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[SANET-MG] field testing a vaccine for dog melanoma cancer
November 21, 2005
Prof. Joe Cummins
Field Testing a DNA Canine Melanoma Cancer Vaccine
The United States Department of Agriculture-Animal and Plant Health
Inspection Service (APHIS) is considering granting authorization to ship
an unlicensed Canine Melanoma Vaccine, DNA, for field testing. Merial,
Inc., Athens, Georgia, has requestedauthorization to conduct clinical
studies that will provide efficacy and safety data in dogsadministered
this vaccine. The efficacy trial will measure the sparing effect of
thevaccine on dogs diagnosed with melanoma. The safety of the vaccine
will be evaluatedin animals participating in the studies. The public may
comment on the environmental assessment APHIS-2005-0104-0001
Availability of an Environmental Assessment for Field Testing Canine
Melanoma Vaccine, DNA 11/15/2005 public comments can be submitted on or
before December 15, 2005. at the web address URL:
The environmental assessment dealt with novel features of DNA vaccines.
However, large sections of the assessment were blacked out as
“confidential business information” (CBI) rendering full evaluation of
the assessment impossible. Frankly, such lavish use of CBI seems to be a
feckless way to avoid criticism of the project other than the comments
made from bureaucrats who have access to the full information.
Nevertheless, the use of DNA vaccines to treat canine melanoma has been
discussed in the literature of science and those studies will be
DNA vaccines are proving effective, normally they are delivered by
intramuscular injection or use of a biolistic device, oral DNA vaccines
are effective in some cases. The vaccines are normally bacterial
plasmids into which are encoded a mammalian promoter such as the
cytomegalovirus promoter driving the protein sequence for an antigen.
The plasmids are taken up by the mammalian cells and reaches the nucleus
of some of those cells. There it is transcribed , translocated to the
cytoplasm, then translated into antigen protein. The bacterial plasmid
sequences are rich in CpG sequences which act as aduvants which enhance
the immune response. The DNA vaccines induce the full spectrum of immune
responses including antibodies, T helper cells and cytotoxic T
lymphocytes(1). Concerns have been expressed about the induction of
autoimmunity and induction of anti-DNA antibodies, and ant-DNA
antibodies were observed in rabbits immunized with plasmids bearing a
HIV reverse trascriptase gene (2). However, DNA antibodies and
autoimmunity have not proven top be major complications of DNA vaccination.
A phase one clinical trial of a DNA vaccine using a plasmid modified
with two peptides from human tyrosinase (tyrosinase is an enzyme that is
on the path to melanin formation which is greatly elevated in melanoma
cancer cells) was undertaken on human subjects with stage IV melanoma
(Patients with stage IV, or metastatic, melanoma have cancer that has
spread from its site of origin to distant lymph nodes and/or distant
sites.). Plasmid DNA was injected into groin lymph nodes. Survival of
treated patients was surprisingly long , with 16 of 24 patients
surviving for after 12 months(3).
Canine malignant melanoma , metastatic form of the disease is common and
resistant to chemotherapy. A clinical study of dogs with malignant
melanoma involved treatment with plasmids containing peptides from human
or mouse tyrosinase. The study showed that the inoculations were safe
and led formation of anti-tyrosinase antibodies (4). Dogs with advanced
malignant melanoma survived for an extended period when inoculated with
a plasmid containing a gene for a peptide from human tyrosinase,
survival extended more than a year . The trial supported use of the
vaccine with dogs and humans with advanced melanoma alike (5).
The report “Nucleic Acid-Mediated (Genetic) Vaccines Risk Analysis for
Melanoma DNA Vaccine (Product Code 9240.D0, Unlicensed)” (reference 6)
indicated that the DNA vaccine was derived from a bacterial plasmid but
all of the pertinent information about the antigen sequence and
antibiotic selection markers was blacked out presumably deemed
confidential business information (CBI) in an astonishingly ill informed
manner. The only information about the plasmid allowed (not blacked out)
was that it was an E coli plasmid.
Among the issues considered in the review was the chance that the
vaccine antigen would recombine with genes in the dog chromosomes
causing mutations. No effort was made to measure gene integration form
the vaccine antigen , the proponents and APHIS argued that the chance of
integration was low based on studies of antigen integration from the
malaria parasite (7) or from influenza virus or HIV virus (8). It is
worth pointing out that the dog melanoma vaccines have all been based on
genes present in the mammalian genomes with high levels of DNA homology
allowing legitimate recombination at a much higher frequency than the
antigen genes from parasites or viruses that have little or no homology
with the mammalian genome and must recombine using illegitimate
recombination, It is surprising that APHIS and the proponent failed to
mention that important point.
The proponent and APHIS argue that immuno-modulator sequences such as
the CpG motif are not known to be present in something blacked out
related to the plasmid vaccine DNA. This point is clearly in error for
the CpG motif is present in the E. coli plasmids and that is certainly
active in dogs and cats (9).
