Drug – bio-affecting and body treating compositions – Antigen – epitope – or other immunospecific immunoeffector – Virus or component thereof
Reexamination Certificate
2001-02-27
2004-04-20
Salimi, Ali R. (Department: 1648)
Drug, bio-affecting and body treating compositions
Antigen, epitope, or other immunospecific immunoeffector
Virus or component thereof
C424S202100, C424S201100, C424S816000, C435S235100, C435S236000
Reexamination Certificate
active
06723324
ABSTRACT:
The present invention relates to a chicken anaemia virus (CAV), a vaccine comprising a CAV and a method for the preparation of a CAV vaccine.
Chicken anaemia virus (CAV) is the causative agent of a disease known as avian infectious anaemia, anaemia dermatitis syndrome or blue-wing disease and was first described by Yuasa et al. in 1979 (Avian Diseases 23, 366-385, 1979).
Most outbreaks of naturally occurring CAV-induced disease have been reported in young chickens. The disease is acute and the first signs usually occur at 10-14 days of age. This clinical disease is characterised by a sudden increase in mortality, usually around 5-10%, but up to 60% has been reported. Peak mortality occurs within 5 to 6 days of onset of disease. Further clinical signs include depression and anorexia. Moreover, severe anaemia, haemorrhages throughout the body, atrophy of the thymus and bursa of Fabricius and yellowish bone marrow is seen in affected chickens (McNulty, Avian Pathol. 20, 187-203, 1991).
CAV spread both horizontally and vertically in chickens. When in-lay breeders with no previous exposure to the virus become infected, CAV is transmitted vertically to the progeny. No clinical signs are seen in the breeders and there is no apparent effect on egg production, hatchability or fertility. Vertically infected progeny chicks appear normal at hatching but showed increased mortality and develop typical disease (anaemia dermatitis syndrome) from 10 to 14 days of age. Horizontal spread occurs through contact with vertically infected chickens, contaminated fomites, houses, etc. Horizontal spread to young susceptible chickens that means without maternally derived antibodies to CAV may also lead to clinical disease two weeks later.
Ensuring that parent flocks develop antibodies to CAV before onset of lay can control the anaemia dermatitis syndrome. A high level of antibodies against CAV before the onset of lay will prevent vertical transmission during lay and will provide the off spring with maternally derived antibodies, which are protective during the first few weeks after hatching against horizontal infection.
Therefore, it is important that all birds are vaccinated with a CAV vaccine before the onset of lay.
Maternal antibody to CAV has usually disappeared by about 3 weeks of age. By that time horizontal infections can take place. These infections are normally sub-clinical, however this sub-clinical infection is associated with significant economic losses due to reduced growth of the broilers (McNulty et al., Avian Diseases 35, 263-268, 1991). The sub-clinical disease may be prevented by vaccinating the chickens immediately after hatch, preferably at one-day of age.
Clearly, a need exists for a safe vaccine that induces an effective protection against the clinical and sub-clinical disease associated with CAV infections. Because the possibility of spreading of vaccine viruses to susceptible flocks of young chickens exist in practise, live CAV vaccines for parent stock vaccination should be based on CAVs of low pathogenicity. Furthermore, as young chickens are very susceptible to CAV infection, live vaccines for direct administration to young chickens requires the availability of CAV isolates of low pathogenicity which do not adversely affect the young chicks.
