Patent Abstract:
the l2 protein of papillomavirus has been cloned as a fusion protein with beta - galactosi - dase and gst ; both as the whole protein and as fragments . vaccination of calves is found to have both a prophylactic effect in tumor prevention and a therapeutic effect in tumor regression .

Detailed Description:
embodiments of the present invention will now be described by way of example only with reference to the following experimental protocol . [ 0016 ] fig1 shows the open reading frames for l2 protein of bpv - 2 ; [ 0017 ] fig2 and 4 show the results of vaccination experiments using l2 protein of bpv - 4 for control group , l2 vaccinated group , and l2 plus e7 vaccinated group respectively . [ 0018 ] fig1 referred to in the experimental protocol shows the l1 and l2 open reading frames ( orf &# 39 ; s ) of bpv2 and the restriction enzyme sites used for cloning . t = tata box ; a = polyadenylation site ; met = translation initiation codon ; taa = translational termination codon ; b = bamhi site ; hp = hpai site ; h = hindiii site . the dna fragment cloned in pur is indicated as l2 ( bamhi - bamhi ). the nucleotide numbering of potter and meinke ( 1985 ) is used . twenty one 12 - week old male friesian calves were obtained from a papilloma - free source . they were randomly assigned to three initial groups , which were housed in separate , clean , well ventilated pens in the isolation unit of the department of veterinary pathology , glasgow . all the calves were bled on arrival for haematological analysis and to obtain pre - inoculation serum samples . the experiment was started when the calves were 16 weeks old . the open reading frame ( orf ) encoding the l2 peptide was isolated by digesting the bpv - 2 genome cloned in pat 153 ( campo and coggins , 1982 ) with bam hi . this produced one fragment of 2030 bp ( nt 268 - 2298 ) numbered according to the nucleotide ( nt ) sequence of potter and meinke ( 1985 ), where nt 1 is the a of the atg codon of the l2 orf ( fig1 ); this fragment contains the majority of the l2 orf ( from aa 90 to aa 467 , l2 ), the l2 orf stop codon and the 5 ′ half of the l1 orf , which would not be expressed because of the termination codon . the fragment was cloned in the pur vector series ( ruther and muller - hill , 1983 ), giving rise to pl2 , and transfected into e . coli jm 109 . peptide for vaccination was prepared from mid - log phase cultures induced for 4 hours in l - broth supplemented with 100 ug / ml ampicillin and containing 1 mm iptg . bacterial pellets resuspended in lysozyme buffer ( 50 mm tris - hc1 ph 8 . 0 , 10 mm mccl 2 , 50 mm glucose , 1 mg / ml lysozyme ) were left at 20 ° c . for 10 min , when edta was added to 50 mm . following cell lysis by the addition of triton x100 to 1 % ( v / v ), the fusion peptide was pelleted at 39000 g for 30 min and resuspended by boiling and sonication in 5 % sds , 50 mm b - mercaptoethanol , 50 mm tris - hcl , ph 8 . 0 purity of 90 - 95 % was achieved by preparative sds page , the final yields being up to 2 mg of product per gm wet weight of cells . the protein was stored at − 20 ° c . before use , but prolonged storage caused degradation . the vaccination experiments were designed as follows : in group a , six animals were vaccinated prophylactically with the gel - purified l2 ( one calf had to be withdrawn from the experiment because of pneumonia ); three of these animals were also vaccinated therapeutically with the gel - purified l2 nine weeks after callenge . in group b , eleven animals received no prophylactic vaccination ; after tumor formation three of these animals were therapeutically vaccinated with gel - purified l2 , while eight animals received no vaccine at all and were therefore used as controls . the calves receiving the l2 vaccine were given a 1 ml pbs suspension containing 650 ug of the l2 fusion protein plus 1 ml of freund &# 39 ; s incomplete adjuvant ( fia ) into the right quadriceps muscle . this was repeated fourteen days later as a boost , but with only 500 g of protein . bpv - 2 was purified from a skin fibropapilloma ( campo et al , 1981 ) and the concentration of viral particles was estimated by the electron microscope assay ( jarrett et al , 1990a ). each calf was challenged at multiple sites with 10 12 virus particles as described by jarrett and other ( 1990a ) either four weeks after vaccination ( two weeks after the boost ) or nine weeks before vaccination . biopsies were performed as described by jarrett et al ( 1990a ). immunocytochemical studies were made by the peroxidase - anti - peroxidase ( hsu et al , 1981 ) or immunogold ( holgate et al , 1983 ) techniques using rabbit anti - bpv - 2 serum as described by jarrett et al ( 1984 ). the presence of neutralizing antibodies in serum samples was determined by the cell transformation inhibition assay described previously ( jarrett et al , 1990a ). this assay takes advantage of the ability of bpv - 2 to transform primary bovine fibroblasts in vitro ( jarrett , 1985b ), which is abrogated by pre - incubation of virus with immune serum . the size of the bpv - 2 b - gal - l2 fusion protein was estimated on page to be 180 kda well in agreement with the predicted size of 156 kda . the l2 fusion protein was characterized immunologically . it was injected into rabbits or calves and the antisera were tested against the fusion protein itself and against