The problem of auto-immunity and anti-DNA antibodies was dealt with in a
cursory manner. The handling and escape of plasmid bearing bacteria was
discussed in a cursory manner and no data was provided to support
conclusions. The dissemination of the vaccine plasmid in the environment
was also considered without experimental data. Conclusion that the
plasmid ingested by animals would be of no consequence did not provide
data support that conclusion. Horizontal gene transfer was discounted
without supporting data.
The proposal by the proponent and APHIS claims that here is little or no
chance of having problems related to accidental spills of solutions
containing plasmid. Because the plasmid is not infectious and is
unstable in the environment. However no data were supplied to support
that conclusion. The report maintains that plasmid shed or released from
test animals posed no concern because the levels of plasmid released by
those animals would be low. Even though data was not provided to support
that conclusion there was no indication that feces , urine or vomited
materials would be handled in any special way to prevent dispersal of
the plasmid in the environment. The antibiotic resistance markers
associated with the plasmid were designated CBI , thus information on
them is unavailable to any bystander exposed to the plasmid from surface
or groundwater, in air associated with dust particles or in bacteria.
Many bacteria are capable of taking up DNA molecules and integrating
them into the bacterial chromosome , such as Acinobacter and a wide
array of gram positive bacteria.
In conclusion, the proposal for a field trial of a DNA vaccine to treat
canine had serious defects that make the project appear to be
threatening rather than beneficial. Using CBI to hide the most
elementary aspects of the proposal seemed to hide serious defects in the
experiment as did the failure to provide supporting date to support far
reaching conclusions. The proposal seems to cry out there must be
collusion between APHIS and the vaccine promoters to provide fast and
dirty remedies for important problems. The proponents should have
provided a full and truthful report , without the feckless, even, silly
CBI designations of fundamental information. Such proposals make it
appear that bureaucrats and corporations connive to exclude the public
from deliberations on biotechnology. This unfortunate turn of events has
transpired because the public has allowed secretive field tests of
dangerous genetic constructions which allows the proponents for such
tests to evade being implicated in the injury from such tests. Now,
bureaucrats serve private interests and participate in withholding
fundamental information designated CBI . The practice prostitutes the
primary scientific dictum that the results of experiments must be
reported fully and truthfully.
1Kowalczyk,D. and Ertl,H. Immune response to DNA vaccines CMLS Cell.
Mol. Life Sci. 1999 , 55, 751-70
2.Isaguliants MG, Iakimtchouk K, Petrakova NV, Yermalovich MA, Zuber AK,
Kashuba VI, Belikov SV, Andersson S, Kochetkov SN, Klinman DM and Wahren
B. Gene immunization may induce secondary antibodies reacting with DNA.
Vaccine. 2004 Mar 29;22(11-12):1576-85.
3. Tagawa ST, Lee P, Snively J, Boswell W, Ounpraseuth S, Lee S,
Hickingbottom B, Smith J, Johnson D and Weber JS. Phase I study of
intranodal delivery of a plasmid DNA vaccine for patients with Stage IV
melanoma Cancer. 2003 Jul 1;98(1):144-54.
4. Bergman PJ, Camps-Palau MA, McKnight JA, Leibman NF, Craft DM, Leung
C, Liao J, Riviere I, Sadelain M, Hohenhaus AE, Gregor P, Houghton AN,
Perales MA and Wolchok JD. Development of a xenogeneic DNA vaccine
program for canine malignant melanoma at the Animal Medical Center.
Vaccine. 2005 Sep 23; [Epub ahead of print]
5. Bergman PJ, McKnight J, Novosad A, Charney S, Farrelly J, Craft D,
Wulderk M, Jeffers Y, Sadelain M, Hohenhaus AE, Segal N, Gregor P,
Engelhorn M, Riviere I, Houghton AN and Wolchok JD. Long-term survival
of dogs with advanced malignant melanoma after DNA vaccination with
xenogeneic human tyrosinase: a phase I trial. Clin Cancer Res. 2003
6. Merial, Inc. Environmental Assessment for Field Testing Canine
Melanoma Vaccine, DNA 2005 Nucleic Acid-Mediated (Genetic) Vaccines Risk
Analysis for Melanoma DNA Vaccine (Product Code 9240.D0, Unlicensed)”
7. Martin T, Parker SE, Hedstrom R, Le T, Hoffman SL, Norman J, Hobart P
and Lew D. Plasmid DNA malaria vaccine: the potential for genomic
integration after intramuscular injection. Hum Gene Ther. 1999 Mar
8. Ledwith BJ, Manam S, Troilo PJ, Barnum AB, Pauley CJ, Griffiths TG
2nd, Harper LB, Beare CM, Bagdon WJ and Nichols WW. Plasmid DNA
Vaccines: Investigation of Integration into Host Cellular DNA following
Intramuscular Injection in Mice Intervirology. 2000;43(4-6):258-72
9. Krieg A. CpG Motifs in bacterial DNA and their immune effect Annu,
Rev. Immunol. 2002 ,20,709-60
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