 5' end, the sequence of the T7 promoter was added for in vitro transcription, and an Srfl site was added to the 3' end for plasmid linearization (Fig. 1 ).
• the full-length clone was named pKANE40A.
• MDBK cells were transfected with RNA generated from the linearized pKANE40A template by in vitro transcription.
• a runoff transcript from plasmid pKANE28AII which terminates 19 codons upstream of the NS5B coding region served as a negative control.
• Three days post transfection, BVDV-specific signals were detected after immunofluorescence staining in cells transfected with RNA from pKANE40A but not in the control.
• the virus generated from the infectious clone pKANE40A was termed XIKE-A.
• the transfected cells were passaged twice, and the stock of the second passage was used for all further experiments. The virus was analysed by RT-PCR sequencing, taking the nucleotide exchange from C to T at position 1630 as proof of the identity of XIKE-A.
• the specific infectivity of the RNA derived from pKANE40A was determined in comparison to RNA prepared from cells infected with the wild type virus NY'93/C. To this end, the concentration of viral RNA in samples used for transfection of MDBK cells was measured in comparison with defined amounts of the in vitro transcribed RNA after Northern blotting and hybridization, using a phosphoimager. MDBK cells were transfected with similar amounts of both RNAs, and plaques were counted three days post transfection. On the average, the infectivity of RNA derived from pKANE40A was 4.32 x 10 2 pfu/ ⁇ g, and the wild-type RNA yielded 4 x 10 2 pfu/ ⁇ g.
• the growth characteristics of the recombinant virus were analysed through a growth curve, using the original field isolate VLS#399 as a control in the same experiment (Fig. 2).
• MDBK cells were infected with an m.o.i. of 0.1 , and samples were taken at seven time points from 2 hours to 96 hours post infection.
• the growth curve of the recombinant XIKE-A is somewhat smoother than that of VLS#399, but both viruses reach a titre of 10 6,39 after 96 hours. XIKE-A was therefore deemed suitable for further experiments.
• Both mutants were stable in MDBK cells for at least five passages as determined by nucleotide sequencing of RT-PCR products encompassing the E rns coding region.
• the growth characteristics of the two mutant viruses were compared with virus derived from the wild type infectious clone XIKE-A (Fig. 3).
• RNAse activity of XIKE-A, XIKE-B and XIKE-C was determined in crude cell extracts of cells infected with the same m.o.i. of either virus two days post infection.
• RNAse activity was found in the NY'93/C and XIKE-A samples whereas the two mutants XIKE-B and XIKE-C were in the same range as the negative control (Fig. 4).
• the purpose of the first animal experiment was to compare the virulence and pathogenicity of the recombinant virus XIKE-A derived from the infectious cDNA clone with the wild type strain NY'93/C.
• Two groups of three animals (8 to 9 months old) were each infected with 10 5 TClD 50 of either XIKE-A (animals #615, #377, #091) or NY'93/C (animals #275, #612, #1610). Each group was housed in a separate isolation unit. Body temperatures and clinical signs were recorded daily; blood samples were taken on days 0, 2 to 16 and 21 p.i. for leukocyte counts and detection of viremia.
• the identity of the viruses was checked by nucleotide sequencing of RT-PCR products from RNA prepared from buffy coat preparations from all animals. The entire E rns coding region (positions 1140 to 1780) was sequenced and found to be identical with the known sequences of NY'93/C or XIKE-A, respectively. Neutralizing antibodies were found in the serum of all calves starting on day 14 p.i. (Table 2). days p.i. 615 377 091 275 612 1610
• Table 2 Neutralizing antibody titres determined in serum samples of all calves after experimental infection with New York '93/C or XIKE-A. Results are expressed as the reciprocal of the serum BVDV-specific neutralizing antibody titers against New York '93/C (10 2l07 TClD 50 ).
• Leucopenia was found in all animals; however, the decrease of leucocyte numbers was more pronounced in the calves infected with wild type XIKE-A than in the XIKE-B group (Fig. 8).
• Virus was found in buffy coat preparations of all animals starting on day 4 p.i.; however, viremia was shorter for the E rns mutant (0 4 days) than for the virus with wild type sequence (0 8 days). Nasal shedding of virus could be observed for up to 8 days (0 4,7) with XIKE-A animals, but for a maximum of 1 day (0 0,7) with XIKE-B animals (Table 3).
• Table 3 Virus isolation from buffy coat preparations and nasal swabs of animals infected with the recombinant virus XIKE-A (animals #387, #388 and #418) or the E rns mutant XIKE-B (animals #415, #417 and #419). +virus detected, -no virus detected, *anima!s were euthanized on day 12 p.i.
• nucleotide sequencing of RT-PCR products encompassing the entire E rns coding region was used for virus identification in buffy coat preparations.
• isolates from animals #387, #388 and #418 were wild type.
• a deletion of the "H349" codon was confirmed for animals #415, #417 and #419.
• nucleotide position 1246 was changed from guanin to thymin, resulting in the amino acid substitution Q287H.
• Neutralizing antibodies were first detected on day 12 p.i. in the serum of the calves infected with XIKE-A, and on day 14 p.i. in the serum of calves infected with the E r ⁇ s mutant (Table 4).
• Group 1 5 One i. n. administration, XIKE-A 3 ml in each nostril
• Foetal organ samples were collected during routine necropsy and examined for BVDV infection.
• the presence of fetal infection was the main evaluation parameter, composed from the number of BVDV-related cow mortality, the number of BVDV-related abortions and the number of BVD positive fetuses at termination.
• the study aimed to assess the efficacy of BVDV isolates against foetal infection.
• Efficacy of the NY93 infectious copy derivative BVDV recombinant (type II) with a deletion of the Rnase function in the E(RNS) protein XIKE-B (H349 ⁇ ) is investigated to prevent fetal infection after an heterologous type I challenge.
• Heifers were selected from a BVDV negative herd. The heifers were tested serologically and virologically negative for BVDV. The following groups of heifers were included in the trial:
• Group 1 remained untreated in the herd of origin until challenge. Blood samples were collected post-vaccination for buffy coat preparation and serology.
• Inseminations started 4 weeks after immunisation for all groups. Group 1 was transported to the experimental facility before challenge.
• the virus is grown in BVDV free medium as appropriate, aliquoted and frozen at -70 °C [ ⁇ 10 C].
• the vaccination schedule is described in the Experimental Design Section.
• All fetuses from heifers of group 1 were positive for BVDV (all of the following organs were positiv tested for BVDV by virus isolation (mesenteric lymph nodes; small intestine, spleen, thymus, kidney, sternum, bone marrow, cerebellum); the fetuses from from heifers of group 2 were all negative (in all tested organs consistently: mesenteric lymph nodes; small intestine, spleen, thymus, kidney, sternum, bone marrow, cerebellum) for BVDV.
• the XIKE B virus belongs antigenetically to the BVDV type II viruses and is effective in preventing fetal infection after challenge with an heterologous challenge virus belonging to the BVDV type 1 antigenic group.
• Bovine viral diarrhea virus a review. J. Am. Vet. Med.Assoc. 190: 1449-1458.
• BVDV bovine viral diarrhea virus

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  • 2002-09-06 AR ARP020103361A patent/AR036432A1/es unknown
• 2009
  • 2009-08-03 JP JP2009180719A patent/JP2009291203A/ja active Pending

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