virion proteins in both ouchterlony and western blots assays . the antisera were reactive with both the engineered protein ( data not shown ) and its viral l2 ( 62 kda ) counterpart . in reciprocal experiments , rabbit or calf antisera raised against sds - disrupted virus were reactive with the fusion protein . although n - terminus truncated , the fusion protein therefore shares epitopes with virus and presents them effectively to the host immune system . five animals were vaccinated prophylactically ; three of these and three unvaccinated animals were vaccinated therapeutically nine weeks after challenge . as the same results were obtained with the two groups of calves , they will be considered together . all animals developed fibropapillomas four weeks after challenge ( table 1 ). six vaccinated animals were still bearing tumours at ten weeks . in the other two vaccinated calves the tumours were entering the rejection phase : the epithelium was virtually normal and the sub - epithelial tissue was mainly composed of hyalinised collagen . there was a drastic reduction in the number of fibroblasts and a massive infiltration of lymphocytes and macrophages in the sub - epithelial tissue . all vaccinated animals had reached that stage by week thirteen . by week sixteen the tumours had definitely regressed . there were small plaque - like lesions with hyperkeratosis , but virtually all the normal skin adnexal elements were present . some lymphocytes and macrophages were still present . the control animals were still bearing virus - producing tumours ( table 1 ). neutralizing antibodies appeared in the serum of the vaccinated calves at the same time and with the same titre as the control animals ( data not shown ). serum antibodies to l2 were however detected soon after vaccination and before challenge ( data not shown ). vaccination with the l2 fusion protein , whether delivered before or after challenge , induced early tumor regression . tumor regression was accompanied by infiltration of the lesion by macrophages and lymphocytes , a process consistently observed when natural regression takes place ( jarrett , 1985a ). thus it appears that the l2 protein encodes epitopes specific for the cellular effector arm of the immune system . zhou et al ( 1991 ) have recently shown that the l1 protein of hpv - 16 , when expressed in vaccinia virus , induces cytotoxic t - lymphocytes in infected mice , providing another example of t - cell activation by a structural protein . in field and experimental cases , rejection takes place approximately twelve months after infection and it generally follows ulceration of the lesion . this is consistent with the l2 being internal to the virion ( jin et al , 1989 ) and therefore not readily exposed to the host immune system ; ulceration of the tumor with associated bleeding would lead to the exposure of relatively large amounts of antigen to the immune cells . anti l2 antibodies were present in the serum of the vaccinated animals , but these had no activity in the neutralization assay . therefore , unless some neutralizing epitopes are present in the first n - terminus amino acids of l2 , which are missing in our fusion protein , it is unlikely that l2 plays a significant role in conferring prophylactic protection . l2 open reading frame ( orf ) of bpv - 4 was cloned following the general procedure of example 1 , except that plasmid pgex was employed which resulted in a l2 fusion protein with glutathione s - transferase ( gst ) as coprotein . the l2 orf was cloned as the whole orf ( encoding amino acids 8 to 525 ) and as the three fragments encoding amino acids 11 - 201 , 203 - 329 , and 330 - 525 . in the subsequent vaccination experiments a mixture of these four was used . expression was in e . coli and the proteins were purified by gel chromatography , as before . vaccination was carried out as in example 1 using freund &# 39 ; s incomplete adjuvant , except that doses of 1 mg total protein ( l2 and fragments ) was administered both as the dose ( day 0 ) and the booster ( day 28 ). 47 calves , of about 10 weeks of age at the start of the experiment , were housed in an isolation compound . they were divided into 2 groups of 15 and one of 17 ( controls ). all animals were examined and bled before day 0 . they were vaccinated on day 0 and day 28 . they were challenged with bpv - 4 virus on day 43 and examined for tumor formation 4 and 7 weeks later . the results are shown in fig2 ( controls ), fig3 ( l2 alone ) and fig3 ( l2 plus e7 ). the controls showed a good tumor response , 13 of the 17 animals being infected . in the l2 vaccinated group only one animal showed a response ( a small plaque ). in the group vaccinated with l2 plus e7 only one animal developed tumours . thus the l2 protein of bpv - 4 appears to be exerting a strong prophylactic effect in preventing tumor formation ( in contrast to bpv - 2 where a therapeutic effect was exhibited ). campo m s and coggins l w ( 1982 ) molecular cloning of bovine papillomavirus genomes and comparison of their sequence homologies by heteroduplex mapping . journal general virology , 63 , 255 - 264 . campo m s and jarrett w f h ( 1986 ) papillomavirus infection in cattle : viral and chemical cofactors in naturally occurring and experimentally induced tumours . ciba foundation symposium 120 ; 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