However, all naturally occurring CAVs isolated so far are pathogenic for young chicks (McNulty, Avian Pathology 20, 187-203, 1991; Noteborn and Koch, Avian Pathology 24, 11-31, 1995; McNulty, British Poultry Science 38, 7-13, 1997). In addition, the attenuation of CAV isolates by in vitro passages in cell culture has resulted in ambiguous results. Bulow and Fuchs (J. Vet. Med. B 33, 568-573, 1986) reported a decrease of the pathogenicity of the Cux-1 isolate after 12 passages in MDCC-MSB1 cells which was further reduced after an additional 100-112 passages. However, Yuasa (Nat. Inst. Anim. Health Quarterly 23, 13-20, 1983) and Goryo et al. (Avian Pathology 16, 149-163, 1987) found no evidence of attenuation when CAV isolates were subjected to 19 and 40 cell cultures passages, respectively. Todd et al. (Avian Pathology 24, 171-187, 1995) demonstrated attenuation of the Cux-1 isolate by passages (173 times) in MDCC-MSB1 cells, but it was established that this attenuation was not stable and reversion to virulence occurred. European patent application no. 0533294 discloses CAV isolates attenuated by passages in embryonated eggs. These isolates still display some rest-virulence for one-day-old chicks and, hence, are not particularly suited for vaccinating chicks younger than 1 week-of-age. In addition, these attenuated CAV isolates induce lesions in chicken embryos that make these vaccine viruses less suited for in ovo vaccination.
The chicken has been considered as the natural host for CAV. CAV was not found in a survey of UK turkey and duck sera and one-day-old turkey poults inoculated with CAV did not show clinical signs of anaemia and did not develop antibodies to the virus (McNulty et al., Avian Pathology 17, 315-324, 1988 and McNulty, Avian Pathology 20, 187-203, 1991). Only recently Farkas et al. (Avian Pathology 27, 316-320, 1998) reported that CAV antibodies were detected in a species (i.e. quail) other than chicken.
It is an object of the present invention to provide additional CAVs of low pathogenicity which can advantageously be used for the preparation of a live CAV vaccine, e.g. for broiler vaccination.
Another object of the present invention is to provide CAVs of low pathogenicity, in particular non-pathogenic CAVs which can be used for vaccinating birds most susceptible to CAV, e.g. for in ovo vaccination or vaccination of one-day-old birds.
It has now been found that these objects can be met by providing a chicken anaemia virus (CAV), characterised in that the virus is neutralised by a reference sample comprising monoclonal antibody R2 secreted by a hybridoma cell line, a sample of which is deposited at the European Collection of Animal Cell Cultures (ECACC), Salisbury, UK, on Feb. 3, 2000 under accession no. 00020304.
Surprisingly, it has been found that naturally occurring strains of CAV of low pathogenicity exist. The CAVs according to this invention exhibit significantly reduced pathogenicity in one-day-old chickens if compared with naturally occurring CAV strains described so far, as determined by the ability of the virus to induce thymus atrophy, pale bone marrow and/or anaemia (Table 2). Similar unexpectedly, it has been found that these CAVs are isolatable from infected turkeys in the field.
The CAVs according to the invention are antigenically distinguishable from the hitherto known CAV strains isolated from infected chickens as well as from certain other CAV strains isolated from turkeys. Monoclonal antibodies (Moabs) are useful for identifying characteristics of an infectious agent, and for determining antigenic similarities and differences among different isolates of the same or similar micro-organism. In Table 1 it is shown that the CAVs according to the present invention have a reaction pattern with a Moab which is different from that observed with known chicken strains or other turkey strains with a pathogenic character.
In particular it has been found that a CAV strain according to the invention is a virus that is neutralised by a sample comprising Moab R2, in contrast to the known CAV strains isolated from chickens that are not neutralised by this Moab.
To examine whether a CAV strain is neutralised by a sample comprising Moab R2, first the neutralising antibody titre of the Moab R2 sample against the CAV strain 319 deposited at the European Collection of Animal Cell Cultures (ECACC), Salisbury, UK, on Jan. 26, 2000 under accession no. 00012608 must be established in a virus neutralisation test, as described in Example 1 below. Depending on the antibody titre, a Moab R2 reference sample is prepared by either dilution or concentration of the Moab R2 sample so that 50 &mgr;l contains an antibody titre of 16 (log
2
) when examined against 300-1000 TCID
50
per 50 &mgr;l of CAV strain 319 in a virus neutralisatio
Jagt Henricus Johannes Maria
Schrier Carla Christina
Akzo Nobel NV
Ramey III William P.
Salimi Ali R.
LandOfFree
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